'use strict';
/* Student-owned personal materials ("Мои материалы").
 * A user keeps copies of items saved from live lessons; the copies are
 * independent of the session lifecycle. */
const db = require('../db/db');
const { emit } = require('../sse');

const KINDS = ['board', 'note', 'link', 'image'];

/* GET /api/materials — list the current user's saved materials + their collections */
function list(req, res) {
  const uid = req.user.id;
  const materials = db.prepare(`
    SELECT id, kind, title, body, url, source_session_id, source_title, collection_id, tags, created_at
      FROM student_materials
     WHERE user_id = ?
     ORDER BY created_at DESC, id DESC
  `).all(uid);
  const collections = db.prepare(`
    SELECT c.id, c.name, c.color, c.sort_order,
           (SELECT COUNT(*) FROM student_materials m WHERE m.collection_id = c.id) AS count
      FROM material_collections c
     WHERE c.user_id = ?
     ORDER BY c.sort_order, c.id
  `).all(uid);
  res.json({ materials, collections });
}

/* Validate that a collection id belongs to the user; returns null if unset/invalid. */
function ownCollectionId(raw, uid) {
  if (raw === null || raw === '' || raw === undefined) return null;
  const cid = Number(raw);
  if (!Number.isFinite(cid)) return null;
  const own = db.prepare('SELECT 1 FROM material_collections WHERE id = ? AND user_id = ?').get(cid, uid);
  return own ? cid : null;
}

/* POST /api/materials — save a new item to the current user's collection.
   Body: { kind, title?, body?, url?, sourceSessionId?, sourceTitle? } */
function create(req, res) {
  const b = req.body || {};
  const kind = String(b.kind || '');
  if (!KINDS.includes(kind)) return res.status(400).json({ error: 'invalid kind' });

  const title = String(b.title || '').slice(0, 300);
  const body  = b.body != null ? String(b.body).slice(0, 60000) : null;
  const url   = b.url != null ? String(b.url).slice(0, 2000) : null;
  if ((kind === 'note') && !body) return res.status(400).json({ error: 'body required for note' });
  if ((kind === 'board' || kind === 'image' || kind === 'link') && !url)
    return res.status(400).json({ error: 'url required' });

  // Soft reference to the source session (kept readable via source_title even
  // after the session is deleted). Only store the id if the session exists.
  let sourceSessionId = Number(b.sourceSessionId);
  if (!Number.isFinite(sourceSessionId)) sourceSessionId = null;
  else if (!db.prepare('SELECT 1 FROM classroom_sessions WHERE id = ?').get(sourceSessionId)) sourceSessionId = null;
  const sourceTitle = b.sourceTitle != null ? String(b.sourceTitle).slice(0, 300) : null;
  const collectionId = ownCollectionId(b.collection_id, req.user.id);
  const tags = b.tags != null ? String(b.tags).slice(0, 500) : null;

  const r = db.prepare(`
    INSERT INTO student_materials (user_id, kind, title, body, url, source_session_id, source_title, collection_id, tags)
    VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)
  `).run(req.user.id, kind, title, body, url, sourceSessionId, sourceTitle, collectionId, tags);
  res.status(201).json({ id: Number(r.lastInsertRowid) });
}

/* PATCH /api/materials/:id — rename / edit one of the current user's items.
   Editable: title, body, url (e.g. re-saving an annotated image), collection_id, tags. */
function update(req, res) {
  const row = db.prepare('SELECT user_id FROM student_materials WHERE id = ?').get(req.params.id);
  if (!row) return res.status(404).json({ error: 'not found' });
  if (row.user_id !== req.user.id) return res.status(403).json({ error: 'forbidden' });
  const b = req.body || {};
  const fields = [], args = [];
  if (b.title !== undefined) { fields.push('title = ?'); args.push(String(b.title || '').slice(0, 300)); }
  if (b.body  !== undefined) { fields.push('body = ?');  args.push(b.body != null ? String(b.body).slice(0, 60000) : null); }
  if (b.url   !== undefined) { fields.push('url = ?');   args.push(b.url != null ? String(b.url).slice(0, 2000) : null); }
  if (b.collection_id !== undefined) { fields.push('collection_id = ?'); args.push(ownCollectionId(b.collection_id, req.user.id)); }
  if (b.tags !== undefined) { fields.push('tags = ?'); args.push(b.tags != null ? String(b.tags).slice(0, 500) : null); }
  if (!fields.length) return res.json({ ok: true });
  args.push(req.params.id);
  db.prepare(`UPDATE student_materials SET ${fields.join(', ')} WHERE id = ?`).run(...args);
  res.json({ ok: true });
}

/* DELETE /api/materials/:id — remove one of the current user's items */
function remove(req, res) {
  const row = db.prepare('SELECT user_id FROM student_materials WHERE id = ?').get(req.params.id);
  if (!row) return res.status(404).json({ error: 'not found' });
  if (row.user_id !== req.user.id) return res.status(403).json({ error: 'forbidden' });
  db.prepare('DELETE FROM student_materials WHERE id = ?').run(req.params.id);
  res.json({ ok: true });
}

