Requirements

Functional Requirements:

• Assign first-fitting spot - On arrival, find the earliest free spot that can fit the vehicle size across floors.
• Issue ticket on entry - Generate unique ticket with vehicle, spot, and entry time.
• Compute fee on exit - Calculate duration and apply active PricingStrategy.
• Lot full handling - If no suitable spot exists, indicate 'Lot Full'.

Core Objects & Relationships

Entities:

1. Vehicle: Represents a vehicle that uses the system.
2. Ticket: Represents a ticket that gets issued upon entry.
3. Pricing: Represents a concrete payment strategy for charging a ticket.
4. ParkingLot: Represents the physical layout of the system.
5. ParkingSpot: Represents a spot to be used by a vehicle.
6. ParkingFloor: Represents a floor on a parking lot.
7. CheckoutService: Represents the system in charging an amount with a strategy.

Relationships:

• A ParkingSpot can store at most one Vehicle of the correct size.
• A Ticket gets issued for one Vehicle and one ParkingSpot.
• A ParkingLot is composed of several ParkingFloors.
• A ParkingFloor is composed of several ParkingSpots.
• A CheckoutSystem charges an amount with a PaymentStrategy.

APIs & Class Members

Interfaces and class methods:

• PricingStrategy (interface): Defines the contract for objects that can charge an amount.
  • processPayment(amount): charges an amount.

• Vehicle Class:
  • getSize(): retrieves the size of the vehicle.
• Ticket Class:
  • computeFee(): computes the fee based on parking duration.
• ParkingLot:
  • assignParkingSpot(vehicle): assigns a parking spot to a vehicle if it fits and there is enough capacity.
  • getAvailableSpots(): retrieves the number of available spots across the whole parking lot.
• ParkingFloor:
  • getFirstAvailableSpot(vehicle): retrieves the first available parking spot that suits the bgiven vehicle.
  • getAvailableSpots(): retrieves the number of free spots in this floor.
• ParkingSpot:
  • isEmpty(): verifies if the parking spot is free or occupied.
  • doesItFit(vehicle): checks if a vehicle fits in the spot.
  • occupy(vehicle): assigns a vehicle to the parking spot.
• CheckoutService:
  • pay(amount): charges the amount with the class' injected payment strategy.

Deep Dive

• I want to use lists as containers because of the methods already implemented in the standard libraries.
• The parkinglot is an independent entity from the parking lot service, so I model the relationship as aggregation. ParkingLotService has a ParkingLot, but their lifespans are independent.