Backend Task - CNB Exchange Rate Provider

.gitignore

@@ -21,3 +21,5 @@
 node_modules
 bower_components
 npm-debug.log
+
+.fake

jobs/Backend/Task/ExchangeRateUpdater/src/Common/TextParsingUtils.cs

@@ -0,0 +1,60 @@
+namespace ExchangeRateUpdater.Common
+{
+    /// <summary>
+    /// Provides static utility methods for parsing text-based data.
+    /// </summary>
+    public static class TextParsingUtils
+    {
+        /// <summary>
+        /// Analyzes a sample of data lines to automatically detect the most likely column delimiter.
+        /// </summary>
+        /// <param name="lines">The collection of all lines from the source file.</param>
+        /// <returns>The detected delimiter character, or ',' as a default fallback.</returns>
+        public static char DetectDelimiter(IEnumerable<string> lines)
+        {
+            var potentialDelimiters = new[] { '|', ',', ';', '\t' };
+            var sampleLines = lines.Where(l => !string.IsNullOrWhiteSpace(l)).Take(10).ToList();
+
+            if (sampleLines.Count < 2)
+            {
+                return ',';
+            }
+
+            var delimiterInfo = potentialDelimiters
+                .Select(d => new
+                {
+                    Delimiter = d,
+                    MostCommonGroup = sampleLines.GroupBy(l => l.Count(c => c == d))
+                                                 .Where(g => g.Key > 0) 
+                                                 .OrderByDescending(g => g.Count()) 
+                                                 .ThenByDescending(g => g.Key) 
+                                                 .Select(g => new { DelimiterCount = g.Key, LineCount = g.Count() })
+                                                 .FirstOrDefault()
+                })
+                .Where(info => info.MostCommonGroup != null && info.MostCommonGroup.LineCount > 1)
+                .OrderByDescending(info => info.MostCommonGroup?.LineCount)
+                .ThenByDescending(info => info.MostCommonGroup?.DelimiterCount)
+                .FirstOrDefault();
+
+            return delimiterInfo?.Delimiter ?? ',';
+        }
+
+        /// <summary>
+        /// Finds the zero-based index of the header row in the data file.
+        /// </summary>
+        /// <param name="lines">The collection of all lines from the source file.</param>
+        /// <param name="delimiter">The delimiter character to look for in the header.</param>
+        /// <returns>The index of the header row, or -1 if not found.</returns>
+        public static int FindHeaderRowIndex(IReadOnlyList<string> lines, char delimiter)
+        {
+            for (int i = 0; i < lines.Count; i++)
+            {
+                if (lines[i].Contains(delimiter))
+                {
+                    return i;
+                }
+            }
+            return -1;
+        }
+    }
+}

jobs/Backend/Task/ExchangeRateUpdater/src/Core/Interfaces/ICnbApiClient.cs

@@ -0,0 +1,14 @@
+namespace ExchangeRateUpdater.Core.Interfaces
+{
+    /// <summary>
+    /// Interface for a client that interacts with the Czech National Bank API to fetch exchange rates.
+    /// </summary>
+    public interface ICnbApiClient
+    {
+        /// <summary>
+        /// Asynchronously retrieves the latest exchange rates from the Czech National Bank API.
+        /// </summary>
+        /// <returns>A task that represents the asynchronous operation, containing the latest exchange rates.</returns>
+        Task<string> GetLatestExchangeRatesAsync();
+    }
+}

jobs/Backend/Task/ExchangeRateUpdater/src/Core/Interfaces/ICnbExchangeRateRepository.cs

