[ts][stock_management-01_base] Add stock management example

examples/typescript/ts-stock_management-01_base/.gitignore

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+node_modules
+coverage

examples/typescript/ts-stock_management-01_base/README.md

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+# Stock management
+
+Code smells:
+- Data class
+- Shotgun surgery
+
+## Setup
+- Install dependencies with `yarn install`
+- Execute test with `yarn test`

examples/typescript/ts-stock_management-01_base/babel.config.js

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+module.exports = {
+  presets: [
+    ['@babel/preset-env', {targets: {node: 'current'}}],
+    '@babel/preset-typescript',
+  ],
+}

examples/typescript/ts-stock_management-01_base/package.json

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+{
+  "name": "step_shotgun_surgery",
+  "version": "1.0.0",
+  "main": "index.js",
+  "license": "MIT",
+  "scripts": {
+    "test": "jest",
+    "test-coverage": "jest --coverage"
+  },
+  "devDependencies": {
+    "@babel/core": "^7.13.15",
+    "@babel/preset-env": "^7.13.15",
+    "@babel/preset-typescript": "^7.13.0",
+    "@types/jest": "^26.0.22",
+    "babel-jest": "^26.6.3",
+    "jest": "^26.6.3",
+    "typescript": "^4.2.4"
+  }
+}

examples/typescript/ts-stock_management-01_base/src/AggregateRoot.ts

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+export class AggregateRoot {
+    private domainEvents: Array<any>
+
+    constructor() {
+        this.domainEvents = []
+    }
+
+    pullDomainEvents(): Array<any> {
+        const domainEvents = this.domainEvents.slice()
+        this.domainEvents = []
+
+        return domainEvents
+    }
+
+    record(event: any): void {
+        this.domainEvents.push(event)
+    }
+}

examples/typescript/ts-stock_management-01_base/src/FlowerStock.ts

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+import { LowStock } from "./LowStock"
+import { AggregateRoot } from "./AggregateRoot"
+import { NotEnoughStock } from "./NotEnoughStock"
+import { OutOfStock } from "./OutOfStock"
+
+export class FlowerStock extends AggregateRoot {
+
+    private flowers: Array<string>
+
+    constructor(flowers: Array<string> = []) {
+        super()
+        const flowerSet = new Set<string>(flowers)
+        this.flowers = Array.from(flowerSet)
+    }
+
+    total() {
+        return this.flowers.length
+    }
+
+    add(flowerId: string): void {
+        const flowerSet = new Set<string>(this.flowers)
+        flowerSet.add(flowerId)
+        this.flowers = Array.from(flowerSet)
+    }
+
+    get(): string {
+        if (this.flowers.length === 0) {
+            throw new OutOfStock()
+        }
+        const currentStock = this.flowers.length
+
+        const flowerId = this.flowers.shift()
+
+        if (currentStock >= 50 && this.flowers.length < 50) {
+            this.record(new LowStock('low flower stock'))
+        }
+
+        return flowerId
+    }
+
+    getMultiple(amount: number): Array<string> {
+        if (this.flowers.length < amount) {
+            throw new NotEnoughStock()
+        }
+
+        const currentStock = this.flowers.length
+
+        const flowerIds: Array<string> = this.flowers.splice(0, amount)
+
+        if (currentStock >= 50 && this.flowers.length < 50) {
+            this.record(new LowStock(`low flower stock produced by high demand: ${amount}`))
+        }
+
+        return flowerIds
+    }
+
+    removeDeadFlowers(deadFlowers: Array<string>): void {
+        const currentStock = this.flowers.length
+
+        this.flowers = this.flowers.filter(flowerId => !deadFlowers.includes(flowerId))
+
+        if (currentStock >= 50 && this.flowers.length < 50) {
+            this.record(new LowStock(`low flower stock produced by ${deadFlowers.length} dead flowers`))
+        }
+    }
+}

examples/typescript/ts-stock_management-01_base/src/LowStock.ts

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+export class LowStock {
+    constructor(public readonly reason: string) {}
+}

examples/typescript/ts-stock_management-01_base/src/NotEnoughStock.ts

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+export class NotEnoughStock extends Error {
+    constructor() {
+        super('Not enough stock')
+    }
+}

examples/typescript/ts-stock_management-01_base/src/OutOfStock.ts

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+export class OutOfStock extends Error {
+    constructor() {
+        super('Out of stock')
+    }
+}

