/**
 * 数据库连接池配置
 * @file database-pool.js
 * @description 配置和管理Sequelize数据库连接池
 */
const { Sequelize } = require('sequelize');
const { EventEmitter } = require('events');
const logger = require('../utils/logger');
const ormConfig = require('./orm-config');

// 从环境变量获取数据库连接参数
const DB_DIALECT = process.env.DB_DIALECT || 'mysql';
const DB_STORAGE = process.env.DB_STORAGE || './database.sqlite';
const DB_NAME = process.env.DB_NAME || 'nxTest';
const DB_USER = process.env.DB_USER || 'root';
const DB_PASSWORD = process.env.DB_PASSWORD || 'Aiotagro@741';
const DB_HOST = process.env.DB_HOST || '129.211.213.226';
const DB_PORT = process.env.DB_PORT || 3306;

// 数据库连接池事件发射器
class DatabasePoolEmitter extends EventEmitter {}
const poolEvents = new DatabasePoolEmitter();

// 默认连接池配置
const DEFAULT_POOL_CONFIG = {
  max: parseInt(process.env.DB_POOL_MAX || '10'), // 最大连接数
  min: parseInt(process.env.DB_POOL_MIN || '2'),  // 最小连接数
  acquire: parseInt(process.env.DB_POOL_ACQUIRE || '30000'), // 获取连接超时时间（毫秒）
  idle: parseInt(process.env.DB_POOL_IDLE || '10000'),      // 连接空闲多久后释放（毫秒）
  evict: parseInt(process.env.DB_POOL_EVICT || '1000'),     // 多久检查一次空闲连接（毫秒）
};

// 创建Sequelize实例
let sequelize;
if (DB_DIALECT === 'sqlite') {
  sequelize = new Sequelize({
    dialect: 'sqlite',
    storage: DB_STORAGE,
    logging: (msg) => logger.debug(msg),
    benchmark: process.env.NODE_ENV !== 'production',
    pool: DEFAULT_POOL_CONFIG,
    define: ormConfig.defaultModelOptions
  });
} else {
  sequelize = new Sequelize(DB_NAME, DB_USER, DB_PASSWORD, {
    host: DB_HOST,
    port: DB_PORT,
    dialect: DB_DIALECT,
    logging: (msg) => logger.debug(msg),
    benchmark: process.env.NODE_ENV !== 'production',
    pool: DEFAULT_POOL_CONFIG,
    define: ormConfig.defaultModelOptions,
    dialectOptions: {
      charset: 'utf8mb4',
      supportBigNumbers: true,
      bigNumberStrings: true,
      dateStrings: true,
      multipleStatements: process.env.DB_MULTIPLE_STATEMENTS === 'true'
    },
    timezone: '+08:00'
  });
}

// 监听连接池事件 - 使用Sequelize实例的hooks
sequelize.addHook('afterConnect', (connection, config) => {
  logger.info(`数据库连接已建立`);
  poolEvents.emit('connect', connection);
});

sequelize.addHook('beforeDisconnect', (connection) => {
  logger.info(`数据库连接即将断开`);
  poolEvents.emit('disconnect', connection);
});

// 注意：acquire和release事件在新版Sequelize中需要通过其他方式监听
// 这里我们使用定时器来监控连接池状态
setInterval(() => {
  if (sequelize.connectionManager && sequelize.connectionManager.pool) {
    const pool = sequelize.connectionManager.pool;
    poolEvents.emit('poolStatus', {
      size: pool.size || 0,
      available: pool.available || 0,
      using: pool.using || 0,
      waiting: pool.waiting || 0
    });
  }
}, 30000); // 每30秒检查一次连接池状态

// 测试数据库连接
async function testConnection() {
  try {
    await sequelize.authenticate();
    logger.info('数据库连接测试成功');
    poolEvents.emit('connectionSuccess');
    return { success: true, message: '数据库连接测试成功' };
  } catch (error) {
    logger.error('数据库连接测试失败:', error);
    poolEvents.emit('connectionError', error);
    return { success: false, message: error.message };
  }
}

// 获取连接池状态
async function getPoolStatus() {
  try {
    const pool = sequelize.connectionManager.pool;
    if (!pool) {
      return { error: '连接池未初始化' };
    }

