[ExchangeRateProvider]:: ExchangeRateProvider service implementation

jobs/Backend/Task/ExchangeRateProvider.cs

@@ -1,10 +1,23 @@
-using System.Collections.Generic;
+using ExchangeRateProvider.Models;
+using ExchangeRateUpdater.Interfaces;
+using System;
+using System.Collections.Generic;
 using System.Linq;
 
 namespace ExchangeRateUpdater
 {
-    public class ExchangeRateProvider
-    {
+    public class ExchangeRateProvider : IExchangeRateProvider
+    {/// <summary>
+     /// The data source to fetch exchange rates from.
+     /// </summary>
+        private BaseExchangeDataSource _exchangeDataSource;
+
+
+        public ExchangeRateProvider(BaseExchangeDataSource baseExchangeDataSource)
+        {
+            _exchangeDataSource = baseExchangeDataSource;
+        }
+
         /// <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",
@@ -13,7 +26,25 @@ public class ExchangeRateProvider
         /// </summary>
         public IEnumerable<ExchangeRate> GetExchangeRates(IEnumerable<Currency> currencies)
         {
-            return Enumerable.Empty<ExchangeRate>();
+            try
+            {
+                var textFormatUrl = _exchangeDataSource.GetExchangeRateDatasetUrl();
+
+                var readerService = ExchangeDataSourceReaderFactory.CreateDataSourceReader(_exchangeDataSource.DataSourceType);
+                // Fetch and parse the data
+                var exchangeRates = readerService.FetchAndParseExchangeRatesAsync(_exchangeDataSource)
+                    .GetAwaiter()
+                    .GetResult();
+
+                // Filter the exchange rates based on the specified currencies
+                return exchangeRates.Where(rate =>
+                    currencies.Any(c => c.Code == rate.TargetCurrency.Code));
+            }
+            catch (Exception ex)
+            {
+                // return a specific error
+                throw new Exception("An error occurred while fetching exchange rates.", ex);
+            }
         }
     }
 }

jobs/Backend/Task/ExchangeRateUpdater.csproj

@@ -5,4 +5,8 @@
     <TargetFramework>net6.0</TargetFramework>
   </PropertyGroup>
 
+  <ItemGroup>
+    <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="9.0.0" />
+  </ItemGroup>
+
 </Project>

jobs/Backend/Task/Interfaces/IExchangeDataSourceFactory.cs

@@ -0,0 +1,9 @@
+using ExchangeRateProvider.Models;
+
+namespace ExchangeRateUpdater.Interfaces
+{
+    public interface IExchangeDataSourceFactory
+    {
+        public BaseExchangeDataSource CreateDataSource(ExchangeRateDataSourceType dataSourceType);
+    }
+}

jobs/Backend/Task/Interfaces/IExchangeRateProvider.cs

@@ -0,0 +1,9 @@
+using System.Collections.Generic;
+
+namespace ExchangeRateUpdater.Interfaces
+{
+    public interface IExchangeRateProvider
+    {
+        public IEnumerable<ExchangeRate> GetExchangeRates(IEnumerable<Currency> currencies);
+    }
+}

jobs/Backend/Task/Models/BaseExchangeDataSource.cs

@@ -0,0 +1,34 @@
+namespace ExchangeRateProvider.Models
+{
+    public abstract class BaseExchangeDataSource
+    {
+        /// <summary>
+        /// The source currency code.
+        /// </summary>
+        public abstract SourceCurrencyCode SourceCurrencyCode { get; }
+
+        /// <summary>
+        /// The type of the exchange rate data source.
+        /// </summary>
+        public abstract ExchangeRateDataSourceType DataSourceType { get; }
+
+        /// <summary>
+        /// The URL to connect to the exchange rate data source.
+        /// </summary>
+        public abstract string ConnectionUrl { get; }
+
+        /// <summary>
+        /// Returns the URL to fetch the exchange rate dataset.
+        /// </summary>
+        /// <returns></returns>
+        public abstract string GetExchangeRateDatasetUrl();
+    }
+
+    /// <summary>
+    /// The source currency code.
+    /// </summary>
+    public enum SourceCurrencyCode
+    {
+        CZK = 1
+    }
+}

