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import { AsyncIterator } from "https://esm.sh/asynciterator@3.7.0";
export {  ArrayIterator,  type AsyncIterator,  MappingIterator,} from "https://esm.sh/asynciterator@3.7.0";
type TreeNode<T> = {  [property: string]: T[] | TreeNode<T>;};
export type Tree<T> = T[] | TreeNode<T>;
type Subtree<T> = {  type: "node";  tree: TreeNode<T>;  parent?: Subtree<T>;  items: string[];  path: string[];  index: number;} | {  type: "leaf";  parent?: Subtree<T>;  items: T[];  path: string[];  index: number;};
export class TreeIterator<T> extends AsyncIterator<[...string[], T]> {  private _tree: Tree<T>;  private _pointer: Subtree<T>;
  constructor(tree: Tree<T>) {    super();    this._tree = tree;    this._pointer = this._buildPointerFromSource(tree);    this.readable = true;  }
  read() {    if (this.closed) {      return null;    }
    this._findNextCommonSegment();    this._findNextLeaf();
    const p = this._pointer;    if (p.type === "leaf") {      p.index++;      if (p.index < p.items.length) {        return [...p.path, p.items[p.index]] as [...string[], T];      }      if (!p.parent) {        this.close();      }    }    if (p.type === "node") {      this.close();    }
    return null;  }
  protected _buildPointerFromSource(    tree: Tree<T>,    path: string[] = [],  ): Subtree<T> {    if (tree.constructor === Object && !Array.isArray(tree)) {      return {        tree,        parent: this._pointer,        type: "node",        items: Object.keys(tree),        path,        index: -1,      };    }    if (Array.isArray(tree)) {      return {        parent: this._pointer,        type: "leaf",        items: tree,        path,        index: -1,      };    } else {      throw new Error(        "Invalid tree specified, expecting arrays in plain objects.",      );    }  }
  protected _findNextCommonSegment() {    while (this._pointer.parent !== null) {      const p = this._pointer;      if (p.type === "leaf" && p.index < p.items.length - 1) {        // Points to a leaf that is not yet exhausted        break;      }      if (p.index >= p.items.length - 1 && this._pointer.parent) {        this._pointer = this._pointer.parent!;      } else {        break;      }    }  }
  protected _findNextLeaf() {    while (this._pointer.type !== "leaf") {      const p = this._pointer;      p.index++;      if (p.index >= p.items.length) {        // no other keys present, the tree is exhausted;        break;      }      const key = p.items[p.index];      const source = this._pointer.tree[key];      this._pointer = this._buildPointerFromSource(source, [...p.path, key]);    }  }}