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

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

"use strict";

const makeSerializable = require("./makeSerializable.js");

/**
 * @template T
 * @param {Set<T>} targetSet set where items should be added
 * @param {Set<Iterable<T>>} toMerge iterables to be merged
 * @returns {void}
 */
const merge = (targetSet, toMerge) => {
        for (const set of toMerge) {
                for (const item of set) {
                        targetSet.add(item);
                }
        }
};

/**
 * @template T
 * @param {Set<Iterable<T>>} targetSet set where iterables should be added
 * @param {Array<LazySet<T>>} toDeepMerge lazy sets to be flattened
 * @returns {void}
 */
const flatten = (targetSet, toDeepMerge) => {
        for (const set of toDeepMerge) {
                if (set._set.size > 0) targetSet.add(set._set);
                if (set._needMerge) {
                        for (const mergedSet of set._toMerge) {
                                targetSet.add(mergedSet);
                        }
                        flatten(targetSet, set._toDeepMerge);
                }
        }
};

/**
 * Like Set but with an addAll method to eventually add items from another iterable.
 * Access methods make sure that all delayed operations are executed.
 * Iteration methods deopts to normal Set performance until clear is called again (because of the chance of modifications during iteration).
 * @template T
 */
class LazySet {
        /**
         * @param {Iterable<T>=} iterable init iterable
         */
        constructor(iterable) {
                /** @type {Set<T>} */
                this._set = new Set(iterable);
                /** @type {Set<Iterable<T>>} */
                this._toMerge = new Set();
                /** @type {Array<LazySet<T>>} */
                this._toDeepMerge = [];
                this._needMerge = false;
                this._deopt = false;
        }

        _flatten() {
                flatten(this._toMerge, this._toDeepMerge);
                this._toDeepMerge.length = 0;
        }

        _merge() {
                this._flatten();
                merge(this._set, this._toMerge);
                this._toMerge.clear();
                this._needMerge = false;
        }

        _isEmpty() {
                return (
                        this._set.size === 0 &&
                        this._toMerge.size === 0 &&
                        this._toDeepMerge.length === 0
                );
        }

        get size() {
                if (this._needMerge) this._merge();
                return this._set.size;
        }

        /**
         * @param {T} item an item
         * @returns {this} itself
         */
        add(item) {
                this._set.add(item);
                return this;
        }

        /**
         * @param {Iterable<T> | LazySet<T>} iterable a immutable iterable or another immutable LazySet which will eventually be merged into the Set
         * @returns {this} itself
         */
        addAll(iterable) {
                if (this._deopt) {
                        const _set = this._set;
                        for (const item of iterable) {
                                _set.add(item);
                        }
                } else {
                        if (iterable instanceof LazySet) {
                                if (iterable._isEmpty()) return this;
                                this._toDeepMerge.push(iterable);
                                this._needMerge = true;
                                if (this._toDeepMerge.length > 100000) {
                                        this._flatten();
                                }
                        } else {
                                this._toMerge.add(iterable);
                                this._needMerge = true;
                        }
                        if (this._toMerge.size > 100000) this._merge();
                }
                return this;
        }

        clear() {
                this._set.clear();
                this._toMerge.clear();
                this._toDeepMerge.length = 0;
                this._needMerge = false;
                this._deopt = false;
        }

        /**
         * @param {T} value an item
         * @returns {boolean} true, if the value was in the Set before
         */
        delete(value) {
                if (this._needMerge) this._merge();
                return this._set.delete(value);
        }

        entries() {
                this._deopt = true;
                if (this._needMerge) this._merge();
                return this._set.entries();
        }

        /**
         * @param {function(T, T, Set<T>): void} callbackFn function called for each entry
         * @param {any} thisArg this argument for the callbackFn
         * @returns {void}
         */
        forEach(callbackFn, thisArg) {
                this._deopt = true;
                if (this._needMerge) this._merge();
                this._set.forEach(callbackFn, thisArg);
        }

        /**
         * @param {T} item an item
         * @returns {boolean} true, when the item is in the Set
         */
        has(item) {
                if (this._needMerge) this._merge();
                return this._set.has(item);
        }

        keys() {
                this._deopt = true;
                if (this._needMerge) this._merge();
                return this._set.keys();
        }

        values() {
                this._deopt = true;
                if (this._needMerge) this._merge();
                return this._set.values();
        }

        [Symbol.iterator]() {
                this._deopt = true;
                if (this._needMerge) this._merge();
                return this._set[Symbol.iterator]();
        }

        /* istanbul ignore next */
        get [Symbol.toStringTag]() {
                return "LazySet";
        }

        serialize({ write }) {
                if (this._needMerge) this._merge();
                write(this._set.size);
                for (const item of this._set) write(item);
        }

        static deserialize({ read }) {
                const count = read();
                const items = [];
                for (let i = 0; i < count; i++) {
                        items.push(read());
                }
                return new LazySet(items);
        }
}

makeSerializable(LazySet, "webpack/lib/util/LazySet");

module.exports = LazySet;