const express = require('express');
const router = express.Router();
const db = require('../config/database');
const { requireAdmin } = require('../middleware/auth');

// ============================================
// GET /admin/finance – Übersicht
// ============================================
router.get('/', requireAdmin, async (req, res) => {
  try {
    // Mahngebühr aus Einstellungen
    const [settingRows] = await db.query("SELECT value FROM settings WHERE key_name='dunning_fee'");
    const dunningFee = settingRows.length ? parseFloat(settingRows[0].value) : 7.50;

    // Gesamtumsatz
    const [totalRevenue] = await db.query(`
      SELECT 
        COALESCE(SUM(CASE WHEN status='paid' THEN amount ELSE 0 END), 0) as paid_total,
        COALESCE(SUM(CASE WHEN status='open' THEN amount ELSE 0 END), 0) as open_total,
        COALESCE(SUM(amount), 0) as gross_total,
        COUNT(*) as invoice_count
      FROM invoices
    `);

    // Monatlicher Umsatz (letzte 12 Monate)
    const [monthlyRevenue] = await db.query(`
      SELECT 
        CONVERT(period USING utf8mb4) as period,
        SUM(CASE WHEN status='paid' THEN amount ELSE 0 END) as paid,
        SUM(CASE WHEN status='open' THEN amount ELSE 0 END) as open_amount,
        SUM(amount) as total,
        COUNT(*) as count
      FROM invoices
      GROUP BY CONVERT(period USING utf8mb4)
      ORDER BY period DESC
      LIMIT 12
    `);

    // Offene Posten
    const [openInvoices] = await db.query(`
      SELECT i.*, m.first_name, m.last_name, m.email, m.phone,
             t.name as tariff_name
      FROM invoices i
      JOIN memberships m ON i.membership_id = m.id
      LEFT JOIN tariffs t ON m.tariff_id = t.id
      WHERE i.status = 'open'
      ORDER BY i.period ASC, m.last_name ASC
    `);

    // Rückläufer
    const [chargebacks] = await db.query(`
      SELECT c.*, m.first_name, m.last_name, m.email
      FROM chargebacks c
      JOIN memberships m ON c.membership_id = m.id
      ORDER BY c.chargeback_date DESC
    `);

    // Mahngebühren
    const [dunnings] = await db.query(`
      SELECT d.*, m.first_name, m.last_name, m.email
      FROM dunning_fees d
      JOIN memberships m ON d.membership_id = m.id
      ORDER BY d.issued_date DESC
    `);

    // Mahngebühren Summen
    const [dunningStats] = await db.query(`
      SELECT 
        COALESCE(SUM(CASE WHEN status='open' THEN amount ELSE 0 END), 0) as open_total,
        COALESCE(SUM(CASE WHEN status='paid' THEN amount ELSE 0 END), 0) as paid_total,
        COUNT(CASE WHEN status='open' THEN 1 END) as open_count
      FROM dunning_fees
    `);

    // Rückläufer Summen
    const [chargebackStats] = await db.query(`
      SELECT 
        COUNT(*) as total,
        COUNT(CASE WHEN status='open' THEN 1 END) as open_count,
        COALESCE(SUM(amount), 0) as total_amount
      FROM chargebacks
    `);

    // Auslaufende Verträge (nächste 3 Monate)
    const [expiringContracts] = await db.query(`
      SELECT m.*, t.name as tariff_name, t.price_monthly
      FROM memberships m
      JOIN tariffs t ON m.tariff_id = t.id
      WHERE m.status = 'active'
        AND m.effective_end BETWEEN CURDATE() AND DATE_ADD(CURDATE(), INTERVAL 3 MONTH)
      ORDER BY m.effective_end ASC
    `);

    // Alle Mitglieder für Dropdowns
    const [members] = await db.query(`
      SELECT m.id, m.first_name, m.last_name
      FROM memberships m WHERE m.status IN ('active','paused','inactive')
      ORDER BY m.last_name ASC
    `);

    // Offene Rechnungen für Dropdown
    const [openInvoicesDropdown] = await db.query(`
      SELECT i.id, i.period, i.amount, m.first_name, m.last_name
      FROM invoices i JOIN memberships m ON i.membership_id = m.id
      WHERE i.status = 'open'
      ORDER BY i.period DESC, m.last_name ASC
    `);

    res.render('admin/finance', {
      admin: req.session.adminUser,
      dunningFee,
      totalRevenue: totalRevenue[0],
      monthlyRevenue: monthlyRevenue.reverse(), // aufsteigend für Chart
      openInvoices,
      chargebacks,
      dunnings,
      dunningStats: dunningStats[0],
      chargebackStats: chargebackStats[0],
      expiringContracts,
      members,
      openInvoicesDropdown,
      success: req.query.success || null,
      error: req.query.error || null
    });
  } catch (err) {
    console.error(err);
    res.redirect('/admin?error=Fehler+in+der+Finanzübersicht:+' + encodeURIComponent(err.message));
  }
});

