Add set scene loading screen command

src/commands/set-scene-loading-screen-command.ts

@@ -0,0 +1,79 @@
+import { createOpaqueId } from "../core/ids";
+import {
+  cloneSceneLoadingScreenSettings,
+  type SceneLoadingScreenSettings
+} from "../document/scene-document";
+
+import type { EditorCommand } from "./command";
+
+interface SetSceneLoadingScreenCommandOptions {
+  sceneId: string;
+  label: string;
+  loadingScreen: SceneLoadingScreenSettings;
+}
+
+export function createSetSceneLoadingScreenCommand(
+  options: SetSceneLoadingScreenCommandOptions
+): EditorCommand {
+  const nextLoadingScreen = cloneSceneLoadingScreenSettings(
+    options.loadingScreen
+  );
+  let previousLoadingScreen: SceneLoadingScreenSettings | null = null;
+
+  return {
+    id: createOpaqueId("command"),
+    label: options.label,
+    execute(context) {
+      const currentProjectDocument = context.getProjectDocument();
+      const currentScene = currentProjectDocument.scenes[options.sceneId];
+
+      if (currentScene === undefined) {
+        throw new Error(
+          `Cannot update loading overlay for missing scene ${options.sceneId}.`
+        );
+      }
+
+      if (previousLoadingScreen === null) {
+        previousLoadingScreen = cloneSceneLoadingScreenSettings(
+          currentScene.loadingScreen
+        );
+      }
+
+      context.setProjectDocument({
+        ...currentProjectDocument,
+        scenes: {
+          ...currentProjectDocument.scenes,
+          [options.sceneId]: {
+            ...currentScene,
+            loadingScreen: cloneSceneLoadingScreenSettings(nextLoadingScreen)
+          }
+        }
+      });
+    },
+    undo(context) {
+      if (previousLoadingScreen === null) {
+        return;
+      }
+
+      const currentProjectDocument = context.getProjectDocument();
+      const currentScene = currentProjectDocument.scenes[options.sceneId];
+
+      if (currentScene === undefined) {
+        throw new Error(
+          `Cannot restore loading overlay for missing scene ${options.sceneId}.`
+        );
+      }
+
+      context.setProjectDocument({
+        ...currentProjectDocument,
+        scenes: {
+          ...currentProjectDocument.scenes,
+          [options.sceneId]: {
+            ...currentScene,
+            loadingScreen: cloneSceneLoadingScreenSettings(previousLoadingScreen)
+          }
+        }
+      });
+    }
+  };
+}