import { NextResponse } from "next/server";
import type Stripe from "stripe";

import { isPaidPlanId, type PlanId } from "@/lib/plans";
import { getStripe } from "@/lib/stripe";
import { createAdminClient } from "@/lib/supabase/admin";

export const runtime = "nodejs";

function resolvePlanId(metadata: Stripe.Metadata | null): PlanId | null {
  const planId = metadata?.planId;
  if (planId && isPaidPlanId(planId)) {
    return planId;
  }
  return null;
}

async function upsertProfileFromSession(session: Stripe.Checkout.Session) {
  const userId = session.client_reference_id ?? session.metadata?.userId;

  if (!userId) {
    return;
  }

  const plan = resolvePlanId(session.metadata);
  if (!plan) {
    return;
  }

  const admin = createAdminClient();

  const { error } = await admin.from("profiles").upsert(
    {
      id: userId,
      email: session.customer_email ?? session.customer_details?.email ?? null,
      plan,
      billing_period: session.metadata?.billingPeriod ?? null,
      stripe_customer_id:
        typeof session.customer === "string" ? session.customer : null,
      stripe_subscription_id:
        typeof session.subscription === "string"
          ? session.subscription
          : null,
      updated_at: new Date().toISOString(),
    },
    { onConflict: "id" }
  );

  if (error) {
    throw new Error(`Failed to update profile: ${error.message}`);
  }
}

export async function POST(request: Request) {
  const webhookSecret = process.env.STRIPE_WEBHOOK_SECRET;

  if (!webhookSecret) {
    return NextResponse.json(
      { error: "Webhook secret not configured." },
      { status: 500 }
    );
  }

  const signature = request.headers.get("stripe-signature");

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

  const body = await request.text();
  const stripe = getStripe();

  let event: Stripe.Event;

  try {
    event = stripe.webhooks.constructEvent(body, signature, webhookSecret);
  } catch (error) {
    const message =
      error instanceof Error ? error.message : "Webhook signature verification failed.";
    return NextResponse.json({ error: message }, { status: 400 });
  }

  try {
    switch (event.type) {
      case "checkout.session.completed": {
        const session = event.data.object as Stripe.Checkout.Session;
        if (session.mode === "subscription") {
          await upsertProfileFromSession(session);
        }
        break;
      }
      case "customer.subscription.deleted": {
        const subscription = event.data.object as Stripe.Subscription;
        const userId = subscription.metadata?.userId;

        if (userId) {
          const admin = createAdminClient();
          await admin
            .from("profiles")
            .update({
              plan: "free",
              billing_period: null,
              stripe_subscription_id: null,
              updated_at: new Date().toISOString(),
            })
            .eq("id", userId);
        }
        break;
      }
      default:
        break;
    }
  } catch (error) {
    const message =
      error instanceof Error ? error.message : "Webhook handler failed.";
    return NextResponse.json({ error: message }, { status: 500 });
  }

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