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Packs ECMAScript/CommonJs/AMD modules for the browser. Allows you to split your codebase into multiple bundles, which can be loaded on demand. Supports loaders to preprocess files, i.e. json, jsx, es7, css, less, ... and your custom stuff.
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/*
	MIT License http://www.opensource.org/licenses/mit-license.php
*/

"use strict";

const path = require("path");

const WINDOWS_ABS_PATH_REGEXP = /^[a-zA-Z]:[\\/]/;
const SEGMENTS_SPLIT_REGEXP = /([|!])/;
const WINDOWS_PATH_SEPARATOR_REGEXP = /\\/g;

/**
 * @typedef {object} MakeRelativePathsCache
 * @property {Map>=} relativePaths
 */

/**
 * @param {string} relativePath relative path
 * @returns {string} request
 */
const relativePathToRequest = relativePath => {
	if (relativePath === "") return "./.";
	if (relativePath === "..") return "../.";
	if (relativePath.startsWith("../")) return relativePath;
	return `./${relativePath}`;
};

/**
 * @param {string} context context for relative path
 * @param {string} maybeAbsolutePath path to make relative
 * @returns {string} relative path in request style
 */
const absoluteToRequest = (context, maybeAbsolutePath) => {
	if (maybeAbsolutePath[0] === "/") {
		if (
			maybeAbsolutePath.length > 1 &&
			maybeAbsolutePath[maybeAbsolutePath.length - 1] === "/"
		) {
			// this 'path' is actually a regexp generated by dynamic requires.
			// Don't treat it as an absolute path.
			return maybeAbsolutePath;
		}

		const querySplitPos = maybeAbsolutePath.indexOf("?");
		let resource =
			querySplitPos === -1
				? maybeAbsolutePath
				: maybeAbsolutePath.slice(0, querySplitPos);
		resource = relativePathToRequest(path.posix.relative(context, resource));
		return querySplitPos === -1
			? resource
			: resource + maybeAbsolutePath.slice(querySplitPos);
	}

	if (WINDOWS_ABS_PATH_REGEXP.test(maybeAbsolutePath)) {
		const querySplitPos = maybeAbsolutePath.indexOf("?");
		let resource =
			querySplitPos === -1
				? maybeAbsolutePath
				: maybeAbsolutePath.slice(0, querySplitPos);
		resource = path.win32.relative(context, resource);
		if (!WINDOWS_ABS_PATH_REGEXP.test(resource)) {
			resource = relativePathToRequest(
				resource.replace(WINDOWS_PATH_SEPARATOR_REGEXP, "/")
			);
		}
		return querySplitPos === -1
			? resource
			: resource + maybeAbsolutePath.slice(querySplitPos);
	}

	// not an absolute path
	return maybeAbsolutePath;
};

/**
 * @param {string} context context for relative path
 * @param {string} relativePath path
 * @returns {string} absolute path
 */
const requestToAbsolute = (context, relativePath) => {
	if (relativePath.startsWith("./") || relativePath.startsWith("../"))
		return path.join(context, relativePath);
	return relativePath;
};

const makeCacheable = realFn => {
	/** @type {WeakMap>} */
	const cache = new WeakMap();

	const getCache = associatedObjectForCache => {
		const entry = cache.get(associatedObjectForCache);
		if (entry !== undefined) return entry;
		/** @type {Map} */
		const map = new Map();
		cache.set(associatedObjectForCache, map);
		return map;
	};

	/**
	 * @param {string} str the path with query and fragment
	 * @param {object=} associatedObjectForCache an object to which the cache will be attached
	 * @returns {ParsedResource} parsed parts
	 */
	const fn = (str, associatedObjectForCache) => {
		if (!associatedObjectForCache) return realFn(str);
		const cache = getCache(associatedObjectForCache);
		const entry = cache.get(str);
		if (entry !== undefined) return entry;
		const result = realFn(str);
		cache.set(str, result);
		return result;
	};

	fn.bindCache = associatedObjectForCache => {
		const cache = getCache(associatedObjectForCache);
		return str => {
			const entry = cache.get(str);
			if (entry !== undefined) return entry;
			const result = realFn(str);
			cache.set(str, result);
			return result;
		};
	};

	return fn;
};

const makeCacheableWithContext = fn => {
	/** @type {WeakMap>>} */
	const cache = new WeakMap();

