feat: get latest exchange rate from third party services

packages/server/src/lib/ExchangeRate/ExchangeRate.ts

@@ -0,0 +1,45 @@
+import { OpenExchangeRate } from './OpenExchangeRate';
+import { ExchangeRateServiceType, IExchangeRateService } from './types';
+
+export class ExchangeRate {
+  private exchangeRateService: IExchangeRateService;
+  private exchangeRateServiceType: ExchangeRateServiceType;
+
+  /**
+   * Constructor method.
+   * @param {ExchangeRateServiceType} service
+   */
+  constructor(service: ExchangeRateServiceType) {
+    this.exchangeRateServiceType = service;
+    this.initService();
+  }
+
+  /**
+   * Initialize the exchange rate service based on the service type.
+   */
+  private initService() {
+    if (
+      this.exchangeRateServiceType === ExchangeRateServiceType.OpenExchangeRate
+    ) {
+      this.setExchangeRateService(new OpenExchangeRate());
+    }
+  }
+
+  /**
+   * Sets the exchange rate service.
+   * @param {IExchangeRateService} service
+   */
+  private setExchangeRateService(service: IExchangeRateService) {
+    this.exchangeRateService = service;
+  }
+
+  /**
+   * Gets the latest exchange rate.
+   * @param {string} baseCurrency
+   * @param {string} toCurrency
+   * @returns {number}
+   */
+  public latest(baseCurrency: string, toCurrency: string): Promise<number> {
+    return this.exchangeRateService.latest(baseCurrency, toCurrency);
+  }
+}

packages/server/src/lib/ExchangeRate/OpenExchangeRate.ts

@@ -0,0 +1,62 @@
+import Axios, { AxiosError } from 'axios';
+import {
+  EchangeRateErrors,
+  IExchangeRateService,
+  OPEN_EXCHANGE_RATE_LATEST_URL,
+} from './types';
+import config from '@/config';
+import { ServiceError } from '@/exceptions';
+
+export class OpenExchangeRate implements IExchangeRateService {
+  /**
+   * Gets the latest exchange rate.
+   * @param {string} baseCurrency
+   * @param {string} toCurrency
+   * @returns {Promise<number}
+   */
+  public async latest(
+    baseCurrency: string,
+    toCurrency: string
+  ): Promise<number> {
+    try {
+      const result = await Axios.get(OPEN_EXCHANGE_RATE_LATEST_URL, {
+        params: {
+          app_id: config.exchangeRate.openExchangeRate.appId,
+          base: baseCurrency,
+          symbols: toCurrency,
+        },
+      });
+      return result.data.rates[toCurrency] || (1 as number);
+    } catch (error) {
+      this.handleLatestErrors(error);
+    }
+  }
+
+  /**
+   * Handles the latest errors.
+   * @param {any} error
+   */
+  private handleLatestErrors(error: any) {
+    if (error.response.data?.message === 'missing_app_id') {
+      throw new ServiceError(
+        EchangeRateErrors.EX_RATE_SERVICE_API_KEY_REQUIRED,
+        'Invalid App ID provided. Please sign up at https://openexchangerates.org/signup, or contact support@openexchangerates.org.'
+      );
+    } else if (error.response.data?.message === 'invalid_app_id') {
+      throw new ServiceError(
+        EchangeRateErrors.EX_RATE_SERVICE_API_KEY_REQUIRED,
+        'Invalid App ID provided. Please sign up at https://openexchangerates.org/signup, or contact support@openexchangerates.org.'
+      );
+    } else if (error.response.data?.message === 'not_allowed') {
+      throw new ServiceError(
+        EchangeRateErrors.EX_RATE_SERVICE_NOT_ALLOWED,
+        'Getting the exchange rate from the given base currency to the given currency is not allowed.'
+      );
+    } else if (error.response.data?.message === 'invalid_base') {
+      throw new ServiceError(
+        EchangeRateErrors.EX_RATE_INVALID_BASE_CURRENCY,
+        'The given base currency is invalid.'
+      );
+    }
+  }
+}

packages/server/src/lib/ExchangeRate/types.ts

@@ -0,0 +1,17 @@
+export interface IExchangeRateService {
+  latest(baseCurrency: string, toCurrency: string): Promise<number>;
+}
+
+export enum ExchangeRateServiceType {
+  OpenExchangeRate = 'OpenExchangeRate',
+}
+
+export enum EchangeRateErrors {
+  EX_RATE_SERVICE_NOT_ALLOWED = 'EX_RATE_SERVICE_NOT_ALLOWED',
+  EX_RATE_LIMIT_EXCEEDED = 'EX_RATE_LIMIT_EXCEEDED',
+  EX_RATE_SERVICE_API_KEY_REQUIRED = 'EX_RATE_SERVICE_API_KEY_REQUIRED',
+  EX_RATE_INVALID_BASE_CURRENCY = 'EX_RATE_INVALID_BASE_CURRENCY',
+}
+
+export const OPEN_EXCHANGE_RATE_LATEST_URL =
+  'https://openexchangerates.org/api/latest.json';