interface ReadableResponse {
  headers: { get: (name: string) => string | null };
  body: {
    getReader: () => {
      read: () => Promise<{ done: boolean; value?: Uint8Array }>;
      cancel: () => Promise<void>;
    };
  } | null;
}

export async function readBoundedJsonResponseAsync(
  response: ReadableResponse,
  maxBytes: number,
  label = "Response",
): Promise<unknown> {
  const declaredLength = Number(response.headers.get("content-length"));
  if (Number.isFinite(declaredLength) && declaredLength > maxBytes) {
    throw new Error(`${label} exceeds ${maxBytes} bytes`);
  }

  if (!response.body) return null;

  const reader = response.body.getReader();
  const chunks: Uint8Array[] = [];
  let byteLength = 0;
  for (;;) {
    const { done, value } = await reader.read();
    if (done) break;
    if (!value) continue;
    byteLength += value.byteLength;
    if (byteLength > maxBytes) {
      await reader.cancel();
      throw new Error(`${label} exceeds ${maxBytes} bytes`);
    }
    chunks.push(value);
  }

  const body = new Uint8Array(byteLength);
  let offset = 0;
  for (const chunk of chunks) {
    body.set(chunk, offset);
    offset += chunk.byteLength;
  }
  return JSON.parse(new TextDecoder().decode(body)) as unknown;
}