ckeditor/ckeditor5-heading

/**
 * @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 heading/headingcommand
 */

import Command from '@ckeditor/ckeditor5-core/src/command';
import first from '@ckeditor/ckeditor5-utils/src/first';

/**
 * The heading command. It is used by the {@link module:heading/heading~Heading heading feature} to apply headings.
 *
 * @extends module:core/command~Command
 */
export default class HeadingCommand extends Command {
    /**
     * Creates an instance of the command.
     *
     * @param {module:core/editor/editor~Editor} editor Editor instance.
     * @param {Array.<String>} modelElements Names of the element which this command can apply in the model.
     */
    constructor( editor, modelElements ) {
        super( editor );

        /**
         * If the selection starts in a heading (which {@link #modelElements is supported by this command})
         * the value is set to the name of that heading model element.
         * It is  set to `false` otherwise.
         *
         * @observable
         * @readonly
         * @member {Boolean|String} #value
         */

        /**
         * Set of defined model's elements names that this command support.
         * See {@link module:heading/heading~HeadingOption}.
         *
         * @readonly
         * @member {Array.<String>}
         */
        this.modelElements = modelElements;
    }

    /**
     * @inheritDoc
     */
    refresh() {
        const block = first( this.editor.model.document.selection.getSelectedBlocks() );

        this.value = !!block && this.modelElements.includes( block.name ) && block.name;
        this.isEnabled = !!block && this.modelElements.some( heading => checkCanBecomeHeading( block, heading, this.editor.model.schema ) );
    }

    /**
     * Executes the command. Applies the heading to the selected blocks or, if the first selected
     * block is a heading already, turns selected headings (of this level only) to paragraphs.
     *
     * @param {Object} options
     * @param {String} options.value Name of the element which this command will apply in the model.
     * @fires execute
     */
    execute( options ) {
        const model = this.editor.model;
        const document = model.document;

        const modelElement = options.value;

        model.change( writer => {
            const blocks = Array.from( document.selection.getSelectedBlocks() )
                .filter( block => {
                    return checkCanBecomeHeading( block, modelElement, model.schema );
                } );

            for ( const block of blocks ) {
                if ( !block.is( modelElement ) ) {
                    writer.rename( block, modelElement );
                }
            }
        } );
    }
}

// Checks whether the given block can be replaced by a specific heading.
//
// @private
// @param {module:engine/model/element~Element} block A block to be tested.
// @param {module:heading/headingcommand~HeadingCommand#modelElement} heading Command element name in the model.
// @param {module:engine/model/schema~Schema} schema The schema of the document.
// @returns {Boolean}
function checkCanBecomeHeading( block, heading, schema ) {
    return schema.checkChild( block.parent, heading ) && !schema.isObject( block );
}