feat(work): add Reverse Linked List solution

feat(api): add /admin/solved endpoint and commit source handling

.claude/skills/campaign-issues/SKILL.md

@@ -0,0 +1,175 @@
+---
+name: campaign-issues
+description: Create GitHub issues for this LeetCode campaign — individual problem issues and the topic issues that own them — using the repo's exact title, label, milestone, body, and sub-issue conventions. Use when asked to add/create an issue for a LeetCode problem or a topic, attach a problem to its topic, or backfill the issue catalog.
+---
+
+# Campaign issues
+
+The GitHub issue tracker **is the campaign catalog**: ~24 `topic` issues each own a
+set of `problem` sub-issues. The Worker reconciles this catalog into D1 nightly
+(`/admin/reconcile`), so a correctly-labelled issue is all that's needed — the SRS,
+digest, charts, and Project mirror pick it up automatically. Get the labels/body shape
+right; everything downstream is reconciliation.
+
+All commands use `gh` against `prdlk/leetcode` and fall back to `gh auth token`.
+
+## Problem issue
+
+One issue per LeetCode problem, attached as a sub-issue of its topic.
+
+- **Title:** `LC <num> · <Title>` — the LC number and the problem's name, nothing
+  else. Separator is a middle dot `·` (U+00B7) with single spaces. Difficulty and
+  set are **labels only**; never repeat them in the title (they used to be a `·
+  Hard · core` suffix — that is gone, and `catalog.ts` no longer parses it).
+- **Labels** (four, all required — these are what the Worker reads):
+  - `problem` — marks the sub-issue as curriculum; without it the reconcile skips it.
+  - `diff:easy` | `diff:medium` | `diff:hard` — LeetCode's own rating, do not invent.
+  - `set:core` | `set:optional` | `set:deferred` — see set semantics below.
+  - `phase:N` — the **topic's** phase (same phase label the topic issue carries).
+- **Milestone:**
+  - `core` / `optional` → the topic's phase milestone.
+  - `deferred` → `Review — Transfer & Mocks` (deferred Hards are parked until week 8).
+  - Pass the milestone **title**, not its number, to `--milestone`.
+- **Body** (exact shape; `<slug>` is the LeetCode URL slug, `<topic-issue>` the owning topic's number):
+
+  ```
+  https://leetcode.com/problems/<slug>/
+
+  - **Topic:** #<topic-issue>
+  - **Set:** <core|optional|deferred>
+  - **Language:** Python
+
+  ### Close-out (paste before closing this issue)
+  - Time: O(?)
+  - Space: O(?)
+  - Edge case traced:
+  - First attempt passed: yes / no
+  - Miss note:
+  ```
+
+Create it:
+
+```sh
+gh issue create --repo prdlk/leetcode \
+  --title "LC 42 · Trapping Rain Water" \
+  --label problem --label set:core --label diff:hard --label phase:1 \
+  --milestone "Phase I — Linear Structures" \
+  --body "https://leetcode.com/problems/trapping-rain-water/
+
+- **Topic:** #9
+- **Set:** core
+- **Language:** Python
+
+### Close-out (paste before closing this issue)
+- Time: O(?)
+- Space: O(?)
+- Edge case traced:
+- First attempt passed: yes / no
+- Miss note:"
+```
+
+Then **attach it as a sub-issue of the topic** (this is a separate API call — creating
+the issue does not link it). The sub-issues API wants the child's internal **id**, not
+its issue number, and the field is integer-typed, so use `-F` (not `-f`):
+
+```sh
+child_id=$(gh api repos/prdlk/leetcode/issues/211 --jq '.id')
+gh api --method POST repos/prdlk/leetcode/issues/9/sub_issues -F sub_issue_id=$child_id
+# verify
+gh api repos/prdlk/leetcode/issues/9/sub_issues --jq '.[] | "\(.number)  \(.title)"'
+```
+
+## Topic issue
+
+One issue per curriculum topic; owns the problem sub-issues.
+
+- **Title:** `Topic NN — <Name>` (zero-padded number, em dash, e.g. `Topic 07 — Monotonic Stack`).
+- **Labels:** `topic`, `phase:N`.
+- **Milestone:** that phase's milestone (title, not number).
+- **Body:**
+
+  ```
+  **Scheduled:** <Weekday Mon DD, YYYY>
+  **Phase:** <Roman> — <Phase name> (Week N)
+  **Builds on:** Topic <n>
+
+  ### Trigger
+  TODO
+
+  ### Invariant
+  TODO
+
+  ### Trap
+  TODO
+
+  ### Close-out ritual
+  Before every submit, out loud:
+  1. State time and space complexity.
+  2. Trace one edge case.
+
+  ### Day rules
+  - 90-minute coding cap. Stop at the cap, even mid-problem.
+  - Core problems first. Optional only if the core is done.
+  - Finished early? Do this topic's optional set. Do not start tomorrow.
+  ```
+
+`Scheduled` should come from the calendar of record — `apps/api/data/schedule.json`
+(day → topic issue) — not guessed.
+
+## Reference tables
+
+Set semantics (from the label descriptions):
+
+| set | meaning | milestone |
+|---|---|---|
+| `core` | must solve on the topic day | topic's phase milestone |
+| `optional` | solve only if the clock allows | topic's phase milestone |
+| `deferred` | a Hard, parked until week 8 | `Review — Transfer & Mocks` |
+
+Milestones (`--milestone` takes the **title**):
+
+| # | title |
+|---|---|
+| 1 | Phase I — Linear Structures |
+| 2 | Phase II — Nodal & Grid |
+| 3 | Phase III — Hierarchical |
+| 4 | Phase IV — Relational |
+| 5 | Phase V — Decision Space |
+| 6 | Review — Transfer & Mocks |
+
+Find a topic issue and confirm its phase before creating problems under it:
+
+```sh
+gh issue list --repo prdlk/leetcode --label topic --state all --limit 30 \
+  --json number,title,labels,milestone
+```
+
+## Gotchas
+
+- **Check the LC number is not already in the curriculum BEFORE creating.** D1 keys
+  `problems` on `lc_number` (`ON CONFLICT(lc_number)`), so two issues for one LC number
+  silently fight over a single row — whichever the reconcile walks last wins, and the
+  loser's issue number ends up orphaned in D1. A problem can legitimately move topic or
+  set; that is a relabel/re-parent of the *existing* issue, never a second issue:
+
+  ```sh
+  gh issue list --repo prdlk/leetcode --label problem --state all --limit 300 \
+    --search "LC 42" --json number,title,labels,state
+  ```
+
+  If a row already exists, change the existing issue instead: swap its `set:*` label,
+  move the sub-issue to the new topic, and fix its milestone. Then reconcile the board
+  (`project-fields` skill). If a duplicate did get created and one is deleted, the
+  surviving issue number and set only reach D1 on the next catalog reconcile — SRS
+  columns (`stage`, `next_review`) are preserved, since they are the real attempt history.
+
+- **`-F` vs `-f`:** `sub_issue_id` must be an integer; `-f` sends a string and the API
+  rejects it with `is not of type integer`.
+- **id, not number:** the sub-issue payload wants the child's `.id` (a large opaque
+  integer), never its display `#number`.
+- **`--milestone` wants the title string**, not the numeric id (`'1' not found` otherwise).
+- **Reconcile, don't react:** don't edit D1 or the Project by hand — a correct issue is
+  reconciled into SRS state on the nightly cron. Solutions landing in `work/` are what
+  close problem issues (via `close-solved.yml`), which then roll up to close topics.
+- **Difficulty is LeetCode's**, `set` is our scheduling choice — they're independent. A
+  Hard can be `core` if we deliberately schedule it (vs the usual `deferred`).

.claude/skills/project-fields/SKILL.md

@@ -0,0 +1,108 @@
+---
+name: project-fields
+description: Reconcile the "Interview Prep" GitHub Project (user project #2) fields — Set and Difficulty projected from issue labels — and understand which fields the Worker mirrors vs which live only in D1. Use when asked to sync/fix/backfill Project fields, when Project columns look empty or stale, or when adding a field to the project.
+---
+
+# Interview Prep Project fields
+
+The user-level Project **"Interview Prep"** (`prdlk` project #2, id `PVT_kwHOADoNjs4BhV1a`)
+is a *board over* the issue catalog, never a source of truth. Every field is a projection
+of something owned elsewhere.
+
+## Field ownership — the rule that matters
+
+| Field | Owner | Written by |
+|---|---|---|
+| `Set` (Core/Optional/Deferred) | issue label `set:*` | `sync-project-fields`, last step of `close-solved.yml` |
+| `Difficulty` (Easy/Medium/Hard) | issue label `diff:*` | `sync-project-fields`, last step of `close-solved.yml` |
+| `Target Date` | D1 `next_review` | Worker mirror, per log (`apps/api/src/mirror.ts`) |
+| `Status`, `Labels`, `Milestone`, `Parent issue`, … | GitHub built-ins | GitHub |
+
+**SRS stage and first-attempt result are deliberately NOT Project fields.** They live only
+in D1; the charts, digest and `/api/stats` read them from there. Duplicating them into
+Project single-selects bought nothing but drift and two extra writes per log. Do not re-add
+them to the project, and do not re-add `setStage`/`setFirstAttempt` to `mirror.ts`.
+
+## Reconciling Set / Difficulty
+
+`apps/cli/sync-project-fields.ts` recomputes every desired value from the issue labels and
+writes only what differs — same reconcile-don't-react shape as `close-solved`.
+
+**In CI it runs itself.** It is the final step of `.github/workflows/close-solved.yml`, so
+any push under `work/` reconciles the board along with the issues and D1. The step is
+`continue-on-error: true` and skips cleanly when `PROJECT_PAT` is unset — D1 and the issues
+are the truth, so a Project failure must never fail a run that already closed issues and
+logged the solve. It honours the workflow's `dry_run` input via `DRY_RUN=true`.
+
+Run it by hand when issues changed without a `work/` push (e.g. you just filed a problem
+issue, or relabelled one):
+
+```sh
+# needs a token with the `project` scope — neither `gh auth token` nor GITHUB_TOKEN has it.
+export GH_TOKEN=$(grep '^GH_PAT=' apps/api/.dev.vars | cut -d= -f2-)
+
+bun run sync-project-fields -- --dry-run   # or DRY_RUN=1|true; prints the table, writes nothing
+bun run sync-project-fields                # apply
+bun run sync-project-fields                # re-run: must report 0 writes
+```
+
+Invariants the script holds — preserve them in any edit:
+
+- **Only `problem`-labelled items are touched.** Topic, cadence and review issues have no
+  set/difficulty; they are skipped, never written and never cleared.
+- **Idempotent.** A second run reports `0 field value(s)`. That re-run *is* the verification.
+- **Labels are truth.** Never "fix" a field by hand in the UI — fix the label, then reconcile.
+  A hand-edited field is silently reverted on the next run.
+- **Fields and options resolve by NAME**, so re-creating a field in the UI doesn't strand a
+  dead id. A missing field or option is a hard error, not a silent skip.
+- **A problem missing a `set:`/`diff:` label** warns and is left untouched (it means the
+  issue is mislabelled — fix it with the `campaign-issues` skill).
+
+## Auth gotcha
+
+Project v2 needs the `project` scope. The local `gh` login has only
+`gist, read:org, repo, workflow`, so **any** `gh project`/GraphQL project call fails with
+the default token. Use the Worker's `GH_PAT` from `apps/api/.dev.vars` via `GH_TOKEN`
+(never echo it). Symptom of the wrong token: `Resource not accessible by personal access
+token` or an empty `projectsV2.nodes`.
+
+## Inspecting the project
+
+```sh
+export GH_TOKEN=$(grep '^GH_PAT=' apps/api/.dev.vars | cut -d= -f2-)
+
+# fields + single-select options
+gh api graphql -f owner=prdlk -f title="Interview Prep" -f query='
+query($owner: String!, $title: String!) {
+  user(login: $owner) { projectsV2(first: 10, query: $title) { nodes { id title number
+    items(first: 1) { totalCount }
+    fields(first: 30) { nodes {
+      ... on ProjectV2FieldCommon { id name dataType }
+      ... on ProjectV2SingleSelectField { options { id name } } } } } } }
+}' --jq '.data.user.projectsV2.nodes[] | select(.title=="Interview Prep")
+         | .fields.nodes[] | "\(.name)\t\(.dataType)\t\((.options // []) | map(.name) | join(","))"'
+```
+
+Writes use `updateProjectV2ItemFieldValue` with
+`value: { singleSelectOptionId: … }` (dates use `{ date: "YYYY-MM-DD" }`); clearing uses
+`clearProjectV2ItemFieldValue`. An item id is *not* an issue number — resolve it from the
+project's `items` connection (or the issue's `projectItems`), as `mirror.ts` does.
+
+## Adding a new projected field
+
+1. Create the field + options in the Project UI.
+2. Add it to the `FIELDS` table in `apps/cli/sync-project-fields.ts` — one entry mapping
+   label → option name. Nothing else needs to change; resolution, diffing, dry-run and
+   reporting are generic over that table.
+3. Dry-run, apply, re-run to prove idempotency.
+
+If the new field's truth lives in **D1** rather than a label, it belongs in the Worker
+mirror instead (`apps/api/src/mirror.ts`) — but read the ownership rule above first and
+default to *not* mirroring.
+
+## Known trap
+
+`resolve()` in `mirror.ts` throws if a field it asks for is absent, *before* caching
+`info` — so one missing field breaks **every** mirrored write, including `Target Date`,
+and only as a `console.warn`. If Target Date silently stops updating, check that every
+field `resolve()` looks up still exists in the project.

.github/workflows/close-solved.yml

@@ -28,7 +28,36 @@ jobs:
       - uses: oven-sh/setup-bun@v2
 
       # No install step: the script only uses Bun builtins + fetch.
+      #
+      # SRS_ADMIN_KEY lets the script report the solved set to the Worker
+      # (POST /admin/solved). Closing an issue is invisible to D1 — the
+      # catalog reconcile never reads issue state, and only logAttempt() moves
+      # the ladder — so without this a pushed solution would never reach the
+      # charts, the digest's solved ticks, or the drill/gate pools.
       - run: bun apps/cli/close-solved.ts
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           DRY_RUN: ${{ inputs.dry_run }}
+          SRS_ADMIN_KEY: ${{ secrets.SRS_ADMIN_KEY }}
+
+      # Project fields are a projection of the issue labels, so the same push
+      # that adds a solution (and any issue filed since the last run) can leave
+      # the board's Set/Difficulty empty. Reconciling here keeps the one
+      # "solution landed" entry point responsible for the whole fan-out; the
+      # script is idempotent, so a run with nothing to do writes nothing.
+      #
+      # Needs the `project` scope, which GITHUB_TOKEN does not have — hence
+      # PROJECT_PAT. Unset = skip, matching SRS_ADMIN_KEY above. Best-effort by
+      # design: D1 and the issues are the truth, so a Project failure must not
+      # fail a run that already closed issues and logged the solve.
+      - name: Reconcile Project Set/Difficulty
+        continue-on-error: true
+        env:
+          GH_TOKEN: ${{ secrets.PROJECT_PAT }}
+          DRY_RUN: ${{ inputs.dry_run }}
+        run: |
+          if [ -z "$GH_TOKEN" ]; then
+            echo "PROJECT_PAT unset — skipping the Project field reconcile"
+            exit 0
+          fi
+          bun apps/cli/sync-project-fields.ts

.github/workflows/close-topics.yml

@@ -1,5 +1,10 @@
 name: Close Topics
 
+# No D1 push here, unlike Close Solved: D1 stores no topic completion column.
+# Phase progress, the gate pools and the charts all derive from the problem
+# rows, which close-solved already logs — a topic is finished exactly when its
+# core problems are, so there is nothing left to reconcile.
+
 on:
   # Close Solved closes problem issues with GITHUB_TOKEN, and token-driven
   # closes never fire `issues` events — so chain off its run instead.

.github/workflows/spaced-repetition.yml

@@ -0,0 +1,54 @@
+name: Spaced Repetition
+
+# Opens (or refreshes) today's `Spaced Repetition — <Month D, YYYY>` issue from
+# whatever the SRS ladder has due (`POST /admin/due`, the same rows the 8 AM
+# digest mails — so the two cannot disagree). The script stores nothing and
+# schedules nothing: it asks D1 what is standing today, keyed by the ET date in
+# the title, so a re-run rewrites one body instead of stacking duplicates.
+# Sunday is the rest day and the ladder never books it, so nothing is written.
+
+on:
+  schedule:
+    # 10:00 UTC = 06:00 ET while the campaign runs (EDT through Nov 1), 05:00 ET
+    # after. No DST guard and no second cron: the issue is keyed by ET calendar
+    # date, not by the hour it was created, so the drift is cosmetic.
+    - cron: "0 10 * * *"
+  workflow_dispatch:
+    inputs:
+      dry_run:
+        description: Print the issue body without creating or updating anything
+        type: boolean
+        default: false
+      date:
+        description: ET date to treat as today (YYYY-MM-DD) — backfill a missed day
+        type: string
+        default: ""
+
+permissions:
+  contents: read
+  issues: write
+
+concurrency:
+  group: spaced-repetition
+  cancel-in-progress: false
+
+jobs:
+  drill:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: oven-sh/setup-bun@v2
+
+      # No install step: the script only uses Bun builtins + fetch.
+      #
+      # SRS_ADMIN_KEY reads today's due list from the Worker. Unset is fatal
+      # here, unlike in close-solved: without D1 there is no schedule to render,
+      # and inventing one from issue close dates is exactly the second source of
+      # truth this replaced.
+      - run: bun apps/cli/spaced-repetition.ts
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          DRY_RUN: ${{ inputs.dry_run }}
+          SRS_TODAY: ${{ inputs.date }}
+          SRS_ADMIN_KEY: ${{ secrets.SRS_ADMIN_KEY }}

.gitignore

@@ -1,6 +1,8 @@
 # dependencies (bun install)
 node_modules
 tmp/
+*.log
+.crush
 
 # output
 out

AGENTS.md

@@ -2,7 +2,7 @@
 
 ## Project Overview
 
-LeetCode interview-prep campaign (8 weeks, 2026-08-17 → Oct 11) run as a repo: solution files under `work/`, a Blume docs site under `apps/docs/`, GitHub Actions that reconcile issues and publish docs, and a Cloudflare Worker (`apps/api/`) that runs the spaced-repetition system (SRS) — daily digest email, one-tap logging, weekly review issues, live charts. Issues model the curriculum: ~24 `topic` issues own ~161 `problem` sub-issues (`set:core|optional|deferred`, `diff:*`); milestones are phases; a user-level GitHub Project ("Interview Prep", #2) mirrors review state.
+LeetCode interview-prep campaign (8 weeks, 2026-08-17 → Oct 11) run as a repo: solution files under `work/`, a Blume docs site under `apps/docs/`, GitHub Actions that reconcile issues and publish docs, and a Cloudflare Worker (`apps/api/`) that runs the spaced-repetition system (SRS) — daily digest email, one-tap logging, weekly review issues, live charts. Issues model the curriculum: ~24 `topic` issues (`Topic NN — Name`) own ~161 `problem` sub-issues titled `LC <num> · <Name>`, with difficulty and set carried **only** by labels (`set:core|optional|deferred`, `diff:*`) — never by the title; milestones are phases; a user-level GitHub Project ("Interview Prep", #2) mirrors review state.
 
 ## Architecture & Data Flow
 
@@ -12,18 +12,26 @@ Three owners, one direction of truth:
 flowchart LR
   work[work/ solutions] -->|bun run sync| docs[apps/docs/content/*.mdx]
   work -->|close-solved.yml| PI[problem issues]
+  work -->|close-solved.yml POST /admin/solved| D1[(D1 = SRS state)]
   PI -->|close-topics.yml| TI[topic issues]
-  GH[GitHub issues = catalog] -->|nightly reconcile| D1[(D1 = SRS state)]
+  GH[GitHub issues = catalog] -->|nightly reconcile| D1
   D1 -->|8 AM ET cron| Mail[digest email + one-tap links]
   Mail -->|GET /log| D1
   PI -->|/done webhook| D1
-  D1 -->|best-effort mirror| Proj[GitHub Project fields]
+  D1 -->|best-effort mirror: Target Date only| Proj[GitHub Project fields]
+  GH -->|close-solved.yml sync-project-fields| Proj
   D1 -->|Sat midnight ET| Review[Review — Week N issue]
+  PI -->|"spaced-repetition.yml (6 AM ET cron, closed +3d/+7d)"| SR[Spaced Repetition — Month D issue]
   D1 --> Charts[SVG charts + /api/stats]
 ```
 
-- **Reconcile, don't react.** `close-solved.ts`, `close-topics.ts`, and the Worker's catalog sync recompute desired state from scratch each run: re-runs are no-ops, backfills need no special casing, closing is one-directional.
+- **Reconcile, don't react.** `close-solved.ts`, `close-topics.ts`, and the Worker's catalog sync recompute desired state from scratch each run: re-runs are no-ops, backfills need no special casing, closing is one-directional. `close-solved` posts its *whole* implemented set to `/admin/solved`, not just the issues it closed this run.
-- **D1 owns SRS state; GitHub issues own the catalog; `apps/api/data/schedule.json` owns the calendar.** The catalog reconcile never invents rows and never overwrites SRS columns (`stage`, `next_review`). Project fields (`Target Date`, `SRS Stage`, `First Attempt`) are a best-effort mirror (`apps/api/src/mirror.ts`): failures are warnings, never lost D1 writes; topic rows' `Target Date` is never written.
+- **Solving has three doors, one write path.** A digest one-tap, a `/done` comment, and a solution landing in `work/` all end in `logAttempt()`. Closing an issue is *not* one of them: the catalog reconcile never reads issue state, so a `work/` push that skipped the email would otherwise leave `stage='new'` — invisible to the charts, the digest's solved ticks, and the drill/gate pools. Hence `/admin/solved`, which takes `{lc, bucket}` pairs (`source='commit'`): the bucket names the rung the file settles — `work/1` settles `new`, `work/3` settles `+3`, `work/7` settles `+7` — so a pushed re-solve advances the ladder instead of vanishing, and re-posting the whole implemented set writes nothing because the rung named has already been left behind. That stage check is the entire idempotency mechanism; no index, no dedupe table, no state file. `close-topics` needs no such call — D1 stores no topic completion, only problem rows.
+- **The rest day is structural, not cosmetic.** Sunday is never booked: topics run Mon–Fri (`apps/api/data/schedule.json`), the gate is Saturday, and the ladder's windows are 3 and 7 precisely because those return a solve to a working day. Every scheduled date — ladder review, levelled overflow, deferred-Hard release, review-issue window — comes out of `workingDay()` in `apps/api/src/srs.ts`, which slides the one exception (a Thursday solve's `+3`) forward to Monday. Forward, never back: a review may slip later than its interval, never shorten it. Never mint a scheduled date with bare `addDays()`, and never "fix" a Sunday landing downstream — the digest's Sunday rest branch is a courtesy, not the mechanism. `apps/api/src/srs.test.ts` sweeps the campaign calendar to keep this honest.
+- **One schedule, one answer to "what is open today".** D1's ladder IS the schedule; `dueToday()` (`POST /admin/due`) is its read side and `DUE_WHERE` is the single SQL definition of "due", shared by the digest, the review issue and the docs queue chart. `spaced-repetition.yml` renders that answer into today's `Spaced Repetition — <Month D, YYYY>` issue — grouped by rung, `WINDOW_CAP` (3) required per rung with the overflow listed as optional, keyed by the ET date in the title so a re-run rewrites one body. It schedules nothing, stores nothing, and writes nothing on Sunday. Without `SRS_ADMIN_KEY` it FAILS rather than inventing a second schedule from issue close dates — that reconstruction was the drift, and it is gone. NEVER add a JSON state file (`.github/problems.json` and friends) or a second "when is this due" rule: D1 answers it, with one writer (`logAttempt`) and git-free history in `attempts`.
+- **The picker owns the local review loop; the buckets are its state.** `work/` holds three buckets (`1` = first solve, `3`/`7` = blind re-solves, named after the ladder rungs) and `bun run pick` has three sections — Tab cycles them. Pools are reconciled from the filesystem plus one `git log` (`apps/cli/work.ts`): a first solve dates from the ET date of the commit that added its `work/1` file — the same push that closes the problem issue and starts the +3/+7 windows — and a window stops being owed the moment its bucket holds a file. Uncapped, unlike the review issue's `WINDOW_CAP`: that issue is one day's assignment, the picker is everything still owed. An empty scaffold under `work/1` owes nothing (it is unsolved), which is why `isImplemented()` lives in `apps/cli/source.ts` and is shared with `close-solved.ts`. leetcode-cli reads its output directory from `~/.leetcode/workspaces/<active>/config.json` and nowhere else — no flag, no env var — so `pick.ts` MERGES `workDir` into that file around the child (never replays saved bytes: the CLI owns the file too) and leaves it pointed at `work/1`, then treats the scaffold's existence as the acceptance test, since leetcode-cli exits 0 even when an expired session made it write nothing. The picker itself writes no state: pushing the re-solve is what moves the ladder, via `close-solved` → `/admin/solved` with that file's bucket.
+- **The README charts are live, never committed.** They are Worker endpoints reading D1 per request (`Cache-Control: max-age=300`, honored by GitHub Camo), so a solved push moves them within ~5 minutes with no commit and no workflow of their own.
+- **D1 owns SRS state; GitHub issues own the catalog; `apps/api/data/schedule.json` owns the calendar.** The catalog reconcile never invents rows and never overwrites SRS columns (`stage`, `next_review`). `Target Date` is the *only* Project field the Worker mirrors (`apps/api/src/mirror.ts`): failures are warnings, never lost D1 writes; topic rows' `Target Date` is never written. SRS stage and first-attempt result live **only** in D1 — do not re-add them as Project fields. The Project's `Set`/`Difficulty` single-selects are a projection of the issue labels, reconciled by `bun run sync-project-fields` — a best-effort final step of `close-solved.yml`, never the Worker.
 - **Determinism = idempotency.** Drill/gate sampling uses a seeded PRNG (`rng()` in `apps/api/src/srs.ts`, FNV-1a → mulberry32, seed = date / ISO week); the digest is keyed by ET date in `email_log`; one-tap links are unique on (problem, date, kind).
 - **DST-proof crons:** each event has two UTC crons; code fires only on the computed ET hour (`etHour`), unit-checked in `apps/api/src/srs.test.ts`.
 - **Chained workflows:** `GITHUB_TOKEN`-driven issue closes fire no `issues` events, so `close-topics.yml` chains off `workflow_run` of Close Solved instead. The Worker's webhook uses its own `GH_PAT`, so its events flow normally.
@@ -32,24 +40,41 @@ flowchart LR
 
 | Path | Purpose |
 |---|---|
-| `work/<Difficulty>/<Category>/<num>.<slug>.{js,py}` | Solutions, e.g. `work/Easy/Array/1.two-sum.py`. Machine-parsed header comment (title / `Difficulty:` / URL / `─` rule / statement) — preserve its exact shape |
+| `work/<1\|3\|7>/<Difficulty>/<Category>/<num>.<slug>.{js,py}` | Solutions, e.g. `work/1/Easy/Array/1.two-sum.py`. The top directory is the spaced-repetition bucket: `1` = first solve, `3`/`7` = the blind re-solves of that problem 3 and 7 days later. Machine-parsed header comment (title / `Difficulty:` / URL / `─` rule / statement) — preserve its exact shape |
 | `apps/cli/` | Flat Bun TS workspace: automation entries (shebang + top-level await) and libraries (no shebang, side-effect-free on import). Root `bun run` scripts delegate here |
 | `apps/docs/` | Blume site (`blume.config.ts`, `content/`, `islands/`, `public/`). `content/(<category>)/<num>-<slug>.mdx` generated by sync |
-| `apps/api/` | Cloudflare Worker workspace: `src/` modules, `data/schedule.json` (day → topic issue, human-edited, bundled at deploy), `migrations/`, `scripts/import-srs.ts` |
+| `apps/api/` | Cloudflare Worker workspace: `src/` modules, `data/schedule.json` (day → topic issue, human-edited, bundled at deploy), `migrations/` (append-only; `0002` is the +3/+7 ladder rebuild) |
-| `.github/workflows/` | deploy (docs → Pages, Worker → Cloudflare, on every main push), close-solved, close-topics, sync-d1 (issue edits → `/admin/reconcile`) |
+| `.github/workflows/` | deploy (docs → Pages, Worker → Cloudflare, on every main push), close-solved (issues + `/admin/solved` + Project `Set`/`Difficulty`, needs `SRS_ADMIN_KEY` and `PROJECT_PAT`), close-topics, sync-d1 (issue edits → `/admin/reconcile`), spaced-repetition (daily 06:00 ET cron → today's review issue; `GITHUB_TOKEN` only, no secrets) |
 
 ## Development Commands
 
 All from the repo root (a Bun workspace over `apps/*`):
 
 ```sh
-bun run pick            # scaffold a solution via leetcode-cli (fuzzy picker)
+bun run pick            # scaffold a solution via leetcode-cli (fuzzy picker; Tab cycles the
-bun run test            # run ONE solution against LeetCode's judge (not a test suite)
+                        # sections: new problems → work/1, then the owed 3-day and 7-day
-bun run sync            # work/ → apps/docs/content/ pages
+                        # re-solves → work/3, work/7. Each section hides what its own bucket
+                        # already holds; index+descriptions cached in
+                        # ~/.local/share/leetcode/data.db — see apps/cli/db.ts)
+bun run test            # run ONE solution against LeetCode's judge (not a test suite;
+                        # most recently tested first, stamped in the db on exit 0)
+bun run submit          # submit ONE solution to LeetCode (newest scaffold first, nothing
+                        # hidden; last_submitted stamped in the db on exit 0)
+bun run sync            # work/1 → apps/docs/content/ pages (re-solves are never published)
 bun run dev|build       # Blume docs site (runs in apps/docs/)
 bun run close-solved -- --dry-run    # issue reconcilers (also DRY_RUN=1)
 bun run close-topics -- --dry-run
-bun run api:dev         # wrangler dev on :8787 (local D1); api:test = DST guard tests
+# close-solved also pushes the solved set to the Worker; point it at a local
+# one and nothing production is touched:
+SRS_API=http://localhost:8787 SRS_ADMIN_KEY=$LINK_KEY bun run close-solved -- --dry-run
+# Project Set/Difficulty from the issue labels (needs a `project`-scoped token;
+# runs as the last step of close-solved.yml in CI):
+GH_TOKEN=$PROJECT_PAT bun run sync-project-fields -- --dry-run
+# today's review issue from the +3d/+7d closes (--date backfills a missed day;
+# a Sunday date writes nothing — the rest day has no assignment):
+bun run spaced-repetition -- --dry-run --date=2026-08-31
+bun run api:dev         # wrangler dev on :8787 (local D1)
+bun run api:test        # DST guards + the rest-day calendar sweep
 bun run api:deploy      # deploy the Worker by hand (CI also deploys on main pushes)
 curl -X POST -H "Authorization: Bearer $LINK_KEY" \
   "localhost:8787/admin/digest?dry=1&date=2026-08-30"   # preview a digest, send nothing
@@ -63,18 +88,19 @@ curl -X POST -H "Authorization: Bearer $LINK_KEY" \
 - **Dry-run everything:** reconcilers take `--dry-run`/`DRY_RUN=1`; Worker admin routes take `?dry=1&force=1&date=` (the `SRS_TODAY` equivalent) and `wrangler dev` runs against local D1 — exercise logic there before touching production state.
 - **Dates:** always ET calendar strings (`YYYY-MM-DD`), arithmetic anchored at noon UTC (`atNoon` in `apps/api/src/srs.ts`) to dodge DST. Never `new Date()` math directly.
 - **Style:** section-divider comments (`// ── name ───`), file-top doc comments explaining the *why* and invariants, 2-space JSON with trailing newline, `Map` for dynamic keys / `Record` for static tables, no tiny one-expression wrapper functions.
-- **Known intentional duplication:** `close-solved.ts` re-implements header stripping instead of importing from `sync.ts` because `sync.ts` runs its pipeline on import. Don't "deduplicate" it.
+- **Known intentional duplication:** `sync.ts` keeps its own header split instead of sharing `apps/cli/source.ts`, because `sync.ts` runs its whole pipeline on import and so cannot be imported from. Don't "deduplicate" it. `close-solved.ts` and `work.ts` do share it — the stub test decides both "close the issue" and "owes a review", and the two must never disagree.
 
