Requirements

Functional Requirements:

• Allow users to select a product by entering its product code, displaying the product name and price.
• Enable the machine to accept payment via multiple methods, including coins, cash bills, and credit/debit cards through a unified PaymentStrategy interface.
• Support the dispensing of the selected product after successful payment, decrementing inventory and handling mechanical jams with a refund.
• Calculate and return correct change for cash and coin payments, notifying the user if exact change cannot be provided.
• Store a real-time count of each product to track inventory, verify stock before accepting payment, and support restocking via an admin interface.

Non-Functional Requirements:

• We should consider that many product might be added in the future.
• Another type of payment can be introduced in the future.
• No need for thread safety ad the vending machine is atomic by design (physically)
• in this case there is a single vending machine, there will be other? in that case we should update the system to be thread safe and manage the inventory correctly

Core Objects & Relationships

Product -> descirbe the object being sell at the vending machine

Sale -> rapresent the sale of a product: contains info about the payment and the product

Payment -> rapresent the entity of the payment: contains what ind of payment, what fee had to be paid , what object has been bought.

PaymentStrategy [interface] -> what kind of payment : card, coin, cash bill

VendingMachine: contains the products under the inventory class and manage the transactions.

VendingMachineState: describe the actual status of the vendingmachine

Inventory: contains the inventory of each product and manage their status basign on the available quantity

InventoryProductStatus : described the status of inventory of specific product..

APIs & Class Members

For each class, define the attributes (data) it will hold and the methods (functions) that operate on the attributes. Ensure they align with the object's responsibilities and adhere to the principle of encapsulation. Write your code in the code editor below.

Deep Dive

Explain design tradeoffs you considered. Check and explain whether your design adheres to SOLID principles. Explain how your design can handle changes in scale and whether it would be easy to extend with new functionalities. Identify areas for future improvement...