import { Injectable, OnDestroy } from '@angular/core';
import { BehaviorSubject, Observable, Subject, Subscription } from 'rxjs';
import { AuthService } from './auth.service';
import { GlobalEvent } from '../models/event.model';

/**
 * 独立事件服务 - 为每个标签页提供独立的SSE连接
 * 
 * 特点：
 * 1. 非单例：通过组件级providers创建独立实例
 * 2. 简单：只处理单个会话的连接，无需多会话、映射等复杂逻辑
 * 3. 独立：每个实例管理自己的EventSource连接
 * 4. 生命周期对齐：随组件创建/销毁
 */
@Injectable()
export class IndependentEventService implements OnDestroy {
  private eventSource: EventSource | null = null;
  private isConnected = false;
  private reconnectTimeout: any = null;
  private reconnectAttempts = 0;
  private maxReconnectAttempts = 5;
  private reconnectDelay = 3000;
  private heartbeatTimeout: any = null;
  private heartbeatTimeoutDuration = 5 * 60 * 1000; // 5分钟心跳超时
  
  // 事件主题，用于广播所有事件
  private allEventsSubject = new Subject<GlobalEvent>();
  readonly events$ = this.allEventsSubject.asObservable();
  
  // 连接状态主题
  private connectionStatusSubject = new BehaviorSubject<boolean>(false);
  readonly connectionStatus$ = this.connectionStatusSubject.asObservable();
  
  // 当前连接的会话ID
  private currentSessionId: string | undefined;
  
  constructor(
    private authService: AuthService
  ) {}
  
  /**
   * 连接到事件流
   * @param sessionId 会话ID（可选，用于会话过滤）
   */
  connect(sessionId?: string): boolean {
    console.log('🔍 [IndependentEventService] 连接事件流，会话ID:', sessionId);
    
    // 断开现有连接
    this.disconnect();
    
    // 检查是否已登录
    if (!this.authService.isAuthenticated()) {
      console.warn('未登录状态，不连接事件流');
      return false;
    }
    
    // 获取认证token
    const token = this.authService.getToken();
    if (!token) {
      console.error('无法获取认证token');
      return false;
    }
    
    // 构建带认证参数的URL
    let url = `/api/logs/stream?token=${encodeURIComponent(token)}`;
    if (sessionId) {
      url += `&sessionId=${sessionId}`;
      this.currentSessionId = sessionId;
    }
    
    console.log('🔍 [IndependentEventService] 连接URL:', url);
    this.eventSource = new EventSource(url);
    
    this.eventSource.onopen = () => {
      console.log('🔍 [IndependentEventService] 事件流连接已建立');
      this.isConnected = true;
      this.connectionStatusSubject.next(true);
      this.reconnectAttempts = 0;
      
      // 启动心跳超时定时器
      this.resetHeartbeatTimeout();
      
      // 发送连接成功事件
      this.allEventsSubject.next({
        payload: {
          type: 'connection.established',
          properties: { timestamp: new Date().toISOString() }
        }
      });
    };
    
    this.eventSource.onmessage = (event) => {
      const eventData = event.data;
      
      // 处理SSE注释格式的心跳
      if (eventData === ': heartbeat' || eventData.startsWith(': ')) {
        // 重置心跳超时定时器
        this.resetHeartbeatTimeout();
        return;
      }
      
      console.log('🔍 [IndependentEventService] 收到原始事件数据:', eventData.substring(0, 200));
      
      try {
        // 解析JSON事件
        const globalEvent: GlobalEvent = JSON.parse(eventData);
        this.handleEvent(globalEvent);
      } catch (error) {
        console.log('🔍 [IndependentEventService] 非JSON事件:', eventData.substring(0, 100));
      }
    };
    
    this.eventSource.onerror = (error) => {
      console.error('🔍 [IndependentEventService] 事件流连接错误:', error);
      this.isConnected = false;
      this.connectionStatusSubject.next(false);
      
