import pkg from '../package.json' with { type: 'json' };

/** Where a service whose logs show our traffic can reach us. */
export const DEFAULT_CONTACT = 'https://nibling.dev/contact';

/** The User-Agent every request nibling originates carries, so a service can tell us about runaway traffic. */
export function userAgent(contact: string = DEFAULT_CONTACT): string {
  return `nibling.dev/${pkg.version} (+${contact})`;
}

export const USER_AGENT = userAgent();

/** Browsers own the User-Agent header, and setting it would turn simple requests into preflighted ones. */
export function canSetUserAgent(): boolean {
  const scope = globalThis as { document?: unknown; WorkerGlobalScope?: unknown };
  return scope.document === undefined && scope.WorkerGlobalScope === undefined;
}

/** `headers` with the User-Agent set when this runtime lets us set it. */
export function withUserAgent(headers?: HeadersInit): Headers {
  const out = new Headers(headers);
  if (canSetUserAgent()) out.set('user-agent', USER_AGENT);
  return out;
}