"""
数据库连接管理模块
提供数据库连接池和配置管理功能
"""

import os
import sqlite3
from typing import Optional, Dict, Any
from contextlib import contextmanager
from sqlalchemy import create_engine, Engine, text
from sqlalchemy.orm import sessionmaker, Session
from sqlalchemy.pool import QueuePool
from backend.utils.logger_config import setup_logger

logger = setup_logger(__name__)

class DatabaseConnection:
    """数据库连接管理类"""
    
    def __init__(self, db_type: str = "sqlite", **kwargs):
        """
        初始化数据库连接
        
        Args:
            db_type: 数据库类型 ("sqlite" 或 "mysql")
            **kwargs: 数据库连接参数
        """
        self.db_type = db_type.lower()
        self.engine: Optional[Engine] = None
        self.SessionLocal: Optional[sessionmaker] = None
        self.connection_params = kwargs
        self._setup_connection()
    
    def _setup_connection(self):
        """设置数据库连接"""
        try:
            if self.db_type == "sqlite":
                self._setup_sqlite()
            elif self.db_type == "mysql":
                self._setup_mysql()
            else:
                raise ValueError(f"不支持的数据库类型: {self.db_type}")
            
            # 创建会话工厂
            self.SessionLocal = sessionmaker(
                autocommit=False,
                autoflush=False,
                bind=self.engine
            )
            
            logger.info(f"数据库连接初始化成功: {self.db_type}")
            
        except Exception as e:
            logger.error(f"数据库连接初始化失败: {e}")
            raise
    
    def _setup_sqlite(self):
        """设置SQLite连接"""
        db_path = self.connection_params.get('database', './backend/db/ai_swap.db')
        
        # 确保数据库目录存在
        db_dir = os.path.dirname(db_path)
        if db_dir and not os.path.exists(db_dir):
            os.makedirs(db_dir)
        
        # 创建SQLite引擎
        self.engine = create_engine(
            f"sqlite:///{db_path}",
            connect_args={"check_same_thread": False},
            poolclass=QueuePool,
            pool_size=10,
            max_overflow=20,
            pool_pre_ping=True,
            echo=False  # 设置为True可以看到SQL语句
        )
    
    def _setup_mysql(self):
        """设置MySQL连接"""
        host = self.connection_params.get('host', 'localhost')
        port = self.connection_params.get('port', 3306)
        database = self.connection_params.get('database', 'ai_swap')
        username = self.connection_params.get('username', 'root')
        password = self.connection_params.get('password', '')
        charset = self.connection_params.get('charset', 'utf8mb4')
        
        # 构建MySQL连接URL
        mysql_url = f"mysql+pymysql://{username}:{password}@{host}:{port}/{database}?charset={charset}"
        
        # 创建MySQL引擎
        self.engine = create_engine(
            mysql_url,
            poolclass=QueuePool,
            pool_size=10,
            max_overflow=20,
            pool_pre_ping=True,
            pool_recycle=3600,  # 连接回收时间
            echo=False
        )
    
    @contextmanager
    def get_session(self) -> Session:
        """
        获取数据库会话的上下文管理器
        
        Yields:
            Session: 数据库会话对象
        """
        session = self.SessionLocal()
        try:
            yield session
            session.commit()
        except Exception as e:
            session.rollback()
            logger.error(f"数据库操作失败: {e}")
            raise
        finally:
            session.close()
    
    def get_engine(self) -> Engine:
        """获取数据库引擎"""
        return self.engine
    
    def test_connection(self) -> bool:
        """
        测试数据库连接
        
        Returns:
            bool: 连接是否成功
        """
        try:
            with self.get_session() as session:
                if self.db_type == "sqlite":
                    session.execute(text("SELECT 1"))
                else:
                    session.execute(text("SELECT 1"))
            logger.info("数据库连接测试成功")
            return True
        except Exception as e:
            logger.error(f"数据库连接测试失败: {e}")
            return False
    
    def close(self):
        """关闭数据库连接"""
        if self.engine:
            self.engine.dispose()
            logger.info("数据库连接已关闭")

# 默认数据库连接实例
default_db = DatabaseConnection(
    db_type="sqlite",
    database="backend/data/ai_swap.db"
)