// =====================================================
// 緊急連線清理工具
// =====================================================

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

export class EmergencyConnectionCleanup {
  private static instance: EmergencyConnectionCleanup;

  private constructor() {}

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

  // 立即停止所有監控和清理所有連線
  public async emergencyCleanup() {
    console.log('🚨 執行緊急連線清理...');
    
    try {
      // 1. 立即停止所有監控
      console.log('⏹️ 停止資料庫監控...');
      dbMonitor.stopMonitoring();
      
      // 2. 強制關閉所有連線池
      console.log('🔌 關閉主要資料庫連線池...');
      await db.close();
      
      console.log('🔌 關閉備援資料庫連線池...');
      await dbFailover.close();
      
      // 3. 等待一段時間讓連線完全關閉
      console.log('⏳ 等待連線關閉...');
      await new Promise(resolve => setTimeout(resolve, 2000));
      
      // 4. 檢查連線狀態
      await this.checkConnectionStatus();
      
      console.log('✅ 緊急清理完成');
      
    } catch (error) {
      console.error('❌ 緊急清理失敗:', error);
    }
  }

  // 檢查連線狀態（不建立新連線）
  private async checkConnectionStatus() {
    try {
      // 使用一個臨時連線來檢查狀態
      const tempConnection = await db.getConnection();
      
      try {
        const [statusResult] = await tempConnection.execute(`
          SHOW STATUS LIKE 'Threads_connected'
        `);
        
        const [maxConnResult] = await tempConnection.execute(`
          SHOW VARIABLES LIKE 'max_connections'
        `);
        
        const currentConnections = statusResult[0]?.Value || 0;
        const maxConnections = maxConnResult[0]?.Value || 100;
        const usagePercentage = (currentConnections / maxConnections) * 100;
        
        console.log(`📊 清理後連線狀態: ${currentConnections}/${maxConnections} (${usagePercentage.toFixed(1)}%)`);
        
        if (currentConnections > 5) {
          console.warn(`⚠️ 仍有 ${currentConnections} 個連線未關閉`);
        } else {
          console.log('✅ 連線已成功清理');
        }
        
      } finally {
        tempConnection.release();
      }
      
    } catch (error) {
      console.error('❌ 檢查連線狀態失敗:', error);
    }
  }

  // 強制殺死所有資料庫連線
  public async forceKillAllConnections() {
    console.log('💀 強制殺死所有資料庫連線...');
    
    try {
      const tempConnection = await db.getConnection();
      
      try {
        // 獲取所有連線ID
        const [connections] = await tempConnection.execute(`
          SELECT ID FROM information_schema.PROCESSLIST 
          WHERE USER = ? AND COMMAND != 'Sleep'
        `, [process.env.DB_USER || 'A999']);
        
        console.log(`🔍 找到 ${connections.length} 個活躍連線`);
        
        // 殺死所有連線（除了當前連線）
        for (const conn of connections) {
          if (conn.ID !== tempConnection.threadId) {
            try {
              await tempConnection.execute(`KILL ${conn.ID}`);
              console.log(`💀 已殺死連線 ${conn.ID}`);
            } catch (error) {
              console.log(`⚠️ 無法殺死連線 ${conn.ID}:`, error.message);
            }
          }
        }
        
        // 等待連線關閉
        await new Promise(resolve => setTimeout(resolve, 1000));
        
        // 再次檢查狀態
        await this.checkConnectionStatus();
        
      } finally {
        tempConnection.release();
      }
      
    } catch (error) {
      console.error('❌ 強制殺死連線失敗:', error);
    }
  }

  // 獲取連線詳情
  public async getConnectionDetails() {
    try {
      const tempConnection = await db.getConnection();
      
      try {
        const [connections] = await tempConnection.execute(`
          SELECT 
            ID,
            USER,
            HOST,
            DB,
            COMMAND,
            TIME,
            STATE,
            INFO
          FROM information_schema.PROCESSLIST 
          WHERE USER = ?
          ORDER BY TIME DESC
        `, [process.env.DB_USER || 'A999']);
        
        console.log('📋 當前資料庫連線詳情:');
        connections.forEach((conn, index) => {
          console.log(`${index + 1}. ID: ${conn.ID}, 用戶: ${conn.USER}, 時間: ${conn.TIME}s, 狀態: ${conn.STATE}`);
          if (conn.INFO && conn.INFO.length > 50) {
            console.log(`   查詢: ${conn.INFO.substring(0, 50)}...`);
          } else if (conn.INFO) {
            console.log(`   查詢: ${conn.INFO}`);
          }
        });
        
        return connections;
        
      } finally {
        tempConnection.release();
      }
      
    } catch (error) {
      console.error('❌ 獲取連線詳情失敗:', error);
      return [];
    }
  }
}

// 導出單例實例
export const emergencyCleanup = EmergencyConnectionCleanup.getInstance();