      // 清除心跳超时定时器
      this.clearHeartbeatTimeout();
      
      // 检查是否仍然登录
      if (this.authService.isAuthenticated()) {
        console.log('🔍 [IndependentEventService] 连接断开，正在重连...');
        this.scheduleReconnect(sessionId);
      } else {
        console.log('🔍 [IndependentEventService] 连接断开（用户未登录）');
      }
    };
    
    return true;
  }
  
  /**
   * 断开事件流连接
   */
  disconnect(): void {
    if (this.eventSource) {
      this.eventSource.close();
      this.eventSource = null;
      this.isConnected = false;
      this.connectionStatusSubject.next(false);
      this.currentSessionId = undefined;
      
      console.log('🔍 [IndependentEventService] 已断开事件流连接');
    }
    
    if (this.reconnectTimeout) {
      clearTimeout(this.reconnectTimeout);
      this.reconnectTimeout = null;
    }
    
    // 清除心跳超时定时器
    this.clearHeartbeatTimeout();
    
    this.reconnectAttempts = 0;
  }
  
  /**
   * 获取当前会话ID
   */
  getCurrentSessionId(): string | undefined {
    return this.currentSessionId;
  }
  
  /**
   * 检查连接状态
   */
  isConnectedStatus(): boolean {
    return this.isConnected;
  }
  
  /**
   * 处理事件
   */
  private handleEvent(event: GlobalEvent): void {
    // 任何有效事件都重置心跳超时
    this.resetHeartbeatTimeout();
    
    // 广播所有事件
    this.allEventsSubject.next(event);
    
    console.log('🔍 [IndependentEventService] 处理事件，类型:', event.payload.type);
    console.log('🔍 [IndependentEventService] 事件完整内容:', JSON.stringify(event, null, 2).substring(0, 500));
  }
  
  /**
   * 重置心跳超时定时器
   */
  private resetHeartbeatTimeout(): void {
    // 清除现有超时
    if (this.heartbeatTimeout) {
      clearTimeout(this.heartbeatTimeout);
    }
    
    // 设置新的超时定时器（5分钟）
    this.heartbeatTimeout = setTimeout(() => {
      console.warn('🔍 [IndependentEventService] 心跳超时（5分钟未收到心跳），尝试重连');
      this.isConnected = false;
      this.connectionStatusSubject.next(false);
      
      // 清除现有的重连定时器（如果有）
      if (this.reconnectTimeout) {
        clearTimeout(this.reconnectTimeout);
      }
      
      // 立即尝试重连
      if (this.authService.isAuthenticated()) {
        this.connect(this.currentSessionId);
      }
    }, this.heartbeatTimeoutDuration);
  }
  
  /**
   * 清除心跳超时定时器
   */
  private clearHeartbeatTimeout(): void {
    if (this.heartbeatTimeout) {
      clearTimeout(this.heartbeatTimeout);
      this.heartbeatTimeout = null;
    }
  }
  
  /**
   * 安排重连
   */
  private scheduleReconnect(sessionId?: string): void {
    if (this.reconnectTimeout) {
      clearTimeout(this.reconnectTimeout);
    }
    
    if (this.reconnectAttempts >= this.maxReconnectAttempts) {
      console.error('🔍 [IndependentEventService] 达到最大重连次数，停止重连');
      return;
    }
    
    this.reconnectAttempts++;
    const delay = this.reconnectDelay * Math.pow(1.5, this.reconnectAttempts - 1); // 指数退避
    
    console.log(`🔍 [IndependentEventService] ${this.reconnectAttempts}/${this.maxReconnectAttempts} 重连，等待 ${delay}ms`);
    
    this.reconnectTimeout = setTimeout(() => {
      if (this.authService.isAuthenticated()) {
        this.connect(sessionId);
      }
    }, delay);
  }
  
  /**
   * 清理资源
   */
  ngOnDestroy(): void {
    this.disconnect();
  }
}