// =====================================================
// 資料庫連接配置
// =====================================================

import mysql from 'mysql2/promise';

// 資料庫配置
const dbConfig = {
  host: process.env.DB_HOST || 'mysql.theaken.com',
  port: parseInt(process.env.DB_PORT || '33306'),
  user: process.env.DB_USER || 'AI_Platform',
  password: process.env.DB_PASSWORD || 'Aa123456',
  database: process.env.DB_NAME || 'db_AI_Platform',
  charset: 'utf8mb4',
  timezone: '+08:00',
  acquireTimeout: 60000,
  timeout: 60000,
  reconnect: true,
  connectionLimit: 10,
  queueLimit: 0,
};

// 創建連接池
const pool = mysql.createPool(dbConfig);

// 資料庫連接類
export class Database {
  private static instance: Database;
  private pool: mysql.Pool;

  private constructor() {
    this.pool = pool;
  }

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

  // 獲取連接
  public async getConnection(): Promise<mysql.PoolConnection> {
    return await this.pool.getConnection();
  }

  // 執行查詢
  public async query<T = any>(sql: string, params?: any[]): Promise<T[]> {
    const connection = await this.getConnection();
    try {
      const [rows] = await connection.execute(sql, params);
      return rows as T[];
    } finally {
      connection.release();
    }
  }

  // 執行單一查詢
  public async queryOne<T = any>(sql: string, params?: any[]): Promise<T | null> {
    const results = await this.query<T>(sql, params);
    return results.length > 0 ? results[0] : null;
  }

  // 執行插入
  public async insert(sql: string, params?: any[]): Promise<mysql.ResultSetHeader> {
    const connection = await this.getConnection();
    try {
      const [result] = await connection.execute(sql, params);
      return result as mysql.ResultSetHeader;
    } finally {
      connection.release();
    }
  }

  // 執行更新
  public async update(sql: string, params?: any[]): Promise<mysql.ResultSetHeader> {
    const connection = await this.getConnection();
    try {
      const [result] = await connection.execute(sql, params);
      return result as mysql.ResultSetHeader;
    } finally {
      connection.release();
    }
  }

  // 執行刪除
  public async delete(sql: string, params?: any[]): Promise<mysql.ResultSetHeader> {
    const connection = await this.getConnection();
    try {
      const [result] = await connection.execute(sql, params);
      return result as mysql.ResultSetHeader;
    } finally {
      connection.release();
    }
  }

  // 開始事務
  public async beginTransaction(): Promise<mysql.PoolConnection> {
    const connection = await this.getConnection();
    await connection.beginTransaction();
    return connection;
  }

  // 提交事務
  public async commit(connection: mysql.PoolConnection): Promise<void> {
    await connection.commit();
    connection.release();
  }

  // 回滾事務
  public async rollback(connection: mysql.PoolConnection): Promise<void> {
    await connection.rollback();
    connection.release();
  }

  // 關閉連接池
  public async close(): Promise<void> {
    await this.pool.end();
  }
}

// 導出單例實例
export const db = Database.getInstance();

// 導出類型
export type { PoolConnection } from 'mysql2/promise';