const prisma = require('../config/db');
const { generateTicketsForRegistration } = require('../utils/ticketUtils');
const { emailTickets } = require('./ticketController');
const { getProvider } = require('../payments');

const canReconcile = (req) => !!req.user && ['admin', 'supervisor'].includes(req.user.role);
// The checkout metadata (who/what the payment was for), read by the provider that sent it.
const metadataOf = (tx) => {
  const provider = getProvider(tx.provider);
  try { return (provider && tx.raw ? provider.parseWebhook(tx.raw).transaction.metadata : null) || {}; } catch { return {}; }
};
const withLabel = (tx) => ({ ...tx, providerLabel: getProvider(tx.provider)?.label || tx.provider, metadata: metadataOf(tx) });

// @desc    Payment provider transactions (optionally filter by provider, reconciled, ignored)
// @route   GET /api/provider-transactions  (also /api/yoco-transactions)
// @access  Private/Admin or Supervisor
const getAllProviderTransactions = async (req, res) => {
  try {
    if (!canReconcile(req)) return res.status(403).json({ success: false, message: 'Forbidden' });

    const { reconciled, ignored, provider } = req.query;
    const where = {};
    if (typeof reconciled !== 'undefined') where.reconciled = String(reconciled) === 'true';
    if (typeof ignored !== 'undefined') where.ignored = String(ignored) === 'true';
    if (provider) where.provider = String(provider);

    const items = await prisma.providerTransaction.findMany({ where, orderBy: [{ createdDate: 'desc' }, { createdAt: 'desc' }] });
    return res.status(200).json({ success: true, data: items.map(withLabel) });
  } catch (error) {
    console.error('Failed to fetch provider transactions:', error);
    return res.status(500).json({ success: false, message: 'Server error', details: error.message });
  }
};

// @desc    Unreconciled provider transactions (not reconciled and not ignored)
// @route   GET /api/provider-transactions/unreconciled  (also /api/yoco-transactions/unreconciled)
// @access  Private/Admin or Supervisor
const getUnreconciledProviderTransactions = async (req, res) => {
  try {
    if (!canReconcile(req)) return res.status(403).json({ success: false, message: 'Forbidden' });

    const items = await prisma.providerTransaction.findMany({
      where: { reconciled: false, ignored: false, ...(req.query.provider ? { provider: String(req.query.provider) } : {}) },
      orderBy: { createdDate: 'desc' },
    });
    return res.status(200).json({ success: true, data: items.map(withLabel) });
  } catch (error) {
    console.error('Failed to fetch unreconciled provider transactions:', error);
    return res.status(500).json({ success: false, message: 'Server error', details: error.message });
  }
};

// @desc    Reconcile a provider transaction to a Registration or Donation (creates Payment)
// @route   POST /api/provider-transactions/:id/reconcile  (also /api/yoco-transactions/:id/reconcile)
// @access  Private/Admin or Supervisor
const reconcileProviderTransaction = async (req, res) => {
  try {
    if (!canReconcile(req)) return res.status(403).json({ success: false, message: 'Forbidden' });

    const { id } = req.params;
    const { registrationId, eventId, userId: bodyUserId } = req.body || {};

    const tx = await prisma.providerTransaction.findUnique({ where: { id } });
    if (!tx) return res.status(404).json({ success: false, message: 'Transaction not found' });
    if (tx.reconciled && tx.paymentId) {
      return res.status(409).json({ success: false, message: 'Already reconciled', data: withLabel(tx) });
    }

    // Load registration if provided
    let registration = null;
    if (registrationId) {
      registration = await prisma.registration.findUnique({
        where: { id: registrationId },
        include: {
          event: true,
          user: true,
          registrationOptions: { include: { eventOption: true } },
          payments: true
        }
      });
      if (!registration) return res.status(404).json({ success: false, message: 'Registration not found' });
    }

    // Determine payment fields
    const amountFloat = typeof tx.amount === 'number' ? (tx.amount / 100) : 0;
    if (!amountFloat || amountFloat <= 0) {
      return res.status(400).json({ success: false, message: 'Invalid amount on the transaction for reconciliation' });
    }

    const metadata = metadataOf(tx);

    // Resolve a valid userId for the Payment to satisfy FK constraints
    let resolvedUserId = null;
    if (registration?.userId) {
      resolvedUserId = registration.userId;
    } else if (bodyUserId) {
      // Staff explicitly picked the donor while reconciling (e.g. as a donation) — trust that
      // over metadata guesswork, but still verify the user actually exists.
      try {
        const exists = await prisma.user.findUnique({ where: { id: String(bodyUserId) } });
        if (exists) resolvedUserId = String(bodyUserId);
      } catch {}
    }
    if (!resolvedUserId && metadata.userId) {
      try {
        const exists = await prisma.user.findUnique({ where: { id: String(metadata.userId) } });
        if (exists) resolvedUserId = String(metadata.userId);
      } catch {}
    }
    if (!resolvedUserId && req.user?.id) {
      // Fallback to the acting supervisor/admin to avoid FK violations
      resolvedUserId = req.user.id;
    }
    if (!resolvedUserId) {
      return res.status(400).json({ success: false, message: 'Unable to resolve a valid user for this payment' });
    }

    const paymentData = {
      amount: amountFloat,
      method: tx.methodType || 'card',
      provider: tx.provider,
      userId: resolvedUserId,
      recordedById: req.user?.id || null, // staff who performed the reconciliation
      registrationId: registration?.id || null,
      eventId: registration?.eventId || eventId || null,
      isDonation: !registration?.id,
      externalId: tx.externalId || undefined,
      status: 'completed'
    };