 ## Important Files
 
-- `apps/api/src/srs.ts` — SRS domain: ladder (`new → +2 → +5 → +10 → retired`; fail resets to `+2`; first-ever log enters at `+2`), ET date math, seeded sampling, `logAttempt()` (the ONE write path — email taps, webhook, gate scoring all converge here).
+- `apps/api/src/srs.ts` — SRS domain: the ladder (`new → +3 → +7 → retired`; fail resets to `+3`; first-ever log enters at `+3`), `WINDOWS`/`STAGES` (the one vocabulary shared by the charts, the `work/<n>` buckets and the review issues), ET date math, `workingDay()` (no scheduled date is ever a Sunday), seeded sampling, `logAttempt()` (the ONE write path — email taps, webhook, gate scoring all converge here), and overload leveling: at most `REVIEW_CAP` (3) reviews surface per day — `levelReviews()` (run by `sendDigest` on real sends only, never dry) gives everything past the cap a concrete future WORKING day, ≤ 3 per day, oldest first, instead of letting the due pile grow.
 - `apps/api/src/index.ts` — router + cron dispatch; `apps/api/wrangler.jsonc` — bindings (`DB`, `EMAIL`), crons, vars; secrets `GH_PAT`/`WEBHOOK_SECRET`/`LINK_KEY` via `wrangler secret put`.
 - `apps/api/src/digest.ts` / `apps/api/src/email.tsx` — the daily digest, split data/presentation. `digest.ts` reads D1 into a `DigestData`; `email.tsx` owns every colour and every sentence, and renders both the HTML and (via its own `plainDigest`, not React Email's `plainText` mode, which flattens the tables) the text alternative. The retrieval rules hold by construction: `DigestRow` has no title and no issue field, so a review or drill line *cannot* leak the topic or a solution link. Subject is `(Day N/56) LeetCode Daily Digest`.
 - `apps/api/src/png.ts` — hand-rolled PNG encoder (RGB8, one IDAT, zlib via `CompressionStream("deflate")`, CRC32, 5×7 bitmap font). It exists because every major email client refuses remote SVG, so `/chart/heatmap.png` rasters the heatmap for the digest while `/chart/heatmap.svg` keeps serving the README byte-for-byte. Both come from one `heatmapCells()` so the two pictures cannot drift.
 - `apps/cli/sync.ts` — work→docs contract: only `## Solution` onward is script-owned on existing pages; human prose is never touched; never hand-write solution pages or edit inside `## Solution`.
+- `apps/cli/work.ts` — the `work/` layout: bucket paths, `firstSolved()` (one `git log`, ET dates, keyed by LC number so past layout moves don't matter), and `reviewQueues()` (what each window still owes). Everything that needs to know where a solution file lives, or when it was solved, goes through here.
 - `README.md` live charts are Worker endpoints (`/chart/*.svg`, `/badge/gate.svg`, 5-min Camo cache); the docs `/progress` page fetches `/api/stats` client-side (`apps/docs/islands/ProgressDashboard.tsx`).
 - `apps/docs/blume.config.ts` — site base `/leetcode`; `README.md` campaign table doubles as topic-map input to `sync.ts` (`readmeTopics()`, `TOPIC_ALIASES`).
-- Old `.github/srs/` JSON state and the `srs-*` Actions are RETIRED — do not resurrect; `apps/api/scripts/import-srs.ts` documents the migration.
+- Old `.github/srs/` JSON state, its `srs-*` Actions, and the one-shot `import-srs.ts` importer are RETIRED and deleted — do not resurrect; git history is the record.
 
 ## Runtime/Tooling Preferences
 

README.md

@@ -10,7 +10,9 @@
 
 <p align="center">
   <sub>8-week interview-prep fight camp. Each phase is a milestone; each topic an issue; each problem a sub-issue.<br>
-  Charts are live from the SRS Worker — the daily digest email drives the schedule.</sub>
+  New topic Mon–Fri, gate on Saturday, Sunday off — every solve comes back at <strong>+3</strong> and <strong>+7</strong> days,
+  the two windows that keep the rest day clear (a Thursday solve's +3 slides to Monday).<br>
+  Charts are live from the SRS Worker, never committed: pushing a solution or tapping the daily digest moves them within ~5 min.</sub>
 </p>
 
 <table align="center">
@@ -18,7 +20,7 @@
     <td colspan="2" align="center"><img alt="phase progress" width="100%" src="https://srs-api.prdlk.workers.dev/chart/progress.svg" /></td>
   </tr>
   <tr>
-    <td align="center" width="53%"><img alt="SRS ladder" width="100%" src="https://srs-api.prdlk.workers.dev/chart/ladder.svg" /></td>
+    <td align="center" width="53%"><img alt="SRS ladder — new / +3 / +7 / retired" width="100%" src="https://srs-api.prdlk.workers.dev/chart/ladder.svg" /></td>
     <td align="center" width="47%"><img alt="attempt heatmap" width="100%" src="https://srs-api.prdlk.workers.dev/chart/heatmap.svg" /></td>
   </tr>
 </table>

apps/api/README.md

@@ -16,16 +16,33 @@ Live at `https://srs-api.prdlk.workers.dev`.
   never overwrites SRS-owned columns (`stage`, `next_review`).
 - **The repo owns the schedule** — `data/schedule.json`, human-edited,
   bundled at deploy. Git history is its audit log.
-- The GitHub Project mirror (`Target Date`, `SRS Stage`, `First Attempt`)
+- The GitHub Project mirror writes `Target Date` and nothing else: it is
-  is best-effort: failures log warnings, never block a D1 write. Topic rows
+  best-effort, so failures log warnings and never block a D1 write, and topic
-  are never written.
+  rows are never written. SRS stage and first-attempt result stay in D1 only —
+  the charts, digest and `/api/stats` read them from there, so mirroring them
+  into Project single-selects bought only drift. Do not re-add them.
+  `Set`/`Difficulty` are a projection of the issue labels, reconciled by
+  `bun run sync-project-fields` at the repo root, not by this Worker.
 
 ## The ladder
 
-`new → +2 → +5 → +10 → retired`; pass advances, fail resets to `+2`.
+`new → +3 → +7 → retired`; pass advances, fail resets to `+3`. A problem's
-A problem's first-ever log enters at `+2` regardless of result. Stage names
+first-ever log enters at `+3` regardless of result. Stage names the NEXT
-the NEXT review's interval. All dates are ET calendar strings anchored at
+review's interval, and the two rungs are the same numbers as the `work/3` and
-noon UTC (`src/srs.ts`) — never raw `Date` math.
+`work/7` buckets `bun run pick` scaffolds re-solves into.
+
+**Sunday is never booked.** Topics run Mon–Fri, the gate is Saturday, and 3/7
+are chosen so a solve returns on a working day: only a Thursday solve's `+3`
+would land on the rest day, and `workingDay()` in `src/srs.ts` slides it to
+Monday. Every scheduled date in the Worker — ladder reviews, levelled
+overflow, deferred-Hard release dates — is minted by that one function, so the
+rest day cannot be booked and then swallowed by the digest's Sunday branch.
+Reviews may slip later, never earlier: pulling one back to Saturday would
+shorten the interval it exists to test. `src/srs.test.ts` sweeps the whole
+campaign calendar to prove it.
+
+All dates are ET calendar strings anchored at noon UTC (`src/srs.ts`) — never
+raw `Date` math.
 
 Blind drills draw only from topics **already learned**: scheduled in an
 earlier week (the current week's optional pool is reserved for Saturday's
@@ -40,6 +57,8 @@ day never feeds drills just because its calendar week lapsed.
 | `POST /webhook/github` | HMAC (`WEBHOOK_SECRET`) | `/done <n> pass\|fail` comments (owner only, any issue); `review`-issue close → gate scoring |
 | `GET /chart/{progress,ladder,heatmap}.svg`, `GET /badge/gate.svg` | public | hand-rolled SVGs, `max-age=300` (GitHub Camo's freshness floor) |
 | `GET /api/stats` | public, CORS-pinned to the docs origin | one JSON document for `/progress` |
+| `POST /admin/solved` | `Authorization: Bearer <LINK_KEY>` | `{"solved":[{"lc":1,"bucket":1},…]}` — solutions committed under `work/`; the bucket names the rung it settles (1 → `new`, 3 → `+3`, 7 → `+7`), so a first solve enters the ladder and a pushed re-solve advances it. Writes only when the problem stands on that rung, which is what makes re-posting the whole set a no-op. Takes `?dry=1&date=` |
+| `POST /admin/due` | `Authorization: Bearer <LINK_KEY>` | read-only: what the ladder has due on `?date=` (default today), oldest first, with the rung/bucket, how late it is, and when it was last seen. The one answer behind the daily `Spaced Repetition` issue |
 | `POST /admin/{digest,review,reconcile}` | `Authorization: Bearer <LINK_KEY>` | manual triggers; `digest` takes `?dry=1&force=1&date=` |
 
 ## Crons (DST-proof)
@@ -59,9 +78,23 @@ routes). Bindings in `wrangler.jsonc`: `DB` (D1 `srs`), `EMAIL`
 (`send_email`, restricted to the verified destination). Sender domain
 `prdlk.com` is onboarded to Email Sending.
 
-The `sync-d1.yml` Actions workflow additionally pushes curriculum issue
+Three Actions workflows talk to this Worker with the `SRS_ADMIN_KEY` repo
-edits into D1 immediately (`POST /admin/reconcile` with the
+secret:
-`SRS_ADMIN_KEY` repo secret); the morning cron is the backstop.
+
+- `sync-d1.yml` sends curriculum issue edits to `POST /admin/reconcile` (the
+  morning cron is the backstop).
+- `close-solved.yml` sends the whole implemented `work/` set — each entry
+  tagged with its bucket — to `POST /admin/solved` on every push to `main`.
+  That call is what keeps a committed solution from being invisible here:
+  closing an issue is not a state change the Worker can see (the catalog
+  reconcile ignores issue state, and only `logAttempt()` moves the ladder), and
+  the bucket is what lets a pushed re-solve advance `+3 → +7` instead of
+  being read as a stale first solve. `close-solved` still owns the issue close
+  itself (it knows the files and the commit), so this path only writes D1 and
+  mirrors Project fields.
+- `spaced-repetition.yml` reads `POST /admin/due` at 06:00 ET and renders
+  today's `Spaced Repetition` issue. Read-only, and the only schedule involved
+  is this Worker's ladder.
 
