CNB Exchange Rate Provider - Sergio Mendiola Arraez

jobs/Backend/Task/ExchangeRateUpdater/ExchangeRateUpdater.Api/Controllers/ExchangeRatesController.cs

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+using Microsoft.AspNetCore.Mvc;
+using ExchangeRateUpdater.Application.Interfaces;
+
+namespace ExchangeRateUpdater.Api.Controllers;
+
+[ApiController]
+[Route("api/[controller]")]
+public class ExchangeRatesController : ControllerBase
+{
+    private readonly IExchangeRateService _service;
+    private readonly ILogger<ExchangeRatesController> _logger;
+
+    public ExchangeRatesController(IExchangeRateService service, ILogger<ExchangeRatesController> logger)
+    {
+        _service = service;
+        _logger = logger;
+    }
+
+    [HttpGet]
+    public async Task<ActionResult> GetAll(CancellationToken ct)
+    {
+        _logger.LogInformation("GET /api/exchangerates");
+        var result = await _service.GetAllRatesAsync(ct);
+        return Ok(result);
+    }
+
+    [HttpGet("{currencyCode}")]
+    public async Task<ActionResult> Get(string currencyCode, CancellationToken ct)
+    {
+        _logger.LogInformation("GET /api/exchangerates/{Currency}", currencyCode);
+        var result = await _service.GetRateByCurrencyAsync(currencyCode, ct);
+        return result is null ? NotFound() : Ok(result);
+    }
+}

jobs/Backend/Task/ExchangeRateUpdater/ExchangeRateUpdater.Api/ExchangeRateUpdater.Api.csproj

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+<Project Sdk="Microsoft.NET.Sdk.Web">
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Swashbuckle.AspNetCore" Version="6.9.0" />
+    <PackageReference Include="Asp.Versioning.Mvc" Version="8.0.0" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\ExchangeRateUpdater.Application\ExchangeRateUpdater.Application.csproj" />
+    <ProjectReference Include="..\ExchangeRateUpdater.Infrastructure\ExchangeRateUpdater.Infrastructure.csproj" />
+  </ItemGroup>
+</Project>

jobs/Backend/Task/ExchangeRateUpdater/ExchangeRateUpdater.Api/Program.cs

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+using ExchangeRateUpdater.Application.Interfaces;
+using ExchangeRateUpdater.Application.Services;
+using ExchangeRateUpdater.Domain.Interfaces;
+using ExchangeRateUpdater.Infrastructure.Http;
+using Microsoft.OpenApi.Models;
+
+var builder = WebApplication.CreateBuilder(args);
+
+// Swagger
+builder.Services.AddEndpointsApiExplorer();
+builder.Services.AddSwaggerGen();
+
+// Controllers
+builder.Services.AddControllers();
+
+// Clean Architecture DI
+builder.Services.AddHttpClient<IExchangeRateRepository, CnbHttpExchangeRateRepository>();
+builder.Services.AddScoped<IExchangeRateService, ExchangeRateService>();
+
+var app = builder.Build();
+
+app.UseSwagger();
+app.UseSwaggerUI(options => options.SwaggerEndpoint("/swagger/v1/swagger.json", "v1"));
+
+app.MapControllers();
+
+app.Run();

jobs/Backend/Task/ExchangeRateUpdater/ExchangeRateUpdater.Api/Properties/launchSettings.json

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+{
+  "$schema": "https://json.schemastore.org/launchsettings.json",
+  "profiles": {
+    "http": {
+      "commandName": "Project",
+      "dotnetRunMessages": true,
+      "launchBrowser": false,
+      "applicationUrl": "http://localhost:5131",
+      "environmentVariables": {
+        "ASPNETCORE_ENVIRONMENT": "Development"
+      }
+    },
+    "https": {
+      "commandName": "Project",
+      "dotnetRunMessages": true,
+      "launchBrowser": false,
+      "applicationUrl": "https://localhost:7012;http://localhost:5131",
+      "environmentVariables": {
+        "ASPNETCORE_ENVIRONMENT": "Development"
+      }
+    }
+  }
+}

jobs/Backend/Task/ExchangeRateUpdater/ExchangeRateUpdater.Api/appsettings.Development.json

