Walkthrough: parking lot

1 // Sizing and Entity Types
2 const SpotType = { MOTORCYCLE: "MOTORCYCLE", COMPACT: "COMPACT", LARGE: "LARGE" };
3 
4 class Vehicle {
5   constructor(plate, type) {
6     this.plate = plate;
7     this.type = type;
8   }
9 }
10 
11 class ParkingSpot {
12   #vehicle = null;
13   constructor(id, floorNumber, spotType) {
14     this.id = id;
15     this.floorNumber = floorNumber;
16     this.spotType = spotType;
17   }
18 
19   canFit(vehicle) {
20     if (this.#vehicle !== null) return false;
21     if (vehicle.type === SpotType.MOTORCYCLE) return true;
22     if (vehicle.type === SpotType.COMPACT) {
23       return this.spotType === SpotType.COMPACT || this.spotType === SpotType.LARGE;
24     }
25     return this.spotType === SpotType.LARGE;
26   }
27 
28   assign(vehicle) {
29     if (!this.canFit(vehicle)) throw new Error("Spot cannot accommodate vehicle");
30     this.#vehicle = vehicle;
31   }
32 
33   vacate() { this.#vehicle = null; }
34   get isOccupied() { return this.#vehicle !== null; }
35 }
36 
37 class ParkingTicket {
38   constructor(id, vehiclePlate, spot) {
39     this.id = id;
40     this.vehiclePlate = vehiclePlate;
41     this.spot = spot;
42     this.entryTime = Date.now();
43   }
44 }
45 
46 // Strategy: Hourly fee calculation
47 class FlatRatePricingStrategy {
48   calculate(ticket, exitTime) {
49     const hours = Math.max(1, Math.ceil((exitTime - ticket.entryTime) / (1000 * 60 * 60)));
50     return hours * 10.0; // $10/hour
51   }
52 }
53 
54 // Parking Lot Coordinator
55 class ParkingLot {
56   #spots = [];
57   #activeTickets = new Map();
58   #pricingStrategy;
59 
60   constructor(spots, pricingStrategy = new FlatRatePricingStrategy()) {
61     this.#spots = spots;
62     this.#pricingStrategy = pricingStrategy;
63   }
64 
65   park(vehicle) {
66     const availableSpot = this.#spots.find((s) => s.canFit(vehicle));
67     if (!availableSpot) throw new Error("Parking full for " + vehicle.type);
68 
69     availableSpot.assign(vehicle);
70     const ticket = new ParkingTicket(`TKT-${Date.now()}`, vehicle.plate, availableSpot);
71     this.#activeTickets.set(ticket.id, ticket);
72     return ticket;
73   }
74 
75   unpark(ticketId, exitTime = Date.now()) {
76     const ticket = this.#activeTickets.get(ticketId);
77     if (!ticket) throw new Error("Invalid ticket ID");
78 
79     const fee = this.#pricingStrategy.calculate(ticket, exitTime);
80     ticket.spot.vacate();
81     this.#activeTickets.delete(ticketId);
82     return { fee, vehiclePlate: ticket.vehiclePlate };
83   }
84 }
85 
86 // Verification Test
87 const spots = [
88   new ParkingSpot("F1-01", 1, SpotType.COMPACT),
89   new ParkingSpot("F1-02", 1, SpotType.LARGE)
90 ];
91 const lot = new ParkingLot(spots);
92 
93 const car = new Vehicle("KA-05-AB-1234", SpotType.COMPACT);
94 const ticket = lot.park(car);
95 console.assert(spots[0].isOccupied === true);
96 
97 // Unpark after 2 hours simulated:
98 const receipt = lot.unpark(ticket.id, ticket.entryTime + 2 * 3600 * 1000);
99 console.assert(receipt.fee === 20.0);
100 console.assert(spots[0].isOccupied === false);
101 console.log("Unparked successfully. Receipt fee:", receipt.fee);

1 public class Example {
2   enum SpotType { MOTORCYCLE, COMPACT, LARGE }
3   record Vehicle(String plate, SpotType type) {}
4 
5   static final class ParkingSpot {
6     final String id;
7     final SpotType type;
8     private Vehicle vehicle;
9 
10     ParkingSpot(String id,