source: frontend/node_modules/enhanced-resolve/lib/UnsafeCachePlugin.js

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

"use strict";

const { isRelativeRequest } = require("./util/path");

/** @typedef {import("./Resolver")} Resolver */
/** @typedef {import("./Resolver").ResolveRequest} ResolveRequest */
/** @typedef {import("./Resolver").ResolveStepHook} ResolveStepHook */
/** @typedef {import("./Resolver").ResolveContextYield} ResolveContextYield */
/** @typedef {{ [k: string]: undefined | ResolveRequest | ResolveRequest[] }} Cache */

/**
 * @param {string} relativePath relative path from package root
 * @param {string} request relative request
 * @param {Resolver} resolver resolver instance
 * @returns {string} normalized request with a preserved leading dot
 */
function joinRelativePreservingLeadingDot(relativePath, request, resolver) {
        const normalized = resolver.join(relativePath, request);
        return isRelativeRequest(normalized) ? normalized : `./${normalized}`;
}

/**
 * @param {ResolveRequest} request request
 * @returns {string | false | undefined} normalized path
 */
function getCachePath(request) {
        if (request.descriptionFileRoot && !request.module) {
                return request.descriptionFileRoot;
        }
        return request.path;
}

/**
 * @param {ResolveRequest} request request
 * @param {Resolver} resolver resolver instance
 * @returns {string | undefined} normalized request string
 */
function getCacheRequest(request, resolver) {
        const requestString = request.request;
        if (
                !requestString ||
                !request.relativePath ||
                !isRelativeRequest(requestString)
        ) {
                return requestString;
        }
        return joinRelativePreservingLeadingDot(
                request.relativePath,
                requestString,
                resolver,
        );
}

// Cache-key separator: `\0` is safe because paths, requests, queries and
// fragments produced by `parseIdentifier` never contain a raw NUL (the
// \0-escape in identifier.js is decoded back to the original char), and the
// context, when included, is passed through `JSON.stringify`, which escapes
// any NUL to \u0000.
// const SEP = "\0";

/**
 * Build the cache id for a request. Called on every `described-resolve`
 * invocation when `unsafeCache` is on, so it's a hot path.
 *
 * Equivalent in meaning to the previous `JSON.stringify({ ... })` form, but
 * ~3–5× faster since we avoid the object allocation and JSON serializer for
 * the fields that are already plain strings.
 * @param {string} type type of cache
 * @param {ResolveRequest} request request
 * @param {boolean} withContext cache with context?
 * @param {Resolver} resolver resolver instance
 * @returns {string} cache id
 */
function getCacheId(type, request, withContext, resolver) {
        // TODO use it in the next major release, it is faster
        // const contextPart = withContext ? JSON.stringify(request.context) : "";
        // const path = getCachePath(request);
        // const cacheRequest = getCacheRequest(request, resolver);
        // return (
        //      type +
        //      SEP +
        //      contextPart +
        //      SEP +
        //      (path || "") +
        //      SEP +
        //      (request.query || "") +
        //      SEP +
        //      (request.fragment || "") +
        //      SEP +
        //      (cacheRequest || "")
        // );

        return JSON.stringify({
                type,
                context: withContext ? request.context : "",
                path: getCachePath(request),
                query: request.query,
                fragment: request.fragment,
                request: getCacheRequest(request, resolver),
        });
}

module.exports = class UnsafeCachePlugin {
        /**
         * @param {string | ResolveStepHook} source source
         * @param {(request: ResolveRequest) => boolean} filterPredicate filterPredicate
         * @param {Cache} cache cache
         * @param {boolean} withContext withContext
         * @param {string | ResolveStepHook} target target
         */
        constructor(source, filterPredicate, cache, withContext, target) {
                this.source = source;
                this.filterPredicate = filterPredicate;
                this.withContext = withContext;
                this.cache = cache;
                this.target = target;
        }

        /**
         * @param {Resolver} resolver the resolver
         * @returns {void}
         */
        apply(resolver) {
                const target = resolver.ensureHook(this.target);
                resolver
                        .getHook(this.source)
                        .tapAsync("UnsafeCachePlugin", (request, resolveContext, callback) => {
                                if (!this.filterPredicate(request)) {
                                        return resolver.doResolve(
                                                target,
                                                request,
                                                null,
                                                resolveContext,
                                                callback,
                                        );
                                }
                                const isYield = typeof resolveContext.yield === "function";
                                const cacheId = getCacheId(
                                        isYield ? "yield" : "default",
                                        request,
                                        this.withContext,
                                        resolver,
                                );
                                const cacheEntry = this.cache[cacheId];
                                if (cacheEntry) {
                                        if (isYield) {
                                                const yield_ =
                                                        /** @type {ResolveContextYield} */
                                                        (resolveContext.yield);
                                                if (Array.isArray(cacheEntry)) {
                                                        for (const result of cacheEntry) yield_(result);
                                                } else {
                                                        yield_(cacheEntry);
                                                }
                                                return callback(null, null);
                                        }
                                        return callback(null, /** @type {ResolveRequest} */ (cacheEntry));
                                }

                                /** @type {ResolveContextYield | undefined} */
                                let yieldFn;
                                /** @type {ResolveContextYield | undefined} */
                                let yield_;
                                /** @type {ResolveRequest[]} */
                                const yieldResult = [];
                                if (isYield) {
                                        yieldFn = resolveContext.yield;
                                        yield_ = (result) => {
                                                yieldResult.push(result);
                                        };
                                }

                                resolver.doResolve(
                                        target,
                                        request,
                                        null,
                                        yield_ ? { ...resolveContext, yield: yield_ } : resolveContext,
                                        (err, result) => {
                                                if (err) return callback(err);
                                                if (isYield) {
                                                        if (result) yieldResult.push(result);
                                                        for (const result of yieldResult) {
                                                                /** @type {ResolveContextYield} */
                                                                (yieldFn)(result);
                                                        }
                                                        this.cache[cacheId] = yieldResult;
                                                        return callback(null, null);
                                                }
                                                if (result) return callback(null, (this.cache[cacheId] = result));
                                                callback();
                                        },
                                );
                        });
        }
};