"""Shared FastAPI dependencies — the composition root for request-scoped wiring.

Concrete adapters are bound to ports here so routers and services stay
decoupled from infrastructure. Repository/service providers are added in
later steps as the domain grows.
"""

from collections.abc import AsyncIterator
from typing import Annotated

from fastapi import Depends
from sqlalchemy.ext.asyncio import AsyncSession

from app.infrastructure.db import get_sessionmaker


async def get_session() -> AsyncIterator[AsyncSession]:
    """Request-scoped DB session. Commits on success, rolls back on exception."""
    session = get_sessionmaker()()
    try:
        yield session
        await session.commit()
    except Exception:
        await session.rollback()
        raise
    finally:
        await session.close()


SessionDep = Annotated[AsyncSession, Depends(get_session)]