const express = require('express');
const router  = express.Router();
const { query, queryOne, exec } = require('../models/db');
const { authMiddleware } = require('../middleware/auth');

// ── Firebase Admin ─────────────────────────────────────────────────────────────
let firebaseAdmin = null;
let firebaseApp   = null;

function getMessaging() {
  if (firebaseApp) return firebaseAdmin.messaging(firebaseApp);
  const json = process.env.FIREBASE_SERVICE_ACCOUNT;
  if (!json) return null;
  try {
    firebaseAdmin = require('firebase-admin');
    const svc = JSON.parse(json);
    firebaseApp = firebaseAdmin.initializeApp({
      credential: firebaseAdmin.credential.cert(svc),
    });
    console.log('[Push] Firebase Admin initialised');
    return firebaseAdmin.messaging(firebaseApp);
  } catch (e) {
    console.error('[Push] Firebase Admin init failed:', e.message);
    return null;
  }
}

// ── Helpers ────────────────────────────────────────────────────────────────────

// Called from index.js socket push notifications
async function sendPushToUser(schema, userId, payload) {
  const messaging = getMessaging();
  if (!messaging) return;
  try {
    const subs = await query(schema,
      'SELECT * FROM push_subscriptions WHERE user_id = $1 AND fcm_token IS NOT NULL',
      [userId]
    );
    for (const sub of subs) {
      try {
        await messaging.send({
          token: sub.fcm_token,
          data: {
            title:   payload.title  || 'New Message',
            body:    payload.body   || '',
            url:     payload.url    || '/',
            groupId: payload.groupId ? String(payload.groupId) : '',
          },
          android: { priority: 'high' },
          webpush: { headers: { Urgency: 'high' } },
        });
      } catch (err) {
        // Remove stale tokens
        const stale = [
          'messaging/registration-token-not-registered',
          'messaging/invalid-registration-token',
          'messaging/invalid-argument',
        ];
        if (stale.includes(err.code)) {
          await exec(schema, 'DELETE FROM push_subscriptions WHERE id = $1', [sub.id]);
        }
      }
    }
  } catch (e) {
    console.error('[Push] sendPushToUser error:', e.message);
  }
}

// ── Routes ─────────────────────────────────────────────────────────────────────

// Public — frontend fetches this to initialise the Firebase JS SDK
router.get('/firebase-config', (req, res) => {
  const apiKey             = process.env.FIREBASE_API_KEY;
  const projectId          = process.env.FIREBASE_PROJECT_ID;
  const messagingSenderId  = process.env.FIREBASE_MESSAGING_SENDER_ID;
  const appId              = process.env.FIREBASE_APP_ID;
  const vapidKey           = process.env.FIREBASE_VAPID_KEY;

  if (!apiKey || !projectId || !messagingSenderId || !appId) {
    return res.status(503).json({ error: 'FCM not configured' });
  }
  res.json({ apiKey, projectId, messagingSenderId, appId, vapidKey });
});

// Register / refresh an FCM token for the logged-in user
router.post('/subscribe', authMiddleware, async (req, res) => {
  const { fcmToken } = req.body;
  if (!fcmToken) return res.status(400).json({ error: 'fcmToken required' });
  try {
    const device = req.device || 'desktop';
    await exec(req.schema,
      'DELETE FROM push_subscriptions WHERE user_id = $1 AND device = $2',
      [req.user.id, device]
    );
    await exec(req.schema,
      'INSERT INTO push_subscriptions (user_id, device, fcm_token) VALUES ($1, $2, $3)',
      [req.user.id, device, fcmToken]
    );
    res.json({ success: true });
  } catch (e) { res.status(500).json({ error: e.message }); }
});

// Remove the FCM token for the logged-in user / device
router.post('/unsubscribe', authMiddleware, async (req, res) => {
  try {
    const device = req.device || 'desktop';
    await exec(req.schema,
      'DELETE FROM push_subscriptions WHERE user_id = $1 AND device = $2',
      [req.user.id, device]
    );
    res.json({ success: true });
  } catch (e) { res.status(500).json({ error: e.message }); }
});

module.exports = { router, sendPushToUser };