import express from 'express';
import { stripe, webhookSecret } from '../config/stripe.js';
import { Order } from '../models/Order.js';
import { createWrenOffsetOrder } from '../utils/wrenClient.js';

const router = express.Router();

/**
 * POST /api/webhooks/stripe
 * Handle Stripe webhook events
 *
 * IMPORTANT: This endpoint requires raw body, not JSON parsed
 */
router.post('/stripe', express.raw({ type: 'application/json' }), async (req, res) => {
  const sig = req.headers['stripe-signature'];

  let event;

  try {
    // Verify webhook signature
    event = stripe.webhooks.constructEvent(req.body, sig, webhookSecret);
  } catch (err) {
    console.error('❌ Webhook signature verification failed:', err.message);
    return res.status(400).send(`Webhook Error: ${err.message}`);
  }

  console.log(`📬 Received webhook: ${event.type}`);

  // Handle different event types
  switch (event.type) {
    case 'checkout.session.completed':
      await handleCheckoutSessionCompleted(event.data.object);
      break;

    case 'checkout.session.async_payment_succeeded':
      await handleAsyncPaymentSucceeded(event.data.object);
      break;

    case 'checkout.session.async_payment_failed':
      await handleAsyncPaymentFailed(event.data.object);
      break;

    case 'checkout.session.expired':
      await handleCheckoutSessionExpired(event.data.object);
      break;

    default:
      console.log(`ℹ️  Unhandled event type: ${event.type}`);
  }

  // Return 200 to acknowledge receipt
  res.json({ received: true });
});

/**
 * Handle checkout.session.completed event
 * This fires when payment succeeds (or session completes for delayed payment methods)
 */
async function handleCheckoutSessionCompleted(session) {
  console.log(`✅ Checkout session completed: ${session.id}`);

  try {
    // Find order in database
    const order = Order.findBySessionId(session.id);

    if (!order) {
      console.error(`❌ Order not found for session: ${session.id}`);
      return;
    }

    // 🔒 IDEMPOTENCY CHECK: Prevent duplicate processing
    if (order.status === 'fulfilled' || order.wren_order_id) {
      console.log(`⚠️  Order ${order.id} already fulfilled (status: ${order.status}), skipping duplicate webhook`);
      return;
    }

    if (order.status === 'paid') {
      console.log(`⚠️  Order ${order.id} already marked as paid, skipping payment update`);
      // Still attempt fulfillment if not fulfilled yet
      await fulfillOrder(order, session);
      return;
    }

    // Atomically update payment intent and status to prevent race conditions
    if (session.payment_intent) {
      Order.updatePaymentAndStatus(order.id, session.payment_intent, 'paid');
    } else {
      Order.updateStatus(order.id, 'paid');
    }

    console.log(`💳 Payment confirmed for order: ${order.id}`);
    console.log(`   Customer: ${session.customer_details?.email}`);
    console.log(`   Amount: $${(order.total_amount / 100).toFixed(2)}`);

    // Fulfill order via Wren API
    await fulfillOrder(order, session);

  } catch (error) {
    console.error('❌ Error handling checkout session completed:', error);
  }
}

/**
 * Handle async payment succeeded (e.g., ACH, bank transfer)
 */
async function handleAsyncPaymentSucceeded(session) {
  console.log(`✅ Async payment succeeded: ${session.id}`);

  try {
    const order = Order.findBySessionId(session.id);

    if (!order) {
      console.error(`❌ Order not found for session: ${session.id}`);
      return;
    }

    // 🔒 IDEMPOTENCY CHECK: Prevent duplicate processing
    if (order.status === 'fulfilled' || order.wren_order_id) {
      console.log(`⚠️  Order ${order.id} already fulfilled, skipping duplicate webhook`);
      return;
    }

    if (order.status === 'paid') {
      console.log(`⚠️  Order ${order.id} already marked as paid, attempting fulfillment only`);
      await fulfillOrder(order, session);
      return;
    }

    // Update status to paid
    Order.updateStatus(order.id, 'paid');

    // Fulfill order
    await fulfillOrder(order, session);

  } catch (error) {
    console.error('❌ Error handling async payment succeeded:', error);
  }
}

/**
 * Handle async payment failed
 */
async function handleAsyncPaymentFailed(session) {
  console.log(`❌ Async payment failed: ${session.id}`);

  try {
    const order = Order.findBySessionId(session.id);

    if (!order) {
      console.error(`❌ Order not found for session: ${session.id}`);
      return;
    }

    // 🔒 IDEMPOTENCY CHECK: Only update if not already failed
    if (order.status === 'failed') {
      console.log(`⚠️  Order ${order.id} already marked as failed, skipping duplicate webhook`);
      return;
    }

    // Update status to failed
    Order.updateStatus(order.id, 'failed');

    console.log(`💔 Order ${order.id} marked as failed`);

    // TODO: Send notification to customer about failed payment

  } catch (error) {
    console.error('❌ Error handling async payment failed:', error);
  }
}

/**
 * Handle checkout session expired
 * This fires when a session expires (24 hours) without payment
 */
async function handleCheckoutSessionExpired(session) {
  console.log(`⏰ Checkout session expired: ${session.id}`);

  try {
    const order = Order.findBySessionId(session.id);

    if (!order) {
      console.error(`❌ Order not found for session: ${session.id}`);
      return;
    }

    // 🔒 IDEMPOTENCY CHECK: Only update if still pending
    if (order.status !== 'pending') {
      console.log(`⚠️  Order ${order.id} already processed (status: ${order.status}), skipping expiration`);
      return;
    }

    // Update status to expired
    Order.updateStatus(order.id, 'expired');

    console.log(`🕐 Order ${order.id} marked as expired (abandoned cart)`);
    console.log(`   Session was created but never completed`);

    // TODO: Optional - Send abandoned cart reminder email
    // TODO: Optional - Track abandonment metrics

  } catch (error) {
    console.error('❌ Error handling checkout session expired:', error);
  }
}

/**
 * Fulfill order by creating carbon offset via Wren API
 * @param {Object} order - Database order object
 * @param {Object} session - Stripe session object
 */
async function fulfillOrder(order, session) {
  try {
    // 🔒 IDEMPOTENCY CHECK: Don't fulfill if already fulfilled
    if (order.wren_order_id) {
      console.log(`⚠️  Order ${order.id} already has Wren order ID: ${order.wren_order_id}, skipping fulfillment`);
      return;
    }

    console.log(`🌱 Fulfilling order ${order.id} via Wren API...`);

    // Determine if we should use dry run mode based on environment
    const isDryRun = process.env.WREN_DRY_RUN === 'true';

    if (isDryRun) {
      console.log('⚠️  DRY RUN MODE: No real offset will be created');
    }

    // Create Wren offset order
    const wrenOrder = await createWrenOffsetOrder({
      tons: order.tons,
      portfolioId: order.portfolio_id,
      customerEmail: session.customer_details?.email || order.customer_email,
      dryRun: isDryRun,
    });

    // Update order with Wren order ID
    Order.updateWrenOrder(order.id, wrenOrder.id, 'fulfilled');

    console.log(`✅ Order ${order.id} fulfilled successfully`);
    console.log(`   Wren Order ID: ${wrenOrder.id}`);
    console.log(`   Tons offset: ${order.tons}`);

    // TODO: Send confirmation email to customer

  } catch (error) {
    console.error(`❌ Order fulfillment failed for order ${order.id}:`, error);

    // Mark order as paid but unfulfilled (manual intervention needed)
    Order.updateStatus(order.id, 'paid');

    // TODO: Send alert to admin about failed fulfillment
  }
}

export default router;