 ## Local dev
 
@@ -72,13 +105,14 @@ bunx wrangler d1 migrations apply srs --local
 bun run dev                          # wrangler dev on :8787, local D1
 curl -X POST -H "Authorization: Bearer $LINK_KEY" \
   "localhost:8787/admin/digest?dry=1&date=2026-08-31"   # prints HTML, sends nothing
-bun test src                         # DST guard + date math
+bun test src                         # DST guards, date math, the rest-day sweep
 ```
 
-`?date=` on admin routes is the `SRS_TODAY` equivalent. The one-shot
+`?date=` on admin routes is the `SRS_TODAY` equivalent. Migrations are
-migration from the retired `.github/srs/srs.json` lives at
+append-only and applied in order; `0002_ladder_3_7.sql` is the +2/+5/+10 →
-`scripts/import-srs.ts` (`--remote` for production D1); it is re-runnable —
+`+3`/`+7` rebuild, which also lifts every date that was sitting on a Sunday.
-import-sourced attempts are wiped and re-inserted.
+The one-shot importer for the retired `.github/srs/srs.json` is gone — that
+state no longer exists, and git history is its record.
 
 ## Deploy
 

apps/api/migrations/0001_init.sql

@@ -18,12 +18,14 @@ CREATE TABLE attempts (
   date      TEXT NOT NULL,
   kind      TEXT NOT NULL,                 -- first|review|drill|gate
   result    TEXT NOT NULL,                 -- pass|fail
-  source    TEXT NOT NULL                  -- email|webhook|import
+  source    TEXT NOT NULL                  -- email|webhook|commit|import
 );
 
 -- One-tap email links must be idempotent (same link twice = no-op), but
 -- /done webhook corrections (pass then fail, same day) must stay legal —
--- so uniqueness applies to email-sourced attempts only.
+-- so uniqueness applies to email-sourced attempts only. Commit-sourced
+-- attempts need no index: logAttempt() only accepts them for a stage-'new'
+-- problem, so a re-push cannot insert a second one.
 CREATE UNIQUE INDEX attempts_email_once
   ON attempts (lc_number, date, kind) WHERE source = 'email';
 CREATE INDEX attempts_by_date ON attempts (date);

apps/api/migrations/0002_ladder_3_7.sql

@@ -0,0 +1,31 @@
+-- Ladder rebuild: +2/+5/+10 → +3/+7, and no scheduled date on a Sunday.
+--
+-- The old three rungs scattered reviews across every weekday, so roughly one
+-- review in seven came due on the rest day: the digest hid it (Sunday builds
+-- an empty body) and Monday inherited the pile. The campaign's windows are 3
+-- and 7 days — the same numbers as the work/3 and work/7 buckets and the
+-- Spaced Repetition issue windows — and srs.ts now mints every date through
+-- workingDay(), which never returns a Sunday.
+--
+-- Stage remap keeps earned progress: a problem at +5 has passed one review, so
+-- it owes the 7-day one; a problem at +10 has passed two and is done. Existing
+-- next_review dates keep their day (recomputing them would move work the
+-- reader has already been told about) — only Sunday landings shift, forward to
+-- Monday, because a review may come later than its interval but never sooner.
+--
+-- problems.stage is now: new | +3 | +7 | retired
+
+UPDATE problems SET stage = '+3' WHERE stage = '+2';
+UPDATE problems SET stage = '+7' WHERE stage = '+5';
+UPDATE problems SET stage = 'retired', next_review = NULL WHERE stage = '+10';
+
+UPDATE problems
+   SET next_review = date(next_review, '+1 day')
+ WHERE next_review IS NOT NULL AND strftime('%w', next_review) = '0';
+
+-- defer_until is the deferred Hards' release date; catalog.ts spreads them two
+-- per working day, so the same rule applies. next_review tracks it for a row
+-- that is still `new`, and the shift above kept the two in step.
+UPDATE problems
+   SET defer_until = date(defer_until, '+1 day')
+ WHERE defer_until IS NOT NULL AND strftime('%w', defer_until) = '0';

apps/api/scripts/import-srs.ts

@@ -1,94 +0,0 @@
-#!/usr/bin/env bun
-/**
- * One-shot migration: .github/srs/srs.json → D1.
- *
- * Run AFTER the catalog reconcile has filled `problems` (the import only
- * overlays SRS-owned fields — stage, next_review, defer_until — and inserts
- * attempts/topic counters). Re-runnable without duplicates: import-sourced
- * attempts are wiped and re-inserted, everything else upserts.
- *
- *   bun apps/api/scripts/import-srs.ts            # local D1 (wrangler dev state)
- *   bun apps/api/scripts/import-srs.ts --remote   # production D1
- *
- * Prints row counts; verify them against srs.json before deleting anything.
- */
-import { $ } from "bun";
-import { join } from "node:path";
-
-const ROOT = join(import.meta.dir, "..", "..");
-const API = join(ROOT, "api");
-const REMOTE = process.argv.includes("--remote");
-
-interface Attempt {
-  date: string;
-  kind: string;
-  result: string;
-}
-interface Problem {
-  issue: number;
-  topic: number;
-  difficulty: string;
-  set: string;
-  solved_on?: string;
-  stage: string;
-  next_review?: string;
-  defer_until?: string;
-  history: Attempt[];
-}
-interface State {
-  problems: Record<string, Problem>;
-  topics: Record<string, { misses: number; boost: boolean }>;
-  drill_pool_used: number[];
-}
-
-const state: State = JSON.parse(
-  await Bun.file(join(ROOT, ".github", "srs", "srs.json")).text(),
-);
-
-const q = (v: string | null | undefined) => (v == null ? "NULL" : `'${v}'`);
-const lines: string[] = ["DELETE FROM attempts WHERE source = 'import';"];
-
-let attempts = 0;
-for (const [lc, p] of Object.entries(state.problems)) {
-  lines.push(
-    `UPDATE problems SET stage = ${q(p.stage)}, next_review = ${q(p.next_review ?? null)}, ` +
-      `defer_until = ${q(p.defer_until ?? null)} WHERE lc_number = ${Number(lc)};`,
-  );
-  for (const a of p.history) {
-    lines.push(
-      `INSERT INTO attempts (lc_number, date, kind, result, source) ` +
-        `VALUES (${Number(lc)}, ${q(a.date)}, ${q(a.kind)}, ${q(a.result)}, 'import');`,
-    );
-    attempts++;
-  }
-}
-for (const [topic, t] of Object.entries(state.topics)) {
-  lines.push(
-    `UPDATE topics SET misses = ${t.misses}, boost = ${t.boost ? 1 : 0} WHERE issue = ${Number(topic)};`,
-  );
-}
-for (const lc of state.drill_pool_used) {
-  lines.push(`INSERT OR IGNORE INTO drill_pool_used (lc_number) VALUES (${lc});`);
-}
-
-const sqlPath = join(API, "migrations", ".import.sql");
-await Bun.write(sqlPath, lines.join("\n") + "\n");
-const flag = REMOTE ? "--remote" : "--local";
-await $`bunx wrangler d1 execute srs ${flag} --file ${sqlPath}`.cwd(API);
-await $`rm ${sqlPath}`;
-
-const counts =
-  await $`bunx wrangler d1 execute srs ${flag} --json --command ${"SELECT (SELECT COUNT(*) FROM problems) AS problems, (SELECT COUNT(*) FROM problems WHERE stage != 'new') AS laddered, (SELECT COUNT(*) FROM problems WHERE defer_until IS NOT NULL) AS deferred, (SELECT COUNT(*) FROM attempts WHERE source='import') AS imported_attempts, (SELECT COUNT(*) FROM topics) AS topics, (SELECT COUNT(*) FROM drill_pool_used) AS drills_used"}`
-    .cwd(API)
-    .json();
-
-const expected = {
-  json_problems: Object.keys(state.problems).length,
-  json_attempts: attempts,
-  json_laddered: Object.values(state.problems).filter((p) => p.stage !== "new").length,
-  json_deferred: Object.values(state.problems).filter((p) => p.defer_until).length,
-  json_topics: Object.keys(state.topics).length,
-  json_drills_used: state.drill_pool_used.length,
-};
-console.log("expected from srs.json:", JSON.stringify(expected));
-console.log("in D1:", JSON.stringify(counts[0]?.results?.[0] ?? counts));

apps/api/src/catalog.ts

@@ -4,13 +4,21 @@
  * rows from scratch on every run — re-runs are no-ops. SRS-owned columns
  * (stage, next_review) are NEVER overwritten; defer_until is set once, on
  * first sight of a deferred problem. The Worker never invents catalog rows.
+ *
+ * Difficulty and set come from the `diff:*` / `set:*` LABELS, never from the
+ * issue title — the title carries only the LC number and the problem's name,
+ * so relabelling a problem is enough to move it and titles stay readable.
+ * The `problem` label is what marks a sub-issue as curriculum.
  */
-import { addDays } from "./srs.ts";
+import { workingDay } from "./srs.ts";
 import type { GitHub } from "./github.ts";
 
-const TITLE_RE = /^LC (\d+) · (.+) · (Easy|Medium|Hard) · (core|optional|deferred)$/;
+const TITLE_RE = /^LC (\d+) · (.+)$/;
 
-/** Deferred Hards enter the queue from this date, two per day. */
+const DIFFICULTIES = ["easy", "medium", "hard"] as const;
+const SETS = ["core", "optional", "deferred"] as const;
+
+/** Deferred Hards enter the queue from this date, two per working day. */
 const DEFER_FROM = "2026-09-28";
 
 export interface ReconcileReport {
@@ -18,6 +26,18 @@ export interface ReconcileReport {
   problems: number;
 }
 
+/** Label names on one issue payload, narrowed with guards rather than cast. */
+function labelNames(value: object): string[] {
+  if (!("labels" in value) || !Array.isArray(value.labels)) return [];
+  const names: string[] = [];
+  for (const label of value.labels) {
+    if (label && typeof label === "object" && "name" in label && typeof label.name === "string") {
+      names.push(label.name);
+    }
+  }
+  return names;
+}
+
 export async function reconcileCatalog(db: D1Database, gh: GitHub): Promise<ReconcileReport> {
   interface TopicIssue {
     number: number;
@@ -62,13 +82,24 @@ export async function reconcileCatalog(db: D1Database, gh: GitHub): Promise<Reco
       if (!raw || typeof raw !== "object") continue;
       if (!("number" in raw) || typeof raw.number !== "number") continue;
       if (!("title" in raw) || typeof raw.title !== "string") continue;
+      const labels = labelNames(raw);
+      if (!labels.includes("problem")) continue; // non-curriculum sub-issue
       const m = raw.title.match(TITLE_RE);
-      if (!m) continue; // non-curriculum sub-issue
+      if (!m) {
+        console.warn(`catalog: #${raw.number} is a problem but not titled "LC <n> · <name>"`);
+        continue;
+      }
+      const difficulty = DIFFICULTIES.find((d) => labels.includes(`diff:${d}`));
+      const set = SETS.find((s) => labels.includes(`set:${s}`));
+      if (!difficulty || !set) {
+        console.warn(`catalog: #${raw.number} is missing a diff:/set: label — skipped`);
+        continue;
+      }
       const lc = Number(m[1]);
-      const set = m[4]!;
+      // Two deferred Hards per WORKING day from DEFER_FROM, in catalog walk
-      // Two deferred Hards per day from DEFER_FROM, in catalog walk order —
+      // order — applied only when the row is first created (SRS owns it
-      // applied only when the row is first created (SRS owns it afterwards).
+      // afterwards). Sunday is skipped like every other scheduled date.
-      const defer = set === "deferred" ? addDays(DEFER_FROM, Math.floor(deferredSeen / 2)) : null;
+      const defer = set === "deferred" ? workingDay(DEFER_FROM, Math.floor(deferredSeen / 2)) : null;
       if (set === "deferred") deferredSeen++;
       statements.push(
         db
@@ -78,7 +109,7 @@ export async function reconcileCatalog(db: D1Database, gh: GitHub): Promise<Reco
              ON CONFLICT(lc_number) DO UPDATE SET
                issue = ?2, topic_issue = ?3, title = ?4, difficulty = ?5, set_label = ?6`,
           )
-          .bind(lc, raw.number, t.number, m[2]!, m[3]!.toLowerCase(), set, defer),
+          .bind(lc, raw.number, t.number, m[2]!, difficulty, set, defer),
       );
       problems++;
     }

apps/api/src/charts.ts

@@ -14,6 +14,7 @@
  * badges: rounded #09090b cards, #fafafa/#a1a1aa text, GitHub dark-mode
  * green ramp. Every function renders on a zero-row DB.
  */
+import { STAGES } from "./srs.ts";
 import { Canvas, textWidth } from "./png.ts";
 
 // D1Database comes from the generated worker-configuration.d.ts runtime types.
@@ -43,8 +44,6 @@ const PHASES = [
   { milestone: 5, name: "V — Decision Space" },
 ];
 
-const STAGES = ["new", "+2", "+5", "+10", "retired"];
-
 // ── svg helpers ──────────────────────────────────────────────────
 
 /** Opening tag plus the rounded dark card every chart starts with. */
@@ -159,6 +158,9 @@ export async function progressChart(db: D1Database): Promise<string> {
 
 // ── ladder: bar per stage ────────────────────────────────────────
 
+// One bar per rung, labelled and ordered by srs.ts's STAGES, so changing the
+// ladder can never leave a stale bar here: the slot width is derived from the
+// rung count, only the bar width inside a slot is fixed.
 export async function ladderChart(db: D1Database): Promise<string> {
   const { results } = await db
     .prepare(`SELECT stage, COUNT(*) AS count FROM problems GROUP BY stage`)

apps/api/src/digest.ts

@@ -8,22 +8,28 @@
  * Retrieval rules: review and drill rows carry number + difficulty only —
  * never the topic, never a solution link. `DigestRow` has no field for
  * either, so the rule holds by construction. The learning day's core list is
- * the only labeled section. Reviews + drills ≤ 6, reviews first, overflow
+ * the only labeled section. At most REVIEW_CAP (3) reviews per day; drills
- * simply stays due (oldest tomorrow). Sunday is a two-line rest note.
+ * fill toward DAILY_CAP (6) only when the due queue is light. Overflow is
+ * levelled, not stacked: sendDigest gives every review past the cap a
+ * concrete future date, ≤ REVIEW_CAP per day, oldest first. Sunday is a
+ * two-line rest note.
  *
  * Idempotency: email_log keys sends by ET date — a same-day re-send is a
  * no-op unless forced; the body itself is deterministic (drill picks are
- * seeded by the date).
+ * seeded by the date). Levelling keeps that: it runs once, before the send,
+ * and a re-run finds nothing left over the cap.
  */
 import {
   CAMPAIGN_DAYS,
   type ProblemRow,
+  REVIEW_CAP,
   SCHEDULE,
   addDays,
   campaignDay,
   campaignWeek,
   dueReviews,
   isoWeek,
+  levelReviews,
   pickDrills,
   prettyDate,
   streak,
@@ -32,6 +38,7 @@ import {
 import { type DigestData, type DigestRow, renderDigest } from "./email.tsx";
 import { signLink } from "./links.ts";
 
+/** Total daily ceiling: drills only fill what the whole due queue leaves. */
 const DAILY_CAP = 6;
 
 export interface Digest {
@@ -61,10 +68,12 @@ export async function collectDigest(env: Env, date: string): Promise<DigestData>
   const db = env.DB;
   const rest = weekdayOf(date) === 0;
 
-  // Reviews take the cap first; drills fill whatever is left.
+  // Reviews surface at most REVIEW_CAP; drills fill toward DAILY_CAP only
+  // when the WHOLE due queue is light — a heavy backlog must never trade
+  // review slots for brand-new drill problems.
   const due = rest ? [] : await dueReviews(db, date);
-  const capped = due.slice(0, DAILY_CAP);
+  const capped = due.slice(0, REVIEW_CAP);
-  const drills = rest ? [] : await pickDrills(db, date, DAILY_CAP - capped.length);
+  const drills = rest ? [] : await pickDrills(db, date, DAILY_CAP - Math.min(due.length, DAILY_CAP));
 
   const data: DigestData = {
     day: prettyDate(date),
@@ -96,6 +105,7 @@ export async function collectDigest(env: Env, date: string): Promise<DigestData>
       name: topic?.name ?? `#${topicIssue}`,
       core: core.map((p) => ({
         lc: p.lc_number,
+        difficulty: p.difficulty,
         url: `https://github.com/${env.REPO}/issues/${p.issue}`,
         solved: p.stage !== "new",
       })),
@@ -164,6 +174,11 @@ export async function sendDigest(
     .first();
   if (already && !opts.force) return { sent: false, reason: "already sent today", digest };
 
+  // The digest above was built against the un-levelled queue (so `carried`
+  // reports the real backlog); now give everything past the cap its future
+  // date. Dry runs never reach here, and a forced re-send finds nothing left.
+  await levelReviews(env.DB, date);
+
   await env.EMAIL.send({
     to: env.TO_EMAIL,
     from: { email: env.FROM_EMAIL, name: "SRS" },

apps/api/src/email.tsx

@@ -35,6 +35,7 @@ import {
 } from "@react-email/components";
 import { render } from "@react-email/render";
 import type { CSSProperties } from "react";
+import { REVIEW_CAP } from "./srs.ts";
 
 // ── palette (GitHub dark) ────────────────────────────────────────
 const CANVAS = "#010409";
@@ -61,12 +62,12 @@ const DIFFICULTY: Record<string, { label: string; color: string }> = {
   hard: { label: "Hard", color: RED },
 };
 
-// The SRS ladder in plain English — "+5" means the last look was 5 days back.
+// The SRS ladder in plain English — stage "+3" means the last clean look was
+// three days back, so that is what the reader is told.
 const LAST_SEEN: Record<string, string> = {
   new: "first look",
-  "+2": "2 days ago",
+  "+3": "3 days ago",
-  "+5": "5 days ago",
+  "+7": "7 days ago",
-  "+10": "10 days ago",
   retired: "retired",
 };
 
@@ -82,6 +83,14 @@ export interface DigestRow {
   failUrl: string;
 }
 
+/** A learning-day core problem — the only rows allowed a link. */
+export interface TopicRow {
+  lc: number;
+  difficulty: string;
+  url: string;
+  solved: boolean;
+}
+
 export interface DigestData {
   /** "Tuesday, August 25" */
   day: string;
@@ -89,9 +98,9 @@ export interface DigestData {
   progress: string;
   streak: number;
   rest: boolean;
-  topic?: { name: string; core: { lc: number; url: string; solved: boolean }[] };
+  topic?: { name: string; core: TopicRow[] };
   reviews: DigestRow[];
-  /** Reviews past the daily cap; they simply stay due. */
+  /** Reviews past the daily cap; levelled onto the coming days. */
   carried: number;
   drills: DigestRow[];
   gate?: { week: number; url: string };
@@ -196,6 +205,48 @@ function ProblemTable({ rows, staged }: { rows: DigestRow[]; staged: boolean })
   );
 }
 
+/**
+ * The learning day's core list as the same table shape as reviews — this is
+ * the one section allowed to link problems, and ticks replace tap buttons.
+ */
+function TopicTable({ rows }: { rows: TopicRow[] }) {
+  return (
+    <table
+      width="100%"
+      border={0}
+      cellPadding={0}
+      cellSpacing={0}
+      style={{ borderCollapse: "collapse", width: "100%" }}
+    >
+      <thead>
+        <tr>
+          <th style={th}>Problem</th>
+          <th style={th}>Level</th>
+          <th style={{ ...th, textAlign: "right" }}>Solved</th>
+        </tr>
+      </thead>
+      <tbody>
+        {rows.map((p) => {
+          const difficulty = DIFFICULTY[p.difficulty];
+          return (
+            <tr key={p.lc}>
+              <td style={{ ...td, fontWeight: 600 }}>
+                <Link href={p.url} style={{ color: p.solved ? MUTED : LINK, textDecoration: "none" }}>
+                  LC {p.lc}
+                </Link>
+              </td>
+              <td style={{ ...td, color: difficulty?.color ?? INK }}>{difficulty?.label ?? p.difficulty}</td>
+              <td style={{ ...td, color: p.solved ? GREEN : MUTED, textAlign: "right" }}>
+                {p.solved ? "✓" : "—"}
+              </td>
+            </tr>
+          );
+        })}
+      </tbody>
+    </table>
+  );
+}
+
 function Block({
   title,
   note,
@@ -251,7 +302,7 @@ function DigestEmail({ data }: { data: DigestData }) {
             <Text style={{ color: MUTED, fontSize: "13px", margin: "8px 0 0" }}>
               {data.progress}
               {data.rest
-                ? " · nothing is due today, and anything overdue waits for Monday."
+                ? " · the ladder never books a Sunday, so nothing is due — anything still open waits for Monday."
                 : data.streak === 0
                   ? " · no streak going yet — today is a good day to start one."
                   : ` · 🔥 ${data.streak} day${data.streak === 1 ? "" : "s"} in a row, keep it going.`}
@@ -265,18 +316,8 @@ function DigestEmail({ data }: { data: DigestData }) {
                     <Text style={{ color: INK, fontSize: "16px", fontWeight: 600, margin: "0 0 8px" }}>
                       {data.topic.name}
                     </Text>
-                    <Text style={{ ...hint, margin: 0 }}>
+                    <Text style={hint}>Work through these from the top — a tick means it is already solved.</Text>
-                      Work through these — ticked ones you have already solved:{" "}
+                    <TopicTable rows={data.topic.core} />
-                      {data.topic.core.map((p, i) => (
-                        <span key={p.lc}>
-                          {i > 0 ? " · " : ""}
-                          <Link href={p.url} style={{ color: p.solved ? MUTED : LINK, textDecoration: "none" }}>
-                            LC {p.lc}
-                          </Link>
-                          {p.solved ? <span style={{ color: GREEN }}> ✓</span> : null}
-                        </span>
-                      ))}
-                    </Text>
                   </Section>
                 ) : null}
 
@@ -289,8 +330,8 @@ function DigestEmail({ data }: { data: DigestData }) {
                 />
                 {data.carried > 0 ? (
                   <Text style={{ ...hint, margin: "12px 0 0" }}>
-                    {data.carried} more {data.carried === 1 ? "is" : "are"} waiting — they come back
+                    {data.carried} more {data.carried === 1 ? "is" : "are"} waiting — spread over the
-                    tomorrow, oldest first.
+                    coming days, oldest first, never more than {REVIEW_CAP} a day.
                   </Text>
                 ) : null}
 
@@ -362,7 +403,7 @@ function plainDigest(data: DigestData): string {
     data.rest ? `Take the day off — ${data.day}` : `Good morning. It's ${data.day}.`,
     data.progress +
       (data.rest
-        ? " · nothing is due today, and anything overdue waits for Monday."
+        ? " · the ladder never books a Sunday, so nothing is due — anything still open waits for Monday."
         : data.streak === 0
           ? " · no streak going yet — today is a good day to start one."
           : ` · ${data.streak} day${data.streak === 1 ? "" : "s"} in a row, keep it going.`),
@@ -373,8 +414,11 @@ function plainDigest(data: DigestData): string {
       out.push(
         "",
         `SOMETHING NEW TODAY — ${data.topic.name}`,
-        "Work through these; the ones marked done you have already solved.",
+        "Work through these from the top; the ones marked done you have already solved.",
-        ...data.topic.core.map((p) => `  LC ${p.lc}${p.solved ? " (done)" : ""} — ${p.url}`),
+        ...data.topic.core.map(
+          (p) =>
+            `  LC ${p.lc} — ${DIFFICULTY[p.difficulty]?.label ?? p.difficulty}${p.solved ? " (done)" : ""} — ${p.url}`,
+        ),
       );
     }
 
@@ -411,7 +455,7 @@ function plainDigest(data: DigestData): string {
     if (data.carried > 0) {
       out.push(
         "",
-        `${data.carried} more ${data.carried === 1 ? "is" : "are"} waiting — they come back tomorrow, oldest first.`,
+        `${data.carried} more ${data.carried === 1 ? "is" : "are"} waiting — spread over the coming days, oldest first, never more than ${REVIEW_CAP} a day.`,
       );
     }
     if (data.gate) {

apps/api/src/gate.ts

@@ -5,7 +5,7 @@
  * The gate half is a topic-blind quiz — one unsolved optional problem per
  * topic scheduled this week (which is why daily drills only draw from
  * earlier weeks). The recap half is generated data, deliberately NOT a task
- * list: the week's solved problems are already scheduled by the +2 ladder,
+ * list: the week's solved problems are already scheduled by the +3/+7 ladder,
  * and re-assigning them on Saturday would be massed practice.
  *
  * Label is `review` (the retired Actions system owned `gate`). Creation is

apps/api/src/index.ts

@@ -19,9 +19,12 @@ import { type Mirror, projectMirror } from "./mirror.ts";
 import {
   CAMPAIGN_START,
   type LogOutcome,
+  type Stage,
   daysBetween,
+  dueToday,
   etDate,
   etHour,
+  getProblem,
   logAttempt,
   weekdayOf,
 } from "./srs.ts";
@@ -30,22 +33,20 @@ import { buildStats } from "./stats.ts";
 // ── shared side effects after a state write ──────────────────────
 
 /**
- * Mirror one logged attempt into GitHub: Project fields always; on a
+ * Mirror one logged attempt into GitHub: the Project's Target Date always; on a
  * first-ever pass also close the problem's sub-issue (comment first — repo
  * convention). Runs inside ctx.waitUntil; failures are warnings.
  */
 async function mirrorOutcome(env: Env, outcome: LogOutcome, source: string): Promise<void> {
   if (outcome.error || outcome.duplicate) return;
   const gh = github(env.GH_PAT, env.REPO);
-  const mirror: Mirror = projectMirror(gh, env.REPO.split("/")[0]!);
+  const mirror = projectMirror(gh, env.REPO.split("/")[0]!);
-  await mirror.setStage(outcome.issue, outcome.stage);
   await mirror.setTargetDate(outcome.issue, outcome.next_review);
-  if (outcome.first) await mirror.setFirstAttempt(outcome.issue, outcome.result);
   if (outcome.first && outcome.result === "pass") {
     try {
       await gh.closeIssue(
         outcome.issue,
-        `First attempt passed (${outcome.kind}, via ${source}) — entering the review ladder at +2. Logged by the SRS Worker.`,
+        `First attempt passed (${outcome.kind}, via ${source}) — entering the review ladder at +3. Logged by the SRS Worker.`,
       );
     } catch (err) {
       console.warn(`close #${outcome.issue}: ${err}`);
@@ -97,7 +98,7 @@ async function handleTap(request: Request, env: Env, ctx: ExecutionContext): Pro
   }
   ctx.waitUntil(mirrorOutcome(env, outcome, "email"));
   return page(
-    result === "pass" ? "Logged ✅" : "Logged — back to +2",
+    result === "pass" ? "Logged ✅" : "Logged — back to +3",
     outcomeLine(outcome),
   );
 }
@@ -200,6 +201,68 @@ async function adminAuthorized(request: Request, env: Env): Promise<boolean> {
   return timingSafeEqual(header.slice(7), env.LINK_KEY);
 }
 
+/**
+ * Solutions landing in `work/` are the third way a problem gets solved, after
+ * the digest tap and a /done comment. `close-solved` posts its whole
+ * implemented set here on every push to main, each entry tagged with the
+ * BUCKET the file sits in — 1 for the first solve, 3 and 7 for the blind
+ * re-solves the picker scaffolds. The bucket names the ladder rung the file
+ * settles, and logAttempt writes only when the problem is standing on that
+ * rung, so this is a total recompute like the reconcilers that call it: a
+ * re-run changes nothing, and a pushed re-solve advances +3 → +7 instead of
+ * being invisible.
+ *
+ * Closing the sub-issue stays with close-solved: it is the side that knows
+ * which files at which commit, so this path mirrors Project fields only.
+ * Charts read D1 live, so a push moves them within the 5-minute cache.
+ */
+const RUNG_OF_BUCKET: Record<number, Stage> = { 1: "new", 3: "+3", 7: "+7" };
+
+async function handleSolved(request: Request, env: Env, date: string): Promise<Response> {
+  const body: unknown = await request.json().catch(() => null);
+  const raw: unknown = body && typeof body === "object" && "solved" in body ? body.solved : null;
+  const shape = 'expected {"solved": [{"lc": <number>, "bucket": 1|3|7}, ...]}';
+  if (!Array.isArray(raw)) return new Response(shape, { status: 400 });
+  const entries: { lc: number; rung: Stage; bucket: number }[] = [];
+  for (const item of raw) {
+    if (!item || typeof item !== "object") return new Response(shape, { status: 400 });
+    const lc: unknown = "lc" in item ? item.lc : null;
+    const bucket: unknown = "bucket" in item ? item.bucket : null;
+    if (typeof lc !== "number" || !Number.isFinite(lc)) {
+      return new Response(`not an LC number: ${JSON.stringify(lc)}`, { status: 400 });
+    }
+    const rung = typeof bucket === "number" ? RUNG_OF_BUCKET[bucket] : undefined;
+    if (rung === undefined) return new Response(`not a work/ bucket: ${JSON.stringify(bucket)}`, { status: 400 });
+    entries.push({ lc, rung, bucket });
+  }
+  const dry = new URL(request.url).searchParams.get("dry") === "1";
+
+  const logged: string[] = [];
+  const skipped: string[] = [];
+  let mirror: Mirror | undefined;
+  for (const { lc, rung, bucket } of entries) {
+    if (dry) {
+      const p = await getProblem(env.DB, lc);
+      if (!p) skipped.push(`LC ${lc} is not in the curriculum`);
+      else if (p.stage !== rung) skipped.push(`LC ${lc}: work/${bucket} settles ${rung}, stage is ${p.stage}`);
+      else if (rung === "new") logged.push(`LC ${lc}: would enter the ladder at +3`);
+      else logged.push(`LC ${lc}: would pass ${rung} and move on`);
+      continue;
+    }
+    const outcome = await logAttempt(env.DB, { lc, date, result: "pass", source: "commit", rung });
+    if (outcome.error) skipped.push(outcome.error);
+    else if (outcome.duplicate) {
+      skipped.push(`LC ${lc}: work/${bucket} settles ${rung}, stage is ${outcome.stage}`);
+    } else {
+      logged.push(outcomeLine(outcome));
+      // One mirror for the batch: field IDs resolve once, not per problem.
+      mirror ??= projectMirror(github(env.GH_PAT, env.REPO), env.REPO.split("/")[0]!);
+      await mirror.setTargetDate(outcome.issue, outcome.next_review);
+    }
+  }
+  return Response.json({ date, logged, skipped, warnings: mirror?.warnings ?? [] });
+}
+
 async function handleAdmin(request: Request, env: Env, path: string): Promise<Response> {
   if (!(await adminAuthorized(request, env))) return new Response("unauthorized", { status: 401 });
   const url = new URL(request.url);
@@ -209,6 +272,7 @@ async function handleAdmin(request: Request, env: Env, path: string): Promise<Re
   if (path === "/admin/reconcile") {
     return Response.json(await reconcileCatalog(env.DB, gh()));
   }
+  if (path === "/admin/solved") return await handleSolved(request, env, date);
   if (path === "/admin/digest") {
     const report = await sendDigest(env, date, {
