export interface ConfiguredTransportUrlOptions {
  allowLoopbackHttp: boolean;
  originOnly?: boolean;
}

export function parseCredentialFreeHttpUrl(value: string): URL | undefined {
  let url: URL;
  try {
    url = new URL(value);
  } catch {
    return undefined;
  }
  if (!["http:", "https:"].includes(url.protocol)
    || url.username || url.password || url.search || url.hash) return undefined;
  return url;
}

function canonicalLoopbackAuthority(value: string): boolean {
  const match = /^http:\/\/([^/?#]+)(?:[/?#]|$)/.exec(value);
  if (!match) return false;
  const authority = match[1];
  let port: string | undefined;
  if (authority.startsWith("[")) {
    const ipv6 = /^(\[::1\])(?::([^:]+))?$/.exec(authority);
    if (!ipv6) return false;
    port = ipv6[2];
  } else {
    const ipv4 = /^([^:]+)(?::([^:]+))?$/.exec(authority);
    if (!ipv4) return false;
    const octets = ipv4[1].split(".");
    if (octets.length !== 4 || octets.some((octet) => !/^(?:0|[1-9]\d{0,2})$/.test(octet)
      || Number(octet) > 255) || Number(octets[0]) !== 127) return false;
    port = ipv4[2];
  }
  return port === undefined || (/^(?:0|[1-9]\d{0,4})$/.test(port) && Number(port) <= 65_535);
}

export function parseConfiguredTransportUrl(
  value: string,
  options: ConfiguredTransportUrlOptions,
): URL | undefined {
  const url = parseCredentialFreeHttpUrl(value);
  if (!url || (options.originOnly && url.pathname !== "/")) return undefined;
  if (url.protocol === "https:") return url;
  if (options.allowLoopbackHttp && url.protocol === "http:" && canonicalLoopbackAuthority(value)) return url;
  return undefined;
}