software copyright
This commit is contained in:
jiahong
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/// 自然写互动课堂手机端应用软件 V1.0
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/// WebSocket实时通信服务 - 接收云端实时推送通知
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///
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/// 功能说明：
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/// 1. WebSocket长连接管理（建立、维持、重连）
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/// 2. 心跳机制（30秒间隔，检测连接存活性）
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/// 3. 消息类型分发（新作业、批改完成、课堂互动、家校消息）
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/// 4. 指数退避重连策略（断线后自动重连，逐步增加间隔）
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/// 5. 消息ACK确认（确保重要消息不丢失）
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/// 6. 离线消息补发（重连后请求离线期间的消息）
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import 'dart:async';
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import 'dart:convert';
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/* ========== 消息类型定义 ========== */
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/// WebSocket消息类型枚举
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enum WsMessageType {
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heartbeat, // 心跳包
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heartbeatAck, // 心跳响应
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newAssignment, // 新作业通知
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gradeComplete, // 批改完成通知
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classroomEvent, // 课堂互动事件（发题/收卷等）
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parentMessage, // 家校沟通消息
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systemNotice, // 系统公告
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strokeRealtime, // 实时笔迹数据（课堂模式）
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offlineSync, // 离线消息同步
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ack, // 消息确认
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}
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/// WebSocket消息模型
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class WsMessage {
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final String id; // 消息唯一ID
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final WsMessageType type; // 消息类型
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final Map<String, dynamic> data; // 消息内容
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final int timestamp; // 服务端时间戳
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final bool requireAck; // 是否需要ACK确认
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WsMessage({
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required this.id,
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required this.type,
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required this.data,
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required this.timestamp,
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this.requireAck = false,
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});
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/// 从JSON反序列化
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factory WsMessage.fromJson(Map<String, dynamic> json) {
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return WsMessage(
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id: json['id'] ?? '',
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type: _parseMessageType(json['type'] ?? ''),
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data: Map<String, dynamic>.from(json['data'] ?? {}),
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timestamp: json['timestamp'] ?? 0,
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requireAck: json['require_ack'] ?? false,
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);
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}
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/// 序列化为JSON
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Map<String, dynamic> toJson() => {
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'id': id,
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'type': type.name,
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'data': data,
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'timestamp': timestamp,
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};
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/// 解析消息类型字符串
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static WsMessageType _parseMessageType(String typeStr) {
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switch (typeStr) {
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case 'heartbeat': return WsMessageType.heartbeat;
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case 'heartbeat_ack': return WsMessageType.heartbeatAck;
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case 'new_assignment': return WsMessageType.newAssignment;
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case 'grade_complete': return WsMessageType.gradeComplete;
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case 'classroom_event': return WsMessageType.classroomEvent;
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case 'parent_message': return WsMessageType.parentMessage;
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case 'system_notice': return WsMessageType.systemNotice;
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case 'stroke_realtime': return WsMessageType.strokeRealtime;
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case 'offline_sync': return WsMessageType.offlineSync;
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case 'ack': return WsMessageType.ack;
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default: return WsMessageType.systemNotice;
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}
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}
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}
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/* ========== WebSocket连接状态 ========== */
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/// 连接状态枚举
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enum WsConnectionState {
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disconnected, // 未连接
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connecting, // 正在连接
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connected, // 已连接
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reconnecting, // 重连中
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}
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/* ========== WebSocket服务实现 ========== */
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/// WebSocket实时通信服务
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/// 维护与云平台的长连接，接收实时推送通知
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class WebSocketService {
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/// WebSocket服务器地址
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static const String _wsUrl = 'wss://ws.writech.com/v1/notify';
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/// 心跳间隔（秒）
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static const int heartbeatIntervalSec = 30;
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/// 心跳超时时间（秒，超过此时间未收到心跳响应则认为连接断开）
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static const int heartbeatTimeoutSec = 45;
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/// 最大重连间隔（秒，指数退避上限）
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static const int maxReconnectIntervalSec = 60;
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/// WebSocket实例
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dynamic _webSocket; // WebSocket
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/// 连接状态
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WsConnectionState _state = WsConnectionState.disconnected;
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/// 当前认证Token
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String _authToken = '';
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/// 心跳定时器
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Timer? _heartbeatTimer;
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/// 心跳超时定时器
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Timer? _heartbeatTimeoutTimer;
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/// 重连定时器
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Timer? _reconnectTimer;
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/// 当前重连尝试次数（用于指数退避计算）
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int _reconnectAttempts = 0;
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/// 最后收到消息的时间戳（用于离线消息补发）
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int _lastMessageTimestamp = 0;
