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

/*
        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 */

/**
 * Adds connection states.
 * @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;
};

/**
 * Intersect connection states.
 * @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 {
        /**
         * Creates an instance of 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=} condition condition for the connection
         */
        constructor(
                originModule,
                dependency,
                module,
                explanation,
                weak = false,
                condition = undefined
        ) {
                /** @type {Module | null} */
                this.originModule = originModule;
                /** @type {Module | null} */
                this.resolvedOriginModule = originModule;
                /** @type {Dependency | null} */
                this.dependency = dependency;
                /** @type {Module} */
                this.resolvedModule = module;
                /** @type {Module} */
                this.module = module;
                /** @type {boolean | undefined} */
                this.weak = weak;
                /** @type {boolean} */
                this.conditional = Boolean(condition);
                /** @type {boolean} */
                this._active = condition !== false;
                /** @type {false | null | GetConditionFn | undefined} */
                this.condition = condition || undefined;
                /** @type {Set<string> | 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;
        }

        /**
         * Adds the provided condition to the module graph connection.
         * @param {GetConditionFn} condition condition for the connection
         * @returns {void}
         */
        addCondition(condition) {
                if (this.conditional) {
                        const old =
                                /** @type {GetConditionFn} */
                                (this.condition);
                        /** @type {GetConditionFn} */
                        (this.condition) = (c, r) =>
                                intersectConnectionStates(old(c, r), condition(c, r));
                } else if (this._active) {
                        this.conditional = true;
                        this.condition = condition;
                }
        }

        /**
         * Adds the provided explanation to the module graph connection.
         * @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 [...this.explanations].join(" ");
        }

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

                return (
                        /** @type {GetConditionFn} */ (this.condition)(this, runtime) !== false
                );
        }

        /**
         * Checks whether this module graph connection is target active.
         * @param {RuntimeSpec} runtime the runtime
         * @returns {boolean} true, if the connection is active
         */
        isTargetActive(runtime) {
                if (!this.conditional) return this._active;
                return (
                        /** @type {GetConditionFn} */ (this.condition)(this, runtime) === true
                );
        }

        /**
         * Returns true: fully active, false: inactive, TRANSITIVE: direct module inactive, but transitive connection maybe active.
         * @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 {GetConditionFn} */ (this.condition)(this, runtime);
        }

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

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

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