Clean-up Project GUID generation code

src/Buildalyzer/AnalyzerResult.cs

@@ -35,7 +35,7 @@
         if (string.IsNullOrEmpty(projectGuid) || !Guid.TryParse(projectGuid, out _projectGuid))
         {
             _projectGuid = analyzer == null
-                ? GuidUtility.Create(GuidUtility.UrlNamespace, ProjectFilePath)
+                ? Buildalyzer.ProjectGuid.Create(ProjectFilePath)
                 : analyzer.ProjectGuid;
         }
     }
@@ -156,13 +156,13 @@
     internal void ProcessProject(PropertiesAndItems propertiesAndItems)
     {
         // Add properties
         foreach (var entry in propertiesAndItems.Properties)
         {
             _properties[entry.Key] = entry.StringValue;
         }
 
         // Add items
         foreach (var items in propertiesAndItems.Items)
         {
             _items[items.Key] = items.Values.Select(task => new ProjectItem(task)).ToArray();
         }

src/Buildalyzer/ProjectAnalyzer.cs

@@ -64,7 +64,7 @@ internal ProjectAnalyzer(AnalyzerManager manager, string projectFilePath, Projec
 
         // Get (or create) a project GUID
         ProjectGuid = projectInSolution == null
-            ? GuidUtility.Create(GuidUtility.UrlNamespace, ProjectFile.Name)
+            ? Buildalyzer.ProjectGuid.Create(ProjectFile.Name)
             : Guid.Parse(projectInSolution.ProjectGuid);
 
         // Set the solution directory global property

src/Buildalyzer/ProjectGuid.cs

@@ -0,0 +1,57 @@
+#nullable enable
+
+using System.Security.Cryptography;
+
+namespace Buildalyzer;
+
+/// <summary>Generates Project <see cref="Guid"/>'s.</summary>
+/// <remarks>
+/// See: https://datatracker.ietf.org/doc/html/rfc4122.
+/// </remarks>
+internal static class ProjectGuid
+{
+    /// <summary>The namespace for URL's.</summary>
+    private static readonly Guid UrlNamespace = Guid.Parse("6ba7b811-9dad-11d1-80b4-00c04fd430c8");
+
+    /// <summary>Generates a <see cref="Guid"/> based on the <see cref="SHA1"/> hash of the name.</summary>
+    public static Guid Create(string? name)
+    {
+        byte[] guid = Hash(Encoding.UTF8.GetBytes(name ?? string.Empty));
+
+        // set the four most significant bits (bits 12 through 15) of the time_hi_and_version field to the appropriate 4-bit version number from Section 4.1.3 (step 8)
+        guid[6] = (byte)((guid[6] & 0x0F) | 0x50);
+
+        // set the two most significant bits (bits 6 and 7) of the clock_seq_hi_and_reserved to zero and one, respectively (step 10)
+        guid[8] = (byte)((guid[8] & 0x3F) | 0x80);
+
+        // convert the resulting UUID to local byte order (step 13)
+        SwapBytes(guid);
+        return new Guid(guid);
+    }
+
+    /// <summary>Generates a <see cref="SHA1"/> hash.</summary>
+    [Pure]
+    private static byte[] Hash(byte[] bytes)
+    {
+       // convert the namespace UUID to network order (step 3)
+        var ns = UrlNamespace.ToByteArray();
+        SwapBytes(ns);
+
+        // compute the hash of the name space ID concatenated with the name (step 4)
+        using var sha1 = SHA1.Create();
+        sha1.TransformBlock(ns, 0, ns.Length, null, 0);
+        sha1.TransformFinalBlock(bytes, 0, bytes.Length);
+        return sha1.Hash![..16];
+    }
+
+    /// <summary>Converts a GUID (expressed as a byte array) to/from network order (MSB-first).</summary>
+    private static void SwapBytes(byte[] bytes)
+    {
+        Swap(bytes, 0, 3);
+        Swap(bytes, 1, 2);
+        Swap(bytes, 4, 5);
+        Swap(bytes, 6, 7);
+
+        static void Swap(byte[] bs, int l, int r) => (bs[r], bs[l]) = (bs[l], bs[r]);
+    }
+}

tests/Buildalyzer.Tests/Project_GUID_specs.cs

@@ -0,0 +1,16 @@
+#nullable enable
+
+using Buildalyzer;
+using FluentAssertions;
+
+namespace Project_GUID_specs;
+
+public class Creates
+{
+    [TestCase(null, /*....*/ "1b4db7eb-4057-5ddf-91e0-36dec72071f5")]
+    [TestCase("", /*......*/ "1b4db7eb-4057-5ddf-91e0-36dec72071f5")]
+    [TestCase("ABCDEFGHIJK", "2a738916-9f0a-5c81-a8fa-cc64ba606458")]
+    [TestCase("Buildalyzer", "74397281-1b33-5316-aad1-c7ef52552d75")]
+    public void SHA1_based_GUID(string? name, Guid projectId)
+        => ProjectGuid.Create(name).Should().Be(projectId);
+}