/**
 * Every knob is an environment variable with a working default, so the
 * container runs correctly with no configuration at all.
 */

function int(name: string, fallback: number): number {
  const raw = process.env[name];
  if (raw === undefined || raw === '') return fallback;
  const parsed = Number.parseInt(raw, 10);
  if (!Number.isFinite(parsed)) {
    throw new Error(`${name} must be an integer, got ${JSON.stringify(raw)}`);
  }
  return parsed;
}

function str(name: string, fallback: string): string {
  const raw = process.env[name];
  return raw === undefined || raw === '' ? fallback : raw;
}

export const config = {
  host: str('HOST', '0.0.0.0'),
  port: int('PORT', 8080),
  logLevel: str('LOG_LEVEL', 'info'),

  /** Where the persistent Chromium profile lives. Survives restarts so that
   *  cookies and dismissed consent banners accumulate the way a real
   *  browser's do. */
  profileDir: str('PROFILE_DIR', './profile'),

  /** Concurrent page loads. Chromium is the memory ceiling on this box, so
   *  requests queue rather than opening an unbounded number of tabs. */
  maxConcurrent: int('MAX_CONCURRENT', 2),

  /** Budget for a single navigation, and for a whole resolve including
   *  extraction. */
  navigationTimeoutMs: int('NAVIGATION_TIMEOUT_MS', 20_000),
  resolveTimeoutMs: int('RESOLVE_TIMEOUT_MS', 30_000),

  /** Resolved posts are cached in memory only. Reloading or hitting back
   *  must not drive Chromium again. */
  cacheTtlMs: int('CACHE_TTL_MS', 60 * 60 * 1000),
  cacheMax: int('CACHE_MAX', 200),

  /** How long a signed /m/ media token stays valid. Long enough to finish
   *  watching a video, short enough that a leaked URL goes stale. */
  mediaTokenTtlMs: int('MEDIA_TOKEN_TTL_MS', 6 * 60 * 60 * 1000),

  /** Where this instance is reachable. Only used to print the rewrite rules
   *  on the index page with the right hostname in them. */
  publicOrigin: str('PUBLIC_ORIGIN', 'http://localhost:8080'),
} as const;

export type Config = typeof config;