const kBrowserUserAgent =
    'Mozilla/5.0 (Linux; Android 14; Pixel 8 Pro) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Mobile Safari/537.36';

const kDesktopUserAgent =
    'Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36';

Map<String, String> browserHeaders({
  String? origin,
  String? referer,
  String? accept,
  String? contentType,
  bool desktop = false,
  Map<String, String>? extra,
}) {
  return {
    'User-Agent': desktop ? kDesktopUserAgent : kBrowserUserAgent,
    'Accept': accept ?? '*/*',
    'Accept-Language': 'en-US,en;q=0.9',
    if (origin != null) 'Origin': origin,
    if (referer != null) 'Referer': referer,
    if (contentType != null) 'Content-Type': contentType,
    ...?extra,
  };
}

/// True when a provider dumped an error page / WAF / paywall instead of model text.
bool looksLikeGarbage(String text) {
  final t = text.trimLeft();
  if (t.isEmpty) return true;
  final lower = t.toLowerCase();
  if (t.startsWith('<!DOCTYPE') || t.startsWith('<html') || t.startsWith('<HTML')) {
    return true;
  }
  if (lower.contains('just a moment') ||
      lower.contains('cf-browser-verification') ||
      lower.contains('attention required') ||
      lower.contains('payment required') ||
      lower.contains('frontend_captcha') ||
      lower.contains('err_challenge') ||
      lower.contains('error code:') ||
      lower.contains('missing api key') ||
      lower.contains('invalid api key') ||
      lower.contains('you have to be logged in') ||
      lower.contains('no cake credits') ||
      lower.contains('insufficient_credits')) {
    return true;
  }
  return false;
}

bool looksLikeModelOutput(String text) {
  final trimmed = text.trim();
  if (trimmed.length < 8) return false;
  final lower = trimmed.toLowerCase();
  if (lower == ': ping' || lower == 'ping' || lower == 'pong' || lower == '{}') {
    return false;
  }
  if (RegExp(r'^[\{\}\[\]":\s]+$').hasMatch(trimmed)) return false;
  return !looksLikeGarbage(trimmed);
}

String? cookieHeaderFromSetCookie(String? setCookie, {String? name}) {
  if (setCookie == null || setCookie.isEmpty) return null;
  // http package may join multiple Set-Cookie values with ", ".
  final parts = setCookie.split(RegExp(r',(?=\s*[^;=]+=)'));
  final pairs = <String>[];
  for (final part in parts) {
    final nv = part.split(';').first.trim();
    if (nv.isEmpty || !nv.contains('=')) continue;
    if (name != null && !nv.startsWith('$name=')) continue;
    pairs.add(nv);
  }
  if (pairs.isEmpty) return null;
  return pairs.join('; ');
}