export class BodyTooLargeError extends Error {}

export async function readBodyWithinLimit(
  request: { readonly body: ReadableStream<Uint8Array> | null },
  maxBodyBytes: number,
): Promise<string> {
  if (!request.body) return '';

  const reader = request.body.getReader();
  const decoder = new TextDecoder();
  let bytesRead = 0;
  let text = '';

  try {
    while (true) {
      const { done, value } = await reader.read();
      if (done) return text + decoder.decode();
      bytesRead += value.byteLength;
      if (bytesRead > maxBodyBytes) {
        throw new BodyTooLargeError();
      }
      text += decoder.decode(value, { stream: true });
    }
  } finally {
    reader.releaseLock();
  }
}