Inventory Management System

🎯 Description

This advanced challenge combines object-oriented programming with data management to create a comprehensive inventory system. You'll implement multiple classes that work together to manage products and inventory operations.

🔍 Task

Implement two classes: Product and Inventory that work together to manage a collection of products.

Product Class

Create a Product class with the following specifications:

Constructor

• __init__(self, product_id: int, name: str, price: float, quantity: int)
• Initialize a product with ID, name, price, and quantity
• Should raise ValueError for invalid inputs (negative price/quantity, empty name)

Properties/Methods

• product_id: int - Unique product identifier (read-only)
• name: str - Product name (read-only)
• price: float - Product price (can be updated via setter)
• quantity: int - Available quantity (can be updated via setter)
• total_value() -> float - Returns price × quantity
• __str__() -> str - String representation: "ID: {id}, Name: {name}, Price: ${price:.2f}, Qty: {quantity}"

Inventory Class

Create an Inventory class with the following specifications:

Constructor

• __init__(self) - Initialize empty inventory

Methods

1. add_product(self, product: Product) -> None

   • Add a product to inventory
   • If product ID already exists, raise ValueError

2. remove_product(self, product_id: int) -> bool

   • Remove product from inventory
   • Return True if removed, False if product not found

3. update_stock(self, product_id: int, quantity: int) -> bool

   • Update product quantity (add to existing quantity)
   • Return True if updated, False if product not found
   • Raise ValueError if resulting quantity would be negative

4. get_product(self, product_id: int) -> Product | None

   • Return product object by ID, or None if not found

5. get_total_value(self) -> float

   • Return total value of all products in inventory

6. get_low_stock_products(self, threshold: int = 5) -> list[Product]

   • Return list of products with quantity <= threshold

7. generate_report(self) -> str

   • Return formatted inventory report with all products

📋 Requirements

• Classes must be implemented in Python 3.8+
• Include proper type hints
• Follow PEP 8 style guidelines
• Use appropriate encapsulation (private/protected attributes where needed)
• Implement proper validation for all inputs
• Handle edge cases gracefully

🧪 Test Cases

Your solution must pass the following test cases:

1. Product Class Tests

• Constructor with valid inputs should create product correctly
• Invalid inputs should raise appropriate exceptions
• Properties should be accessible and updateable where appropriate
• total_value() should calculate correctly
• String representation should be formatted correctly

2. Inventory Class Tests

• Empty inventory should be initialized correctly
• Adding products should work for unique IDs
• Adding duplicate product IDs should raise exception
• Removing existing products should return True
• Removing non-existent products should return False

3. Stock Management Tests

• Updating stock should modify quantity correctly
• Stock updates that would result in negative quantity should raise exception
• Getting products by ID should work correctly
• Getting non-existent products should return None

4. Reporting Tests

• Total value calculation should be accurate
• Low stock detection should work with default and custom thresholds
• Inventory report should be properly formatted

5. Edge Cases

• Empty inventory operations should handle gracefully
• Large quantities and prices should be handled correctly
• Multiple operations in sequence should maintain data integrity

📁 Files

• solution.py - Implement your solution here
• test_main.py - Contains the test cases DO NOT EDIT

✅ Submission

1. Implement your solution in solution.py
2. Push your changes to your repository
3. The automated tests will run and verify your solution

💡 Tips

• Use properties and setters to control access to attributes
• Consider using a dictionary to store products in the inventory (with product_id as key)
• Validate inputs in constructors and methods
• Think about when to raise exceptions vs. return error indicators
• Use list comprehensions for filtering operations like low stock detection
• Format monetary values appropriately in string representations