Full project

.gitignore

@@ -21,3 +21,10 @@
 node_modules
 bower_components
 npm-debug.log
+*.received.*
+*.received/
+*.vsidx
+*.bin
+*.manifest
+*.testlog
+*.v2

jobs/Backend/ExchangeRateUpdated.Infrastructure/Entities/DailyExchangeRate.cs

@@ -0,0 +1,10 @@
+using ExchangeRateUpdater.Domain.ValueObjects;
+
+namespace ExchangeRateUpdater.Domain.Entities
+{
+    public class DailyExchangeRate(Currency sourceCurrency, Currency targetCurrency, decimal value) : ExchangeRate(sourceCurrency, targetCurrency, value)
+    {
+
+    }
+}
+

jobs/Backend/ExchangeRateUpdated.Infrastructure/Entities/ExchangeRate.cs

@@ -0,0 +1,20 @@
+using ExchangeRateUpdater.Domain.ValueObjects;
+
+namespace ExchangeRateUpdater.Domain.Entities
+{
+    public abstract class ExchangeRate
+    {
+        public Currency SourceCurrency { get; }
+        public Currency TargetCurrency { get; }
+        public decimal Value { get; }
+
+        protected ExchangeRate(Currency sourceCurrency, Currency targetCurrency, decimal value)
+        {
+            SourceCurrency = sourceCurrency;
+            TargetCurrency = targetCurrency;
+            Value = value;
+        }
+
+        public override string ToString() => $"{SourceCurrency} / {TargetCurrency} = {Value}";
+    }
+}

jobs/Backend/ExchangeRateUpdated.Infrastructure/Entities/MonthYearExchangeRate.cs

@@ -0,0 +1,11 @@
+using ExchangeRateUpdater.Domain.ValueObjects;
+
+namespace ExchangeRateUpdater.Domain.Entities
+{
+    public class MonthYearExchangeRate(Currency sourceCurrency, Currency targetCurrency, decimal value, DateOnly date) : ExchangeRate(sourceCurrency, targetCurrency, value)
+    {
+        public DateOnly Date { get; } = date;
+        public override string ToString() => $"{Date:yyyy-MM-dd} | {base.ToString()}";
+    }
+}
+

jobs/Backend/ExchangeRateUpdated.Infrastructure/ExchangeRateUpdater.Domain.csproj

@@ -0,0 +1,13 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net8.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Newtonsoft.Json" Version="13.0.3" />
+  </ItemGroup>
+
+</Project>

jobs/Backend/ExchangeRateUpdated.Infrastructure/Models/ExchangeRateRow.cs

@@ -0,0 +1,28 @@
+using Newtonsoft.Json;
+
+namespace ExchangeRateUpdater.Domain.Models
+{
+    public class ExchangeRateRow
+    {
+        [JsonProperty("validFor")]
+        public DateOnly ValidFor { get; set; }
+
+        [JsonProperty("order")]
+        public int Order { get; set; }
+
+        [JsonProperty("country")]
+        public string Country { get; set; }
+
+        [JsonProperty("currency")]
+        public string Currency { get; set; }
+
+        [JsonProperty("amount")]
+        public int Amount { get; set; }
+
+        [JsonProperty("currencyCode")]
+        public string CurrencyCode { get; set; }
+
+        [JsonProperty("rate")]
+        public decimal Rate { get; set; }
+    }
+}

jobs/Backend/ExchangeRateUpdated.Infrastructure/Models/ExchangeRatesResponse.cs

@@ -0,0 +1,10 @@
+using Newtonsoft.Json;
+
+namespace ExchangeRateUpdater.Domain.Models
+{
+    public class ExchangeRatesResponse
+    {
+        [JsonProperty("rates")]
+        public List<ExchangeRateRow>? Rates { get; set; }
+    }
+}

jobs/Backend/ExchangeRateUpdated.Infrastructure/Shared/Settings.cs

@@ -0,0 +1,8 @@
+namespace ExchangeRateUpdater.Domain.Shared
+{
+    public class Settings
+    {
+        public required string CnbUrl { get; set; }
+        public required string DefaultCurrency { get; set; }
+    }
+}

jobs/Backend/ExchangeRateUpdated.Infrastructure/ValueObjects/Currency.cs

@@ -0,0 +1,13 @@
+namespace ExchangeRateUpdater.Domain.ValueObjects
+{
+    public class Currency(string code)
+    {
+
+        /// <summary>
+        /// Three-letter ISO 4217 code of the currency.
+        /// </summary>
+        private string Code { get; } = code;
+        public override string ToString() => Code;
+
+    }
+}

jobs/Backend/ExchangeRateUpdater.Infrastructure/Configuration/ExchangeRateDateFormats.cs

