refactor: improved transacion service somewhat (closes #22)

src/shared/reactive.ts

@@ -0,0 +1,34 @@
+import type { Observable } from 'rxjs';
+
+export const promisifyObservable =
+  <TArgs extends any[], TOutput>(f: (...args: TArgs) => Observable<TOutput>) =>
+  (...args: TArgs) =>
+    new Promise<TOutput>((_resolve, _reject) => {
+      let isCalled = false;
+      const resolve = (result: TOutput) => {
+        if (isCalled) {
+          console.log('observable emits more than once');
+          return;
+        }
+
+        _resolve(result);
+      };
+
+      const reject = (error: unknown) => {
+        if (isCalled) {
+          console.log('observable emits more than once');
+          return;
+        }
+
+        _reject(error);
+      };
+
+      try {
+        f(...args).subscribe({
+          next: resolve,
+          error: reject,
+        });
+      } catch (error) {
+        reject(error);
+      }
+    });

src/transaction/transaction.controller.ts

@@ -1,12 +1,11 @@
 import { Controller, Post, UsePipes, Body } from '@nestjs/common';
-import {
-  ExchangeRateInput,
-  ExchangeRateResponse,
-} from 'src/exchange-rate/exchange-rate.dto';
-import { ExchangeRateService } from 'src/exchange-rate/exchange-rate.service';
+import _ from 'lodash';
+import { BodyValidationPipe } from '../pipes/body.validation.pipe';
+import { ExchangeRateService } from '../exchange-rate/exchange-rate.service';
+import { promisifyObservable } from '../shared/reactive';
+import { getMinimumRuleOutput } from '../shared/rules';
 import { TransactionService } from './transaction.service';
 import { transactionBodySchema } from './transaction.validation';
-import { BodyValidationPipe } from '../pipes/body.validation.pipe';
 import {
   Currency,
   TransactionInput,
@@ -16,7 +15,6 @@ import {
   HighTurnoverDiscount,
 } from './transaction.dto';
 import { Transaction } from './transaction.entity';
-import { getMinimumRuleOutput } from 'src/shared/rules';
 
 type TransactionRuleData = Pick<Transaction, 'base_amount' | 'client_id'>;
 
@@ -40,25 +38,15 @@ export class TransactionController {
 
   getClientDeposit = async (transactionInput: TransactionRuleData) => {
     try {
-      const deposit =
-        await this.transactionService.findByClientIdWithinActualMonth(
-          transactionInput.client_id,
-        );
-
-      if (deposit) {
-        const initialDeposit = 0;
-        const totalDeposit = (await deposit).reduce(
-          (prevAmmount, transactionAmmount) =>
-            prevAmmount + transactionAmmount.base_amount,
-          initialDeposit,
-        );
-
-        return totalDeposit;
-      }
+      const existingTransactions = await this.transactionService.findByClientIdWithinActualMonth(
+        transactionInput.client_id,
+      );
+
+      return _.sum(existingTransactions.map(t => t.base_amount));
     } catch (error) {
       console.log(error);
+      return 0;
     }
-    return 0;
   };
 
   turnoverRule = async (transactionInput: TransactionRuleData) => {
@@ -94,18 +82,7 @@ export class TransactionController {
     );
   }
 
-  getExchangeRateResponse(exchangeRateInput: ExchangeRateInput) {
-    return new Promise<ExchangeRateResponse>((resolve, reject) => {
-      try {
-        this.exchangeRateService.convertCurrency(exchangeRateInput).subscribe({
-          next: resolve,
-          error: reject,
-        });
-      } catch (error) {
-        reject(error);
-      }
-    });
-  }
+  getExchangeRateResponse = promisifyObservable(this.exchangeRateService.convertCurrency.bind(this.exchangeRateService));
 
   async getExchangeRateIfNeeded(transactionInput: TransactionInput) {
     if (transactionInput.currency === Currency.EUR) {