from typing import List, Optional
from fastapi import HTTPException, status, Depends
from sqlalchemy.ext.asyncio import AsyncSession
from app.models.menu import MenuItem, Category
from ..db.crud import (
    get_menu_items,
    get_menu_item_by_id,
    create_menu_item_db,
    update_menu_item_db,
    delete_menu_item_db,
    get_categories_db
)
from ..db.database import get_db

class MenuService:
    def __init__(self, db: AsyncSession = Depends(get_db)):
        self.db = db

    async def get_menu_items(self) -> List[MenuItem]:
        """Get all menu items."""
        try:
            menu_items = await get_menu_items(self.db)
            if not menu_items:
                return []
            return menu_items
        except Exception as e:
            raise HTTPException(
                status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
                detail=f"Failed to fetch menu items: {str(e)}"
            )

    async def create_menu_item(self, item: MenuItem) -> MenuItem:
        """Create a new menu item."""
        await self.validate_menu_item(item)
        try:
            return await create_menu_item_db(self.db, item)
        except Exception as e:
            raise HTTPException(
                status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
                detail=f"Failed to create menu item: {str(e)}"
            )

    async def update_menu_item(self, item_id: int, item: MenuItem) -> Optional[MenuItem]:
        """Update an existing menu item."""
        await self.validate_menu_item(item)
        existing_item = await get_menu_item_by_id(self.db, item_id)
        if not existing_item:
            raise HTTPException(
                status_code=status.HTTP_404_NOT_FOUND,
                detail="Menu item not found"
            )
        
        try:
            updated_item = await update_menu_item_db(self.db, item_id, item)
            return updated_item
        except Exception as e:
            raise HTTPException(
                status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
                detail=f"Failed to update menu item: {str(e)}"
            )

    async def delete_menu_item(self, item_id: int) -> bool:
        """Delete a menu item."""
        existing_item = await get_menu_item_by_id(self.db, item_id)
        if not existing_item:
            raise HTTPException(
                status_code=status.HTTP_404_NOT_FOUND,
                detail="Menu item not found"
            )
        
        try:
            success = await delete_menu_item_db(self.db, item_id)
            return success
        except Exception as e:
            raise HTTPException(
                status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
                detail=f"Failed to delete menu item: {str(e)}"
            )

    async def get_categories(self) -> List[Category]:
        """Get all menu categories.
        
        Returns:
            List[Category]: List of all available categories
            
        Raises:
            HTTPException: If there's a database error
        """
        try:
            categories = await get_categories_db(self.db)
            if not categories:
                return []
            return categories
        except Exception as e:
            raise HTTPException(
                status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
                detail=f"Failed to fetch categories: {str(e)}"
            )

    async def validate_menu_item(self, item: MenuItem) -> None:
        """Validate menu item data.
        
        Args:
            item (MenuItem): The menu item to validate
            
        Raises:
            HTTPException: If validation fails
        """
        if not item:
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail="Menu item cannot be null"
            )
        
        if item.price <= 0:
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail="Price must be greater than zero"
            )
        
        if not item.name.strip():
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail="Item name cannot be empty"
            )
        
        if not item.category_id:
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail="Category ID is required"
            )
            
        if item.description and len(item.description) > 500:
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail="Description is too long (max 500 characters)"
            )