"""MySQL 비동기 세션.

FastAPI 의존성으로 쓴다:
    async def handler(session: AsyncSession = Depends(get_session)): ...
"""
from collections.abc import AsyncGenerator

from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine
from sqlalchemy.orm import DeclarativeBase
from sqlalchemy.pool import AsyncQueuePool

from settings import settings

POOL_SIZE = 10
MAX_OVERFLOW = 10
POOL_TIMEOUT = 30
POOL_RECYCLE = 3600        # 연결을 1시간마다 새로 맺는다


class Base(DeclarativeBase):
    pass


engine = create_async_engine(
    settings.mysql_url,
    pool_size=POOL_SIZE,
    max_overflow=MAX_OVERFLOW,
    poolclass=AsyncQueuePool,
    pool_timeout=POOL_TIMEOUT,
    pool_recycle=POOL_RECYCLE,
    pool_pre_ping=True,                 # 끊긴 연결을 쓰기 전에 걸러낸다
    pool_reset_on_return="rollback",
    echo=False,
    connect_args={
        "connect_timeout": 10,
        "read_timeout": 30,
        "write_timeout": 30,
        "charset": "utf8mb4",
        "sql_mode": "STRICT_TRANS_TABLES,NO_ZERO_DATE,NO_ZERO_IN_DATE",
        "init_command": "SET SESSION time_zone = '+00:00'",
    },
)

session_factory = async_sessionmaker(bind=engine, class_=AsyncSession,
                                     expire_on_commit=False, autoflush=False)


async def get_session() -> AsyncGenerator[AsyncSession, None]:
    async with session_factory() as session:
        try:
            yield session
        except Exception:
            await session.rollback()
            raise


async def close_engine() -> None:
    await engine.dispose()