// ============================================
// Einstellungen speichern
// ============================================
router.post('/settings', requireAdmin, async (req, res) => {
  const { dunning_fee } = req.body;
  try {
    await db.query(
      "INSERT INTO settings (key_name, value, label) VALUES ('dunning_fee', ?, 'Mahngebühr (€)') ON DUPLICATE KEY UPDATE value = ?",
      [dunning_fee, dunning_fee]
    );
    res.redirect('/admin/finance?success=Einstellungen+gespeichert');
  } catch (err) {
    res.redirect('/admin/finance?error=Fehler+beim+Speichern');
  }
});

// ============================================
// Rückläufer eintragen
// ============================================
router.post('/chargebacks/add', requireAdmin, async (req, res) => {
  const { membership_id, invoice_id, period, amount, reason, chargeback_date, notes } = req.body;
  try {
    await db.query(
      'INSERT INTO chargebacks (membership_id, invoice_id, period, amount, reason, chargeback_date, notes) VALUES (?,?,?,?,?,?,?)',
      [membership_id, invoice_id || null, period, amount, reason || 'SEPA Rücklastschrift', chargeback_date, notes || null]
    );
    // Rechnung wieder auf offen setzen
    if (invoice_id) {
      await db.query("UPDATE invoices SET status='open', paid_at=NULL WHERE id=?", [invoice_id]);
    }
    res.redirect('/admin/finance?success=Rückläufer+eingetragen');
  } catch (err) {
    console.error(err);
    res.redirect('/admin/finance?error=Fehler+beim+Eintragen');
  }
});

router.post('/chargebacks/:id/resolve', requireAdmin, async (req, res) => {
  try {
    await db.query("UPDATE chargebacks SET status='resolved' WHERE id=?", [req.params.id]);
    res.redirect('/admin/finance?success=Rückläufer+als+erledigt+markiert');
  } catch (err) {
    res.redirect('/admin/finance?error=Fehler');
  }
});

// CSV Import Rückläufer
router.post('/chargebacks/import', requireAdmin, async (req, res) => {
  const { csv_data } = req.body;
  if (!csv_data || !csv_data.trim()) return res.redirect('/admin/finance?error=Keine+Daten+eingegeben');
  try {
    const lines = csv_data.trim().split('\n').filter(l => l.trim());
    let imported = 0;
    for (const line of lines) {
      const cols = line.split(';').map(c => c.trim().replace(/"/g, ''));
      if (cols.length < 3) continue;
      const [iban, amount, date, reason] = cols;
      const cleanIban = iban.replace(/\s/g, '');
      // Mitglied anhand IBAN suchen
      const [members] = await db.query(
        "SELECT id FROM memberships WHERE REPLACE(iban,' ','') = ?", [cleanIban]
      );
      if (members.length === 0) continue;
      const now = new Date();
      const period = `${now.getFullYear()}-${String(now.getMonth()+1).padStart(2,'0')}`;
      await db.query(
        'INSERT INTO chargebacks (membership_id, period, amount, reason, chargeback_date) VALUES (?,?,?,?,?)',
        [members[0].id, period, Math.abs(parseFloat(amount.replace(',','.'))), reason || 'SEPA Rücklastschrift', date || new Date().toISOString().split('T')[0]]
      );
      imported++;
    }
    res.redirect(`/admin/finance?success=${imported}+Rückläufer+importiert`);
  } catch (err) {
    console.error(err);
    res.redirect('/admin/finance?error=Import+Fehler:+' + encodeURIComponent(err.message));
  }
});

// ============================================
// Mahngebühren
// ============================================
router.post('/dunning/add', requireAdmin, async (req, res) => {
  const { membership_id, invoice_id, amount, reason, issued_date, notes } = req.body;
  try {
    await db.query(
      'INSERT INTO dunning_fees (membership_id, invoice_id, amount, reason, issued_date, notes) VALUES (?,?,?,?,?,?)',
      [membership_id, invoice_id || null, amount, reason || 'Mahngebühr', issued_date, notes || null]
    );
    res.redirect('/admin/finance?success=Mahngebühr+eingetragen');
  } catch (err) {
    res.redirect('/admin/finance?error=Fehler+beim+Eintragen');
  }
});

router.post('/dunning/:id/paid', requireAdmin, async (req, res) => {
  try {
    await db.query("UPDATE dunning_fees SET status='paid', paid_at=NOW() WHERE id=?", [req.params.id]);
    res.redirect('/admin/finance?success=Mahngebühr+als+bezahlt+markiert');
  } catch (err) {
    res.redirect('/admin/finance?error=Fehler');
  }
});

router.post('/dunning/:id/cancel', requireAdmin, async (req, res) => {
  try {
    await db.query("UPDATE dunning_fees SET status='cancelled' WHERE id=?", [req.params.id]);
    res.redirect('/admin/finance?success=Mahngebühr+storniert');
  } catch (err) {
    res.redirect('/admin/finance?error=Fehler');
  }
});

module.exports = router;