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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
*/

"use strict";

/** @typedef {import("./Dependency")} Dependency */
/** @typedef {import("./Dependency").GetConditionFn} GetConditionFn */
/** @typedef {import("./Module")} Module */
/** @typedef {import("./util/runtime").RuntimeSpec} RuntimeSpec */

/**
 * Module itself is not connected, but transitive modules are connected transitively.
 */
const TRANSITIVE_ONLY = Symbol("transitive only");

/**
 * While determining the active state, this flag is used to signal a circular connection.
 */
const CIRCULAR_CONNECTION = Symbol("circular connection");

/** @typedef {boolean | typeof TRANSITIVE_ONLY | typeof CIRCULAR_CONNECTION} ConnectionState */

/**
 * @param {ConnectionState} a first
 * @param {ConnectionState} b second
 * @returns {ConnectionState} merged
 */
const addConnectionStates = (a, b) => {
	if (a === true || b === true) return true;
	if (a === false) return b;
	if (b === false) return a;
	if (a === TRANSITIVE_ONLY) return b;
	if (b === TRANSITIVE_ONLY) return a;
	return a;
};

/**
 * @param {ConnectionState} a first
 * @param {ConnectionState} b second
 * @returns {ConnectionState} intersected
 */
const intersectConnectionStates = (a, b) => {
	if (a === false || b === false) return false;
	if (a === true) return b;
	if (b === true) return a;
	if (a === CIRCULAR_CONNECTION) return b;
	if (b === CIRCULAR_CONNECTION) return a;
	return a;
};

class ModuleGraphConnection {
	/**
	 * @param {Module|null} originModule the referencing module
	 * @param {Dependency|null} dependency the referencing dependency
	 * @param {Module} module the referenced module
	 * @param {string=} explanation some extra detail
	 * @param {boolean=} weak the reference is weak
	 * @param {false | null | GetConditionFn | undefined} condition condition for the connection
	 */
	constructor(
		originModule,
		dependency,
		module,
		explanation,
		weak = false,
		condition = undefined
	) {
		this.originModule = originModule;
		this.resolvedOriginModule = originModule;
		this.dependency = dependency;
		this.resolvedModule = module;
		this.module = module;
		this.weak = weak;
		this.conditional = !!condition;
		this._active = condition !== false;
		/** @type {(function(ModuleGraphConnection, RuntimeSpec): ConnectionState) | undefined} */
		this.condition = condition || undefined;
		/** @type {Set | undefined} */
		this.explanations = undefined;
		if (explanation) {
			this.explanations = new Set();
			this.explanations.add(explanation);
		}
	}

	clone() {
		const clone = new ModuleGraphConnection(
			this.resolvedOriginModule,
			this.dependency,
			this.resolvedModule,
			undefined,
			this.weak,
			this.condition
		);
		clone.originModule = this.originModule;
		clone.module = this.module;
		clone.conditional = this.conditional;
		clone._active = this._active;
		if (this.explanations) clone.explanations = new Set(this.explanations);
		return clone;
	}

	/**
	 * @param {function(ModuleGraphConnection, RuntimeSpec): ConnectionState} condition condition for the connection
	 * @returns {void}
	 */
	addCondition(condition) {
		if (this.conditional) {
			const old =
				/** @type {(function(ModuleGraphConnection, RuntimeSpec): ConnectionState)} */
				(this.condition);
			this.condition = (c, r) =>
				intersectConnectionStates(old(c, r), condition(c, r));
		} else if (this._active) {
			this.conditional = true;
			this.condition = condition;
		}
	}

	/**
	 * @param {string} explanation the explanation to add
	 * @returns {void}
	 */
	addExplanation(explanation) {
		if (this.explanations === undefined) {
			this.explanations = new Set();
		}
		this.explanations.add(explanation);
	}

	get explanation() {
		if (this.explanations === undefined) return "";
		return Array.from(this.explanations).join(" ");
	}

	// TODO webpack 5 remove
	get active() {
		throw new Error("Use getActiveState instead");
	}

	/**
	 * @param {RuntimeSpec} runtime the runtime
	 * @returns {boolean} true, if the connection is active
	 */
	isActive(runtime) {
		if (!this.conditional) return this._active;

		return (
			/** @type {(function(ModuleGraphConnection, RuntimeSpec): ConnectionState)} */ (
				this.condition
			)(this, runtime) !== false
		);
	}

	/**
	 * @param {RuntimeSpec} runtime the runtime
	 * @returns {boolean} true, if the connection is active
	 */
	isTargetActive(runtime) {
		if (!this.conditional) return this._active;
		return (
			/** @type {(function(ModuleGraphConnection, RuntimeSpec): ConnectionState)} */ (
				this.condition
			)(this, runtime) === true
		);
	}

	/**
	 * @param {RuntimeSpec} runtime the runtime
	 * @returns {ConnectionState} true: fully active, false: inactive, TRANSITIVE: direct module inactive, but transitive connection maybe active
	 */
	getActiveState(runtime) {
		if (!this.conditional) return this._active;
		return /** @type {(function(ModuleGraphConnection, RuntimeSpec): ConnectionState)} */ (
			this.condition
		)(this, runtime);
	}

	/**
	 * @param {boolean} value active or not
	 * @returns {void}
	 */
	setActive(value) {
		this.conditional = false;
		this._active = value;
	}

	set active(value) {
		throw new Error("Use setActive instead");
	}
}

/** @typedef {typeof TRANSITIVE_ONLY} TRANSITIVE_ONLY */
/** @typedef {typeof CIRCULAR_CONNECTION} CIRCULAR_CONNECTION */

module.exports = ModuleGraphConnection;
module.exports.addConnectionStates = addConnectionStates;
module.exports.TRANSITIVE_ONLY = /** @type {typeof TRANSITIVE_ONLY} */ (
	TRANSITIVE_ONLY
);
module.exports.CIRCULAR_CONNECTION = /** @type {typeof CIRCULAR_CONNECTION} */ (
	CIRCULAR_CONNECTION
);