import type { NextRequest } from "next/server";
import { CONTENT_LIMITS } from "@/lib/validation/contentSchemas";

export class RequestTooLargeError extends Error {}

export async function readLimitedJson(
  request: NextRequest,
  maximumBytes = CONTENT_LIMITS.requestBytes
): Promise<unknown> {
  const declaredLength = Number(request.headers.get("content-length"));
  if (Number.isFinite(declaredLength) && declaredLength > maximumBytes) {
    throw new RequestTooLargeError(`Request body must not exceed ${maximumBytes} bytes`);
  }

  const body = await request.text();
  if (new TextEncoder().encode(body).byteLength > maximumBytes) {
    throw new RequestTooLargeError(`Request body must not exceed ${maximumBytes} bytes`);
  }
  try {
    return JSON.parse(body) as unknown;
  } catch {
    return null;
  }
}