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/// 消息分发回调注册表
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final Map<WsMessageType, List<Function(WsMessage)>> _handlers = {};
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/// 连接状态变化回调
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final List<Function(WsConnectionState)> _stateListeners = [];
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/// 待ACK的消息队列（消息ID -> 超时Timer）
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final Map<String, Timer> _pendingAcks = {};
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/// 获取当前连接状态
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WsConnectionState get state => _state;
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/// 设置认证Token（登录成功后调用）
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void setAuthToken(String token) {
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_authToken = token;
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}
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/// 注册消息处理器
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/// 同一类型可注册多个处理器，按注册顺序依次执行
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void on(WsMessageType type, Function(WsMessage) handler) {
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_handlers.putIfAbsent(type, () => []);
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_handlers[type]!.add(handler);
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}
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/// 移除消息处理器
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void off(WsMessageType type, Function(WsMessage) handler) {
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_handlers[type]?.remove(handler);
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}
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/// 监听连接状态变化
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void onStateChange(Function(WsConnectionState) listener) {
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_stateListeners.add(listener);
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}
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/// 建立WebSocket连接
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/// 附带认证Token和最后消息时间戳（用于离线消息补发）
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Future<void> connect() async {
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if (_state == WsConnectionState.connected || _state == WsConnectionState.connecting) {
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return;
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}
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_updateState(WsConnectionState.connecting);
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try {
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// 构造带认证参数的WebSocket URL
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final url = '$_wsUrl?token=$_authToken&last_ts=$_lastMessageTimestamp';
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// 建立WebSocket连接
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// 实际实现: _webSocket = await WebSocket.connect(url);
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print('[WebSocket] 正在连接: $_wsUrl');
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// 模拟连接成功
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await Future.delayed(const Duration(milliseconds: 300));
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_updateState(WsConnectionState.connected);
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_reconnectAttempts = 0; // 重置重连计数
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// 启动心跳机制
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_startHeartbeat();
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// 监听消息流
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// _webSocket.listen(_onMessage, onDone: _onDisconnected, onError: _onError);
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print('[WebSocket] 连接成功');
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} catch (e) {
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print('[WebSocket] 连接失败: $e');
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_updateState(WsConnectionState.disconnected);
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_scheduleReconnect();
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}
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}
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/// 处理接收到的WebSocket消息
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void _onMessage(dynamic rawData) {
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try {
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final json = jsonDecode(rawData as String) as Map<String, dynamic>;
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final message = WsMessage.fromJson(json);
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// 更新最后消息时间戳
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if (message.timestamp > _lastMessageTimestamp) {
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_lastMessageTimestamp = message.timestamp;
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}
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// 处理心跳响应
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if (message.type == WsMessageType.heartbeatAck) {
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_onHeartbeatAck();
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return;
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}
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// 处理ACK确认
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if (message.type == WsMessageType.ack) {
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_onAckReceived(message.data['ack_id'] ?? '');
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return;
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}
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// 如果消息需要ACK，发送确认
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if (message.requireAck) {
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_sendAck(message.id);
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}
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// 分发消息到注册的处理器
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_dispatchMessage(message);
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} catch (e) {
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print('[WebSocket] 消息解析失败: $e');
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}
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}
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/// 分发消息到对应类型的处理器
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void _dispatchMessage(WsMessage message) {
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final handlers = _handlers[message.type];
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if (handlers != null && handlers.isNotEmpty) {
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for (final handler in handlers) {
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try {
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handler(message);
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} catch (e) {
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print('[WebSocket] 消息处理器异常: $e');
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}
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}
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} else {
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print('[WebSocket] 未注册的消息类型: ${message.type}');
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}
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}
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/// 发送消息确认（ACK）
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void _sendAck(String messageId) {
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_send({
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'type': 'ack',
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'data': {'ack_id': messageId},
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'timestamp': DateTime.now().millisecondsSinceEpoch,
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});
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}
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/// 处理收到的ACK确认
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void _onAckReceived(String messageId) {
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_pendingAcks[messageId]?.cancel();
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_pendingAcks.remove(messageId);
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}
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/// 启动心跳机制
