import { NextResponse } from "next/server";
import { and, eq } from "drizzle-orm";
import {
  getMonthlyImageLimitByPlanId,
  isBillingPlanId,
  type BillingPlanId,
} from "@/lib/billing/plans";
import { verifyStripeSignature } from "@/lib/billing/stripe";
import { db } from "@/lib/db";
import { user } from "@/lib/db/schema";

type StripeEvent = {
  id: string;
  type: string;
  data: {
    object: {
      metadata?: Record<string, string>;
      customer_details?: {
        email?: string;
      };
      mode?: string;
      status?: string;
      cancel_at_period_end?: boolean;
    };
  };
};

async function applyPlanToUser({
  userId,
  email,
  planId,
}: {
  userId?: string;
  email?: string;
  planId: BillingPlanId;
}) {
  const monthlyImageLimit = getMonthlyImageLimitByPlanId(planId);
  const updateData = {
    monthlyImageLimit,
    updatedAt: new Date(),
  };

  if (userId) {
    await db.update(user).set(updateData).where(eq(user.id, userId));
    return;
  }

  if (email) {
    await db
      .update(user)
      .set(updateData)
      .where(and(eq(user.email, email), eq(user.isActive, true)));
  }
}

function extractUserRef(object: StripeEvent["data"]["object"]) {
  return {
    userId: object.metadata?.userId,
    email: object.customer_details?.email,
  };
}

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

  if (!webhookSecret) {
    return NextResponse.json({ error: "Webhook secret is not configured" }, { status: 503 });
  }

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

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

  const verified = verifyStripeSignature({
    payload: rawPayload,
    signatureHeader: signature,
    webhookSecret,
  });

  if (!verified) {
    return NextResponse.json({ error: "Invalid webhook signature" }, { status: 400 });
  }

  try {
    const event = JSON.parse(rawPayload) as StripeEvent;
    const object = event.data.object;
    const userRef = extractUserRef(object);

    if (event.type === "checkout.session.completed") {
      if (object.mode !== "subscription") {
        return NextResponse.json({ received: true });
      }

      const planId = object.metadata?.planId;

      if (planId && isBillingPlanId(planId)) {
        await applyPlanToUser({ ...userRef, planId });
      }

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

    if (event.type === "customer.subscription.updated") {
      const planId = object.metadata?.planId;

      if (planId && isBillingPlanId(planId) && object.status === "active") {
        await applyPlanToUser({ ...userRef, planId });
      }

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

    if (event.type === "customer.subscription.deleted") {
      await applyPlanToUser({ ...userRef, planId: "starter" });
      return NextResponse.json({ received: true });
    }

    return NextResponse.json({ received: true });
  } catch (error) {
    console.error("[Billing Stripe Webhook] Error:", error);
    return NextResponse.json({ error: "Webhook processing failed" }, { status: 500 });
  }
}