Evaraimundez

jobs/Backend/Task/CnbClient.cs

@@ -0,0 +1,56 @@
+using Polly;
+using Polly.Retry;
+using System;
+using System.IO;
+using System.Net.Http;
+
+namespace ExchangeRateUpdater
+{
+
+    internal class CnbClient : ICnbClient
+    {
+        private readonly CnbSettings _settings;
+        private readonly HttpClient _client = new();
+        private readonly RetryPolicy<string> _retryPolicy;
+
+        public CnbClient(CnbSettings settings)
+        {
+            _settings = settings;
+            _retryPolicy = Policy<string>
+                .Handle<HttpRequestException>()
+                .Or<IOException>()
+                .WaitAndRetry(_settings.RetryAttempts, retryAttempt => TimeSpan.FromSeconds(Math.Pow(2, retryAttempt)));
+        }
+
+        public (bool Success, string RawData) GetRawDailyExchanges()
+        {
+            string rawData;
+
+            try
+            {
+                rawData = _retryPolicy.Execute(ReadRawData);
+            }
+            catch (HttpRequestException)
+            {
+                return (false, string.Empty);
+            }
+            catch (IOException)
+            {
+                return (false, string.Empty);
+            }
+
+            return (true, rawData);
+        }
+
+        private string ReadRawData()
+        {
+            using var request = new HttpRequestMessage(HttpMethod.Get, _settings.SourceUrl);
+            using var response = _client.Send(request);
+
+            response.EnsureSuccessStatusCode();
+
+            using var reader = new StreamReader(response.Content.ReadAsStream());
+            return reader.ReadToEnd();
+        }
+    }
+}

jobs/Backend/Task/CnbSettings.cs

@@ -0,0 +1,5 @@
+namespace ExchangeRateUpdater
+{
+    public record CnbSettings(string SourceUrl, string TargetCurrencyCode, int RetryAttempts);
+}
+

jobs/Backend/Task/ConfigurationReader.cs

@@ -0,0 +1,26 @@
+using Microsoft.Extensions.Configuration;
+using System;
+
+namespace ExchangeRateUpdater
+{
+    public class ConfigurationReader(IConfiguration config) : IConfigurationReader
+    {
+        private readonly IConfiguration _config = config;
+        private const string SectionName = "CnbSettings";
+
+        public CnbSettings ReadSettings()
+        {
+            var section = _config.GetSection("CnbSettings");
+            string url = section["SourceUrl"] ?? throw new InvalidOperationException($"{SectionName}:SourceUrl is missing in appsettings.json.");
+            string target = section["TargetCurrencyCode"] ?? "CZK";
+
+            if (!int.TryParse(section["RetryAttempts"], out int retryAttempts))
+            {
+                retryAttempts = 3; // Default fallback
+            }
+
+            return new CnbSettings(url, target, retryAttempts);
+        }
+    }
+}
+

jobs/Backend/Task/ExchangeRateProvider.cs

@@ -1,19 +1,71 @@
-using System.Collections.Generic;
+using System;
+using System.Collections.Generic;
+using System.Globalization;
 using System.Linq;
 