	/**
	 * @param {string} context context used to create relative path
	 * @param {string} identifier identifier used to create relative path
	 * @param {object=} associatedObjectForCache an object to which the cache will be attached
	 * @returns {string} the returned relative path
	 */
	const cachedFn = (context, identifier, associatedObjectForCache) => {
		if (!associatedObjectForCache) return fn(context, identifier);

		let innerCache = cache.get(associatedObjectForCache);
		if (innerCache === undefined) {
			innerCache = new Map();
			cache.set(associatedObjectForCache, innerCache);
		}

		let cachedResult;
		let innerSubCache = innerCache.get(context);
		if (innerSubCache === undefined) {
			innerCache.set(context, (innerSubCache = new Map()));
		} else {
			cachedResult = innerSubCache.get(identifier);
		}

		if (cachedResult !== undefined) {
			return cachedResult;
		} else {
			const result = fn(context, identifier);
			innerSubCache.set(identifier, result);
			return result;
		}
	};

	/**
	 * @param {object=} associatedObjectForCache an object to which the cache will be attached
	 * @returns {function(string, string): string} cached function
	 */
	cachedFn.bindCache = associatedObjectForCache => {
		let innerCache;
		if (associatedObjectForCache) {
			innerCache = cache.get(associatedObjectForCache);
			if (innerCache === undefined) {
				innerCache = new Map();
				cache.set(associatedObjectForCache, innerCache);
			}
		} else {
			innerCache = new Map();
		}

		/**
		 * @param {string} context context used to create relative path
		 * @param {string} identifier identifier used to create relative path
		 * @returns {string} the returned relative path
		 */
		const boundFn = (context, identifier) => {
			let cachedResult;
			let innerSubCache = innerCache.get(context);
			if (innerSubCache === undefined) {
				innerCache.set(context, (innerSubCache = new Map()));
			} else {
				cachedResult = innerSubCache.get(identifier);
			}

			if (cachedResult !== undefined) {
				return cachedResult;
			} else {
				const result = fn(context, identifier);
				innerSubCache.set(identifier, result);
				return result;
			}
		};

		return boundFn;
	};

	/**
	 * @param {string} context context used to create relative path
	 * @param {object=} associatedObjectForCache an object to which the cache will be attached
	 * @returns {function(string): string} cached function
	 */
	cachedFn.bindContextCache = (context, associatedObjectForCache) => {
		let innerSubCache;
		if (associatedObjectForCache) {
			let innerCache = cache.get(associatedObjectForCache);
			if (innerCache === undefined) {
				innerCache = new Map();
				cache.set(associatedObjectForCache, innerCache);
			}

			innerSubCache = innerCache.get(context);
			if (innerSubCache === undefined) {
				innerCache.set(context, (innerSubCache = new Map()));
			}
		} else {
			innerSubCache = new Map();
		}

		/**
		 * @param {string} identifier identifier used to create relative path
		 * @returns {string} the returned relative path
		 */
		const boundFn = identifier => {
			const cachedResult = innerSubCache.get(identifier);
			if (cachedResult !== undefined) {
				return cachedResult;
			} else {
				const result = fn(context, identifier);
				innerSubCache.set(identifier, result);
				return result;
			}
		};

		return boundFn;
	};

	return cachedFn;
};

/**
 *
 * @param {string} context context for relative path
 * @param {string} identifier identifier for path
 * @returns {string} a converted relative path
 */
const _makePathsRelative = (context, identifier) => {
	return identifier
		.split(SEGMENTS_SPLIT_REGEXP)
		.map(str => absoluteToRequest(context, str))
		.join("");
};

exports.makePathsRelative = makeCacheableWithContext(_makePathsRelative);

