Add scene creation and active scene switching commands

src/commands/create-scene-command.ts

@@ -0,0 +1,68 @@
+import { createOpaqueId } from "../core/ids";
+import { createEmptyProjectScene } from "../document/scene-document";
+
+import type { EditorCommand } from "./command";
+
+function createUniqueSceneName(existingNames: string[]): string {
+  const normalizedNames = new Set(
+    existingNames.map((name) => name.trim().toLowerCase())
+  );
+  let suffix = existingNames.length + 1;
+
+  while (normalizedNames.has(`scene ${suffix}`)) {
+    suffix += 1;
+  }
+
+  return `Scene ${suffix}`;
+}
+
+export function createCreateSceneCommand(): EditorCommand {
+  const createdSceneId = createOpaqueId("scene");
+  let createdSceneName: string | null = null;
+  let previousProjectDocumentSerialized: string | null = null;
+
+  return {
+    id: createOpaqueId("command"),
+    label: "Create scene",
+    execute(context) {
+      const currentProjectDocument = context.getProjectDocument();
+
+      if (previousProjectDocumentSerialized === null) {
+        previousProjectDocumentSerialized = JSON.stringify(currentProjectDocument);
+      }
+
+      if (createdSceneName === null) {
+        createdSceneName = createUniqueSceneName(
+          Object.values(currentProjectDocument.scenes).map((scene) => scene.name)
+        );
+      }
+
+      context.setProjectDocument({
+        ...currentProjectDocument,
+        activeSceneId: createdSceneId,
+        scenes: {
+          ...currentProjectDocument.scenes,
+          [createdSceneId]: createEmptyProjectScene({
+            id: createdSceneId,
+            name: createdSceneName
+          })
+        }
+      });
+      context.setSelection({ kind: "none" });
+      context.setToolMode("select");
+    },
+    undo(context) {
+      if (previousProjectDocumentSerialized === null) {
+        return;
+      }
+
+      context.setProjectDocument(
+        JSON.parse(previousProjectDocumentSerialized) as ReturnType<
+          typeof context.getProjectDocument
+        >
+      );
+      context.setSelection({ kind: "none" });
+      context.setToolMode("select");
+    }
+  };
+}