Feature/vasundharam exchange rate provider

jobs/Backend/Task/.gitignore

@@ -0,0 +1,17 @@
+bin/
+obj/
+*.user
+*.suo
+*.userosscache
+*.sln.docstates
+
+[Dd]ebug/
+[Rr]elease/
+bld/
+
+.idea/
+*.iml
+.DS_Store
+
+*.swp
+*.swo

jobs/Backend/Task/ExchangeRateUpdater.csproj

@@ -3,6 +3,33 @@
   <PropertyGroup>
     <OutputType>Exe</OutputType>
     <TargetFramework>net6.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <RootNamespace>ExchangeRateUpdater</RootNamespace>
   </PropertyGroup>
 
-</Project>
+  <ItemGroup>
+    <Compile Remove="test/**" />
+    <None Remove="test/**" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.Extensions.Http" Version="6.0.1" />
+    <PackageReference Include="Microsoft.Extensions.Http.Polly" Version="6.0.1" />
+    <PackageReference Include="Microsoft.Extensions.Logging" Version="6.0.1" />
+    <PackageReference Include="Microsoft.Extensions.Logging.Console" Version="6.0.1" />
+    <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="6.0.2" />
+    <PackageReference Include="Microsoft.Extensions.Configuration" Version="6.0.2" />
+    <PackageReference Include="Microsoft.Extensions.Configuration.Json" Version="6.0.1" />
+    <PackageReference Include="Polly" Version="7.2.3" />
+    <PackageReference Include="Polly.Extensions.Http" Version="3.0.0" />
+    <PackageReference Include="System.Xml.ReaderWriter" Version="4.3.1" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Content Include="appsettings.json">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </Content>
+  </ItemGroup>
+
+</Project>

jobs/Backend/Task/appsettings.json

@@ -0,0 +1,18 @@
+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft": "Warning",
+      "Microsoft.Extensions.Http": "Warning",
+      "ExchangeRateUpdater": "Information"
+    }
+  },
+  "CnbApi": {
+    "BaseUrl": "https://www.cnb.cz/cs/financni-trhy/devizovy-trh/kurzy-devizoveho-trhu/kurzy-devizoveho-trhu/denni_kurz.xml",
+    "TimeoutSeconds": 30,
+    "RetryCount": 3,
+    "CircuitBreakerFailureThreshold": 5,
+    "CircuitBreakerDurationSeconds": 30
+  }
+}
+

jobs/Backend/Task/src/Configuration/CnbApiOptions.cs

@@ -0,0 +1,12 @@
+namespace ExchangeRateUpdater;
+
+public class CnbApiOptions
+{
+    public const string SectionName = "CnbApi";
+
+    public string BaseUrl { get; set; } = string.Empty;
+    public int TimeoutSeconds { get; set; }
+    public int RetryCount { get; set; }
+    public int CircuitBreakerFailureThreshold { get; set; }
+    public int CircuitBreakerDurationSeconds { get; set; }
+}

jobs/Backend/Task/src/Configuration/DependencyInjectionExtensions.cs

@@ -0,0 +1,42 @@
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Options;
+using Polly;
+using Polly.Extensions.Http;
+
+namespace ExchangeRateUpdater;
+
+public static class DependencyInjectionExtensions
+{
+    public static IServiceCollection ConfigureServices(this IServiceCollection services, IConfiguration configuration)
+    {
+        services.Configure<CnbApiOptions>(configuration.GetSection(CnbApiOptions.SectionName));
+        services.AddScoped<ICnbResponseParser, CnbResponseParser>();
+
+        services.AddHttpClient<ICnbExchangeRateService, CnbExchangeRateService>()
+            .AddPolicyHandler((serviceProvider, _) => GetRetryPolicy(serviceProvider))
+            .AddPolicyHandler((serviceProvider, _) => GetCircuitBreakerPolicy(serviceProvider));
+
+        services.AddScoped<ExchangeRateProvider>();
+
+        return services;
+    }
+
+    private static IAsyncPolicy<HttpResponseMessage> GetRetryPolicy(IServiceProvider serviceProvider)
+    {
+        var options = serviceProvider.GetRequiredService<IOptions<CnbApiOptions>>().Value;
+
+        return HttpPolicyExtensions
+            .HandleTransientHttpError()
+            .WaitAndRetryAsync(options.RetryCount, retryAttempt => TimeSpan.FromSeconds(Math.Pow(2, retryAttempt)));
+    }
+
+    private static IAsyncPolicy<HttpResponseMessage> GetCircuitBreakerPolicy(IServiceProvider serviceProvider)
+    {
+        var options = serviceProvider.GetRequiredService<IOptions<CnbApiOptions>>().Value;
+
+        return HttpPolicyExtensions
+            .HandleTransientHttpError()
+            .CircuitBreakerAsync(options.CircuitBreakerFailureThreshold, TimeSpan.FromSeconds(options.CircuitBreakerDurationSeconds));
+    }
+}

