source: frontend/node_modules/webpack/lib/cache/MemoryCachePlugin.js

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

"use strict";

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

/** @typedef {import("../Cache").Data} Data */
/** @typedef {import("../Cache").Etag} Etag */
/** @typedef {import("../Compiler")} Compiler */

class MemoryCachePlugin {
        /**
         * Applies the plugin by registering its hooks on the compiler.
         * @param {Compiler} compiler the compiler instance
         * @returns {void}
         */
        apply(compiler) {
                /** @type {Map<string, { etag: Etag | null, data: Data } | null>} */
                const cache = new Map();
                compiler.cache.hooks.store.tap(
                        { name: "MemoryCachePlugin", stage: Cache.STAGE_MEMORY },
                        (identifier, etag, data) => {
                                cache.set(identifier, { etag, data });
                        }
                );
                compiler.cache.hooks.get.tap(
                        { name: "MemoryCachePlugin", stage: Cache.STAGE_MEMORY },
                        (identifier, etag, gotHandlers) => {
                                const cacheEntry = cache.get(identifier);
                                if (cacheEntry === null) {
                                        return null;
                                } else if (cacheEntry !== undefined) {
                                        return cacheEntry.etag === etag ? cacheEntry.data : null;
                                }
                                gotHandlers.push((result, callback) => {
                                        if (result === undefined) {
                                                cache.set(identifier, null);
                                        } else {
                                                cache.set(identifier, { etag, data: result });
                                        }
                                        return callback();
                                });
                        }
                );
                compiler.cache.hooks.shutdown.tap(
                        { name: "MemoryCachePlugin", stage: Cache.STAGE_MEMORY },
                        () => {
                                cache.clear();
                        }
                );
        }
}

module.exports = MemoryCachePlugin;