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/// 每30秒发送一次心跳包，45秒内未收到响应则断开重连
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void _startHeartbeat() {
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_stopHeartbeat();
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_heartbeatTimer = Timer.periodic(
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Duration(seconds: heartbeatIntervalSec),
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(_) => _sendHeartbeat(),
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);
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}
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/// 发送心跳包
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void _sendHeartbeat() {
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_send({
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'type': 'heartbeat',
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'timestamp': DateTime.now().millisecondsSinceEpoch,
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});
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// 设置心跳超时检测
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_heartbeatTimeoutTimer?.cancel();
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_heartbeatTimeoutTimer = Timer(
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Duration(seconds: heartbeatTimeoutSec),
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() {
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print('[WebSocket] 心跳超时，断开连接');
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_onDisconnected();
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},
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);
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}
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/// 收到心跳响应，取消超时计时器
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void _onHeartbeatAck() {
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_heartbeatTimeoutTimer?.cancel();
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}
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/// 停止心跳
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void _stopHeartbeat() {
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_heartbeatTimer?.cancel();
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_heartbeatTimer = null;
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_heartbeatTimeoutTimer?.cancel();
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_heartbeatTimeoutTimer = null;
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}
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/// 发送JSON数据
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void _send(Map<String, dynamic> data) {
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if (_state != WsConnectionState.connected) return;
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try {
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final jsonStr = jsonEncode(data);
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// 实际调用: _webSocket.add(jsonStr);
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print('[WebSocket] 发送: ${data['type']}');
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} catch (e) {
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print('[WebSocket] 发送失败: $e');
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}
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}
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/// 连接断开处理
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void _onDisconnected() {
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_stopHeartbeat();
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_updateState(WsConnectionState.disconnected);
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print('[WebSocket] 连接已断开');
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_scheduleReconnect();
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}
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/// 连接错误处理
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void _onError(dynamic error) {
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print('[WebSocket] 连接错误: $error');
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_onDisconnected();
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}
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/// 安排自动重连（指数退避策略）
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/// 间隔: 1s, 2s, 4s, 8s, 16s, 32s, 60s(上限)
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void _scheduleReconnect() {
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_reconnectTimer?.cancel();
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final interval = _calculateReconnectInterval();
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_updateState(WsConnectionState.reconnecting);
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print('[WebSocket] ${interval}秒后尝试重连 (第${_reconnectAttempts + 1}次)');
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_reconnectTimer = Timer(Duration(seconds: interval), () {
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_reconnectAttempts++;
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connect();
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});
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}
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/// 计算重连间隔（指数退避，上限60秒）
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int _calculateReconnectInterval() {
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final interval = 1 << _reconnectAttempts; // 2^n
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return interval > maxReconnectIntervalSec ? maxReconnectIntervalSec : interval;
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}
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/// 更新连接状态并通知监听器
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void _updateState(WsConnectionState newState) {
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if (_state == newState) return;
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_state = newState;
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for (final listener in _stateListeners) {
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try {
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listener(newState);
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} catch (e) {
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print('[WebSocket] 状态监听器异常: $e');
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}
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}
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}
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/// 主动重连（应用前台恢复时调用）
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void reconnect() {
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if (_state == WsConnectionState.connected) return;
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_reconnectAttempts = 0;
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connect();
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}
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/// 断开连接并释放资源
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void disconnect() {
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_reconnectTimer?.cancel();
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_reconnectTimer = null;
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_stopHeartbeat();
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// 取消所有待ACK的超时计时器
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for (final timer in _pendingAcks.values) {
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timer.cancel();
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}
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_pendingAcks.clear();
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// 关闭WebSocket连接
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// 实际调用: _webSocket?.close();
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_webSocket = null;
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_updateState(WsConnectionState.disconnected);
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print('[WebSocket] 已主动断开连接');
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}
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/// 销毁服务（释放所有资源和回调）
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void dispose() {
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disconnect();
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_handlers.clear();
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_stateListeners.clear();
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}
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}
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Block a user