fix: anchor Email regex to prevent substring matching & perf: optimize RemoveCharacters via SearchValues

Benchmarks/Benchmark.cs

@@ -1,4 +1,5 @@
-using Benchmark;
+using System.Buffers;
+using Benchmark;
 using BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Configs;
 using BenchmarkDotNet.Running;
@@ -19,20 +20,49 @@ namespace Benchmark
     public class StringExtensionBenchmark
     {
         private readonly string input = "hello world!";
+        private readonly string longInput = string.Concat(Enumerable.Repeat("hello world! ", 100));
         private readonly char[] charactersToRemove = { 'l', 'o' };
+        private readonly SearchValues<char> searchValues = SearchValues.Create('l', 'o');
         private readonly string substring = "l";
         private readonly string phoneNumber = "555-555-5555";
         private readonly string email = "john.doe@example.com";
 
         /// <summary>
-        /// Benchmark for the RemoveCharacters method.
+        /// Benchmark for the RemoveCharacters method with char[].
         /// </summary>
         [Benchmark]
-        public string? RemoveCharacters()
+        public string? RemoveCharacters_CharArray()
         {
             return input.RemoveCharacters(charactersToRemove);
         }
 
+        /// <summary>
+        /// Benchmark for the RemoveCharacters method with SearchValues.
+        /// </summary>
+        [Benchmark]
+        public string? RemoveCharacters_SearchValues()
+        {
+            return input.RemoveCharacters(searchValues);
+        }
+
+        /// <summary>
+        /// Benchmark for the RemoveCharacters method on long input with char[].
+        /// </summary>
+        [Benchmark]
+        public string? RemoveCharacters_Long_CharArray()
+        {
+            return longInput.RemoveCharacters(charactersToRemove);
+        }
+
+        /// <summary>
+        /// Benchmark for the RemoveCharacters method on long input with SearchValues.
+        /// </summary>
+        [Benchmark]
+        public string? RemoveCharacters_Long_SearchValues()
+        {
+            return longInput.RemoveCharacters(searchValues);
+        }
+
         /// <summary>
         /// Benchmark for the IsValidEmail method.
         /// </summary>

StringExtension/StringExtension.cs

@@ -1,4 +1,4 @@
-using System.Buffers;
+using System.Buffers;
 using StringExtension.Internal;
 
 namespace StringExtension;
@@ -65,6 +65,84 @@ public static string RemoveCharacters(this ReadOnlySpan<char> input, ReadOnlySpa
         }
     }
 
+    /// <summary>
+    /// Removes specified characters from the given string using a <see cref="SearchValues{T}"/> set.
+    /// </summary>
+    /// <param name="input">The input string.</param>
+    /// <param name="searchValues">The set of characters to remove.</param>
+    /// <returns>A new string with specified characters removed.</returns>
+    /// <remarks>Returns <see langword="null"/> if <paramref name="input"/> is <see langword="null"/>.</remarks>
+    public static string? RemoveCharacters(this string? input, SearchValues<char>? searchValues)
+    {
+        if (string.IsNullOrEmpty(input) || searchValues is null)
+        {
+            return input;
+        }
+
+        return input.AsSpan().RemoveCharacters(searchValues);
+    }
+
+    /// <summary>
+    /// Removes specified characters from the given span of characters using a <see cref="SearchValues{T}"/> set.
+    /// </summary>
+    /// <param name="input">The input characters.</param>
+    /// <param name="searchValues">The set of characters to remove.</param>
+    /// <returns>A new string with specified characters removed.</returns>
+    public static string RemoveCharacters(this ReadOnlySpan<char> input, SearchValues<char>? searchValues)
+    {
+        if (input.IsEmpty || searchValues is null)
+        {
+            return input.ToString();
+        }
+
+        var firstIndex = input.IndexOfAny(searchValues);
+        if (firstIndex < 0)
+        {
+            return input.ToString();
+        }
+
+        char[]? pooledBuffer = null;
+        var buffer = (uint)input.Length <= BufferLimits.StackAllocThreshold
+            ? stackalloc char[input.Length]
+            : pooledBuffer = ArrayPool<char>.Shared.Rent(input.Length);
+
+        try
+        {
+            input[..firstIndex].CopyTo(buffer);
+            var destinationIndex = firstIndex;
+            var remainder = input[firstIndex..];
+
+            while (true)
+            {
+                remainder = remainder[1..];
+
+                var nextMatch = remainder.IndexOfAny(searchValues);
+                if (nextMatch < 0)
+                {
+                    remainder.CopyTo(buffer[destinationIndex..]);
+                    destinationIndex += remainder.Length;
+                    break;
+                }
+
+                if (nextMatch > 0)
+                {
+                    remainder[..nextMatch].CopyTo(buffer[destinationIndex..]);
+                    destinationIndex += nextMatch;
+                    remainder = remainder[nextMatch..];
+                }
+            }
+
+            return new string(buffer[..destinationIndex]);
+        }
+        finally
+        {
+            if (pooledBuffer is not null)
+            {
+                ArrayPool<char>.Shared.Return(pooledBuffer);
+            }
+        }
+    }
+
     /// <summary>
     /// Counts the number of occurrences of a substring in the given string.
     /// </summary>

