from typing import List, Dict, Optional
from pydantic import BaseModel, validator

class FoodItem(BaseModel):
    name: str
    description: Optional[str] = None
    price: float
    category: str
    is_vegetarian: bool = False
    is_vegan: bool = False

    @validator('name')
    def name_must_not_be_blank(cls, value):
        if not value.strip():
            raise ValueError('Food item name cannot be blank')
        return value

    @validator('price')
    def price_must_be_positive(cls, value):
        if value <= 0:
            raise ValueError('Price must be a positive value')
        return value

class Menu(BaseModel):
    items: List[FoodItem]

    @validator('items')
    def items_must_not_be_empty(cls, value):
        if not value:
            raise ValueError('Menu must contain at least one food item')
        return value

def validate_food_item(food_item: FoodItem) -> Dict[str, str]:
    errors = {}
    if not food_item.name.strip():
        errors['name'] = 'Food item name cannot be blank'
    if food_item.price <= 0:
        errors['price'] = 'Price must be a positive value'
    return errors

def validate_menu(menu: Menu) -> Dict[str, str]:
    errors = {}
    if not menu.items:
        errors['items'] = 'Menu must contain at least one food item'
    for item in menu.items:
        item_errors = validate_food_item(item)
        if item_errors:
            errors[item.name] = item_errors
    return errors

def create_menu_categories(menu: Menu) -> Dict[str, List[FoodItem]]:
    categories = {}
    for item in menu.items:
        category = item.category
        if category not in categories:
            categories[category] = []
        categories[category].append(item)
    return categories

def get_vegetarian_menu(menu: Menu) -> List[FoodItem]:
    return [item for item in menu.items if item.is_vegetarian]

def get_vegan_menu(menu: Menu) -> List[FoodItem]:
    return [item for item in menu.items if item.is_vegan]