From 53c19deffbfe7896db7d539d12f65869b7aaf9ca Mon Sep 17 00:00:00 2001
From: Victor Giers <mail@victorgiers.com>
Date: Sun, 5 Apr 2026 04:21:56 +0200
Subject: [PATCH] Add duplicate selection command

---
 src/commands/duplicate-selection-command.ts | 265 ++++++++++++++++++++
 1 file changed, 265 insertions(+)
 create mode 100644 src/commands/duplicate-selection-command.ts

diff --git a/src/commands/duplicate-selection-command.ts b/src/commands/duplicate-selection-command.ts
new file mode 100644
index 00000000..7c3084db
--- /dev/null
+++ b/src/commands/duplicate-selection-command.ts
@@ -0,0 +1,265 @@
+import { cloneModelInstance, type ModelInstance } from "../assets/model-instances";
+import { createOpaqueId } from "../core/ids";
+import { cloneEditorSelection, type EditorSelection } from "../core/selection";
+import type { ToolMode } from "../core/tool-mode";
+import type { Vec3 } from "../core/vector";
+import { cloneBoxBrush, type BoxBrush } from "../document/brushes";
+import { cloneEntityInstance, type EntityInstance } from "../entities/entity-instances";
+
+import type { EditorCommand } from "./command";
+
+export const DUPLICATE_SELECTION_OFFSET: Vec3 = {
+  x: 1,
+  y: 0,
+  z: 1
+};
+
+interface DuplicateSelectionResult {
+  selection: EditorSelection;
+  brushes: BoxBrush[] | null;
+  entities: EntityInstance[] | null;
+  modelInstances: ModelInstance[] | null;
+}
+
+function applyDuplicateSelectionOffset(position: Vec3): Vec3 {
+  return {
+    x: position.x + DUPLICATE_SELECTION_OFFSET.x,
+    y: position.y + DUPLICATE_SELECTION_OFFSET.y,
+    z: position.z + DUPLICATE_SELECTION_OFFSET.z
+  };
+}
+
+function duplicateBrush(brush: BoxBrush): BoxBrush {
+  const duplicatedBrush = cloneBoxBrush(brush);
+  duplicatedBrush.id = createOpaqueId("brush");
+  duplicatedBrush.center = applyDuplicateSelectionOffset(duplicatedBrush.center);
+  return duplicatedBrush;
+}
+
+function duplicateEntity(entity: EntityInstance): EntityInstance {
+  const duplicatedEntity = cloneEntityInstance(entity);
+  duplicatedEntity.id = createOpaqueId(`entity-${duplicatedEntity.kind}`);
+  duplicatedEntity.position = applyDuplicateSelectionOffset(duplicatedEntity.position);
+  return duplicatedEntity;
+}
+
+function duplicateModelInstance(modelInstance: ModelInstance): ModelInstance {
+  const duplicatedModelInstance = cloneModelInstance(modelInstance);
+  duplicatedModelInstance.id = createOpaqueId("model-instance");
+  duplicatedModelInstance.position = applyDuplicateSelectionOffset(duplicatedModelInstance.position);
+  return duplicatedModelInstance;
+}
+
+function resolveDuplicatableBrushIds(selection: EditorSelection): string[] | null {
+  switch (selection.kind) {
+    case "brushes":
+      return selection.ids;
+    case "brushFace":
+    case "brushEdge":
+    case "brushVertex":
+      return [selection.brushId];
+    default:
+      return null;
+  }
+}
+
+function createDuplicateSelectionResult(currentDocument: ReturnType<Parameters<EditorCommand["execute"]>[0]["getDocument"]>, selection: EditorSelection): DuplicateSelectionResult {
+  const duplicatableBrushIds = resolveDuplicatableBrushIds(selection);
+
+  if (duplicatableBrushIds !== null) {
+    if (duplicatableBrushIds.length === 0) {
+      throw new Error("Select at least one whitebox solid to duplicate.");
+    }
+
+    const duplicatedBrushes = duplicatableBrushIds.map((brushId) => {
+      const sourceBrush = currentDocument.brushes[brushId];
+
+      if (sourceBrush === undefined) {
+        throw new Error(`Box brush ${brushId} does not exist.`);
+      }
+
+      if (sourceBrush.kind !== "box") {
+        throw new Error(`Brush ${brushId} is not a supported box brush.`);
+      }
+
+      return duplicateBrush(sourceBrush);
+    });
+
+    return {
+      selection: {
+        kind: "brushes",
+        ids: duplicatedBrushes.map((brush) => brush.id)
+      },
+      brushes: duplicatedBrushes,
+      entities: null,
+      modelInstances: null
+    };
+  }
+
+  if (selection.kind === "entities") {
+    if (selection.ids.length === 0) {
+      throw new Error("Select at least one entity to duplicate.");
+    }
+
+    const duplicatedEntities = selection.ids.map((entityId) => {
+      const sourceEntity = currentDocument.entities[entityId];
+
+      if (sourceEntity === undefined) {
+        throw new Error(`Entity ${entityId} does not exist.`);
+      }
+
+      return duplicateEntity(sourceEntity);
+    });
+
+    return {
+      selection: {
+        kind: "entities",
+        ids: duplicatedEntities.map((entity) => entity.id)
+      },
+      brushes: null,
+      entities: duplicatedEntities,
