"""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 AsyncAdaptedQueuePool

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=AsyncAdaptedQueuePool,
    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,          # asyncmy에는 write_timeout이 없다
        "charset": "utf8mb4",
        # sql_mode는 asyncmy가 따옴표 없이 끼워 넣어 문법 오류가 나므로 여기서 같이 건다
        "init_command": ("SET SESSION time_zone = '+00:00', "
                         "sql_mode = 'STRICT_TRANS_TABLES,NO_ZERO_DATE,NO_ZERO_IN_DATE'"),
    },
)

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 create_missing_tables() -> None:
    """없는 테이블만 만든다. 컬럼이 바뀐 기존 테이블은 건드리지 않는다"""
    async with engine.begin() as connection:
        await connection.run_sync(Base.metadata.create_all)


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