Feat: Implement foliage layer management commands (create, delete, update)

src/commands/create-foliage-layer-command.ts

@@ -0,0 +1,48 @@
+import { createOpaqueId } from "../core/ids";
+import { cloneFoliageLayer, type FoliageLayer } from "../foliage/foliage";
+
+import type { EditorCommand } from "./command";
+
+interface CreateFoliageLayerCommandOptions {
+  layer: FoliageLayer;
+  label?: string;
+}
+
+export function createCreateFoliageLayerCommand(
+  options: CreateFoliageLayerCommandOptions
+): EditorCommand {
+  const nextLayer = cloneFoliageLayer(options.layer);
+
+  return {
+    id: createOpaqueId("command"),
+    label: options.label ?? "Create foliage layer",
+    execute(context) {
+      const currentDocument = context.getDocument();
+
+      if (currentDocument.foliageLayers[nextLayer.id] !== undefined) {
+        throw new Error(`Foliage layer ${nextLayer.id} already exists.`);
+      }
+
+      context.setDocument({
+        ...currentDocument,
+        foliageLayers: {
+          ...currentDocument.foliageLayers,
+          [nextLayer.id]: cloneFoliageLayer(nextLayer)
+        }
+      });
+    },
+    undo(context) {
+      const currentDocument = context.getDocument();
+      const nextFoliageLayers = {
+        ...currentDocument.foliageLayers
+      };
+
+      delete nextFoliageLayers[nextLayer.id];
+
+      context.setDocument({
+        ...currentDocument,
+        foliageLayers: nextFoliageLayers
+      });
+    }
+  };
+}