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/dataprocessor/xmldataprocessor
 */

/* globals DOMParser, document */

import BasicHtmlWriter from './basichtmlwriter';
import DomConverter from '../view/domconverter';

/**
 * The XML data processor class.
 * This data processor implementation uses XML as input and output data.
 * This class is needed because unlike HTML, XML allows to use any tag with any value.
 * For example, `<link>Text</link>` is a valid XML but invalid HTML.
 *
 * @implements module:engine/dataprocessor/dataprocessor~DataProcessor
 */
export default class XmlDataProcessor {
    /**
     * Creates a new instance of the XML data processor class.
     *
     * @param {module:engine/view/document~Document} document The view document instance.
     * @param {Object} options Configuration options.
     * @param {Array<String>} [options.namespaces=[]] A list of namespaces allowed to use in the XML input.
     */
    constructor( document, options = {} ) {
        /**
         * A list of namespaces allowed to use in the XML input.
         *
         * For example, registering namespaces [ 'attribute', 'container' ] allows to use `<attirbute:tagName></attribute:tagName>`
         * and `<container:tagName></container:tagName>` input. It is mainly for debugging.
         *
         * @public
         * @member {DOMParser}
         */
        this.namespaces = options.namespaces || [];

        /**
         * DOM parser instance used to parse an XML string to an XML document.
         *
         * @private
         * @member {DOMParser}
         */
        this._domParser = new DOMParser();

        /**
         * DOM converter used to convert DOM elements to view elements.
         *
         * @private
         * @member {module:engine/view/domconverter~DomConverter}
         */
        this._domConverter = new DomConverter( document, { blockFillerMode: 'nbsp' } );

        /**
         * A basic HTML writer instance used to convert DOM elements to an XML string.
         * There is no need to use a dedicated XML writer because the basic HTML writer works well in this case.
         *
         * @private
         * @member {module:engine/dataprocessor/basichtmlwriter~BasicHtmlWriter}
         */
        this._htmlWriter = new BasicHtmlWriter();
    }

    /**
     * Converts the provided {@link module:engine/view/documentfragment~DocumentFragment document fragment}
     * to data format &mdash; in this case an XML string.
     *
     * @param {module:engine/view/documentfragment~DocumentFragment} viewFragment
     * @returns {String} An XML string.
     */
    toData( viewFragment ) {
        // Convert view DocumentFragment to DOM DocumentFragment.
        const domFragment = this._domConverter.viewToDom( viewFragment, document );

        // Convert DOM DocumentFragment to XML output.
        // There is no need to use dedicated for XML serializing method because BasicHtmlWriter works well in this case.
        return this._htmlWriter.getHtml( domFragment );
    }

    /**
     * Converts the provided XML string to a view tree.
     *
     * @param {String} data An XML string.
     * @returns {module:engine/view/node~Node|module:engine/view/documentfragment~DocumentFragment|null} A converted view element.
     */
    toView( data ) {
        // Convert input XML data to DOM DocumentFragment.
        const domFragment = this._toDom( data );

        // Convert DOM DocumentFragment to view DocumentFragment.
        return this._domConverter.domToView( domFragment, { keepOriginalCase: true } );
    }

    /**
     * Converts an XML string to its DOM representation. Returns a document fragment containing nodes parsed from
     * the provided data.
     *
     * @private
     * @param {String} data
     * @returns {DocumentFragment}
     */
    _toDom( data ) {
        // Stringify namespaces.
        const namespaces = this.namespaces.map( nsp => `xmlns:${ nsp }="nsp"` ).join( ' ' );

        // Wrap data into root element with optional namespace definitions.
        data = `<xml ${ namespaces }>${ data }</xml>`;

        const parsedDocument = this._domParser.parseFromString( data, 'text/xml' );

        // Parse validation.
        const parserError = parsedDocument.querySelector( 'parsererror' );

        if ( parserError ) {
            throw new Error( 'Parse error - ' + parserError.textContent );
        }

        const fragment = parsedDocument.createDocumentFragment();
        const nodes = parsedDocument.documentElement.childNodes;

        while ( nodes.length > 0 ) {
            fragment.appendChild( nodes[ 0 ] );
        }

        return fragment;
    }
}