export async function readBytes(
  chunks: AsyncIterable<Uint8Array> | Iterable<Uint8Array>,
  maxBytes: number,
): Promise<Uint8Array> {
  const parts: Uint8Array[] = [];
  let size = 0;
  for await (const chunk of chunks) {
    size += chunk.byteLength;
    if (size > maxBytes) throw new Error("Body too large");
    parts.push(chunk);
  }
  const bytes = new Uint8Array(size);
  let offset = 0;
  for (const part of parts) {
    bytes.set(part, offset);
    offset += part.byteLength;
  }
  return bytes;
}

export const cookie = (
  name: string,
  value: string,
  secure: boolean,
  maxAge: number,
) =>
  `${name}=${value}; Path=/; HttpOnly; SameSite=Lax; Max-Age=${maxAge}${
    secure ? "; Secure" : ""
  }`;

export const readCookie = (req: Request, name: string) =>
  new RegExp(`(?:^|;\\s*)${name}=([^;]*)`)
    .exec(req.headers.get("cookie") ?? "")?.[1];

// An origin with nothing else: no credentials, path, query, or fragment.
export const isBareOrigin = (url: URL) =>
  ["https:", "http:"].includes(url.protocol) && !url.username &&
  !url.password && url.pathname === "/" && !url.search && !url.hash;

export class HttpError extends Error {
  constructor(
    readonly status: number,
    message: string,
    readonly headers: HeadersInit = {},
  ) {
    super(message);
  }

  response(): Response {
    return new Response(this.message, {
      status: this.status,
      headers: this.headers,
    });
  }
}

export function fail(status: number, message: string): never {
  throw new HttpError(status, message);
}

export const redirect = (path: string, ...cookies: string[]): Response => {
  const res = new Response(null, { status: 303, headers: { location: path } });
  for (const value of cookies) res.headers.append("set-cookie", value);
  return res;
};