// vpn_bridge_mock.dart — 假内核实现，供 UI 层先行联调
//
// 行为：
//   start()  → 立即 emit connecting，[connectDelay] 后 emit on，启动统计计时器
//   stop()   → 立即 emit off，停止统计计时器
//   stats    → on 状态下按 [statsInterval] 周期推假数据帧
//
// 用法示例（UI 联调）：
//   final bridge = VpnBridgeMock();
//
// 用法示例（测试）：
//   final bridge = VpnBridgeMock(
//     connectDelay:  Duration(milliseconds: 50),
//     statsInterval: Duration(milliseconds: 50),
//   );

import 'dart:async';
import 'dart:math';
import 'vpn_bridge.dart';

class VpnBridgeMock implements VpnBridge {
  VpnBridgeMock({
    this.connectDelay = const Duration(milliseconds: 1500),
    this.statsInterval = const Duration(seconds: 1),
  });

  final Duration connectDelay;
  final Duration statsInterval;

  // 内部状态
  VpnStatus _status = VpnStatus.off;
  String _activeOutbound = 'auto';
  bool _killSwitch = false;

  final _statusCtrl = StreamController<VpnStatus>.broadcast();
  final _statsCtrl = StreamController<VpnStatsEvent>.broadcast();

  Timer? _connectTimer;
  Timer? _statsTimer;

  int _tickCount = 0;
  final _rng = Random();

  // ── helpers ───────────────────────────────────────────────────

  void _emitStatus(VpnStatus s) {
    _status = s;
    if (!_statusCtrl.isClosed) _statusCtrl.add(s);
  }

  void _startStats() {
    _tickCount = 0;
    _statsTimer?.cancel();
    _statsTimer = Timer.periodic(statsInterval, (_) {
      _tickCount++;
      if (!_statsCtrl.isClosed) _statsCtrl.add(_fakeTick(_tickCount));
    });
  }

  VpnStatsEvent _fakeTick(int t) {
    // 模拟稳定带宽 + 微抖动
    final upSpeed = 10240.0 + _rng.nextDouble() * 2048;
    final downSpeed = 51200.0 + _rng.nextDouble() * 8192;
    return VpnStatsEvent(
      uploadBytes: (upSpeed * t * statsInterval.inMilliseconds / 1000).round(),
      downloadBytes: (downSpeed * t * statsInterval.inMilliseconds / 1000).round(),
      uploadSpeed: upSpeed,
      downloadSpeed: downSpeed,
      urltestResults: const [
        UrltestResult(tag: 'hk-01', delayMs: 18),
        UrltestResult(tag: 'jp-01', delayMs: 32),
        UrltestResult(tag: 'sg-01', delayMs: 54),
      ],
    );
  }

  // ── VpnBridge methods ─────────────────────────────────────────

  @override
  Future<void> start(String configJson) async {
    _connectTimer?.cancel();
    _statsTimer?.cancel();
    _emitStatus(VpnStatus.connecting);
    _connectTimer = Timer(connectDelay, () {
      _emitStatus(VpnStatus.on);
      _startStats();
    });
  }

  @override
  Future<void> stop() async {
    _connectTimer?.cancel();
    _statsTimer?.cancel();
    _connectTimer = null;
    _statsTimer = null;
    _emitStatus(VpnStatus.off);
  }

  @override
  Future<VpnStatus> getStatus() async => _status;

  @override
  Future<void> selectOutbound(String tag) async {
    _activeOutbound = tag;
    // 切换出口时模拟短暂重连
    if (_status == VpnStatus.on) {
      _statsTimer?.cancel();
      _emitStatus(VpnStatus.connecting);
      _connectTimer = Timer(connectDelay ~/ 2, () {
        _emitStatus(VpnStatus.on);
        _startStats();
      });
    }
  }

  @override
  Future<String> getActiveOutbound() async => _activeOutbound;

  @override
  Future<void> setKillSwitch({required bool on}) async {
    _killSwitch = on;
  }

  /// 测试可读：mock 记录的 kill-switch 状态。
  bool get killSwitchEnabled => _killSwitch;

  @override
  Stream<VpnStatus> get statusStream => _statusCtrl.stream;

  @override
  Stream<VpnStatsEvent> get statsStream => _statsCtrl.stream;

  @override
  void dispose() {
    _connectTimer?.cancel();
    _statsTimer?.cancel();
    _statusCtrl.close();
    _statsCtrl.close();
  }
}