    // 获取连接池统计信息
    const status = {
      all: pool.size,                // 所有连接数
      idle: pool.idleCount,          // 空闲连接数
      used: pool.size - pool.idleCount, // 使用中的连接数
      waiting: pool.pending,         // 等待连接的请求数
      max: pool.options.max,         // 最大连接数
      min: pool.options.min,         // 最小连接数
      acquire: pool.options.acquire, // 获取连接超时时间
      idle: pool.options.idle,       // 空闲超时时间
      created: new Date().toISOString(), // 状态创建时间
      utilization: (pool.size > 0) ? ((pool.size - pool.idleCount) / pool.size) * 100 : 0 // 利用率
    };

    poolEvents.emit('poolStatus', status);
    return status;
  } catch (error) {
    logger.error('获取连接池状态失败:', error);
    return { error: error.message };
  }
}

// 监控连接池
async function monitorPool(interval = 60000) {
  try {
    const status = await getPoolStatus();
    logger.debug('连接池状态:', status);

    // 检查连接池利用率
    if (status.utilization > 80) {
      logger.warn(`连接池利用率过高: ${status.utilization.toFixed(2)}%`);
      poolEvents.emit('highUtilization', status);
    }

    // 检查等待连接的请求数
    if (status.waiting > 5) {
      logger.warn(`连接池等待请求过多: ${status.waiting}`);
      poolEvents.emit('highWaiting', status);
    }

    return status;
  } catch (error) {
    logger.error('监控连接池失败:', error);
    return { error: error.message };
  }
}

// 关闭连接池
async function closePool() {
  try {
    await sequelize.close();
    logger.info('数据库连接池已关闭');
    poolEvents.emit('poolClosed');
    return { success: true, message: '数据库连接池已关闭' };
  } catch (error) {
    logger.error('关闭数据库连接池失败:', error);
    return { success: false, message: error.message };
  }
}

// 重置连接池
async function resetPool() {
  try {
    await closePool();
    
    // 重新初始化连接池
    sequelize.connectionManager.initPools();
    
    // 测试新的连接池
    const testResult = await testConnection();
    
    if (testResult.success) {
      logger.info('数据库连接池已重置');
      poolEvents.emit('poolReset');
      return { success: true, message: '数据库连接池已重置' };
    } else {
      throw new Error(testResult.message);
    }
  } catch (error) {
    logger.error('重置数据库连接池失败:', error);
    poolEvents.emit('poolResetError', error);
    return { success: false, message: error.message };
  }
}

// 优化连接池配置
async function optimizePool(config = {}) {
  try {
    // 获取当前状态
    const currentStatus = await getPoolStatus();
    
    // 计算新的配置
    const newConfig = {
      max: config.max || Math.max(currentStatus.max, Math.ceil(currentStatus.used * 1.5)),
      min: config.min || Math.min(currentStatus.min, Math.floor(currentStatus.used * 0.5)),
      acquire: config.acquire || currentStatus.acquire,
      idle: config.idle || currentStatus.idle
    };
    
    // 确保最小连接数不小于1
    newConfig.min = Math.max(newConfig.min, 1);
    
    // 确保最大连接数不小于最小连接数
    newConfig.max = Math.max(newConfig.max, newConfig.min);
    
    // 应用新配置
    await closePool();
    
    // 更新连接池配置
    sequelize.options.pool = newConfig;
    
    // 重新初始化连接池
    sequelize.connectionManager.initPools();
    
    // 测试新的连接池
    const testResult = await testConnection();
    
    if (testResult.success) {
      logger.info('数据库连接池已优化:', newConfig);
      poolEvents.emit('poolOptimized', newConfig);
      return { success: true, message: '数据库连接池已优化', config: newConfig };
    } else {
      throw new Error(testResult.message);
    }
  } catch (error) {
    logger.error('优化数据库连接池失败:', error);
    poolEvents.emit('poolOptimizationError', error);
    return { success: false, message: error.message };
  }
}

// 获取数据库表列表
async function getTablesList() {
  try {
    const [results] = await sequelize.query(
      `SELECT TABLE_NAME FROM information_schema.TABLES 
       WHERE TABLE_SCHEMA = ? 
       ORDER BY TABLE_NAME`,
      { replacements: [DB_NAME] }
    );
    
    return results.map(row => row.TABLE_NAME);
  } catch (error) {
    logger.error('获取数据库表列表失败:', error);
    return [];
  }
}

// 导出模块
module.exports = {
  sequelize,
  testConnection,
  getPoolStatus,
  monitorPool,
  closePool,
  resetPool,
  optimizePool,
  getTablesList,
  events: poolEvents
};