From 2528d14d7a4076d7503e5892a1c9540c595e9a98 Mon Sep 17 00:00:00 2001
From: Victor Giers <mail@victorgiers.com>
Date: Wed, 13 May 2026 00:47:34 +0200
Subject: [PATCH] auto-git:  [add] src/commands/add-terrain-layer-command.ts

---
 src/commands/add-terrain-layer-command.ts | 102 ++++++++++++++++++++++
 1 file changed, 102 insertions(+)
 create mode 100644 src/commands/add-terrain-layer-command.ts

diff --git a/src/commands/add-terrain-layer-command.ts b/src/commands/add-terrain-layer-command.ts
new file mode 100644
index 00000000..8ef45032
--- /dev/null
+++ b/src/commands/add-terrain-layer-command.ts
@@ -0,0 +1,102 @@
+import { createOpaqueId } from "../core/ids";
+import { cloneEditorSelection, type EditorSelection } from "../core/selection";
+import type { ToolMode } from "../core/tool-mode";
+import {
+  cloneTerrain,
+  createTerrainWithAddedLayer,
+  getTerrainLayerLabel,
+  type Terrain
+} from "../document/terrains";
+
+import type { EditorCommand } from "./command";
+
+interface AddTerrainLayerCommandOptions {
+  terrainId: string;
+  materialId?: string | null;
+  label?: string;
+}
+
+function setSingleTerrainSelection(terrainId: string): EditorSelection {
+  return {
+    kind: "terrains",
+    ids: [terrainId]
+  };
+}
+
+export function createAddTerrainLayerCommand(
+  options: AddTerrainLayerCommandOptions
+): EditorCommand {
+  let previousTerrain: Terrain | null = null;
+  let nextTerrain: Terrain | null = null;
+  let previousSelection: EditorSelection | null = null;
+  let previousToolMode: ToolMode | null = null;
+
+  return {
+    id: createOpaqueId("command"),
+    label: options.label ?? "Add terrain material layer",
+    execute(context) {
+      const currentDocument = context.getDocument();
+      const terrain = currentDocument.terrains[options.terrainId];
+
+      if (terrain === undefined) {
+        throw new Error(`Terrain ${options.terrainId} does not exist.`);
+      }
+
+      if (previousTerrain === null) {
+        previousTerrain = cloneTerrain(terrain);
+      }
+
+      if (previousSelection === null) {
+        previousSelection = cloneEditorSelection(context.getSelection());
+      }
+
+      if (previousToolMode === null) {
+        previousToolMode = context.getToolMode();
+      }
+
+      if (nextTerrain === null) {
+        nextTerrain = createTerrainWithAddedLayer(
+          terrain,
+          options.materialId ?? null
+        );
+      }
+
+      context.setDocument({
+        ...currentDocument,
+        terrains: {
+          ...currentDocument.terrains,
+          [options.terrainId]: cloneTerrain(nextTerrain)
+        }
+      });
+      context.setSelection(setSingleTerrainSelection(options.terrainId));
+      context.setToolMode("select");
+    },
+    undo(context) {
+      if (previousTerrain === null) {
+        return;
+      }
+
+      const currentDocument = context.getDocument();
+
+      context.setDocument({
+        ...currentDocument,
+        terrains: {
+          ...currentDocument.terrains,
+          [options.terrainId]: cloneTerrain(previousTerrain)
+        }
+      });
+
+      if (previousSelection !== null) {
+        context.setSelection(previousSelection);
+      }
+
+      if (previousToolMode !== null) {
+        context.setToolMode(previousToolMode);
+      }
+    }
+  };
+}
+
+export function getAddedTerrainLayerStatusLabel(terrain: Terrain): string {
+  return getTerrainLayerLabel(terrain.layers.length - 1);
+}