from sqlalchemy import event
from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine, async_sessionmaker
from sqlalchemy.orm import DeclarativeBase
from app.config import settings

engine = create_async_engine(settings.database_url, echo=False)
SessionLocal = async_sessionmaker(engine, expire_on_commit=False)


# Enable WAL mode so concurrent reads don't block on an open write transaction.
# Also set a generous busy timeout so transient lock contention retries instead
# of immediately raising OperationalError.
@event.listens_for(engine.sync_engine, "connect")
def _set_sqlite_pragmas(dbapi_conn, _record):
    cursor = dbapi_conn.cursor()
    cursor.execute("PRAGMA journal_mode=WAL")
    cursor.execute("PRAGMA busy_timeout=10000")  # 10 s
    cursor.close()


class Base(DeclarativeBase):
    pass


async def get_db() -> AsyncSession:
    async with SessionLocal() as session:
        yield session