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+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft.AspNetCore": "Warning"
+    }
+  }
+}

jobs/Backend/Task/ExchangeRateUpdater/ExchangeRateUpdater.Api/appsettings.json

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+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft.AspNetCore": "Warning"
+    }
+  },
+  "AllowedHosts": "*"
+}

jobs/Backend/Task/ExchangeRateUpdater/ExchangeRateUpdater.Application/DTOs/ExchangeRateDto.cs

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+namespace ExchangeRateUpdater.Application.DTOs;
+
+public record ExchangeRateDto(string CurrencyCode, decimal RateToCZK);
+public record RatesResponse(List<ExchangeRateDto> Rates, int TotalCount, DateTime UpdatedAt);

jobs/Backend/Task/ExchangeRateUpdater/ExchangeRateUpdater.Application/ExchangeRateUpdater.Application.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\ExchangeRateUpdater.Domain\ExchangeRateUpdater.Domain.csproj" />
+    <PackageReference Include="Microsoft.Extensions.Logging.Abstractions" Version="10.0.0" />
+  </ItemGroup>
+</Project>

jobs/Backend/Task/ExchangeRateUpdater/ExchangeRateUpdater.Application/Interfaces/IExchangeRateService.cs

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+using ExchangeRateUpdater.Application.DTOs;
+
+namespace ExchangeRateUpdater.Application.Interfaces;
+
+public interface IExchangeRateService
+{
+    Task<RatesResponse> GetAllRatesAsync(CancellationToken cancellationToken = default);
+    Task<ExchangeRateDto?> GetRateByCurrencyAsync(string currencyCode, CancellationToken cancellationToken = default);
+}

jobs/Backend/Task/ExchangeRateUpdater/ExchangeRateUpdater.Application/Services/ExchangeRateService.cs

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+using ExchangeRateUpdater.Application.DTOs;
+using ExchangeRateUpdater.Application.Interfaces;
+using ExchangeRateUpdater.Domain.Interfaces;
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Logging.Abstractions;
+
+namespace ExchangeRateUpdater.Application.Services;
+
+public class ExchangeRateService : IExchangeRateService
+{
+    private readonly IExchangeRateRepository _repository;
+    private readonly ILogger<ExchangeRateService> _logger;
+
+    public ExchangeRateService(IExchangeRateRepository repository, ILogger<ExchangeRateService>? logger = null)
+    {
+        _repository = repository ?? throw new ArgumentNullException(nameof(repository));
+        _logger = logger ?? NullLogger<ExchangeRateService>.Instance;
+    }
+
+    public async Task<RatesResponse> GetAllRatesAsync(CancellationToken cancellationToken = default)
+    {
+        var ratesDict = await _repository.GetCurrentRatesAsync(cancellationToken);
+        var dtos = ratesDict.Values
+            .OrderBy(r => r.CurrencyCode)
+            .Select(r => new ExchangeRateDto(r.CurrencyCode, r.RateToCZK))
+            .ToList();
+
+        return new RatesResponse(dtos, dtos.Count, DateTime.UtcNow);
+    }
+
+    public async Task<ExchangeRateDto?> GetRateByCurrencyAsync(string currencyCode, CancellationToken cancellationToken = default)
+    {
+        var rates = await _repository.GetCurrentRatesAsync(cancellationToken);
+        return rates.TryGetValue(currencyCode.ToUpperInvariant(), out var rate)
+            ? new ExchangeRateDto(rate.CurrencyCode, rate.RateToCZK)
+            : null;
+    }
+}

jobs/Backend/Task/ExchangeRateUpdater/ExchangeRateUpdater.Domain/Entities/ExchangeRate.cs

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+using System; 
+
+namespace ExchangeRateUpdater.Domain.Entities;
+
+/// <summary>
+/// Official Exchange Rate CNB (1 unit to CZK).
+/// Immutable for thread-safety in API.
+/// </summary>
+public record ExchangeRate
+{
+    public string CurrencyCode { get; init; } = string.Empty;  // ISO4217 uppercase
+    public decimal RateToCZK { get; init; } // Normalized rate /1
+    public DateTime UpdatedAt { get; init; } = DateTime.UtcNow; 
+
+    public ExchangeRate(string code, decimal rate, DateTime updatedAt)
+    {
+        CurrencyCode = code.ToUpperInvariant();
+        RateToCZK = Math.Round(rate, 4);  // CNB precision
+        UpdatedAt = updatedAt;
+    }
+}

jobs/Backend/Task/ExchangeRateUpdater/ExchangeRateUpdater.Domain/ExchangeRateUpdater.Domain.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+  </PropertyGroup>
+</Project>

jobs/Backend/Task/ExchangeRateUpdater/ExchangeRateUpdater.Domain/Interfaces/IExchangeRateRepository.cs

