refactor: implemented async getExchangeRate method

src/transaction/transaction.controller.ts

@@ -1,4 +1,5 @@
 import { Controller, Post, UsePipes, Body } from '@nestjs/common';
+import { ExchangeRateInput } from 'src/exchange-rate/exchange-rate.dto';
 import { ExchangeRateService } from 'src/exchange-rate/exchange-rate.service';
 import { TransactionService } from './transaction.service';
 import { transactionBodySchema } from './transaction.validation';
@@ -105,6 +106,19 @@ export class TransactionController {
       : this.defaultRule(transactionInput);
   }
 
+  getExchangeRate(exchangeRateInput: ExchangeRateInput) {
+    return new Promise((resolve, reject) => {
+      try {
+        this.exchangeRateService.convertCurrency(exchangeRateInput).subscribe({
+          next: resolve,
+          error: reject,
+        });
+      } catch (error) {
+        reject(error);
+      }
+    });
+  }
+
   getAmountWithExchange(transactionInput: TransactionInput) {
     const commissionAmount = this.applyRules(
       [this.turnoverRule, this.discountRule],
@@ -115,11 +129,9 @@ export class TransactionController {
       date: transactionInput.date,
     };
 
-    try {
-      this.exchangeRateService.convertCurrency(exhangeRateInput).subscribe({
-        next: (exchangeRateResponse) =>
-          commissionAmount
-            .then((commission) =>
+    this.getExchangeRate(exhangeRateInput)
+      .then((exchangeRateResponse) =>
+        commissionAmount.then((commission) =>
           this.transactionService.insertOne({
             date: transactionInput.date,
             amount: parseInt(transactionInput.amount),
@@ -131,15 +143,9 @@ export class TransactionController {
               parseInt(transactionInput.amount) *
               exchangeRateResponse[transactionInput.currency],
           }),
+        ),
       )
-            .catch((error) => console.log(error)),
-        error: (error) => {
-          console.log(error);
-        },
-      });
-    } catch (error) {
-      console.log(error);
-    }
+      .catch((error) => console.log(error));
 
     return commissionAmount;
   }