renames shapes -> shape utils

lib/shape-utils/index.tsx

@@ -0,0 +1,123 @@
+import {
+  Bounds,
+  BoundsSnapshot,
+  Shape,
+  Shapes,
+  ShapeType,
+  TransformCorner,
+  TransformEdge,
+} from "types"
+import circle from "./circle"
+import dot from "./dot"
+import polyline from "./polyline"
+import rectangle from "./rectangle"
+import ellipse from "./ellipse"
+import line from "./line"
+import ray from "./ray"
+
+/*
+Shape Utiliies
+
+A shape utility is an object containing utility methods for each type of shape
+in the application. While shapes may be very different, each shape must support
+a common set of utility methods, such as hit tests or translations, that 
+
+Operations throughout the app will call these utility methods
+when performing tests (such as hit tests) or mutations, such as translations.
+*/
+
+export interface ShapeUtility<K extends Shape> {
+  // A cache for the computed bounds of this kind of shape.
+  boundsCache: WeakMap<K, Bounds>
+
+  // Create a new shape.
+  create(props: Partial<K>): K
+
+  // Get the bounds of the a shape.
+  getBounds(this: ShapeUtility<K>, shape: K): Bounds
+
+  // Get the routated bounds of the a shape.
+  getRotatedBounds(this: ShapeUtility<K>, shape: K): Bounds
+
+  // Get the center of the shape
+  getCenter(this: ShapeUtility<K>, shape: K): number[]
+
+  // Test whether a point lies within a shape.
+  hitTest(this: ShapeUtility<K>, shape: K, test: number[]): boolean
+
+  // Test whether bounds collide with or contain a shape.
+  hitTestBounds(this: ShapeUtility<K>, shape: K, bounds: Bounds): boolean
+
+  // Apply a rotation to a shape.
+  rotate(this: ShapeUtility<K>, shape: K): K
+
+  // Apply a translation to a shape.
+  translate(this: ShapeUtility<K>, shape: K, delta: number[]): K
+
+  // Transform to fit a new bounding box.
+  transform(
+    this: ShapeUtility<K>,
+    shape: K,
+    bounds: Bounds,
+    info: {
+      type: TransformEdge | TransformCorner
+      initialShape: K
+      scaleX: number
+      scaleY: number
+    }
+  ): K
+
+  transformSingle(
+    this: ShapeUtility<K>,
+    shape: K,
+    bounds: Bounds,
+    info: {
+      type: TransformEdge | TransformCorner
+      initialShape: K
+      scaleX: number
+      scaleY: number
+    }
+  ): K
+
+  // Apply a scale to a shape.
+  scale(this: ShapeUtility<K>, shape: K, scale: number): K
+
+  // Render a shape to JSX.
+  render(this: ShapeUtility<K>, shape: K): JSX.Element
+
+  // Whether to show transform controls when this shape is selected.
+  canTransform: boolean
+}
+
+// A mapping of shape types to shape utilities.
+const shapeUtilityMap: { [key in ShapeType]: ShapeUtility<Shapes[key]> } = {
+  [ShapeType.Circle]: circle,
+  [ShapeType.Dot]: dot,
+  [ShapeType.Polyline]: polyline,
+  [ShapeType.Rectangle]: rectangle,
+  [ShapeType.Ellipse]: ellipse,
+  [ShapeType.Line]: line,
+  [ShapeType.Ray]: ray,
+}
+
+/**
+ * A helper to retrieve a shape utility based on a shape object.
+ * @param shape
+ * @returns
+ */
+export function getShapeUtils(shape: Shape): ShapeUtility<typeof shape> {
+  return shapeUtilityMap[shape.type]
+}
+
+/**
+ *  A factory of shape utilities, with typing enforced.
+ * @param shape
+ * @returns
+ */
+export function registerShapeUtils<T extends Shape>(
+  shape: ShapeUtility<T>
+): ShapeUtility<T> {
+  return Object.freeze(shape)
+}
+
+export default shapeUtilityMap