/**
 *
 * @param {string} context context for relative path
 * @param {string} identifier identifier for path
 * @returns {string} a converted relative path
 */
const _makePathsAbsolute = (context, identifier) => {
	return identifier
		.split(SEGMENTS_SPLIT_REGEXP)
		.map(str => requestToAbsolute(context, str))
		.join("");
};

exports.makePathsAbsolute = makeCacheableWithContext(_makePathsAbsolute);

/**
 * @param {string} context absolute context path
 * @param {string} request any request string may containing absolute paths, query string, etc.
 * @returns {string} a new request string avoiding absolute paths when possible
 */
const _contextify = (context, request) => {
	return request
		.split("!")
		.map(r => absoluteToRequest(context, r))
		.join("!");
};

const contextify = makeCacheableWithContext(_contextify);
exports.contextify = contextify;

/**
 * @param {string} context absolute context path
 * @param {string} request any request string
 * @returns {string} a new request string using absolute paths when possible
 */
const _absolutify = (context, request) => {
	return request
		.split("!")
		.map(r => requestToAbsolute(context, r))
		.join("!");
};

const absolutify = makeCacheableWithContext(_absolutify);
exports.absolutify = absolutify;

const PATH_QUERY_FRAGMENT_REGEXP =
	/^((?:\0.|[^?#\0])*)(\?(?:\0.|[^#\0])*)?(#.*)?$/;
const PATH_QUERY_REGEXP = /^((?:\0.|[^?\0])*)(\?.*)?$/;

/** @typedef {{ resource: string, path: string, query: string, fragment: string }} ParsedResource */
/** @typedef {{ resource: string, path: string, query: string }} ParsedResourceWithoutFragment */

/**
 * @param {string} str the path with query and fragment
 * @returns {ParsedResource} parsed parts
 */
const _parseResource = str => {
	const match = PATH_QUERY_FRAGMENT_REGEXP.exec(str);
	return {
		resource: str,
		path: match[1].replace(/\0(.)/g, "$1"),
		query: match[2] ? match[2].replace(/\0(.)/g, "$1") : "",
		fragment: match[3] || ""
	};
};
exports.parseResource = makeCacheable(_parseResource);

/**
 * Parse resource, skips fragment part
 * @param {string} str the path with query and fragment
 * @returns {ParsedResourceWithoutFragment} parsed parts
 */
const _parseResourceWithoutFragment = str => {
	const match = PATH_QUERY_REGEXP.exec(str);
	return {
		resource: str,
		path: match[1].replace(/\0(.)/g, "$1"),
		query: match[2] ? match[2].replace(/\0(.)/g, "$1") : ""
	};
};
exports.parseResourceWithoutFragment = makeCacheable(
	_parseResourceWithoutFragment
);

/**
 * @param {string} filename the filename which should be undone
 * @param {string} outputPath the output path that is restored (only relevant when filename contains "..")
 * @param {boolean} enforceRelative true returns ./ for empty paths
 * @returns {string} repeated ../ to leave the directory of the provided filename to be back on output dir
 */
exports.getUndoPath = (filename, outputPath, enforceRelative) => {
	let depth = -1;
	let append = "";
	outputPath = outputPath.replace(/[\\/]$/, "");
	for (const part of filename.split(/[/\\]+/)) {
		if (part === "..") {
			if (depth > -1) {
				depth--;
			} else {
				const i = outputPath.lastIndexOf("/");
				const j = outputPath.lastIndexOf("\\");
				const pos = i < 0 ? j : j < 0 ? i : Math.max(i, j);
				if (pos < 0) return outputPath + "/";
				append = outputPath.slice(pos + 1) + "/" + append;
				outputPath = outputPath.slice(0, pos);
			}
		} else if (part !== ".") {
			depth++;
		}
	}
	return depth > 0
		? `${"../".repeat(depth)}${append}`
		: enforceRelative
			? `./${append}`
			: append;
};