ckeditor/ckeditor5-enter

/**
 * @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 enter/entercommand
 */

import Command from '@ckeditor/ckeditor5-core/src/command';
import { getCopyOnEnterAttributes } from './utils';

/**
 * Enter command. It is used by the {@link module:enter/enter~Enter Enter feature} to handle the <kbd>Enter</kbd> key.
 *
 * @extends module:core/command~Command
 */
export default class EnterCommand extends Command {
    /**
     * @inheritDoc
     */
    execute() {
        const model = this.editor.model;
        const doc = model.document;

        model.change( writer => {
            enterBlock( this.editor.model, writer, doc.selection, model.schema );
            this.fire( 'afterExecute', { writer } );
        } );
    }
}

// Creates a new block in the way that the <kbd>Enter</kbd> key is expected to work.
//
// @param {module:engine/model~Model} model
// @param {module:engine/model/writer~Writer} writer
// @param {module:engine/model/selection~Selection|module:engine/model/documentselection~DocumentSelection} selection
// Selection on which the action should be performed.
// @param {module:engine/model/schema~Schema} schema
function enterBlock( model, writer, selection, schema ) {
    const isSelectionEmpty = selection.isCollapsed;
    const range = selection.getFirstRange();
    const startElement = range.start.parent;
    const endElement = range.end.parent;

    // Don't touch the roots and other limit elements.
    if ( schema.isLimit( startElement ) || schema.isLimit( endElement ) ) {
        // Delete the selected content but only if inside a single limit element.
        // Abort, when crossing limit elements boundary (e.g. <limit1>x[x</limit1>donttouchme<limit2>y]y</limit2>).
        // This is an edge case and it's hard to tell what should actually happen because such a selection
        // is not entirely valid.
        if ( !isSelectionEmpty && startElement == endElement ) {
            model.deleteContent( selection );
        }

        return;
    }

    if ( isSelectionEmpty ) {
        const attributesToCopy = getCopyOnEnterAttributes( writer.model.schema, selection.getAttributes() );
        splitBlock( writer, range.start );
        writer.setSelectionAttribute( attributesToCopy );
    } else {
        const leaveUnmerged = !( range.start.isAtStart && range.end.isAtEnd );
        const isContainedWithinOneElement = ( startElement == endElement );

        model.deleteContent( selection, { leaveUnmerged } );

        if ( leaveUnmerged ) {
            // Partially selected elements.
            //
            // <h>x[xx]x</h>        -> <h>x^x</h>            -> <h>x</h><h>^x</h>
            if ( isContainedWithinOneElement ) {
                splitBlock( writer, selection.focus );
            }
            // Selection over multiple elements.
            //
            // <h>x[x</h><p>y]y<p>    -> <h>x^</h><p>y</p>    -> <h>x</h><p>^y</p>
            else {
                writer.setSelection( endElement, 0 );
            }
        }
    }
}

function splitBlock( writer, splitPos ) {
    writer.split( splitPos );
    writer.setSelection( splitPos.parent.nextSibling, 0 );
}