#!/usr/bin/env python3
# -*- coding:utf-8 -*-
from sqlalchemy import create_engine, text
from sqlalchemy.dialects.mysql import pymysql
from sqlalchemy.orm import sessionmaker
from sqlalchemy.ext.declarative import declarative_base
from config import database_config
import pandas as pd


class Mysql(object):
    def __init__(self):
        host = database_config.MYSQL_HOST
        port = database_config.MYSQL_PORT
        user = database_config.MYSQL_USER
        passwd = database_config.MYSQL_PASSWD
        dbname = database_config.MYSQL_DB
        
        # 通过连接池创建engine
        self.engine = create_engine(
            self._connect(host, port, user, passwd, dbname),
            pool_size=10, # 设置连接池大小
            max_overflow=20, # 超过连接池大小时的额外连接数
            pool_recycle=3600 # 回收连接时间
        )
        self._DBSession = sessionmaker(bind=self.engine)

    def _connect(self, host, port, user, pwd, db):
        try:
            client = "mysql+pymysql://" + user + ":" + pwd + "@" + host + ":" + str(port) + "/" + db
            return client
        except Exception as e:
            raise ConnectionError(f"failed to create connection string: {e}")
        
    def create_session(self):
        """创建返回一个新的数据库session"""
        return self._DBSession()

    def closed(self):
        """关闭连接，回收资源"""
        self.engine.dispose()


if __name__ == '__main__':
    client = Mysql()
    # 创建会话
    session = client.create_session()
    
    # 使用 session 执行查询等操作
    try:
        results = session.execute(
            text("select * from tads_brandcul_cust_order")
            ).mappings().all()
        # 将结果转换为DataFrame
        df = pd.DataFrame(results) # 提取列名
        print(df)
    finally:
        session.close()