       dry: url.searchParams.get("dry") === "1",
@@ -222,6 +286,12 @@ async function handleAdmin(request: Request, env: Env, path: string): Promise<Re
   if (path === "/admin/review") {
     return Response.json(await createReviewIssue(env, gh(), date));
   }
+  // What is due on `date`, straight out of the ladder — the ONE answer to
+  // "which problems are open today", so the daily review issue and the digest
+  // cannot disagree. Read-only; the caller decides what to render.
+  if (path === "/admin/due") {
+    return Response.json(await dueToday(env.DB, date));
+  }
   return new Response("not found", { status: 404 });
 }
 

apps/api/src/mirror.ts

@@ -4,30 +4,26 @@
  * console warning and never blocks a state write. Only problem issues are
  * ever passed in, so topic rows' Target Date is never written.
  *
- * Field/option IDs are resolved by NAME per invocation (a Worker isolate is
+ * Target Date is the ONLY mirrored column. SRS stage and first-attempt result
- * short-lived; the two extra queries per mirror burst are irrelevant at this
+ * live exclusively in D1 — they are read from there (charts, digest, /api/stats)
- * volume and survive field re-creation).
+ * and duplicating them into Project single-selects bought nothing but drift and
+ * two extra writes per log. Do not re-add them here.
+ *
+ * Field IDs are resolved by NAME per invocation (a Worker isolate is
+ * short-lived; the extra query per mirror burst is irrelevant at this
+ * volume and survives field re-creation).
  */
 import type { GitHub } from "./github.ts";
 
 const PROJECT_TITLE = "Interview Prep";
 
-interface SelectField {
-  id: string;
-  options: Record<string, string>;
-}
-
 interface ProjectInfo {
   id: string;
   targetDate: string;
-  srsStage: SelectField;
-  firstAttempt: SelectField;
 }
 
 export interface Mirror {
   setTargetDate(issue: number, date: string | null): Promise<void>;
-  setStage(issue: number, stage: string): Promise<void>;
-  setFirstAttempt(issue: number, result: string): Promise<void>;
   warnings: string[];
 }
 
@@ -47,7 +43,6 @@ export function projectMirror(gh: GitHub, owner: string): Mirror {
               fields(first: 30) {
                 nodes {
                   ... on ProjectV2FieldCommon { id name dataType }
-                  ... on ProjectV2SingleSelectField { id name options { id name } }
                 }
               }
             }
@@ -62,7 +57,7 @@ export function projectMirror(gh: GitHub, owner: string): Mirror {
             id: string;
             title: string;
             fields: {
-              nodes: { id: string; name: string; options?: { id: string; name: string }[] }[];
+              nodes: { id: string; name: string }[];
             };
           }[];
         };
@@ -70,19 +65,9 @@ export function projectMirror(gh: GitHub, owner: string): Mirror {
     };
     const node = data.user.projectsV2.nodes.find((n) => n.title === PROJECT_TITLE);
     if (!node) throw new Error(`project "${PROJECT_TITLE}" not found for @${owner}`);
-    const select = (name: string): SelectField => {
-      const f = node.fields.nodes.find((n) => n.name === name);
-      if (!f?.options) throw new Error(`single-select field "${name}" missing`);
-      return { id: f.id, options: Object.fromEntries(f.options.map((o) => [o.name, o.id])) };
-    };
     const date = node.fields.nodes.find((n) => n.name === "Target Date");
     if (!date) throw new Error(`date field "Target Date" missing`);
-    info = {
+    info = { id: node.id, targetDate: date.id };
-      id: node.id,
-      targetDate: date.id,
-      srsStage: select("SRS Stage"),
-      firstAttempt: select("First Attempt"),
-    };
     return info;
   }
 
@@ -154,19 +139,5 @@ export function projectMirror(gh: GitHub, owner: string): Mirror {
           await setField(issue, project.targetDate, { date });
         }
       }),
-    setStage: (issue, stage) =>
-      attempt(`SRS Stage #${issue}`, async () => {
-        const project = await resolve();
-        const option = project.srsStage.options[stage];
-        if (!option) throw new Error(`no option "${stage}"`);
-        await setField(issue, project.srsStage.id, { singleSelectOptionId: option });
-      }),
-    setFirstAttempt: (issue, result) =>
-      attempt(`First Attempt #${issue}`, async () => {
-        const project = await resolve();
-        const option = project.firstAttempt.options[result];
-        if (!option) throw new Error(`no option "${result}"`);
-        await setField(issue, project.firstAttempt.id, { singleSelectOptionId: option });
-      }),
   };
 }

apps/api/src/srs.test.ts

@@ -1,11 +1,30 @@
 /**
- * DST-guard and date-math checks with fixed instants — the acceptance proof
+ * Acceptance proof for the two rules that cannot be eyeballed in production:
- * that the double crons fire exactly once at 8 AM ET (digest) and midnight
+ * the double crons fire exactly once at 8 AM ET (digest) and midnight Saturday
- * Saturday ET (review issue) on BOTH UTC offsets.
+ * ET (review issue) on BOTH UTC offsets, and NOTHING is ever scheduled on the
+ * Sunday rest day — which is the whole reason the ladder's windows are 3 and 7.
  */
 import { describe, expect, test } from "bun:test";
 
-import { addDays, campaignDay, campaignWeek, etDate, etHour, isoWeek, rng, sample, weekdayOf } from "./srs.ts";
+import {
+  INTERVAL,
+  STAGES,
+  WINDOWS,
+  addDays,
+  campaignDay,
+  campaignWeek,
+  etDate,
+  etHour,
+  isRestDay,
+  isoWeek,
+  rng,
+  sample,
+  weekdayOf,
+  workingDay,
+} from "./srs.ts";
+
+/** Every ET date of the campaign, plus the deferred-Hard tail. */
+const CALENDAR = Array.from({ length: 70 }, (_, i) => addDays("2026-08-17", i));
 
 describe("DST-proof cron guard", () => {
   test("digest fires only at ET hour 8 — EDT (UTC-4)", () => {
@@ -50,6 +69,69 @@ describe("date math (noon-UTC anchored)", () => {
   });
 });
 
+describe("the rest day", () => {
+  test("Sunday is the only rest day", () => {
+    expect(isRestDay("2026-08-30")).toBe(true); // Sunday
+    expect(isRestDay("2026-08-29")).toBe(false); // Saturday: gate day, still work
+    expect(isRestDay("2026-08-31")).toBe(false);
+  });
+
+  test("workingDay never returns a Sunday, from any day and any offset", () => {
+    for (const date of CALENDAR) {
+      for (let offset = 0; offset < 10; offset++) {
+        expect(isRestDay(workingDay(date, offset))).toBe(false);
+      }
+    }
+  });
+
+  test("workingDay(date) leaves a working day alone and slides Sunday to Monday", () => {
+    expect(workingDay("2026-09-04")).toBe("2026-09-04"); // Friday
+    expect(workingDay("2026-09-05")).toBe("2026-09-05"); // Saturday
+    expect(workingDay("2026-09-06")).toBe("2026-09-07"); // Sunday → Monday
+  });
+
+  test("offsets count working days, so a spill skips the rest day", () => {
+    // Levelling from Saturday: tomorrow is Sunday, so the spill starts Monday.
+    expect(workingDay("2026-09-05", 1)).toBe("2026-09-07");
+    expect(workingDay("2026-09-05", 2)).toBe("2026-09-08");
+    // Two deferred Hards per working day from a Monday.
+    expect(workingDay("2026-09-28", 5)).toBe("2026-10-03"); // Saturday
+    expect(workingDay("2026-09-28", 6)).toBe("2026-10-05"); // Sunday skipped
+  });
+
+  test("every ladder interval lands on a working day, from every learning day", () => {
+    for (const date of CALENDAR) {
+      if (isRestDay(date)) continue;
+      for (const days of WINDOWS) {
+        const review = workingDay(addDays(date, days));
+        expect(isRestDay(review)).toBe(false);
+        // Never earlier than the interval: a review may slip, never shorten.
+        expect(review >= addDays(date, days)).toBe(true);
+      }
+    }
+  });
+
+  test("only Thursday's +3 needs the slide", () => {
+    const slid = CALENDAR.filter(
+      (date) => !isRestDay(date) && workingDay(addDays(date, 3)) !== addDays(date, 3),
+    );
+    expect(new Set(slid.map(weekdayOf))).toEqual(new Set([4])); // Thursday only
+    for (const date of CALENDAR) {
+      if (isRestDay(date)) continue;
+      expect(workingDay(addDays(date, 7))).toBe(addDays(date, 7)); // +7 keeps the weekday
+    }
+  });
+});
+
+describe("the ladder", () => {
+  test("two rungs, named after the windows", () => {
+    expect(STAGES).toEqual(["new", "+3", "+7", "retired"]);
+    expect(WINDOWS.map((w) => INTERVAL[`+${w}`])).toEqual([...WINDOWS]);
+    // Every non-terminal stage has an interval, and only those.
+    expect(Object.keys(INTERVAL).sort()).toEqual(STAGES.slice(1, -1).sort());
+  });
+});
+
 describe("deterministic sampling", () => {
   test("same seed, same picks", () => {
     const pool = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];

apps/api/src/srs.ts

@@ -1,12 +1,19 @@
 /**
- * SRS domain: ET dates, the interval ladder, deterministic sampling, and the
+ * SRS domain: ET dates, the work week, the interval ladder, deterministic
- * one write path for attempts — ported from scripts/srs.ts, re-homed on D1.
+ * sampling, and the one write path for attempts.
  *
  * D1 is the single source of truth. The stage names the review a problem must
- * pass NEXT (`+2` = due 2 days after last clean solve). Passing advances
+ * pass NEXT (`+3` = due 3 working days after the last clean solve). Passing
- * new → +2 → +5 → +10 → retired; any failure resets to +2. A problem's
+ * advances new → +3 → +7 → retired; any failure resets to +3. A problem's
- * FIRST-ever log enters the ladder at +2 regardless of result: a pass earns
+ * FIRST-ever log enters the ladder at +3 regardless of result: a pass earns a
- * a +2 review, a fail must be re-solved just as soon.
+ * 3-day review, a fail must be re-solved just as soon. Two rungs, 3 and 7 —
+ * the same numbers as the `work/3` and `work/7` buckets a re-solve is
+ * scaffolded into, and as the review-issue windows in
+ * apps/cli/spaced-repetition.ts.
+ *
+ * Sunday is off, structurally: every scheduled date comes out of
+ * workingDay(), which never returns one. Nothing "falls on" the rest day and
+ * gets swallowed or carried — it is simply never booked there.
  *
  * All dates are America/New_York calendar strings (YYYY-MM-DD); arithmetic is
  * anchored at noon UTC so DST edges cannot shift a date. Never raw Date math.
@@ -56,6 +63,37 @@ export function weekdayOf(date: string): number {
   return atNoon(date).getUTCDay();
 }
 
+// ── the work week ────────────────────────────────────────────────
+
+/**
+ * Sunday, the one day the campaign never schedules: topics run Mon–Fri
+ * (data/schedule.json), the gate is Saturday, and the review windows below are
+ * picked so a solve comes back on a working day.
+ */
+const REST_DAY = 0;
+
+export function isRestDay(date: string): boolean {
+  return weekdayOf(date) === REST_DAY;
+}
+
+/**
+ * The `offset`-th working day counting from `from` (0 = `from` itself), with
+ * Sundays skipped — the ONE place a scheduled date is minted.
+ *
+ * Work may slide later, never earlier: pulling a review back to Saturday would
+ * shorten the very interval it exists to test, so a Sunday landing becomes
+ * Monday. With the +3/+7 ladder that only ever happens to a Thursday solve's
+ * 3-day review; +7 lands on the solve's own weekday, which is never a Sunday.
+ */
+export function workingDay(from: string, offset = 0): string {
+  let cursor = isRestDay(from) ? addDays(from, 1) : from;
+  for (let i = 0; i < offset; i++) {
+    cursor = addDays(cursor, 1);
+    if (isRestDay(cursor)) cursor = addDays(cursor, 1);
+  }
+  return cursor;
+}
+
 export function campaignDay(date: string): number {
   return daysBetween(CAMPAIGN_START, date) + 1;
 }
@@ -126,7 +164,21 @@ export function sample<T>(pool: T[], n: number, random: () => number): T[] {
 
 // ── rows ─────────────────────────────────────────────────────────
 
-export type Stage = "new" | "+2" | "+5" | "+10" | "retired";
+/**
+ * Review windows in days. One vocabulary for the whole campaign: these are the
+ * ladder rungs, the `work/<n>` buckets the picker scaffolds into, and the
+ * windows the `Spaced Repetition — <date>` issues are built from.
+ *
+ * 3 and 7 keep the rest day free. +7 returns a solve to its own weekday, and
+ * of the five learning weekdays only Thursday's +3 touches a Sunday — which
+ * workingDay() slides to Monday.
+ */
+export const WINDOWS = [3, 7] as const;
+export type Window = (typeof WINDOWS)[number];
+
+export type Stage = "new" | `+${Window}` | "retired";
+/** Chart / stats order, low to high. */
+export const STAGES: Stage[] = ["new", "+3", "+7", "retired"];
 export type Result = "pass" | "fail";
 export type Kind = "first" | "review" | "drill" | "gate";
 
@@ -142,8 +194,8 @@ export interface ProblemRow {
   defer_until: string | null;
 }
 
-export const INTERVAL: Record<string, number> = { "+2": 2, "+5": 5, "+10": 10 };
+export const INTERVAL: Record<string, number> = { "+3": 3, "+7": 7 };
-const NEXT_STAGE: Record<string, Stage> = { new: "+2", "+2": "+5", "+5": "+10", "+10": "retired" };
+const NEXT_STAGE: Record<string, Stage> = { new: "+3", "+3": "+7", "+7": "retired" };
 
 // ── queries ──────────────────────────────────────────────────────
 
@@ -151,20 +203,111 @@ export async function getProblem(db: D1Database, lc: number): Promise<ProblemRow
   return db.prepare("SELECT * FROM problems WHERE lc_number = ?").bind(lc).first<ProblemRow>();
 }
 
+/**
+ * What "due" means, in one place: not retired, scheduled on/before ?1, and
+ * past its deferral if it has one. Every caller that asks "what is open on
+ * this day" — the digest, the review issue, the docs queue chart — shares
+ * this clause so they cannot answer differently.
+ */
+export const DUE_WHERE = `stage != 'retired' AND next_review IS NOT NULL AND next_review <= ?1
+    AND (defer_until IS NULL OR defer_until <= ?1)`;
+
 /** Reviews due on/before `date`, oldest first — the overflow carry order. */
 export async function dueReviews(db: D1Database, date: string): Promise<ProblemRow[]> {
   const { results } = await db
-    .prepare(
+    .prepare(`SELECT * FROM problems WHERE ${DUE_WHERE} ORDER BY next_review, lc_number`)
-      `SELECT * FROM problems
-       WHERE stage != 'retired' AND next_review IS NOT NULL AND next_review <= ?1
-         AND (defer_until IS NULL OR defer_until <= ?1)
-       ORDER BY next_review, lc_number`,
-    )
     .bind(date)
     .all<ProblemRow>();
   return results;
 }
 
+/** One problem the ladder wants re-solved today. */
+export interface DueRow {
+  lc: number;
+  issue: number;
+  title: string;
+  difficulty: string;
+  /** The rung being settled: also the `work/<n>` bucket the re-solve goes in. */
+  stage: Stage;
+  bucket: number;
+  /** Scheduled day; earlier than `date` when a day was missed. */
+  due: string;
+  /** Days late (0 = due today), so a renderer can say so. */
+  late: number;
+  /** Last logged attempt, and how long ago — the "last seen" line. */
+  last_seen: string | null;
+  days_since: number | null;
+}
+
+/**
+ * Everything the ladder wants re-solved on `date`, oldest first.
+ *
+ * The read side of "which problems are open today": the same rows the digest
+ * mails, shaped for whoever renders them (the daily Spaced Repetition issue).
+ * Nothing here writes, so it is safe to call repeatedly, and there is no
+ * second schedule to drift — D1's ladder is the schedule.
+ */
+export async function dueToday(db: D1Database, date: string): Promise<{ date: string; due: DueRow[] }> {
+  const { results } = await db
+    .prepare(
+      `SELECT lc_number, issue, title, difficulty, stage, next_review,
+              (SELECT MAX(a.date) FROM attempts a WHERE a.lc_number = problems.lc_number) AS last_seen
+         FROM problems WHERE ${DUE_WHERE} ORDER BY next_review, lc_number`,
+    )
+    .bind(date)
+    .all<{
+      lc_number: number;
+      issue: number;
+      title: string;
+      difficulty: string;
+      stage: Stage;
+      next_review: string;
+      last_seen: string | null;
+    }>();
+  return {
+    date,
+    due: results.map((r) => ({
+      lc: r.lc_number,
+      issue: r.issue,
+      title: r.title,
+      difficulty: r.difficulty,
+      stage: r.stage,
+      // "+3" -> 3: the rung's number IS its work/ bucket.
+      bucket: Number(r.stage.slice(1)),
+      due: r.next_review,
+      late: daysBetween(r.next_review, date),
+      last_seen: r.last_seen,
+      days_since: r.last_seen === null ? null : daysBetween(r.last_seen, date),
+    })),
+  };
+}
+
+/** Reviews surfaced per day; the digest levels everything past this forward. */
+export const REVIEW_CAP = 3;
+
+/**
+ * Load-level an overloaded review queue: everything due beyond today's
+ * REVIEW_CAP is pushed to a concrete future WORKING day — at most REVIEW_CAP
+ * per day, oldest first — instead of piling up as "due today". Runs every
+ * digest morning, so a future day that grows past the cap (spill plus newly
+ * maturing reviews) is simply re-levelled when it arrives. Idempotent within
+ * a date: after one pass at most REVIEW_CAP problems remain due today, so a
+ * second pass moves nothing. The spill starts tomorrow, or Monday when
+ * tomorrow is the rest day.
+ */
+export async function levelReviews(db: D1Database, date: string): Promise<number> {
+  const overflow = (await dueReviews(db, date)).slice(REVIEW_CAP);
+  if (overflow.length === 0) return 0;
+  await db.batch(
+    overflow.map((p, i) =>
+      db
+        .prepare("UPDATE problems SET next_review = ? WHERE lc_number = ?")
+        .bind(workingDay(addDays(date, 1), Math.floor(i / REVIEW_CAP)), p.lc_number),
+    ),
+  );
+  return overflow.length;
+}
+
 /**
  * Blind drills: unsolved optional problems from topics ALREADY LEARNED —
  * scheduled in an earlier week (the current week's optional pool is reserved
@@ -242,16 +385,32 @@ export interface LogOutcome {
 
 /**
  * Record an attempt and move the ladder. Ladder semantics live here and only
- * here — email one-taps, webhook /done lines, and gate scoring all converge.
+ * here — email one-taps, webhook /done lines, gate scoring, and solutions
+ * landing in work/ all converge.
  *
  * Email idempotency comes from the partial unique index on
  * (lc_number, date, kind) WHERE source='email': a replayed link inserts
  * nothing and must not touch the ladder. Webhook corrections (pass then fail
  * on the same day) remain legal — every webhook attempt appends.
+ *
+ * Commit idempotency needs no index either. A commit names the rung the file
+ * it landed in settles — `work/1` settles `new`, `work/3` settles `+3`,
+ * `work/7` settles `+7` — and the stage check below writes only when the
+ * ladder is actually standing on that rung. So re-pushing a solution, or the
+ * reconciler re-sending its whole implemented set on every push, moves
+ * nothing: the rung it names has already been left behind.
  */
 export async function logAttempt(
   db: D1Database,
-  opts: { lc: number; date: string; result: Result; source: "email" | "webhook"; gate?: boolean },
+  opts: {
+    lc: number;
+    date: string;
+    result: Result;
+    source: "email" | "webhook" | "commit";
+    /** Commit only: the stage this file settles. Default `new` = first solve. */
+    rung?: Stage;
+    gate?: boolean;
+  },
 ): Promise<LogOutcome> {
   const p = await getProblem(db, opts.lc);
   const nothing: LogOutcome = {
@@ -266,6 +425,21 @@ export async function logAttempt(
     duplicate: false,
   };
   if (!p) return { ...nothing, error: `LC ${opts.lc} is not in the curriculum` };
+  // A commit reports a file, not an event: it may only settle the rung that
+  // file's bucket IS. Any other stage means the push is old news (the ladder
+  // already moved past it) or premature — no write either way, and a retired
+  // problem can never be woken. Fresh reviews otherwise come from the digest
+  // tap, a /done comment, or a gate.
+  if (opts.source === "commit" && p.stage !== (opts.rung ?? "new")) {
+    return {
+      ...nothing,
+      title: p.title,
+      stage: p.stage,
+      next_review: p.next_review,
+      issue: p.issue,
+      duplicate: true,
+    };
+  }
   if (p.stage === "retired") {
     return { ...nothing, title: p.title, issue: p.issue, error: `LC ${opts.lc} is already retired` };
   }
@@ -288,16 +462,18 @@ export async function logAttempt(
     return { ...nothing, title: p.title, kind, stage: p.stage, next_review: p.next_review, issue: p.issue, duplicate: true };
   }
 
-  // Ladder move. First-ever logs enter at +2 for pass AND fail.
+  // Ladder move. First-ever logs enter at +3 for pass AND fail.
   let stage: Stage;
   if (first) {
-    stage = "+2";
+    stage = "+3";
   } else if (opts.result === "pass") {
     stage = NEXT_STAGE[p.stage] ?? "retired";
   } else {
-    stage = "+2";
+    stage = "+3";
   }
-  const next = stage === "retired" ? null : addDays(opts.date, INTERVAL[stage]!);
+  // workingDay(), not addDays(): a Thursday solve's +3 would land on the rest
+  // day, and it takes Monday instead.
+  const next = stage === "retired" ? null : workingDay(addDays(opts.date, INTERVAL[stage]!));
 
   const writes = [
     db.prepare(

apps/api/src/stats.ts

@@ -7,9 +7,12 @@
 import {
   CAMPAIGN_DAYS,
   CAMPAIGN_START,
+  DUE_WHERE,
   addDays,
   campaignDay,
   campaignWeek,
+  isoWeek,
+  STAGES,
   streak,
 } from "./srs.ts";
 
@@ -58,23 +61,25 @@ export async function buildStats(db: D1Database, today: string): Promise<object>
   const { results: ladderRows } = await db
     .prepare("SELECT stage, COUNT(*) AS n FROM problems GROUP BY stage")
     .all<{ stage: string; n: number }>();
-  const ladder: Record<string, number> = { new: 0, "+2": 0, "+5": 0, "+10": 0, retired: 0 };
+  // Every rung is present even at zero: the page's bar list is this object.
+  const ladder: Record<string, number> = Object.fromEntries(STAGES.map((s) => [s, 0]));
   for (const row of ladderRows) ladder[row.stage] = row.n;
 
-  const { results: gates } = await db
+  // gates rows are keyed by ISO week (that's the digest/gate contract), but
+  // the page speaks campaign weeks. The campaign never crosses a year
+  // boundary, so a plain offset converts safely.
+  const isoWeekOffset = isoWeek(CAMPAIGN_START) - 1;
+  const { results: gateRows } = await db
     .prepare("SELECT week, issue, pass_rate, closed_on FROM gates ORDER BY week")
     .all<{ week: number; issue: number | null; pass_rate: number | null; closed_on: string | null }>();
+  const gates = gateRows.map((g) => ({ ...g, week: g.week - isoWeekOffset }));
 
   // Review-queue depth for the next 14 days: everything due by that day.
   const queue: { date: string; due: number }[] = [];
   for (let i = 0; i < 14; i++) {
     const date = addDays(today, i);
     const row = await db
-      .prepare(
+      .prepare(`SELECT COUNT(*) AS n FROM problems WHERE ${DUE_WHERE}`)
-        `SELECT COUNT(*) AS n FROM problems
-         WHERE stage != 'retired' AND next_review IS NOT NULL AND next_review <= ?1
-           AND (defer_until IS NULL OR defer_until <= ?1)`,
-      )
       .bind(date)
       .first<{ n: number }>();
     queue.push({ date, due: row?.n ?? 0 });

apps/api/wrangler.jsonc

@@ -15,7 +15,7 @@
     { "binding": "DB", "database_name": "srs", "database_id": "2ee2c34a-c2e2-4ebb-934e-c9e7dc8aa4f1" }
   ],
 
-  // Sender domain prdlk.com is onboarded to Email Sending; the binding is
+  // Sender domain prdlk.com is onboarded to Email Service; the binding is
   // restricted to the one verified destination inbox.
   "send_email": [
     { "name": "EMAIL", "allowed_destination_addresses": ["prnk28@gmail.com"] }

apps/cli/close-solved.ts

@@ -1,6 +1,7 @@
 #!/usr/bin/env bun
 /**
- * Close the GitHub issue for every LeetCode problem actually solved under work/.
+ * Close the GitHub issue for every LeetCode problem actually solved under work/,
+ * then report the solved set to the SRS Worker so D1 agrees.
  *
  * Reconciles state instead of reacting to a push diff: any `problem`-labelled
  * issue whose LC number has an *implemented* solution file in work/ gets
@@ -9,75 +10,27 @@
  *
  * `bun run pick` scaffolds a statement header plus an empty function body, so
  * file existence alone means nothing — a stub must not close its issue. See
- * isImplemented().
+ * isImplemented() in source.ts.
  *
- *   bun apps/cli/close-solved.ts            # close matches
+ *   bun apps/cli/close-solved.ts            # close matches, log them in D1
  *   bun apps/cli/close-solved.ts --dry-run  # report only, touch nothing
  *
  * Auth: GH_TOKEN / GITHUB_TOKEN, else falls back to `gh auth token`.
+ *       SRS_ADMIN_KEY for the D1 push (unset = skip it); SRS_API overrides
+ *       the Worker URL for local `wrangler dev` runs.
  */
-import { basename, join } from "node:path";
+import { join } from "node:path";
 
 import { github } from "./github.ts";
 import { markdownTable, printTable, writeStepSummary } from "./report.ts";
-
+import { isImplemented } from "./source.ts";
-const ROOT = join(import.meta.dir, "..", "..");
+import { WORK, parseWorkPath, type Bucket } from "./work.ts";
-const WORK = join(ROOT, "work");
 
 const DRY =
   process.argv.includes("--dry-run") ||
   process.env.DRY_RUN === "1" ||
   process.env.DRY_RUN === "true";
 
-// ── is the file a real solution or just a scaffolded stub? ────────
-
-/** Placeholder bodies that leetcode-cli / a human leaves behind. */
-const PLACEHOLDERS: Record<string, true> = { pass: true, "...": true, TODO: true };
-
-/**
- * Decide whether a work/ file contains an implementation.
- *
- * The header comment is dropped the same way sync.ts splitSource() does it
- * (duplicated rather than imported, because sync.ts runs its whole pipeline on
- * import). Comments must go before any brace analysis: the scaffold's JSDoc
- * carries `@param {number[]}`, whose braces would otherwise read as a body.
- *
- * A brace-language file counts as implemented when at least one *innermost*
- * brace pair holds real content. That distinguishes a bare stub
- * (`function(nums) {}`) and a class-shaped design stub (every method body
- * empty) from any genuine solution, whose innermost block always has code.
- */
-function isImplemented(src: string, lang: "js" | "py"): boolean {
-  if (lang === "py") {
-    const open = src.indexOf('"""');
-    const close = src.indexOf('"""', open + 3);
-    const code = open === -1 || close === -1 ? src : src.slice(close + 3);
-    for (const raw of code.split("\n")) {
-      const line = raw.replace(/#.*$/, "").trim();
-      if (!line || PLACEHOLDERS[line]) continue;
-      if (/^(?:@|def\s|class\s)/.test(line)) continue;
-      return true; // a statement inside some def body
-    }
-    return false;
-  }
-
-  const headerEnd = src.indexOf("*/");
-  const body = headerEnd === -1 ? src : src.slice(headerEnd + 2);
-  const code = body.replace(/\/\*[\s\S]*?\*\//g, " ").replace(/\/\/.*$/gm, " ");
-
-  let innermost = -1;
-  for (let i = 0; i < code.length; i++) {
-    if (code[i] === "{") {
-      innermost = i;
-    } else if (code[i] === "}" && innermost !== -1) {
-      const inner = code.slice(innermost + 1, i).replace(/[\s;]/g, "");
-      if (inner && !PLACEHOLDERS[inner]) return true;
-      innermost = -1; // measured; the enclosing pair is not innermost
-    }
-  }
-  return false;
-}
-
 // ── repo + auth ──────────────────────────────────────────────────
 
 const gh = await github();
@@ -86,27 +39,27 @@ const gh = await github();
 
 interface WorkEntry {
   files: string[];
+  /** Any bucket implemented — this is what closes the problem issue. */
   implemented: boolean;
+  /** Buckets holding a real solution: 1 = first solve, 3/7 = the re-solves. */
+  solved: Set<Bucket>;
 }
 
-/** LC number -> solution files (a problem may have both js and py). */
+/** LC number -> its solution files across every bucket (js and py both count). */
 const work = new Map<number, WorkEntry>();
 for await (const rel of new Bun.Glob("**/*.{js,py}").scan(WORK)) {
-  const m = basename(rel).match(/^(\d+)\.(.+)\.(?:js|py)$/);
+  const file = parseWorkPath(rel);
-  if (!m) {
+  if (!file) {
-    console.warn(`skip (unrecognized name): work/${rel}`);
+    console.warn(`skip (off-layout): work/${rel}`);
     continue;
   }
-  const num = Number(m[1]);
   const src = await Bun.file(join(WORK, rel)).text();
   const implemented = isImplemented(src, rel.endsWith(".py") ? "py" : "js");
-  const entry = work.get(num);
+  const entry = work.get(file.lc) ?? { files: [], implemented: false, solved: new Set<Bucket>() };
-  if (entry) {
+  entry.files.push(`work/${rel}`);
-    entry.files.push(`work/${rel}`);
+  entry.implemented ||= implemented;
-    entry.implemented ||= implemented;
+  if (implemented) entry.solved.add(file.bucket);
-  } else {
+  work.set(file.lc, entry);
-    work.set(num, { files: [`work/${rel}`], implemented });
-  }
 }
 
 // ── open problem issues ──────────────────────────────────────────
@@ -193,24 +146,85 @@ for (const num of [...work.keys()].sort((a, b) => a - b)) {
   closed++;
 }
 
+// ── push the solved set into D1 ───────────────────────────────────
+
+// Closing an issue is invisible to the Worker: its catalog reconcile reads
+// GitHub for titles, labels and milestones and never looks at issue state,
+// and D1's SRS columns only ever move through logAttempt(). So a solution
+// pushed here — rather than tapped in the digest email — has to be reported,
+// or the charts, the digest's "already solved" ticks, and the drill/gate
+// pools all keep treating it as untouched.
+//
+// Each entry carries the BUCKET the file sits in, which is the rung it
+// settles: work/1 is the first solve, work/3 the 3-day review, work/7 the
+// 7-day one. That is what makes a pushed re-solve advance the ladder instead
+// of vanishing — and the Worker writes only when a problem is standing on the
