ckeditor/ckeditor5-engine

/**
 * @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 engine/view/emptyelement
 */

import Element from './element';
import CKEditorError from '@ckeditor/ckeditor5-utils/src/ckeditorerror';
import Node from './node';

/**
 * Empty element class. It is used to represent elements that cannot contain any child nodes (for example `<img>` elements).
 *
 * To create a new empty element use the
 * {@link module:engine/view/downcastwriter~DowncastWriter#createEmptyElement `downcastWriter#createEmptyElement()`} method.
 *
 * @extends module:engine/view/element~Element
 */
export default class EmptyElement extends Element {
    /**
     * Creates new instance of EmptyElement.
     *
     * Throws {@link module:utils/ckeditorerror~CKEditorError CKEditorError} `view-emptyelement-cannot-add` when third parameter is passed,
     * to inform that usage of EmptyElement is incorrect (adding child nodes to EmptyElement is forbidden).
     *
     * @see module:engine/view/downcastwriter~DowncastWriter#createEmptyElement
     * @protected
     * @param {module:engine/view/document~Document} document The document instance to which this element belongs.
     * @param {String} name Node name.
     * @param {Object|Iterable} [attrs] Collection of attributes.
     * @param {module:engine/view/node~Node|Iterable.<module:engine/view/node~Node>} [children]
     * A list of nodes to be inserted into created element.
     */
    constructor( document, name, attrs, children ) {
        super( document, name, attrs, children );

        /**
         * Returns `null` because filler is not needed for EmptyElements.
         *
         * @method #getFillerOffset
         * @returns {null} Always returns null.
         */
        this.getFillerOffset = getFillerOffset;
    }

    /**
     * Checks whether this object is of the given.
     *
     *        emptyElement.is( 'emptyElement' ); // -> true
     *        emptyElement.is( 'element' ); // -> true
     *        emptyElement.is( 'node' ); // -> true
     *        emptyElement.is( 'view:emptyElement' ); // -> true
     *        emptyElement.is( 'view:element' ); // -> true
     *        emptyElement.is( 'view:node' ); // -> true
     *
     *        emptyElement.is( 'model:element' ); // -> false
     *        emptyElement.is( 'documentFragment' ); // -> false
     *
     * Assuming that the object being checked is an empty element, you can also check its
     * {@link module:engine/view/emptyelement~EmptyElement#name name}:
     *
     *        emptyElement.is( 'img' ); // -> true if this is a img element
     *        emptyElement.is( 'emptyElement', 'img' ); // -> same as above
     *        text.is( 'img' ); -> false
     *
     * {@link module:engine/view/node~Node#is Check the entire list of view objects} which implement the `is()` method.
     *
     * @param {String} type Type to check when `name` parameter is present.
     * Otherwise, it acts like the `name` parameter.
     * @param {String} [name] Element name.
     * @returns {Boolean}
     */
    is( type, name = null ) {
        if ( !name ) {
            return type === 'emptyElement' || type === 'view:emptyElement' ||
                // From super.is(). This is highly utilised method and cannot call super. See ckeditor/ckeditor5#6529.
                type === this.name || type === 'view:' + this.name ||
                type === 'element' || type === 'view:element' ||
                type === 'node' || type === 'view:node';
        } else {
            return name === this.name && (
                type === 'emptyElement' || type === 'view:emptyElement' ||
                type === 'element' || type === 'view:element'
            );
        }
    }

    /**
     * Overrides {@link module:engine/view/element~Element#_insertChild} method.
     * Throws {@link module:utils/ckeditorerror~CKEditorError CKEditorError} `view-emptyelement-cannot-add` to prevent
     * adding any child nodes to EmptyElement.
     *
     * @protected
     */
    _insertChild( index, nodes ) {
        if ( nodes && ( nodes instanceof Node || Array.from( nodes ).length > 0 ) ) {
            /**
             * Cannot add children to {@link module:engine/view/emptyelement~EmptyElement}.
             *
             * @error view-emptyelement-cannot-add
             */
            throw new CKEditorError(
                'view-emptyelement-cannot-add: Cannot add child nodes to EmptyElement instance.',
                [ this, nodes ]
            );
        }
    }
}

// Returns `null` because block filler is not needed for EmptyElements.
//
// @returns {null}
function getFillerOffset() {
    return null;
}