import { serve } from 'https://deno.land/std@0.168.0/http/server.ts';
import { createClient } from 'https://esm.sh/@supabase/supabase-js@2';
import Stripe from 'https://esm.sh/stripe@14?target=deno';

const stripe = new Stripe(Deno.env.get('STRIPE_SECRET_KEY')!, { apiVersion: '2023-10-16' });
const webhookSecret = Deno.env.get('STRIPE_WEBHOOK_SECRET')!;

serve(async (req) => {
  const body = await req.text();
  const sig = req.headers.get('stripe-signature');

  let event: Stripe.Event;
  try {
    event = await stripe.webhooks.constructEventAsync(body, sig!, webhookSecret);
  } catch (err) {
    console.error('Webhook signature failed:', err.message);
    return new Response(`Webhook Error: ${err.message}`, { status: 400 });
  }

  const supabase = createClient(
    Deno.env.get('SUPABASE_URL')!,
    Deno.env.get('SUPABASE_SERVICE_ROLE_KEY')!,
  );

  // Helper: retrieve fee from a payment intent and mark invoice paid
  async function markPaid(paymentIntentId: string, invoice_id: string) {
    let stripe_fee: number | null = null;
    try {
      const pi = await stripe.paymentIntents.retrieve(paymentIntentId, {
        expand: ['latest_charge.balance_transaction'],
      });
      const charge = pi.latest_charge as Stripe.Charge | null;
      const balanceTx = charge?.balance_transaction as Stripe.BalanceTransaction | null;
      if (balanceTx?.fee != null) stripe_fee = balanceTx.fee / 100;
    } catch (err) {
      console.error('Failed to retrieve Stripe fee:', err.message);
    }

    const updateData: Record<string, unknown> = {
      status: 'paid',
      paid_at: new Date().toISOString(),
    };
    if (stripe_fee !== null) updateData.stripe_fee = stripe_fee;
    await supabase.from('invoices').update(updateData).eq('id', invoice_id);
  }

  // Card payments: session completes with payment_status = 'paid' immediately
  if (event.type === 'checkout.session.completed') {
    const session = event.data.object as Stripe.Checkout.Session;
    const invoice_id = session.metadata?.invoice_id;
    const paymentIntentId = session.payment_intent as string | null;

    // Only mark paid here for instant payment methods (card).
    // ACH sessions complete with payment_status 'unpaid' — let payment_intent.succeeded handle those.
    if (invoice_id && paymentIntentId && session.payment_status === 'paid') {
      await markPaid(paymentIntentId, invoice_id);
    }
  }

  // ACH / async payment methods: payment_intent.succeeded fires when money actually settles
  if (event.type === 'payment_intent.succeeded') {
    const pi = event.data.object as Stripe.PaymentIntent;
    const invoice_id = pi.metadata?.invoice_id;
    if (invoice_id) {
      await markPaid(pi.id, invoice_id);
    }
  }

  return new Response(JSON.stringify({ received: true }), { status: 200 });
});