+// rung named, so the whole implemented set can go over on every push (a total
+// recompute that backfills whatever earlier runs missed) and re-runs write
+// nothing.
+const SRS_API = process.env.SRS_API ?? "https://srs-api.prdlk.workers.dev";
+const solved = [...work.entries()]
+  .flatMap(([lc, entry]) => [...entry.solved].sort().map((bucket) => ({ lc, bucket })))
+  .sort((a, b) => a.lc - b.lc || a.bucket - b.bucket);
+
+let syncNote: string;
+let syncFailed = false;
+if (!process.env.SRS_ADMIN_KEY) {
+  syncNote = "SRS_ADMIN_KEY unset — D1 not touched";
+} else if (solved.length === 0) {
+  syncNote = "nothing implemented — D1 not touched";
+} else {
+  try {
+    const res = await fetch(`${SRS_API}/admin/solved${DRY ? "?dry=1" : ""}`, {
+      method: "POST",
+      headers: {
+        authorization: `Bearer ${process.env.SRS_ADMIN_KEY}`,
+        "content-type": "application/json",
+      },
+      body: JSON.stringify({ solved }),
+    });
+    if (!res.ok) throw new Error(`${res.status} ${await res.text()}`);
+    // Narrow the report payload instead of casting it; a shape change should
+    // read as "logged nothing", not throw inside the reconciler.
+    const payload: unknown = await res.json();
+    const fields = payload && typeof payload === "object" ? payload : {};
+    const strings = (value: unknown): string[] => (Array.isArray(value) ? value.map(String) : []);
+    const logged = strings("logged" in fields ? fields.logged : null);
+    const skipped = strings("skipped" in fields ? fields.skipped : null);
+    syncNote =
+      `${DRY ? "would log" : "logged"} ${logged.length} of ${solved.length} ` +
+      `(${skipped.length} already on the ladder or off-curriculum)`;
+    for (const line of logged) console.log(`  d1: ${line}`);
+  } catch (err) {
+    // The closes above already landed; surface the failure instead of
+    // letting D1 drift silently until the next push.
+    syncFailed = true;
+    syncNote = `D1 push FAILED: ${err instanceof Error ? err.message : String(err)}`;
+  }
+}
+
 // ── report ───────────────────────────────────────────────────────
 
 const rows = [["lc", "issue", "set", "status"], ...report];
 printTable(rows);
 
-const implemented = [...work.values()].filter((e) => e.implemented).length;
 const actionable = report.filter((r) => r[3] !== "no open issue");
 console.log(
-  `\n${work.size} in work/ · ${implemented} implemented · ` +
+  `\n${work.size} problems in work/ · ${solved.length} solved files across buckets · ` +
     `${actionable.length} matched an open issue · ` +
-    `${DRY ? `would close ${actionable.filter((r) => r[3] === "would close").length}` : `closed ${closed}`}`,
+    `${DRY ? `would close ${actionable.filter((r) => r[3] === "would close").length}` : `closed ${closed}`}` +
+    `\nd1: ${syncNote}`,
 );
 
 await writeStepSummary(
   `### close-solved${DRY ? " (dry run)" : ""}\n\n` +
-    `${work.size} files in \`work/\`, ${implemented} implemented, ` +
+    `${work.size} problems in \`work/\`, ${solved.length} solved files across buckets, ` +
     `${actionable.length} matched an open issue.\n\n` +
     (actionable.length
       ? `${markdownTable([rows[0]!, ...actionable])}\n`
-      : "Nothing to close.\n"),
+      : "Nothing to close.\n") +
+    `\nD1: ${syncNote}\n`,
 );
+
+// Non-zero only for the D1 push: the closes are already reported above.
+if (syncFailed) process.exitCode = 1;

apps/cli/db.ts

@@ -0,0 +1,235 @@
+/**
+ * Local LeetCode problem cache backed by SQLite at
+ * ~/.local/share/leetcode/data.db (XDG_DATA_HOME honored).
+ *
+ * One `problems` table, two freshness rules:
+ *   - the full problem index (id / title / slug / difficulty / paid flag) is
+ *     refreshed from leetcode.com at most once per 24h (`meta.index_fetched_at`);
+ *   - descriptions (HTML from GraphQL `question.content`) are fetched once per
+ *     slug and kept forever. Only the campaign problems linked from README.md
+ *     are ever fetched, and paid-only problems are skipped because GraphQL
+ *     returns null content for them.
+ *
+ * A `solutions` table tracks the lifecycle of each work/ file by LC number:
+ * `created_at` (backfilled from the file's birthtime on every picker run),
+ * `last_tested` and `last_submitted` (stamped on exit 0 of leetcode-cli).
+ * The test picker sorts by last_tested, the submit picker by created_at, and
+ * submit hides anything with a last_submitted.
+ *
+ * Library: side-effect-free on import — nothing is opened or fetched until
+ * problemDb() is called. Index upserts never touch the description column, so
+ * a daily refresh cannot evict cached statements.
+ */
+import { Database } from "bun:sqlite";
+import { mkdirSync } from "node:fs";
+import { homedir } from "node:os";
+import { dirname, join } from "node:path";
+
+export interface Problem {
+  id: number;
+  title: string;
+  slug: string;
+  difficulty: "Easy" | "Medium" | "Hard";
+  paidOnly: boolean;
+}
+
+/** Lifecycle of one work/ solution, keyed by LC number. ISO timestamps. */
+export interface SolutionActivity {
+  createdAt: string;
+  lastTested: string | null;
+  lastSubmitted: string | null;
+}
+
+const DIFFICULTY = ["", "Easy", "Medium", "Hard"] as const;
+const INDEX_TTL_MS = 24 * 60 * 60 * 1000;
+
+export const DB_PATH = join(
+  process.env.XDG_DATA_HOME ?? join(homedir(), ".local", "share"),
+  "leetcode",
+  "data.db",
+);
+
+// ── README parsing ───────────────────────────────────────────────
+
+/** Campaign problem slugs linked from README.md, in order, deduplicated. */
+export function readmeSlugs(markdown: string): string[] {
+  const slugs = new Set<string>();
+  for (const m of markdown.matchAll(/https:\/\/leetcode\.com\/problems\/([\w-]+)\//g)) {
+    slugs.add(m[1]!);
+  }
+  return [...slugs];
+}
+
+// ── remote fetches ───────────────────────────────────────────────
+
+async function fetchIndex(): Promise<Problem[]> {
+  const res = await fetch("https://leetcode.com/api/problems/all/", {
+    headers: { "user-agent": "Mozilla/5.0" },
+  });
+  if (!res.ok) throw new Error(`GET /api/problems/all -> ${res.status} ${res.statusText}`);
+  const data = (await res.json()) as {
+    stat_status_pairs: Array<{
+      stat: {
+        frontend_question_id: number;
+        question__title: string;
+        question__title_slug: string;
+      };
+      difficulty: { level: 1 | 2 | 3 };
+      paid_only: boolean;
+    }>;
+  };
+  return data.stat_status_pairs
+    .map((p) => ({
+      id: p.stat.frontend_question_id,
+      title: p.stat.question__title,
+      slug: p.stat.question__title_slug,
+      difficulty: DIFFICULTY[p.difficulty.level] as Problem["difficulty"],
+      paidOnly: p.paid_only,
+    }))
+    .sort((a, b) => a.id - b.id);
+}
+
+/** HTML problem statement, or null when LeetCode withholds it (paid-only). */
+export async function fetchDescription(slug: string): Promise<string | null> {
+  const res = await fetch("https://leetcode.com/graphql", {
+    method: "POST",
+    headers: {
+      "content-type": "application/json",
+      "user-agent": "Mozilla/5.0",
+      referer: `https://leetcode.com/problems/${slug}/`,
+    },
+    body: JSON.stringify({
+      query: "query questionContent($titleSlug: String!) { question(titleSlug: $titleSlug) { content } }",
+      variables: { titleSlug: slug },
+    }),
+  });
+  if (!res.ok) throw new Error(`POST /graphql (${slug}) -> ${res.status} ${res.statusText}`);
+  const data = (await res.json()) as { data?: { question?: { content?: string | null } | null } };
+  return data.data?.question?.content ?? null;
+}
+
+// ── the cache ────────────────────────────────────────────────────
+
+export function problemDb(path = DB_PATH) {
+  mkdirSync(dirname(path), { recursive: true });
+  const db = new Database(path);
+  db.exec(`
+    CREATE TABLE IF NOT EXISTS problems (
+      id          INTEGER PRIMARY KEY,
+      title       TEXT NOT NULL,
+      slug        TEXT NOT NULL UNIQUE,
+      difficulty  TEXT NOT NULL,
+      paid_only   INTEGER NOT NULL,
+      description TEXT
+    );
+    CREATE TABLE IF NOT EXISTS solutions (
+      id             INTEGER PRIMARY KEY,
+      created_at     TEXT NOT NULL,
+      last_tested    TEXT,
+      last_submitted TEXT
+    );
+    DROP TABLE IF EXISTS submissions;
+    CREATE TABLE IF NOT EXISTS meta (
+      key   TEXT PRIMARY KEY,
+      value TEXT NOT NULL
+    );
+  `);
+
+  const getMeta = db.query<{ value: string }, [string]>("SELECT value FROM meta WHERE key = ?1");
+  const setMeta = db.query<never, [string, string]>(
+    "INSERT INTO meta (key, value) VALUES (?1, ?2) ON CONFLICT(key) DO UPDATE SET value = excluded.value",
+  );
+  const upsert = db.query<never, [number, string, string, string, number]>(
+    `INSERT INTO problems (id, title, slug, difficulty, paid_only)
+     VALUES (?1, ?2, ?3, ?4, ?5)
+     ON CONFLICT(id) DO UPDATE SET
+       title = excluded.title, slug = excluded.slug,
+       difficulty = excluded.difficulty, paid_only = excluded.paid_only`,
+  );
+  const descState = db.query<{ paid_only: number; described: number }, [string]>(
+    "SELECT paid_only, description IS NOT NULL AS described FROM problems WHERE slug = ?1",
+  );
+
+  return {
+    path,
+
+    /** True when the index has never been fetched or is older than 24h. */
+    indexStale(): boolean {
+      const row = getMeta.get("index_fetched_at");
+      return !row || Date.now() - Number(row.value) > INDEX_TTL_MS;
+    },
+
+    /** Pull the full index from leetcode.com and upsert it. Returns the count. */
+    async refreshIndex(): Promise<number> {
+      const problems = await fetchIndex();
+      db.transaction(() => {
+        for (const p of problems) upsert.run(p.id, p.title, p.slug, p.difficulty, p.paidOnly ? 1 : 0);
+        setMeta.run("index_fetched_at", String(Date.now()));
+      })();
+      return problems.length;
+    },
+
+    /** Every cached problem, ordered by LC number. */
+    all(): Problem[] {
+      const rows = db
+        .query<{ id: number; title: string; slug: string; difficulty: string; paid_only: number }, []>(
+          "SELECT id, title, slug, difficulty, paid_only FROM problems ORDER BY id",
+        )
+        .all();
+      return rows.map((r) => ({
+        id: r.id,
+        title: r.title,
+        slug: r.slug,
+        difficulty: r.difficulty as Problem["difficulty"],
+        paidOnly: r.paid_only === 1,
+      }));
+    },
+
+    /** Free (non-premium) slugs among `slugs` with no cached description yet. */
+    missingDescriptions(slugs: string[]): string[] {
+      return slugs.filter((slug) => {
+        const row = descState.get(slug);
+        return row !== null && !row.paid_only && !row.described;
+      });
+    },
+
+    saveDescription(slug: string, html: string): void {
+      db.query("UPDATE problems SET description = ?2 WHERE slug = ?1").run(slug, html);
+    },
+
+    /** Per-solution lifecycle rows keyed by LC number. */
+    solutionActivity(): Map<number, SolutionActivity> {
+      const rows = db
+        .query<{ id: number; created_at: string; last_tested: string | null; last_submitted: string | null }, []>(
+          "SELECT id, created_at, last_tested, last_submitted FROM solutions",
+        )
+        .all();
+      return new Map(
+        rows.map((r) => [r.id, { createdAt: r.created_at, lastTested: r.last_tested, lastSubmitted: r.last_submitted }]),
+      );
+    },
+
+    /** Register a solution's creation time; existing rows are left alone. */
+    ensureSolution(id: number, createdAt: string): void {
+      db.query("INSERT INTO solutions (id, created_at) VALUES (?1, ?2) ON CONFLICT(id) DO NOTHING").run(id, createdAt);
+    },
+
+    markTested(id: number): void {
+      db.query(
+        `INSERT INTO solutions (id, created_at, last_tested) VALUES (?1, ?2, ?2)
+         ON CONFLICT(id) DO UPDATE SET last_tested = excluded.last_tested`,
+      ).run(id, new Date().toISOString());
+    },
+
+    markSubmitted(id: number): void {
+      db.query(
+        `INSERT INTO solutions (id, created_at, last_submitted) VALUES (?1, ?2, ?2)
+         ON CONFLICT(id) DO UPDATE SET last_submitted = excluded.last_submitted`,
+      ).run(id, new Date().toISOString());
+    },
+
+    close(): void {
+      db.close();
+    },
+  };
+}

apps/cli/github.ts

@@ -1,6 +1,6 @@
 /**
- * GitHub REST plumbing shared by the issue reconcilers (close-solved,
+ * GitHub REST + GraphQL plumbing shared by the issue reconcilers (close-solved,
- * close-topics).
+ * close-topics) and the Project field reconciler (sync-project-fields).
  *
  * Importing this module is side-effect free — nothing resolves credentials or
  * touches the network until github() is awaited — so a script can import it
@@ -22,6 +22,8 @@ export interface GitHub {
   repo: string;
   /** One authenticated request against api.github.com; throws on non-2xx. */
   api(path: string, init?: RequestInit): Promise<unknown>;
+  /** One GraphQL call (Projects v2 lives here); throws on transport or query errors. */
+  graphql(query: string, variables?: Record<string, unknown>): Promise<unknown>;
   /** Every page of a list endpoint, flattened into one stream of elements. */
   list(path: string): AsyncGenerator<unknown, void, void>;
   /** Comment on an issue, then close it as completed. */
@@ -74,6 +76,24 @@ export async function github(): Promise<GitHub> {
     }
   }
 
+  async function graphql(
+    query: string,
+    variables: Record<string, unknown> = {},
+  ): Promise<unknown> {
+    const res = await fetch("https://api.github.com/graphql", {
+      method: "POST",
+      headers: {
+        authorization: `Bearer ${token}`,
+        "content-type": "application/json",
+      },
+      body: JSON.stringify({ query, variables }),
+    });
+    if (!res.ok) throw new Error(`graphql -> ${res.status} ${await res.text()}`);
+    const payload = (await res.json()) as { data?: unknown; errors?: { message: string }[] };
+    if (payload.errors?.length) throw new Error(payload.errors.map((e) => e.message).join("; "));
+    return payload.data;
+  }
+
   /**
    * Comment before closing: if the PATCH fails, the issue still carries a
    * visible note of what the automation decided, instead of failing silently.
@@ -89,5 +109,5 @@ export async function github(): Promise<GitHub> {
     });
   }
 
-  return { repo, api, list, closeIssue };
+  return { repo, api, graphql, list, closeIssue };
 }

apps/cli/package.json

@@ -5,6 +5,7 @@
   "scripts": {
     "pick": "bun ./pick.ts",
     "test": "bun ./test.ts",
+    "submit": "bun ./submit.ts",
     "sync": "bun ./sync.ts",
     "close-solved": "bun ./close-solved.ts",
     "close-topics": "bun ./close-topics.ts"

apps/cli/pick.ts

@@ -1,80 +1,171 @@
 #!/usr/bin/env bun
 /**
- * Fuzzy-pick a LeetCode problem and scaffold it via leetcode-cli.
+ * Fuzzy-pick a problem and scaffold it via leetcode-cli, in one of the three
- * Problem index is fetched from leetcode.com and cached for 24h in .cache/.
+ * work/ buckets (see work.ts): a first solve under work/1, or the 3-day and
+ * 7-day blind re-solves under work/3 and work/7. Tab cycles the sections.
+ *
+ * The problem index lives in the local SQLite cache (see db.ts), refreshed at
+ * most once per 24h; campaign problem descriptions from README.md are
+ * backfilled into the same db on the way. The new-problem section hides
+ * anything that already has a numbered file under work/1 — re-picking it would
+ * only clobber the existing scaffold — and each review section hides whatever
+ * its own bucket already holds, so a finished re-solve leaves the list.
  */
-import { autocomplete, cancel, isCancel, spinner } from "@clack/prompts";
+import { autocomplete, cancel, isCancel, log, spinner } from "@clack/prompts";
-import { mkdir } from "node:fs/promises";
+import { existsSync, mkdirSync, readFileSync, writeFileSync } from "node:fs";
+import { homedir } from "node:os";
 import { join } from "node:path";
+import { styleText } from "node:util";
+import { etDate } from "../api/src/srs.ts";
+import { fetchDescription, problemDb, readmeSlugs } from "./db";
+import { ROOT, WINDOWS, bucketDir, reviewQueues, scanBucket, type Bucket } from "./work";
 
-const ROOT = join(import.meta.dir, "..", "..");
+const db = problemDb();
-const CACHE_FILE = join(ROOT, ".cache", "leetcode-problems.json");
-const CACHE_TTL_MS = 24 * 60 * 60 * 1000;
 
-interface Problem {
+// ── problem index (24h TTL) ──────────────────────────────────────
-  id: number;
-  title: string;
-  slug: string;
-  difficulty: "Easy" | "Medium" | "Hard";
-  paidOnly: boolean;
-}
-
-const DIFFICULTY = ["", "Easy", "Medium", "Hard"] as const;
-
-async function loadProblems(): Promise<Problem[]> {
-  const file = Bun.file(CACHE_FILE);
-  if (await file.exists()) {
-    const stale = Date.now() - file.lastModified > CACHE_TTL_MS;
-    if (!stale) return file.json();
-  }
 
+if (db.indexStale()) {
   const s = spinner();
   s.start("Fetching problem index from leetcode.com");
-  const res = await fetch("https://leetcode.com/api/problems/all/", {
+  try {
-    headers: { "user-agent": "Mozilla/5.0" },
+    s.stop(`Indexed ${await db.refreshIndex()} problems`);
-  });
+  } catch (err) {
-  if (!res.ok) {
+    if (db.all().length === 0) {
-    s.error(`Fetch failed: ${res.status} ${res.statusText}`);
+      s.error(`Fetch failed: ${err}`);
-    process.exit(1);
+      process.exit(1);
+    }
+    s.stop(`Index refresh failed (${err}) — using cached copy`);
   }
-  const data = (await res.json()) as {
-    stat_status_pairs: Array<{
-      stat: {
-        frontend_question_id: number;
-        question__title: string;
-        question__title_slug: string;
-      };
-      difficulty: { level: 1 | 2 | 3 };
-      paid_only: boolean;
-    }>;
-  };
-  const problems: Problem[] = data.stat_status_pairs
-    .map((p) => ({
-      id: p.stat.frontend_question_id,
-      title: p.stat.question__title,
-      slug: p.stat.question__title_slug,
-      difficulty: DIFFICULTY[p.difficulty.level] as Problem["difficulty"],
-      paidOnly: p.paid_only,
-    }))
-    .sort((a, b) => a.id - b.id);
-  s.stop(`Loaded ${problems.length} problems`);
-
-  await mkdir(join(ROOT, ".cache"), { recursive: true });
-  await Bun.write(CACHE_FILE, JSON.stringify(problems));
-  return problems;
 }
 
-const problems = await loadProblems();
+// ── description backfill for the campaign problems in README.md ──
 
-const picked = await autocomplete<Problem>({
+const missing = db.missingDescriptions(readmeSlugs(await Bun.file(join(ROOT, "README.md")).text()));
-  message: "Pick a problem",
+if (missing.length > 0) {
-  placeholder: "Type to search by number or title...",
+  const s = spinner();
-  maxItems: 12,
+  s.start(`Caching ${missing.length} problem descriptions`);
-  options: problems.map((p) => ({
+  let fetched = 0;
-    value: p,
+  let failed = 0;
-    label: `${p.id}. ${p.title}`,
+  await Promise.all(
-    hint: p.paidOnly ? `${p.difficulty} 🔒 premium` : p.difficulty,
+    Array.from({ length: 6 }, async () => {
+      for (let slug = missing.shift(); slug; slug = missing.shift()) {
+        try {
+          const html = await fetchDescription(slug);
+          if (html !== null) db.saveDescription(slug, html);
+          s.message(`Caching problem descriptions (${++fetched})`);
+        } catch {
+          failed++; // left NULL — retried on the next run
+        }
+      }
+    }),
+  );
+  s.stop(failed ? `Cached ${fetched} descriptions (${failed} failed, will retry next run)` : `Cached ${fetched} problem descriptions`);
+}
+
+// ── the three sections ───────────────────────────────────────────
+
+/** What Enter scaffolds: this problem, into this bucket. */
+interface Choice {
+  bucket: Bucket;
+  lc: number;
+  slug: string;
+}
+
+interface Section {
+  label: string;
+  options: { value: Choice; label: string; hint: string }[];
+}
+
+const first = scanBucket(1);
+const problems = db.all();
+const titles = new Map(problems.map((p) => [p.id, p.title] as const));
+db.close();
+
+const queues = reviewQueues(etDate(new Date()));
+
+const sections: Section[] = [
+  {
+    label: "new",
+    options: problems
+      .filter((p) => !first.has(p.id))
+      .map((p) => ({
+        value: { bucket: 1 as Bucket, lc: p.id, slug: p.slug },
+        label: `${p.id}. ${p.title}`,
+        hint: p.paidOnly ? `${p.difficulty} 🔒 premium` : p.difficulty,
+      })),
+  },
+  ...WINDOWS.map((window) => ({
+    label: `${window}-day`,
+    options: queues.get(window)!.map((owed) => ({
+      value: { bucket: window as Bucket, lc: owed.lc, slug: owed.slug },
+      label: `${owed.lc}. ${titles.get(owed.lc) ?? owed.slug}`,
+      hint: `${owed.difficulty} · ${owed.category} · solved ${owed.solved}, ${owed.days}d ago`,
+    })),
   })),
+];
+
+let active = 0;
+
+/**
+ * The slice of clack's AutocompletePrompt this picker drives. @clack/prompts
+ * re-exports neither the class nor its type, and apps/cli does not depend on
+ * @clack/core directly, so the contract is spelled out structurally.
+ */
+interface Autocomplete {
+  userInput: string;
+  on(event: "key", cb: (char: string | undefined, key: { name?: string }) => void): void;
+  emit(event: "userInput", input: string): void;
+}
+
+/** Search text that cannot match any option — see refresh() below. */
+const NO_MATCH = "\u0000";
+
+let hooked = false;
+
+/**
+ * Bind Tab to the section switch, once per prompt.
+ *
+ * clack has no hook for extra keys, but it calls `options` with the prompt as
+ * `this`, which is all a subscription needs. Switching sections also has to
+ * re-filter the list, and the prompt only recomputes `filteredOptions` when
+ * the search text *changes* — hence the pair of userInput events: an
+ * unmatchable string, then the real one, which recomputes against the new
+ * section, resets the cursor onto its first match and leaves the typed query
+ * on screen untouched. clack repaints as soon as the key handlers return.
+ *
+ * No `placeholder` is passed to the prompt on purpose: clack's own Tab binding
+ * (fill the input with the placeholder) is inert without one.
+ */
+function hookTab(prompt: Autocomplete): void {
+  if (hooked) return;
+  hooked = true;
+  prompt.on("key", (_char, key) => {
+    if (key.name !== "tab") return;
+    active = (active + 1) % sections.length;
+    prompt.emit("userInput", NO_MATCH);
+    prompt.emit("userInput", prompt.userInput);
+  });
+}
+
+// Widened, not asserted: clack resolves `undefined` when Enter lands on an
+// empty list, which its own types do not admit.
+const picked: Choice | symbol | undefined = await autocomplete<Choice>({
+  // Getter, not a string: clack reads `message` on every repaint, so the tab
+  // bar tracks the active section.
+  get message(): string {
+    const bar = sections
+      .map((section, i) => {
+        const text = `${section.label} (${section.options.length})`;
+        return i === active ? styleText("cyan", `▸ ${text}`) : styleText("dim", text);
+      })
+      .join(styleText("dim", "  ·  "));
+    return `Pick a problem   ${bar}   ${styleText("dim", "Tab: next section")}`;
+  },
+  maxItems: 12,
+  options(this: Autocomplete) {
+    hookTab(this);
+    return sections[active]!.options;
+  },
   filter: (search, option) => {
     const haystack = option.label!.toLowerCase();
     return search
@@ -88,10 +179,77 @@ if (isCancel(picked)) {
   cancel("Nothing picked.");
   process.exit(0);
 }
+if (picked === undefined) {
+  // Enter on an empty section: nothing was focused, so there is nothing to do.
+  cancel(`Nothing owed in the ${sections[active]!.label} section.`);
+  process.exit(0);
+}
 
-const proc = Bun.spawn(
+// ── scaffold into the picked bucket ──────────────────────────────
-  // bun installs workspace-dep bins into this package's node_modules, not the root's
+
-  [join(import.meta.dir, "node_modules", ".bin", "leetcode"), "pick", picked.slug],
+// The active workspace names the config file; everything else about it belongs
-  { cwd: ROOT, stdio: ["inherit", "inherit", "inherit"] },
+// to leetcode-cli.
-);
+const registry = join(homedir(), ".leetcode", "workspaces.json");
-process.exit(await proc.exited);
+let workspace = "default";
+if (existsSync(registry)) {
+  const parsed: unknown = JSON.parse(readFileSync(registry, "utf8"));
+  if (parsed && typeof parsed === "object" && "active" in parsed && typeof parsed.active === "string") {
+    workspace = parsed.active || workspace;
+  }
+}
+const configPath = join(homedir(), ".leetcode", "workspaces", workspace, "config.json");
+if (!existsSync(configPath)) {
+  log.error(`No leetcode-cli config at ${configPath} — run \`leetcode config -i\` once.`);
+  process.exit(1);
+}
+
+/**
+ * Point leetcode-cli at one bucket. It reads its output directory from the
+ * active workspace config and from nowhere else — no flag, no environment
+ * override — so `workDir` is the whole handover.
+ *
+ * Each write MERGES the file as it is on disk at that moment; a saved copy is
+ * never played back. The CLI owns this file too (theme, language, whatever a
+ * `leetcode login` adds), and replaying stale bytes over it would silently
+ * undo what it wrote while the child ran. After the pick, `workDir` is set to
+ * work/1 instead of to whatever it was before: the first-solve bucket is the
+ * one resting value that is always right, so even a killed run leaves a bare
+ * `leetcode pick` on-layout.
+ */
+function setWorkDir(target: string): void {
+  const raw: unknown = JSON.parse(readFileSync(configPath, "utf8"));
+  if (raw === null || typeof raw !== "object") {
+    log.error(`${configPath} holds no JSON object — run \`leetcode config -i\` to rewrite it.`);
+    process.exit(1);
+  }
+  // 2-space JSON with a trailing newline: leetcode-cli's own format.
+  writeFileSync(configPath, `${JSON.stringify({ ...raw, workDir: target }, null, 2)}\n`);
+}
+
+const dir = bucketDir(picked.bucket);
+mkdirSync(dir, { recursive: true });
+setWorkDir(dir);
+
+let code: number;
+try {
+  const proc = Bun.spawn(
+    // bun installs workspace-dep bins into this package's node_modules, not the root's
+    [join(import.meta.dir, "node_modules", ".bin", "leetcode"), "pick", picked.slug],
+    { cwd: ROOT, stdio: ["inherit", "inherit", "inherit"] },
+  );
+  code = await proc.exited;
+} finally {
+  setWorkDir(bucketDir(1));
+}
+
+// leetcode-cli exits 0 even when it wrote nothing (an expired session only
+// prints a warning), so the scaffold itself is the acceptance test: without a
+// file for this problem in the bucket, the pick failed.
+if (!scanBucket(picked.bucket).has(picked.lc)) {
+  log.error(
+    `leetcode-cli scaffolded nothing for LC ${picked.lc} under work/${picked.bucket}/.\n` +
+      "If it printed “Session expired”, run `leetcode login` and pick again.",
+  );
+  process.exit(code === 0 ? 1 : code);
+}
+process.exit(code);

apps/cli/solutions.ts

@@ -0,0 +1,115 @@
+/**
+ * Shared work/ solution picker for the test and submit entries: fuzzy-select
+ * a solution file, then hand it to leetcode-cli.
+ *
+ * Every bucket is listed — a 3-day or 7-day re-solve is tested and submitted
+ * exactly like a first solve — and the hint says which one a file belongs to.
+ * The db's per-solution timestamps are keyed by LC number, so the buckets of
+ * one problem share them.
+ *
+ * Every run backfills the db's solutions table with created_at (from the
+ * file's birthtime, mtime when the filesystem has none) so ordering works for
+ * files that predate the db. Ordering is per command — test lists the most
+ * recently tested first (never-tested after, by name); submit lists the most
+ * recently created first. Nothing is ever hidden. Exit 0 of leetcode-cli
+ * stamps last_tested / last_submitted.
+ *
+ * Library: side-effect-free on import — nothing scans the filesystem until
+ * runOnSolution() is called.
+ */
+import { autocomplete, cancel, isCancel, log } from "@clack/prompts";
+import { statSync } from "node:fs";
+import { basename, join, relative } from "node:path";
+import { problemDb } from "./db";
+import { ROOT, WORK as WORK_DIR, parseWorkPath } from "./work";
+
+/** Leading LC number of a work/ file, or undefined for unnumbered names. */
+function lcNumber(rel: string): number | undefined {
+  const m = basename(rel).match(/^(\d+)\./);
+  return m ? Number(m[1]) : undefined;
+}
+
+/** Fuzzy-pick a solution under work/ and run `leetcode <command>` on it. */
+export async function runOnSolution(command: "test" | "submit", message: string): Promise<never> {
+  const db = problemDb();
+
+  const scanned = [...new Bun.Glob("**/*.{js,ts,py,java,c,cpp,go,rs,rb,swift,kt,cs}").scanSync({ cwd: WORK_DIR })];
+
+  // register creation times so files older than the db still sort correctly
+  for (const f of scanned) {
+    const num = lcNumber(f);
+    if (num === undefined) continue;
+    const stat = statSync(join(WORK_DIR, f));
+    db.ensureSolution(num, new Date(stat.birthtimeMs || stat.mtimeMs).toISOString());
+  }
+  const activity = db.solutionActivity();
+
+  // test → most recently tested first; submit → most recently created first
+  const sortKey = (f: string) => {
+    const num = lcNumber(f);
+    const row = num === undefined ? undefined : activity.get(num);
+    return (command === "test" ? row?.lastTested : row?.createdAt) ?? undefined;
+  };
+
+  const files = scanned
+    .sort((a, b) => {
+      const ka = sortKey(a);
+      const kb = sortKey(b);
+      if (ka !== kb) {
+        if (ka === undefined) return 1;
+        if (kb === undefined) return -1;
+        return kb.localeCompare(ka); // ISO timestamps: lexicographic = chronological
+      }
+      return a.localeCompare(b, undefined, { numeric: true });
+    });
+
+  if (files.length === 0) {
