leetcode/AGENTS.md

# Repository Guidelines

## 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 (`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

Three owners, one direction of truth:

```mermaid
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 -->|8 AM ET cron| Mail[digest email + one-tap links]
  Mail -->|GET /log| D1
  PI -->|/done webhook| D1
  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]
  Charts -->|bun run stats| TUI[terminal dashboard]
```

- **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.
- **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.

## Key Directories

| Path | Purpose |
|---|---|
| `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/` (append-only; `0002` is the +3/+7 ladder rebuild) |
| `.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; Tab cycles the
                        # sections: new problems → work/1, then the owed 3-day and 7-day
                        # 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 stats           # terminal dashboard over GET /api/stats — four panes (Overview,
                        # Ladder, Concepts, Activity); Tab/1-4 switches, ↑↓ scrolls,
                        # r refetches, q quits. Outside a TTY it prints every pane once.
                        # SRS_API points it at a local Worker like close-solved does.
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
# 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
```

## Code Conventions & Common Patterns

- **Scripts are either entries or libraries.** Entries (`apps/cli/close-*.ts`) use shebang + top-level `await`. Libraries (`apps/cli/github.ts`, `apps/cli/report.ts`, everything in `apps/api/src/`) are side-effect-free on import — nothing touches network/credentials until a factory (`github()`, `projectMirror()`) is called.
- **Shared plumbing:** `github()` gives `repo`, `api()` (throws `METHOD path -> status body`), `list()` (paginating async generator), `closeIssue()` (comment **first**, then close — a failed PATCH still leaves a trace). `report.ts` gives `printTable`/`markdownTable`/`writeStepSummary`.
- **Narrow API payloads with guards**, not inline casts: `if (!("number" in value) || typeof value.number !== "number") return;` (see `readProblemIssue` in `close-solved.ts`). Named-const casts only with a reason.
- **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:** `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: the ladder (`new → +3 → +7 → retired`; fail resets to `+3`; first-ever log enters at `+3`), `WINDOWS`/`STAGES`/`TEMPERATURES`/`DIFFICULTIES`/`SETS` (the one vocabulary shared by the charts, the `work/<n>` buckets, the review issues and the stats dashboard), ET date math, `workingDay()` (no scheduled date is ever a Sunday), `temperatureOf()` (days since a concept was last exercised → `hot`/`fresh`/`fading`/`cold`, bands derived from `WINDOWS` so they cannot drift; read-side only, nothing is scheduled off it), 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: on existing pages only the `## Solution` section itself is script-owned, bounded by `solutionEnd()` at the next unfenced top-level heading; human prose before it and any sections after it (`## Approach`, `## Explanation`) are never touched. Never hand-write solution pages or edit inside `## Solution`.
- `apps/cli/work.ts` — the `work/` layout: bucket paths, `isSolution()`/`solvedInBucket()` (the stub test, shared with `close-solved.ts`), `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.
- `apps/api/src/stats.ts` / `apps/cli/stats.ts` / `apps/cli/tui.ts` / `apps/cli/api.ts` — the read side. `buildStats()` is the ONE aggregation: phases, ladder, difficulty, per-topic temperature, gates, the 14-day due queue, and `heat` (every campaign day, zeros and future days included — the docs page windows the tail off it rather than asking a second question). Two readers consume it, the docs island and `bun run stats`, so its shape is both their contract: change all three together. `tui.ts` is hand-rolled ANSI (bars, sparklines, heat cells, alternate screen) on charts.ts's palette, and every chart differs by GLYPH as well as by colour so a piped or `NO_COLOR` dashboard still reads. The TUI recomputes nothing: the only local fact it shows is the `work/` solution count, which is inventory, not schedule.
- `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, 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

- **Bun only**: run scripts with `bun apps/cli/<name>.ts` (or the root `bun run` aliases), install with `bun install --frozen-lockfile`. One workspace (`apps/*`), one root `bun.lock`. Node 22 appears only in `deploy.yml` because Blume requires it.
- **Near-zero runtime npm dependencies** — SVG, PNG, terminal ANSI, HMAC (WebCrypto), GraphQL are hand-rolled; Actions scripts use Bun builtins + `fetch` only. The **one** exception is the digest email: `apps/api/src/email.tsx` renders React Email (`react`, `react-dom`, `@react-email/components`, `@react-email/render`) inside the Worker, because hand-rolling table-based email HTML that survives Gmail *and* Outlook is not worth owning. It costs ~235 KB gzipped of a 3 MB budget, needs no `nodejs_compat` (it resolves to `renderToReadableStream`), and requires `"jsx": "react-jsx"` in `apps/api/tsconfig.json`. Do not extend this exception to any other module.
- Local GitHub auth falls back to `gh auth token`; scripts run fine outside Actions.

## Testing & QA

- Repo-wide: no test framework — `bun run test` submits one solution to LeetCode's judge. Exception: `apps/api/src/srs.test.ts` (`bun:test`) proves the DST cron guards with fixed dates; run via `bun run api:test`.
- QA is dry-runs + local state: Worker logic against `wrangler dev` + local D1 with `?dry=1&date=`; reconcilers with `--dry-run`; idempotency check = run twice, `cmp` output.
- Docs changes: `bunx blume build --isolated` (from `apps/docs/`) must pass with no new warnings (then `rm -rf apps/docs/.blume-verify`); after sync, review only *created* pages (prose transforms are heuristic).