"""
MySQL 连接池配置

该文件提供 MySQL 数据库连接池配置功能，支持：
- 单例模式
- DBUtils 连接池管理
- 连接错误处理
- 从.env文件读取配置
"""
import pymysql
from pymysql.cursors import DictCursor
from dbutils.pooled_db import PooledDB
from conf.settings import mysql_settings

# 单例装饰器
class singleton:
    def __init__(self, cls):
        self.cls = cls
        self._instance = None
    
    def __call__(self, *args, **kwargs):
        if self._instance is None:
            self._instance = self.cls(*args, **kwargs)
        return self._instance

@singleton
class MySQLPool:
    """
    MySQL 连接池管理器
    支持：
    - 单例模式
    - DBUtils 连接池管理
    - 连接错误处理
    """
    
    def __init__(self, host: str = None, port: int = None, 
                 user: str = None, password: str = None, 
                 database: str = None, charset: str = None,
                 pool_size: int = None, **kwargs):
        """
        初始化 MySQL 连接池
        
        Args:
            host: MySQL 主机地址
            port: MySQL 端口号
            user: MySQL 用户名
            password: MySQL 密码
            database: 数据库名称
            charset: 字符集
            pool_size: 连接池大小
            **kwargs: 其他 MySQL 连接参数
        """
        # 从环境变量读取配置，优先级：传入参数 > 环境变量 > 默认值
        self.host = host or mysql_settings.mysql_host
        self.port = int(port or mysql_settings.mysql_port)
        self.user = user or mysql_settings.mysql_user
        self.password = password or mysql_settings.mysql_password
        self.database = database or mysql_settings.mysql_database
        self.charset = charset or mysql_settings.mysql_charset
        self.pool_size = int(pool_size or mysql_settings.mysql_pool_size)
        self.kwargs = kwargs
        
        # 初始化 DBUtils 连接池
        self._pool = PooledDB(
            creator=pymysql,
            maxconnections=self.pool_size,
            mincached=2,
            maxcached=5,
            maxshared=3,
            blocking=True,
            maxusage=None,
            setsession=[],
            ping=0,
            host=self.host,
            port=self.port,
            user=self.user,
            password=self.password,
            database=self.database,
            charset=self.charset,
            cursorclass=DictCursor,
            **kwargs
        )
    
    def get_connection(self) -> pymysql.connections.Connection:
        """
        从连接池获取连接
        
        Returns:
            MySQL 连接对象
        """
        return self._pool.connection()
    
    def close(self):
        """
        关闭连接池
        """
        # DBUtils 连接池会自动管理连接，无需手动关闭
        pass

# 简化的接口函数，便于快速使用
def get_mysql_pool(host: str = None, port: int = None, 
                  user: str = None, password: str = None, 
                  database: str = None, charset: str = None,
                  pool_size: int = None, **kwargs) -> MySQLPool:
    """
    获取 MySQL 连接池实例
    
    Args:
        host: MySQL 主机地址
        port: MySQL 端口号
        user: MySQL 用户名
        password: MySQL 密码
        database: 数据库名称
        charset: 字符集
        pool_size: 连接池大小
        **kwargs: 其他 MySQL 连接参数
    
    Returns:
        MySQL 连接池实例
    """
    # 从环境变量读取默认值，与MySQLPool.__init__保持一致
    default_host = mysql_settings.mysql_host
    default_port = int(mysql_settings.mysql_port)
    default_user = mysql_settings.mysql_user
    default_database = mysql_settings.mysql_database
    default_charset = mysql_settings.mysql_charset
    default_pool_size = int(mysql_settings.mysql_pool_size)
    
    return MySQLPool(
        host=host or default_host,
        port=port or default_port,
        user=user or default_user,
        password=password,
        database=database or default_database,
        charset=charset or default_charset,
        pool_size=pool_size or default_pool_size,
        **kwargs
    )