"""
Database Configuration and Session Management

Provides database initialization, session management, and base models
following the Python Quick Start Guide best practices.
"""

from flask_sqlalchemy import SQLAlchemy
from typing import Generator
from sqlalchemy.orm import Session

# Database instance
db = SQLAlchemy()


def init_db(app) -> None:
    """
    Initialize database with Flask app.

    Args:
        app: Flask application instance
    """
    db.init_app(app)


def get_db_session() -> Session:
    """
    Get current database session.

    Returns:
        SQLAlchemy session instance

    Note:
        This is a Flask-SQLAlchemy session, managed automatically.
        Use db.session throughout the application.
    """
    return db.session


# For FastAPI-style dependency injection (if migrating to FastAPI later)
def get_db() -> Generator[Session, None, None]:
    """
    Get database session for dependency injection.

    Yields:
        Database session

    Usage:
        def some_function(db: Session = Depends(get_db)):
            # Use db session
    """
    try:
        yield db.session
    finally:
        # Flask-SQLAlchemy handles cleanup automatically
        pass