Fix an issue with random grawlix being interpreted as GitHub math exp…

…ressions.
IEvangelist · Feb 16, 2024 · ac3f793 · ac3f793
1 parent 2f2c4e2
commit ac3f793
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Showing 6 changed files with 113 additions and 8 deletions.
diff --git a/src/ProfanityFilter.Services/Extensions/RandomExtensions.cs b/src/ProfanityFilter.Services/Extensions/RandomExtensions.cs
@@ -0,0 +1,27 @@
+// Copyright (c) David Pine. All rights reserved.
+// Licensed under the MIT License.
+
+namespace ProfanityFilter.Services.Extensions;
+
+internal static class RandomExtensions
+{
+    /// <summary>
+    /// Gets a random subset of items from the source array, with the
+    /// specified length, while respecting the limits.
+    /// </summary>
+    internal static TItem[] RandomItemsWithLimitToOne<TItem>(
+        this TItem[] array,
+        int length,
+        TItem limit) where TItem : notnull
+    {
+        var choices = array.Except([limit]).ToArray();
+
+        var items = Random.Shared.GetItems(choices, length);
+
+        var index = Random.Shared.Next(0, items.Length);
+
+        items[index] = limit;
+
+        return items;
+    }
+}
diff --git a/src/ProfanityFilter.Services/Filters/Symbols.cs b/src/ProfanityFilter.Services/Filters/Symbols.cs
@@ -5,19 +5,31 @@ namespace ProfanityFilter.Services.Filters;
 
 internal static class Symbols
 {
+    /// <summary>
+    /// Only permit a single <c>"\$"</c> string within an entire grawlix
+    /// replacement, to avoid GitHub from rendering it as a Math expression.
+    /// </summary>
+    internal const string LimitGrawlixToOne = $"\\{UnescapedLimitGrawlixToOne}";
+
+    /// <summary>
+    /// Only permit a single <c>"$"</c> string within an entire grawlix
+    /// replacement, to avoid GitHub from rendering it as a Math expression.
+    /// </summary>
+    internal const string UnescapedLimitGrawlixToOne = "$";
+
     /// <summary>
     /// An array of hand-selected grawlix replacements for profane words.
     /// See <a href="https://english.stackexchange.com/a/86840/446108"></a>
     /// </summary>
     internal static string[] Grawlixes =
     [
-        new Symbol('#', true),
+        new Symbol('#'),
         new Symbol('$'),
         new Symbol('@'),
-        new Symbol('!', true),
+        new Symbol('!'),
         new Symbol('%'),
         new Symbol('&'),
-        new Symbol('*', true),
+        new Symbol('*'),
         new Symbol('+'),
         new Symbol('?'),
         new Symbol('^'),
@@ -41,7 +53,7 @@ internal static class Symbols
     ];
 }
 
-file readonly record struct Symbol(char Value, bool RequiresEscaping = false)
+file readonly record struct Symbol(char Value, bool Escape = true)
 {
     /// <summary>
     /// Implicitly converts a <see cref="char"/> to a <see cref="Symbol"/>.
@@ -55,6 +67,6 @@ file readonly record struct Symbol(char Value, bool RequiresEscaping = false)
 
     public override string ToString()
     {
-        return RequiresEscaping ? $"\\{Value}" : $"{Value}";
+        return Escape ? $"\\{Value}" : $"{Value}";
     }
 }
diff --git a/src/ProfanityFilter.Services/GlobalUsings.cs b/src/ProfanityFilter.Services/GlobalUsings.cs
@@ -4,12 +4,16 @@
 global using System.Collections.Concurrent;
 global using System.Collections.Frozen;
 global using System.Diagnostics.CodeAnalysis;
+global using System.Runtime.InteropServices;
 global using System.Text;
 global using System.Text.RegularExpressions;
+
 global using Microsoft.Extensions.Caching.Memory;
 global using Microsoft.Extensions.DependencyInjection;
+
 global using Pathological.Globbing.Extensions;
 global using Pathological.Globbing.Options;
+
 global using ProfanityFilter.Services.Extensions;
 global using ProfanityFilter.Services.Filters;
 global using ProfanityFilter.Services.Results;

diff --git a/src/ProfanityFilter.Services/Internals/MatchEvaluators.cs b/src/ProfanityFilter.Services/Internals/MatchEvaluators.cs
@@ -20,8 +20,12 @@ internal static MatchEvaluator GrawlixEvaluator(FilterParameters parameters) =>
 
             var grawlixes = isNotTitle ? Symbols.Grawlixes : Symbols.UnescapedGrawlixes;
 