jobs/Backend/Task/Models/CnbExchangeRateDataSource.cs

@@ -0,0 +1,68 @@
+using System;
+
+namespace ExchangeRateProvider.Models
+{
+    public class CnbExchangeRateDataSource : BaseExchangeDataSource
+    {
+        /// <summary>
+        /// The base URL of the exchange rate data source.
+        /// </summary>
+        private const string BaseUrl = "https://www.cnb.cz";
+
+        /// <summary>
+        /// The URL path to fetch the exchange rate dataset.
+        /// </summary>
+        private const string DailyTextUrl = "/en/financial-markets/foreign-exchange-market/central-bank-exchange-rate-fixing/central-bank-exchange-rate-fixing/daily.txt";
+
+        /// <summary>
+        /// The date of the exchange rate. Default is today.
+        /// </summary>
+        private DateTime _exchangeRateDate;
+
+        /// <summary>
+        /// The date format.
+        /// </summary>
+        private string DATE_FORMAT = "dd.MM.yyyy";
+
+        /// <summary>
+        /// The type of the exchange rate data source.
+        /// </summary>
+        public override ExchangeRateDataSourceType DataSourceType => ExchangeRateDataSourceType.Cnb;
+
+        /// <summary>
+        /// The URL to connect to the exchange rate data source.
+        /// </summary>
+        public override string ConnectionUrl => $"{BaseUrl}{DailyTextUrl}";
+
+        /// <summary>
+        /// The date of the exchange rate.
+        /// </summary>
+        public DateTime ExchangeRateDate { get => _exchangeRateDate; set => _exchangeRateDate = value; }
+
+        /// <summary>
+        /// The source currency code.
+        /// </summary>
+        public override SourceCurrencyCode SourceCurrencyCode => SourceCurrencyCode.CZK;
+
+
+        public CnbExchangeRateDataSource(DateTime? exchangeRateDate = null) : base()
+        {
+            ExchangeRateDate = exchangeRateDate ?? DateTime.UtcNow;
+        }
+
+        /// <summary>
+        /// Returns the URL to fetch the exchange rate dataset.
+        /// </summary>
+        /// <returns></returns>
+        public override string GetExchangeRateDatasetUrl()
+        {
+            var formattedDate = ExchangeRateDate.ToString(DATE_FORMAT);
+            return $"{ConnectionUrl}?date={formattedDate}";
+        }
+
+        public override string ToString()
+        {
+            return "Czech National Bank (CNB)";
+        }
+    }
+}

jobs/Backend/Task/Models/ExchangeDataSourceFactory.cs

@@ -0,0 +1,33 @@
+using ExchangeRateUpdater.Interfaces;
+using System;
+
+namespace ExchangeRateProvider.Models
+{
+    public class ExchangeDataSourceFactory : IExchangeDataSourceFactory
+    {
+        /// <summary>
+        /// Creates a new instance of the exchange rate data source.
+        /// </summary>
+        /// <param name="dataSourceType"></param>
+        /// <returns></returns>
+        /// <exception cref="NotSupportedException"></exception>
+        public BaseExchangeDataSource CreateDataSource(ExchangeRateDataSourceType dataSourceType)
+        {
+            switch (dataSourceType)
+            {
+                case ExchangeRateDataSourceType.Cnb:
+                    return new CnbExchangeRateDataSource();
+                default:
+                    throw new NotSupportedException($"Data source type '{dataSourceType}' is not supported.");
+            }
+        }
+    }
+
+    /// <summary>
+    /// The type of the exchange rate data source.
+    /// </summary>
+    public enum ExchangeRateDataSourceType
+    {
+        Cnb = 1
+    }
+}

jobs/Backend/Task/Models/ExchangeDataSourceReaderFactory.cs

@@ -0,0 +1,22 @@
+using ExchangeRateProvider.Services;
+using System;
+
+namespace ExchangeRateProvider.Models
+{
+    /// <summary>
+    /// The factory for creating the exchange rate data source reader.
+    /// </summary>
+    public class ExchangeDataSourceReaderFactory
+    {
+        public static BaseExchangeDataSourceReader CreateDataSourceReader(ExchangeRateDataSourceType dataSourceType)
+        {
+            switch (dataSourceType)
+            {
+                case ExchangeRateDataSourceType.Cnb:
+                    return new CnbExchangeDataSourceReader();
+                default:
+                    throw new NotSupportedException($"Data source type '{dataSourceType}' is not supported.");
+            }
+        }
+    }
+}

jobs/Backend/Task/Program.cs

@@ -1,4 +1,7 @@
-using System;
+using ExchangeRateProvider.Models;
+using ExchangeRateUpdater.Interfaces;
+using Microsoft.Extensions.DependencyInjection;
+using System;
 using System.Collections.Generic;
 using System.Linq;
 