examples/typescript/ts-stock_management-01_base/tests/FlowerStock.test.ts

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+import { FlowerStock } from "../src/FlowerStock"
+import { LowStock } from "../src/LowStock"
+import { NotEnoughStock } from "../src/NotEnoughStock"
+import { OutOfStock } from "../src/OutOfStock"
+
+describe('flower stock management', () => {
+
+    it('should add a flower to the stock', () => {
+        const stockFlowerIds = ['1', '2']
+        const stock = new FlowerStock(stockFlowerIds)
+
+        stock.add('3')
+
+        expect(stock.total()).toBe(3)
+    })
+
+    it('should add the same flower multiple times', () => {
+        const stock = new FlowerStock()
+
+        stock.add('3')
+        stock.add('3')
+
+        expect(stock.total()).toBe(1)
+    })
+
+    it('get a single flower from the stock', () => {
+        const flowerIds = ['1', '2']
+        const stock = new FlowerStock(flowerIds)
+
+        const flowerId = stock.get()
+
+        expect(flowerId).toContain('1')
+        expect(stock.total()).toBe(1)
+    })
+
+    it('should reach low stock when getting a single flower from a stock of 50', () => {
+        const stockFlowerIds = makeFlowerIds(50)
+        const stock = new FlowerStock(stockFlowerIds)
+
+        stock.get()
+
+        const domainEvents = stock.pullDomainEvents()
+        expect(domainEvents.length).toBe(1)
+        const lowStockEvent = domainEvents[0] as LowStock
+        expect(lowStockEvent.reason).toBe('low flower stock')
+    })
+
+    it('should not reach low stock when getting a single flower from a stock greater than 50', () => {
+        const flowerIds = makeFlowerIds(51)
+        const stock = new FlowerStock(flowerIds)
+
+        stock.get()
+
+        expect(stock.pullDomainEvents().length).toBe(0)
+    })
+
+    it('should throw an error when trying to get a single flower from an empty stock', () => {
+        const stock = new FlowerStock()
+
+        expect(() => stock.get()).toThrow(OutOfStock)
+    })
+
+    it('should get multiple flowers from the stock', () => {
+        const stockFlowerIds = ['1', '2', '3']
+        const stock = new FlowerStock(stockFlowerIds)
+
+        const flowerIds = stock.getMultiple(2)
+
+        expect(flowerIds).toEqual(['1', '2'])
+        expect(stock.total()).toBe(1)
+    })
+
+    it('should reach low stock when getting multiple flowers and the limit of 50 is exceeded', () => {
+        const lowStockLevel = 50
+        const unitsToLowStock = 5
+        const unitsToGetFromTheStock = 6
+        const totalStock = lowStockLevel + unitsToLowStock
+        const stockFlowerIds = makeFlowerIds(totalStock)
+        const stock = new FlowerStock(stockFlowerIds)
+
+        stock.getMultiple(unitsToGetFromTheStock)
+
+        const domainEvents = stock.pullDomainEvents()
+        expect(domainEvents.length).toBe(1)
+        const lowStockEvent = domainEvents[0] as LowStock
+        expect(lowStockEvent.reason).toBe('low flower stock produced by high demand: 6')
+    })
+
+    it('should not reach low stock when getting multiple flowers and the limit of 50 is not exceeded', () => {
+        const lowStockLimit = 50
+        const unitsToLowStock = 5
+        const unitsToGetFromTheStock = 5
+        const totalStock = lowStockLimit + unitsToLowStock
+        const flowerIds = makeFlowerIds(totalStock)
+        const stock = new FlowerStock(flowerIds)
+
+        stock.getMultiple(unitsToGetFromTheStock)
+
+        expect(stock.pullDomainEvents().length).toBe(0)
+    })
+
+    it('should get a multiple flowers from an empty stock', () => {
+        const stock = new FlowerStock()
+
+        expect(() => stock.getMultiple(2)).toThrow(NotEnoughStock)
+    })
+
+    it('remove dead flowers from the stock', () => {
+        const stockFlowerIds = ['1', '2', '3']
+        const stock = new FlowerStock(stockFlowerIds)
+
+        const deadFlowerIds = ['1', '3']
+        stock.removeDeadFlowers(deadFlowerIds)
+
+        expect(stock.total()).toBe(1)
+        const aliveFlower = '2'
+        expect(stock.get()).toBe(aliveFlower)
+    })
+
+
+    it('should reach low stock when removing dead flowers and the limit of 50 is exceeded', () => {
+        const lowStockLevel = 50
+        const unitsToLowStock = 5
+        const totalDeadFlowers = 6
+        const totalStock = lowStockLevel + unitsToLowStock
+        const stockFlowerIds = makeFlowerIds(totalStock)
+        const stock = new FlowerStock(stockFlowerIds)
+
+        const deadFlowers = makeFlowerIds(totalDeadFlowers)
+        stock.removeDeadFlowers(deadFlowers)
+
+        const domainEvents = stock.pullDomainEvents()
+        expect(domainEvents.length).toBe(1)
+        const lowStockEvent = domainEvents[0] as LowStock
+        expect(lowStockEvent.reason).toBe('low flower stock produced by 6 dead flowers')
+    })
+
+    it('should not reach low stock when removing flowers and the limit of 50 is not exceeded', () => {
+        const lowStockLimit = 50
+        const unitsToLowStock = 5
+        const totalDeadFlowers = 5
+        const totalStock = lowStockLimit + unitsToLowStock
+        const flowerIds = makeFlowerIds(totalStock)
+        const stock = new FlowerStock(flowerIds)
+
+        const deadFlowers = makeFlowerIds(totalDeadFlowers)
+        stock.removeDeadFlowers(deadFlowers)
+
+        expect(stock.pullDomainEvents().length).toBe(0)
+    })
+
+    function makeFlowerIds(amount: number) {
+        return Array<string>(amount).fill('1').map((x, y) => (x + y) as string)
+    }
+})