const express   = require('express');
const webpush   = require('web-push');
const db        = require('../db');
const { authenticate } = require('../middleware/auth');
const router    = express.Router();

// ── VAPID-Setup (einmalig, in DB gespeichert) ─────────────────────────────────
function getVapidKeys() {
  const pub  = db.prepare("SELECT value FROM admin_settings WHERE key='vapid_public'").get();
  const priv = db.prepare("SELECT value FROM admin_settings WHERE key='vapid_private'").get();
  if (pub && priv) return { publicKey: pub.value, privateKey: priv.value };
  const keys = webpush.generateVAPIDKeys();
  db.prepare("INSERT OR REPLACE INTO admin_settings (key,value) VALUES ('vapid_public',?)").run(keys.publicKey);
  db.prepare("INSERT OR REPLACE INTO admin_settings (key,value) VALUES ('vapid_private',?)").run(keys.privateKey);
  return keys;
}
const vapid = getVapidKeys();
webpush.setVapidDetails('mailto:admin@dickendock.local', vapid.publicKey, vapid.privateKey);

// GET /vapid-key – öffentlicher VAPID-Schlüssel für den Browser
router.get('/vapid-key', authenticate, (req, res) => {
  res.json({ publicKey: vapid.publicKey });
});

// ── Öffentliche Schlüssel ─────────────────────────────────────────────────────
// POST /keys – eigenen öffentlichen Schlüssel speichern
router.post('/keys', authenticate, (req, res) => {
  const { publicKey } = req.body;
  if (!publicKey) return res.status(400).json({ error: 'Kein Schlüssel' });
  db.prepare('INSERT OR REPLACE INTO user_keys (user_id,public_key,updated_at) VALUES (?,?,CURRENT_TIMESTAMP)').run(req.user.id, publicKey);
  res.json({ success: true });
});

// GET /keys/:username – öffentlichen Schlüssel eines Users abrufen
router.get('/keys/:username', authenticate, (req, res) => {
  const user = db.prepare('SELECT id FROM users WHERE username=?').get(req.params.username);
  if (!user) return res.status(404).json({ error: 'User nicht gefunden' });
  const key = db.prepare('SELECT public_key FROM user_keys WHERE user_id=?').get(user.id);
  if (!key) return res.status(404).json({ error: 'Noch kein Schlüssel hinterlegt' });
  res.json({ publicKey: key.public_key });
});

// ── Push-Subscriptions ────────────────────────────────────────────────────────
router.post('/subscribe', authenticate, (req, res) => {
  const { endpoint, keys } = req.body;
  if (!endpoint || !keys?.p256dh || !keys?.auth) return res.status(400).json({ error: 'Ungültige Subscription' });
  db.prepare('INSERT OR REPLACE INTO push_subscriptions (user_id,endpoint,p256dh,auth) VALUES (?,?,?,?)')
    .run(req.user.id, endpoint, keys.p256dh, keys.auth);
  res.json({ success: true });
});

router.delete('/subscribe', authenticate, (req, res) => {
  db.prepare('DELETE FROM push_subscriptions WHERE user_id=?').run(req.user.id);
  res.json({ success: true });
});

// ── Nachrichten ───────────────────────────────────────────────────────────────
// GET /conversations – alle Gesprächspartner mit ungelesener Anzahl
router.get('/conversations', authenticate, (req, res) => {
  const uid = req.user.id;
  const convs = db.prepare(`
    SELECT
      CASE WHEN m.sender_id=? THEN m.recipient_id ELSE m.sender_id END AS partner_id,
      u.username AS partner_name,
      MAX(m.created_at) AS last_at,
      COUNT(CASE WHEN m.recipient_id=? AND m.deleted_by_recipient=0 THEN 1 END) AS unread
    FROM messages m
    JOIN users u ON u.id=(CASE WHEN m.sender_id=? THEN m.recipient_id ELSE m.sender_id END)
    WHERE (m.sender_id=? AND m.deleted_by_sender=0)
       OR (m.recipient_id=? AND m.deleted_by_recipient=0)
    GROUP BY partner_id
    ORDER BY last_at DESC
  `).all(uid, uid, uid, uid, uid);
  res.json(convs);
});

// GET /unread-count – Gesamtanzahl ungelesener Nachrichten
router.get('/unread-count', authenticate, (req, res) => {
  const count = db.prepare('SELECT COUNT(*) c FROM messages WHERE recipient_id=? AND deleted_by_recipient=0').get(req.user.id).c;
  res.json({ count });
});

