feature #4 - add get exchange rate use case

src/2-business/constants/errorData.ts

@@ -0,0 +1,11 @@
+export interface ErrorData {
+  code: string,
+  message: string,
+  shortMessage: string
+}
+
+export class ExchangeRateError extends Error {
+  constructor (public readonly errorData: ErrorData) {
+    super(errorData.message)
+  }
+}

src/2-business/constants/errors/error.ts

@@ -0,0 +1,7 @@
+import { ErrorData } from '../errorData'
+
+export class ExchangeRateError extends Error {
+  constructor (public readonly errorData: ErrorData) {
+    super(errorData.message)
+  }
+}

src/2-business/constants/errors/exchangeRateList.ts

@@ -0,0 +1,5 @@
+export const exchangeRateNotFoundError = {
+  code: 'EXR-001',
+  message: 'Exchange Rate not found for the base',
+  shortMessage: 'exchangeRateNotFound'
+}

src/2-business/dto/exchangeRate/getExchangeRateInputDto.ts

@@ -0,0 +1,5 @@
+import { CurrencyEnum } from '../../enums/currencyEnum'
+
+export interface GetExchangeRateInputDto {
+  base: CurrencyEnum
+}

src/2-business/useCases/exchangeRate/getExchangeRateUseCase.ts

@@ -0,0 +1,34 @@
+import { IExchangeRateRepository } from '../../repositories/iExchangeRateRepository'
+import { ExchangeRate } from '../../../1-domain/entities/exchangeRate'
+import { GetExchangeRateInputDto } from '../../dto/exchangeRate/getExchangeRateInputDto'
+import { ExchangeRateError } from '../../constants/errorData'
+import { exchangeRateNotFoundError } from '../../constants/errors/exchangeRateList'
+
+export class GetExchangeRateUseCase {
+
+  constructor (
+		private readonly exchangeRateRepository: IExchangeRateRepository
+	) {}
+
+  private logPrefix: string = 'GetExchangeRateUseCase'
+
+  async execute (input: GetExchangeRateInputDto): Promise<ExchangeRate> {
+    console.log(`${this.logPrefix} :: start`)
+    try {
+      const { base } = input
+      const exchangeRate: ExchangeRate = await this.exchangeRateRepository.get(base)
+
+      if (!exchangeRate) {
+        throw new ExchangeRateError(exchangeRateNotFoundError)
+      }
+
+      console.log(`${this.logPrefix} :: end`)
+
+      return exchangeRate
+    } catch (error) {
+      throw error
+    }
+  }
+}
+
+export default GetExchangeRateUseCase

test/unit/2-business/exchangeRate/getExchangeRateUseCase.test.ts

@@ -0,0 +1,61 @@
+import { ExchangeRate } from '../../../../src/1-domain/entities/exchangeRate'
+import { GetExchangeRateUseCase } from '../../../../src/2-business/useCases/exchangeRate/getExchangeRateUseCase'
+import { IExchangeRateRepository } from '../../../../src/2-business/repositories/iExchangeRateRepository'
+import { CurrencyEnum } from '../../../../src/2-business/enums/currencyEnum'
+import { GetExchangeRateInputDto } from '../../../../src/2-business/dto/exchangeRate/getExchangeRateInputDto'
+
+describe('GetExchangeRateUseCase', () => {
+  const exchangeRateMock: ExchangeRate = {
+    baseCurrency: 'BRL',
+    rates: {
+      'AUD': 1.566015,
+      'CAD': 1.560132,
+      'CHF': 1.154727,
+      'CNY': 7.827874,
+      'GBP': 0.882047,
+      'JPY': 132.360679,
+      'USD': 1.23396
+    }
+  }
+
+  const mockInput: GetExchangeRateInputDto = {
+    base: CurrencyEnum.BRL
+  }
+
+  let exchangeRateRepository: IExchangeRateRepository
+
+  const setMocks = () => {
+    exchangeRateRepository = {
+      upsert: jest.fn().mockResolvedValue(null),
+      get: jest.fn().mockResolvedValue(exchangeRateMock)
+    }
+  }
+
+  beforeEach(() => {
+    setMocks()
+  })
+
+  test('Success::should get the exchange rates successfully', async () => {
+    const useCase = new GetExchangeRateUseCase(
+			exchangeRateRepository
+		)
+
+    const output = await useCase.execute(mockInput)
+
+    expect(exchangeRateRepository.get).toHaveBeenCalledWith(CurrencyEnum.BRL)
+    expect(output).toEqual(exchangeRateMock)
+  })
+
+  test('Failure::should throw error when getting exchange fails or not exists', async () => {
+    exchangeRateRepository = {
+      upsert: jest.fn().mockResolvedValue(null),
+      get: jest.fn().mockResolvedValue(null)
+    }
+
+    const useCase = new GetExchangeRateUseCase(
+			exchangeRateRepository
+		)
+
+    await expect(useCase.execute({ base: CurrencyEnum.USD })).rejects.toThrow()
+  })
+})