import { statSync } from "node:fs";
import type { AuthUser, Feature, ServerContext } from "@stc/contracts";
import type { LoadedCourse, Manifest } from "@stc/course-format";
import { libraryRepo, progressRepo } from "@stc/db";
import type {
  ContinueItem, CourseCard, CoursePayload, Format, LessonProgress, LibraryPayload, OutlineModule, SearchHit,
} from "../shared/types";
import { mediaUrl } from "../shared/types";
import { accessIndex, courseFor, isOwner, visible } from "./access";
import { coverUrlFor } from "./covers";
import { moduleLocks } from "./gating";
import { json, notFound, param } from "./http";

const WPM = 220;
const EXERCISE_MINUTES = 15;

/** Lesson length estimates (minutes), cached per course and manifest mtime. */
export function createEstimator(ctx: ServerContext) {
  const cache = new Map<string, { key: string; minutes: Map<string, number | null> }>();
  return async function minutesFor(c: LoadedCourse): Promise<Map<string, number | null>> {
    let key = c.manifestPath;
    try { key += `@${statSync(c.manifestPath).mtimeMs}`; } catch { /* keep path */ }
    const hit = cache.get(c.id);
    if (hit && hit.key === key) return hit.minutes;
    const minutes = new Map<string, number | null>();
    for (const mod of c.manifest?.modules ?? []) {
      for (const l of mod.lessons) {
        if (l.type === "video") {
          minutes.set(l.id, l.duration ? l.duration / 60 : null);
          continue;
        }
        let words = 0;
        try {
          const md = await ctx.courses.readLessonMarkdown(c.id, l.id);
          words = md ? md.split(/\s+/).filter(Boolean).length : 0;
        } catch { /* unreadable: no estimate */ }
        const read = words / WPM;
        minutes.set(l.id, l.type === "exercise" ? Math.max(EXERCISE_MINUTES, read) : words ? Math.max(1, read) : null);
      }
    }
    cache.set(c.id, { key, minutes });
    return minutes;
  };
}

export function formatsOf(m: Manifest): Format[] {
  const types = new Set(m.modules.flatMap((x) => x.lessons.map((l) => l.type)));
  const f: Format[] = [];
  if (types.has("text")) f.push("text");
  if (types.has("video")) f.push("video");
  if (m.decks?.length) f.push("slides");
  if (types.has("exercise")) f.push("exercises");
  return f;
}

export function addedAt(c: LoadedCourse): string {
  const imported = c.manifest?.source?.importedAt;
  if (imported && !Number.isNaN(Date.parse(imported))) return new Date(imported).toISOString();
  try { return statSync(c.manifestPath).mtime.toISOString(); } catch { return new Date(0).toISOString(); }
}

const slug = (s: string) => s.trim().toLowerCase().normalize("NFKD").replace(/[^\p{L}\p{N}]+/gu, "-").replace(/^-|-$/g, "");
const fold = (s: string) => s.normalize("NFKD").replace(/\p{M}/gu, "").toLowerCase();

type ProgressByCourse = Map<string, Record<string, LessonProgress>>;

async function allProgress(ctx: ServerContext, user: AuthUser | null): Promise<ProgressByCourse> {
  const out: ProgressByCourse = new Map();
  if (!user) return out;
  const rows = await ctx.db.sql`SELECT course_id, lesson_id, state, position_seconds, updated_at FROM progress WHERE user_id = ${user.id}`;
  for (const r of rows) {
    const rec = out.get(r.course_id) ?? {};
    rec[r.lesson_id] = { state: r.state, positionSeconds: r.position_seconds === null ? null : Number(r.position_seconds), updatedAt: r.updated_at };
    out.set(r.course_id, rec);
  }
  return out;
}

export function libraryRoutes(ctx: ServerContext): Feature["routes"] {
  const minutesFor = createEstimator(ctx);
  const lib = libraryRepo(ctx.db);

  async function card(c: LoadedCourse, progress: Record<string, LessonProgress>): Promise<CourseCard> {
    const m = c.manifest;
    if (!m) {
      return {
        id: c.id, title: c.id, pitch: c.diagnostics[0]?.message ?? null, authors: [], coverUrl: null, accent: null, formats: [],
        lessonCount: 0, minutes: 0, collections: [], tracks: [], source: null, addedAt: addedAt(c), status: "error", progress: 0, doneCount: 0, started: false,
      };
    }
    const lessons = m.modules.flatMap((x) => x.lessons);
    const est = await minutesFor(c);
    const minutes = Math.round(lessons.reduce((s, l) => s + (est.get(l.id) ?? 0), 0));
    const doneCount = lessons.filter((l) => progress[l.id]?.state === "done").length;
    return {
      id: m.id, title: m.title, pitch: m.pitch ?? null, authors: m.authors ?? [],
      coverUrl: coverUrlFor(ctx, m),
      accent: m.accent ?? null, formats: formatsOf(m), lessonCount: lessons.length, minutes,
      collections: m.collections ?? [], tracks: (m.tracks ?? []).map((t) => t.label), source: m.source?.kind ?? null,
      addedAt: addedAt(c), status: c.status, progress: lessons.length ? doneCount / lessons.length : 0, doneCount,
      started: lessons.some((l) => progress[l.id]),
    };
  }

