const express = require('express');
const crypto  = require('crypto');
const router  = express.Router();
const dns     = require('dns').promises;
const db      = require('../config/database');

// ============================================
// E-Mail Validierung via DNS MX-Record
// ============================================
async function verifyEmailDomain(email) {
  const emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
  if (!emailRegex.test(email)) return { valid: false, reason: 'Ungültiges E-Mail-Format' };
  const domain = email.split('@')[1];
  try {
    const records = await dns.resolveMx(domain);
    if (records && records.length > 0) return { valid: true };
    return { valid: false, reason: 'Domain hat keine E-Mail-Server (MX-Records fehlen)' };
  } catch (err) {
    return { valid: false, reason: 'E-Mail-Domain konnte nicht verifiziert werden' };
  }
}

// ============================================
// IBAN Validierung (Modulo-97)
// ============================================
const IBAN_LENGTHS = {
  AL:28,AD:24,AT:20,AZ:28,BH:22,BE:16,BA:20,BR:29,BG:22,CR:22,HR:21,
  CY:28,CZ:24,DK:18,DO:28,EE:20,FO:18,FI:18,FR:27,GE:22,DE:22,GI:23,
  GL:18,GT:28,HU:28,IS:26,IE:22,IL:23,IT:27,JO:30,KZ:20,KW:30,LV:21,
  LB:28,LI:21,LT:20,LU:20,MK:19,MT:31,MR:27,MU:30,MC:27,MD:24,ME:22,
  NL:18,NO:15,PK:24,PS:29,PL:28,PT:25,QA:29,RO:24,SM:27,SA:24,RS:22,
  SK:24,SI:19,ES:24,SE:24,CH:21,TN:24,TR:26,AE:23,GB:22,VG:24
};
function validateIBANServer(iban) {
  if (!iban) return { valid: true };
  const clean = iban.replace(/\s/g, '').toUpperCase();
  if (clean.length < 5) return { valid: false, error: 'IBAN zu kurz' };
  const country = clean.substring(0, 2);
  if (!/^[A-Z]{2}$/.test(country)) return { valid: false, error: 'Ungültiger Ländercode' };
  const expectedLen = IBAN_LENGTHS[country];
  if (!expectedLen) return { valid: false, error: 'Ländercode nicht unterstützt' };
  if (clean.length !== expectedLen) return { valid: false, error: country + '-IBAN muss ' + expectedLen + ' Zeichen haben' };
  const rearranged = clean.substring(4) + clean.substring(0, 4);
  const numeric = rearranged.split('').map(c => {
    const code = c.charCodeAt(0);
    return code >= 65 ? (code - 55).toString() : c;
  }).join('');
  let remainder = 0;
  for (let i = 0; i < numeric.length; i++) {
    remainder = (remainder * 10 + parseInt(numeric[i])) % 97;
  }
  if (remainder !== 1) return { valid: false, error: 'IBAN Prüfziffer ungültig' };
  return { valid: true };
}

// POST /api/verify-email
router.post('/verify-email', async (req, res) => {
  const { email } = req.body;
  if (!email) return res.json({ valid: false, reason: 'Keine E-Mail angegeben' });
  const result = await verifyEmailDomain(email);
  res.json(result);
});

// POST /api/submit-membership
router.post('/submit-membership', async (req, res) => {
  try {
    const {
      tariff_id, salutation, title, first_name, last_name, birth_date,
      email, phone, street, address_addition, zip, city,
      bank_name, account_holder, iban,
      sepa_accepted, agb_accepted, datenschutz_accepted, data_correct,
      guardian_consent
    } = req.body;

    // Pflichtfelder prüfen
    if (!tariff_id || !first_name || !last_name || !birth_date || !email || !street || !zip || !city) {
      return res.json({ success: false, error: 'Bitte alle Pflichtfelder ausfüllen.' });
    }
    if (!agb_accepted || !datenschutz_accepted || !data_correct) {
      return res.json({ success: false, error: 'Bitte alle Einverständniserklärungen bestätigen.' });
    }

    // E-Mail validieren
    const emailCheck = await verifyEmailDomain(email);
    if (!emailCheck.valid) {
      return res.json({ success: false, error: 'E-Mail-Adresse ist nicht erreichbar: ' + emailCheck.reason });
    }

