Added Decorator design pattern

Author: Mayur Kadam

05 - Low Level Design/03 - TypeScript Design Pattern/Structural Design Patterns/Proxy/Decorator/Vehicle System/Base/BaseBike.ts

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+import { Vehicle } from "../Vehicle";
+
+export class BaseBike implements Vehicle {
+    getDescription(): string {
+        return "Base Bike";
+    }
+
+    getCost(): number {
+        return 100000; // Base price
+    }
+}

05 - Low Level Design/03 - TypeScript Design Pattern/Structural Design Patterns/Proxy/Decorator/Vehicle System/Base/BaseCar.ts

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+import { Vehicle } from "../Vehicle";
+
+export class BaseCar implements Vehicle {
+    getDescription(): string {
+        return "Base Car";
+    }
+
+    getCost(): number {
+        return 500000; // Base price
+    }
+}

05 - Low Level Design/03 - TypeScript Design Pattern/Structural Design Patterns/Proxy/Decorator/Vehicle System/Decorators/VehicleDecorator.ts

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+import { Vehicle } from "../Vehicle";
+
+export class VehicleDecorator implements Vehicle {
+    decoratedVehicle: Vehicle;
+
+    constructor(decoratedVehicle: Vehicle) {
+        this.decoratedVehicle = decoratedVehicle;
+    }
+
+    getCost(): number {
+        return this.decoratedVehicle.getCost();
+    }
+    getDescription(): string {
+        return this.decoratedVehicle.getDescription();
+    }
+}

05 - Low Level Design/03 - TypeScript Design Pattern/Structural Design Patterns/Proxy/Decorator/Vehicle System/Features/GPS.ts

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+import { VehicleDecorator } from "../Decorators/VehicleDecorator";
+
+export class GPS extends VehicleDecorator {
+    getDescription(): string {
+        return `${this.decoratedVehicle.getDescription()}, GPS`;
+    }
+
+    getCost(): number {
+        return this.decoratedVehicle.getCost() + 30000;
+    }
+}

05 - Low Level Design/03 - TypeScript Design Pattern/Structural Design Patterns/Proxy/Decorator/Vehicle System/Features/SportsMode.ts

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+import { VehicleDecorator } from "../Decorators/VehicleDecorator";
+
+export class SportsMode extends VehicleDecorator {
+    getDescription(): string {
+        return `${this.decoratedVehicle.getDescription()}, Sport Mode.`;
+    }
+
+    getCost(): number {
+        return this.decoratedVehicle.getCost() + 70000;
+    }
+}

05 - Low Level Design/03 - TypeScript Design Pattern/Structural Design Patterns/Proxy/Decorator/Vehicle System/Features/Sunroof.ts

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+import { VehicleDecorator } from "../Decorators/VehicleDecorator";
+
+export class Sunroof extends VehicleDecorator {
+    getDescription(): string {
+        return `${this.decoratedVehicle.getDescription()}, Sunroof`;
+    }
+
+    getCost(): number {
+        return this.decoratedVehicle.getCost() + 50000;
+    }
+}

05 - Low Level Design/03 - TypeScript Design Pattern/Structural Design Patterns/Proxy/Decorator/Vehicle System/Vehicle.ts

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+export interface Vehicle {
+    getDescription(): string;
+    getCost(): number;
+}

05 - Low Level Design/03 - TypeScript Design Pattern/Structural Design Patterns/Proxy/Decorator/Vehicle System/index.ts

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+import { BaseBike } from "./Base/BaseBike";
+import { BaseCar } from "./Base/BaseCar";
+import { GPS } from "./Features/GPS";
+import { SportsMode } from "./Features/SportsMode";
+import { Sunroof } from "./Features/Sunroof";
+
+
+// CAR
+let myCar = new BaseCar();
+
+console.log(`${myCar.getDescription()} costs ₹${myCar.getCost()}`);
+console.log();
+
+myCar = new GPS(myCar);
+console.log(`${myCar.getDescription()} costs ₹${myCar.getCost()}`);
+console.log();
+
+myCar = new Sunroof(myCar);
+console.log(`${myCar.getDescription()} costs ₹${myCar.getCost()}`);
+console.log();
+
+myCar = new SportsMode(myCar);
+console.log(`${myCar.getDescription()} costs ₹${myCar.getCost()}`);
+console.log();
+
+// BIKE
+let myBike = new BaseBike();
+console.log(`${myBike.getDescription()} costs ₹${myBike.getCost()}`);
+console.log();
+
+myBike = new GPS(myBike);
+console.log(`${myBike.getDescription()} costs ₹${myBike.getCost()}`);
+console.log();
+
+myBike = new SportsMode(myBike);
+console.log(`${myBike.getDescription()} costs ₹${myBike.getCost()}`);
+console.log();