source: trip-planner-front/node_modules/webpack/lib/util/ArrayQueue.js

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

"use strict";

/**
 * @template T
 */
class ArrayQueue {
        /**
         * @param {Iterable<T>=} items The initial elements.
         */
        constructor(items) {
                /** @private @type {T[]} */
                this._list = items ? Array.from(items) : [];
                /** @private @type {T[]} */
                this._listReversed = [];
        }

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

        /**
         * Empties the queue.
         */
        clear() {
                this._list.length = 0;
                this._listReversed.length = 0;
        }

        /**
         * Appends the specified element to this queue.
         * @param {T} item The element to add.
         * @returns {void}
         */
        enqueue(item) {
                this._list.push(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() {
                if (this._listReversed.length === 0) {
                        if (this._list.length === 0) return undefined;
                        if (this._list.length === 1) return this._list.pop();
                        if (this._list.length < 16) return this._list.shift();
                        const temp = this._listReversed;
                        this._listReversed = this._list;
                        this._listReversed.reverse();
                        this._list = temp;
                }
                return this._listReversed.pop();
        }

        /**
         * Finds and removes an item
         * @param {T} item the item
         * @returns {void}
         */
        delete(item) {
                const i = this._list.indexOf(item);
                if (i >= 0) {
                        this._list.splice(i, 1);
                } else {
                        const i = this._listReversed.indexOf(item);
                        if (i >= 0) this._listReversed.splice(i, 1);
                }
        }

        [Symbol.iterator]() {
                let i = -1;
                let reversed = false;
                return {
                        next: () => {
                                if (!reversed) {
                                        i++;
                                        if (i < this._list.length) {
                                                return {
                                                        done: false,
                                                        value: this._list[i]
                                                };
                                        }
                                        reversed = true;
                                        i = this._listReversed.length;
                                }
                                i--;
                                if (i < 0) {
                                        return {
                                                done: true,
                                                value: undefined
                                        };
                                }
                                return {
                                        done: false,
                                        value: this._listReversed[i]
                                };
                        }
                };
        }
}

module.exports = ArrayQueue;