  function continueItem(c: LoadedCourse, progress: Record<string, LessonProgress>, bypass: boolean): ContinueItem | null {
    const m = c.manifest!;
    const lessons = m.modules.flatMap((x) => x.lessons);
    const done = lessons.filter((l) => progress[l.id]?.state === "done").length;
    if (!lessons.some((l) => progress[l.id]) || done === lessons.length) return null;
    const locks = moduleLocks(m, progress, bypass);
    for (const [i, mod] of m.modules.entries()) {
      if (locks[i]) break;
      const next = mod.lessons.find((l) => progress[l.id]?.state !== "done");
      if (!next) continue;
      return {
        courseId: m.id, lessonId: next.id, lessonTitle: next.title, moduleTitle: mod.title, moduleIndex: i,
        moduleDone: mod.lessons.filter((l) => progress[l.id]?.state === "done").length, moduleTotal: mod.lessons.length,
        progress: done / lessons.length,
      };
    }
    return null;
  }

  return {
    "/api/library": {
      GET: async (_req, rc) => {
        const user = rc.user;
        const idx = await accessIndex(ctx.db, user);
        const courses = ctx.courses.list().filter((c) => visible(user, c, idx));
        const progress = await allProgress(ctx, user);
        const cards = await Promise.all(courses.map((c) => card(c, progress.get(c.id) ?? {})));
        const byId = new Map(cards.map((c) => [c.id, c]));

        const cont: (ContinueItem & { at: string })[] = [];
        for (const c of courses) {
          if (!c.manifest) continue;
          const p = progress.get(c.id) ?? {};
          const item = continueItem(c, p, isOwner(user));
          if (item) cont.push({ ...item, at: Object.values(p).map((x) => x.updatedAt).sort().pop() ?? "" });
        }
        cont.sort((a, b) => (a.at < b.at ? 1 : -1));

        const newest = [...cards].filter((c) => c.status === "ok" || c.lessonCount).sort((a, b) => (a.addedAt < b.addedAt ? 1 : a.addedAt > b.addedAt ? -1 : a.title.localeCompare(b.title))).map((c) => c.id);

        const collections: LibraryPayload["collections"] = [];
        for (const col of await lib.listCollections()) {
          collections.push({ id: col.id, title: col.title, courseIds: col.courseIds.filter((id) => byId.has(id)) });
        }
        for (const c of cards) {
          for (const name of c.collections) {
            const id = slug(name);
            let col = collections.find((x) => x.id === id || x.title.toLowerCase() === name.toLowerCase());
            if (!col) collections.push((col = { id, title: name, courseIds: [] }));
            if (!col.courseIds.includes(c.id)) col.courseIds.push(c.id);
          }
        }

        const featuredId = await lib.getFeatured();
        const featured = (featuredId && byId.get(featuredId)) || (cont[0] && byId.get(cont[0].courseId)) || byId.get(newest[0] ?? "") || null;
        const payload: LibraryPayload = {
          signedIn: !!user,
          featured,
          continue: cont.map(({ at: _at, ...rest }) => rest),
          newest,
          collections: collections.filter((c) => c.courseIds.length > 0),
          courses: cards.sort((a, b) => a.title.localeCompare(b.title)),
        };
        return json(payload);
      },
    },
    "/api/library/search": {
      GET: async (_req, rc) => {
        const q = fold(rc.url.searchParams.get("q") ?? "").trim();
        if (!q) return json([]);
        const terms = q.split(/\s+/);
        const hit = (s: string | undefined) => !!s && terms.every((t) => fold(s).includes(t));
        const idx = await accessIndex(ctx.db, rc.user);
        const out: SearchHit[] = [];
        for (const c of ctx.courses.list()) {
          const m = c.manifest;
          if (!m || !visible(rc.user, c, idx)) continue;
          const course = hit(`${m.title} ${m.pitch ?? ""} ${(m.authors ?? []).join(" ")} ${(m.collections ?? []).join(" ")}`);
          const lessons = m.modules.flatMap((mod) => mod.lessons.filter((l) => hit(l.title) || hit(`${mod.title} ${l.title}`)).map((l) => ({ id: l.id, title: l.title, moduleTitle: mod.title })));
          if (course || lessons.length) out.push({ courseId: m.id, courseTitle: m.title, course, lessons: lessons.slice(0, 8) });
        }
        out.sort((a, b) => Number(b.course) - Number(a.course) || b.lessons.length - a.lessons.length);
        return json(out.slice(0, 50));
      },
    },
    "/api/courses/:courseId": {
      GET: async (_req, rc) => {
        const found = await courseFor(ctx, rc.user, param(rc, "courseId"));
        if (!found) return notFound();
        const { course, manifest: m } = found;
        const progress = rc.user ? await progressRepo(ctx.db).get(rc.user.id, m.id) : {};
        const est = await minutesFor(course);
        const locks = moduleLocks(m, progress, found.canEdit);
        const deckTargets = new Set((m.decks ?? []).map((d) => d.attachTo));
        const modules: OutlineModule[] = m.modules.map((mod, i) => ({
          id: mod.id, title: mod.title, index: i, locked: locks[i]!, hasCode: !!mod.code,
          lessons: mod.lessons.map((l, li) => ({
            id: l.id, title: l.title, type: l.type, minutes: est.get(l.id) ?? null,
            hasDeck: deckTargets.has(l.id) || (li === 0 && deckTargets.has(mod.id)), browser: !!l.browser,
          })),
        }));
        const payload: CoursePayload = {
          id: m.id, title: m.title, pitch: m.pitch ?? null, authors: m.authors ?? [], accent: m.accent ?? null,
          coverUrl: coverUrlFor(ctx, m),
          tracks: m.tracks ?? [], gating: m.gating, source: m.source?.kind ?? null, status: course.status,
          modules, progress, canEdit: found.canEdit, signedIn: !!rc.user,
          diagnostics: found.canEdit ? course.diagnostics.map((d) => ({ level: d.level, lessonId: d.lessonId, path: d.path, message: d.message })) : [],
        };
        return json(payload);
      },
    },
  };
}