"""Async SQLAlchemy engine, session factory, and declarative base.

The SQLite database file lives under ./data so it can be persisted via a
Docker volume mount. The data directory is created on import if missing.
"""
import os

from dotenv import load_dotenv
from sqlalchemy.ext.asyncio import (
    AsyncSession,
    async_sessionmaker,
    create_async_engine,
)
from sqlalchemy.orm import DeclarativeBase

load_dotenv()

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


def _ensure_sqlite_dir(url: str) -> None:
    """Make sure the directory holding the SQLite file exists."""
    if "sqlite" not in url:
        return
    # everything after the scheme's :/// is the filesystem path
    if ":///" not in url:
        return
    path = url.split(":///", 1)[1]
    directory = os.path.dirname(path)
    if directory:
        os.makedirs(directory, exist_ok=True)


_ensure_sqlite_dir(DATABASE_URL)


class Base(DeclarativeBase):
    """Declarative base shared by all ORM models."""


engine = create_async_engine(DATABASE_URL, echo=False, future=True)

AsyncSessionLocal = async_sessionmaker(
    engine, class_=AsyncSession, expire_on_commit=False
)


async def get_db() -> AsyncSession:
    """FastAPI dependency that yields a scoped async session."""
    async with AsyncSessionLocal() as session:
        yield session