Scaffolded resource manager

SlaveEngine.Assets/AssetProcessorAttribute.cs

@@ -0,0 +1,46 @@
+namespace SlaveEngine.Assets;
+
+public class AssetProcessorAttribute : Attribute {
+    public Type ManagedType { get; init; }
+    public string[] ManagedExtensions { get; init; }
+    
+    public AssetProcessorAttribute(Type managedType, string[] managedExtensions)
+    {
+        ManagedType = managedType ?? throw new ArgumentNullException(nameof(managedType));
+
+        // Validate that the provided type is Asset or a subclass of Asset
+        if (!typeof(Asset).IsSubclassOf(managedType))
+            throw new ArgumentException($"The type '{managedType.FullName}' must derive from '{typeof(Asset).FullName}'.", nameof(managedType));
+
+        // Validate extensions: non-null, non-empty, normalized, start with '.', no whitespace, unique
+        if (managedExtensions == null)
+            throw new ArgumentNullException(nameof(managedExtensions));
+
+        if (managedExtensions.Length == 0)
+            throw new ArgumentException("At least one file extension must be provided.", nameof(managedExtensions));
+
+        var normalized = new List<string>(managedExtensions.Length);
+        foreach (var ext in managedExtensions)
+        {
+            if (string.IsNullOrWhiteSpace(ext))
+                throw new ArgumentException("Extensions must be non-empty strings.", nameof(managedExtensions));
+
+            var e = ext.Trim();
+
+            // allow either "png" or ".png" as input, normalize to lowercase with leading dot
+            if (!e.StartsWith('.'))
+                e = "." + e;
+
+            if (e.Length < 2)
+                throw new ArgumentException($"Invalid extension '{ext}'.", nameof(managedExtensions));
+
+            if (e.Any(char.IsWhiteSpace))
+                throw new ArgumentException($"Extension '{ext}' contains whitespace.", nameof(managedExtensions));
+
+            normalized.Add(e.ToLowerInvariant());
+        }
+
+        // ensure uniqueness
+        ManagedExtensions = normalized.Distinct().ToArray();
+    }
+}