# app/database.py
from sqlalchemy.orm import DeclarativeBase
from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine, AsyncEngine
from contextlib import asynccontextmanager
from typing import AsyncGenerator

from .config import settings


# ====================== 1. 基类定义 ======================
class Base(DeclarativeBase):
    """SQLAlchemy 2.0 声明式基类"""
    pass


# ====================== 2. 异步URL转换 ======================
def ensure_async_url(database_url: str) -> str:
    """确保使用异步数据库URL"""
    # 如果已经是异步URL，直接返回
    if any(x in database_url for x in ["+asyncpg", "+aiomysql", "+aiosqlite"]):
        return database_url
    
    # 转换同步URL为异步URL
    if database_url.startswith("postgresql://"):
        return database_url.replace("postgresql://", "postgresql+asyncpg://")
    elif database_url.startswith("mysql://"):
        return database_url.replace("mysql://", "mysql+aiomysql://")
    elif database_url.startswith("sqlite://"):
        return database_url.replace("sqlite://", "sqlite+aiosqlite://")
    else:
        raise ValueError(f"不支持的数据库类型: {database_url}")


# ====================== 3. 异步引擎配置 ======================
async_database_url = ensure_async_url(settings.DATABASE_URL)

# 连接参数
connect_args = {}
if "sqlite+aiosqlite" in async_database_url:
    connect_args = {"check_same_thread": False}

async_engine: AsyncEngine = create_async_engine(
    async_database_url,
    connect_args=connect_args,
    echo=settings.DEBUG,
    pool_size=20,
    max_overflow=10,
    pool_pre_ping=True,
    future=True,  # 启用2.0特性
)


# ====================== 4. 异步会话工厂 ======================
AsyncSessionLocal = async_sessionmaker(
    bind=async_engine,
    class_=AsyncSession,
    expire_on_commit=False,
    autoflush=False,
)


# ====================== 5. 异步依赖注入 ======================
async def get_async_db() -> AsyncGenerator[AsyncSession, None]:
    """
    FastAPI兼容的异步数据库依赖
    注意：移除了@asynccontextmanager装饰器
    """
    session = AsyncSessionLocal()
    try:
        yield session
        await session.commit()
    except Exception:
        await session.rollback()
        raise
    finally:
        await session.close()


# ====================== 6. 数据库初始化 ======================
async def init_async_db():
    """异步初始化数据库"""
    from .models.user import User
    from sqlalchemy import select
    from .core.security import password_hasher
    
    # 创建表
    async with async_engine.begin() as conn:
        await conn.run_sync(Base.metadata.create_all)
    print("✅ 数据库表创建完成")
    
    # 创建默认管理员用户
    async with AsyncSessionLocal() as session:
        try:
            # 异步查询
            stmt = select(User).where(User.username == "admin")
            result = await session.execute(stmt)
            admin = result.scalar_one_or_none()
            
            if not admin:
                admin_user = User(
                    username="admin",
                    email="admin@caiyouhui.com",
                    hashed_password=password_hasher.hash_password("Admin123!"),
                    full_name="系统管理员",
                    is_active=True,
                    is_verified=True,
                    is_superuser=True
                )
                session.add(admin_user)
                await session.commit()
                print("✅ 默认管理员用户已创建")
        except Exception as e:
            print(f"⚠️  创建管理员用户时出错: {e}")
            await session.rollback()


# ====================== 7. 连接健康检查 ======================
async def check_async_connection():
    """检查数据库连接"""
    from sqlalchemy import text  # 需要导入text
    try:
        async with async_engine.connect() as conn:
            await conn.execute(text("SELECT 1"))
        print("✅ 数据库连接正常")
        return True
    except Exception as e:
        print(f"❌ 数据库连接失败: {e}")
        return False


# ====================== 8. 导出 ======================
__all__ = [
    "Base",
    "async_engine", 
    "AsyncSessionLocal",
    "get_async_db",
    "init_async_db",
    "check_async_connection",
]