/**
 * @file MySQLConnection.ts
 * @version 1.0.1
 * @description MySQL数据库连接池
 * 
 * 该文件提供了MySQL数据库连接池的实现，包括以下功能：
 * - 创建数据库连接池
 * - 自动测试数据库连接
 * - 数据库基础错误处理
 * 
 * ## 配置项说明
 * 在 `config.ts` 文件中，可以配置以下选项：
 * - `enable`: 是否启用 MySQL 数据库
 * - `host`: 数据库主机地址
 * - `port`: 数据库端口号
 * - `database`: 数据库名称
 * - `user`: 数据库用户名
 * - `password`: 数据库密码
 * 
 */
import mysql from "mysql2/promise";
import Logger from "@lib/Logger/Logger";
import config from "../../config";

class MySQLConnectPool {
    private pool: any;
    private logger = new Logger('MySQL');

    constructor() {
        if (!config.mysql.enable) {
            this.logger.warn('Database is disabled, initialization terminated');
            return;
        }
        this.pool = this.createConnectPool();
        this.logger.info("Database connection pool created")
        setTimeout(async () => {
            let res = await this.testConnection();
            if (res)
                this.logger.info("Database test successful")
            else
                this.logger.error("Database test failed")
        }, 10);
    }

    private createConnectPool() {
        return mysql.createPool({
            host: config.mysql.host,
            database: config.mysql.database,
            port: config.mysql.port,
            user: config.mysql.user,
            password: config.mysql.password,
            waitForConnections: true,
            connectionLimit: 10,
            queueLimit: 0
        })
    }

    private async testConnection() {
        try {
            let res = await this.execute("SELECT 1 + 1 As result");
            if (res[0].result == 2)
                return 1;
            else
                return 0;
        } catch (error) {
            this.logger.error(`An error occurred during the database test: ` + error);
            return 0;
        }

    }

    /**
     * 执行SQL查询
     * @param sql SQL语句
     * @param values 可选的查询参数列表
     * @param database 可选的数据库
     * @returns Promise<any | undefined> 查询结果
     */
    public async execute(sql: string, values?: any[], database?: string): Promise<any | undefined> {
        let connection: any;
        try {
            connection = await this.pool.getConnection();

            // 如果指定了数据库，则更改当前连接的数据库
            if (database) {
                await connection.changeUser({ database });
            }

            let [rows, fields] = await connection.execute(sql, values);
            return rows;
        } catch (error) {
            this.logger.error("An error occurred in the database: " + error, '\n##', sql, '\n##', JSON.stringify(values));
            return undefined;
        } finally {
            if (database)
                await connection.changeUser({ database: config.mysql.database });// 恢复默认数据库
            if (connection)
                connection.release();
        }
    }
}

const MySQLConnection = new MySQLConnectPool();
export default MySQLConnection;