"""Database configuration and session management."""
import os
from sqlalchemy.ext.asyncio import create_async_engine, async_sessionmaker, AsyncSession
from sqlalchemy.orm import DeclarativeBase

DATABASE_URL = os.getenv("DATABASE_URL", "sqlite+aiosqlite:///./xdl.db")

engine = create_async_engine(DATABASE_URL, echo=False)
async_session = async_sessionmaker(engine, class_=AsyncSession, expire_on_commit=False)


class Base(DeclarativeBase):
    pass


async def get_db():
    async with async_session() as session:
        yield session


async def init_db():
    async with engine.begin() as conn:
        await conn.run_sync(Base.metadata.create_all)
        # Ensure composite index exists on already-created tables (idempotent)
        await conn.execute(
            __import__("sqlalchemy").text(
                "CREATE INDEX IF NOT EXISTS ix_video_url_format_id ON videos (url, format_id)"
            )
        )