@@ -23,7 +26,20 @@ public static void Main(string[] args)
         {
             try
             {
-                var provider = new ExchangeRateProvider();
+                var serviceCollection = new ServiceCollection();
+
+                serviceCollection.AddTransient<IExchangeDataSourceFactory, ExchangeDataSourceFactory>();
+                serviceCollection.AddTransient<IExchangeRateProvider>(provider =>
+                {
+                    var factory = provider.GetRequiredService<IExchangeDataSourceFactory>();
+                    return new ExchangeRateProvider(factory.CreateDataSource(ExchangeRateDataSourceType.Cnb));
+
+                });
+
+                var serviceProvider = serviceCollection.BuildServiceProvider();
+
+                var provider = serviceProvider.GetRequiredService<IExchangeRateProvider>();
+
                 var rates = provider.GetExchangeRates(currencies);
 
                 Console.WriteLine($"Successfully retrieved {rates.Count()} exchange rates:");
@@ -32,6 +48,10 @@ public static void Main(string[] args)
                     Console.WriteLine(rate.ToString());
                 }
             }
+            catch (NotSupportedException e)
+            {
+                Console.WriteLine($"Could not create data source: '{e.Message}'.");
+            }
             catch (Exception e)
             {
                 Console.WriteLine($"Could not retrieve exchange rates: '{e.Message}'.");

jobs/Backend/Task/Services/BaseExchangeDataSourceReader.cs

@@ -0,0 +1,23 @@
+using ExchangeRateProvider.Models;
+using ExchangeRateUpdater;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+
+namespace ExchangeRateProvider.Services
+{
+    public abstract class BaseExchangeDataSourceReader
+    {
+        /// <summary>
+        /// Fetches and parses the exchange rates from the data source.
+        /// </summary>
+        protected BaseExchangeDataSource _baseExchangeDataSource;
+
+        /// <summary>
+        /// Fetches and parses the exchange rates from the data source.
+        /// </summary>
+        /// <param name="baseExchangeDataSource"></param>
+        /// <returns></returns>
+        public abstract Task<List<ExchangeRate>> FetchAndParseExchangeRatesAsync(BaseExchangeDataSource baseExchangeDataSource);
+
+    }
+}

jobs/Backend/Task/Services/CnbExchangeDataSourceReader.cs

@@ -0,0 +1,58 @@
+using ExchangeRateProvider.Models;
+using ExchangeRateUpdater;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Net.Http;
+using System.Threading.Tasks;
+
+namespace ExchangeRateProvider.Services
+{
+    public class CnbExchangeDataSourceReader : BaseExchangeDataSourceReader
+    {
+        /// <summary>
+        /// Fetches and parses the exchange rates from the data source.
+        /// </summary>
+        /// <param name="baseExchangeDataSource"></param>
+        /// <returns></returns>
+        public override async Task<List<ExchangeRate>> FetchAndParseExchangeRatesAsync(BaseExchangeDataSource baseExchangeDataSource)
+        {
+            _baseExchangeDataSource = baseExchangeDataSource;
+
+            var httpClient = new HttpClient();
+            var response = await httpClient.GetStringAsync(baseExchangeDataSource.GetExchangeRateDatasetUrl());
+
+            return ParseExchangeRates(response);
+        }
+
+        /// <summary>
+        /// Parses the exchange rates from the text data.
+        /// </summary>
+        /// <param name="textData"></param>
+        /// <returns></returns>
+        private List<ExchangeRate> ParseExchangeRates(string textData)
+        {
+            var exchangeRates = new List<ExchangeRate>();
+            var lines = textData.Split(new[] { '\n' }, StringSplitOptions.RemoveEmptyEntries);
+
+
+            // Skip the first two lines (date and header)
+            foreach (var line in lines.Skip(2))
+            {
+                var parts = line.Split('|');
+                if (parts.Length >= 5)
+                {
+                    var currencyCode = parts[3];
+                    var amount = int.Parse(parts[2]); // Amount indicates the base unit (e.g., 100 HUF)
+                    if (decimal.TryParse(parts[4], out var rate))
+                    {
+                        var sourceCurrency = new Currency(_baseExchangeDataSource.SourceCurrencyCode.ToString());
+                        var targetCurrency = new Currency(currencyCode);
+                        exchangeRates.Add(new ExchangeRate(sourceCurrency, targetCurrency, rate / amount));
+                    }
+                }
+            }
+            return exchangeRates;
+        }
+    }
+}