"""Database engine and session management.

Provides a SQLModel engine factory and a session dependency
for use with FastAPI's dependency injection.
"""

from pathlib import Path
from typing import Generator

import structlog
from sqlmodel import Session, create_engine

logger = structlog.get_logger(__name__)


def get_engine(database_url: str):
    """Create a SQLAlchemy engine for the given database URL.

    For SQLite, ensures the parent directory exists and sets
    appropriate connection arguments.

    Args:
        database_url: SQLAlchemy-compatible connection string.

    Returns:
        A configured SQLAlchemy Engine.
    """
    connect_args = {}
    if database_url.startswith("sqlite"):
        # Ensure the data directory exists
        db_path = database_url.replace("sqlite:///", "")
        if db_path and db_path != ":memory:":
            Path(db_path).parent.mkdir(parents=True, exist_ok=True)
        connect_args = {"check_same_thread": False}

    engine = create_engine(
        database_url,
        connect_args=connect_args,
        echo=False,
    )
    logger.info("database_engine_created", url=database_url)
    return engine


def get_db_session(engine) -> Generator[Session, None, None]:
    """Yield a SQLModel session for dependency injection.

    Usage in FastAPI routes:
        @router.get("/example")
        def example(session: Session = Depends(get_db_session)):
            ...

    Args:
        engine: The SQLAlchemy engine to bind the session to.

    Yields:
        A SQLModel Session that auto-closes after use.
    """
    with Session(engine) as session:
        yield session