StringExtension/Validation/Validation.cs

@@ -11,7 +11,7 @@ public static partial class Validation
     /// Represents a regular expression that can be used to validate an email address.
     /// </summary>
     /// <returns>A regular expression that can be used to validate an email address.</returns>
-    [GeneratedRegex(@"[^@ \t\r\n]+@[^@ \t\r\n]+\.[^@ \t\r\n]+")]
+    [GeneratedRegex(@"^[^@ \t\r\n]+@[^@ \t\r\n]+\.[^@ \t\r\n]+$")]
     private static partial Regex MailAddressRegex();
 
     /// <summary>

UnitTests/StringExtensionTests.cs

@@ -1,3 +1,4 @@
+using System.Buffers;
 using StringExtension;
 using StringExtension.Casing;
 using StringExtension.Linguistics;
@@ -23,6 +24,32 @@ public void TestRemoveCharacters()
         Assert.That(result, Is.EqualTo(expected));
     }
 
+    /// <summary>
+    /// Tests the RemoveCharacters method with SearchValues.
+    /// </summary>
+    [Test]
+    public void TestRemoveCharacters_SearchValues()
+    {
+        var input = "hello world!";
+        var searchValues = SearchValues.Create('l', 'o');
+        var expected = "he wrd!";
+        var result = input.RemoveCharacters(searchValues);
+        Assert.That(result, Is.EqualTo(expected));
+    }
+
+    /// <summary>
+    /// Tests the ReadOnlySpan overload of RemoveCharacters with SearchValues.
+    /// </summary>
+    [Test]
+    public void TestRemoveCharacters_SearchValues_Span()
+    {
+        ReadOnlySpan<char> input = "hello world!";
+        var searchValues = SearchValues.Create('l', 'o');
+        var expected = "he wrd!";
+        var result = input.RemoveCharacters(searchValues);
+Assert.That(result, Is.EqualTo(expected));
+    }
+
     /// <summary>
     /// Tests that RemoveCharacters handles a null input gracefully.
     /// </summary>
@@ -59,6 +86,21 @@ public void TestIsValidEmail()
         Assert.That(result, Is.True);
     }
 
+    /// <summary>
+    /// Tests that IsValidEmail rejects strings that only contain an email as a substring.
+    /// </summary>
+    [Test]
+    public void TestIsValidEmail_InvalidSubstrings()
+    {
+        string emailWithPrefix = "hello john.doe@example.com";
+        string emailWithSuffix = "john.doe@example.com world";
+        string emailInSentence = "contact john.doe@example.com for info";
+
+        Assert.That(emailWithPrefix.IsValidEmail(), Is.False);
+        Assert.That(emailWithSuffix.IsValidEmail(), Is.False);
+        Assert.That(emailInSentence.IsValidEmail(), Is.False);
+    }
+
     /// <summary>
     /// Tests the IsValidPhoneNumber method.
     /// </summary>