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);
+  }
+}