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

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

"use strict";

/**
 * @template K
 * @template V
 */
class StackedCacheMap {
        constructor() {
                /** @type {Map<K, V>} */
                this.map = new Map();
                /** @type {ReadonlyMap<K, V>[]} */
                this.stack = [];
        }

        /**
         * @param {ReadonlyMap<K, V>} map map to add
         * @param {boolean} immutable if 'map' is immutable and StackedCacheMap can keep referencing it
         */
        addAll(map, immutable) {
                if (immutable) {
                        this.stack.push(map);

                        // largest map should go first
                        for (let i = this.stack.length - 1; i > 0; i--) {
                                const beforeLast = this.stack[i - 1];
                                if (beforeLast.size >= map.size) break;
                                this.stack[i] = beforeLast;
                                this.stack[i - 1] = map;
                        }
                } else {
                        for (const [key, value] of map) {
                                this.map.set(key, value);
                        }
                }
        }

        /**
         * @param {K} item the key of the element to add
         * @param {V} value the value of the element to add
         * @returns {void}
         */
        set(item, value) {
                this.map.set(item, value);
        }

        /**
         * @param {K} item the item to delete
         * @returns {void}
         */
        delete(item) {
                throw new Error("Items can't be deleted from a StackedCacheMap");
        }

        /**
         * @param {K} item the item to test
         * @returns {boolean} true if the item exists in this set
         */
        has(item) {
                throw new Error(
                        "Checking StackedCacheMap.has before reading is inefficient, use StackedCacheMap.get and check for undefined"
                );
        }

        /**
         * @param {K} item the key of the element to return
         * @returns {V} the value of the element
         */
        get(item) {
                for (const map of this.stack) {
                        const value = map.get(item);
                        if (value !== undefined) return value;
                }
                return this.map.get(item);
        }

        clear() {
                this.stack.length = 0;
                this.map.clear();
        }

        get size() {
                let size = this.map.size;
                for (const map of this.stack) {
                        size += map.size;
                }
                return size;
        }

        [Symbol.iterator]() {
                const iterators = this.stack.map(map => map[Symbol.iterator]());
                let current = this.map[Symbol.iterator]();
                return {
                        next() {
                                let result = current.next();
                                while (result.done && iterators.length > 0) {
                                        current = iterators.pop();
                                        result = current.next();
                                }
                                return result;
                        }
                };
        }
}

module.exports = StackedCacheMap;