1 files changed, 46 insertions, 0 deletions
diff --git a/llparse-frontend/src/node/base.ts b/llparse-frontend/src/node/base.ts
new file mode 100644
index 0000000..1e93c49
--- /dev/null
+++ b/llparse-frontend/src/node/base.ts
@@ -0,0 +1,46 @@
+import { IUniqueName } from '../utils';
+import { IWrap } from '../wrap';
+import { Slot } from './slot';
+
+export interface IReadonlyOtherwiseEdge {
+  readonly node: IWrap<Node>;
+  readonly noAdvance: boolean;
+  readonly value: number | undefined;
+}
+
+interface IOtherwiseEdge {
+  node: IWrap<Node>;
+  readonly noAdvance: boolean;
+  readonly value: number | undefined;
+}
+
+export abstract class Node {
+  private privOtherwise: IOtherwiseEdge | undefined;
+  private privSlots: ReadonlyArray<Slot> | undefined;
+
+  constructor(public readonly id: IUniqueName) {
+  }
+
+  public setOtherwise(node: IWrap<Node>, noAdvance: boolean, value?: number) {
+    this.privOtherwise = { node, noAdvance, value };
+  }
+
+  public get otherwise(): IReadonlyOtherwiseEdge | undefined {
+    return this.privOtherwise;
+  }
+
+  public *getSlots() {
+    if (this.privSlots === undefined) {
+      this.privSlots = Array.from(this.buildSlots());
+    }
+
+    yield* this.privSlots;
+  }
+
+  protected *buildSlots() {
+    const otherwise = this.privOtherwise;
+    if (otherwise !== undefined) {
+      yield new Slot(otherwise.node, (value) => otherwise.node = value);
+    }
+  }
+}