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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
	Author Tobias Koppers @sokra and Zackary Jackson @ScriptedAlchemy
*/

"use strict";

const { RawSource } = require("webpack-sources");
const Module = require("../Module");
const { WEBPACK_MODULE_TYPE_FALLBACK } = require("../ModuleTypeConstants");
const RuntimeGlobals = require("../RuntimeGlobals");
const Template = require("../Template");
const makeSerializable = require("../util/makeSerializable");
const FallbackItemDependency = require("./FallbackItemDependency");

/** @typedef {import("../../declarations/WebpackOptions").WebpackOptionsNormalized} WebpackOptions */
/** @typedef {import("../Chunk")} Chunk */
/** @typedef {import("../ChunkGraph")} ChunkGraph */
/** @typedef {import("../ChunkGroup")} ChunkGroup */
/** @typedef {import("../Compilation")} Compilation */
/** @typedef {import("../Module").CodeGenerationContext} CodeGenerationContext */
/** @typedef {import("../Module").CodeGenerationResult} CodeGenerationResult */
/** @typedef {import("../Module").LibIdentOptions} LibIdentOptions */
/** @typedef {import("../Module").NeedBuildContext} NeedBuildContext */
/** @typedef {import("../Module").SourceTypes} SourceTypes */
/** @typedef {import("../RequestShortener")} RequestShortener */
/** @typedef {import("../ResolverFactory").ResolverWithOptions} ResolverWithOptions */
/** @typedef {import("../WebpackError")} WebpackError */
/** @typedef {import("../serialization/ObjectMiddleware").ObjectDeserializerContext} ObjectDeserializerContext */
/** @typedef {import("../serialization/ObjectMiddleware").ObjectSerializerContext} ObjectSerializerContext */
/** @typedef {import("../util/Hash")} Hash */
/** @typedef {import("../util/fs").InputFileSystem} InputFileSystem */

const TYPES = new Set(["javascript"]);
const RUNTIME_REQUIREMENTS = new Set([RuntimeGlobals.module]);

class FallbackModule extends Module {
	/**
	 * @param {string[]} requests list of requests to choose one
	 */
	constructor(requests) {
		super(WEBPACK_MODULE_TYPE_FALLBACK);
		this.requests = requests;
		this._identifier = `fallback ${this.requests.join(" ")}`;
	}

	/**
	 * @returns {string} a unique identifier of the module
	 */
	identifier() {
		return this._identifier;
	}

	/**
	 * @param {RequestShortener} requestShortener the request shortener
	 * @returns {string} a user readable identifier of the module
	 */
	readableIdentifier(requestShortener) {
		return this._identifier;
	}

	/**
	 * @param {LibIdentOptions} options options
	 * @returns {string | null} an identifier for library inclusion
	 */
	libIdent(options) {
		return `${this.layer ? `(${this.layer})/` : ""}webpack/container/fallback/${
			this.requests[0]
		}/and ${this.requests.length - 1} more`;
	}

	/**
	 * @param {Chunk} chunk the chunk which condition should be checked
	 * @param {Compilation} compilation the compilation
	 * @returns {boolean} true, if the chunk is ok for the module
	 */
	chunkCondition(chunk, { chunkGraph }) {
		return chunkGraph.getNumberOfEntryModules(chunk) > 0;
	}

	/**
	 * @param {NeedBuildContext} context context info
	 * @param {function((WebpackError | null)=, boolean=): void} callback callback function, returns true, if the module needs a rebuild
	 * @returns {void}
	 */
	needBuild(context, callback) {
		callback(null, !this.buildInfo);
	}

	/**
	 * @param {WebpackOptions} options webpack options
	 * @param {Compilation} compilation the compilation
	 * @param {ResolverWithOptions} resolver the resolver
	 * @param {InputFileSystem} fs the file system
	 * @param {function(WebpackError=): void} callback callback function
	 * @returns {void}
	 */
	build(options, compilation, resolver, fs, callback) {
		this.buildMeta = {};
		this.buildInfo = {
			strict: true
		};

		this.clearDependenciesAndBlocks();
		for (const request of this.requests)
			this.addDependency(new FallbackItemDependency(request));

		callback();
	}

	/**
	 * @param {string=} type the source type for which the size should be estimated
	 * @returns {number} the estimated size of the module (must be non-zero)
	 */
	size(type) {
		return this.requests.length * 5 + 42;
	}

	/**
	 * @returns {SourceTypes} types available (do not mutate)
	 */
	getSourceTypes() {
		return TYPES;
	}

	/**
	 * @param {CodeGenerationContext} context context for code generation
	 * @returns {CodeGenerationResult} result
	 */
	codeGeneration({ runtimeTemplate, moduleGraph, chunkGraph }) {
		const ids = this.dependencies.map(dep =>
			chunkGraph.getModuleId(/** @type {Module} */ (moduleGraph.getModule(dep)))
		);
		const code = Template.asString([
			`var ids = ${JSON.stringify(ids)};`,
			"var error, result, i = 0;",
			`var loop = ${runtimeTemplate.basicFunction("next", [
				"while(i < ids.length) {",
				Template.indent([
					`try { next = ${RuntimeGlobals.require}(ids[i++]); } catch(e) { return handleError(e); }`,
					"if(next) return next.then ? next.then(handleResult, handleError) : handleResult(next);"
				]),
				"}",
				"if(error) throw error;"
			])}`,
			`var handleResult = ${runtimeTemplate.basicFunction("result", [
				"if(result) return result;",
				"return loop();"
			])};`,
			`var handleError = ${runtimeTemplate.basicFunction("e", [
				"error = e;",
				"return loop();"
			])};`,
			"module.exports = loop();"
		]);
		const sources = new Map();
		sources.set("javascript", new RawSource(code));
		return { sources, runtimeRequirements: RUNTIME_REQUIREMENTS };
	}

	/**
	 * @param {ObjectSerializerContext} context context
	 */
	serialize(context) {
		const { write } = context;
		write(this.requests);
		super.serialize(context);
	}

	/**
	 * @param {ObjectDeserializerContext} context context
	 * @returns {FallbackModule} deserialized fallback module
	 */
	static deserialize(context) {
		const { read } = context;
		const obj = new FallbackModule(read());
		obj.deserialize(context);
		return obj;
	}
}

makeSerializable(FallbackModule, "webpack/lib/container/FallbackModule");

module.exports = FallbackModule;