ckeditor/ckeditor5-list

/**
 * @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 list/indentcommand
 */

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

/**
 * The list indent command. It is used by the {@link module:list/list~List list feature}.
 *
 * @extends module:core/command~Command
 */
export default class IndentCommand extends Command {
    /**
     * Creates an instance of the command.
     *
     * @param {module:core/editor/editor~Editor} editor The editor instance.
     * @param {'forward'|'backward'} indentDirection The direction of indent. If it is equal to `backward`, the command
     * will outdent a list item.
     */
    constructor( editor, indentDirection ) {
        super( editor );

        /**
         * Determines by how much the command will change the list item's indent attribute.
         *
         * @readonly
         * @private
         * @member {Number}
         */
        this._indentBy = indentDirection == 'forward' ? 1 : -1;
    }

    /**
     * @inheritDoc
     */
    refresh() {
        this.isEnabled = this._checkEnabled();
    }

    /**
     * Indents or outdents (depending on the {@link #constructor}'s `indentDirection` parameter) selected list items.
     *
     * @fires execute
     */
    execute() {
        const model = this.editor.model;
        const doc = model.document;
        let itemsToChange = Array.from( doc.selection.getSelectedBlocks() );

        model.change( writer => {
            const lastItem = itemsToChange[ itemsToChange.length - 1 ];

            // Indenting a list item should also indent all the items that are already sub-items of indented item.
            let next = lastItem.nextSibling;

            // Check all items after last indented item, as long as their indent is bigger than indent of that item.
            while ( next && next.name == 'listItem' && next.getAttribute( 'listIndent' ) > lastItem.getAttribute( 'listIndent' ) ) {
                itemsToChange.push( next );

                next = next.nextSibling;
            }

            // We need to be sure to keep model in correct state after each small change, because converters
            // bases on that state and assumes that model is correct.
            // Because of that, if the command outdents items, we will outdent them starting from the last item, as
            // it is safer.
            if ( this._indentBy < 0 ) {
                itemsToChange = itemsToChange.reverse();
            }

            for ( const item of itemsToChange ) {
                const indent = item.getAttribute( 'listIndent' ) + this._indentBy;

                // If indent is lower than 0, it means that the item got outdented when it was not indented.
                // This means that we need to convert that list item to paragraph.
                if ( indent < 0 ) {
                    // To keep the model as correct as possible, first rename listItem, then remove attributes,
                    // as listItem without attributes is very incorrect and will cause problems in converters.
                    // No need to remove attributes, will be removed by post fixer.
                    writer.rename( item, 'paragraph' );
                }
                // If indent is >= 0, change the attribute value.
                else {
                    writer.setAttribute( 'listIndent', indent, item );
                }
            }
        } );
    }

    /**
     * Checks whether the command can be enabled in the current context.
     *
     * @private
     * @returns {Boolean} Whether the command should be enabled.
     */
    _checkEnabled() {
        // Check whether any of position's ancestor is a list item.
        const listItem = first( this.editor.model.document.selection.getSelectedBlocks() );

        // If selection is not in a list item, the command is disabled.
        if ( !listItem || !listItem.is( 'listItem' ) ) {
            return false;
        }

        if ( this._indentBy > 0 ) {
            // Cannot indent first item in it's list. Check if before `listItem` is a list item that is in same list.
            // To be in the same list, the item has to have same attributes and cannot be "split" by an item with lower indent.
            const indent = listItem.getAttribute( 'listIndent' );
            const type = listItem.getAttribute( 'listType' );

            let prev = listItem.previousSibling;

            while ( prev && prev.is( 'listItem' ) && prev.getAttribute( 'listIndent' ) >= indent ) {
                if ( prev.getAttribute( 'listIndent' ) == indent ) {
                    // The item is on the same level.
                    // If it has same type, it means that we found a preceding sibling from the same list.
                    // If it does not have same type, it means that `listItem` is on different list (this can happen only
                    // on top level lists, though).
                    return prev.getAttribute( 'listType' ) == type;
                }

                prev = prev.previousSibling;
            }

            // Could not find similar list item, this means that `listItem` is first in its list.
            return false;
        }

        // If we are outdenting it is enough to be in list item. Every list item can always be outdented.
        return true;
    }
}