from sqlalchemy.ext.asyncio import create_async_engine, async_sessionmaker, AsyncSession
from sqlalchemy.orm import declarative_base
from sqlalchemy import text, JSON
from sqlalchemy import exc as sqlalchemy_exc
from sqlalchemy.types import TypeDecorator
from sqlalchemy.dialects.postgresql import JSONB
import logging

from app.config import settings

logger = logging.getLogger(__name__)


class JSONType(TypeDecorator):
    """A JSON type that uses JSONB on PostgreSQL and JSON on other databases."""
    impl = JSON
    cache_ok = True

    def load_dialect_impl(self, dialect):
        if dialect.name == "postgresql":
            return dialect.type_descriptor(JSONB())
        return dialect.type_descriptor(JSON())


_db_url = settings.DATABASE_URL
_connect_args = {}
if _db_url.startswith("postgresql+asyncpg"):
    _connect_args = {"ssl": False}

engine = create_async_engine(
    _db_url,
    pool_size=10,
    max_overflow=20,
    pool_timeout=30,
    pool_recycle=3600,
    pool_pre_ping=True,
    echo=False,
    connect_args=_connect_args,
)

AsyncSessionLocal = async_sessionmaker(
    engine,
    class_=AsyncSession,
    expire_on_commit=False,
    autoflush=False,
    autocommit=False,
)

Base = declarative_base()


async def get_db() -> AsyncSession:
    async with AsyncSessionLocal() as session:
        try:
            yield session
        finally:
            await session.close()


async def check_db_connection() -> bool:
    """检查数据库连接是否正常"""
    try:
        async with AsyncSessionLocal() as session:
            await session.execute(text("SELECT 1"))
            return True
    except sqlalchemy_exc.SQLAlchemyError as e:
        logger.error(f"Database connection error: {e}", exc_info=True)
        raise ConnectionError(f"Failed to connect to database: {e}") from e
    except Exception as e:
        logger.error(f"Unexpected database error: {e}", exc_info=True)
        raise