from typing import Dict, Optional, Union, Any
from decimal import Decimal
from sqlalchemy.orm import Session
from fastapi import HTTPException
from models.product import Product
from schemas.product import ProductCreate

def validate_product_data(product_data: ProductCreate) -> bool:
    """
    Validate product data before creation.
    
    Args:
        product_data: Product data to validate
        
    Returns:
        bool: True if data is valid, False otherwise
    """
    if not product_data.name or len(product_data.name.strip()) == 0:
        return False
    
    if not product_data.price or product_data.price <= Decimal('0.00'):
        return False
        
    if product_data.quantity and product_data.quantity < 0:
        return False
        
    return True

def check_duplicate_product(db: Session, name: str) -> bool:
    """
    Check if a product with the same name already exists.
    
    Args:
        db: Database session
        name: Product name to check
        
    Returns:
        bool: True if duplicate exists, False otherwise
    """
    existing_product = db.query(Product).filter(Product.name == name).first()
    return bool(existing_product)

def create_product_safely(db: Session, product_data: ProductCreate) -> Union[Product, Dict[str, str]]:
    """
    Create a new product with validation and error handling.
    
    Args:
        db: Database session
        product_data: Product data for creation
        
    Returns:
        Product object if created successfully, error dict otherwise
    """
    if not validate_product_data(product_data):
        raise HTTPException(status_code=400, detail="Invalid product data")

    if check_duplicate_product(db, product_data.name):
        raise HTTPException(status_code=400, detail="Product with this name already exists")

    try:
        db_product = Product(
            name=product_data.name,
            description=product_data.description,
            price=product_data.price,
            quantity=product_data.quantity,
            category_id=product_data.category_id
        )
        
        db.add(db_product)
        db.commit()
        db.refresh(db_product)
        return db_product
        
    except Exception as e:
        db.rollback()
        raise HTTPException(status_code=500, detail=f"Failed to create product: {str(e)}")

def format_product_response(product: Product) -> Dict[str, Any]:
    """
    Format product data for API response.
    
    Args:
        product: Product object to format
        
    Returns:
        Dict containing formatted product data
    """
    return {
        "id": product.id,
        "name": product.name,
        "description": product.description,
        "price": str(product.price),
        "quantity": product.quantity,
        "category_id": product.category_id,
        "created_at": product.created_at.isoformat() if product.created_at else None
    }

def validate_product_update(product_data: Dict[str, Any]) -> bool:
    """
    Validate product data for updates.
    
    Args:
        product_data: Product update data to validate
        
    Returns:
        bool: True if update data is valid, False otherwise
    """
    if "price" in product_data and product_data["price"] <= Decimal('0.00'):
        return False
        
    if "quantity" in product_data and product_data["quantity"] < 0:
        return False
        
    if "name" in product_data and len(product_data["name"].strip()) == 0:
        return False
        
    return True