/// In-process cookie jar. Python g4f keeps a curl_cffi session; Dart/Cronet
/// does not, so every provider must share cookies across GET-then-POST.
class G4fCookieJar {
  final Map<String, _StoredCookie> _cookies = {};

  int get length => _cookies.length;

  void clear() => _cookies.clear();

  void set({
    required String name,
    required String value,
    required String domain,
    String path = '/',
    DateTime? expires,
    bool secure = false,
    bool hostOnly = true,
  }) {
    if (name.isEmpty) return;
    final canon = _canonDomain(domain);
    if (canon.isEmpty) return;
    final key = _key(canon, path, name);
    if (value.isEmpty && expires != null) {
      _cookies.remove(key);
      return;
    }
    _cookies[key] = _StoredCookie(
      name: name,
      value: value,
      domain: canon,
      path: path.isEmpty ? '/' : path,
      expires: expires,
      secure: secure,
      hostOnly: hostOnly,
    );
  }

  /// Parse `Set-Cookie` from an HTTP response for [uri].
  void absorb(Uri uri, Map<String, String> headers) {
    final raw = headers['set-cookie'];
    if (raw == null || raw.isEmpty) return;
    for (final part in splitSetCookieHeader(raw)) {
      final parsed = _parseSetCookie(part, uri);
      if (parsed == null) continue;
      if (parsed.expired) {
        _cookies.remove(_key(parsed.domain, parsed.path, parsed.name));
        continue;
      }
      _cookies[_key(parsed.domain, parsed.path, parsed.name)] = parsed;
    }
  }

  String headerFor(Uri uri) {
    final now = DateTime.now().toUtc();
    final matching = <_StoredCookie>[];
    final stale = <String>[];
    _cookies.forEach((key, cookie) {
      if (cookie.expires != null && !cookie.expires!.isAfter(now)) {
        stale.add(key);
        return;
      }
      if (cookie.matches(uri)) matching.add(cookie);
    });
    for (final key in stale) {
      _cookies.remove(key);
    }
    matching.sort((a, b) => b.path.length.compareTo(a.path.length));
    return matching.map((c) => '${c.name}=${c.value}').join('; ');
  }

  /// Test helper.
  Map<String, String> asMapFor(Uri uri) {
    final header = headerFor(uri);
    if (header.isEmpty) return {};
    final out = <String, String>{};
    for (final part in header.split('; ')) {
      final eq = part.indexOf('=');
      if (eq <= 0) continue;
      out[part.substring(0, eq)] = part.substring(eq + 1);
    }
    return out;
  }
}

class _StoredCookie {
  _StoredCookie({
    required this.name,
    required this.value,
    required this.domain,
    required this.path,
    required this.secure,
    required this.hostOnly,
    this.expires,
  });

  final String name;
  final String value;
  final String domain;
  final String path;
  final DateTime? expires;
  final bool secure;
  final bool hostOnly;

  bool get expired {
    if (expires == null) return false;
    return !expires!.isAfter(DateTime.now().toUtc());
  }

  bool matches(Uri uri) {
    if (secure && uri.scheme != 'https') return false;
    final host = uri.host.toLowerCase();
    if (hostOnly) {
      if (host != domain) return false;
    } else {
      if (host != domain && !host.endsWith('.$domain')) return false;
    }
    final reqPath = uri.path.isEmpty ? '/' : uri.path;
    if (path == '/') return true;
    if (reqPath == path) return true;
    if (reqPath.startsWith(path.endsWith('/') ? path : '$path/')) return true;
    return false;
  }
}

String _canonDomain(String domain) {
  var d = domain.trim().toLowerCase();
  if (d.startsWith('.')) d = d.substring(1);
  return d;
}

String _key(String domain, String path, String name) =>
    '${_canonDomain(domain)}|$path|$name';

/// Split a folded Set-Cookie header (commas inside Expires dates).
List<String> splitSetCookieHeader(String header) {
  return header
      .split(RegExp(r',(?=\s*[^;=]+=)'))
      .map((s) => s.trim())
      .where((s) => s.isNotEmpty)
      .toList();
}

_StoredCookie? _parseSetCookie(String raw, Uri uri) {
  final parts = raw.split(';');
  if (parts.isEmpty) return null;
  final nv = parts.first.trim();
  final eq = nv.indexOf('=');
  if (eq <= 0) return null;
  final name = nv.substring(0, eq).trim();
  final value = nv.substring(eq + 1).trim();
  if (name.isEmpty) return null;

  String? domain;
  var path = '/';
  DateTime? expires;
  var secure = false;
  var hostOnly = true;

  for (var i = 1; i < parts.length; i++) {
    final attr = parts[i].trim();
    if (attr.isEmpty) continue;
    final aEq = attr.indexOf('=');
    final key = (aEq < 0 ? attr : attr.substring(0, aEq)).trim().toLowerCase();
    final val = aEq < 0 ? '' : attr.substring(aEq + 1).trim();
    if (key == 'domain' && val.isNotEmpty) {
      domain = _canonDomain(val);
      hostOnly = false;
    } else if (key == 'path' && val.isNotEmpty) {
      path = val;
    } else if (key == 'expires') {
      expires ??= DateTime.tryParse(val)?.toUtc();
    } else if (key == 'max-age') {
      final secs = int.tryParse(val);
      if (secs != null) {
        expires = DateTime.now().toUtc().add(Duration(seconds: secs));
      }
    } else if (key == 'secure') {
      secure = true;
    }
  }

  return _StoredCookie(
    name: name,
    value: value,
    domain: domain ?? uri.host.toLowerCase(),
    path: path,
    expires: expires,
    secure: secure,
    hostOnly: domain == null ? true : hostOnly,
  );
}