From 8c8c8d4e9ea01410aebf14f14ca10da5f585660c Mon Sep 17 00:00:00 2001
From: Victor Giers <mail@victorgiers.com>
Date: Fri, 1 May 2026 17:41:42 +0200
Subject: [PATCH] auto-git:  [add]
 src/commands/apply-terrain-brush-patch-command.ts

---
 .../apply-terrain-brush-patch-command.ts      | 120 ++++++++++++++++++
 1 file changed, 120 insertions(+)
 create mode 100644 src/commands/apply-terrain-brush-patch-command.ts

diff --git a/src/commands/apply-terrain-brush-patch-command.ts b/src/commands/apply-terrain-brush-patch-command.ts
new file mode 100644
index 00000000..7b085648
--- /dev/null
+++ b/src/commands/apply-terrain-brush-patch-command.ts
@@ -0,0 +1,120 @@
+import { createOpaqueId } from "../core/ids";
+import { cloneEditorSelection, type EditorSelection } from "../core/selection";
+import type {
+  TerrainBrushPatch,
+  TerrainSampleValuePatch
+} from "../core/terrain-brush";
+import type { ToolMode } from "../core/tool-mode";
+
+import type { EditorCommand } from "./command";
+
+interface ApplyTerrainBrushPatchCommandOptions {
+  patch: TerrainBrushPatch;
+  label?: string;
+}
+
+function setSingleTerrainSelection(terrainId: string): EditorSelection {
+  return {
+    kind: "terrains",
+    ids: [terrainId]
+  };
+}
+
+function assertValidPatchEntry(
+  entry: TerrainSampleValuePatch,
+  length: number,
+  label: string
+) {
+  if (
+    !Number.isInteger(entry.index) ||
+    entry.index < 0 ||
+    entry.index >= length
+  ) {
+    throw new Error(`${label} patch index ${entry.index} is out of range.`);
+  }
+
+  if (!Number.isFinite(entry.before) || !Number.isFinite(entry.after)) {
+    throw new Error(`${label} patch values must remain finite.`);
+  }
+}
+
+export function isTerrainBrushPatchEmpty(patch: TerrainBrushPatch): boolean {
+  return patch.heightSamples.length === 0 && patch.paintWeights.length === 0;
+}
+
+export function createApplyTerrainBrushPatchCommand(
+  options: ApplyTerrainBrushPatchCommandOptions
+): EditorCommand {
+  const patch: TerrainBrushPatch = {
+    terrainId: options.patch.terrainId,
+    heightSamples: options.patch.heightSamples.map((entry) => ({ ...entry })),
+    paintWeights: options.patch.paintWeights.map((entry) => ({ ...entry }))
+  };
+  let previousSelection: EditorSelection | null = null;
+  let previousToolMode: ToolMode | null = null;
+
+  const applyPatch = (
+    context: Parameters<EditorCommand["execute"]>[0],
+    direction: "forward" | "backward"
+  ) => {
+    const currentDocument = context.getDocument();
+    const terrain = currentDocument.terrains[patch.terrainId];
+
+    if (terrain === undefined) {
+      throw new Error(`Terrain ${patch.terrainId} does not exist.`);
+    }
+
+    for (const entry of patch.heightSamples) {
+      assertValidPatchEntry(entry, terrain.heights.length, "Terrain height");
+      terrain.heights[entry.index] =
+        direction === "forward" ? entry.after : entry.before;
+    }
+
+    for (const entry of patch.paintWeights) {
+      assertValidPatchEntry(
+        entry,
+        terrain.paintWeights.length,
+        "Terrain paint weight"
+      );
+      terrain.paintWeights[entry.index] =
+        direction === "forward" ? entry.after : entry.before;
+    }
+
+    context.setDocument({
+      ...currentDocument,
+      terrains: {
+        ...currentDocument.terrains,
+        [patch.terrainId]: terrain
+      }
+    });
+  };
+
+  return {
+    id: createOpaqueId("command"),
+    label: options.label ?? "Apply terrain brush patch",
+    execute(context) {
+      if (previousSelection === null) {
+        previousSelection = cloneEditorSelection(context.getSelection());
+      }
+
+      if (previousToolMode === null) {
+        previousToolMode = context.getToolMode();
+      }
+
+      applyPatch(context, "forward");
+      context.setSelection(setSingleTerrainSelection(patch.terrainId));
+      context.setToolMode("select");
+    },
+    undo(context) {
+      applyPatch(context, "backward");
+
+      if (previousSelection !== null) {
+        context.setSelection(previousSelection);
+      }
+
+      if (previousToolMode !== null) {
+        context.setToolMode(previousToolMode);
+      }
+    }
+  };
+}