source: frontend/node_modules/webpack/lib/Cache.js

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

"use strict";

const { AsyncParallelHook, AsyncSeriesBailHook, SyncHook } = require("tapable");
const {
        makeWebpackError,
        makeWebpackErrorCallback
} = require("./errors/HookWebpackError");

/**
 * Cache validation token whose string representation identifies the build
 * inputs associated with a cached value.
 * @typedef {object} Etag
 * @property {() => string} toString
 */

/**
 * Completion callback used by cache operations that either fail with a `Error` or resolve with a typed result.
 * @template T
 * @callback CallbackCache
 * @param {Error | null} err
 * @param {T=} result
 * @returns {void}
 */

/** @typedef {EXPECTED_ANY} Data */

/**
 * Handler invoked after a cache read succeeds so additional cache layers can
 * react to the retrieved value.
 * @template T
 * @callback GotHandler
 * @param {T} result
 * @param {() => void} callback
 * @returns {void}
 */

/**
 * Creates a callback wrapper that waits for a fixed number of completions and
 * forwards the first error immediately.
 * @param {number} times times
 * @param {(err?: Error | null) => void} callback callback
 * @returns {(err?: Error | null) => void} callback
 */
const needCalls = (times, callback) => (err) => {
        if (--times === 0) {
                return callback(err);
        }
        if (err && times > 0) {
                times = 0;
                return callback(err);
        }
};

/**
 * Abstract cache interface backed by tapable hooks for reading, writing, idle
 * transitions, and shutdown across webpack cache implementations.
 */
class Cache {
        /**
         * Initializes the cache lifecycle hooks implemented by cache backends.
         */
        constructor() {
                this.hooks = {
                        /** @type {AsyncSeriesBailHook<[string, Etag | null, GotHandler<EXPECTED_ANY>[]], Data>} */
                        get: new AsyncSeriesBailHook(["identifier", "etag", "gotHandlers"]),
                        /** @type {AsyncParallelHook<[string, Etag | null, Data]>} */
                        store: new AsyncParallelHook(["identifier", "etag", "data"]),
                        /** @type {AsyncParallelHook<[Iterable<string>]>} */
                        storeBuildDependencies: new AsyncParallelHook(["dependencies"]),
                        /** @type {SyncHook<[]>} */
                        beginIdle: new SyncHook([]),
                        /** @type {AsyncParallelHook<[]>} */
                        endIdle: new AsyncParallelHook([]),
                        /** @type {AsyncParallelHook<[]>} */
                        shutdown: new AsyncParallelHook([])
                };
        }

        /**
         * Retrieves a cached value and lets registered `gotHandlers` observe the
         * result before the caller receives it.
         * @template T
         * @param {string} identifier the cache identifier
         * @param {Etag | null} etag the etag
         * @param {CallbackCache<T>} callback signals when the value is retrieved
         * @returns {void}
         */
        get(identifier, etag, callback) {
                /** @type {GotHandler<T>[]} */
                const gotHandlers = [];
                this.hooks.get.callAsync(identifier, etag, gotHandlers, (err, result) => {
                        if (err) {
                                callback(makeWebpackError(err, "Cache.hooks.get"));
                                return;
                        }
                        if (result === null) {
                                result = undefined;
                        }
                        if (gotHandlers.length > 1) {
                                const innerCallback = needCalls(gotHandlers.length, () =>
                                        callback(null, result)
                                );
                                for (const gotHandler of gotHandlers) {
                                        gotHandler(result, innerCallback);
                                }
                        } else if (gotHandlers.length === 1) {
                                gotHandlers[0](result, () => callback(null, result));
                        } else {
                                callback(null, result);
                        }
                });
        }

        /**
         * Stores a cache entry for the identifier and etag through the registered
         * cache backend hooks.
         * @template T
         * @param {string} identifier the cache identifier
         * @param {Etag | null} etag the etag
         * @param {T} data the value to store
         * @param {CallbackCache<void>} callback signals when the value is stored
         * @returns {void}
         */
        store(identifier, etag, data, callback) {
                this.hooks.store.callAsync(
                        identifier,
                        etag,
                        data,
                        makeWebpackErrorCallback(callback, "Cache.hooks.store")
                );
        }

        /**
         * Persists the set of build dependencies required to determine whether the
         * cache can be restored in a future compilation.
         * @param {Iterable<string>} dependencies list of all build dependencies
         * @param {CallbackCache<void>} callback signals when the dependencies are stored
         * @returns {void}
         */
        storeBuildDependencies(dependencies, callback) {
                this.hooks.storeBuildDependencies.callAsync(
                        dependencies,
                        makeWebpackErrorCallback(callback, "Cache.hooks.storeBuildDependencies")
                );
        }

        /**
         * Signals that webpack is entering an idle phase and cache backends may flush
         * or compact pending work.
         * @returns {void}
         */
        beginIdle() {
                this.hooks.beginIdle.call();
        }

        /**
         * Signals that webpack is leaving the idle phase and waits for cache
         * backends to finish any asynchronous resume work.
         * @param {CallbackCache<void>} callback signals when the call finishes
         * @returns {void}
         */
        endIdle(callback) {
                this.hooks.endIdle.callAsync(
                        makeWebpackErrorCallback(callback, "Cache.hooks.endIdle")
                );
        }

        /**
         * Shuts down every registered cache backend and waits for cleanup to finish.
         * @param {CallbackCache<void>} callback signals when the call finishes
         * @returns {void}
         */
        shutdown(callback) {
                this.hooks.shutdown.callAsync(
                        makeWebpackErrorCallback(callback, "Cache.hooks.shutdown")
                );
        }
}

Cache.STAGE_MEMORY = -10;
Cache.STAGE_DEFAULT = 0;
Cache.STAGE_DISK = 10;
Cache.STAGE_NETWORK = 20;

module.exports = Cache;