incomplete work during interview

src/shared/reactive.ts

@@ -4,7 +4,7 @@ export const promisifyObservable =
   <TArgs extends any[], TOutput>(f: (...args: TArgs) => Observable<TOutput>) =>
   (...args: TArgs) =>
     new Promise<TOutput>((_resolve, _reject) => {
-      let isCalled = false;
+      const isCalled = false;
       const resolve = (result: TOutput) => {
         if (isCalled) {
           console.log('observable emits more than once');

src/shared/rules.ts

@@ -6,6 +6,15 @@ 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));
+  const results = await Promise.all(
+    rules.map(async (rule) => {
+      const result = await rule(input);
+      if (result === undefined || result === false) {
+        return null;
+      }
+
+      return { commission: result };
+    }),
+  );
+  return Math.min(..._.compact(results).map(({ commission }) => commission));
 };

src/transaction/transaction.controller.spec.ts

@@ -72,6 +72,7 @@ describe('TransactionController Unit Tests', () => {
   it('calling applyRules method minimum result of applied rules should be got', async () => {
     {
       const result = await transactionController.applyRules({
+        date: '2021-01-05',
         base_amount: 1000,
         client_id: 1,
       });
@@ -81,6 +82,7 @@ describe('TransactionController Unit Tests', () => {
 
     {
       const result = await transactionController.applyRules({
+        date: '2021-01-05',
         base_amount: 1,
         client_id: 1,
       });
@@ -90,6 +92,37 @@ describe('TransactionController Unit Tests', () => {
 
     {
       const result = await transactionController.applyRules({
+        date: '2021-01-01',
+        base_amount: 1,
+        client_id: 1,
+      });
+
+      expect(result).to.eql(0);
+    }
+
+    {
+      const result = await transactionController.applyRules({
+        date: '2021-01-05',
+        base_amount: 1000,
+        client_id: 20,
+      });
+
+      expect(result).to.eql(0.01);
+    }
+
+    {
+      const result = await transactionController.applyRules({
+        date: '2021-01-05',
+        base_amount: 1,
+        client_id: 20,
+      });
+
+      expect(result).to.eql(0.01);
+    }
+
+    {
+      const result = await transactionController.applyRules({
+        date: '2021-01-05',
         base_amount: 1000,
         client_id: 42,
       });
@@ -99,6 +132,7 @@ describe('TransactionController Unit Tests', () => {
 
     {
       const result = await transactionController.applyRules({
+        date: '2021-01-05',
         base_amount: 1,
         client_id: 42,
       });
@@ -108,6 +142,7 @@ describe('TransactionController Unit Tests', () => {
 
     {
       const result = await transactionController.applyRules({
+        date: '2021-01-05',
         base_amount: 1000,
         client_id: 99,
       });
@@ -117,6 +152,7 @@ describe('TransactionController Unit Tests', () => {
 
     {
       const result = await transactionController.applyRules({
+        date: '2021-01-05',
         base_amount: 1,
         client_id: 99,
       });

src/transaction/transaction.controller.ts

@@ -1,5 +1,5 @@
 import { Controller, Post, UsePipes, Body } from '@nestjs/common';
-import _ from 'lodash';
+import _, { endsWith } from 'lodash';
 import { BodyValidationPipe } from '../pipes/body.validation.pipe';
 import { ExchangeRateService } from '../exchange-rate/exchange-rate.service';
 import { promisifyObservable } from '../shared/reactive';
@@ -9,14 +9,14 @@ import { transactionBodySchema } from './transaction.validation';
 import {
   Currency,
   TransactionInput,
-  DiscountRuleForClientById,
   DefaultCommissionPercentage,
   DefaultCommissionAmount,
   HighTurnoverDiscount,
+  DISCOUNTED_COMMISSIONS,
 } from './transaction.dto';
 import { Transaction } from './transaction.entity';
 
-type TransactionRuleData = Pick<Transaction, 'base_amount' | 'client_id'>;
+type TransactionRuleData = Pick<Transaction, 'base_amount' | 'client_id' | 'date'>;
 
 @Controller('transaction')
 export class TransactionController {
@@ -38,11 +38,12 @@ export class TransactionController {
 
   getClientDeposit = async (transactionInput: TransactionRuleData) => {
     try {
-      const existingTransactions = await this.transactionService.findByClientIdWithinActualMonth(
-        transactionInput.client_id,
-      );
+      const existingTransactions =
+        await this.transactionService.findByClientIdWithinActualMonth(
+          transactionInput.client_id,
+        );
 
-      return _.sum(existingTransactions.map(t => t.base_amount));
+      return _.sum(existingTransactions.map((t) => t.base_amount));
     } catch (error) {
       console.log(error);
       return 0;
@@ -61,8 +62,8 @@ export class TransactionController {
   };
 
   discountRule(transactionInput: TransactionRuleData) {
-    return transactionInput.client_id === 42
-      ? DiscountRuleForClientById.client_42
+    return DISCOUNTED_COMMISSIONS.has(transactionInput.client_id)
+      ? DISCOUNTED_COMMISSIONS.get(transactionInput.client_id)
       : false;
   }
 
@@ -75,14 +76,24 @@ export class TransactionController {
       : commissionAmount;
   }
 
+  firstDayOfMonthFreeRule(transactionInput: TransactionRuleData) {
+    if (transactionInput.date.endsWith('-01')) {
+      return 0;
+    }
+
+    return undefined;
+  }
+
   async applyRules(transactionInput: TransactionRuleData) {
     return getMinimumRuleOutput(
-      [this.turnoverRule, this.discountRule, this.defaultRule],
+      [this.turnoverRule, this.discountRule, this.firstDayOfMonthFreeRule, this.defaultRule],
       transactionInput,
     );
   }
 
-  getExchangeRateResponse = promisifyObservable(this.exchangeRateService.convertCurrency.bind(this.exchangeRateService));
+  getExchangeRateResponse = promisifyObservable(
+    this.exchangeRateService.convertCurrency.bind(this.exchangeRateService),
+  );
 
   async getExchangeRateIfNeeded(transactionInput: TransactionInput) {
     if (transactionInput.currency === Currency.EUR) {

src/transaction/transaction.dto.ts

@@ -9,9 +9,11 @@ export enum Currency {
   EUR = 'EUR',
 }
 
-export enum DiscountRuleForClientById {
-  client_42 = 0.05,
-}
+export const DISCOUNTED_COMMISSIONS = new Map<number, number>([
+  [42, 0.05],
+  [10, 0.02],
+  [20, 0.01]
+]);
 
 export enum DefaultCommissionPercentage {
   percentage = 0.5,