import { NextResponse } from "next/server";
import { addToCart } from "@/lib/medusa";
import { parseBody, isNonEmptyString, isPositiveInt, isValidMedusaId, badRequest, checkCsrf } from "@/lib/apiUtils";

// POST /api/cart/[cartId]/items — add a line item
export async function POST(
  request: Request,
  { params }: { params: Promise<{ cartId: string }> },
) {
  const csrfError = await checkCsrf();
  if (csrfError) return csrfError;

  const { cartId } = await params;
  if (!isValidMedusaId(cartId)) {
    return badRequest("Invalid cart ID format");
  }

  const body = await parseBody<{ variant_id?: unknown; quantity?: unknown }>(request);
  if (!body) return badRequest("Invalid request body");

  const { variant_id, quantity } = body;

  if (!isNonEmptyString(variant_id)) {
    return badRequest("Missing or invalid variant_id");
  }
  if (!isValidMedusaId(variant_id)) {
    return badRequest("Invalid variant ID format");
  }

  const qty = quantity ?? 1;
  if (!isPositiveInt(qty)) {
    return badRequest("Quantity must be a positive integer");
  }

  try {
    const cart = await addToCart(cartId, variant_id, qty);
    return NextResponse.json(cart);
  } catch (e) {
    console.error("[cart:add]", (e as Error).message);
    return NextResponse.json({ error: "Failed to add item to cart" }, { status: 500 });
  }
}