/*
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MIT License http://www.opensource.org/licenses/mit-license.php
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Author Ivan Kopeykin @vankop
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*/
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"use strict";
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/**
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* Tracks values across a stack of nested sets where child scopes can add new
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* values without mutating the sets created by their parents.
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* @template T
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*/
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class AppendOnlyStackedSet {
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/**
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* Seeds the stacked set with an optional chain of previously created scope
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* layers.
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* @param {Set<T>[]} sets an optional array of sets
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*/
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constructor(sets = []) {
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/** @type {Set<T>[]} */
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this._sets = sets;
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/** @type {Set<T> | undefined} */
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this._current = undefined;
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}
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/**
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* Adds a value to the current scope layer, creating that layer lazily when
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* the first write occurs.
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* @param {T} el element
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*/
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add(el) {
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if (!this._current) {
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this._current = new Set();
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this._sets.push(this._current);
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}
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this._current.add(el);
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}
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/**
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* Checks whether a value is present in any scope layer currently visible to
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* this stacked set.
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* @param {T} el element
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* @returns {boolean} result
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*/
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has(el) {
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for (const set of this._sets) {
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if (set.has(el)) return true;
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}
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return false;
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}
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/**
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* Removes every scope layer and any values accumulated in them.
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*/
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clear() {
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this._sets = [];
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if (this._current) {
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this._current = undefined;
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}
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}
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/**
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* Creates a child stacked set that shares the existing scope history while
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* allowing subsequent additions to be recorded in its own new layer.
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* @returns {AppendOnlyStackedSet<T>} child
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*/
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createChild() {
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return new AppendOnlyStackedSet(this._sets.length ? [...this._sets] : []);
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}
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/**
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* Iterates over the stacked sets from newest to oldest so consumers can
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* inspect recently added values first.
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* @returns {Iterator<T>} iterable iterator
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*/
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[Symbol.iterator]() {
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const iterators = this._sets.map((map) => map[Symbol.iterator]());
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let current = iterators.pop();
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return {
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next() {
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if (!current) return { done: true, value: undefined };
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let result = current.next();
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while (result.done && iterators.length > 0) {
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current = /** @type {SetIterator<T>} */ (iterators.pop());
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result = current.next();
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}
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return result;
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}
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};
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}
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}
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module.exports = AppendOnlyStackedSet;
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