from typing import List, Optional
from sqlalchemy.orm import Session
from models.meal import Meal

def get_available_meals(db: Session, category: Optional[str] = None) -> List[Meal]:
    """
    Retrieve a list of available meals from the database.

    Args:
        db (Session): SQLAlchemy database session.
        category (str, optional): Filter meals by category. Defaults to None.

    Returns:
        List[Meal]: List of available meal objects.
    """
    query = db.query(Meal).filter(Meal.is_available == True)
    if category:
        query = query.filter(Meal.category == category)
    return query.all()

def validate_meal_data(meal_data: dict) -> dict:
    """
    Validate meal data dictionary for required fields and data types.

    Args:
        meal_data (dict): Dictionary containing meal data.

    Returns:
        dict: Validated meal data dictionary.

    Raises:
        ValueError: If required fields are missing or data types are incorrect.
    """
    required_fields = ['name', 'price']
    for field in required_fields:
        if field not in meal_data:
            raise ValueError(f"Missing required field: {field}")

    if not isinstance(meal_data['name'], str):
        raise ValueError("Name must be a string")

    if not isinstance(meal_data['price'], float):
        raise ValueError("Price must be a float")

    return meal_data

def format_meal_price(price: float) -> str:
    """
    Format a meal price as a string with two decimal places.

    Args:
        price (float): The meal price.

    Returns:
        str: Formatted price string.
    """
    return f"{price:.2f}"

def filter_meals_by_price_range(meals: List[Meal], min_price: Optional[float] = None, max_price: Optional[float] = None) -> List[Meal]:
    """
    Filter a list of meals by a specified price range.

    Args:
        meals (List[Meal]): List of meal objects.
        min_price (float, optional): Minimum price for filtering. Defaults to None.
        max_price (float, optional): Maximum price for filtering. Defaults to None.

    Returns:
        List[Meal]: Filtered list of meal objects.
    """
    filtered_meals = []
    for meal in meals:
        if (min_price is None or meal.price >= min_price) and (max_price is None or meal.price <= max_price):
            filtered_meals.append(meal)
    return filtered_meals