import { NextRequest, NextResponse } from "next/server";
import { z } from "zod";
import { requireSession } from "@/lib/api-auth";
import { applyRateLimit } from "@/lib/rate-limit";

const Schema = z.object({
  barcode: z.string().trim().min(4).max(32).regex(/^[0-9]+$/, "Barcode must be numeric"),
});

type OffProduct = {
  product_name?: string;
  product_name_en?: string;
  generic_name?: string;
  quantity?: string;
  product_quantity?: string;
  product_quantity_unit?: string;
  brands?: string;
};

type OffResponse = {
  status: number;
  product?: OffProduct;
};

/** Very rough unit guess from Open Food Facts' free-text `quantity` field (e.g. "500 g", "1 L"). */
function extractUnit(quantity: string | undefined): string | undefined {
  if (!quantity) return undefined;
  const match = /([a-zA-Z]+)\s*$/.exec(quantity.trim());
  return match?.[1]?.toLowerCase();
}

export async function POST(req: NextRequest) {
  const { session, response } = await requireSession();
  if (response) return response;

  const body = await req.json() as unknown;
  const parsed = Schema.safeParse(body);
  if (!parsed.success) return NextResponse.json({ error: "Validation error" }, { status: 400 });

  const limited = await applyRateLimit(`rl:pantry-scan-barcode:${session!.user.id}`, 20, 60);
  if (limited) return limited;

  const { barcode } = parsed.data;

  let offResponse: Response;
  try {
    offResponse = await fetch(
      `https://world.openfoodfacts.org/api/v2/product/${encodeURIComponent(barcode)}.json`,
      {
        headers: { "User-Agent": "Epicure/1.0 (pantry-scan)" },
        signal: AbortSignal.timeout(8000),
      }
    );
  } catch {
    return NextResponse.json({ error: "Barcode lookup service unavailable" }, { status: 502 });
  }

  if (!offResponse.ok) {
    return NextResponse.json({ error: "Barcode lookup service unavailable" }, { status: 502 });
  }

  const data = await offResponse.json() as OffResponse;

  if (data.status !== 1 || !data.product) {
    return NextResponse.json({ found: false });
  }

  const product = data.product;
  const rawName = product.product_name_en?.trim() || product.product_name?.trim() || product.generic_name?.trim();

  if (!rawName) {
    return NextResponse.json({ found: false });
  }

  return NextResponse.json({
    found: true,
    rawName: product.brands ? `${rawName} (${product.brands.split(",")[0]?.trim()})` : rawName,
    quantity: product.product_quantity,
    unit: extractUnit(product.product_quantity_unit) ?? extractUnit(product.quantity),
  });
}