    // IBAN prüfen
    if (iban && iban.trim()) {
      const ibanCheck = validateIBANServer(iban.trim());
      if (!ibanCheck.valid) {
        return res.json({ success: false, error: 'IBAN ungültig: ' + ibanCheck.error });
      }
    }

    // Alter berechnen
    const birthDateObj = new Date(birth_date);
    const today = new Date();
    let age = today.getFullYear() - birthDateObj.getFullYear();
    const mo = today.getMonth() - birthDateObj.getMonth();
    if (mo < 0 || (mo === 0 && today.getDate() < birthDateObj.getDate())) age--;

    const is_minor = age < 18 ? 1 : 0;

    if (is_minor && !guardian_consent) {
      return res.json({ success: false, error: 'Bei Minderjährigen ist die Einverständniserklärung der Erziehungsberechtigten erforderlich.' });
    }
    if (age < 14) {
      return res.json({ success: false, error: 'Das Mindestalter für eine Mitgliedschaft beträgt 14 Jahre.' });
    }

    // Tarif laden — MUSS vor Berechnungen stehen
    const [tariffs] = await db.query('SELECT * FROM tariffs WHERE id = ? AND active = 1', [tariff_id]);
    if (tariffs.length === 0) {
      return res.json({ success: false, error: 'Ungültiger oder inaktiver Tarif.' });
    }
    const tariff = tariffs[0];

    // Startpaket-Preis
    const startPackagePrice = parseFloat(tariff.start_package_price) || 35.00;

    // Vertragsbeginn = heute + 15 Tage
    const contractStart = new Date();
    contractStart.setDate(contractStart.getDate() + 15);

    // Anteiligen ersten Monatsbeitrag berechnen
    const daysInMonth    = new Date(contractStart.getFullYear(), contractStart.getMonth() + 1, 0).getDate();
    const remainingDays  = daysInMonth - contractStart.getDate() + 1;
    const dailyRate      = parseFloat(tariff.price_monthly) / daysInMonth;
    const partialMonth   = Math.round(dailyRate * remainingDays * 100) / 100;

    // Erste Zahlung = anteiliger Monat + Startpaket
    const firstPaymentAmt = Math.round((partialMonth + startPackagePrice) * 100) / 100;

    // Vertragsende
    const contractEnd = new Date(contractStart);
    contractEnd.setMonth(contractEnd.getMonth() + tariff.duration_months);
    contractEnd.setDate(contractEnd.getDate() - 1);

    // Zugangstoken generieren
    const access_token = crypto.randomBytes(16).toString('hex');

    // In DB speichern
    // Spalten: 26, Werte: 26
    await db.query(`
      INSERT INTO memberships 
        (tariff_id, salutation, title, first_name, last_name, birth_date,
         email, phone, street, address_addition, zip, city,
         bank_name, account_holder, iban,
         sepa_accepted, agb_accepted, datenschutz_accepted, data_correct,
         guardian_consent, is_minor, access_token,
         agreed_price, agreed_duration,
         start_package_price,
         signup_date, contract_start, contract_end, effective_end,
         first_payment_date, first_payment_amt)
      VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
    `, [
      tariff_id, salutation, title || '', first_name, last_name, birth_date,
      email, phone || '', street, address_addition || '', zip, city,
      bank_name || '', account_holder || '', iban || '',
      sepa_accepted ? 1 : 0, agb_accepted ? 1 : 0,
      datenschutz_accepted ? 1 : 0, data_correct ? 1 : 0,
      guardian_consent ? 1 : 0, is_minor, access_token,
      tariff.price_monthly, tariff.duration_months,
      startPackagePrice,
      today.toISOString().split('T')[0],
      contractStart.toISOString().split('T')[0],
      contractEnd.toISOString().split('T')[0],
      contractEnd.toISOString().split('T')[0],
      contractStart.toISOString().split('T')[0],
      firstPaymentAmt
    ]);

    res.json({ success: true });

  } catch (err) {
    console.error('Submit error:', err);
    res.json({ success: false, error: 'Serverfehler. Bitte versuche es später erneut.' });
  }
});

module.exports = router;