#!/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"),
);