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+using System;
+using System.Collections.Generic;
+using System.Threading;
+using System.Threading.Tasks; 
+using ExchangeRateUpdater.Domain.Entities;
+
+namespace ExchangeRateUpdater.Domain.Interfaces;
+
+public interface IExchangeRateRepository
+{
+    /// <summary>
+    /// GET current CNB rates.
+    /// </summary>
+    Task<IReadOnlyDictionary<string, ExchangeRate>> GetCurrentRatesAsync(CancellationToken cancellationToken = default);
+}

jobs/Backend/Task/ExchangeRateUpdater/ExchangeRateUpdater.Infrastructure/ExchangeRateUpdater.Infrastructure.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+  </PropertyGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\ExchangeRateUpdater.Domain\ExchangeRateUpdater.Domain.csproj" />
+    <ProjectReference Include="..\ExchangeRateUpdater.Application\ExchangeRateUpdater.Application.csproj" />
+    <PackageReference Include="Microsoft.Extensions.Logging.Abstractions" Version="10.0.0" />
+  </ItemGroup>
+</Project>

jobs/Backend/Task/ExchangeRateUpdater/ExchangeRateUpdater.Infrastructure/Http/CnbHttpExchangeRateRepository.cs

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+using System;
+using System.Collections.Generic;
+using System.Net.Http;
+using System.Threading;
+using System.Threading.Tasks;
+using ExchangeRateUpdater.Domain.Entities;
+using ExchangeRateUpdater.Domain.Interfaces;
+using Microsoft.Extensions.Logging;
+using System.Linq;
+using System.Text.Json;
+
+
+namespace ExchangeRateUpdater.Infrastructure.Http;
+
+/// <summary>
+/// CNB-specific HTTP adapter. Replaces with ECBHttpRepository without Domain changes.
+/// HTTP details encapsulated.
+/// </summary>
+public class CnbHttpExchangeRateRepository : IExchangeRateRepository
+{
+    private readonly HttpClient _httpClient;
+    private readonly ILogger<CnbHttpExchangeRateRepository> _logger;
+    private const string CnbJsonRatesUrl = "https://api.cnb.cz/cnbapi/exrates/daily?lang=EN";
+
+    public CnbHttpExchangeRateRepository(HttpClient httpClient, ILogger<CnbHttpExchangeRateRepository> logger)
+    {
+        _httpClient = httpClient ?? throw new ArgumentNullException(nameof(httpClient));
+        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
+        _httpClient.DefaultRequestHeaders.Add("User-Agent", "Mews-ExchangeRateUpdater/1.0");
+    }
+
+    public async Task<IReadOnlyDictionary<string, ExchangeRate>> GetCurrentRatesAsync(CancellationToken ct)
+    {
+        _logger.LogInformation("Fetching CNB JSON rates from {Url}", CnbJsonRatesUrl);
+
+        var response = await _httpClient.GetAsync(CnbJsonRatesUrl, ct);
+        response.EnsureSuccessStatusCode();
+
+        var json = await response.Content.ReadAsStringAsync(ct);
+        var rates = await ParseCnbJsonAsync(json);
+
+        _logger.LogInformation("Parsed {Count} JSON rates from CNB API", rates.Count);
+        return rates;
+    }
+
+    private async Task<Dictionary<string, ExchangeRate>> ParseCnbJsonAsync(string jsonContent)
+    {
+        var cnbResponse = JsonSerializer.Deserialize<CnbDailyResponse>(jsonContent);
+
+        return cnbResponse.rates.ToDictionary(
+            r => r.currencyCode,
+            r => new ExchangeRate(r.currencyCode, r.rate, DateTime.UtcNow));
+    }
+}