/**
 * @module ol/format/XML
 */
import {isDocument, parse} from './util/xml.js';

/**
 * @classdesc
 * Generic format for reading non-feature XML data
 *
 * @abstract
 */
class XML {
 /**
 * Read the source document.
 *
 * @param {Document|Element|string} source The XML source.
 * @return {Object} An object representing the source.
 * @api
 */
 read(source) {
 if (!source) {
 return null;
 } else if (typeof source === 'string') {
 const doc = parse(source);
 return this.readFromDocument(doc);
 } else if (isDocument(source)) {
 return this.readFromDocument(/** @type {Document} */ (source));
 } else {
 return this.readFromNode(/** @type {Element} */ (source));
 }
 }

 /**
 * @param {Document} doc Document.
 * @return {Object} Object
 */
 readFromDocument(doc) {
 for (let n = doc.firstChild; n; n = n.nextSibling) {
 if (n.nodeType == Node.ELEMENT_NODE) {
 return this.readFromNode(/** @type {Element} */ (n));
 }
 }
 return null;
 }

 /**
 * @abstract
 * @param {Element} node Node.
 * @return {Object} Object
 */
 readFromNode(node) {}
}

export default XML;