Move UUID v7 polyfill to Common/Polyfills/System/GuidPolyfills.cs

Co-authored-by: eiriktsarpalis <2813363+eiriktsarpalis@users.noreply.github.com>

Author: Copilot

src/Common/Polyfills/System/GuidPolyfills.cs

@@ -0,0 +1,62 @@
+#if !NET9_0_OR_GREATER
+namespace System;
+
+/// <summary>
+/// Polyfill for Guid methods not available in older .NET versions.
+/// </summary>
+internal static class GuidPolyfills
+{
+    /// <summary>
+    /// Creates a new Guid according to RFC 9562, following the Version 7 format.
+    /// This polyfill provides the functionality of <c>Guid.CreateVersion7()</c> for targets earlier than .NET 9.
+    /// </summary>
+    /// <returns>A new Guid with embedded timestamp for monotonic ordering.</returns>
+    public static Guid CreateVersion7()
+    {
+        // UUID v7 format (RFC 9562):
+        // - 48 bits: Unix timestamp in milliseconds (big-endian)
+        // - 4 bits: version (0111 = 7)
+        // - 12 bits: random
+        // - 2 bits: variant (10)
+        // - 62 bits: random
+
+        var timestamp = DateTimeOffset.UtcNow.ToUnixTimeMilliseconds();
+        byte[] bytes = new byte[16];
+
+        // Fill with random data first
+#if NETSTANDARD2_0
+        using (var rng = Security.Cryptography.RandomNumberGenerator.Create())
+        {
+            rng.GetBytes(bytes);
+        }
+#else
+        Security.Cryptography.RandomNumberGenerator.Fill(bytes);
+#endif
+
+        // Set timestamp (48 bits, big-endian) in first 6 bytes
+        bytes[0] = (byte)(timestamp >> 40);
+        bytes[1] = (byte)(timestamp >> 32);
+        bytes[2] = (byte)(timestamp >> 24);
+        bytes[3] = (byte)(timestamp >> 16);
+        bytes[4] = (byte)(timestamp >> 8);
+        bytes[5] = (byte)timestamp;
+
+        // Set version 7 (0111) in high nibble of byte 6
+        bytes[6] = (byte)((bytes[6] & 0x0F) | 0x70);
+
+        // Set variant (10) in high 2 bits of byte 8
+        bytes[8] = (byte)((bytes[8] & 0x3F) | 0x80);
+
+        // Convert from big-endian byte array to Guid
+        // Guid constructor expects bytes in a specific order for the first 8 bytes
+        // (little-endian for the first three components on Windows)
+        // We need to swap bytes to match the Guid's internal layout
+        return new Guid(
+            (int)(bytes[0] << 24 | bytes[1] << 16 | bytes[2] << 8 | bytes[3]),  // a (big-endian to int)
+            (short)(bytes[4] << 8 | bytes[5]),  // b (big-endian to short)
+            (short)(bytes[6] << 8 | bytes[7]),  // c (big-endian to short)
+            bytes[8], bytes[9], bytes[10], bytes[11],
+            bytes[12], bytes[13], bytes[14], bytes[15]);
+    }
+}
+#endif

src/ModelContextProtocol.Core/Server/InMemoryMcpTaskStore.cs

@@ -451,59 +451,7 @@ public void Dispose()
 #if NET9_0_OR_GREATER
     private static string GenerateTaskId() => Guid.CreateVersion7().ToString("N");
 #else
-    private static string GenerateTaskId() => CreateVersion7Guid().ToString("N");
-
-    /// <summary>
-    /// Polyfill for Guid.CreateVersion7() on targets earlier than .NET 9.
-    /// Generates a UUID v7 with embedded timestamp for monotonic ordering.
-    /// </summary>
-    private static Guid CreateVersion7Guid()
-    {
-        // UUID v7 format (RFC 9562):
-        // - 48 bits: Unix timestamp in milliseconds (big-endian)
-        // - 4 bits: version (0111 = 7)
-        // - 12 bits: random
-        // - 2 bits: variant (10)
-        // - 62 bits: random
-
-        var timestamp = DateTimeOffset.UtcNow.ToUnixTimeMilliseconds();
-        byte[] bytes = new byte[16];
-
-        // Fill with random data first
-#if NETSTANDARD2_0
-        using (var rng = System.Security.Cryptography.RandomNumberGenerator.Create())
-        {
-            rng.GetBytes(bytes);
-        }
-#else
-        System.Security.Cryptography.RandomNumberGenerator.Fill(bytes);
-#endif
-
-        // Set timestamp (48 bits, big-endian) in first 6 bytes
-        bytes[0] = (byte)(timestamp >> 40);
-        bytes[1] = (byte)(timestamp >> 32);
-        bytes[2] = (byte)(timestamp >> 24);
-        bytes[3] = (byte)(timestamp >> 16);
-        bytes[4] = (byte)(timestamp >> 8);
-        bytes[5] = (byte)timestamp;
-
-        // Set version 7 (0111) in high nibble of byte 6
-        bytes[6] = (byte)((bytes[6] & 0x0F) | 0x70);
-
-        // Set variant (10) in high 2 bits of byte 8
-        bytes[8] = (byte)((bytes[8] & 0x3F) | 0x80);
-
-        // Convert from big-endian byte array to Guid
-        // Guid constructor expects bytes in a specific order for the first 8 bytes
-        // (little-endian for the first three components on Windows)
-        // We need to swap bytes to match the Guid's internal layout
-        return new Guid(
-            (int)(bytes[0] << 24 | bytes[1] << 16 | bytes[2] << 8 | bytes[3]),  // a (big-endian to int)
-            (short)(bytes[4] << 8 | bytes[5]),  // b (big-endian to short)
-            (short)(bytes[6] << 8 | bytes[7]),  // c (big-endian to short)
-            bytes[8], bytes[9], bytes[10], bytes[11],
-            bytes[12], bytes[13], bytes[14], bytes[15]);
-    }
+    private static string GenerateTaskId() => GuidPolyfills.CreateVersion7().ToString("N");
 #endif
 
     private static bool IsTerminalStatus(McpTaskStatus status) =>