source: trip-planner-front/node_modules/webpack/lib/util/TupleQueue.js@ 8d391a1

/*
        MIT License http://www.opensource.org/licenses/mit-license.php
        Author Tobias Koppers @sokra
*/

"use strict";

const TupleSet = require("./TupleSet");

/**
 * @template {any[]} T
 */
class TupleQueue {
        /**
         * @param {Iterable<T>=} items The initial elements.
         */
        constructor(items) {
                /** @private @type {TupleSet<T>} */
                this._set = new TupleSet(items);
                /** @private @type {Iterator<T>} */
                this._iterator = this._set[Symbol.iterator]();
        }

        /**
         * Returns the number of elements in this queue.
         * @returns {number} The number of elements in this queue.
         */
        get length() {
                return this._set.size;
        }

        /**
         * Appends the specified element to this queue.
         * @param {T} item The element to add.
         * @returns {void}
         */
        enqueue(...item) {
                this._set.add(...item);
        }

        /**
         * Retrieves and removes the head of this queue.
         * @returns {T | undefined} The head of the queue of `undefined` if this queue is empty.
         */
        dequeue() {
                const result = this._iterator.next();
                if (result.done) {
                        if (this._set.size > 0) {
                                this._iterator = this._set[Symbol.iterator]();
                                const value = this._iterator.next().value;
                                this._set.delete(...value);
                                return value;
                        }
                        return undefined;
                }
                this._set.delete(...result.value);
                return result.value;
        }
}

module.exports = TupleQueue;