from typing import Iterator
from contextlib import contextmanager
from sqlalchemy import create_engine, text
from sqlalchemy.orm import sessionmaker, Session
from sqlalchemy.exc import OperationalError
from ..config import config
from ..logger import logger


class Database:
    """简化版数据库单例类"""
    _instance = None

    def __new__(cls):
        if cls._instance is None:
            cls._instance = super().__new__(cls)
            cls._instance._init_db()
        return cls._instance

    def _init_db(self):
        """初始化数据库连接"""
        db_config = config.database
        self.engine = create_engine(
            f"mysql+pymysql://{db_config.user}:{db_config.password}@{db_config.host}:{db_config.port}/{db_config.name}?charset=utf8mb4"
        )
        self.SessionLocal = sessionmaker(autocommit=False,
                                         autoflush=False,
                                         bind=self.engine)

        self.test_connection()

    @contextmanager
    def session(self) -> Iterator[Session]:
        """获取数据库会话"""
        db = self.SessionLocal()
        try:
            yield db
            db.commit()
        except Exception:
            db.rollback()
            raise
        finally:
            db.close()

    @classmethod
    def initialize(cls):
        """初始化数据库"""
        return cls()

    def test_connection(self):
        """测试数据库连接"""
        try:
            with self.engine.connect() as conn:
                result = conn.execute(text("SELECT 1"))
                if result.scalar() == 1:
                    # logger.info(f"数据库 [{config.database.name}] 连接成功。")
                    return True
            return False
        except OperationalError as e:
            logger.error(f"数据库 [{config.database.name}] 连接失败: {e}")
            return False
        except Exception as e:
            logger.error(f"未知错误: {e}")
            return False