@@ -0,0 +1,9 @@
+namespace ExchangeRateUpdater.Infrastructure.Configuration
+{
+    public static class ExchangeRateDateFormats
+    {
+        public const string FullDate = "yyyy-MM-dd";
+        public const string YearMonth = "yyyy-MM";
+        public const string Year = "yyyy";
+    }
+}

jobs/Backend/ExchangeRateUpdater.Infrastructure/Configuration/ExchangeRateRoutes.cs

@@ -0,0 +1,9 @@
+namespace ExchangeRateUpdater.Infrastructure.Configuration
+{
+    public static class ExchangeRateRoutes
+    {
+        public const string Daily = "daily";
+        public const string DailyCurrencyMonth = "daily-currency-month";
+        public const string DailyYear = "daily-year";
+    }
+}

jobs/Backend/ExchangeRateUpdater.Infrastructure/Configuration/Helpers/SettingsHelper.cs

@@ -0,0 +1,18 @@
+using Microsoft.Extensions.Configuration;
+
+namespace ExchangeRateUpdater.Infrastructure.Configuration.Helpers
+{
+    public static class SettingsHelper
+    {
+        private static IConfiguration _settings;
+
+        public static void Initialize()
+        {
+            var builder = new ConfigurationBuilder().AddJsonFile("appsettings.json");
+            _settings = builder.Build();
+        }
+
+        public static string GetCnbUrl() => _settings["cnbUrl"] ?? "https://api.cnb.cz/cnbapi/exrates/daily";
+        public static string GetDefaultCurrency() => _settings["DefaultCurrency"] ?? "CZK";
+    }
+}

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

@@ -0,0 +1,21 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net8.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="LanguageExt.Core" Version="4.4.9" />
+    <PackageReference Include="Microsoft.Extensions.Caching.Memory" Version="9.0.0" />
+    <PackageReference Include="Microsoft.Extensions.Configuration" Version="9.0.0" />
+    <PackageReference Include="Microsoft.Extensions.Configuration.Json" Version="9.0.0" />
+    <PackageReference Include="Newtonsoft.Json" Version="13.0.3" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\ExchangeRateUpdated.Infrastructure\ExchangeRateUpdater.Domain.csproj" />
+  </ItemGroup>
+
+</Project>

jobs/Backend/ExchangeRateUpdater.Infrastructure/Extensions/ExchangeRateExtension.cs

@@ -0,0 +1,25 @@
+using ExchangeRateUpdater.Domain.Entities;
+using ExchangeRateUpdater.Domain.Models;
+using ExchangeRateUpdater.Domain.ValueObjects;
+using ExchangeRateUpdater.Infrastructure.Configuration;
+
+namespace ExchangeRateUpdater.Infrastructure.Extensions
+{
+    public static class ExchangeRateExtension
+    {
+        public static IEnumerable<ExchangeRateRow> FilterByCurrencies(this IEnumerable<ExchangeRateRow> exchangeRateRows, IEnumerable<Currency>? currencies) =>
+            currencies is not null && currencies.Any() ?
+                exchangeRateRows.Where(x => currencies.Any(z => z.ToString().Equals(x.CurrencyCode, StringComparison.InvariantCultureIgnoreCase))) : exchangeRateRows;
+
+        public static IEnumerable<ExchangeRate> ToExchangeRates(this IEnumerable<ExchangeRateRow> exchangeRateRows, string scope, Currency targetCurrency) =>
+            scope switch
+            {
+                ExchangeRateRoutes.Daily => exchangeRateRows.Select(x => new DailyExchangeRate(new(x.CurrencyCode), targetCurrency, x.Rate / x.Amount)).Cast<ExchangeRate>().ToList(),
+                ExchangeRateRoutes.DailyCurrencyMonth or ExchangeRateRoutes.DailyYear => exchangeRateRows.Select(x => new MonthYearExchangeRate(new(x.CurrencyCode), targetCurrency, x.Rate / x.Amount, x.ValidFor)).Cast<ExchangeRate>().ToList(),
+                _ => throw new InvalidOperationException()
+            };
+
+        public static IEnumerable<Currency> ToCurrency(this string[] currencies) => currencies.Select(currency => new Currency(currency));
+
+    }
+}

jobs/Backend/ExchangeRateUpdater.Infrastructure/Services/ExchangeRateCacheManager.cs

