const { Client, LocalAuth } = require('whatsapp-web.js');
const qrcode = require('qrcode-terminal');
const qrcodeLib = require('qrcode');
const cron = require('node-cron');
const http = require('http');
const fs = require('fs');
const path = require('path');

const CONTACTS_PATH = path.join(__dirname, '..', 'config', 'contacts.json');
const SETTINGS_PATH = path.join(__dirname, '..', 'config', 'settings.json');
const DATA_PATH = path.join(__dirname, '..', 'data');

let currentQR = null;
let isReady = false;

function loadSettings() {
  return JSON.parse(fs.readFileSync(SETTINGS_PATH, 'utf8'));
}

function loadContacts() {
  return JSON.parse(fs.readFileSync(CONTACTS_PATH, 'utf8'));
}

// Gibt den Kontakt zurück der im angegebenen Monat dran ist (wiederholt sich jedes Jahr).
function getContactForMonth(year, month) {
  const settings = loadSettings();
  const contacts = loadContacts();

  const schedule = settings.schedule;
  if (!Array.isArray(schedule) || schedule.length !== 12) {
    console.log('schedule in settings.json muss ein Array mit 12 Einträgen sein.');
    return null;
  }

  const contactId = schedule[month - 1];
  if (!contactId) {
    console.log(`Monat ${month}/${year}: kein Kontakt (null) — nichts zu tun.`);
    return null;
  }

  const contact = contacts.find(c => c.id === contactId);
  if (!contact) {
    console.log(`Kontakt-ID "${contactId}" nicht in contacts.json gefunden.`);
    return null;
  }

  return contact;
}

async function sendReminders(overrideYear = null, overrideMonth = null) {
  const settings = loadSettings();
  const now = new Date();
  const year  = overrideYear  ?? now.getFullYear();
  const month = overrideMonth ?? (now.getMonth() + 1);

  const monthName = new Date(year, month - 1, 1).toLocaleString('de-DE', { month: 'long' });
  const contact = getContactForMonth(year, month);

  if (!contact) {
    return { skipped: true, reason: `Kein Kontakt für ${monthName} ${year}` };
  }

  const vorname = contact.name.split(' ')[0];
  const message = settings.message
    .replace(/{vorname}/g,  vorname)
    .replace(/{name}/g,     contact.name)
    .replace(/{amount}/g,   settings.amount ?? '')
    .replace(/{currency}/g, settings.currency ?? '')
    .replace(/{month}/g,    monthName)
    .replace(/{year}/g,     year);

  const phone = contact.phone.replace(/\D/g, '');
  const chatId = `${phone}@c.us`;

  console.log(`[${monthName} ${year}] Sende an: ${contact.name} (${contact.phone})`);

  try {
    await client.sendMessage(chatId, message);
    console.log(`[OK] Nachricht gesendet.`);
    return { sent: true, contact: contact.name };
  } catch (err) {
    console.error(`[FEHLER] ${err.message}`);
    return { sent: false, error: err.message };
  }
}

// Web-Interface
const server = http.createServer(async (req, res) => {
  const url = new URL(req.url, 'http://localhost');

  if (url.pathname === '/qr') {
    if (!currentQR) {
      res.writeHead(200, { 'Content-Type': 'text/html; charset=utf-8' });
      return res.end(htmlPage('Status', isReady
        ? '<p style="color:green;font-size:1.1em">✓ Verbunden und bereit</p><p><a href="/send-now">Erinnerung jetzt senden</a></p>'
        : '<p>Kein QR-Code verfügbar — Client startet noch, bitte kurz warten...</p>'
      ));
    }
    const qrDataUrl = await qrcodeLib.toDataURL(currentQR);
    res.writeHead(200, { 'Content-Type': 'text/html; charset=utf-8' });
    return res.end(htmlPage('QR-Code scannen', `
      <p>Öffne WhatsApp &rarr; <strong>Verknüpfte Geräte</strong> &rarr; <strong>Gerät verknüpfen</strong></p>
      <img src="${qrDataUrl}" style="width:280px;height:280px;border:1px solid #ddd;border-radius:8px;" />
      <p><small>Seite neu laden falls der Code abgelaufen ist.</small></p>
    `));
  }

  if (url.pathname === '/send-now') {
    if (!isReady) {
      res.writeHead(503, { 'Content-Type': 'text/html; charset=utf-8' });
      return res.end(htmlPage('Nicht bereit', '<p>Client ist noch nicht verbunden. Erst QR-Code scannen.</p>'));
    }
    // Optionale Query-Parameter: ?year=2026&month=5
    const year  = url.searchParams.has('year')  ? parseInt(url.searchParams.get('year'))  : null;
    const month = url.searchParams.has('month') ? parseInt(url.searchParams.get('month')) : null;
    const result = await sendReminders(year, month);
    res.writeHead(200, { 'Content-Type': 'text/html; charset=utf-8' });
    if (result.skipped) {
      return res.end(htmlPage('Übersprungen', `<p style="color:orange">⏭ ${result.reason}</p><p><a href="/">Zurück</a></p>`));
    }
    return res.end(htmlPage(result.sent ? 'Gesendet' : 'Fehler', `
      ${result.sent
        ? `<p style="color:green">✓ Nachricht an ${result.contact} gesendet</p>`
        : `<p style="color:red">✗ Fehler: ${result.error}</p>`}
      <p><a href="/">Zurück</a></p>
    `));
  }

