First round of cleanup for DolphinLib additions

SabreTools.Data.Extensions/NintendoDiscExtensions.cs

@@ -0,0 +1,30 @@
+using SabreTools.Data.Models.NintendoDisc;
+
+namespace SabreTools.Data.Extensions
+{
+    // TODO: Write tests for these
+    public static class NintendoDiscExtensions
+    {
+        /// <summary>
+        /// Get the platform associated with a disc header
+        /// </summary>
+        public static Platform GetPlatform(this DiscHeader header)
+        {
+            if (header.WiiMagic == Constants.WiiMagicWord)
+                return Platform.Wii;
+            else if (header.GCMagic == Constants.GCMagicWord)
+                return Platform.GameCube;
+            else if (header.GameId is not null && header.GameId.Length >= 1 && IsGameCubeTitleType(header.GameId[0]))
+                return Platform.GameCube;
+            else
+                return Platform.Unknown;
+        }
+
+        /// <summary>
+        /// Returns true if the GameId first character is a known GameCube title type prefix.
+        /// Used as a fallback when the GC magic word is absent from the disc image.
+        /// </summary>
+        public static bool IsGameCubeTitleType(this char c)
+            => c == 'G' || c == 'D' || c == 'R';
+    }
+}