Add subgraph skeleton classes (#997)

Allows downstream consumers to use subgraph types ahead of impl.

src/subgraph/SubgraphIONodeBase.ts

@@ -0,0 +1,82 @@
+import type { Subgraph } from "./Subgraph"
+import type { SubgraphInput } from "./SubgraphInput"
+import type { SubgraphOutput } from "./SubgraphOutput"
+import type { Point, Positionable, ReadOnlyRect, Rect } from "@/interfaces"
+import type { NodeId } from "@/LGraphNode"
+import type { ExportedSubgraphIONode, Serialisable } from "@/types/serialisation"
+
+import { isPointInRect, snapPoint } from "@/measure"
+
+export abstract class SubgraphIONodeBase implements Positionable, Serialisable<ExportedSubgraphIONode> {
+  static margin = 10
+  static defaultWidth = 100
+  static roundedRadius = 10
+
+  readonly #boundingRect: Float32Array = new Float32Array(4)
+  readonly #pos: Point = this.#boundingRect.subarray(0, 2)
+  readonly #size: Point = this.#boundingRect.subarray(2, 4)
+
+  abstract readonly id: NodeId
+
+  get boundingRect(): Rect {
+    return this.#boundingRect
+  }
+
+  selected: boolean = false
+  pinned: boolean = false
+
+  get pos() {
+    return this.#pos
+  }
+
+  set pos(value) {
+    if (!value || value.length < 2) return
+
+    this.#pos[0] = value[0]
+    this.#pos[1] = value[1]
+  }
+
+  get size() {
+    return this.#size
+  }
+
+  set size(value) {
+    if (!value || value.length < 2) return
+
+    this.#size[0] = value[0]
+    this.#size[1] = value[1]
+  }
+
+  abstract readonly slots: SubgraphInput[] | SubgraphOutput[]
+
+  constructor(
+    /** The subgraph that this node belongs to. */
+    readonly subgraph: Subgraph,
+  ) {}
+
+  move(deltaX: number, deltaY: number): void {
+    this.pos[0] += deltaX
+    this.pos[1] += deltaY
+  }
+
+  /** @inheritdoc */
+  snapToGrid(snapTo: number): boolean {
+    return this.pinned ? false : snapPoint(this.pos, snapTo)
+  }
+
+  containsPoint(point: Point): boolean {
+    return isPointInRect(point, this.boundingRect)
+  }
+
+  asSerialisable(): ExportedSubgraphIONode {
+    return {
+      id: this.id,
+      bounding: serialiseRect(this.boundingRect),
+      pinned: this.pinned ? true : undefined,
+    }
+  }
+}
+
+function serialiseRect(rect: ReadOnlyRect): [number, number, number, number] {
+  return [rect[0], rect[1], rect[2], rect[3]]
+}