adding_maybe_class

src/ByteDecoder.Common.Tests/Fakes/FileStorage.cs

@@ -0,0 +1,44 @@
+using System;
+using System.IO;
+
+namespace ByteDecoder.Common.Tests.Fakes;
+
+/// <summary>
+/// Example of usage:
+/// var message = fileStorage.Read(49).DefaultIfEmpty("").Single();
+/// This fake is designed under CQS principle (Command Query Separation Principle),
+/// Postel's Law, Fail Fast concept and Maybe idiom.
+/// </summary>
+internal class FileStorage
+{
+    public FileStorage(string workingDirectory)
+    {
+        if (workingDirectory is null)
+            throw new ArgumentNullException(nameof(workingDirectory));
+        if (!Directory.Exists(workingDirectory))
+            throw new ArgumentException("BOo", nameof(workingDirectory));
+
+        WorkingDirectory = workingDirectory;
+    }
+
+    public string WorkingDirectory { get; }
+
+    public void Save(int id, string message)
+    {
+        var path = this.GetFileName(id);
+        File.WriteAllText(path, message);
+    }
+
+    public Maybe<string> Read(int id)
+    {
+        var path = this.GetFileName(id);
+        if (!File.Exists(path))
+            return new Maybe<string>();
+
+        var message = File.ReadAllText(path);
+        return new Maybe<string>(message);
+    }
+
+    public string GetFileName(int id) =>
+        Path.Combine(this.WorkingDirectory, id + ".txt");
+}

src/ByteDecoder.Common/Maybe.cs

@@ -0,0 +1,42 @@
+using System.Collections;
+
+namespace ByteDecoder.Common;
+
+/// <summary>
+/// Alternative to Tester/Doer and TryRead idioms to handle outputs.
+/// Internally holds 0 or 1 element.
+/// </summary>
+/// <typeparam name="T"></typeparam>
+public class Maybe<T> : IEnumerable<T>
+{
+    private readonly IEnumerable<T> _values;
+
+    /// <summary>
+    ///
+    /// </summary>
+    public Maybe()
+    {
+        _values = new T[0];
+    }
+
+    /// <summary>
+    ///
+    /// </summary>
+    /// <param name="value"></param>
+    public Maybe(T value)
+    {
+        _values = new[] { value };
+    }
+
+    /// <summary>
+    ///
+    /// </summary>
+    /// <returns></returns>
+    public IEnumerator<T> GetEnumerator() => _values.GetEnumerator();
+
+    /// <summary>
+    ///
+    /// </summary>
+    /// <returns></returns>
+    IEnumerator IEnumerable.GetEnumerator() => this.GetEnumerator();
+}