Import StringProtectionExtensions (#223)

src/Tingle.Extensions.Primitives/Extensions/StringProtectionExtensions.cs

@@ -0,0 +1,61 @@
+namespace System;
+
+/// <summary>
+/// Specifies the position to apply protection in <see cref="string"/> objects.
+/// </summary>
+public enum StringProtectionPosition
+{
+    /// <summary>
+    /// Protect the start. Example result: <c>**********dttJAsQVU</c>
+    /// </summary>
+    Start,
+
+    /// <summary>
+    /// Protect the middle. Example result: <c>e0gNH**********AsQVU</c>
+    /// </summary>
+    Middle,
+
+    /// <summary>
+    /// Protect the end. Example result: <c>e0gNHBa90**********</c>
+    /// </summary>
+    End,
+}
+
+/// <summary>Extension methods for <see cref="string"/>.</summary>
+public static partial class StringProtectionExtensions
+{
+    /// <summary>
+    /// Protect a value such as an authentication key. Useful before serialization
+    /// </summary>
+    /// <param name="input"></param>
+    /// <param name="toKeep"></param>
+    /// <param name="position"></param>
+    /// <param name="replacementChar"></param>
+    /// <param name="replacementLength"></param>
+    /// <returns></returns>
+    public static string Protect(this string input,
+                                 float toKeep = 0.2f, /* 20% is a good rule of thumb */
+                                 StringProtectionPosition position = StringProtectionPosition.End,
+                                 char replacementChar = '*',
+                                 int? replacementLength = null)
+    {
+        ArgumentNullException.ThrowIfNull(input);
+
+        var lengthToKeep = Convert.ToInt32(input.Length * toKeep); // consider a minimum
+        var lengthToKeepHalf = lengthToKeep / 2;
+        var lengthToReplace = input.Length - (lengthToKeepHalf * 2);
+        if (replacementLength is not null)
+        {
+            replacementLength = replacementLength <= 0 ? input.Length : replacementLength;
+            lengthToReplace = Math.Min(replacementLength.Value, lengthToReplace);
+        }
+        var totalWidth = Math.Min(input.Length, lengthToKeep + lengthToReplace);
+        return position switch
+        {
+            StringProtectionPosition.Start => input[^lengthToKeep..].PadLeft(totalWidth, replacementChar),
+            StringProtectionPosition.End => input[..lengthToKeep].PadRight(totalWidth, replacementChar),
+            StringProtectionPosition.Middle => input[..lengthToKeepHalf] + new string(replacementChar, lengthToReplace) + input[^lengthToKeepHalf..],
+            _ => throw new NotSupportedException($"'{nameof(StringProtectionPosition)}.{position}' is not yet supported."),
+        };
+    }
+}

tests/Tingle.Extensions.Primitives.Tests/Extensions/StringProtectionExtensionsTests.cs

@@ -0,0 +1,52 @@
+namespace Tingle.Extensions.Modeling.Tests;
+
+public class StringProtectionExtensionsTests
+{
+    [Theory]
+    [InlineData("EcsmGa/wXv/HlA==", "Ecs*************")]
+    [InlineData("U6G0be/Q5wR1nExscY6Rfg==", "U6G0b*******************")]
+    [InlineData("e0gNHBa90CfdKbtcWgksn52cvXoXMqCTaLdttJAsQVU=", "e0gNHBa90***********************************")]
+    public void Protect_Works(string original, string expected)
+    {
+        Assert.Equal(expected, original.Protect());
+    }
+
+    [Theory]
+    [InlineData("EcsmGa/wXv/HlA==", "Ecs*************", 0.2f)]
+    [InlineData("U6G0be/Q5wR1nExscY6Rfg==", "U6G0b*******************", 0.2f)]
+    [InlineData("e0gNHBa90CfdKbtcWgksn52cvXoXMqCTaLdttJAsQVU=", "e0gNHBa90***********************************", 0.2f)]
+    [InlineData("e0gNHBa90CfdKbtcWgksn52cvXoXMqCTaLdttJAsQVU=", "e0gNHBa90CfdKbtcWg**************************", 0.4f)]
+    public void Protect_Works_Respects_Fraction(string original, string expected, float fraction)
+    {
+        Assert.Equal(expected, original.Protect(toKeep: fraction));
+    }
+
+    [Theory]
+    [InlineData("e0gNHBa90CfdKbtcWgksn52cvXoXMqCTaLdttJAsQVU=", "e0gNHBa90***********************************", StringProtectionPosition.End)]
+    [InlineData("e0gNHBa90CfdKbtcWgksn52cvXoXMqCTaLdttJAsQVU=", "***********************************ttJAsQVU=", StringProtectionPosition.Start)]
+    [InlineData("e0gNHBa90CfdKbtcWgksn52cvXoXMqCTaLdttJAsQVU=", "e0gN************************************QVU=", StringProtectionPosition.Middle)]
+    public void Protect_Respects_Position(string original, string expected, StringProtectionPosition position)
+    {
+        Assert.Equal(expected, original.Protect(position: position));
+    }
+
+    [Theory]
+    [InlineData("e0gNHBa90CfdKbtcWgksn52cvXoXMqCTaLdttJAsQVU=", "e0gNHBa90***********************************", '*')]
+    [InlineData("e0gNHBa90CfdKbtcWgksn52cvXoXMqCTaLdttJAsQVU=", "e0gNHBa90xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx", 'x')]
+    [InlineData("e0gNHBa90CfdKbtcWgksn52cvXoXMqCTaLdttJAsQVU=", "e0gNHBa90-----------------------------------", '-')]
+    [InlineData("e0gNHBa90CfdKbtcWgksn52cvXoXMqCTaLdttJAsQVU=", "e0gNHBa90$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$", '$')]
+    public void Protect_Respects_ReplacementChar(string original, string expected, char replacementChar)
+    {
+        Assert.Equal(expected, original.Protect(replacementChar: replacementChar));
+    }
+
+    [Theory]
+    [InlineData("e0gNHBa90CfdKbtcWgksn52cvXoXMqCTaLdttJAsQVU=", "e0gNHBa90***********************************", null)]
+    [InlineData("e0gNHBa90CfdKbtcWgksn52cvXoXMqCTaLdttJAsQVU=", "e0gNHBa90***********************************", 44)]
+    [InlineData("e0gNHBa90CfdKbtcWgksn52cvXoXMqCTaLdttJAsQVU=", "e0gNHBa90*****", 5)]
+    [InlineData("e0gNHBa90CfdKbtcWgksn52cvXoXMqCTaLdttJAsQVU=", "e0gNHBa90***********************************", 0)]
+    public void Protect_Respects_ReplacementLength(string original, string expected, int? replacementLength)
+    {
+        Assert.Equal(expected, original.Protect(replacementLength: replacementLength));
+    }
+}