// connection_provider.dart — 连接状态机（严格三态，状态由内核事件驱动）
//
// 设计约定：
//   - UI 调用 toggle()，控制器内部读取有效节点 + 认证令牌，调用 ConnectApi
//     并启动 VpnBridge 子进程。
//   - 严禁乐观翻转：VpnPhase.on 必须由 bridge.statusStream 确认后才置。
//   - 状态来源：bridge.statusStream（来自内核回调），非 Timer 模拟。
import 'dart:async';

import 'package:flutter_riverpod/flutter_riverpod.dart';

import '../bridge/vpn_bridge.dart';
import '../bridge/vpn_bridge_provider.dart';
import '../services/connect_api.dart';
import 'auth_provider.dart';
import 'nodes_provider.dart';

// ── 设备 ID（MVP 常量；后续由 device_info_plus 取真实 ID）──────────

const _kDeviceId = String.fromEnvironment(
  'PANGOLIN_DEVICE_ID',
  defaultValue: 'mac-001',
);

// ── API base URL ─────────────────────────────────────────────────

const _kApiUrl = String.fromEnvironment(
  'PANGOLIN_API_URL',
  defaultValue: 'http://localhost:8080',
);

// ── 连接阶段枚举 ──────────────────────────────────────────────────

/// 连接阶段。严格三态，与设计稿一致。
enum VpnPhase { off, connecting, on }

// ── 连接状态快照 ──────────────────────────────────────────────────

class ConnectionState {
  const ConnectionState({required this.phase, this.elapsed = Duration.zero});

  final VpnPhase phase;
  final Duration elapsed;

  ConnectionState copyWith({VpnPhase? phase, Duration? elapsed}) =>
      ConnectionState(phase: phase ?? this.phase, elapsed: elapsed ?? this.elapsed);

  @override
  bool operator ==(Object other) =>
      other is ConnectionState && other.phase == phase && other.elapsed == elapsed;

  @override
  int get hashCode => Object.hash(phase, elapsed);
}

// ── 状态机 ───────────────────────────────────────────────────────

class ConnectionController extends StateNotifier<ConnectionState> {
  ConnectionController(this._ref, this._bridge)
      : super(const ConnectionState(phase: VpnPhase.off)) {
    // 订阅桥状态流：状态由内核事件驱动，严禁 UI 乐观翻转。
    _statusSub = _bridge.statusStream.listen(_onKernelStatus);
  }

  final Ref _ref;
  final VpnBridge _bridge;
  StreamSubscription<VpnStatus>? _statusSub;
  Timer? _elapsed;
  ConnectApi? _api;

  // ── 公有 API ───────────────────────────────────────────────────

  /// 用户点击连接键：按当前状态决定动作，握手中忽略（禁乐观）。
  void toggle() {
    switch (state.phase) {
      case VpnPhase.off:
        _connect();
      case VpnPhase.on:
        _disconnect();
      case VpnPhase.connecting:
        break; // 握手进行中，不响应
    }
  }

  /// 节点切换时触发：已连接则重连。
  void onNodeChanged() {
    if (state.phase == VpnPhase.on || state.phase == VpnPhase.connecting) {
      _disconnect().then((_) => _connect());
    }
  }

  // ── 内部 ─────────────────────────────────────────────────────

  Future<void> _connect() async {
    state = const ConnectionState(phase: VpnPhase.connecting);

    final authState = _ref.read(authProvider);
    final token = authState.accessToken ?? '';
    final node = _ref.read(effectiveNodeProvider);

    // 无 UUID 时（演示节点）直接进入 mock 连接状态
    if (node.uuid.isEmpty) {
      await Future<void>.delayed(const Duration(milliseconds: 1200));
      if (mounted) state = const ConnectionState(phase: VpnPhase.on);
      _startElapsed();
      return;
    }

    try {
      _api?.dispose();
      _api = ConnectApi(baseUrl: _kApiUrl, authToken: token);
      final configJson = await _api!.fetchConfig(
        nodeId: node.uuid,
        deviceId: _kDeviceId,
      );
      // bridge.start() 不阻塞至连接建立；on 状态由 statusStream 回调驱动。
      await _bridge.start(configJson);
    } catch (e) {
      if (mounted) state = const ConnectionState(phase: VpnPhase.off);
    }
  }

  Future<void> _disconnect() async {
    _stopElapsed();
    try {
      await _bridge.stop();
    } catch (_) {}
    if (mounted) state = const ConnectionState(phase: VpnPhase.off);
  }

  void _onKernelStatus(VpnStatus s) {
    if (!mounted) return;
    switch (s) {
      case VpnStatus.on:
        state = state.copyWith(phase: VpnPhase.on);
        _startElapsed();
      case VpnStatus.connecting:
        state = state.copyWith(phase: VpnPhase.connecting);
        _stopElapsed();
      case VpnStatus.off:
      case VpnStatus.error:
        state = const ConnectionState(phase: VpnPhase.off);
        _stopElapsed();
    }
  }

  void _startElapsed() {
    _elapsed?.cancel();
    _elapsed = Timer.periodic(const Duration(seconds: 1), (_) {
      if (mounted && state.phase == VpnPhase.on) {
        state = state.copyWith(elapsed: state.elapsed + const Duration(seconds: 1));
      }
    });
  }

  void _stopElapsed() {
    _elapsed?.cancel();
    _elapsed = null;
  }

  @override
  void dispose() {
    _statusSub?.cancel();
    _stopElapsed();
    _api?.dispose();
    super.dispose();
  }
}

// ── Provider ──────────────────────────────────────────────────────

final connectionProvider =
    StateNotifierProvider<ConnectionController, ConnectionState>(
  (ref) => ConnectionController(ref, ref.watch(vpnBridgeProvider)),
);