from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker
from datetime import datetime, timezone
from backend.config import settings
import sqlite3

# SQLite 类型转换器：将从数据库读取的字符串转换为 timezone-aware datetime
def convert_timestamp(val):
    """将从数据库读取的字符串转换为 timezone-aware datetime (UTC)"""
    if val is None:
        return None
    # 解析 ISO 8601 格式的字符串
    try:
        dt = datetime.fromisoformat(val.decode() if isinstance(val, bytes) else val)
        # 如果是 naive datetime，添加 UTC timezone
        if dt.tzinfo is None:
            dt = dt.replace(tzinfo=timezone.utc)
        return dt
    except (ValueError, AttributeError):
        return None

# 注册 SQLite 类型转换器（全局）
sqlite3.register_converter("DATETIME", convert_timestamp)
sqlite3.register_converter("TIMESTAMP", convert_timestamp)

# 创建数据库引擎
# 为 SQLite 连接添加 detect_types 参数以启用类型转换
engine = create_engine(
    settings.DATABASE_URL,
    connect_args={
        "check_same_thread": False,  # SQLite 特定配置
        "detect_types": sqlite3.PARSE_DECLTYPES | sqlite3.PARSE_COLNAMES  # 启用类型转换
    },
    echo=False,  # 生产环境设为 False
)

# 创建会话工厂
SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)

# 创建基类
Base = declarative_base()


def get_db():
    """依赖注入：获取数据库会话"""
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()


def init_db():
    """初始化数据库：创建所有表"""
    Base.metadata.create_all(bind=engine)