    // Ensure donation has an eventId
    if (!registration && !paymentData.eventId) {
      return res.status(400).json({ success: false, message: 'eventId is required when reconciling as donation' });
    }

    // Keep the provider's creation time so early-bird pricing is evaluated correctly
    const createdAt = tx.createdDate || tx.createdAt || new Date();
    const payment = await prisma.payment.create({ data: { ...paymentData, createdAt } });

    // Update registration status and generate tickets if paid. Ticket generation stays
    // synchronous so `generatedTickets` can be in the response; emailing is backgrounded below.
    let generatedTickets = [];
    if (registration) {
      try {
        const updatedReg = await updateRegistrationStatus(registration.id);
        if (updatedReg && updatedReg.status === 'paid') {
          try {
            generatedTickets = await generateTicketsForRegistration(registration.id);
          } catch (genErr) {
            console.error('Error generating tickets after reconciliation:', genErr);
          }
        }
      } catch (e) {
        // log but do not fail reconciliation
        console.warn('Failed to update registration after reconciliation:', e?.message || e);
      }
    }

    // Fire-and-forget: payment confirmation email, then ticket email/WhatsApp (guarantees order)
    const { sendPaymentEmails } = require('../utils/notifications');
    const _rxPaymentId = payment.id;
    const _rxUserId = registration?.userId;
    const _rxRegId = registration?.id;
    const _rxShouldEmailTickets = Array.isArray(generatedTickets) && generatedTickets.length > 0;
    (async () => {
      try { await sendPaymentEmails(_rxPaymentId); } catch (e) { console.error('Failed to send payment emails after reconciliation:', e); }
      if (_rxShouldEmailTickets && _rxUserId) {
        const mockReq = { user: { id: _rxUserId }, body: { registrationId: _rxRegId } };
        const mockRes = { status: () => mockRes, json: () => {} };
        try { await emailTickets(mockReq, mockRes); } catch (e) { console.error('Error emailing tickets after reconciliation:', e); }
      }
    })();

    const updatedTx = await prisma.providerTransaction.update({ where: { id: tx.id }, data: { reconciled: true, paymentId: payment.id } });

    return res.status(200).json({ success: true, data: { transaction: withLabel(updatedTx), payment, generatedTickets: generatedTickets.length ? generatedTickets : undefined } });
  } catch (error) {
    console.error('Failed to reconcile provider transaction:', error);
    // A Payment with the same externalId already exists: link to it instead
    if (error?.code === 'P2002') {
      try {
        const tx = await prisma.providerTransaction.findUnique({ where: { id: req.params.id } });
        const existing = tx ? await prisma.payment.findFirst({ where: { externalId: tx.externalId } }) : null;
        if (existing) {
          const updatedTx = await prisma.providerTransaction.update({ where: { id: tx.id }, data: { reconciled: true, paymentId: existing.id } });
          return res.status(200).json({ success: true, data: { transaction: withLabel(updatedTx), payment: existing }, message: 'Linked to existing payment' });
        }
      } catch {}
    }
    return res.status(500).json({ success: false, message: 'Server error', details: error?.message || String(error) });
  }
};

// Minimal registration status update mirroring webhook logic
async function updateRegistrationStatus(registrationId) {
  const registration = await prisma.registration.findUnique({
    where: { id: registrationId },
    include: {
      registrationOptions: { include: { eventOption: { include: { earlyBirdTiers: true } } } },
      payments: true
    }
  });
  if (!registration) return null;
  const totalPaid = (registration.payments || []).reduce((s, p) => s + (p.amount || 0), 0);
  const totalDue = require('../utils/pricing').computeRegistrationTotalDue(registration, new Date());
  let newStatus = 'pending';
  if (totalPaid >= totalDue) newStatus = 'paid';
  else if (totalPaid > 0) newStatus = 'partial_paid';
  return prisma.registration.update({ where: { id: registrationId }, data: { status: newStatus, updatedAt: new Date() } });
}

// @desc    Ignore a provider transaction (mark as ignored and reconciled without creating a payment)
// @route   POST /api/provider-transactions/:id/ignore  (also /api/yoco-transactions/:id/ignore)
// @access  Private/Admin or Supervisor
const ignoreProviderTransaction = async (req, res) => {
  try {
    if (!canReconcile(req)) return res.status(403).json({ success: false, message: 'Forbidden' });
    const { id } = req.params;
    const tx = await prisma.providerTransaction.findUnique({ where: { id } });
    if (!tx) return res.status(404).json({ success: false, message: 'Transaction not found' });

    if (tx.reconciled && tx.ignored) {
      return res.status(200).json({ success: true, data: withLabel(tx), message: 'Already ignored' });
    }

    const updated = await prisma.providerTransaction.update({ where: { id }, data: { ignored: true, reconciled: true } });
    return res.status(200).json({ success: true, data: withLabel(updated) });
  } catch (error) {
    console.error('Failed to ignore provider transaction:', error);
    return res.status(500).json({ success: false, message: 'Server error', details: error?.message || String(error) });
  }
};

module.exports = {
  getAllProviderTransactions,
  getUnreconciledProviderTransactions,
  reconcileProviderTransaction,
  ignoreProviderTransaction
};