+    log.error(`No solution files found in ${relative(process.cwd(), WORK_DIR)}/`);
+    process.exit(1);
+  }
+
+  const picked = await autocomplete<string>({
+    message,
+    placeholder: "Type to search...",
+    maxItems: 12,
+    options: files.map((f) => {
+      const parsed = parseWorkPath(f);
+      const stage = parsed?.bucket === 1 ? "first solve" : `${parsed?.bucket}-day review`;
+      return {
+        value: f,
+        label: basename(f),
+        hint: parsed ? `${stage} · ${parsed.difficulty} · ${parsed.category}` : f,
+      };
+    }),
+    filter: (search, option) => {
+      const haystack = option.value.toLowerCase();
+      return search
+        .toLowerCase()
+        .split(/\s+/)
+        .every((token) => haystack.includes(token));
+    },
+  });
+
+  if (isCancel(picked)) {
+    cancel("Nothing selected.");
+    process.exit(0);
+  }
+
+  const proc = Bun.spawn(
+    [
+      // bun installs workspace-dep bins into this package's node_modules, not the root's
+      join(import.meta.dir, "node_modules", ".bin", "leetcode"),
+      command,
+      join(WORK_DIR, picked),
+    ],
+    { cwd: ROOT, stdio: ["inherit", "inherit", "inherit"] },
+  );
+  const code = await proc.exited;
+  const num = lcNumber(picked);
+  if (code === 0 && num !== undefined) {
+    if (command === "test") db.markTested(num);
+    else db.markSubmitted(num);
+  }
+  db.close();
+  process.exit(code);
+}

apps/cli/source.ts

@@ -0,0 +1,61 @@
+/**
+ * Is a work/ file a real solution or just a scaffolded stub?
+ *
+ * `bun run pick` writes a statement header plus an empty function body, so
+ * file existence alone means nothing: close-solved.ts must not close an issue
+ * on a stub, and work.ts must not ask for the spaced-repetition re-solve of a
+ * problem that was never solved in the first place.
+ *
+ * sync.ts keeps its own copy of the header split — it runs its whole pipeline
+ * on import, so it cannot be imported from. Don't "deduplicate" that one.
+ *
+ * Library: side-effect-free on import.
+ */
+
+/** Placeholder bodies that leetcode-cli / a human leaves behind. */
+const PLACEHOLDERS: Record<string, true> = { pass: true, "...": true, TODO: true };
+
+/**
+ * Decide whether a work/ file contains an implementation.
+ *
+ * The header comment is dropped the same way sync.ts splitSource() does it.
+ * Comments must go before any brace analysis: the scaffold's JSDoc carries
+ * `@param {number[]}`, whose braces would otherwise read as a body.
+ *
+ * A brace-language file counts as implemented when at least one *innermost*
+ * brace pair holds real content. That distinguishes a bare stub
+ * (`function(nums) {}`) and a class-shaped design stub (every method body
+ * empty) from any genuine solution, whose innermost block always has code.
+ * Every non-Python language the campaign has ever used is brace-shaped, so
+ * "not .py" is the only branch that matters.
+ */
+export function isImplemented(src: string, lang: "js" | "py"): boolean {
+  if (lang === "py") {
+    const open = src.indexOf('"""');
+    const close = src.indexOf('"""', open + 3);
+    const code = open === -1 || close === -1 ? src : src.slice(close + 3);
+    for (const raw of code.split("\n")) {
+      const line = raw.replace(/#.*$/, "").trim();
+      if (!line || PLACEHOLDERS[line]) continue;
+      if (/^(?:@|def\s|class\s)/.test(line)) continue;
+      return true; // a statement inside some def body
+    }
+    return false;
+  }
+
+  const headerEnd = src.indexOf("*/");
+  const body = headerEnd === -1 ? src : src.slice(headerEnd + 2);
+  const code = body.replace(/\/\*[\s\S]*?\*\//g, " ").replace(/\/\/.*$/gm, " ");
+
+  let innermost = -1;
+  for (let i = 0; i < code.length; i++) {
+    if (code[i] === "{") {
+      innermost = i;
+    } else if (code[i] === "}" && innermost !== -1) {
+      const inner = code.slice(innermost + 1, i).replace(/[\s;]/g, "");
+      if (inner && !PLACEHOLDERS[inner]) return true;
+      innermost = -1; // measured; the enclosing pair is not innermost
+    }
+  }
+  return false;
+}

apps/cli/spaced-repetition.ts

@@ -0,0 +1,384 @@
+#!/usr/bin/env bun
+/**
+ * Open today's spaced-repetition issue: whatever the SRS ladder has due,
+ * linked straight to LeetCode.
+ *
+ * D1 is the schedule and this script is a renderer. `POST /admin/due` returns
+ * exactly the rows the 8 AM digest mails — reviews standing at the `+3` and
+ * `+7` rungs, oldest first — so the issue and the email can never disagree
+ * about a day, and there is no second scheduler to drift. The rung is also
+ * the `work/<n>` bucket the blind re-solve belongs in, which is the section
+ * `bun run pick` opens on Tab.
+ *
+ * How a problem gets here: closing its issue (a push, a digest tap, a `/done`
+ * comment) enters it on the ladder at `+3` with a concrete next_review, and
+ * passing that review moves it to `+7`. Nothing is "activated" by this script
+ * — it asks what is standing today and writes it down. A day's issue is keyed
+ * by its title (`Spaced Repetition — <Month D, YYYY>`), so re-runs rewrite
+ * that one body instead of stacking duplicates.
+ *
+ * Sunday writes nothing: the ladder never schedules the rest day (WINDOWS of
+ * 3 and 7 exist for exactly that reason, see apps/api/src/srs.ts), so there is
+ * nothing to render. Each rung shows at most WINDOW_CAP problems, with the
+ * overflow listed as optional — the digest's leveller moves that overflow to
+ * later working days the next morning.
+ *
+ * Links: D1 stores titles, not URLs, so each due problem's issue body is read
+ * for the canonical LeetCode link. A body with no URL falls back to a slug
+ * guessed from the title and is flagged in the report, because repo titles are
+ * sometimes abbreviated ("LC 167 · Two Sum II") and a guess can 404.
+ *
+ *   bun apps/cli/spaced-repetition.ts                   # create/update today's issue
+ *   bun apps/cli/spaced-repetition.ts --dry-run         # print the body, touch nothing
+ *   bun apps/cli/spaced-repetition.ts --date=2026-09-02 # pretend it is that ET day
+ *
+ * Auth: GH_TOKEN / GITHUB_TOKEN, else falls back to `gh auth token`.
+ *       SRS_ADMIN_KEY reads the due list; SRS_API overrides the Worker URL for
+ *       local `wrangler dev` runs.
+ */
+import { WINDOWS, etDate, isRestDay } from "../api/src/srs.ts";
+import { github } from "./github.ts";
+import { markdownTable, printTable, writeStepSummary } from "./report.ts";
+
+const DRY =
+  process.argv.includes("--dry-run") ||
+  process.env.DRY_RUN === "1" ||
+  process.env.DRY_RUN === "true";
+
+/**
+ * Required re-solves per window: 3 + 3 on top of the day's 3 new core problems
+ * is already a 90-minute session. A window that closed more than this (the
+ * catalog backfill closed 19 issues in one day) keeps the rest listed under a
+ * collapsed "optional" block rather than pretending they were never due.
+ */
+const WINDOW_CAP = 3;
+
+const LABEL = "spaced-repetition";
+
+// ── ET calendar dates ────────────────────────────────────────────
+
+// Every date here is an ET calendar string (YYYY-MM-DD): the campaign runs on
+// ET days, and an issue closed at 21:30 ET belongs to that ET day, not to the
+// next UTC one. The helpers come from the Worker's SRS domain so this script,
+// the picker and D1 cannot disagree about a date, a window, or the rest day.
+
+const LONG = new Intl.DateTimeFormat("en-US", {
+  timeZone: "UTC",
+  weekday: "long",
+  month: "long",
+  day: "numeric",
+  year: "numeric",
+});
+
+/** `2026-08-26` -> `August 26, 2026`, or with the weekday prefix. */
+function longDate(date: string, weekday = false): string {
+  // Noon-UTC anchor, like every date in srs.ts: no DST edge can move the day.
+  const text = LONG.format(new Date(`${date}T12:00:00Z`));
+  return weekday ? text : text.slice(text.indexOf(", ") + 2);
+}
+
+// ── today ────────────────────────────────────────────────────────
+
+// `||`, not `??`: the workflow passes SRS_TODAY="" on scheduled runs, where the
+// input has no value.
+const override = process.argv.find((a) => a.startsWith("--date="))?.slice(7) || process.env.SRS_TODAY;
+if (override && !/^\d{4}-\d{2}-\d{2}$/.test(override)) {
+  throw new Error(`--date wants YYYY-MM-DD, got ${override}`);
+}
+const today = override || etDate(new Date());
+
+// Sunday is the campaign's rest day and the reason the windows are 3 and 7:
+// nothing is ever booked on it, so there is no issue to write. The cron still
+// fires — the guard lives here, not in the workflow, so a manual run agrees.
+if (isRestDay(today)) {
+  console.log(`${today} is the rest day — no spaced-repetition issue.`);
+  await writeStepSummary(`### Spaced Repetition — ${longDate(today)}\n\nRest day: nothing scheduled.\n`);
+  process.exit(0);
+}
+
+// ── what is due today (D1, via the Worker) ───────────────────────
+
+// The ladder is the schedule: `POST /admin/due` returns exactly the rows the
+// morning digest mails, so the issue and the email can never disagree about a
+// day. This script adds no scheduling of its own — it renders, caps, and
+// links.
+const SRS_API = process.env.SRS_API ?? "https://srs-api.prdlk.workers.dev";
+
+/** One problem the ladder wants re-solved today, as the Worker reports it. */
+interface Due {
+  lc: number;
+  issue: number;
+  title: string;
+  difficulty: string;
+  /** The rung being settled: "+3" or "+7". */
+  stage: string;
+  /** The rung's number — also the `work/<n>` bucket the re-solve belongs in. */
+  bucket: number;
+  due: string;
+  late: number;
+  last_seen: string | null;
+  days_since: number | null;
+}
+
+function readDue(value: unknown): Due | undefined {
+  if (!value || typeof value !== "object") return;
+  const num = (key: string): number | undefined =>
+    key in value && typeof (value as Record<string, unknown>)[key] === "number"
+      ? ((value as Record<string, unknown>)[key] as number)
+      : undefined;
+  const str = (key: string): string | undefined =>
+    key in value && typeof (value as Record<string, unknown>)[key] === "string"
+      ? ((value as Record<string, unknown>)[key] as string)
+      : undefined;
+  const lc = num("lc");
+  const issue = num("issue");
+  const bucket = num("bucket");
+  const stage = str("stage");
+  const title = str("title");
+  const dueOn = str("due");
+  if (lc === undefined || issue === undefined || bucket === undefined) return;
+  if (stage === undefined || title === undefined || dueOn === undefined) return;
+  const difficulty = str("difficulty") ?? "unrated";
+  return {
+    lc,
+    issue,
+    title,
+    difficulty: difficulty.charAt(0).toUpperCase() + difficulty.slice(1),
+    stage,
+    bucket,
+    due: dueOn,
+    late: num("late") ?? 0,
+    last_seen: str("last_seen") ?? null,
+    days_since: num("days_since") ?? null,
+  };
+}
+
+if (!process.env.SRS_ADMIN_KEY) {
+  // Failing loudly beats writing an issue from a second, guessed schedule:
+  // there is only one schedule now, and it lives in D1.
+  console.error("SRS_ADMIN_KEY unset — cannot read today's due list from the Worker.");
+  process.exit(1);
+}
+const res = await fetch(`${SRS_API}/admin/due?date=${today}`, {
+  method: "POST",
+  headers: { authorization: `Bearer ${process.env.SRS_ADMIN_KEY}` },
+});
+if (!res.ok) throw new Error(`GET due list -> ${res.status} ${await res.text()}`);
+const payload: unknown = await res.json();
+const dueRaw: unknown = payload && typeof payload === "object" && "due" in payload ? payload.due : null;
+const due: Due[] = (Array.isArray(dueRaw) ? dueRaw : []).flatMap((r) => {
+  const row = readDue(r);
+  return row ? [row] : [];
+});
+
+// ── repo + auth ──────────────────────────────────────────────────
+
+const gh = await github();
+
+// ── canonical LeetCode links ─────────────────────────────────────
+
+const LC_URL = /https:\/\/leetcode\.com\/problems\/[a-z0-9-]+/;
+
+/** LeetCode's own slug shape, for bodies that lost their URL line. */
+function slugify(name: string): string {
+  return name
+    .toLowerCase()
+    .replace(/[^a-z0-9]+/g, "-")
+    .replace(/^-|-$/g, "");
+}
+
+/**
+ * D1 stores titles, not URLs, so each due problem's issue body is read for the
+ * canonical LeetCode link written by the campaign-issues convention. That is
+ * one request per due problem — at most REVIEW_CAP per rung — instead of the
+ * old walk over every closed issue in the repo. A body with no URL falls back
+ * to a slug guessed from the title and is flagged in the report, because repo
+ * titles are sometimes abbreviated ("LC 167 · Two Sum II") and a guess can 404.
+ */
+interface Linked extends Due {
+  url: string;
+  linked: boolean;
+}
+
+async function link(row: Due): Promise<Linked> {
+  let url: string | undefined;
+  try {
+    const issue: unknown = await gh.api(`/repos/${gh.repo}/issues/${row.issue}`);
+    const body =
+      issue && typeof issue === "object" && "body" in issue && typeof issue.body === "string"
+        ? issue.body
+        : "";
+    url = LC_URL.exec(body)?.[0];
+  } catch (err) {
+    console.warn(`#${row.issue}: could not read the issue body (${err})`);
+  }
+  return {
+    ...row,
+    url: `${url ?? `https://leetcode.com/problems/${slugify(row.title)}`}/`,
+    linked: url !== undefined,
+  };
+}
+
+// ── issue body ───────────────────────────────────────────────────
+
+const title = `Spaced Repetition — ${longDate(today)}`;
+
+/** The window's due problems, capped, oldest scheduled first. */
+const byWindow = new Map<number, Linked[]>();
+for (const days of WINDOWS) {
+  const rows = due.filter((d) => d.bucket === days);
+  byWindow.set(days, await Promise.all(rows.map(link)));
+}
+
+function bucket(days: number): Linked[] {
+  return byWindow.get(days) ?? [];
+}
+
+/** One checkbox line, straight to LeetCode. */
+function line(s: Linked, box: boolean): string {
+  const seen = s.days_since === null ? "unlogged" : `last seen ${s.days_since}d ago`;
+  return (
+    `${box ? "- [ ] " : "- "}[LC ${s.lc} · ${s.title}](${s.url}) · ${s.difficulty} · #${s.issue}` +
+    ` · ${seen}${s.late > 0 ? ` · ⏰ ${s.late}d late` : ""}` +
+    (s.linked ? "" : " · ⚠️ link guessed from title")
+  );
+}
+
+const sections = WINDOWS.map((days) => {
+  const rows = bucket(days);
+  const required = rows.slice(0, WINDOW_CAP);
+  const spill = rows.slice(WINDOW_CAP);
+  return [
+    `### +${days} days — re-solve into \`work/${days}/\``,
+    "",
+    ...(required.length
+      ? required.map((s) => line(s, true))
+      : [`_Nothing at the +${days} rung today._`]),
+    // Overflow is shown, not dropped: the ladder levels everything past the
+    // cap onto later working days, but until that morning's digest runs this
+    // issue is the only record of what was standing.
+    ...(spill.length
+      ? [
+          "",
+          `<details><summary>${spill.length} more at this rung — optional</summary>`,
+          "",
+          ...spill.map((s) => line(s, false)),
+          "",
+          "</details>",
+        ]
+      : []),
+    "",
+  ].join("\n");
+});
+
+const total = WINDOWS.reduce((n, days) => n + Math.min(bucket(days).length, WINDOW_CAP), 0);
+
+const body = [
+  `Re-solve from memory, ${longDate(today, true)}. Blind: no notes, no \`work/\` file, no editor history.`,
+  "",
+  "- 15 minutes per problem, then stop and read your own solution.",
+  "- Say the invariant and the complexity out loud before typing.",
+  "- Failed one? Tick it anyway and expect it back at +3.",
+  "- `bun run pick` → Tab to this rung's section scaffolds the blind re-solve.",
+  "",
+  ...sections,
+  "<sub>Today's due list straight from the SRS ladder in D1 (`POST /admin/due`), rendered by " +
+    "`.github/workflows/spaced-repetition.yml` — re-runs on the same day rewrite this body. " +
+    "The ladder never schedules a Sunday, so there is no issue on the rest day.</sub>",
+].join("\n");
+
+// ── create or refresh today's issue ──────────────────────────────
+
+interface Existing {
+  number: number;
+  title: string;
+  body: string;
+}
+
+function readExisting(value: unknown): Existing | undefined {
+  if (!value || typeof value !== "object") return;
+  if ("pull_request" in value) return;
+  if (!("number" in value) || typeof value.number !== "number") return;
+  if (!("title" in value) || typeof value.title !== "string") return;
+  const text = "body" in value && typeof value.body === "string" ? value.body : "";
+  return { number: value.number, title: value.title, body: text };
+}
+
+// state=all: a day's issue that was already closed must not be recreated.
+let existing: Existing | undefined;
+for await (const raw of gh.list(`/repos/${gh.repo}/issues?labels=${LABEL}&state=all`)) {
+  const row = readExisting(raw);
+  if (row?.title === title) {
+    existing = row;
+    break;
+  }
+}
+
+let status: string;
+if (total === 0) {
+  status = existing
+    ? `nothing due — left #${existing.number} alone`
+    : "nothing due — no issue created";
+} else if (existing && existing.body.trim() === body.trim()) {
+  status = `#${existing.number} already current`;
+} else if (DRY) {
+  status = existing ? `would update #${existing.number}` : "would create";
+} else if (existing) {
+  await gh.api(`/repos/${gh.repo}/issues/${existing.number}`, {
+    method: "PATCH",
+    body: JSON.stringify({ body }),
+  });
+  status = `updated #${existing.number}`;
+} else {
+  // Ensure the label exists before it is used (422 = someone already made it).
+  try {
+    await gh.api(`/repos/${gh.repo}/labels`, {
+      method: "POST",
+      body: JSON.stringify({
+        name: LABEL,
+        color: "0E8A16",
+        description: "Daily blind re-solve of whatever the SRS ladder has due",
+      }),
+    });
+  } catch (err) {
+    if (!String(err).includes("422")) throw err;
+  }
+
+  const created = (await gh.api(`/repos/${gh.repo}/issues`, {
+    method: "POST",
+    body: JSON.stringify({ title, body, labels: [LABEL] }),
+  })) as { number: number };
+  status = `created #${created.number}`;
+}
+
+// ── report ───────────────────────────────────────────────────────
+
+const report = WINDOWS.flatMap((days) =>
+  bucket(days).map((s, i) => [
+    `+${days}d`,
+    String(s.lc),
+    `#${s.issue}`,
+    s.difficulty,
+    s.due + (s.late > 0 ? ` (${s.late}d late)` : ""),
+    i < WINDOW_CAP ? "due" : "optional",
+    s.linked ? s.url : `${s.url} (inferred)`,
+  ]),
+);
+const rows = [["rung", "lc", "issue", "diff", "scheduled", "state", "leetcode"], ...report];
+if (report.length) printTable(rows);
+
+console.log(
+  `\n${title}${DRY ? " (dry run)" : ""}\n` +
+    WINDOWS.map((days) => {
+      const n = bucket(days).length;
+      return `+${days}d: ${Math.min(n, WINDOW_CAP)} due${n > WINDOW_CAP ? ` (+${n - WINDOW_CAP} optional)` : ""}`;
+    }).join(" · ") +
+    `\n${status}`,
+);
+if (DRY) console.log(`\n${body}`);
+
+await writeStepSummary(
+  `### ${title}${DRY ? " (dry run)" : ""}\n\n` +
+    `${total} problem${total === 1 ? "" : "s"} due · ${status}\n\n` +
+    (report.length ? `${markdownTable(rows)}\n` : "The ladder has nothing due today.\n"),
+);

apps/cli/submit.ts

@@ -0,0 +1,7 @@
+#!/usr/bin/env bun
+/**
+ * Fuzzy-select a solution file from work/ and submit it to LeetCode's judge.
+ */
+import { runOnSolution } from "./solutions";
+
+await runOnSolution("submit", "Submit which solution?");

apps/cli/sync-project-fields.ts

@@ -0,0 +1,252 @@
+#!/usr/bin/env bun
+/**
+ * Reconcile the "Interview Prep" Project's Set and Difficulty fields from the
+ * labels on each problem issue.
+ *
+ * The issue labels are the truth: `set:core|optional|deferred` and
+ * `diff:easy|medium|hard` are fixed when a problem issue is filed, and the
+ * Project's single-selects are a projection of them so the board can group and
+ * filter. This recomputes every desired value from scratch and writes only the
+ * ones that differ, so re-runs are no-ops and a backfill needs no special
+ * casing — same reconcile-don't-react shape as close-solved / close-topics.
+ *
+ * Scope guard: only items whose issue carries the `problem` label are touched.
+ * Topic, cadence and review issues have no set or difficulty, so they are
+ * skipped outright — never written, never cleared.
+ *
+ * Deliberately NOT mirrored: SRS stage and first-attempt result. Those live
+ * only in D1 (apps/api owns them; the charts, digest and /api/stats read them
+ * from there). The Project mirror writes Target Date and nothing else.
+ *
+ * Auth: needs a token carrying the `project` scope — neither the default
+ * `gh auth token` nor Actions' GITHUB_TOKEN has it. Pass one in GH_TOKEN: the
+ * PROJECT_PAT secret in CI, or the Worker's GH_PAT locally:
+ *   GH_TOKEN=$GH_PAT bun run sync-project-fields -- --dry-run
+ */
+import { github, type GitHub } from "./github.ts";
+import { markdownTable, printTable, writeStepSummary } from "./report.ts";
+
+const PROJECT_TITLE = "Interview Prep";
+
+/** Label → single-select option name, per field. Static tables, so Record. */
+const FIELDS: Record<string, Record<string, string>> = {
+  Set: { "set:core": "Core", "set:optional": "Optional", "set:deferred": "Deferred" },
+  Difficulty: { "diff:easy": "Easy", "diff:medium": "Medium", "diff:hard": "Hard" },
+};
+
+const DRY =
+  process.argv.includes("--dry-run") ||
+  process.env.DRY_RUN === "1" ||
+  process.env.DRY_RUN === "true";
+
+// ── project + field resolution ───────────────────────────────────
+
+interface SelectField {
+  id: string;
+  /** option name → option id */
+  options: Record<string, string>;
+}
+
+interface Project {
+  id: string;
+  fields: Record<string, SelectField>;
+}
+
+/**
+ * Field and option IDs are resolved by NAME, so re-creating a field in the UI
+ * does not strand this script on a dead id.
+ */
+async function readProject(gh: GitHub, owner: string): Promise<Project> {
+  const data = (await gh.graphql(
+    `query($owner: String!, $title: String!) {
+      user(login: $owner) {
+        projectsV2(first: 10, query: $title) {
+          nodes {
+            id title
+            fields(first: 30) {
+              nodes {
+                ... on ProjectV2SingleSelectField { id name options { id name } }
+              }
+            }
+          }
+        }
+      }
+    }`,
+    { owner, title: PROJECT_TITLE },
+  )) as {
+    user: {
+      projectsV2: {
+        nodes: {
+          id: string;
+          title: string;
+          fields: { nodes: ({ id: string; name: string; options: { id: string; name: string }[] } | Record<string, never>)[] };
+        }[];
+      };
+    };
+  };
+
+  const node = data.user.projectsV2.nodes.find((n) => n.title === PROJECT_TITLE);
+  if (!node) throw new Error(`project "${PROJECT_TITLE}" not found for @${owner}`);
+
+  const fields: Record<string, SelectField> = {};
+  for (const name of Object.keys(FIELDS)) {
+    const field = node.fields.nodes.find((f) => "name" in f && f.name === name);
+    if (!field || !("options" in field)) {
+      throw new Error(`single-select field "${name}" missing from "${PROJECT_TITLE}"`);
+    }
+    fields[name] = {
+      id: field.id,
+      options: Object.fromEntries(field.options.map((o) => [o.name, o.id])),
+    };
+  }
+  return { id: node.id, fields };
+}
+
+// ── items ────────────────────────────────────────────────────────
+
+interface Item {
+  id: string;
+  issue: number;
+  title: string;
+  labels: string[];
+  /** field name → current option name */
+  current: Record<string, string>;
+}
+
+async function* readItems(gh: GitHub, project: string): AsyncGenerator<Item, void, void> {
+  let cursor: string | null = null;
+  for (;;) {
+    const data = (await gh.graphql(
+      `query($id: ID!, $after: String) {
+        node(id: $id) {
+          ... on ProjectV2 {
+            items(first: 100, after: $after) {
+              pageInfo { hasNextPage endCursor }
+              nodes {
+                id
+                fieldValues(first: 25) {
+                  nodes {
+                    ... on ProjectV2ItemFieldSingleSelectValue {
+                      name field { ... on ProjectV2FieldCommon { name } }
+                    }
+                  }
+                }
+                content {
+                  ... on Issue { number title labels(first: 25) { nodes { name } } }
+                }
+              }
+            }
+          }
+        }
+      }`,
+      { id: project, after: cursor },
+    )) as {
+      node: {
+        items: {
+          pageInfo: { hasNextPage: boolean; endCursor: string };
+          nodes: {
+            id: string;
+            fieldValues: { nodes: ({ name: string; field: { name: string } } | Record<string, never>)[] };
+            content: { number: number; title: string; labels: { nodes: { name: string }[] } } | Record<string, never>;
+          }[];
+        };
+      };
+    };
+
+    for (const node of data.node.items.nodes) {
+      const content = node.content;
+      // Draft items and PRs have no issue number; nothing to reconcile.
+      if (!("number" in content) || typeof content.number !== "number") continue;
+      const current: Record<string, string> = {};
+      for (const value of node.fieldValues.nodes) {
+        if ("name" in value && value.field?.name) current[value.field.name] = value.name;
+      }
+      yield {
+        id: node.id,
+        issue: content.number,
+        title: content.title,
+        labels: content.labels.nodes.map((l) => l.name),
+        current,
+      };
+    }
+
+    const page = data.node.items.pageInfo;
+    if (!page.hasNextPage) return;
+    cursor = page.endCursor;
+  }
+}
+
+// ── reconcile ────────────────────────────────────────────────────
+
+interface Write {
+  item: string;
+  issue: number;
+  title: string;
+  field: string;
+  from: string;
+  to: string;
+}
+
+async function setField(gh: GitHub, project: string, w: Write, option: string): Promise<void> {
+  await gh.graphql(
+    `mutation($project: ID!, $item: ID!, $field: ID!, $option: String!) {
+      updateProjectV2ItemFieldValue(
+        input: {
+          projectId: $project, itemId: $item, fieldId: $field
+          value: { singleSelectOptionId: $option }
+        }
+      ) { projectV2Item { id } }
+    }`,
+    { project, item: w.item, field: w.field, option },
+  );
+}
+
+const gh = await github();
+const owner = gh.repo.split("/")[0]!;
+const project = await readProject(gh, owner);
+
+const writes: Write[] = [];
+let problems = 0;
+let skipped = 0;
+
+for await (const item of readItems(gh, project.id)) {
+  if (!item.labels.includes("problem")) {
+    skipped++;
+    continue;
+  }
+  problems++;
+  for (const [field, mapping] of Object.entries(FIELDS)) {
+    const want = item.labels.map((l) => mapping[l]).find(Boolean);
+    if (!want) {
+      console.warn(`#${item.issue} has no ${field.toLowerCase()} label — left untouched`);
+      continue;
+    }
+    const from = item.current[field];
+    if (from === want) continue;
+    if (!project.fields[field]!.options[want]) {
+      throw new Error(`field "${field}" has no option "${want}"`);
+    }
+    writes.push({
+      item: item.id,
+      issue: item.issue,
+      title: item.title,
+      field: project.fields[field]!.id,
+      from: from ?? "(empty)",
+      to: want,
+    });
+  }
+}
+
+const rows: string[][] = [["ISSUE", "PROBLEM", "FIELD", "FROM", "TO"]];
+for (const w of writes) {
+  const name = Object.entries(project.fields).find(([, f]) => f.id === w.field)![0];
+  rows.push([`#${w.issue}`, w.title.slice(0, 46), name, w.from, w.to]);
+  if (DRY) continue;
+  await setField(gh, project.id, w, project.fields[name]!.options[w.to]!);
+}
+
+if (writes.length) printTable(rows);
+console.log(
+  `\n${DRY ? "would update" : "updated"} ${writes.length} field value(s) across ${problems} problem item(s); ${skipped} non-problem item(s) skipped`,
+);
+if (writes.length) await writeStepSummary(markdownTable(rows));

apps/cli/sync.ts

@@ -1,6 +1,6 @@
 #!/usr/bin/env bun
 /**
- * Sync work/ leetcode solutions into apps/docs/content/ pages.
+ * Sync work/1 leetcode solutions into apps/docs/content/ pages.
  *
  * - New problems get a full page (frontmatter, badge, warning, examples,
  *   constraints, solution) in the gold-standard format.
@@ -9,12 +9,16 @@
  * - When a problem is solved in both JavaScript and Python the solution
  *   renders as a <CodeGroup> (Python first); single-language solutions
  *   render as a plain fence.
+ *
+ * Only the first-solve bucket is read: work/3 and work/7 hold blind re-solves
+ * of problems whose page already exists (see work.ts), and a fresh scaffold
+ * there would otherwise wipe the page's `## Solution`.
  */
 import { mkdir, rename } from "node:fs/promises";
 import { basename, join } from "node:path";
 
 const ROOT = join(import.meta.dir, "..", "..");
-const WORK = join(ROOT, "work");
+const WORK = join(ROOT, "work", "1");
 const DOCS = join(ROOT, "apps", "docs", "content");
 
 type Lang = "js" | "py";
@@ -323,7 +327,7 @@ for await (const rel of new Bun.Glob("**/*.{js,py}").scan(WORK)) {
   const file = basename(rel);
   const m = file.match(/^(\d+)\.(.+)\.(?:js|py)$/);
   if (!m) {
-    console.warn(`skip (unrecognized name): work/${rel}`);
+    console.warn(`skip (unrecognized name): work/1/${rel}`);
     continue;
   }
   const num = Number(m[1]);

apps/cli/test.ts

@@ -2,54 +2,6 @@
 /**
  * Fuzzy-select a solution file from work/ and run leetcode-cli tests on it.
  */
-import { autocomplete, cancel, isCancel, log } from "@clack/prompts";
+import { runOnSolution } from "./solutions";
-import { join, relative } from "node:path";
 
-const ROOT = join(import.meta.dir, "..", "..");
+await runOnSolution("test", "Test which solution?");
-const WORK_DIR = join(ROOT, "work");
-
-const files = [...new Bun.Glob("**/*.{js,ts,py,java,c,cpp,go,rs,rb,swift,kt,cs}").scanSync({ cwd: WORK_DIR })]