+      modelInstances: null
+    };
+  }
+
+  if (selection.kind === "modelInstances") {
+    if (selection.ids.length === 0) {
+      throw new Error("Select at least one model instance to duplicate.");
+    }
+
+    const duplicatedModelInstances = selection.ids.map((modelInstanceId) => {
+      const sourceModelInstance = currentDocument.modelInstances[modelInstanceId];
+
+      if (sourceModelInstance === undefined) {
+        throw new Error(`Model instance ${modelInstanceId} does not exist.`);
+      }
+
+      return duplicateModelInstance(sourceModelInstance);
+    });
+
+    return {
+      selection: {
+        kind: "modelInstances",
+        ids: duplicatedModelInstances.map((modelInstance) => modelInstance.id)
+      },
+      brushes: null,
+      entities: null,
+      modelInstances: duplicatedModelInstances
+    };
+  }
+
+  throw new Error("Selection must contain whitebox solids, entities, or model instances to duplicate.");
+}
+
+export function createDuplicateSelectionCommand(): EditorCommand {
+  let previousSelection: EditorSelection | null = null;
+  let previousToolMode: ToolMode | null = null;
+  let duplicateSelectionResult: DuplicateSelectionResult | null = null;
+
+  return {
+    id: createOpaqueId("command"),
+    label: "Duplicate selection",
+    execute(context) {
+      const currentDocument = context.getDocument();
+
+      if (previousSelection === null) {
+        previousSelection = cloneEditorSelection(context.getSelection());
+      }
+
+      if (previousToolMode === null) {
+        previousToolMode = context.getToolMode();
+      }
+
+      if (duplicateSelectionResult === null) {
+        duplicateSelectionResult = createDuplicateSelectionResult(currentDocument, context.getSelection());
+      }
+
+      if (duplicateSelectionResult.brushes !== null) {
+        context.setDocument({
+          ...currentDocument,
+          brushes: {
+            ...currentDocument.brushes,
+            ...Object.fromEntries(duplicateSelectionResult.brushes.map((brush) => [brush.id, cloneBoxBrush(brush)]))
+          }
+        });
+      } else if (duplicateSelectionResult.entities !== null) {
+        context.setDocument({
+          ...currentDocument,
+          entities: {
+            ...currentDocument.entities,
+            ...Object.fromEntries(duplicateSelectionResult.entities.map((entity) => [entity.id, cloneEntityInstance(entity)]))
+          }
+        });
+      } else if (duplicateSelectionResult.modelInstances !== null) {
+        context.setDocument({
+          ...currentDocument,
+          modelInstances: {
+            ...currentDocument.modelInstances,
+            ...Object.fromEntries(
+              duplicateSelectionResult.modelInstances.map((modelInstance) => [modelInstance.id, cloneModelInstance(modelInstance)])
+            )
+          }
+        });
+      }
+
+      context.setSelection(cloneEditorSelection(duplicateSelectionResult.selection));
+      context.setToolMode("select");
+    },
+    undo(context) {
+      if (duplicateSelectionResult === null) {
+        return;
+      }
+
+      const currentDocument = context.getDocument();
+
+      if (duplicateSelectionResult.brushes !== null) {
+        const nextBrushes = {
+          ...currentDocument.brushes
+        };
+
+        for (const duplicatedBrush of duplicateSelectionResult.brushes) {
+          delete nextBrushes[duplicatedBrush.id];
+        }
+
+        context.setDocument({
+          ...currentDocument,
+          brushes: nextBrushes
+        });
+      } else if (duplicateSelectionResult.entities !== null) {
+        const nextEntities = {
+          ...currentDocument.entities
+        };
+
+        for (const duplicatedEntity of duplicateSelectionResult.entities) {
+          delete nextEntities[duplicatedEntity.id];
+        }
+
+        context.setDocument({
+          ...currentDocument,
+          entities: nextEntities
+        });
+      } else if (duplicateSelectionResult.modelInstances !== null) {
+        const nextModelInstances = {
+          ...currentDocument.modelInstances
+        };
+
+        for (const duplicatedModelInstance of duplicateSelectionResult.modelInstances) {
+          delete nextModelInstances[duplicatedModelInstance.id];
+        }
+
+        context.setDocument({
+          ...currentDocument,
+          modelInstances: nextModelInstances
+        });
+      }
+
+      if (previousSelection !== null) {
+        context.setSelection(previousSelection);
+      }
+
+      if (previousToolMode !== null) {
+        context.setToolMode(previousToolMode);
+      }
+    }
+  };
+}
\ No newline at end of file