From 9e29123d2e7aaa84f665599c07feb9fe6f512734 Mon Sep 17 00:00:00 2001
From: Daniel Cazzulino <daniel@cazzulino.com>
Date: Sat, 7 Dec 2024 12:07:00 -0300
Subject: [PATCH] Add IUtf8SpanFormattable template

---
 src/StructId.FunctionalTests/Functional.cs    | 21 +++++++++++++++++++
 src/StructId/Templates/Utf8SpanFormattable.cs | 12 +++++++++++
 2 files changed, 33 insertions(+)
 create mode 100644 src/StructId/Templates/Utf8SpanFormattable.cs

diff --git a/src/StructId.FunctionalTests/Functional.cs b/src/StructId.FunctionalTests/Functional.cs
index bbfbc25..8b4a84a 100644
--- a/src/StructId.FunctionalTests/Functional.cs
+++ b/src/StructId.FunctionalTests/Functional.cs
@@ -1,4 +1,5 @@
 using System.Diagnostics.CodeAnalysis;
+using System.Text;
 using Dapper;
 using Microsoft.Data.Sqlite;
 using Microsoft.EntityFrameworkCore;
@@ -140,6 +141,26 @@ public void StringIdDoesNotImplementISpanFormattable()
         Assert.IsNotAssignableFrom<ISpanFormattable>(WalletId.New("foo"));
     }
 
+    [Fact]
+    public void GuidImplementUtf8SpanFormattable()
+    {
+        var id = ProductId.New();
+
+        Assert.IsAssignableFrom<IUtf8SpanFormattable>(id);
+
+        Span<byte> utf8Destination = new byte[36]; // Typical GUID length in string form
+
+        if (id.TryFormat(utf8Destination, out int bytesWritten, default, null))
+        {
+            var guid = new Guid(Encoding.UTF8.GetString(utf8Destination.Slice(0, bytesWritten)));
+            Assert.Equal(id.Value, guid);
+        }
+        else
+        {
+            Assert.Fail("TryFormat failed");
+        }
+    }
+
     public class Context : DbContext
     {
         public Context(DbContextOptions<Context> options) : base(options) { }
diff --git a/src/StructId/Templates/Utf8SpanFormattable.cs b/src/StructId/Templates/Utf8SpanFormattable.cs
new file mode 100644
index 0000000..51fe415
--- /dev/null
+++ b/src/StructId/Templates/Utf8SpanFormattable.cs
@@ -0,0 +1,12 @@
+// <auto-generated />
+#nullable enable
+
+using System;
+using StructId;
+
+[TStructId]
+file partial record struct Utf8SpanFormattable(IUtf8SpanFormattable Value) : IUtf8SpanFormattable
+{
+    public bool TryFormat(Span<byte> utf8Destination, out int bytesWritten, ReadOnlySpan<char> format, IFormatProvider? provider) 
+        => Value.TryFormat(utf8Destination, out bytesWritten, format, provider);
+}
\ No newline at end of file