@@ -0,0 +1,43 @@
+using ExchangeRateUpdater.Domain.Models;
+using LanguageExt.Common;
+using Microsoft.Extensions.Caching.Memory;
+using Newtonsoft.Json;
+
+namespace ExchangeRateUpdater.Infrastructure.Services
+{
+    public class ExchangeRateCacheManager(IMemoryCache memoryCache)
+    {
+        private readonly object _lock = new();
+        private readonly IMemoryCache _memoryCache = memoryCache;
+
+        public Result<List<ExchangeRateRow>> GetDailyRates(string date, string url)
+        {
+            lock (_lock)
+            {
+                var rates = _memoryCache.Get<List<ExchangeRateRow>>(date);
+                if (rates is not null)
+                    return rates;
+
+                return SetDailyRatesAsync(date, url).Result;
+            }
+        }
+        private async Task<Result<List<ExchangeRateRow>>> SetDailyRatesAsync(string date, string url)
+        {
+            try
+            {
+                using var client = new HttpClient();
+                var response = await client.GetAsync(url);
+                var result = JsonConvert.DeserializeObject<ExchangeRatesResponse>(await response.Content.ReadAsStringAsync());
+                if (result is null || result.Rates is null || result.Rates.Count == 0)
+                    return new Result<List<ExchangeRateRow>>(new ArgumentException("No data for the requested information"));
+                _memoryCache.Set(date, result.Rates, TimeOnly.MaxValue - TimeOnly.FromDateTime(DateTime.UtcNow));
+                return result.Rates;
+            }
+            catch (Exception ex)
+            {
+                return new Result<List<ExchangeRateRow>>(ex);
+            }
+        }
+
+    }
+}

jobs/Backend/ExchangeRateUpdater.Infrastructure/Services/ExchangeRateProvider.cs

@@ -0,0 +1,55 @@
+using ExchangeRateUpdater.Domain.Entities;
+using ExchangeRateUpdater.Domain.Shared;
+using ExchangeRateUpdater.Domain.ValueObjects;
+using ExchangeRateUpdater.Infrastructure.Configuration;
+using ExchangeRateUpdater.Infrastructure.Extensions;
+using LanguageExt;
+using LanguageExt.Common;
+using Microsoft.Extensions.Options;
+using ExchangeRateUpdater.Infrastructure.Services.Interfaces;
+using ExchangeRateUpdater.Infrastructure.Services.Helpers;
+
+namespace ExchangeRateUpdater.Infrastructure.Services
+{
+    public class ExchangeRateProvider(IOptions<Settings> settings, ExchangeRateCacheManager exchangeRateCacheManager) : IExchangeRateProvider
+    {
+        private readonly Settings _settings = settings.Value;
+        private readonly Currency targetCurrency = new(settings.Value.DefaultCurrency);
+        private readonly ExchangeRateCacheManager _cacheManager = exchangeRateCacheManager;
+
+        /// <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 Result<IEnumerable<ExchangeRate>> GetExchangeRates(string scope, string? date = null, string? currency = null, IEnumerable<Currency>? currencies = null)
+        {            
+            if (!ValidationHelper.ValidateDateFormat(scope,ref date, out var formatException) ||
+                !ValidationHelper.ValidateCurrency(currency, out formatException) ||
+                !ValidationHelper.ValidateCurrency(currencies, out formatException))
+                return new(formatException);
+
+            var exchangeRates = _cacheManager.GetDailyRates(date, CurrentUrl(scope, date, currency));
+
+            return exchangeRates.Match<Result<IEnumerable<ExchangeRate>>>(
+                x => x.FilterByCurrencies(currencies).ToExchangeRates(scope, targetCurrency).ToList(),
+                ex => new(ex));
+        }
+
+        /// <summary>
+        /// Constructs the URL to retrieve exchange rates from the source, based on the scope and parameters.
+        /// </summary>
+        /// <param name="scope">The scope or type of exchange rates (e.g., daily, daily-year, daily-currency-month).</param>
+        /// <param name="date">The date or year-month combination for the exchange rate query.</param>
+        /// <param name="currency">The base currency for the query.</param>
+        /// <returns>A formatted URL string that can be used to retrieve exchange rates from the source.</returns>
+        private string CurrentUrl(string scope, string date, string? currency) => scope switch
+        {
+            ExchangeRateRoutes.Daily => $"{_settings.CnbUrl}/{scope}?date={date}",
+            ExchangeRateRoutes.DailyYear => $"{_settings.CnbUrl}/{scope}?year={date}",
+            ExchangeRateRoutes.DailyCurrencyMonth => $"{_settings.CnbUrl}/{scope}?currency={currency}&yearMonth={date}",
+            _ => throw new ArgumentException(),
+        };
+    }
+}