// GET /with/:username – Nachrichten mit einem User
router.get('/with/:username', authenticate, (req, res) => {
  const uid     = req.user.id;
  const partner = db.prepare('SELECT id FROM users WHERE username=?').get(req.params.username);
  if (!partner) return res.status(404).json({ error: 'User nicht gefunden' });
  const msgs = db.prepare(`
    SELECT m.id, m.sender_id, m.encrypted_content, m.iv, m.created_at,
      s.username AS sender_name
    FROM messages m
    JOIN users s ON s.id=m.sender_id
    WHERE ((m.sender_id=? AND m.recipient_id=? AND m.deleted_by_sender=0)
        OR (m.sender_id=? AND m.recipient_id=? AND m.deleted_by_recipient=0))
    ORDER BY m.created_at ASC
  `).all(uid, partner.id, partner.id, uid);
  res.json(msgs);
});

// GET /users – alle User außer sich selbst (für neues Gespräch)
router.get('/users', authenticate, (req, res) => {
  const users = db.prepare('SELECT id,username FROM users WHERE id!=? ORDER BY username').all(req.user.id);
  res.json(users);
});

// POST /send – verschlüsselte Nachricht senden
router.post('/send', authenticate, async (req, res) => {
  const { recipient_username, encrypted_content, iv } = req.body;
  if (!recipient_username || !encrypted_content || !iv)
    return res.status(400).json({ error: 'Fehlende Felder' });
  const recipient = db.prepare('SELECT id FROM users WHERE username=?').get(recipient_username);
  if (!recipient) return res.status(404).json({ error: 'Empfänger nicht gefunden' });

  const r = db.prepare('INSERT INTO messages (sender_id,recipient_id,encrypted_content,iv) VALUES (?,?,?,?)')
    .run(req.user.id, recipient.id, encrypted_content, iv);

  // Push-Benachrichtigung an Empfänger
  const subs = db.prepare('SELECT * FROM push_subscriptions WHERE user_id=?').all(recipient.id);
  const sender = db.prepare('SELECT username FROM users WHERE id=?').get(req.user.id);
  for (const sub of subs) {
    try {
      await webpush.sendNotification(
        { endpoint: sub.endpoint, keys: { p256dh: sub.p256dh, auth: sub.auth } },
        JSON.stringify({ title: `Nachricht von ${sender.username}`, body: '🔒 Verschlüsselte Nachricht', icon: '/favicon.svg' })
      );
    } catch(e) {
      if (e.statusCode === 410) db.prepare('DELETE FROM push_subscriptions WHERE endpoint=?').run(sub.endpoint);
    }
  }

  res.json({ id: r.lastInsertRowid, success: true });
});

// DELETE /:id – Nachricht für sich löschen
router.delete('/:id', authenticate, (req, res) => {
  const uid = req.user.id;
  const msg = db.prepare('SELECT * FROM messages WHERE id=?').get(req.params.id);
  if (!msg) return res.status(404).json({ error: 'Nicht gefunden' });
  if (msg.sender_id !== uid && msg.recipient_id !== uid)
    return res.status(403).json({ error: 'Kein Zugriff' });

  if (msg.sender_id === uid) db.prepare('UPDATE messages SET deleted_by_sender=1 WHERE id=?').run(msg.id);
  else db.prepare('UPDATE messages SET deleted_by_recipient=1 WHERE id=?').run(msg.id);

  // Wenn beide gelöscht → komplett entfernen
  const updated = db.prepare('SELECT * FROM messages WHERE id=?').get(msg.id);
  if (updated?.deleted_by_sender && updated?.deleted_by_recipient)
    db.prepare('DELETE FROM messages WHERE id=?').run(msg.id);

  res.json({ success: true });
});

// DELETE /conversation/:username – ganzes Gespräch für sich löschen
router.delete('/conversation/:username', authenticate, (req, res) => {
  const uid     = req.user.id;
  const partner = db.prepare('SELECT id FROM users WHERE username=?').get(req.params.username);
  if (!partner) return res.status(404).json({ error: 'User nicht gefunden' });

  db.prepare('UPDATE messages SET deleted_by_sender=1 WHERE sender_id=? AND recipient_id=?').run(uid, partner.id);
  db.prepare('UPDATE messages SET deleted_by_recipient=1 WHERE recipient_id=? AND sender_id=?').run(uid, partner.id);
  // Komplett löschen wenn beide weg
  db.prepare('DELETE FROM messages WHERE sender_id IN (?,?) AND recipient_id IN (?,?) AND deleted_by_sender=1 AND deleted_by_recipient=1')
    .run(uid, partner.id, uid, partner.id);

  res.json({ success: true });
});

module.exports = router;