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+using ExchangeRateUpdater.Core.Models;
+namespace ExchangeRateUpdater.Core.Interfaces
+{
+    /// <summary>
+    /// Interface for a repository that retrieves exchange rates from the Czech National Bank (CNB) API.
+    /// </summary>
+    public interface ICnbExchangeRateRepository
+    {
+        /// <summary>
+        /// Asynchronously retrieves the latest exchange rates.
+        /// </summary>
+        /// <returns>A collection of <see cref="ExchangeRate"/> objects representing the latest exchange rates.</returns>
+        Task<IEnumerable<ExchangeRate>> GetExchangeRatesAsync();
+
+        /// <summary>
+        /// Asynchronously retrieves specific exchange rates for the given currencies.
+        /// </summary>
+        /// <param name="currencies"></param>
+        /// <returns></returns>
+        Task<IEnumerable<ExchangeRate>> GetSpecificExchangeRatesAsync(IEnumerable<Currency> currencies);
+    }
+}

jobs/Backend/Task/ExchangeRateUpdater/src/Core/Interfaces/IExchangeRateProvider.cs

@@ -0,0 +1,17 @@
+using ExchangeRateUpdater.Core.Models;
+
+namespace ExchangeRateUpdater.Core.Interfaces
+{
+    /// <summary>
+    /// Provides functionality to retrieve exchange rates for specified currencies.
+    /// </summary>
+    public interface IExchangeRateProvider
+    {
+        /// <summary>
+        /// Gets exchange rates for the specified currencies.
+        /// </summary>
+        /// <param name="currencies">Collection of currencies to get exchange rates for.</param>
+        /// <returns>Collection of exchange rates for the specified currencies.</returns>
+        Task<IEnumerable<ExchangeRate>> GetExchangeRatesAsync(IEnumerable<Currency> currencies);
+    }
+}

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

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+namespace ExchangeRateUpdater.Core.Models
+{
+    /// <summary>
+    /// Represents a currency.
+    /// </summary>
+    public class Currency
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Currency"/> class.
+        /// </summary>
+        /// <param name="code">The three-letter ISO 4217 code of the currency.</param>
+        /// <exception cref="ArgumentException"></exception>
+        public Currency(string code)
+        {
+            if (string.IsNullOrWhiteSpace(code))
+            {
+                throw new ArgumentException("Currency code cannot be null or empty.", nameof(code));
+            }
+            Code = code.ToUpperInvariant();
+        }
+
+        /// <summary>
+        /// Three-letter ISO 4217 code of the currency.
+        /// </summary>
+        public string Code { get; }
+
+        /// <summary>
+        /// Overrides the ToString method to return the currency code.
+        /// </summary>
+        /// <returns>The currency code.</returns>
+        public override string ToString()
+        {
+            return Code;
+        }
+
+        /// <summary>
+        /// Determines whether the specified object is equal to the current currency.
+        /// </summary>
+        /// <param name="obj">The object to compare with the current currency.</param>
+        /// <returns>true if the specified object is equal to the current currency; otherwise, false.</returns>
+        public override bool Equals(object? obj)
+        {
+            return obj is Currency currency && Code == currency.Code;
+        }
+
+        /// <summary>
+        /// Generates a hash code for the current currency.
+        /// </summary>
+        /// <returns>A hash code for the current currency.</returns>
+        public override int GetHashCode()
+        {
+            return HashCode.Combine(Code);
+        }
+
+        /// <summary>
+        /// Overloaded equality operator to compare two Currency objects.
+        /// </summary>
+        /// <param name="left">The first Currency object to compare.</param>
+        /// <param name="right">The second Currency object to compare.</param>
+        /// <returns>true if both Currency objects are equal; otherwise, false.</returns>
+        public static bool operator ==(Currency? left, Currency? right)
+        {
+            return EqualityComparer<Currency>.Default.Equals(left, right);
+        }
+
+        /// <summary>
+        /// Overloaded inequality operator to compare two Currency objects.
+        /// </summary>
+        /// <param name="left">The first Currency object to compare.</param>
+        /// <param name="right">The second Currency object to compare.</param>
+        /// <returns>true if both Currency objects are not equal; otherwise, false.</returns>
+        public static bool operator !=(Currency? left, Currency? right)
+        {
+            return !(left == right);
+        }
+    }
+}