"""Async SQLAlchemy engine, session factory, get_db dependency."""
from collections.abc import AsyncGenerator
from datetime import datetime
from uuid import uuid4

from sqlalchemy import DateTime, String, func
from sqlalchemy.ext.asyncio import (
    AsyncSession,
    async_sessionmaker,
    create_async_engine,
)
from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column

from app.config import settings

engine = create_async_engine(
    settings.database_url,
    echo=settings.app_env != "production",
    pool_pre_ping=True,
    pool_recycle=3600,
    pool_size=10,
    max_overflow=20,
)

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


class Base(DeclarativeBase):
    """Tüm ORM modelleri bundan miras alır."""


def gen_uuid() -> str:
    return str(uuid4())


class UUIDMixin:
    id: Mapped[str] = mapped_column(String(36), primary_key=True, default=gen_uuid)


class TimestampMixin:
    created_at: Mapped[datetime] = mapped_column(
        DateTime, server_default=func.now(), nullable=False
    )
    updated_at: Mapped[datetime] = mapped_column(
        DateTime, server_default=func.now(), onupdate=func.now(), nullable=False
    )


async def get_db() -> AsyncGenerator[AsyncSession, None]:
    """FastAPI dependency — request başına bir session."""
    async with AsyncSessionFactory() as session:
        try:
            yield session
        except Exception:
            await session.rollback()
            raise