Slight refactor to clean up resource loading from plugins

PkmnLib.Dynamic/ScriptHandling/Registry/ResourceProvider.cs

@@ -1,3 +1,4 @@
+using System.Reflection;
 using PkmnLib.Static.Libraries;
 
 namespace PkmnLib.Dynamic.ScriptHandling.Registry;
@@ -13,9 +14,10 @@ public interface IResourceProvider
     LibrarySettings? Settings { get; }
 
     /// <summary>
-    /// Gets the resource for the given type. This is used to load resources from the plugin.
+    /// Gets the resource for the given type. This is used to load resources from the plugin. Returns null if the
+    /// plugin does not provide the resource.
     /// </summary>
-    Stream? GetResource(ResourceFileType request);
+    IResourceResult? GetResource(ResourceFileType request);
 }
 
 /// <summary>
@@ -62,4 +64,36 @@ public enum ResourceFileType
     /// The type for the species of Pokémon. This includes the species names and the species effects.
     /// </summary>
     Species,
+}
+
+/// <summary>
+/// Interface for a resource result. This is used to load resources from the plugin.
+/// </summary>
+public interface IResourceResult
+{
+    /// <summary>
+    /// Opens the resource and returns a stream. This is used to load the resource from the plugin.
+    /// </summary>
+    Stream Open();
+}
+
+/// <summary>
+/// Class for a resource result that is loaded from an embedded resource in an assembly.
+/// </summary>
+public class AssemblyResourceResult : IResourceResult
+{
+    private readonly string _resourceName;
+    private readonly Assembly _assembly;
+
+    /// <inheritdoc cref="AssemblyResourceResult" />
+    public AssemblyResourceResult(string resourceName, Assembly assembly)
+    {
+        _resourceName = resourceName;
+        _assembly = assembly;
+    }
+
+    /// <inheritdoc />
+    public Stream Open() => _assembly.GetManifestResourceStream(_resourceName) ??
+                            throw new InvalidOperationException(
+                                $"Resource '{_resourceName}' not found in assembly '{_assembly.FullName}'.");
 }