/**
 * BookingWA — Servizio WhatsApp Baileys per Farmacia Ianni
 * Espone REST: GET /status, GET /qr, POST /send, POST /disconnect
 * Sessione persistente in /data/auth per sopravvivere ai restart.
 */
const express = require('express');
const { default: makeWASocket, useMultiFileAuthState, DisconnectReason, fetchLatestBaileysVersion } = require('@whiskeysockets/baileys');
const qrcode = require('qrcode');
const pino = require('pino');

const app = express();
app.use(express.json());

const PORT = process.env.PORT || 3100;
const AUTH_DIR = '/data/auth';
const logger = pino({ level: 'warn' });

let sock = null;
let currentQR = null;
let qrGeneratedAt = null;
let qrAttempt = 0;
let connectionState = 'disconnected';
let phoneNumber = null;
let retryCount = 0;
const MAX_RETRIES = 5;
const QR_TTL_SEC = 20;

async function startSocket() {
  const { state, saveCreds } = await useMultiFileAuthState(AUTH_DIR);
  const { version } = await fetchLatestBaileysVersion();

  sock = makeWASocket({
    version,
    auth: state,
    logger,
    printQRInTerminal: false,
    browser: ['Farmacia Ianni', 'Chrome', '120.0'],
    connectTimeoutMs: 30000,
    defaultQueryTimeoutMs: 30000,
    generateHighQualityLinkPreview: false,
    syncFullHistory: false,
    qrTimeout: 60000,
  });

  sock.ev.on('creds.update', saveCreds);

  sock.ev.on('connection.update', async (update) => {
    const { connection, lastDisconnect, qr } = update;

    if (qr) {
      currentQR = await qrcode.toDataURL(qr, { width: 280, margin: 2 });
      qrGeneratedAt = Date.now();
      qrAttempt++;
      connectionState = 'connecting';
      console.log(`[WA] QR #${qrAttempt} generato — scade tra ${QR_TTL_SEC}s`);
    }

    if (connection === 'close') {
      currentQR = null;
      qrGeneratedAt = null;
      const statusCode = lastDisconnect?.error?.output?.statusCode;
      const shouldReconnect = statusCode !== DisconnectReason.loggedOut;

      if (statusCode === DisconnectReason.loggedOut) {
        connectionState = 'disconnected';
        phoneNumber = null;
        retryCount = 0;
        qrAttempt = 0;
        console.log('[WA] Disconnesso (logout). Serve nuovo QR.');
        const fs = require('fs');
        fs.rmSync(AUTH_DIR, { recursive: true, force: true });
        fs.mkdirSync(AUTH_DIR, { recursive: true });
      } else if (shouldReconnect && retryCount < MAX_RETRIES) {
        retryCount++;
        const delay = Math.min(retryCount * 2000, 15000);
        console.log(`[WA] Riconnessione ${retryCount}/${MAX_RETRIES} in ${delay}ms...`);
        connectionState = 'connecting';
        setTimeout(startSocket, delay);
      } else {
        connectionState = 'disconnected';
        console.log('[WA] Connessione persa, max retry raggiunto.');
      }
    }

    if (connection === 'open') {
      connectionState = 'connected';
      currentQR = null;
      qrGeneratedAt = null;
      retryCount = 0;
      qrAttempt = 0;
      phoneNumber = sock.user?.id?.split(':')[0] || sock.user?.id;
      console.log(`[WA] Connesso come ${phoneNumber}`);
    }
  });
}

// ── API ──

app.get('/status', (req, res) => {
  res.json({
    connected: connectionState === 'connected',
    state: connectionState,
    phone: phoneNumber,
    message: connectionState === 'connected'
      ? `Connesso come ${phoneNumber}`
      : connectionState === 'connecting'
        ? 'In attesa di scansione QR...'
        : 'Disconnesso'
  });
});

app.get('/qr', (req, res) => {
  if (connectionState === 'connected') {
    return res.json({ qr: null, expired: false, message: 'Già connesso' });
  }

  if (currentQR && qrGeneratedAt) {
    const elapsed = (Date.now() - qrGeneratedAt) / 1000;
    const remaining = Math.max(0, Math.round(QR_TTL_SEC - elapsed));

    if (remaining <= 0) {
      return res.json({
        qr: null,
        expired: true,
        attempt: qrAttempt,
        message: 'QR scaduto — in attesa del prossimo...'
      });
    }

    return res.json({
      qr: currentQR,
      expired: false,
      expires_in: remaining,
      ttl: QR_TTL_SEC,
      attempt: qrAttempt,
    });
  }

  // Se non c'è QR e non siamo connessi, avvia socket
  if (connectionState === 'disconnected') {
    startSocket().catch(console.error);
    return res.json({ qr: null, expired: false, message: 'Avvio connessione... riprova tra 5 secondi' });
  }

  res.json({ qr: null, expired: false, message: 'QR in generazione...' });
});

app.post('/send', async (req, res) => {
  const { to, text } = req.body;
  if (!to || !text) return res.status(400).json({ error: 'Servono "to" e "text"' });
  if (connectionState !== 'connected' || !sock) return res.status(503).json({ error: 'WhatsApp non connesso' });

  try {
    let jid = to.replace(/[^0-9]/g, '');
    if (!jid.endsWith('@s.whatsapp.net')) jid = jid + '@s.whatsapp.net';
    await sock.sendMessage(jid, { text });
    console.log(`[WA] Messaggio inviato a ${to}`);
    res.json({ ok: true, to, message: 'Inviato' });
  } catch (e) {
    console.error('[WA] Errore invio:', e.message);
    res.status(500).json({ error: e.message });
  }
});

app.post('/disconnect', async (req, res) => {
  try {
    if (sock) { await sock.logout(); sock = null; }
    connectionState = 'disconnected';
    phoneNumber = null;
    currentQR = null;
    qrGeneratedAt = null;
    qrAttempt = 0;
    res.json({ ok: true, message: 'Disconnesso' });
  } catch (e) {
    res.status(500).json({ error: e.message });
  }
});

app.get('/health', (req, res) => {
  res.json({ status: 'ok', service: 'booking-wa', state: connectionState });
});

// ── START ──
app.listen(PORT, '0.0.0.0', () => {
  console.log(`[WA] Servizio avviato su :${PORT}`);
  const fs = require('fs');
  if (fs.existsSync(AUTH_DIR) && fs.readdirSync(AUTH_DIR).length > 0) {
    console.log('[WA] Sessione trovata, riconnessione...');
    startSocket().catch(console.error);
  } else {
    console.log('[WA] Nessuna sessione. Chiama GET /qr per iniziare.');
    fs.mkdirSync(AUTH_DIR, { recursive: true });
  }
});