"""SQLite engine and session management.

Uses SQLAlchemy async engine with aiosqlite driver.

For tests, pass `test_db_url` via the settings or use a test fixture
to point at an in-memory SQLite database.
"""

import logging

from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine

from app.db.models import Base

logger = logging.getLogger(__name__)

# Default DB path for production
DEFAULT_DB_URL = "sqlite+aiosqlite:///data/slab.db"

_engine: object = None
_session_factory: object = None

_test_url: str | None = None


def set_test_url(url: str) -> None:
    """Override the database URL for testing. Must be called before create_app."""
    global _test_url
    _test_url = url


def get_db_url() -> str:
    """Return the database URL, preferring test URL if set."""
    if _test_url:
        return _test_url
    return DEFAULT_DB_URL


async def init_db() -> None:
    """Initialize the async engine, session factory, and create tables.

    For in-memory SQLite tests, creates tables directly.
    For file-based SQLite, attempts alembic migrations first, falling
    back to direct table creation.
    """
    global _engine, _session_factory

    db_url = get_db_url()
    logger.info("Connecting to %s", db_url)

    _engine = create_async_engine(
        db_url,
        echo=False,
        connect_args={"check_same_thread": False},
    )

    _session_factory = async_sessionmaker(
        _engine,
        class_=AsyncSession,
        expire_on_commit=False,
        autocommit=False,
        autoflush=False,
    )

    # Create all tables (works for both in-memory and file-based)
    async with _engine.begin() as conn:
        await conn.run_sync(Base.metadata.create_all)

    logger.info("Database initialized")


async def close_db_connection() -> None:
    """Dispose of the engine (closes all connections)."""
    global _engine
    if _engine is not None:
        await _engine.dispose()
        _engine = None


async def get_session() -> AsyncSession:
    """Get a database session."""
    if _session_factory is None:
        raise RuntimeError("Database not initialized. Call init_db() first.")
    return _session_factory()