jobs/Backend/Task/src/Constants/CnbConstants.cs

@@ -0,0 +1,19 @@
+namespace ExchangeRateUpdater;
+
+public static class CnbConstants
+{
+    public const string BaseCurrencyCode = "CZK";
+    public const string DateFormat = "dd.MM.yyyy";
+
+    // XML element and attribute names from CNB response (in Czech)
+    public const string XmlRootElementName = "kurzy";
+    public const string XmlRowElementName = "radek";
+    public const string DateAttributeName = "datum";
+    public const string CodeAttributeName = "kod";
+    public const string AmountAttributeName = "mnozstvi";
+    public const string RateAttributeName = "kurz";
+
+    // Culture and query parameters
+    public const string CzechCultureCode = "cs-CZ";
+    public const string DateQueryParameter = "date";
+}

jobs/Backend/Task/src/Exceptions/CnbApiException.cs

@@ -0,0 +1,12 @@
+namespace ExchangeRateUpdater;
+
+public class CnbApiException : Exception
+{
+    public CnbApiException(string message) : base(message)
+    {
+    }
+
+    public CnbApiException(string message, Exception innerException) : base(message, innerException)
+    {
+    }
+}

jobs/Backend/Task/src/Models/Currency.cs

@@ -0,0 +1,21 @@
+namespace ExchangeRateUpdater;
+
+public class Currency
+{
+    public string Code { get; }
+
+    /// <summary>
+    /// Three-letter ISO 4217 code of the currency.
+    /// </summary>
+    public Currency(string code)
+    {
+        if (string.IsNullOrWhiteSpace(code) || code.Length != 3)
+        {
+            throw new ArgumentException($"Currency code must be exactly 3 characters, got '{code}'", nameof(code));
+        }
+
+        Code = code.ToUpperInvariant();
+    }
+
+    public override string ToString() => Code;
+}

jobs/Backend/Task/src/Models/ExchangeRate.cs

@@ -0,0 +1,23 @@
+namespace ExchangeRateUpdater;
+
+public class ExchangeRate
+{
+    public Currency SourceCurrency { get; }
+    public Currency TargetCurrency { get; }
+    public decimal Value { get; }
+
+    public ExchangeRate(Currency sourceCurrency, Currency targetCurrency, decimal value)
+    {
+        SourceCurrency = sourceCurrency ?? throw new ArgumentNullException(nameof(sourceCurrency));
+        TargetCurrency = targetCurrency ?? throw new ArgumentNullException(nameof(targetCurrency));
+
+        if (value <= 0)
+        {
+            throw new ArgumentException("Exchange rate must be greater than zero", nameof(value));
+        }
+
+        Value = value;
+    }
+
+    public override string ToString() => $"{SourceCurrency}/{TargetCurrency}={Value}";
+}

jobs/Backend/Task/src/Program.cs

@@ -0,0 +1,65 @@
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging;
+
+namespace ExchangeRateUpdater;
+
+public static class Program
+{
+    private static readonly Currency[] Currencies = new[]
+    {
+        new Currency("USD"),
+        new Currency("EUR"),
+        new Currency("CZK"),
+        new Currency("JPY"),
+        new Currency("KES"),
+        new Currency("RUB"),
+        new Currency("THB"),
+        new Currency("TRY"),
+        new Currency("INR")
+    };
+
+    public static async Task Main()
+    {
+        var configuration = new ConfigurationBuilder()
+            .SetBasePath(Directory.GetCurrentDirectory())
+            .AddJsonFile("appsettings.json", optional: false, reloadOnChange: true)
+            .Build();
+
+        var services = new ServiceCollection();
+
+        services.AddLogging(builder =>
+        {
+            builder.AddConsole();
+            builder.AddConfiguration(configuration.GetSection("Logging"));
+        });
+
+        services.ConfigureServices(configuration);
+
+        using var serviceProvider = services.BuildServiceProvider();
+        var provider = serviceProvider.GetRequiredService<ExchangeRateProvider>();
+
+        try
+        {
+            var rates = await provider.GetExchangeRatesAsync(Currencies);
+            var ratesList = rates.ToList();
+
+            if (ratesList.Count == 0)
+            {
+                Console.WriteLine("No exchange rates were retrieved.");
+                return;
+            }
+
+            foreach (var rate in ratesList)
+            {
+                Console.WriteLine(rate.ToString());
+            }
+        }
+        catch (Exception ex)
+        {
+            Console.WriteLine($"Could not retrieve exchange rates: '{ex.Message}'.");
+        }
+
+        Console.ReadLine();
+    }
+}