import { NextRequest, NextResponse } from 'next/server';
import { getStripe } from '@/lib/stripe';
import { getServiceClient } from '@/lib/supabase';
import Stripe from 'stripe';

export async function POST(req: NextRequest) {
  const body = await req.text();
  const signature = req.headers.get('stripe-signature');

  if (!signature) {
    return NextResponse.json(
      { error: 'Missing stripe-signature header' },
      { status: 400 }
    );
  }

  let event: Stripe.Event;

  try {
    event = getStripe().webhooks.constructEvent(
      body,
      signature,
      process.env.STRIPE_WEBHOOK_SECRET!
    );
  } catch (err) {
    const message = err instanceof Error ? err.message : 'Unknown error';
    console.error('Webhook signature verification failed:', message);
    return NextResponse.json(
      { error: `Webhook Error: ${message}` },
      { status: 400 }
    );
  }

  const supabase = getServiceClient();

  try {
    switch (event.type) {
      case 'checkout.session.completed': {
        const session = event.data.object as Stripe.Checkout.Session;
        const applicationId = session.metadata?.application_id;

        if (applicationId) {
          const { error } = await supabase
            .from('applications')
            .update({
              payment_status: 'paid',
              amount_paid: session.amount_total,
              currency: session.currency,
            })
            .eq('id', applicationId);

          if (error) {
            console.error('Failed to update application on payment success:', error);
          }
        }
        break;
      }

      case 'checkout.session.expired': {
        const session = event.data.object as Stripe.Checkout.Session;
        const applicationId = session.metadata?.application_id;

        if (applicationId) {
          const { error } = await supabase
            .from('applications')
            .update({
              payment_status: 'failed',
            })
            .eq('id', applicationId);

          if (error) {
            console.error('Failed to update application on session expiry:', error);
          }
        }
        break;
      }

      default:
        // Unhandled event type - log but don't error
        console.log(`Unhandled event type: ${event.type}`);
    }
  } catch (error) {
    console.error('Webhook handler error:', error);
    return NextResponse.json(
      { error: 'Webhook handler failed' },
      { status: 500 }
    );
  }

  return NextResponse.json({ received: true }, { status: 200 });
}