#!/usr/bin/env bun
/**
 * Rewrite the pinned `📋 Today` daily-brief issue from SRS state.
 *
 * Runs every day at 10:00 UTC (6 AM ET) and on demand. Stateless by design:
 * it reads srs.json + schedule.json and rewrites one issue body, so running
 * it twice in a day is a byte-identical no-op (drill picks are seeded by the
 * date). Overflow needs no bookkeeping either — anything past the daily cap
 * simply stays due and is the oldest entry tomorrow.
 *
 * Retrieval rules enforced here:
 * - Review and drill lines carry number + difficulty only. Never the topic,
 *   never a link — recognizing the pattern unaided is the exercise.
 * - Blind drills come only from optional pools of topics covered in EARLIER
 *   weeks; the current week's optional pool is reserved for Saturday's gate.
 * - Boosted topics (failed gate problem / repeated drill misses) inject up to
 *   2 extra drills, inside the same daily cap.
 *
 *   bun scripts/srs-scheduler.ts             # rewrite the live issue
 *   SRS_DRY=1 SRS_TODAY=2026-08-30 bun ...   # print the body, touch nothing
 */
import { github } from "./github.ts";
import { projectMirror, reportMirror } from "./srs-project.ts";
import {
  CAMPAIGN_DAYS,
  type Catalog,
  type State,
  TODAY_TITLE,
  campaignDay,
  campaignWeek,
  dueReviews,
  fetchCatalog,
  loadSchedule,
  loadState,
  prettyDate,
  rng,
  sample,
  todayET,
  weekdayOf,
} from "./srs.ts";

const DRY = process.env.SRS_DRY === "1";
const DAILY_CAP = 6;

const gh = await github();
const state = await loadState();
const schedule = await loadSchedule();
const today = todayET();
const week = campaignWeek(today);

// ── compose the body ─────────────────────────────────────────────

/** Week in which a topic was (or will be) taught, from the schedule file. */
function topicWeek(topic: number): number | undefined {
  for (const [date, t] of Object.entries(schedule)) {
    if (t === topic) return campaignWeek(date);
  }
  return undefined;
}

interface Drill {
  lc: number;
  difficulty: string;
}

function pickDrills(catalog: Catalog, budget: number): Drill[] {
  // Optional problems from earlier weeks, unseen by both ladder and drills.
  const pool = [...catalog.problems.values()]
    .filter((p) => {
      if (p.set !== "optional" || !p.open) return false;
      if (state.problems[p.lc] || state.drill_pool_used.includes(p.lc)) return false;
      const w = topicWeek(p.topic);
      return w !== undefined && w < week;
    })
    .sort((a, b) => a.lc - b.lc); // stable base order for the seeded shuffle

  const boosted = pool.filter((p) => state.topics[p.topic]?.boost);
  const regular = pool.filter((p) => !state.topics[p.topic]?.boost);

  const picks = [
    ...sample(boosted, Math.min(2, budget), rng(`boost-${today}`)),
    ...sample(regular, Math.min(2, Math.max(0, budget - Math.min(2, boosted.length))), rng(`drill-${today}`)),
  ].slice(0, budget);
  return picks.map((p) => ({ lc: p.lc, difficulty: p.difficulty }));
}

function composeBody(catalog: Catalog): string {
  if (weekdayOf(today) === 0) {
    return "Rest day. Nothing is due. Overdue reviews moved to Monday.";
  }

  const due = dueReviews(state, today);
  const reviews = due.slice(0, DAILY_CAP);
  const carried = due.length - reviews.length;
  const drills = pickDrills(catalog, DAILY_CAP - reviews.length);

  const lines: string[] = [
    `## ${prettyDate(today)} — Day ${campaignDay(today)}/${CAMPAIGN_DAYS} · Week ${week}`,
    "",
  ];

  const topicIssue = schedule[today];
  const topic = topicIssue === undefined ? undefined : catalog.topics.get(topicIssue);
  if (topic) {
    const core = [...catalog.problems.values()]
      .filter((p) => p.topic === topic.issue && p.set === "core")
      .sort((a, b) => a.lc - b.lc)
      .map((p) => `[LC ${p.lc}](${p.url})${p.open ? "" : " ✓"}`);
    lines.push(`### New topic: ${topic.name} (#${topic.issue})`, `Core: ${core.join(" · ")}`, "");
  } else {
    lines.push("_No new topic today — reviews and drills only._", "");
  }

  lines.push(`### Reviews due (${reviews.length})`);
  if (reviews.length) {
    lines.push("Solve each from scratch. Do not open your old solution first.");
    for (const [lc, p] of reviews) {
      const difficulty = catalog.problems.get(Number(lc))?.difficulty ?? p.difficulty;
      lines.push(`- LC ${lc} — ${difficulty} — stage ${p.stage}`);
    }
    if (carried > 0) lines.push(`\n${carried} more carried to tomorrow (cap ${DAILY_CAP}).`);
  } else {
    lines.push("None.");
  }
  lines.push("");

  lines.push(`### Blind drills (${drills.length})`);
  if (drills.length) {
    lines.push("No topic given. Name the pattern out loud before you code.");
    for (const d of drills) lines.push(`- LC ${d.lc} — ${d.difficulty}`);
  } else {
    lines.push("None today.");
  }
  lines.push("");

  lines.push(
    "### Log your results",
    "Comment on this issue, one line per problem:",
    "`/done 704 pass` · `/done 15 fail`",
    "",
    "### Rules",
    "90-minute cap · core first, then reviews, then drills · close-out",
    "ritual on every submit.",
  );
  return lines.join("\n");
}

// ── find / create / pin the Today issue ──────────────────────────

async function todayIssue(): Promise<{ number: number; created: boolean }> {
  for await (const raw of gh.list(`/repos/${gh.repo}/issues?state=open`)) {
    const issue = raw as { number: number; title: string; pull_request?: unknown };
    if (!issue.pull_request && issue.title === TODAY_TITLE) {
      return { number: issue.number, created: false };
    }
  }
  const created = (await gh.api(`/repos/${gh.repo}/issues`, {
    method: "POST",
    body: JSON.stringify({ title: TODAY_TITLE, body: "(initializing)" }),
  })) as { number: number; node_id: string };
  try {
    await gh.api("/graphql", {
      method: "POST",
      body: JSON.stringify({
        query: `mutation($id: ID!) { pinIssue(input: { issueId: $id }) { issue { number } } }`,
        variables: { id: created.node_id },
      }),
    });
  } catch (err) {
    console.warn(`could not pin #${created.number}: ${err} — pin it by hand`);
  }
  return { number: created.number, created: true };
}

// ── run ──────────────────────────────────────────────────────────

const catalog = await fetchCatalog(gh);
const body = composeBody(catalog);

if (DRY) {
  console.log(body);
  process.exit(0);
}

const issue = await todayIssue();
await gh.api(`/repos/${gh.repo}/issues/${issue.number}`, {
  method: "PATCH",
  body: JSON.stringify({ body }),
});
console.log(`${issue.created ? "created + pinned" : "rewrote"} #${issue.number} ${TODAY_TITLE}`);

// Mirror every due problem's next_review so the project's Target Date views
// stay a live review calendar (problem rows only — never topic rows).
const mirror = await projectMirror(gh.repo.split("/")[0]!, gh.repo);
if (weekdayOf(today) !== 0) {
  for (const [, p] of dueReviews(state as State, today)) {
    await mirror.setTargetDate(p.issue, p.next_review!);
  }
}
await reportMirror(mirror);
console.log(body);