ckeditor/ckeditor5-utils

/**
 * @license Copyright (c) 2003-2020, CKSource - Frederico Knabben. All rights reserved.
 * For licensing, see LICENSE.md or https://ckeditor.com/legal/ckeditor-oss-license
 */

/**
 * @module utils/arestructuresconnected
 */

/* globals EventTarget, Event */

/**
 * Traverses both structures to find out whether there is a reference that is shared between both structures.
 *
 * @param {Object|Array} obj1
 * @param {Object|Array} obj2
 */
export default function areConnectedThroughProperties( obj1, obj2 ) {
    if ( obj1 === obj2 && isObject( obj1 ) ) {
        return true;
    }

    const subNodes1 = getSubNodes( obj1 );
    const subNodes2 = getSubNodes( obj2 );

    for ( const node of subNodes1 ) {
        if ( subNodes2.has( node ) ) {
            return true;
        }
    }

    return false;
}

// Traverses JS structure and stores all sub-nodes, including the head node.
// It walks into each iterable structures with the `try catch` block to omit errors that might be thrown during
// tree walking. All primitives, functions and built-ins are skipped.
function getSubNodes( head ) {
    const nodes = [ head ];

    // Nodes are stored to prevent infinite looping.
    const subNodes = new Set();

    while ( nodes.length > 0 ) {
        const node = nodes.shift();

        if ( subNodes.has( node ) || shouldNodeBeSkipped( node ) ) {
            continue;
        }

        subNodes.add( node );

        // Handle arrays, maps, sets, custom collections that implements `[ Symbol.iterator ]()`, etc.
        if ( node[ Symbol.iterator ] ) {
            // The custom editor iterators might cause some problems if the editor is crashed.
            try {
                nodes.push( ...node );
            } catch ( err ) {
                // eslint-disable-line no-empty
            }
        } else {
            nodes.push( ...Object.values( node ) );
        }
    }

    return subNodes;
}

function shouldNodeBeSkipped( node ) {
    const type = Object.prototype.toString.call( node );

    return (
        type === '[object Number]' ||
        type === '[object Boolean]' ||
        type === '[object String]' ||
        type === '[object Symbol]' ||
        type === '[object Function]' ||
        type === '[object Date]' ||
        type === '[object RegExp]' ||

        node === undefined ||
        node === null ||

        // Skip native DOM objects, e.g. Window, nodes, events, etc.
        node instanceof EventTarget ||
        node instanceof Event
    );
}

function isObject( structure ) {
    return typeof structure === 'object' && structure !== null;
}