-  .sort((a, b) => a.localeCompare(b, undefined, { numeric: true }));
-
-if (files.length === 0) {
-  log.error(`No solution files found in ${relative(process.cwd(), WORK_DIR)}/`);
-  process.exit(1);
-}
-
-const picked = await autocomplete<string>({
-  message: "Test which solution?",
-  placeholder: "Type to search...",
-  maxItems: 12,
-  options: files.map((f) => {
-    // work layout: Difficulty/Category/<id>.<slug>.<ext>
-    const [difficulty, category, name] = f.split("/");
-    return {
-      value: f,
-      label: name ?? f,
-      hint: category ? `${difficulty} · ${category}` : difficulty,
-    };
-  }),
-  filter: (search, option) => {
-    const haystack = option.value.toLowerCase();
-    return search
-      .toLowerCase()
-      .split(/\s+/)
-      .every((token) => haystack.includes(token));
-  },
-});
-
-if (isCancel(picked)) {
-  cancel("Nothing selected.");
-  process.exit(0);
-}
-
-const proc = Bun.spawn(
-  [
-    // bun installs workspace-dep bins into this package's node_modules, not the root's
-    join(import.meta.dir, "node_modules", ".bin", "leetcode"),
-    "test",
-    join(WORK_DIR, picked),
-  ],
-  { cwd: ROOT, stdio: ["inherit", "inherit", "inherit"] },
-);
-process.exit(await proc.exited);

apps/cli/work.ts

@@ -0,0 +1,180 @@
+/**
+ * The work/ layout: one directory per spaced-repetition window.
+ *
+ *   work/1/<Difficulty>/<Category>/<num>.<slug>.<ext>   first solve
+ *   work/3/<Difficulty>/<Category>/<num>.<slug>.<ext>   3-day blind re-solve
+ *   work/7/<Difficulty>/<Category>/<num>.<slug>.<ext>   7-day blind re-solve
+ *
+ * The bucket name is the review window in days — the same +3/+7 windows the
+ * campaign's `Spaced Repetition — <date>` issues use (WINDOWS in
+ * spaced-repetition.ts). Below the bucket the layout is leetcode-cli's own
+ * `workDir/Difficulty/Category/` shape, so a re-solve lands beside its first
+ * solve under a different bucket.
+ *
+ * A window is *owed* when the first solve is at least that many days old and
+ * the bucket has no file for that problem yet. Reconciled from the filesystem
+ * on every run the way close-solved.ts reconciles issues: no state file, no
+ * bookkeeping, and a re-solve closes its window just by existing — presence,
+ * not content, so a stub in work/3 counts as done the same way `bun run pick`
+ * treats a scaffold under work/1 as picked. The first solve is the one place
+ * content is read: an empty scaffold in work/1 owes nothing, it is simply
+ * unsolved (isImplemented() in source.ts, the same gate close-solved.ts uses
+ * before it closes an issue).
+ *
+ * "First solve" is the ET date of the commit that first added the problem's
+ * work/ file — the same push that closes its problem issue and therefore
+ * starts the campaign's +3/+7 windows. An uncommitted solution has no date and
+ * is never owed a review yet: you just solved it. ET dates and the date
+ * arithmetic come from apps/api/src/srs.ts so the local picker and D1 cannot
+ * disagree about what day it is.
+ *
+ * Library: side-effect-free on import — nothing scans or shells out until a
+ * function is called.
+ */
+import { readFileSync } from "node:fs";
+import { join } from "node:path";
+import { WINDOWS, type Window, daysBetween } from "../api/src/srs.ts";
+import { isImplemented } from "./source.ts";
+
+export const ROOT = join(import.meta.dir, "..", "..");
+export const WORK = join(ROOT, "work");
+
+// The windows are the SRS ladder's rungs: srs.ts defines them once and the
+// bucket directories are named after them. Re-exported so the picker needs
+// only this module to know the work/ layout.
+export { WINDOWS, type Window };
+
+/** work/1 is the first solve, the rest are the review windows. */
+export const BUCKETS = [1, ...WINDOWS] as const;
+export type Bucket = (typeof BUCKETS)[number];
+const BUCKET_BY_DIR: Record<string, Bucket> = { "1": 1, "3": 3, "7": 7 };
+
+export function bucketDir(bucket: Bucket): string {
+  return join(WORK, String(bucket));
+}
+
+export interface WorkFile {
+  lc: number;
+  slug: string;
+  bucket: Bucket;
+  /** Path relative to work/, bucket included. */
+  rel: string;
+  difficulty: string;
+  category: string;
+}
+
+/** `<num>.<slug>.<ext>` — the only file name the campaign scripts parse. */
+function parseName(name: string): { lc: number; slug: string } | null {
+  const m = name.match(/^(\d+)\.(.+)\.[A-Za-z0-9]+$/);
+  return m ? { lc: Number(m[1]), slug: m[2]! } : null;
+}
+
+/** Parse `1/Medium/Array/15.3sum.py` — null for anything off-layout. */
+export function parseWorkPath(rel: string): WorkFile | null {
+  const parts = rel.split("/");
+  const name = parts.pop();
+  const bucket = BUCKET_BY_DIR[parts[0] ?? ""];
+  if (name === undefined || bucket === undefined) return null;
+  const parsed = parseName(name);
+  if (!parsed) return null;
+  return { ...parsed, bucket, rel, difficulty: parts[1] ?? "", category: parts[2] ?? "" };
+}
+
+/** LC number -> its files in that bucket (a problem may have both js and py). */
+export function scanBucket(bucket: Bucket): Map<number, WorkFile[]> {
+  const files = new Map<number, WorkFile[]>();
+  for (const name of new Bun.Glob("**/*.*").scanSync({ cwd: bucketDir(bucket) })) {
+    const file = parseWorkPath(`${bucket}/${name}`);
+    if (!file) continue;
+    const found = files.get(file.lc);
+    if (found) found.push(file);
+    else files.set(file.lc, [file]);
+  }
+  return files;
+}
+
+/**
+ * LC number -> ET date of the commit that first added a work/ file for it.
+ *
+ * One `git log` over the whole of work/, oldest commit first, so the first
+ * date seen for a problem wins. Keyed by LC number rather than by path, which
+ * makes every past reshuffle of the directory layout — including the move into
+ * work/1 — irrelevant: the original add still counts. TZ + `format-local`
+ * put the dates on the ET calendar srs.ts speaks.
+ */
+export function firstSolved(): Map<number, string> {
+  const git = Bun.spawnSync(
+    [
+      "git",
+      "log",
+      "--reverse",
+      "--no-merges",
+      "--diff-filter=A",
+      "--date=format-local:%Y-%m-%d",
+      "--format=%ad",
+      "--name-only",
+      "--",
+      "work",
+    ],
+    { cwd: ROOT, env: { ...process.env, TZ: "America/New_York" } },
+  );
+  if (git.exitCode !== 0) {
+    throw new Error(`git log failed: ${git.stderr.toString().trim()}`);
+  }
+
+  const dates = new Map<number, string>();
+  let date = "";
+  for (const line of git.stdout.toString().split("\n")) {
+    if (/^\d{4}-\d{2}-\d{2}$/.test(line)) {
+      date = line;
+      continue;
+    }
+    const parsed = line === "" ? null : parseName(line.slice(line.lastIndexOf("/") + 1));
+    if (parsed && !dates.has(parsed.lc)) dates.set(parsed.lc, date);
+  }
+  return dates;
+}
+
+export interface Owed extends WorkFile {
+  /** ET date of the first solve. */
+  solved: string;
+  /** Days since the first solve — at least the window. */
+  days: number;
+}
+
+/**
+ * Both review windows for `today`, oldest solve first.
+ *
+ * Uncapped, unlike the review issue's WINDOW_CAP: the issue is one day's
+ * assignment, this is everything still owed. A window skipped for a day stays
+ * on the list until its file exists.
+ */
+export function reviewQueues(today: string): Map<Window, Owed[]> {
+  const dates = firstSolved();
+
+  // An empty scaffold under work/1 is a problem still unsolved, not one owing
+  // a review — the same call close-solved.ts makes before it closes an issue.
+  const solved: { file: WorkFile; date: string }[] = [];
+  for (const files of scanBucket(1).values()) {
+    const date = dates.get(files[0]!.lc);
+    if (date === undefined) continue; // uncommitted: you only just solved it
+    const file = files.find((f) =>
+      isImplemented(readFileSync(join(WORK, f.rel), "utf8"), f.rel.endsWith(".py") ? "py" : "js"),
+    );
+    if (file) solved.push({ file, date });
+  }
+
+  const queues = new Map<Window, Owed[]>();
+  for (const window of WINDOWS) {
+    const done = scanBucket(window);
+    const owed: Owed[] = [];
+    for (const { file, date } of solved) {
+      if (done.has(file.lc)) continue;
+      const days = daysBetween(date, today);
+      if (days >= window) owed.push({ ...file, solved: date, days });
+    }
+    owed.sort((a, b) => b.days - a.days || a.lc - b.lc);
+    queues.set(window, owed);
+  }
+  return queues;
+}

apps/docs/content/(array)/150-evaluate-reverse-polish-notation.mdx

@@ -0,0 +1,55 @@
+---
+title: '150. Evaluate Reverse Polish Notation'
+description: You are given an array of strings tokens that represents an arithmetic expression in a Reverse Polish Notation
+sidebar:
+  label: 'Evaluate Reverse Polish Notation'
+  badge: 'Medium'
+---
+
+<Badge variant="accent">Stack</Badge>
+
+### Example 1:
+- Input: `tokens = ["2","1","+","3","*"]`
+- Output: `9`
+- Explanation: `((2 + 1`) * `3`) = `9`
+
+### Example 2:
+- Input: `tokens = ["4","13","5","/","+"]`
+- Output: `6`
+- Explanation: `(4 + (13 / 5`)) = `6`
+
+### Example 3:
+- Input: `tokens = ["10","6","9","3","+","-11","*","/","*","17","+","5","+"]`
+- Output: `22`
+- Explanation: `((10 * (6 / ((9 + 3`) * `-11`))) + `17`) + `5 = ((10 * (6 / (12 * -11`))) + `17`) + `5 = ((10 * (6 / -132`)) + `17`) + `5 = ((10 * 0`) + `17`) + `5 = (0 + 17`) + `5 = 17 + 5 = 22`
+
+### Constraints:
+
+- `1 <= tokens.length <= 10^4`
+- `tokens[i]` is either an operator: "+", "-", "*", or "/", or an integer in the range [-200, 200].
+
+## Solution
+
+```py
+class Solution:
+    def evalRPN(self, tokens: List[str]) -> int:
+        stack = []
+        operations = {
+            "+": lambda x, y: int(x + y),
+            "-": lambda x, y: int(x - y),
+            "*": lambda x, y: int(x * y),
+            "/": lambda x, y: int(x / y),
+        }
+
+        for c in tokens:
+            if c in operations:
+                y = stack.pop()
+                x = stack.pop()
+                calc_func = operations[c]
+                result = calc_func(x, y)
+                stack.append(result)
+            else:
+                stack.append(int(c))
+
+        return stack[0]
+```

apps/docs/content/(array)/153-find-minimum-in-rotated-sorted-array.mdx

@@ -0,0 +1,55 @@
+---
+title: '153. Find Minimum in Rotated Sorted Array'
+description: 'Suppose an array of length n sorted in ascending order is rotated between 1 and n times. For example, the array nums = [0,1,2,4,5,6,7] might become:'
+sidebar:
+  label: 'Find Minimum in Rotated Sorted Array'
+  badge: 'Medium'
+---
+
+<Badge variant="accent">Binary Search</Badge>
+
+::::warning
+Notice that rotating an array [a[0], a[1], a[2], ..., a[n-1]] 1 time results in the array [a[n-1], a[0], a[1], a[2], ..., a[n-2]].
+::::
+
+### Example 1:
+- Input: `nums = [3,4,5,1,2]`
+- Output: `1`
+- Explanation: The original array was `[1,2,3,4,5]` rotated `3` times.
+
+### Example 2:
+- Input: `nums = [4,5,6,7,0,1,2]`
+- Output: `0`
+- Explanation: The original array was `[0,1,2,4,5,6,7]` and it was rotated `4` times.
+
+### Example 3:
+- Input: `nums = [11,13,15,17]`
+- Output: `11`
+- Explanation: The original array was `[11,13,15,17]` and it was rotated `4` times.
+
+### Constraints:
+
+- `n == nums.length`
+- `1 <= n <= 5000`
+- `-5000 <= nums[i] <= 5000`
+- All the integers of `nums` are unique.
+- `nums` is sorted and rotated between 1 and `n` times.
+
+## Solution
+
+```py
+class Solution:
+    def findMin(self, nums: List[int]) -> int:
+        l, r = 0, len(nums) - 1
+        lowest_index = -1
+
+        while l <= r:
+            m = (l + r) // 2
+            if nums[m] <= nums[-1]:
+                lowest_index = m
+                r = m - 1
+            else:
+                l = m + 1
+
+        return nums[lowest_index]
+```

apps/docs/content/(array)/189-rotate-array.mdx

@@ -1,42 +0,0 @@
----
-title: '189. Rotate Array'
-description: Given an integer array nums, rotate the array to the right by k steps, where k is non-negative
-sidebar:
-  label: 'Rotate Array'
-  badge: 'Medium'
----
-
-<Badge variant="accent">Two Pointers</Badge>
-
-::::warning
-Try to come up with as many solutions as you can. There are at least three different ways to solve this problem. Could you do it in-place with `O(1)` extra space?
-::::
-
-### Example 1:
-- Input: `nums = [1,2,3,4,5,6,7], k = 3`
-- Output: `[5,6,7,1,2,3,4]`
-- Explanation: rotate 1 steps to the right: `[7,1,2,3,4,5,6]` rotate 2 steps to the right: `[6,7,1,2,3,4,5]` rotate 3 steps to the right: `[5,6,7,1,2,3,4]`
-
-### Example 2:
-- Input: `nums = [-1,-100,3,99], k = 2`
-- Output: `[3,99,-1,-100]`
-- Explanation: rotate 1 steps to the right: `[99,-1,-100,3]` rotate 2 steps to the right: `[3,99,-1,-100]`
-
-### Constraints:
-
-- `1 <= nums.length <= 10^5`
-- `-2^31 <= nums[i] <= 2^31 - 1`
-- `0 <= k <= 10^5`
-
-## Solution
-
-```js
-/**
- * @param {number[]} nums
- * @param {number} k
- * @return {void} Do not return anything, modify nums in-place instead.
- */
-var rotate = function(nums, k) {
-    
-};
-```

apps/docs/content/(array)/2090-k-radius-subarray-averages.mdx

@@ -1,50 +0,0 @@
----
-title: '2090. K Radius Subarray Averages'
-description: You are given a 0-indexed array nums of n integers, and an integer k
-sidebar:
-  label: 'K Radius Subarray Averages'
-  badge: 'Medium'
----
-
-<Badge variant="accent">Array</Badge>
-
-### Example 1:
-- Input: `nums = [7,4,3,9,1,8,5,2,6], k = 3`
-- Output: `[-1,-1,-1,5,4,4,-1,-1,-1]`
-- Explanation:
-  - `avg[0]`, `avg[1]`, and `avg[2]` are `-1` because there are less than `k` elements before each index.
-  - The sum of the subarray centered at index `3` with radius `3` is: `7 + 4 + 3 + 9 + 1 + 8 + 5 = 37`. Using integer division, `avg[3] = 37 / 7 = 5`.
-  - For the subarray centered at index `4`, `avg[4] = (4 + 3 + 9 + 1 + 8 + 5 + 2) / 7 = 4`.
-  - For the subarray centered at index `5`, `avg[5] = (3 + 9 + 1 + 8 + 5 + 2 + 6) / 7 = 4`.
-  - `avg[6]`, `avg[7]`, and `avg[8]` are `-1` because there are less than `k` elements after each index.
-
-### Example 2:
-- Input: `nums = [100000], k = 0`
-- Output: `[100000]`
-- Explanation:
-  - The sum of the subarray centered at index `0` with radius `0` is: `100000`. `avg[0] = 100000 / 1 = 100000`.
-
-### Example 3:
-- Input: `nums = [8], k = 100000`
-- Output: `[-1]`
-- Explanation:
-  - `avg[0]` is `-1` because there are less than `k` elements before and after index `0`.
-
-### Constraints:
-
-- `n == nums.length`
-- `1 <= n <= 10^5`
-- `0 <= nums[i], k <= 10^5`
-
-## Solution
-
-```js
-/**
- * @param {number[]} nums
- * @param {number} k
- * @return {number[]}
- */
-var getAverages = function(nums, k) {
-    
-};
-```

apps/docs/content/(array)/35-search-insert-position.mdx

@@ -0,0 +1,51 @@
+---
+title: '35. Search Insert Position'
+description: Given a sorted array of distinct integers and a target value, return the index if the target is found. If not, return the index where it would be if it were inserted in order
+sidebar:
+  label: 'Search Insert Position'
+  badge: 'Easy'
+---
+
+<Badge variant="accent">Binary Search</Badge>
+
+::::warning
+You must write an algorithm with O(log n) runtime complexity.
+::::
+
+### Example 1:
+- Input: `nums = [1,3,5,6], target = 5`
+- Output: `2`
+
+### Example 2:
+- Input: `nums = [1,3,5,6], target = 2`
+- Output: `1`
+
+### Example 3:
+- Input: `nums = [1,3,5,6], target = 7`
+- Output: `4`
+
+### Constraints:
+
+- `1 <= nums.length <= 10^4`
+- `-10^4 <= nums[i] <= 10^4`
+- `nums` contains distinct values sorted in ascending order.
+- `-10^4 <= target <= 10^4`
+
+## Solution
+
+```py
+class Solution:
+    def searchInsert(self, nums: List[int], target: int) -> int:
+        l, r = 0, len(nums) - 1
+
+        while l <= r:
+            m = (l + r) // 2
+            if nums[m] == target:
+                return m
+            elif nums[m] < target:
+                l = m + 1
+            elif nums[m] > target:
+                r = m - 1
+
+        return (l + r) // 2 + 1
+```

apps/docs/content/(array)/42-trapping-rain-water.mdx

@@ -1,36 +0,0 @@
----
-title: '42. Trapping Rain Water'
-description: Given n non-negative integers representing an elevation map where the width of each bar is 1, compute how much water it can trap after raining
-sidebar:
-  label: 'Trapping Rain Water'
-  badge: 'Hard'
----
-
-<Badge variant="accent">Two Pointers</Badge>
-
-### Example 1:
-- Input: `height = [0,1,0,2,1,0,1,3,2,1,2,1]`
-- Output: `6`
-- Explanation: The above elevation map (black section) is represented by array `[0,1,0,2,1,0,1,3,2,1,2,1]`. In this case, `6` units of rain water (blue section) are being trapped.
-
-### Example 2:
-- Input: `height = [4,2,0,3,2,5]`
-- Output: `9`
-
-### Constraints:
-
-- `n == height.length`
-- `1 <= n <= 2 * 10^4`
-- `0 <= height[i] <= 10^5`
-
-## Solution
-
-```js
-/**
- * @param {number[]} height
- * @return {number}
- */
-var trap = function(height) {
-    
-};
-```

apps/docs/content/(array)/739-daily-temperatures.mdx

@@ -0,0 +1,41 @@
+---
+title: '739. Daily Temperatures'
+description: Given an array of integers temperatures represents the daily temperatures, return an array answer such that answer[i] is the number of days you have to wait after the i^th day to get a warmer temperature. If there is no future day for which this is possible, keep answer[i] == 0 instead
+sidebar:
+  label: 'Daily Temperatures'
+  badge: 'Medium'
+---
+
+<Badge variant="accent">Monotonic Stack</Badge>
+
+### Example 1:
+- Input: `temperatures = [73,74,75,71,69,72,76,73]`
+- Output: `[1,1,4,2,1,1,0,0]`
+
+### Example 2:
+- Input: `temperatures = [30,40,50,60]`
+- Output: `[1,1,1,0]`
+
+### Example 3:
+- Input: `temperatures = [30,60,90]`
+- Output: `[1,1,0]`
+
+### Constraints:
+
+- `1 <= temperatures.length <= 10^5`
+- `30 <= temperatures[i] <= 100`
+
+## Solution
+
+```py
+class Solution:
+    def dailyTemperatures(self, temperatures: List[int]) -> List[int]:
+        ans = [0] * len(temperatures)
+        stack = []
+        for i, temp in enumerate(temperatures):
+            while stack and temperatures[stack[-1]] < temp:
+                prev = stack.pop()
+                ans[prev] = i - prev
+            stack.append(i)
+        return ans
+```

apps/docs/content/(array)/74-search-a-2d-matrix.mdx

@@ -0,0 +1,61 @@
+---
+title: '74. Search a 2D Matrix'
+description: 'You are given an m x n integer matrix matrix with the following two properties:'
+sidebar:
+  label: 'Search a 2D Matrix'
+  badge: 'Medium'
+---
+
+<Badge variant="accent">Binary Search</Badge>
+
+::::warning
+You must write a solution in O(log(m * n)) time complexity.
+::::
+
+### Example 1:
+- Input: `matrix = [[1,3,5,7],[10,11,16,20],[23,30,34,60]], target = 3`
+- Output: `true`
+
+### Example 2:
+- Input: `matrix = [[1,3,5,7],[10,11,16,20],[23,30,34,60]], target = 13`
+- Output: `false`
+
+### Constraints:
+
+- `m == matrix.length`
+- `n == matrix[i].length`
+- `1 <= m, n <= 100`
+- `-10^4 <= matrix[i][j], target <= 10^4`
+
+## Solution
+
+```py
+class Solution:
+    def searchMatrix(self, matrix: List[List[int]], target: int) -> bool:
+        ROWS, COLS = len(matrix), len(matrix[0])
+
+        top, bot = 0, ROWS - 1
+        while top <= bot:
+            row = (top + bot) // 2
+            if target > matrix[row][-1]:
+                top = row + 1
+            elif target < matrix[row][0]:
+                bot = row - 1
+            else:
+                break
+
+        if not (top <= bot):
+            return False
+
+        row = (top + bot) // 2
+        l, r = 0, COLS - 1
+        while l <= r:
+            m = (l + r) // 2
+            if target > matrix[row][m]:
+                l = m + 1
+            elif target < matrix[row][m]:
+                r = m - 1
+            else:
+                return True
+        return False
+```

apps/docs/content/(array)/853-car-fleet.mdx

@@ -0,0 +1,47 @@
+---
+title: '853. Car Fleet'
+description: There are n cars at given miles away from the starting mile 0, traveling to reach the mile target
+sidebar:
+  label: 'Car Fleet'
+  badge: 'Medium'
+---
+
+<Badge variant="accent">Monotonic Stack</Badge>
+
+### Example 1:
+- Input: `target = 12, position = [10,8,0,5,3], speed = [2,4,1,1,3]`
+- Output: `3`
+- Explanation: • The cars starting at `10 (speed 2`) and `8 (speed 4`) become a fleet, meeting each other at `12`. The fleet forms at `target`. • The car starting at `0 (speed 1`) does not catch up to any other car, so it is a fleet by itself. • The cars starting at `5 (speed 1`) and `3 (speed 3`) become a fleet, meeting each other at `6`. The fleet moves at `speed 1` until it reaches `target`.
+
+### Example 2:
+- Input: `target = 10, position = [3], speed = [3]`
+- Output: `1`
+- Explanation: There is only one car, hence there is only one fleet.
+
+### Example 3:
+- Input: `target = 100, position = [0,2,4], speed = [4,2,1]`
+- Output: `1`
+- Explanation: • The cars starting at `0 (speed 4`) and `2 (speed 2`) become a fleet, meeting each other at `4`. The car starting at `4 (speed 1`) travels to `5`. • Then, the fleet at `4 (speed 2`) and the car at `position 5 (speed 1`) become one fleet, meeting each other at `6`. The fleet moves at `speed 1` until it reaches `target`.
+
+### Constraints:
+
+- `n == position.length == speed.length`
+- `1 <= n <= 10^5`
+- `0 < target <= 10^6`
+- `0 <= position[i] < target`
+- All the values of `position` are unique.
+- `0 < speed[i] <= 10^6`
+
+## Solution
+
+```py
+class Solution:
+    def carFleet(self, target: int, position: List[int], speed: List[int]) -> int:
+        stack = []
+        for pos, spd in sorted(zip(position, speed), reverse=True):
+            time = (target - pos) / spd
+            if not stack or time > stack[-1]:
+                stack.append(time)
+
+        return len(stack)
+```

apps/docs/content/(hash-table)/141-linked-list-cycle.mdx

@@ -0,0 +1,56 @@
+---
+title: '141. Linked List Cycle'
+description: Given head, the head of a linked list, determine if the linked list has a cycle in it
+sidebar:
+  label: 'Linked List Cycle'
+  badge: 'Easy'
+---
+
+<Badge variant="accent">Linked List</Badge>
+
+::::warning
+Can you solve it using O(1) (i.e. constant) memory?
+::::
+
+### Example 1:
+- Input: `head = [3,2,0,-4], pos = 1`
+- Output: `true`
+- Explanation: There is a cycle in the linked list, where the tail connects to the 1st node (0-indexed).
+
+### Example 2:
+- Input: `head = [1,2], pos = 0`
+- Output: `true`
+- Explanation: There is a cycle in the linked list, where the tail connects to the 0th node.
+
+### Example 3:
+- Input: `head = [1], pos = -1`
+- Output: `false`
+- Explanation: There is no cycle in the linked list.
+
+### Constraints:
+
+- The number of the nodes in the list is in the range [0, 10^4].
+- `-10^5 <= Node.val <= 10^5`
+- pos is -1 or a valid index in the linked-list.
+
+## Solution
+
+```py
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.next = None
+
+
+class Solution:
+    def hasCycle(self, head: Optional[ListNode]) -> bool:
+        fast = slow = head
+
+        while fast and fast.next:
+            fast = fast.next.next
+            slow = slow.next
+            if fast is slow:
+                return True
+        return False
+```

apps/docs/content/(linked-list)/206-reverse-linked-list.mdx

@@ -0,0 +1,50 @@
+---
+title: '206. Reverse Linked List'
+description: Given the head of a singly linked list, reverse the list, and return the reversed list
+sidebar:
+  label: 'Reverse Linked List'
+  badge: 'Easy'
+---
+
+<Badge variant="accent">Linked List</Badge>
+
+::::warning
+A linked list can be reversed either iteratively or recursively. Could you implement both?
+::::
+
+### Example 1:
+- Input: `head = [1,2,3,4,5]`
+- Output: `[5,4,3,2,1]`
+
+### Example 2:
+- Input: `head = [1,2]`
+- Output: `[2,1]`
+
+### Example 3:
+- Input: `head = []`
+- Output: `[]`
+
+### Constraints:
+
+- The number of nodes in the list is the range [0, 5000].
+- `-5000 <= Node.val <= 5000`
+
+## Solution
+
+```py
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def reverseList(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        prev = None
+        curr = head
+        while curr:
+            next_ = curr.next
+            curr.next = prev
+            prev = curr
+            curr = next_
+        return prev
+```

apps/docs/content/(linked-list)/21-merge-two-sorted-lists.mdx

@@ -0,0 +1,66 @@
+---
+title: '21. Merge Two Sorted Lists'
+description: You are given the heads of two sorted linked lists list1 and list2
+sidebar:
+  label: 'Merge Two Sorted Lists'
+  badge: 'Easy'
+---
+
+<Badge variant="accent">Linked List</Badge>
+
+### Example 1:
+- Input: `list1 = [1,2,4], list2 = [1,3,4]`
+- Output: `[1,1,2,3,4,4]`
+
+### Example 2:
+- Input: `list1 = [], list2 = []`
+- Output: `[]`
+
+### Example 3:
+- Input: `list1 = [], list2 = [0]`
+- Output: `[0]`
+
+### Constraints:
+
+- The number of nodes in both lists is in the range [0, 50].
+- `-100 <= Node.val <= 100`
+- Both list1 and list2 are sorted in non-decreasing order.
+
+## Solution
+
+```py
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def mergeTwoLists(
+        self, list1: Optional[ListNode], list2: Optional[ListNode]
+    ) -> Optional[ListNode]:
+
+        if not list1:
+            return list2
+        if not list2:
+            return list1
+
+        if list1.val < list2.val:
+            head = list1
+            list1 = list1.next
+        else:
+            head = list2
+            list2 = list2.next
+
+        current = head
+        while list1 and list2:
+            if list1.val < list2.val:
+                current.next = list1
+                list1 = list1.next
+            else:
+                current.next = list2
+                list2 = list2.next
+            current = current.next
+
+        current.next = list1 or list2
+        return head
+```

apps/docs/content/(stack)/155-min-stack.mdx

@@ -0,0 +1,56 @@
+---
+title: '155. Min Stack'
+description: Design a stack that supports push, pop, top, and retrieving the minimum element in constant time
+sidebar:
+  label: 'Min Stack'
+  badge: 'Medium'
+---
+
+<Badge variant="accent">Stack</Badge>
+
+::::warning
+You must implement a solution with O(1) time complexity for each function.
+::::
+
+### Example 1:
+- Input: ``
+- Output: ``
+- Explanation: Input `["MinStack","push","push","push","getMin","pop","top","getMin"]` [[],[-2],[0],[-3],[],[],[],[]] Output `[null,null,null,null,-3,null,0,-2]` Explanation MinStack minStack = new MinStack(); minStack.push(-2); minStack.push(0); minStack.push(-3); minStack.getMin(); // return `-3` minStack.pop(); minStack.top();    // return `0` minStack.getMin(); // return `-2`
+
+### Constraints:
+
+- `-2^31 <= val <= 2^31 - 1`
+- Methods pop, top and getMin operations will always be called on non-empty stacks.
+- At most 3 * 10^4 calls will be made to push, pop, top, and getMin.
+
+## Solution
+
+```py
+class MinStack:
+    def __init__(self):
+        self.stack = []
+        self.minStack = []
+
+    def push(self, value: int) -> None:
+        self.stack.append(value)
+        value = min(value, self.minStack[-1] if self.minStack else value)
+        self.minStack.append(value)
+
+    def pop(self) -> None:
+        self.stack.pop()
+        self.minStack.pop()
+
+    def top(self) -> int:
+        return self.stack[-1]
+
+    def getMin(self) -> int:
+        return self.minStack[-1]
+
+
+# Your MinStack object will be instantiated and called as such:
+# obj = MinStack()
+# obj.push(value)
+# obj.pop()
+# param_3 = obj.top()
+# param_4 = obj.getMin()
+```

apps/docs/content/(string)/20-valid-parentheses.mdx

@@ -0,0 +1,54 @@
+---
+title: '20. Valid Parentheses'
+description: Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid
+sidebar:
+  label: 'Valid Parentheses'
+  badge: 'Easy'
+---
+
+<Badge variant="accent">Stack</Badge>
+
+### Example 1:
+- Input: `s = "()"`
+- Output: `true`
+
+### Example 2:
+- Input: `s = "()[]{}"`
+- Output: `true`
+
+### Example 3:
+- Input: `s = "(]"`
+- Output: `false`
+
+### Example 4:
+- Input: `s = "([])"`
+- Output: `true`
+
+### Example 5:
+- Input: `s = "([)]"`
+- Output: `false`
+
+### Constraints:
+
+- `1 <= s.length <= 10^4`
+- `s` consists of parentheses only '()[]{}'.
+
+## Solution
+
+```py
+class Solution:
+    def isValid(self, s: str) -> bool:
+        stack = []
+        pairs = {")": "(", "]": "[", "}": "{"}
+
+        for c in s:
+            if c in pairs:
+                if stack and pairs[c] == stack[-1]:
+                    stack.pop()
+                else:
+                    return False
+            else:
+                stack.append(c)
+
+        return True if not stack else False
+```

apps/docs/islands/ProgressDashboard.tsx

@@ -17,7 +17,9 @@ const API_BASE = "https://srs-api.prdlk.workers.dev";
 
 // ── /api/stats response shape ────────────────────────────────────
 
-const STAGES = ["new", "+2", "+5", "+10", "retired"] as const;
+// Mirrors STAGES in apps/api/src/srs.ts — the ladder rungs, in order. The
+// Worker ships every rung in `ladder`, zeros included.
+const STAGES = ["new", "+3", "+7", "retired"] as const;
 
 type Stage = (typeof STAGES)[number];
 
@@ -35,6 +37,7 @@ interface Stats {
     deferred_total: number;
   }[];
   ladder: Record<Stage, number>;
+  /** week is the 1-based campaign week — the Worker converts from ISO. */
   gates: {
     week: number;
     issue: number | null;
@@ -76,7 +79,12 @@ function dayLabel(iso: string): string {
   return `${weekday} ${iso.slice(8)}`;
 }
 
-// ── shared styles (theme tokens only — no hand-rolled palette) ───
+// ── shared styles ────────────────────────────────────────────────
+// Theme tokens only, with two deliberate exceptions: the phase-bar sets get