 namespace ExchangeRateUpdater
 {
     public class ExchangeRateProvider
     {
+        private readonly CnbSettings _settings;
+        private readonly Currency _targetCurrency;
+        private readonly ICnbClient _cnbClient;
+
+        public ExchangeRateProvider(CnbSettings settings, ICnbClient cnbClient)
+        {
+            _settings = settings;
+            _targetCurrency = new Currency(_settings.TargetCurrencyCode);
+            _cnbClient = cnbClient;
+        }
+
         /// <summary>
         /// Should return exchange rates among the specified currencies that are defined by the source. But only those defined
         /// by the source, do not return calculated exchange rates. E.g. if the source contains "CZK/USD" but not "USD/CZK",
         /// do not return exchange rate "USD/CZK" with value calculated as 1 / "CZK/USD". If the source does not provide
         /// some of the currencies, ignore them.
         /// </summary>
+        /// 
         public IEnumerable<ExchangeRate> GetExchangeRates(IEnumerable<Currency> currencies)
         {
-            return Enumerable.Empty<ExchangeRate>();
+            var requestedCurrencies = currencies.ToDictionary(c => c.Code, c => c, StringComparer.OrdinalIgnoreCase);
+
+            if (requestedCurrencies.Count == 0)
+            {
+                return [];
+
+            }
+
+            var (success, rawData) = _cnbClient.GetRawDailyExchanges();
+            if (!success)
+            {
+                return [];
+            }
+
+            var rates = ParseData(rawData, requestedCurrencies);
+            return rates;
+        }
+
+        private IEnumerable<ExchangeRate> ParseData(string rawData, Dictionary<string, Currency> requestedCurrencies)
+        {
+            var rates = new List<ExchangeRate>();
+            var lines = rawData.Split(["\n", "\r\n"], StringSplitOptions.RemoveEmptyEntries);
+
+            foreach (var line in lines.Skip(2))
+            {
+                var cols = line.Split('|');
+                if (cols.Length < 5) continue;
+
+                var code = cols[3].Trim();
+                if (requestedCurrencies.TryGetValue(code, out var sourceCurrency))
+                {
+                    if (int.TryParse(cols[2].Trim(), out int amount) && amount > 0 &&
+                        decimal.TryParse(cols[4].Trim(), NumberStyles.Any, CultureInfo.InvariantCulture, out decimal rateValue))
+                    {
+                        rates.Add(new ExchangeRate(sourceCurrency, _targetCurrency, rateValue / amount));
+                    }
+                }
+            }
+            return rates;
         }
     }
 }

jobs/Backend/Task/ExchangeRateUpdater.csproj

@@ -2,7 +2,19 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>net6.0</TargetFramework>
+    <TargetFramework>net10.0</TargetFramework>
   </PropertyGroup>
 
+  <ItemGroup>
+    <PackageReference Include="Microsoft.Extensions.Configuration" Version="10.0.7" />
+    <PackageReference Include="Microsoft.Extensions.Configuration.Json" Version="10.0.7" />
+    <PackageReference Include="Polly" Version="8.6.6" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <None Update="appSettings.json">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </None>
+  </ItemGroup>
+
 </Project>

jobs/Backend/Task/ICnbClient.cs

@@ -0,0 +1,7 @@
+namespace ExchangeRateUpdater
+{
+    public interface ICnbClient
+    {
+        (bool Success, string RawData) GetRawDailyExchanges();
+    }
+}

jobs/Backend/Task/IConfigurationReader.cs

@@ -0,0 +1,8 @@
+namespace ExchangeRateUpdater
+{
+    public interface IConfigurationReader
+    {
+        CnbSettings ReadSettings();
+    }
+}
+

jobs/Backend/Task/Program.cs

@@ -1,5 +1,7 @@
-using System;
+using Microsoft.Extensions.Configuration;
+using System;
 using System.Collections.Generic;
+using System.IO;
 using System.Linq;
 
 namespace ExchangeRateUpdater
@@ -23,7 +25,17 @@ public static void Main(string[] args)
         {
             try
             {
-                var provider = new ExchangeRateProvider();
+                var config = new ConfigurationBuilder()
+                .AddJsonFile(Path.Combine(AppContext.BaseDirectory, "appSettings.json"))
+                .Build();
+
+                var configurationReader = new ConfigurationReader(config);
+
+                var settings = configurationReader.ReadSettings();
+
+                var client = new CnbClient(settings);
+
+                var provider = new ExchangeRateProvider(settings, client);
                 var rates = provider.GetExchangeRates(currencies);
 
                 Console.WriteLine($"Successfully retrieved {rates.Count()} exchange rates:");

jobs/Backend/Task/appSettings.json

@@ -0,0 +1,7 @@
+{
+  "CnbSettings": {
+    "SourceUrl": "https://www.cnb.cz/en/financial-markets/foreign-exchange-market/central-bank-exchange-rate-fixing/central-bank-exchange-rate-fixing/daily.txt",
+    "TargetCurrencyCode": "CZK",
+    "RetryAttempts": 3
+  }
+}