+            var limit = isNotTitle ? Symbols.LimitGrawlixToOne : Symbols.UnescapedLimitGrawlixToOne;
+
+            var randomGrawlix = grawlixes.RandomItemsWithLimitToOne(match.Length, limit);
+
             var result = string.Join(
-                "", Random.Shared.GetItems(grawlixes, match.Length));
+                "", randomGrawlix);
 
             return result;
         };
@@ -38,9 +42,14 @@ internal static MatchEvaluator BoldGrawlixEvaluator(FilterParameters parameters)
 
             var grawlixes = isNotTitle ? Symbols.Grawlixes : Symbols.UnescapedGrawlixes;
 
+            var limit = isNotTitle ? Symbols.LimitGrawlixToOne : Symbols.UnescapedLimitGrawlixToOne;
+
+            var randomGrawlix = grawlixes.RandomItemsWithLimitToOne(match.Length, limit);
+
             var result = string.Join(
-                "", Random.Shared.GetItems(grawlixes, match.Length));
+                "", randomGrawlix);
 
+            // Titles cannot be bolded
             return isNotTitle ? $"__{result}__" : result;
         };
 

diff --git a/tests/ProfanityFilter.Services.Tests/MatchEvaluatorTests.cs b/tests/ProfanityFilter.Services.Tests/MatchEvaluatorTests.cs
@@ -41,7 +41,7 @@ public void RandomAsteriskEvaluator_Returns_Expected_Result()
     [Fact]
     public void GrawlixEvaluator_Returns_Expected_Result()
     {
-        var input = "swear";
+        var input = "someReallyLongSwearWordOrPhrase";
         var regex = TestRegex();
         var match = regex.Match(input);
         var sut = MatchEvaluators.GrawlixEvaluator;
@@ -50,6 +50,7 @@ public void GrawlixEvaluator_Returns_Expected_Result()
         var actual = sut(parameters).Invoke(match);
 
         Assert.NotEqual(input, actual);
+        Assert.Single(actual.Where(@char => @char is '$'));
     }
 
     [Fact]
@@ -64,6 +65,7 @@ public void BoldGrawlixEvaluator_Returns_Expected_Result()
         var actual = sut(parameters).Invoke(match);
 
         Assert.NotEqual(input, actual);
+        Assert.Single(actual.Where(@char => @char is '$'));
     }
 
     [Fact]

diff --git a/tests/ProfanityFilter.Services.Tests/RandomExtensionsTests.cs b/tests/ProfanityFilter.Services.Tests/RandomExtensionsTests.cs
@@ -0,0 +1,51 @@
+// Copyright (c) David Pine. All rights reserved.
+// Licensed under the MIT License.
+
+namespace ProfanityFilter.Services.Tests;
+
+public class RandomExtensionsTests
+{
+    [Fact]
+    public void RandomItemsWithLimitsReturnsRandomSubsetOfItems()
+    {
+        // Arrange
+        var source = new[] { "a", "b", "c", "d", "e" };
+
+        // Act
+        var result = source.RandomItemsWithLimitToOne(3, "");
+
+        // Assert
+        Assert.Equal(3, result.Length);
+    }
+
+    [Fact]
+    public void RandomItemsWithLimitsRespectsLimits()
+    {
+        // Arrange
+        var source = new[] { "a", "b", "c", "d", "e" };
+
+        // Act
+        var result = source.RandomItemsWithLimitToOne(3, "a");
+
+        // Assert
+        Assert.Equal(3, result.Length);
+        Assert.Single(result.Where(str => str is "a"));
+    }
+
+    [Fact]
+    public void RandomItemsWithLimitsReturnsHugeArrayWithOnlyOneLimitedValue()
+    {
+        // Arrange
+        var source = new[] { "a", "b", "c", "d", "e" };
+
+        // Act
+        var result = source.RandomItemsWithLimitToOne(100_000, "c");
+
+        // Assert
+        Assert.Contains(result, str => str is "a");
+        Assert.Contains(result, str => str is "b");
+        Assert.Single(result.Where(str => str is "c"));
+        Assert.Contains(result, str => str is "d");
+        Assert.Contains(result, str => str is "e");
+    }
+}