Exchange Rate Currency Task

fullstack/task/packages/client/package.json

@@ -4,6 +4,12 @@
     "version": "1.0.0",
     "dependencies": {
         "@apollo/client": "3.7.10",
+        "@emotion/react": "^11.14.0",
+        "@emotion/styled": "^11.14.0",
+        "@mui/material": "^6.3.0",
+        "@mui/system": "^6.3.0",
+        "@mui/x-data-grid": "^7.23.5",
+        "dayjs": "^1.11.13",
         "graphql": "16.6.0",
         "graphql-tag": "2.12.6",
         "graphql-ws": "5.12.0",

fullstack/task/packages/client/src/App.tsx

@@ -1,5 +1,7 @@
+import ExchangeRateTable from "./components/ExchangeRateTable";
+
 function App() {
-    return <p>TODO</p>;
+    return <ExchangeRateTable />;
 }
 
 export default App;

fullstack/task/packages/client/src/components/ExchangeRateTable.tsx

@@ -0,0 +1,75 @@
+import React from 'react';
+import { useQuery } from '@apollo/client';
+import { GET_EXCHANGE_RATES } from '../graphql/queries';
+import { DataGrid, GridToolbar } from '@mui/x-data-grid';
+import { Typography, Box, Paper } from '@mui/material';
+import dayjs from 'dayjs'; 
+
+const ExchangeRateTable: React.FC = () => {
+  const { loading, error, data } = useQuery(GET_EXCHANGE_RATES);
+  console.log('data', data);
+
+  if (loading) return <p>Loading...</p>;
+  if (error) return <p>Error: {error.message}</p>;
+
+  const rows = data.exchangeRates.map((rate: any, index: number) => ({
+    id: index, 
+    amount: rate.amount || 'N/A',
+    code: rate.code || 'N/A',
+    country: rate.country || 'N/A',
+    currency: rate.currency,
+    rate: rate.rate,
+  }));
+
+  const columns = [
+    { field: 'country', headerName: 'Country', width: 150 },
+    { field: 'currency', headerName: 'Currency', width: 150 },
+    { field: 'amount', headerName: 'Amount', width: 150 },
+    { field: 'code', headerName: 'Code', width: 150 },
+    { field: 'rate', headerName: 'Rate', width: 100 },
+  ];
+
+  const lastFetched = dayjs(data.exchangeRates[0]?.updatedAtUtc).format(
+    'MMMM D, YYYY h:mm A'
+  );
+
+  return (
+    <Box
+      sx={{
+        display: 'flex',
+        justifyContent: 'center',
+        alignItems: 'center',
+        backgroundColor: '#f9f9f9',
+      }}
+    >
+      <Paper
+        sx={{
+          padding: 3,
+          boxShadow: 3,
+          borderRadius: 2,
+        }}
+      >
+        <Box
+          sx={{
+            marginBottom: 2,
+            padding: 1,
+            backgroundColor: '#f5f5f5',
+            borderRadius: '4px',
+          }}
+        >
+          <Typography variant="subtitle1" color="textSecondary">
+            <strong>Last Fetched:</strong> {lastFetched}
+          </Typography>
+        </Box>
+        <DataGrid
+          rows={rows}
+          columns={columns}
+          loading={loading}
+          slots={{ toolbar: GridToolbar }}
+        />
+      </Paper>
+    </Box>
+  );
+};
+
+export default ExchangeRateTable;

fullstack/task/packages/client/src/graphql/queries.ts

@@ -0,0 +1,14 @@
+import { gql } from '@apollo/client';
+
+export const GET_EXCHANGE_RATES = gql`
+  query {
+    exchangeRates {
+      rate
+      currency
+      country
+      amount
+      code
+      updatedAtUtc
+    }
+  }
+`;

fullstack/task/packages/client/src/main.tsx

@@ -4,7 +4,7 @@ import { ApolloClient, ApolloProvider, InMemoryCache } from '@apollo/client';
 import App from './App';
 
 const client = new ApolloClient({
-    uri: 'http://localhost:4000/graphql',
+    uri: 'http://localhost:4001/graphql',
     cache: new InMemoryCache(),
 });
 

fullstack/task/packages/server/.env

@@ -9,3 +9,5 @@ GQL_PLAYGROUND=true
 GQL_INTROSPECTION=true
 
 PORT=4001
+
+EXCHANGE_RATE_API_URL=https://www.cnb.cz/en/financial-markets/foreign-exchange-market/central-bank-exchange-rate-fixing/central-bank-exchange-rate-fixing/daily.txt

fullstack/task/packages/server/package.json

@@ -10,6 +10,7 @@
     },
     "dependencies": {
         "@nestjs/apollo": "10.1.3",
+        "@nestjs/axios": "^3.1.3",
         "@nestjs/common": "9.3.12",
         "@nestjs/config": "2.2.0",
         "@nestjs/core": "9.3.12",

fullstack/task/packages/server/schema.gql

@@ -17,8 +17,21 @@ A date-time string at UTC, such as 2019-12-03T09:54:33Z, compliant with the date
 """
 scalar DateTime
 
