import { NextRequest, NextResponse } from "next/server";
import { activateProPlan } from "@/lib/billing";
import { PRO_PRICE_CENTS } from "@/lib/credits";
import { prisma } from "@/lib/db";
import { getSessionUser } from "@/lib/session";
import {
  checkoutTaxAndReferenceOptions,
  ensureStripeCustomer,
  priceDataTaxFields,
  productDataWithTaxCode,
} from "@/lib/stripe-checkout";
import { getStripe, isBillingDevMock, isStripeConfigured } from "@/lib/stripe";

/** Start Pro subscription Checkout (€5/mo) or mock-upgrade in development. */
export async function POST(req: NextRequest) {
  const user = await getSessionUser();
  if (!user) {
    return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
  }

  if (user.plan === "PREMIUM") {
    return NextResponse.json({ error: "Already on Pro." }, { status: 400 });
  }

  const dbUser = await prisma.user.findUniqueOrThrow({
    where: { id: user.id },
    select: { email: true, stripeCustomerId: true },
  });

  if (isBillingDevMock()) {
    await activateProPlan(user.id, {
      stripeCustomerId: dbUser.stripeCustomerId,
      stripeSubscriptionId: `dev_sub_${Date.now()}`,
      cardLast4: "4242",
    });
    return NextResponse.json({ mocked: true, plan: "PREMIUM" });
  }

  if (!isStripeConfigured()) {
    return NextResponse.json(
      { error: "Payments are not configured yet. Set STRIPE_SECRET_KEY." },
      { status: 503 },
    );
  }

  const origin = process.env.NEXTAUTH_URL || req.nextUrl.origin;
  const stripe = getStripe();
  const customerId = await ensureStripeCustomer(user.id, dbUser.email);
  const priceId = process.env.STRIPE_PRO_PRICE_ID;

  const session = await stripe.checkout.sessions.create({
    mode: "subscription",
    customer: customerId,
    line_items: priceId
      ? [{ price: priceId, quantity: 1 }]
      : [
          {
            quantity: 1,
            price_data: {
              currency: "eur",
              unit_amount: PRO_PRICE_CENTS,
              recurring: { interval: "month" },
              ...priceDataTaxFields(),
              product_data: productDataWithTaxCode(
                "Songs2VID Pro",
                "50 video credits / month · 1080p · API access · Includes Custom Branding, Watermark Positioning, and Bulk Image Matching",
              ),
            },
          },
        ],
    metadata: {
      type: "pro_subscription",
      userId: user.id,
    },
    subscription_data: {
      metadata: {
        type: "pro_subscription",
        userId: user.id,
      },
    },
    ...checkoutTaxAndReferenceOptions(user.id),
    success_url: `${origin}/dashboard/settings?upgrade=success`,
    cancel_url: `${origin}/dashboard/settings?upgrade=cancelled`,
  });

  return NextResponse.json({ url: session.url, sessionId: session.id });
}