src/shared/rules.ts

@@ -0,0 +1,11 @@
+import _ from 'lodash';
+
+type RuleResult = number | false | undefined;
+
+export const getMinimumRuleOutput = async <T>(
+  rules: ((input: T) => RuleResult | Promise<RuleResult>)[],
+  input: T,
+) => {
+  const results = await Promise.all(rules.map((rule) => rule(input)));
+  return Math.min(..._.compact(results));
+};

src/transaction/transaction.controller.spec.ts

@@ -71,91 +71,55 @@ describe('TransactionController Unit Tests', () => {
 
   it('calling applyRules method minimum result of applied rules should be got', async () => {
     {
-      const result = await transactionController.applyRules(
-        [
-          transactionController.discountRule,
-          transactionController.turnoverRule,
-        ],
-        {
+      const result = await transactionController.applyRules({
         base_amount: 1000,
         client_id: 1,
-        },
-      );
+      });
 
       expect(result).to.eql(5);
     }
 
     {
-      const result = await transactionController.applyRules(
-        [
-          transactionController.discountRule,
-          transactionController.turnoverRule,
-        ],
-        {
+      const result = await transactionController.applyRules({
         base_amount: 1,
         client_id: 1,
-        },
-      );
+      });
 
       expect(result).to.eql(0.05);
     }
 
     {
-      const result = await transactionController.applyRules(
-        [
-          transactionController.discountRule,
-          transactionController.turnoverRule,
-        ],
-        {
+      const result = await transactionController.applyRules({
         base_amount: 1000,
         client_id: 42,
-        },
-      );
+      });
 
       expect(result).to.eql(0.03);
     }
 
     {
-      const result = await transactionController.applyRules(
-        [
-          transactionController.discountRule,
-          transactionController.turnoverRule,
-        ],
-        {
+      const result = await transactionController.applyRules({
         base_amount: 1,
         client_id: 42,
-        },
-      );
+      });
 
       expect(result).to.eql(0.03);
     }
 
     {
-      const result = await transactionController.applyRules(
-        [
-          transactionController.discountRule,
-          transactionController.turnoverRule,
-        ],
-        {
+      const result = await transactionController.applyRules({
         base_amount: 1000,
         client_id: 99,
-        },
-      );
+      });
 
       expect(result).to.eql(0.03);
     }
 
     {
-      const result = await transactionController.applyRules(
-        [
-          transactionController.discountRule,
-          transactionController.turnoverRule,
-        ],
-        {
+      const result = await transactionController.applyRules({
         base_amount: 1,
         client_id: 99,
-        },
-      );
+      });
 
       expect(result).to.eql(0.03);
     }

src/transaction/transaction.controller.ts

@@ -1,5 +1,4 @@
 import { Controller, Post, UsePipes, Body } from '@nestjs/common';
-import _ from 'lodash';
 import {
   ExchangeRateInput,
   ExchangeRateResponse,
@@ -17,6 +16,7 @@ import {
   HighTurnoverDiscount,
 } from './transaction.dto';
 import { Transaction } from './transaction.entity';
+import { getMinimumRuleOutput } from 'src/shared/rules';
 
 type TransactionRuleData = Pick<Transaction, 'base_amount' | 'client_id'>;
 
@@ -33,10 +33,7 @@ export class TransactionController {
     @Body() transactionInput: TransactionInput,
   ): Promise<string> {
     return JSON.stringify({
-      amount:
-        transactionInput.currency !== Currency.EUR
-          ? (await this.getAmountWithExchange(transactionInput)).toFixed(2)
-          : (await this.getAmountWithoutExchange(transactionInput)).toFixed(2),
+      amount: (await this.getCommissionAmount(transactionInput)).toFixed(2),
       currency: Currency.EUR,
     });
   }
@@ -90,19 +87,14 @@ export class TransactionController {
       : commissionAmount;
   }
 
-  async applyRules(
-    rules: ((
-      transactionInput: TransactionRuleData,
-    ) => number | false | undefined | Promise<number | false | undefined>)[],
-    transactionInput: TransactionRuleData,
-  ) {
-    const commissions = await Promise.all(
-      [...rules, this.defaultRule].map((rule) => rule(transactionInput)),
+  async applyRules(transactionInput: TransactionRuleData) {
+    return getMinimumRuleOutput(
+      [this.turnoverRule, this.discountRule, this.defaultRule],
+      transactionInput,
     );
-    return Math.min(..._.compact(commissions));
   }
 
-  getExchangeRate(exchangeRateInput: ExchangeRateInput) {
+  getExchangeRateResponse(exchangeRateInput: ExchangeRateInput) {
     return new Promise<ExchangeRateResponse>((resolve, reject) => {
       try {
         this.exchangeRateService.convertCurrency(exchangeRateInput).subscribe({
@@ -115,11 +107,21 @@ export class TransactionController {
     });
   }
 
-  async getAmountWithExchange(transactionInput: TransactionInput) {
-    const exchangeRateResponse = await this.getExchangeRate({
+  async getExchangeRateIfNeeded(transactionInput: TransactionInput) {
+    if (transactionInput.currency === Currency.EUR) {
+      return 1;
+    }
+
+    const exchangeRateResponse = await this.getExchangeRateResponse({
       date: transactionInput.date,
     });
 
+    return exchangeRateResponse[transactionInput.currency];
+  }
+
+  async getCommissionAmount(transactionInput: TransactionInput) {
+    const exchangeRate = await this.getExchangeRateIfNeeded(transactionInput);
+
     const transactionAmount = parseInt(transactionInput.amount);
     const transactionData = {
       date: transactionInput.date,
@@ -127,53 +129,18 @@ export class TransactionController {
       currency: transactionInput.currency,
       client_id: transactionInput.client_id,
       base_currency: Currency.EUR,
-      base_amount:
-        transactionAmount / exchangeRateResponse[transactionInput.currency],
+      base_amount: transactionAmount / exchangeRate,
     };
 
-    const commissionAmount = this.applyRules(
-      [this.turnoverRule, this.discountRule],
-      transactionData,
-    );
+    const commission = await this.applyRules(transactionData);
 
-    commissionAmount
-      .then((commission) =>
-        this.transactionService.insertOne({
-          ...transactionData,
-          commission,
-        }),
-      )
-      .catch((error) => console.log(error));
-
-    return commissionAmount;
-  }
-
-  async getAmountWithoutExchange(transactionInput: TransactionInput) {
-    const transactionData = {
-      date: transactionInput.date,
-      amount: parseInt(transactionInput.amount),
-      currency: transactionInput.currency,
-      client_id: transactionInput.client_id,
-      base_currency: Currency.EUR,
-      base_amount: parseInt(transactionInput.amount),
-    };
-
-    const commissionAmount = await this.applyRules(
-      [this.turnoverRule, this.discountRule],
-      transactionData,
-    );
-    try {
     this.transactionService
       .insertOne({
         ...transactionData,
-          commission: commissionAmount,
+        commission,
       })
       .catch((error) => console.log(error));
-    } catch (error) {
-      console.log(error);
-      throw error;
-    }
 
-    return commissionAmount;
+    return commission;
   }
 }