+type ExchangeRate {
+  id: ID!
+  createdAtUtc: DateTime!
+  updatedAtUtc: DateTime
+  deleteDateUtc: DateTime
+  version: Int!
+  country: String!
+  currency: String!
+  amount: Float!
+  code: String!
+  rate: Float!
+}
+
 type Query {
-  exchangeRates: String!
+  exchangeRates: [ExchangeRate!]!
   exampleByName(name: String!): Example
 }
 

fullstack/task/packages/server/src/app.module.ts

@@ -5,11 +5,13 @@ import { TypeOrmModule } from '@nestjs/typeorm';
 import { graphqlConfig, typeormConfig } from './config';
 import { modules } from './entity-modules';
 import { ExchangeRateModule } from './services/exchange-rate/exchange-rate.module';
+import { exchangeRateConfig } from './config/exchange-rates';
 
 @Module({
     imports: [
         ConfigModule.forRoot({
             isGlobal: true,
+            load: [() => ({ exchangeRate: exchangeRateConfig })], 
         }),
         TypeOrmModule.forRoot(typeormConfig),
         GraphQLModule.forRoot(graphqlConfig),

fullstack/task/packages/server/src/config/exchange-rates/exchange-rates-config.ts

@@ -0,0 +1,11 @@
+import { config } from 'dotenv';
+
+config();
+
+const {
+    EXCHANGE_RATE_API_URL: exchangeRateApi,
+} = process.env;
+
+export const exchangeRateConfig = {
+    apiUrl: exchangeRateApi,
+};

fullstack/task/packages/server/src/config/exchange-rates/index.ts

@@ -0,0 +1 @@
+export * from './exchange-rates-config';

fullstack/task/packages/server/src/entities/constants.ts

@@ -1 +1,4 @@
 export const VAR_CHAR = { type: 'varchar', length: 255 } as const;
+export const DECIMAL = { type: 'decimal' } as const;
+export const TIMESTAMP_TZ = { type: 'timestamptz' } as const;
+export const INT = { type: 'int' } as const;

fullstack/task/packages/server/src/entities/exchange-rates.entity.ts

@@ -0,0 +1,36 @@
+import { Field, Float, ObjectType } from '@nestjs/graphql';
+import { IsInt, IsString, MinLength } from 'class-validator';
+import { Column, Entity } from 'typeorm';
+import { EntityWithMeta } from '../common';
+import { VAR_CHAR, DECIMAL, INT } from './constants';
+
+@ObjectType()
+@Entity()
+export class ExchangeRate extends EntityWithMeta {
+    @IsString()
+    @MinLength(1)
+    @Field(() => String)
+    @Column({ ...VAR_CHAR })
+    public country!: string;
+
+    @IsString()
+    @MinLength(1)
+    @Field(() => String)
+    @Column({ ...VAR_CHAR })
+    public currency!: string;
+
+    @IsInt()
+    @Field(() => Number)
+    @Column({ ...INT })
+    public amount!: number;
+
+    @IsString()
+    @MinLength(1)
+    @Field(() => String)
+    @Column({ ...VAR_CHAR })
+    public code!: string;
+
+    @Field(() => Float)
+    @Column({ ...DECIMAL })
+    public rate!: number;
+}

fullstack/task/packages/server/src/migrations/1735573865264-createExchangeRatesTable.ts

@@ -0,0 +1,14 @@
+import { MigrationInterface, QueryRunner } from "typeorm";
+
+export class createExchangeRatesTable1735573865264 implements MigrationInterface {
+    name = 'createExchangeRatesTable1735573865264'
+
+    public async up(queryRunner: QueryRunner): Promise<void> {
+        await queryRunner.query(`ALTER TABLE "exchange_rate" ALTER COLUMN "rate" TYPE numeric`);
+    }
+
+    public async down(queryRunner: QueryRunner): Promise<void> {
+        await queryRunner.query(`ALTER TABLE "exchange_rate" ALTER COLUMN "rate" TYPE numeric(3,3)`);
+    }
+
+}

fullstack/task/packages/server/src/services/exchange-rate/exchange-rate.module.ts

@@ -1,9 +1,12 @@
 import { Module } from '@nestjs/common';
+import { TypeOrmModule } from '@nestjs/typeorm';
 import { ExchangeRateService } from './exchange-rate.service';
 import { ExchangeRateResolver } from './exchange-rate.resolver';
+import { HttpModule } from '@nestjs/axios';
+import { ExchangeRate } from 'src/entities/exchange-rates.entity';
 
