"""
Database configuration and session management using SQLAlchemy async.
"""

from typing import AsyncGenerator

from sqlalchemy import MetaData
from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker

from app.config import settings

# Create async engine
engine = create_async_engine(
    settings.DATABASE_URL,
    echo=settings.DEBUG,
    future=True,
)

# Create async session factory
async_session_maker = sessionmaker(
    engine,
    class_=AsyncSession,
    expire_on_commit=False,
    autocommit=False,
    autoflush=False,
)

# Naming convention for constraints (for Alembic)
convention = {
    "ix": "ix_%(column_0_label)s",
    "uq": "uq_%(table_name)s_%(column_0_name)s",
    "ck": "ck_%(table_name)s_%(constraint_name)s",
    "fk": "fk_%(table_name)s_%(column_0_name)s_%(referred_table_name)s",
    "pk": "pk_%(table_name)s",
}

metadata = MetaData(naming_convention=convention)

# Base class for all models
Base = declarative_base(metadata=metadata)


async def get_db() -> AsyncGenerator[AsyncSession, None]:
    """
    Dependency to get database session.

    Usage:
        @app.get("/users")
        async def get_users(db: AsyncSession = Depends(get_db)):
            ...

    Yields:
        AsyncSession instance
    """
    async with async_session_maker() as session:
        try:
            yield session
        finally:
            await session.close()