// =====================================================
// 連線生命週期管理器
// =====================================================

import { db } from './database';
import { dbFailover } from './database-failover';

export class ConnectionLifecycleManager {
  private static instance: ConnectionLifecycleManager;
  private activeConnections = new Map<string, {
    connection: any;
    createdAt: number;
    lastUsed: number;
    userId?: string;
    sessionId?: string;
  }>();
  private cleanupInterval: NodeJS.Timeout | null = null;
  private maxIdleTime = 5 * 60 * 1000; // 5分鐘空閒超時
  private maxConnectionAge = 30 * 60 * 1000; // 30分鐘最大連線時間

  private constructor() {
    this.startCleanupProcess();
  }

  public static getInstance(): ConnectionLifecycleManager {
    if (!ConnectionLifecycleManager.instance) {
      ConnectionLifecycleManager.instance = new ConnectionLifecycleManager();
    }
    return ConnectionLifecycleManager.instance;
  }

  // 註冊連線
  public registerConnection(connectionId: string, connection: any, metadata?: {
    userId?: string;
    sessionId?: string;
  }) {
    this.activeConnections.set(connectionId, {
      connection,
      createdAt: Date.now(),
      lastUsed: Date.now(),
      userId: metadata?.userId,
      sessionId: metadata?.sessionId
    });

    console.log(`📝 註冊連線: ${connectionId} (總數: ${this.activeConnections.size})`);
  }

  // 更新連線使用時間
  public updateConnectionUsage(connectionId: string) {
    const conn = this.activeConnections.get(connectionId);
    if (conn) {
      conn.lastUsed = Date.now();
    }
  }

  // 釋放連線
  public releaseConnection(connectionId: string) {
    const conn = this.activeConnections.get(connectionId);
    if (conn) {
      try {
        if (conn.connection && typeof conn.connection.release === 'function') {
          conn.connection.release();
        }
        this.activeConnections.delete(connectionId);
        console.log(`🗑️ 釋放連線: ${connectionId} (剩餘: ${this.activeConnections.size})`);
      } catch (error) {
        console.error(`❌ 釋放連線失敗: ${connectionId}`, error);
      }
    }
  }

  // 開始清理程序
  private startCleanupProcess() {
    // 每30秒檢查一次空閒連線
    this.cleanupInterval = setInterval(() => {
      this.cleanupIdleConnections();
    }, 30 * 1000);

    console.log('🧹 連線生命週期管理器已啟動');
  }

  // 清理空閒連線
  private cleanupIdleConnections() {
    const now = Date.now();
    const toRemove: string[] = [];

    for (const [connectionId, conn] of this.activeConnections) {
      const idleTime = now - conn.lastUsed;
      const connectionAge = now - conn.createdAt;

      // 檢查空閒時間
      if (idleTime > this.maxIdleTime) {
        console.log(`⏰ 連線 ${connectionId} 空閒時間過長 (${Math.round(idleTime / 1000)}s)，準備釋放`);
        toRemove.push(connectionId);
      }
      // 檢查連線年齡
      else if (connectionAge > this.maxConnectionAge) {
        console.log(`⏰ 連線 ${connectionId} 存在時間過長 (${Math.round(connectionAge / 1000)}s)，準備釋放`);
        toRemove.push(connectionId);
      }
    }

    // 釋放需要清理的連線
    toRemove.forEach(connectionId => {
      this.releaseConnection(connectionId);
    });

    if (toRemove.length > 0) {
      console.log(`🧹 清理了 ${toRemove.length} 個空閒連線`);
    }
  }

  // 強制清理所有連線
  public forceCleanupAll() {
    console.log('🚨 強制清理所有連線...');
    
    const connectionIds = Array.from(this.activeConnections.keys());
    connectionIds.forEach(connectionId => {
      this.releaseConnection(connectionId);
    });

    console.log(`✅ 已清理 ${connectionIds.length} 個連線`);
  }

  // 獲取連線統計
  public getConnectionStats() {
    const now = Date.now();
    const connections = Array.from(this.activeConnections.values());
    
    const idleConnections = connections.filter(conn => 
      now - conn.lastUsed > this.maxIdleTime
    ).length;

    const oldConnections = connections.filter(conn => 
      now - conn.createdAt > this.maxConnectionAge
    ).length;

    return {
      totalConnections: this.activeConnections.size,
      idleConnections,
      oldConnections,
      maxIdleTime: this.maxIdleTime,
      maxConnectionAge: this.maxConnectionAge,
      connections: connections.map(conn => ({
        createdAt: new Date(conn.createdAt).toISOString(),
        lastUsed: new Date(conn.lastUsed).toISOString(),
        idleTime: now - conn.lastUsed,
        age: now - conn.createdAt,
        userId: conn.userId,
        sessionId: conn.sessionId
      }))
    };
  }

  // 停止清理程序
  public stop() {
    if (this.cleanupInterval) {
      clearInterval(this.cleanupInterval);
      this.cleanupInterval = null;
    }
    
    // 清理所有連線
    this.forceCleanupAll();
    
    console.log('⏹️ 連線生命週期管理器已停止');
  }

  // 設置清理參數
  public setCleanupParams(maxIdleTime?: number, maxConnectionAge?: number) {
    if (maxIdleTime) this.maxIdleTime = maxIdleTime;
    if (maxConnectionAge) this.maxConnectionAge = maxConnectionAge;
    
    console.log(`⚙️ 更新清理參數: 空閒時間=${this.maxIdleTime}ms, 最大年齡=${this.maxConnectionAge}ms`);
  }
}

// 導出單例實例
export const connectionLifecycleManager = ConnectionLifecycleManager.getInstance();