import os
import pymysql
from dotenv import load_dotenv


from typing import Tuple, Any, Dict, Literal, Optional
from dbutils.pooled_db import PooledDB, PooledDedicatedDBConnection
from dbutils.steady_db import SteadyDBCursor
from pymysql.cursors import DictCursor


class SyncMySQLHelper(object):
    _pool: PooledDB = None
    _instance = None

    def __new__(cls, *args, **kwargs):
        """单例"""
        if cls._instance is None:
            cls._instance = super().__new__(cls, *args, **kwargs)
        return cls._instance

    def get_pool(self):
        if self._pool is None:
            # 加载环境变量，允许通过 .env 配置本机调试数据库
            load_dotenv()
            env = (os.getenv('APP_ENV') or os.getenv('ENV') or 'local').lower()
            host = os.getenv('DB_HOST', 'rm-t4nh1xx6o2a6vj8qu3o.mysql.singapore.rds.aliyuncs.com')
            port = int(os.getenv('DB_PORT', '3306'))
            user = os.getenv('DB_USER', 'content_rw')
            password = os.getenv('DB_PASSWORD', 'bC1aH4bA1lB0')
            database = os.getenv('DB_NAME', 'content-deconstruction-test' if env in ('local','dev','development') else 'content-deconstruction')
            self._pool = PooledDB(
                creator=pymysql,
                mincached=10,
                maxconnections=20,
                blocking=True,
                host=host,
                port=port,
                user=user,
                password=password,
                database=database)

        return self._pool

    def fetchone(self, sql: str, data: Optional[Tuple[Any, ...]] = None) -> Dict[str, Any]:
        pool = self.get_pool()
        with pool.connection() as conn:  
            with conn.cursor(DictCursor) as cursor: 
                cursor.execute(sql, data)
                result = cursor.fetchone()
                return result

    def fetchall(self, sql: str, data: Optional[Tuple[Any, ...]] = None) -> Tuple[Dict[str, Any]]:
        pool = self.get_pool()
        with pool.connection() as conn: 
            with conn.cursor(DictCursor) as cursor: 
                cursor.execute(sql, data)
                result = cursor.fetchall()
                return result

    def fetchmany(self,
                  sql: str,
                  data: Optional[Tuple[Any, ...]] = None,
                  size: Optional[int] = None) -> Tuple[Dict[str, Any]]:
        pool = self.get_pool()
        with pool.connection() as conn:  
            with conn.cursor(DictCursor) as cursor: 
                cursor.execute(sql, data)
                result = cursor.fetchmany(size=size)
                return result

    def execute(self, sql: str, data: Optional[Tuple[Any, ...]] = None):
        pool = self.get_pool()
        with pool.connection() as conn:  
            with conn.cursor(DictCursor) as cursor:  
                try:
                    cursor.execute(sql, data)
                    result = conn.commit()
                    return result
                except pymysql.err.IntegrityError as e:
                    if e.args[0] == 1062:  # 重复值
                        return None
                    else:
                        raise e
                except pymysql.err.OperationalError as e:
                    if e.args[0] == 1205:  # 死锁
                        conn.rollback()
                        return None
                    else:
                        raise e


mysql = SyncMySQLHelper()