const express = require('express');
const Database = require('better-sqlite3');
const path = require('path');
const fs = require('fs');
const os = require('os');
const { execSync } = require('child_process');

const app = express();
const PORT = 3099;

// DB path shared with plugin
const DB_PATH = path.join(os.homedir(), '.local', 'share', 'jellyfin-lessons', 'lessons.db');

// Ensure DB directory exists
fs.mkdirSync(path.dirname(DB_PATH), { recursive: true });

const db = new Database(DB_PATH);

// UUID helper
function generateId() {
  return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, c => {
    const r = Math.random() * 16 | 0;
    return (c === 'x' ? r : (r & 0x3 | 0x8)).toString(16);
  });
}

// Initialize schema — must match plugin Data/LessonStore.cs
const now = () => new Date().toISOString();
db.exec(`
  CREATE TABLE IF NOT EXISTS lessons (
    id TEXT PRIMARY KEY,
    title TEXT NOT NULL,
    grade INTEGER NOT NULL,
    subject TEXT NOT NULL,
    lesson_date TEXT NOT NULL,
    description TEXT,
    source_path TEXT NOT NULL,
    compiled_html TEXT,
    created_at TEXT NOT NULL,
    updated_at TEXT NOT NULL
  );

  CREATE TABLE IF NOT EXISTS lesson_media (
    lesson_id TEXT NOT NULL,
    jellyfin_item_id TEXT NOT NULL,
    sort_order INTEGER NOT NULL DEFAULT 0,
    PRIMARY KEY (lesson_id, jellyfin_item_id),
    FOREIGN KEY (lesson_id) REFERENCES lessons(id) ON DELETE CASCADE
  );
`);

// Middleware
app.use(express.json({ limit: '10mb' }));
app.use(express.static(path.join(__dirname, 'public')));

// CORS for local dev
app.use((req, res, next) => {
  res.header('Access-Control-Allow-Origin', '*');
  res.header('Access-Control-Allow-Methods', 'GET, POST, DELETE, OPTIONS');
  res.header('Access-Control-Allow-Headers', 'Content-Type');
  if (req.method === 'OPTIONS') return res.sendStatus(200);
  next();
});

// GET /api/lessons — list all lessons
app.get('/api/lessons', (req, res) => {
  try {
    const lessons = db.prepare('SELECT * FROM lessons ORDER BY updated_at DESC').all();
    res.json(lessons);
  } catch (err) {
    res.status(500).json({ error: err.message });
  }
});

// GET /api/lessons/:id — single lesson with media items
app.get('/api/lessons/:id', (req, res) => {
  try {
    const lesson = db.prepare('SELECT * FROM lessons WHERE id = ?').get(req.params.id);
    if (!lesson) return res.status(404).json({ error: 'Lesson not found' });
    const mediaItems = db.prepare('SELECT * FROM lesson_media WHERE lesson_id = ? ORDER BY sort_order').all(req.params.id);
    res.json({ ...lesson, mediaItems });
  } catch (err) {
    res.status(500).json({ error: err.message });
  }
});

// POST /api/lessons — create or update lesson
app.post('/api/lessons', (req, res) => {
  try {
    const { id, title, grade, subject, lessonDate, description, sourcePath, compiledHtml, mediaItems } = req.body;

    if (!title) return res.status(400).json({ error: 'Title is required' });

    const upsertLesson = db.transaction(() => {
      let lessonId = id || generateId();
      const ts = now();
      const existing = id ? db.prepare('SELECT created_at FROM lessons WHERE id = ?').get(id) : null;
      const createdAt = existing ? existing.created_at : ts;

      db.prepare(`
        INSERT INTO lessons (id, title, grade, subject, lesson_date, description, source_path, compiled_html, created_at, updated_at)
        VALUES (@id, @title, @grade, @subject, @lesson_date, @description, @source_path, @compiled_html, @created_at, @updated_at)
        ON CONFLICT(id) DO UPDATE SET
          title = excluded.title, grade = excluded.grade, subject = excluded.subject,
          lesson_date = excluded.lesson_date, description = excluded.description,
          source_path = excluded.source_path, compiled_html = excluded.compiled_html,
          updated_at = excluded.updated_at
      `).run({
        id: lessonId, title, grade: grade || 0,
        subject: subject || '', lesson_date: lessonDate || new Date().toISOString().split('T')[0],
        description: description || null, source_path: sourcePath || '',
        compiled_html: compiledHtml || null, created_at: createdAt, updated_at: ts
      });

      // Replace media items
      db.prepare('DELETE FROM lesson_media WHERE lesson_id = ?').run(lessonId);
      if (mediaItems && Array.isArray(mediaItems)) {
        const insertMedia = db.prepare('INSERT INTO lesson_media (lesson_id, jellyfin_item_id, sort_order) VALUES (?, ?, ?)');
        for (const item of mediaItems) {
          insertMedia.run(lessonId, item.jellyfinItemId, item.sortOrder || 0);
        }
      }

      return lessonId;
    });

    const lessonId = upsertLesson();
    const lesson = db.prepare('SELECT * FROM lessons WHERE id = ?').get(lessonId);
    const media = db.prepare('SELECT * FROM lesson_media WHERE lesson_id = ? ORDER BY sort_order').all(lessonId);
    res.json({ ...lesson, mediaItems: media });
  } catch (err) {
    res.status(500).json({ error: err.message });
  }
});

// DELETE /api/lessons/:id
app.delete('/api/lessons/:id', (req, res) => {
  try {
    const result = db.prepare('DELETE FROM lessons WHERE id = ?').run(req.params.id);
    if (result.changes === 0) return res.status(404).json({ error: 'Lesson not found' });
    res.json({ deleted: true });
  } catch (err) {
    res.status(500).json({ error: err.message });
  }
});

// POST /api/compile — compile Typst to HTML
app.post('/api/compile', (req, res) => {
  try {
    const { typst } = req.body;
    if (!typst) return res.status(400).json({ error: 'typst source is required' });

    // Write to temp file
    const tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), 'typst-'));
    const srcFile = path.join(tmpDir, 'lesson.typ');
    const outFile = path.join(tmpDir, 'lesson.html');

    fs.writeFileSync(srcFile, typst);

    try {
      execSync(`typst compile "${srcFile}" "${outFile}"`, { timeout: 10000, encoding: 'utf8' });
      const html = fs.readFileSync(outFile, 'utf8');
      res.json({ html });
    } finally {
      // Cleanup
      fs.rmSync(tmpDir, { recursive: true, force: true });
    }
  } catch (err) {
    res.status(500).json({ error: err.stderr || err.message });
  }
});

app.listen(PORT, () => {
  console.log(`Jellyfin Lessons Admin UI running at http://localhost:${PORT}`);
});