  if (url.pathname === '/status') {
    res.writeHead(200, { 'Content-Type': 'application/json' });
    return res.end(JSON.stringify({ ready: isReady, qr_pending: !!currentQR }));
  }

  // Startseite mit Monatsübersicht
  let scheduleHtml = '';
  try {
    const settings = loadSettings();
    const contacts = loadContacts();
    const now = new Date();
    const thisYear = now.getFullYear();
    const thisMonth = now.getMonth() + 1;
    const monthNames = ['', 'Januar','Februar','März','April','Mai','Juni','Juli','August','September','Oktober','November','Dezember'];
    const plan = settings.schedule ?? [];
    const rows = plan.map((id, i) => {
      const m = i + 1;
      const contact = id ? contacts.find(c => c.id === id) : null;
      const isCurrent = m === thisMonth;
      return `<tr style="${isCurrent ? 'font-weight:bold;background:#e7f7f0' : ''}">
        <td style="padding:4px 12px">${monthNames[m]}</td>
        <td style="padding:4px 12px">${contact ? contact.name : '—'}</td>
        ${isCurrent ? '<td style="padding:4px 12px;color:green">← aktueller Monat</td>' : '<td></td>'}
      </tr>`;
    }).join('');
    scheduleHtml = `<h2>Plan ${thisYear}</h2><table border="0" cellspacing="0">${rows}</table>`;
  } catch (e) {
    scheduleHtml = `<p style="color:red">Fehler beim Laden des Plans: ${e.message}</p>`;
  }

  res.writeHead(200, { 'Content-Type': 'text/html; charset=utf-8' });
  res.end(htmlPage('WhatsApp Reminder', `
    <p>Status: ${isReady
      ? '<span style="color:green">✓ Verbunden</span>'
      : currentQR
        ? '<span style="color:orange"><a href="/qr">QR-Code scannen</a></span>'
        : '<span style="color:gray">Startet...</span>'}</p>
    <p><a href="/send-now">▶ Erinnerung für diesen Monat jetzt senden</a></p>
    ${scheduleHtml}
  `));
});

function htmlPage(title, body) {
  return `<!DOCTYPE html><html><head>
    <meta charset="utf-8"><title>${title} – WhatsApp Reminder</title>
    <style>body{font-family:sans-serif;max-width:650px;margin:40px auto;padding:0 20px}
    a{color:#075e54}h1,h2{color:#075e54}table{border-collapse:collapse}
    td{border-bottom:1px solid #eee}</style>
  </head><body><h1>${title}</h1>${body}</body></html>`;
}

server.listen(3000, () => {
  console.log('Web-Interface: http://localhost:3000');
  console.log('QR-Code:       http://localhost:3000/qr');
});

// WhatsApp Client
const client = new Client({
  authStrategy: new LocalAuth({ dataPath: DATA_PATH }),
  puppeteer: {
    executablePath: process.env.PUPPETEER_EXECUTABLE_PATH || '/usr/bin/chromium',
    args: [
      '--no-sandbox',
      '--disable-setuid-sandbox',
      '--disable-dev-shm-usage',
      '--disable-accelerated-2d-canvas',
      '--no-first-run',
      '--no-zygote',
      '--single-process',
      '--disable-gpu'
    ]
  }
});

client.on('qr', (qr) => {
  currentQR = qr;
  console.log('\n>>> QR-Code bereit: http://localhost:3000/qr <<<');
  qrcode.generate(qr, { small: true });
});

client.on('authenticated', () => {
  currentQR = null;
  console.log('Authentifiziert.');
});

client.on('ready', () => {
  isReady = true;
  const settings = loadSettings();
  const schedule = settings.cron || '0 9 1 * *';
  const tz = settings.timezone || 'Europe/Zurich';

  cron.schedule(schedule, async () => {
    const now = new Date();
    console.log(`[CRON] ${now.toLocaleString('de-DE')} — prüfe Monatsplan...`);
    await sendReminders();
  }, { timezone: tz });

  console.log(`WhatsApp bereit. Cron: "${schedule}" (${tz})`);
});

client.on('disconnected', (reason) => {
  console.log('Verbindung getrennt:', reason);
  isReady = false;
  process.exit(1);
});

client.initialize();