Add brush and grid snapping functionality

src/document/brushes.ts

@@ -0,0 +1,117 @@
+import { createOpaqueId } from "../core/ids";
+import type { Vec3 } from "../core/vector";
+
+export const BOX_FACE_IDS = ["posX", "negX", "posY", "negY", "posZ", "negZ"] as const;
+
+export type BoxFaceId = (typeof BOX_FACE_IDS)[number];
+
+export interface BrushFace {
+  materialId: string | null;
+}
+
+export type BoxBrushFaces = Record<BoxFaceId, BrushFace>;
+
+export interface BoxBrush {
+  id: string;
+  kind: "box";
+  center: Vec3;
+  size: Vec3;
+  faces: BoxBrushFaces;
+  layerId?: string;
+  groupId?: string;
+}
+
+export type Brush = BoxBrush;
+
+export const DEFAULT_BOX_BRUSH_CENTER: Vec3 = {
+  x: 0,
+  y: 1,
+  z: 0
+};
+
+export const DEFAULT_BOX_BRUSH_SIZE: Vec3 = {
+  x: 2,
+  y: 2,
+  z: 2
+};
+
+function cloneVec3(vector: Vec3): Vec3 {
+  return {
+    x: vector.x,
+    y: vector.y,
+    z: vector.z
+  };
+}
+
+function cloneBrushFace(face: BrushFace): BrushFace {
+  return {
+    materialId: face.materialId
+  };
+}
+
+export function isBoxFaceId(value: unknown): value is BoxFaceId {
+  return typeof value === "string" && BOX_FACE_IDS.some((faceId) => faceId === value);
+}
+
+export function hasPositiveBoxSize(size: Vec3): boolean {
+  return size.x > 0 && size.y > 0 && size.z > 0;
+}
+
+export function cloneBoxBrushFaces(faces: BoxBrushFaces): BoxBrushFaces {
+  return {
+    posX: cloneBrushFace(faces.posX),
+    negX: cloneBrushFace(faces.negX),
+    posY: cloneBrushFace(faces.posY),
+    negY: cloneBrushFace(faces.negY),
+    posZ: cloneBrushFace(faces.posZ),
+    negZ: cloneBrushFace(faces.negZ)
+  };
+}
+
+export function createDefaultBoxBrushFaces(): BoxBrushFaces {
+  return {
+    posX: {
+      materialId: null
+    },
+    negX: {
+      materialId: null
+    },
+    posY: {
+      materialId: null
+    },
+    negY: {
+      materialId: null
+    },
+    posZ: {
+      materialId: null
+    },
+    negZ: {
+      materialId: null
+    }
+  };
+}
+
+export function createBoxBrush(
+  overrides: Partial<Pick<BoxBrush, "id" | "center" | "size" | "faces" | "layerId" | "groupId">> = {}
+): BoxBrush {
+  const center = cloneVec3(overrides.center ?? DEFAULT_BOX_BRUSH_CENTER);
+  const size = cloneVec3(overrides.size ?? DEFAULT_BOX_BRUSH_SIZE);
+
+  if (!hasPositiveBoxSize(size)) {
+    throw new Error("Box brush size must remain positive on every axis.");
+  }
+
+  return {
+    id: overrides.id ?? createOpaqueId("brush"),
+    kind: "box",
+    center,
+    size,
+    faces: overrides.faces === undefined ? createDefaultBoxBrushFaces() : cloneBoxBrushFaces(overrides.faces),
+    layerId: overrides.layerId,
+    groupId: overrides.groupId
+  };
+}
+
+export function cloneBoxBrush(brush: BoxBrush): BoxBrush {
+  return createBoxBrush(brush);
+}