+// fixed hues (accent-blue core, yellow optional, red deferred — they must be
+// distinguishable, not shades of one colour), and the last-7-days heatmap
+// reuses the GREENS ramp from apps/api/src/charts.ts so the page matches the
+// README/email heatmaps (level 0 stays a theme token so light mode works).
 
 const card: CSSProperties = {
   border: "1px solid var(--blume-border)",
@@ -142,32 +150,78 @@ function Header({ stats }: { stats: Stats }) {
   );
 }
 
+// One stacked bar per phase: solved core / optional / deferred segments over
+// a muted track sized by the phase's total problem count, so both phase size
+// and progress read at a glance.
+const SETS = [
+  ["core", "var(--blume-accent)"],
+  ["optional", "#d29922"],
+  ["deferred", "#e5534b"],
+] as const;
+
 function Phases({ stats }: { stats: Stats }) {
+  const maxTotal = Math.max(
+    1,
+    ...stats.phases.map((p) => p.core_total + p.optional_total + p.deferred_total),
+  );
   return (
     <div style={card}>
       <div style={heading}>Phases</div>
-      <table style={{ borderCollapse: "collapse", width: "100%" }}>
+      <div style={{ display: "flex", gap: "1rem", flexWrap: "wrap", marginBottom: "0.6rem" }}>
-        <tbody>
+        {SETS.map(([set, color]) => (
-          {stats.phases.map((p) => (
+          <span key={set} style={muted}>
-            <tr key={p.milestone}>
+            <span
-              <td style={{ padding: "0.2rem 1rem 0.2rem 0" }}>{p.name}</td>
+              style={{
-              <td style={{ padding: "0.2rem 1rem 0.2rem 0" }}>
+                display: "inline-block",
-                <Bar done={p.core_done} total={p.core_total} />{" "}
+                width: "0.65rem",
-                <span style={muted}>
+                height: "0.65rem",
-                  core {p.core_done}/{p.core_total}
+                borderRadius: "2px",
-                </span>
+                background: color,
-              </td>
+                marginRight: "0.35rem",
-              <td style={{ padding: "0.2rem 0" }}>
+              }}
-                <span style={muted}>
+            />
-                  optional {p.optional_done}/{p.optional_total}
+            {set}
-                  {p.deferred_total > 0 &&
+          </span>
-                    ` · deferred ${p.deferred_done}/${p.deferred_total}`}
+        ))}
-                </span>
+      </div>
-              </td>
+      {stats.phases.map((p) => {
-            </tr>
+        const total = p.core_total + p.optional_total + p.deferred_total;
-          ))}
+        const done = p.core_done + p.optional_done + p.deferred_done;
-        </tbody>
+        return (
-      </table>
+          <div
+            key={p.milestone}
+            title={`core ${p.core_done}/${p.core_total} · optional ${p.optional_done}/${p.optional_total} · deferred ${p.deferred_done}/${p.deferred_total}`}
+            style={{ display: "flex", alignItems: "center", gap: "0.75rem", padding: "0.25rem 0" }}
+          >
+            <span style={{ width: "9.5rem", flexShrink: 0 }}>{p.name}</span>
+            <span style={{ flex: 1 }}>
+              <span
+                style={{
+                  display: "flex",
+                  width: `${(total / maxTotal) * 100}%`,
+                  height: "0.65rem",
+                  borderRadius: "var(--blume-radius)",
+                  background: "var(--blume-muted)",
+                  overflow: "hidden",
+                }}
+              >
+                {SETS.map(([set, color]) => {
+                  const solved = p[`${set}_done`];
+                  return solved > 0 ? (
+                    <span
+                      key={set}
+                      style={{ width: `${(solved / total) * 100}%`, background: color }}
+                    />
+                  ) : null;
+                })}
+              </span>
+            </span>
+            <span style={{ ...muted, width: "3.5rem", textAlign: "right", flexShrink: 0 }}>
+              {done}/{total}
+            </span>
+          </div>
+        );
+      })}
     </div>
   );
 }
@@ -224,76 +278,95 @@ function Gates({ stats }: { stats: Stats }) {
     <div style={card}>
       <div style={heading}>Gate log</div>
       {stats.gates.length === 0 ? (
-        <span style={muted}>No gates yet.</span>
+        <span style={muted}>No gates yet — the first weekly review opens Saturday night.</span>
       ) : (
-        <table style={{ borderCollapse: "collapse", width: "100%" }}>
+        stats.gates.map((g) => (
-          <thead>
+          <div
-            <tr>
+            key={g.week}
-              {["Week", "Issue", "Pass rate", "Closed"].map((h) => (
+            style={{
-                <th key={h} style={{ ...muted, textAlign: "left", padding: "0.2rem 1rem 0.2rem 0" }}>
+              display: "flex",
-                  {h}
+              gap: "0.75rem",
-                </th>
+              alignItems: "baseline",
-              ))}
+              flexWrap: "wrap",
-            </tr>
+              padding: "0.15rem 0",
-          </thead>
+            }}
-          <tbody>
+          >
-            {stats.gates.map((g) => (
+            <span style={{ width: "4.5rem", flexShrink: 0 }}>Week {g.week}</span>
-              <tr key={g.week}>
+            {g.issue === null ? (
-                <td style={{ padding: "0.2rem 1rem 0.2rem 0" }}>{g.week}</td>
+              <span style={muted}>no review issue</span>
-                <td style={{ padding: "0.2rem 1rem 0.2rem 0" }}>
+            ) : (
-                  {g.issue === null ? (
+              <a
-                    <span style={muted}>—</span>
+                href={`https://github.com/prdlk/leetcode/issues/${g.issue}`}
-                  ) : (
+                target="_blank"
-                    <a
+                rel="noreferrer"
-                      href={`https://github.com/prdlk/leetcode/issues/${g.issue}`}
+              >
-                      target="_blank"
+                #{g.issue}
-                      rel="noreferrer"
+              </a>
-                    >
+            )}
-                      #{g.issue}
+            {g.pass_rate === null ? (
-                    </a>
+              <span style={muted}>in progress</span>
-                  )}
+            ) : (
-                </td>
+              <span>
-                <td style={{ padding: "0.2rem 1rem 0.2rem 0" }}>
+                {percent(g.pass_rate)} passed
-                  {g.pass_rate === null ? (
+                {g.closed_on && <span style={muted}> · closed {g.closed_on}</span>}
-                    <span style={muted}>open</span>
+              </span>
-                  ) : (
+            )}
-                    percent(g.pass_rate)
+          </div>
-                  )}
+        ))
-                </td>
-                <td style={{ padding: "0.2rem 0" }}>
-                  {g.closed_on ?? <span style={muted}>—</span>}
-                </td>
-              </tr>
-            ))}
-          </tbody>
-        </table>
       )}
+      <div style={{ ...muted, marginTop: "0.4rem" }}>
+        One gate per campaign week — scored when its review issue closes.
+      </div>
     </div>
   );
 }
 
+// GREENS ramp from apps/api/src/charts.ts; level 0 swapped for the theme's
+// muted token so an empty day looks right in both colour schemes.
+const GREENS = [
+  "var(--blume-muted)",
+  "#0e4429",
+  "#006d32",
+  "#26a641",
+  "#39d353",
+];
+
 function Recent({ stats }: { stats: Stats }) {
   return (
     <div style={card}>
       <div style={heading}>Last 7 days</div>
-      <div style={{ display: "flex", gap: "0.5rem", flexWrap: "wrap" }}>
+      <div style={{ display: "flex", gap: "0.4rem", flexWrap: "wrap" }}>
         {stats.recent.map((r) => (
           <span
             key={r.date}
-            style={{
+            title={`${r.date}: ${r.passes}/${r.attempts} passed`}
-              border: "1px solid var(--blume-border)",
+            style={{ textAlign: "center" }}
-              borderRadius: "var(--blume-radius)",
-              padding: "0.35rem 0.6rem",
-              textAlign: "center",
-            }}
           >
-            <span style={{ ...muted, display: "block" }}>{dayLabel(r.date)}</span>
+            <span
-            <strong>{r.passes}</strong>
+              style={{
-            <span style={muted}>/{r.attempts}</span>
+                display: "block",
+                width: "2.6rem",
+                height: "2rem",
+                borderRadius: "var(--blume-radius)",
+                background: GREENS[Math.min(r.attempts, 4)],
+              }}
+            />
+            <span style={{ ...muted, display: "block", marginTop: "0.25rem", fontSize: "0.75em" }}>
+              {dayLabel(r.date)}
+            </span>
           </span>
         ))}
       </div>
-      <div style={{ ...muted, marginTop: "0.4rem" }}>passes / attempts</div>
+      <div style={{ ...muted, marginTop: "0.5rem", display: "flex", alignItems: "center", gap: "0.25rem" }}>
+        <span>Less</span>
+        {GREENS.map((color) => (
+          <span
+            key={color}
+            style={{ display: "inline-block", width: "0.65rem", height: "0.65rem", borderRadius: "2px", background: color }}
+          />
+        ))}
+        <span>More · colour = attempts, hover for passes</span>
+      </div>
     </div>
   );
 }

package.json

@@ -9,11 +9,14 @@
     "doctor": "cd apps/docs && bun run doctor",
     "close-solved": "bun apps/cli/close-solved.ts",
     "close-topics": "bun apps/cli/close-topics.ts",
+    "sync-project-fields": "bun apps/cli/sync-project-fields.ts",
+    "spaced-repetition": "bun apps/cli/spaced-repetition.ts",
     "api:dev": "cd apps/api && bun run dev",
     "api:deploy": "cd apps/api && bun run deploy",
     "api:test": "cd apps/api && bun test src",
     "pick": "bun apps/cli/pick.ts",
     "sync": "bun apps/cli/sync.ts",
+    "submit": "bun apps/cli/submit.ts",
     "test": "bun apps/cli/test.ts"
   }
 }

work/1/Easy/Array/35.search-insert-position.py

@@ -0,0 +1,58 @@
+"""
+35. Search Insert Position
+Difficulty: Easy
+https://leetcode.com/problems/search-insert-position/
+
+──────────────────────────────────────────────────
+
+Given a sorted array of distinct integers and a target value, return
+the index if the target is found. If not, return the index where it
+would be if it were inserted in order.
+
+You must write an algorithm with O(log n) runtime complexity.
+
+
+
+Example 1:
+
+Input: nums = [1,3,5,6], target = 5
+Output: 2
+
+Example 2:
+
+Input: nums = [1,3,5,6], target = 2
+Output: 1
+
+Example 3:
+
+Input: nums = [1,3,5,6], target = 7
+Output: 4
+
+
+
+Constraints:
+
+        • 1 <= nums.length <= 10^4
+
+        • -10^4 <= nums[i] <= 10^4
+
+        • nums contains distinct values sorted in ascending order.
+
+        • -10^4 <= target <= 10^4
+"""
+
+
+class Solution:
+    def searchInsert(self, nums: List[int], target: int) -> int:
+        l, r = 0, len(nums) - 1
+
+        while l <= r:
+            m = (l + r) // 2
+            if nums[m] == target:
+                return m
+            elif nums[m] < target:
+                l = m + 1
+            elif nums[m] > target:
+                r = m - 1
+
+        return (l + r) // 2 + 1

work/1/Easy/Hash Table/141.linked-list-cycle.py

@@ -0,0 +1,73 @@
+"""
+141. Linked List Cycle
+Difficulty: Easy
+https://leetcode.com/problems/linked-list-cycle/
+
+──────────────────────────────────────────────────
+
+Given head, the head of a linked list, determine if the linked list
+has a cycle in it.
+
+There is a cycle in a linked list if there is some node in the list
+that can be reached again by continuously following the next pointer.
+Internally, pos is used to denote the index of the node that tail's
+next pointer is connected to. Note that pos is not passed as a
+parameter.
+
+Return true if there is a cycle in the linked list. Otherwise, return
+false.
+
+
+
+Example 1:
+
+Input: head = [3,2,0,-4], pos = 1
+Output: true
+Explanation: There is a cycle in the linked list, where the tail
+connects to the 1st node (0-indexed).
+
+Example 2:
+
+Input: head = [1,2], pos = 0
+Output: true
+Explanation: There is a cycle in the linked list, where the tail
+connects to the 0th node.
+
+Example 3:
+
+Input: head = [1], pos = -1
+Output: false
+Explanation: There is no cycle in the linked list.
+
+
+
+Constraints:
+
+        • The number of the nodes in the list is in the range [0, 10^4].
+
+        • -10^5 <= Node.val <= 10^5
+
+        • pos is -1 or a valid index in the linked-list.
+
+
+
+Follow up: Can you solve it using O(1) (i.e. constant) memory?
+"""
+
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.next = None
+
+
+class Solution:
+    def hasCycle(self, head: Optional[ListNode]) -> bool:
+        fast = slow = head
+
+        while fast and fast.next:
+            fast = fast.next.next
+            slow = slow.next
+            if fast is slow:
+                return True
+        return False

work/1/Easy/Linked List/206.reverse-linked-list.py

@@ -0,0 +1,57 @@
+"""
+206. Reverse Linked List
+Difficulty: Easy
+https://leetcode.com/problems/reverse-linked-list/
+
+──────────────────────────────────────────────────
+
+Given the head of a singly linked list, reverse the list, and return
+the reversed list.
+
+
+
+Example 1:
+
+Input: head = [1,2,3,4,5]
+Output: [5,4,3,2,1]
+
+Example 2:
+
+Input: head = [1,2]
+Output: [2,1]
+
+Example 3:
+
+Input: head = []
+Output: []
+
+
+
+Constraints:
+
+        • The number of nodes in the list is the range [0, 5000].
+
+        • -5000 <= Node.val <= 5000
+
+
+
+Follow up: A linked list can be reversed either iteratively or
+recursively. Could you implement both?
+"""
+
+
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def reverseList(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        prev = None
+        curr = head
+        while curr:
+            next_ = curr.next
+            curr.next = prev
+            prev = curr
+            curr = next_
+        return prev

work/1/Easy/Linked List/21.merge-two-sorted-lists.py

@@ -0,0 +1,77 @@
+"""
+21. Merge Two Sorted Lists
+Difficulty: Easy
+https://leetcode.com/problems/merge-two-sorted-lists/
+
+──────────────────────────────────────────────────
+
+You are given the heads of two sorted linked lists list1 and list2.
+
+Merge the two lists into one sorted list. The list should be made by
+splicing together the nodes of the first two lists.
+
+Return the head of the merged linked list.
+
+
+
+Example 1:
+
+Input: list1 = [1,2,4], list2 = [1,3,4]
+Output: [1,1,2,3,4,4]
+
+Example 2:
+
+Input: list1 = [], list2 = []
+Output: []
+
+Example 3:
+
+Input: list1 = [], list2 = [0]
+Output: [0]
+
+
+
+Constraints:
+
+        • The number of nodes in both lists is in the range [0, 50].
+
+        • -100 <= Node.val <= 100
+
+        • Both list1 and list2 are sorted in non-decreasing order.
+"""
+
+
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def mergeTwoLists(
+        self, list1: Optional[ListNode], list2: Optional[ListNode]
+    ) -> Optional[ListNode]:
+
+        if not list1:
+            return list2
+        if not list2:
+            return list1
+
+        if list1.val < list2.val:
+            head = list1
+            list1 = list1.next
+        else:
+            head = list2
+            list2 = list2.next
+
+        current = head
+        while list1 and list2:
+            if list1.val < list2.val:
+                current.next = list1
+                list1 = list1.next
+            else:
+                current.next = list2
+                list2 = list2.next
+            current = current.next
+
+        current.next = list1 or list2
+        return head

work/1/Easy/String/20.valid-parentheses.py

@@ -0,0 +1,76 @@
+"""
+20. Valid Parentheses
+Difficulty: Easy
+https://leetcode.com/problems/valid-parentheses/
+
+──────────────────────────────────────────────────
+
+Given a string s containing just the characters '(', ')', '{', '}',
+'[' and ']', determine if the input string is valid.
+
+An input string is valid if:
+
+        • Open brackets must be closed by the same type of brackets.
+
+        • Open brackets must be closed in the correct order.
+
+• Every close bracket has a corresponding open bracket of the same
+type.
+
+
+
+Example 1:
+
+Input: s = "()"
+
+Output: true
+
+Example 2:
+
+Input: s = "()[]{}"
+
+Output: true
+
+Example 3:
+
+Input: s = "(]"
+
+Output: false
+
+Example 4:
+
+Input: s = "([])"
+
+Output: true
+
+Example 5:
+
+Input: s = "([)]"
+
+Output: false
+
+
+
+Constraints:
+
+        • 1 <= s.length <= 10^4
+
+        • s consists of parentheses only '()[]{}'.
+"""
+
+
+class Solution:
+    def isValid(self, s: str) -> bool:
+        stack = []
+        pairs = {")": "(", "]": "[", "}": "{"}
+
+        for c in s:
+            if c in pairs:
+                if stack and pairs[c] == stack[-1]:
+                    stack.pop()
+                else:
+                    return False
+            else:
+                stack.append(c)
+
+        return True if not stack else False

work/1/Medium/Array/150.evaluate-reverse-polish-notation.py

@@ -0,0 +1,88 @@
+"""
+150. Evaluate Reverse Polish Notation
+Difficulty: Medium
+https://leetcode.com/problems/evaluate-reverse-polish-notation/
+
+──────────────────────────────────────────────────
+
+You are given an array of strings tokens that represents an
+arithmetic expression in a Reverse Polish Notation.
+
+Evaluate the expression. Return an integer that represents the value
+of the expression.
+
+Note that:
+
+        • The valid operators are '+', '-', '*', and '/'.
+
+        • Each operand may be an integer or another expression.
+
+        • The division between two integers always truncates toward zero.
+
+        • There will not be any division by zero.
+
+• The input represents a valid arithmetic expression in a reverse
+polish notation.
+
+• The answer and all the intermediate calculations can be
+represented in a 32-bit integer.
+
+
+
+Example 1:
+
+Input: tokens = ["2","1","+","3","*"]
+Output: 9
+Explanation: ((2 + 1) * 3) = 9
+
+Example 2:
+
+Input: tokens = ["4","13","5","/","+"]
+Output: 6
+Explanation: (4 + (13 / 5)) = 6
+
+Example 3:
+
+Input: tokens =
+["10","6","9","3","+","-11","*","/","*","17","+","5","+"]
+Output: 22
+Explanation: ((10 * (6 / ((9 + 3) * -11))) + 17) + 5
+= ((10 * (6 / (12 * -11))) + 17) + 5
+= ((10 * (6 / -132)) + 17) + 5
+= ((10 * 0) + 17) + 5
+= (0 + 17) + 5
+= 17 + 5
+= 22
+
+
+
+Constraints:
+
+        • 1 <= tokens.length <= 10^4
+
+• tokens[i] is either an operator: "+", "-", "*", or "/", or an
+integer in the range [-200, 200].
+"""
+
+
+class Solution:
+    def evalRPN(self, tokens: List[str]) -> int:
+        stack = []
+        operations = {
+            "+": lambda x, y: int(x + y),
+            "-": lambda x, y: int(x - y),
+            "*": lambda x, y: int(x * y),
+            "/": lambda x, y: int(x / y),
+        }
+
+        for c in tokens:
+            if c in operations:
+                y = stack.pop()
+                x = stack.pop()
+                calc_func = operations[c]
+                result = calc_func(x, y)
+                stack.append(result)
+            else:
+                stack.append(int(c))
+
+        return stack[0]

work/1/Medium/Array/153.find-minimum-in-rotated-sorted-array.py

@@ -0,0 +1,75 @@
+"""
+153. Find Minimum in Rotated Sorted Array
+Difficulty: Medium
+https://leetcode.com/problems/find-minimum-in-rotated-sorted-array/
+
+──────────────────────────────────────────────────
+
+Suppose an array of length n sorted in ascending order is rotated
+between 1 and n times. For example, the array nums = [0,1,2,4,5,6,7]
+might become:
+
+        • [4,5,6,7,0,1,2] if it was rotated 4 times.
+
+        • [0,1,2,4,5,6,7] if it was rotated 7 times.
+
+Notice that rotating an array [a[0], a[1], a[2], ..., a[n-1]] 1 time
+results in the array [a[n-1], a[0], a[1], a[2], ..., a[n-2]].
+
+Given the sorted rotated array nums of unique elements, return the
+minimum element of this array.
+
+You must write an algorithm that runs in O(log n) time.
+
+
+
+Example 1:
+
+Input: nums = [3,4,5,1,2]
+Output: 1
+Explanation: The original array was [1,2,3,4,5] rotated 3 times.
+
+Example 2:
+
+Input: nums = [4,5,6,7,0,1,2]
+Output: 0
+Explanation: The original array was [0,1,2,4,5,6,7] and it was
+rotated 4 times.
+
+Example 3:
+
+Input: nums = [11,13,15,17]
+Output: 11
+Explanation: The original array was [11,13,15,17] and it was rotated
+4 times.
+
+
+
+Constraints:
+
+        • n == nums.length
+
+        • 1 <= n <= 5000
+
+        • -5000 <= nums[i] <= 5000
+
+        • All the integers of nums are unique.
+
+        • nums is sorted and rotated between 1 and n times.
+"""
+
+
+class Solution:
+    def findMin(self, nums: List[int]) -> int:
+        l, r = 0, len(nums) - 1
+        lowest_index = -1
+
+        while l <= r:
+            m = (l + r) // 2
+            if nums[m] <= nums[-1]:
+                lowest_index = m
+                r = m - 1
+            else:
+                l = m + 1
+
+        return nums[lowest_index]

work/1/Medium/Array/739.daily-temperatures.py

@@ -0,0 +1,50 @@
+"""
+739. Daily Temperatures
+Difficulty: Medium
+https://leetcode.com/problems/daily-temperatures/
+
+──────────────────────────────────────────────────
+
+Given an array of integers temperatures represents the daily
+temperatures, return an array answer such that answer[i] is the number
+of days you have to wait after the i^th day to get a warmer
+temperature. If there is no future day for which this is possible,
+keep answer[i] == 0 instead.
+
+
+
+Example 1:
+
+Input: temperatures = [73,74,75,71,69,72,76,73]
+Output: [1,1,4,2,1,1,0,0]
+
+Example 2:
+
+Input: temperatures = [30,40,50,60]
+Output: [1,1,1,0]
+
+Example 3:
+
+Input: temperatures = [30,60,90]
+Output: [1,1,0]
+
+
+
+Constraints:
+
+        • 1 <= temperatures.length <= 10^5
+
+        • 30 <= temperatures[i] <= 100
+"""
+
+
+class Solution:
+    def dailyTemperatures(self, temperatures: List[int]) -> List[int]:
+        ans = [0] * len(temperatures)
+        stack = []
+        for i, temp in enumerate(temperatures):
+            while stack and temperatures[stack[-1]] < temp:
+                prev = stack.pop()
+                ans[prev] = i - prev
+            stack.append(i)
+        return ans

work/1/Medium/Array/74.search-a-2d-matrix.py

@@ -0,0 +1,74 @@
+"""
+74. Search a 2D Matrix
+Difficulty: Medium
+https://leetcode.com/problems/search-a-2d-matrix/
+
+──────────────────────────────────────────────────
+
+You are given an m x n integer matrix matrix with the following two
+properties:
+
+        • Each row is sorted in non-decreasing order.
+
+• The first integer of each row is greater than the last integer of
+the previous row.
+
+Given an integer target, return true if target is in matrix or false
+otherwise.
+
+You must write a solution in O(log(m * n)) time complexity.
+
+
+
+Example 1:
+
+Input: matrix = [[1,3,5,7],[10,11,16,20],[23,30,34,60]], target = 3
+Output: true
+
+Example 2:
+
+Input: matrix = [[1,3,5,7],[10,11,16,20],[23,30,34,60]], target = 13
+Output: false
+
+
+
+Constraints:
+
+        • m == matrix.length
+
+        • n == matrix[i].length
+
+        • 1 <= m, n <= 100
+
+        • -10^4 <= matrix[i][j], target <= 10^4
+"""
+
+
+class Solution:
+    def searchMatrix(self, matrix: List[List[int]], target: int) -> bool:
+        ROWS, COLS = len(matrix), len(matrix[0])
+
+        top, bot = 0, ROWS - 1
+        while top <= bot:
+            row = (top + bot) // 2
+            if target > matrix[row][-1]:
+                top = row + 1
+            elif target < matrix[row][0]:
+                bot = row - 1
+            else:
+                break
+
+        if not (top <= bot):
+            return False
+
+        row = (top + bot) // 2
+        l, r = 0, COLS - 1
+        while l <= r:
+            m = (l + r) // 2
+            if target > matrix[row][m]:
+                l = m + 1
+            elif target < matrix[row][m]:
+                r = m - 1
+            else:
+                return True
+        return False

work/1/Medium/Array/853.car-fleet.py

@@ -0,0 +1,98 @@
+"""
+853. Car Fleet
+Difficulty: Medium
+https://leetcode.com/problems/car-fleet/
+
+──────────────────────────────────────────────────
+
+There are n cars at given miles away from the starting mile 0,
+traveling to reach the mile target.
+
+You are given two integer arrays position and speed, both of length
+n, where position[i] is the starting mile of the i^th car and speed[i]
+is the speed of the i^th car in miles per hour.
+
+A car cannot pass another car, but it can catch up and then travel
+next to it at the speed of the slower car.
+
+A car fleet is a single car or a group of cars driving next to each
+other. The speed of the car fleet is the minimum speed of any car in
+the fleet.
+
+If a car catches up to a car fleet at the mile target, it will still
+be considered as part of the car fleet.
+
+Return the number of car fleets that will arrive at the destination.
+
+
+
+Example 1:
+
+Input: target = 12, position = [10,8,0,5,3], speed = [2,4,1,1,3]
+
+Output: 3
+
+Explanation:
+
+• The cars starting at 10 (speed 2) and 8 (speed 4) become a fleet,
+meeting each other at 12. The fleet forms at target.
+
+• The car starting at 0 (speed 1) does not catch up to any other
+car, so it is a fleet by itself.
+
+• The cars starting at 5 (speed 1) and 3 (speed 3) become a fleet,
+meeting each other at 6. The fleet moves at speed 1 until it reaches
+target.
+
+Example 2:
+
+Input: target = 10, position = [3], speed = [3]
+
+Output: 1
+
+Explanation:
+
+There is only one car, hence there is only one fleet.
+
+Example 3:
+
+Input: target = 100, position = [0,2,4], speed = [4,2,1]
+
+Output: 1
+
+Explanation:
+
+• The cars starting at 0 (speed 4) and 2 (speed 2) become a fleet,
+meeting each other at 4. The car starting at 4 (speed 1) travels to 5.
+
+• Then, the fleet at 4 (speed 2) and the car at position 5 (speed 1)
+become one fleet, meeting each other at 6. The fleet moves at speed 1
+until it reaches target.
+
+
+
+Constraints:
+
+        • n == position.length == speed.length
+
+        • 1 <= n <= 10^5
+
+        • 0 < target <= 10^6
+
+        • 0 <= position[i] < target
+
+        • All the values of position are unique.
+
+        • 0 < speed[i] <= 10^6
+"""
+
+
+class Solution:
+    def carFleet(self, target: int, position: List[int], speed: List[int]) -> int:
+        stack = []
+        for pos, spd in sorted(zip(position, speed), reverse=True):
+            time = (target - pos) / spd
+            if not stack or time > stack[-1]:
+                stack.append(time)
+
+        return len(stack)

work/1/Medium/Stack/155.min-stack.py

@@ -0,0 +1,86 @@
+"""
+155. Min Stack
+Difficulty: Medium
+https://leetcode.com/problems/min-stack/
+
+──────────────────────────────────────────────────
+
+Design a stack that supports push, pop, top, and retrieving the
+minimum element in constant time.
+
+Implement the MinStack class:
+
+        • MinStack() initializes the stack object.
+
+        • void push(int value) pushes the element value onto the stack.
+
+        • void pop() removes the element on the top of the stack.
+
+        • int top() gets the top element of the stack.
+
+        • int getMin() retrieves the minimum element in the stack.
+
+You must implement a solution with O(1) time complexity for each
+function.
+
+
+
+Example 1:
+
+Input
+["MinStack","push","push","push","getMin","pop","top","getMin"]
+[[],[-2],[0],[-3],[],[],[],[]]
+
+Output
+[null,null,null,null,-3,null,0,-2]
+
+Explanation
+MinStack minStack = new MinStack();
+minStack.push(-2);
+minStack.push(0);
+minStack.push(-3);
+minStack.getMin(); // return -3
+minStack.pop();
+minStack.top();    // return 0
+minStack.getMin(); // return -2
+
+
+
+Constraints:
+
+        • -2^31 <= val <= 2^31 - 1
+
+• Methods pop, top and getMin operations will always be called on
+non-empty stacks.
+
+        • At most 3 * 10^4 calls will be made to push, pop, top, and getMin.
+"""
+
+
+class MinStack:
+    def __init__(self):
+        self.stack = []
+        self.minStack = []
+
+    def push(self, value: int) -> None:
+        self.stack.append(value)
+        value = min(value, self.minStack[-1] if self.minStack else value)
+        self.minStack.append(value)
+
+    def pop(self) -> None:
+        self.stack.pop()
+        self.minStack.pop()
+
+    def top(self) -> int:
+        return self.stack[-1]
+
+    def getMin(self) -> int:
+        return self.minStack[-1]
+
+
+# Your MinStack object will be instantiated and called as such:
+# obj = MinStack()
+# obj.push(value)
+# obj.pop()
+# param_3 = obj.top()
+# param_4 = obj.getMin()

work/Hard/Array/42.trapping-rain-water.js

@@ -1,44 +0,0 @@
-/*
- * 42. Trapping Rain Water
- * Difficulty: Hard
- * https://leetcode.com/problems/trapping-rain-water/
- * 
- * ──────────────────────────────────────────────────
- * 
- * Given n non-negative integers representing an elevation map where the
- * width of each bar is 1, compute how much water it can trap after
- * raining.
- * 
- *  
- * 
- * Example 1:
- * 
- * Input: height = [0,1,0,2,1,0,1,3,2,1,2,1]
- * Output: 6
- * Explanation: The above elevation map (black section) is represented
- * by array [0,1,0,2,1,0,1,3,2,1,2,1]. In this case, 6 units of rain
- * water (blue section) are being trapped.
- * 
- * Example 2:
- * 
- * Input: height = [4,2,0,3,2,5]
- * Output: 9
- * 
- *  
- * 
- * Constraints:
- * 
- * 	• n == height.length
- * 
- * 	• 1 <= n <= 2 * 10^4
- * 
- * 	• 0 <= height[i] <= 10^5
-*/
-
-/**
- * @param {number[]} height
- * @return {number}
- */
-var trap = function(height) {
-    
-};