/* ── Collections (folders) ──────────────────────────────────────────── */

/* POST /api/materials/collections — create a folder */
function createCollection(req, res) {
  const name = String((req.body && req.body.name) || '').trim().slice(0, 120);
  if (!name) return res.status(400).json({ error: 'name required' });
  const color = req.body && req.body.color ? String(req.body.color).slice(0, 20) : null;
  const r = db.prepare(
    'INSERT INTO material_collections (user_id, name, color, sort_order) VALUES (?, ?, ?, ?)'
  ).run(req.user.id, name, color, Number(req.body && req.body.sortOrder) || 0);
  res.status(201).json({ id: Number(r.lastInsertRowid) });
}

/* PATCH /api/materials/collections/:id — rename / recolor / reorder */
function updateCollection(req, res) {
  const row = db.prepare('SELECT user_id FROM material_collections WHERE id = ?').get(req.params.id);
  if (!row) return res.status(404).json({ error: 'not found' });
  if (row.user_id !== req.user.id) return res.status(403).json({ error: 'forbidden' });
  const b = req.body || {};
  const fields = [], args = [];
  if (b.name !== undefined)      { fields.push('name = ?');       args.push(String(b.name || '').trim().slice(0, 120)); }
  if (b.color !== undefined)     { fields.push('color = ?');      args.push(b.color ? String(b.color).slice(0, 20) : null); }
  if (b.sortOrder !== undefined) { fields.push('sort_order = ?'); args.push(Number(b.sortOrder) || 0); }
  if (!fields.length) return res.json({ ok: true });
  args.push(req.params.id);
  db.prepare(`UPDATE material_collections SET ${fields.join(', ')} WHERE id = ?`).run(...args);
  res.json({ ok: true });
}

/* DELETE /api/materials/collections/:id — delete folder (materials kept, uncategorised) */
function deleteCollection(req, res) {
  const row = db.prepare('SELECT user_id FROM material_collections WHERE id = ?').get(req.params.id);
  if (!row) return res.status(404).json({ error: 'not found' });
  if (row.user_id !== req.user.id) return res.status(403).json({ error: 'forbidden' });
  db.prepare('DELETE FROM material_collections WHERE id = ?').run(req.params.id); // ON DELETE SET NULL
  res.json({ ok: true });
}

/* POST /api/materials/:id/share — teacher hands a material out to a class or
   a student. Each recipient gets an independent COPY (survives later edits/
   deletes by the teacher). Body: { classId } | { userId }. */
function share(req, res) {
  const mat = db.prepare('SELECT user_id, kind, title, body, url FROM student_materials WHERE id = ?').get(req.params.id);
  if (!mat) return res.status(404).json({ error: 'not found' });
  if (mat.user_id !== req.user.id && req.user.role !== 'admin') return res.status(403).json({ error: 'forbidden' });

  const b = req.body || {};
  let recipients = [];
  if (b.classId) {
    const cls = db.prepare('SELECT id, teacher_id FROM classes WHERE id = ?').get(b.classId);
    if (!cls) return res.status(404).json({ error: 'class not found' });
    if (cls.teacher_id !== req.user.id && req.user.role !== 'admin') return res.status(403).json({ error: 'not your class' });
    recipients = db.prepare('SELECT user_id FROM class_members WHERE class_id = ?').all(b.classId).map(r => r.user_id);
  } else if (b.userId) {
    const uid = Number(b.userId);
    if (!Number.isFinite(uid)) return res.status(400).json({ error: 'bad userId' });
    // Раздавать можно только своему ученику (в своём классе или в teacher_students).
    if (req.user.role !== 'admin') {
      const linked = db.prepare(
        `SELECT 1 FROM class_members cm JOIN classes c ON c.id = cm.class_id WHERE cm.user_id = ? AND c.teacher_id = ?
         UNION SELECT 1 FROM teacher_students WHERE student_id = ? AND teacher_id = ? LIMIT 1`
      ).get(uid, req.user.id, uid, req.user.id);
      if (!linked) return res.status(403).json({ error: 'Этот ученик не привязан к вам' });
    }
    recipients = [uid];
  } else {
    return res.status(400).json({ error: 'classId or userId required' });
  }

  const teacherName = (db.prepare('SELECT name FROM users WHERE id = ?').get(req.user.id) || {}).name || 'Учитель';
  const srcTitle = 'Раздатка: ' + teacherName;
  const ins = db.prepare(`INSERT INTO student_materials (user_id, kind, title, body, url, source_session_id, source_title) VALUES (?,?,?,?,?,NULL,?)`);
  let sent = 0;
  db.transaction(() => {
    for (const uid of recipients) {
      if (!uid || uid === req.user.id) continue;
      ins.run(uid, mat.kind, mat.title, mat.body, mat.url, srcTitle);
      try {
        emit(uid, { type: 'notification', notif_type: 'material_shared',
          message: `Новый материал от ${teacherName}: «${mat.title || 'материал'}»`, link: '/my-materials' });
      } catch (e) { /* ignore notify failure */ }
      sent++;
    }
  })();
  res.json({ ok: true, sent });
}

module.exports = { list, create, update, remove, createCollection, updateCollection, deleteCollection, share };