"""
DAO 基类

提供数据访问对象的通用方法和辅助函数
"""

from typing import Optional
from config.schema import DatabaseType
from db.base_connection import BaseDatabaseConnection
from db.connection import get_connection
from db.table_name_converter import TableNameConverter


class BaseDAO:
    """数据访问对象基类"""

    def __init__(self):
        """初始化 DAO"""
        self.db: Optional[BaseDatabaseConnection] = None
        # 从配置文件加载数据库类型
        from config.loader import ConfigLoader
        app_config = ConfigLoader.load()
        self._db_type = app_config.database.db_type

    def __enter__(self):
        """进入上下文管理器，建立数据库连接"""
        self.db = get_connection()
        self.db.connect()
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        """退出上下文管理器，关闭数据库连接"""
        if self.db:
            self.db.disconnect()

    def close(self):
        """关闭数据库连接"""
        if self.db:
            self.db.disconnect()

    def _convert_sql(self, sql: str) -> str:
        """
        根据当前数据库类型转换 SQL 语句中的表名

        Args:
            sql: 原始 SQL 语句（SQL Server 格式）

        Returns:
            转换后的 SQL 语句
        """
        if self._db_type == DatabaseType.MYSQL:
            # SQL Server → MySQL
            return TableNameConverter.convert_sql(sql, 'mysql')
        return sql

    def _get_placeholder(self) -> str:
        """
        获取当前数据库类型的参数占位符

        Returns:
            SQL Server 返回 "?"，MySQL 返回 "%s"
        """
        if self._db_type == DatabaseType.MYSQL:
            return "%s"
        return "?"

    def _build_placeholders(self, count: int) -> str:
        """
        构建参数占位符字符串

        Args:
            count: 占位符数量

        Returns:
            占位符字符串，如 "?, ?, ?" 或 "%s, %s, %s"
        """
        placeholder = self._get_placeholder()
        return ", ".join([placeholder for _ in range(count)])

    def _build_in_clause_placeholders(self, count: int) -> str:
        """
        构建 IN 子句的参数占位符字符串

        Args:
            count: 占位符数量

        Returns:
            IN 子句占位符字符串，如 "?, ?, ?" 或 "%s, %s, %s"
        """
        placeholder = self._get_placeholder()
        return ", ".join([placeholder for _ in range(count)])

    def _get_connection(self):
        """
        获取数据库连接

        Returns:
            数据库连接对象
        """
        return get_connection()