 @Module({
-    imports: [],
+    imports: [HttpModule,TypeOrmModule.forFeature([ExchangeRate])],
     providers: [ExchangeRateService, ExchangeRateResolver],
     exports: [ExchangeRateService],
 })

fullstack/task/packages/server/src/services/exchange-rate/exchange-rate.repository.ts

@@ -0,0 +1,4 @@
+import { Repository } from 'typeorm';
+import { ExchangeRate } from 'src/entities/exchange-rates.entity';
+
+export class ExchangeRateRepository extends Repository<ExchangeRate> {}

fullstack/task/packages/server/src/services/exchange-rate/exchange-rate.resolver.ts

@@ -1,13 +1,14 @@
 import { Query, Resolver } from '@nestjs/graphql';
 import { ExchangeRateService } from './exchange-rate.service';
+import { ExchangeRate } from 'src/entities/exchange-rates.entity';
 
-@Resolver()
+@Resolver(() => ExchangeRate)
 export class ExchangeRateResolver {
-    constructor(private readonly exchangeRateService: ExchangeRateService) {}
+  constructor(private readonly exchangeRateService: ExchangeRateService) {}
 
-    // TODO: Implement a GraphQL Query that returns the exchange rates
-    @Query(() => String)
-    async exchangeRates(): Promise<string> {
-        return 'Hello';
-    }
+  @Query(() => [ExchangeRate])
+  async exchangeRates(): Promise<ExchangeRate[]> {
+    const exchangeRates = await this.exchangeRateService.getExchangeRates();
+    return exchangeRates;
+  }
 }

fullstack/task/packages/server/src/services/exchange-rate/exchange-rate.service.ts

@@ -1,11 +1,85 @@
-import { Injectable } from '@nestjs/common';
+import { Injectable, NotFoundException } from '@nestjs/common';
+import { ConfigService } from '@nestjs/config';
+import { HttpService } from '@nestjs/axios';
+import { firstValueFrom } from 'rxjs';
+import { InjectRepository } from '@nestjs/typeorm';
+import { Repository } from 'typeorm';
+import { ExchangeRate } from 'src/entities/exchange-rates.entity';
 
 @Injectable()
 export class ExchangeRateService {
-    public getExchangeRates = async () => {
-        // TODO: Implement the fetching and parsing of the exchange rates.
-        // Use this method in the resolver.
+    private readonly CACHE_LIFETIME_MS = 5 * 60 * 1000; // 5 minutes
 
-        return [];
+    constructor(
+        private readonly configService: ConfigService,
+        private readonly httpService: HttpService,
+
+        @InjectRepository(ExchangeRate)
+        private readonly exchangeRateRepository: Repository<ExchangeRate>
+    ) {}
+
+    public getExchangeRates = async (): Promise<ExchangeRate[]> => {
+        const now = new Date();
+        const oldestAllowedTime = new Date(now.getTime() - this.CACHE_LIFETIME_MS);
+
+        // Check if cached data is still valid
+        const latestRate = await this.exchangeRateRepository.findOne({
+            where: {},
+            order: { updatedAtUtc: 'DESC' },
+        });
+
+        if (latestRate && latestRate.updatedAtUtc && latestRate.updatedAtUtc > oldestAllowedTime) {
+            console.log('Returning cached exchange rates from the database');
+            return await this.getExchangeRatesFromDB();
+        }
+
+        // Fetch new data from the API
+        console.log('Fetching new exchange rates from the API');
+        const apiUrl = this.configService.get<string>('exchangeRate.apiUrl') || '';
+
+        try {
+            const response = await firstValueFrom(this.httpService.get(apiUrl));
+            console.log('API Response:', response.data);
+
+            const rates = this.parseExchangeRates(response.data);
+            await this.saveExchangeRatesToDB(rates);
+
+            console.log('Exchange rates updated successfully');
+            return rates;
+        } catch (err) {
+            console.error('Error fetching exchange rates:', err);
+            throw new Error('Failed to fetch exchange rates from the API');
+        }
+    };
+
+    private getExchangeRatesFromDB = async (): Promise<ExchangeRate[]> => {
+        const rates = await this.exchangeRateRepository.find();
+        if (!rates || rates.length === 0) {
+            throw new NotFoundException('No exchange rates found in the database');
+        }
+        return rates;
+    };
+
+    private parseExchangeRates = (data: string): ExchangeRate[] => {
+        return data
+            .split('\n')
+            .slice(2) 
+            .filter(line => line.trim()) 
+            .map(line => {
+                const [country, currency, amount, code, rate] = line.split('|');
+                return {
+                    country: country.trim(),
+                    currency: currency.trim(),
+                    amount: parseInt(amount, 10),
+                    code: code.trim(),
+                    rate: parseFloat(rate),
+                } as ExchangeRate;
+            })
+    };
+
+    private saveExchangeRatesToDB = async (rates: ExchangeRate[]): Promise<void> => {
+        await this.exchangeRateRepository.clear();
+
+        await this.exchangeRateRepository.save(rates);
     };
 }