/*!
 * VisualEditor MediaWiki ArticleTargetLoader.
 *
 * @copyright 2011-2017 VisualEditor Team and others; see AUTHORS.txt
 * @license The MIT License (MIT); see LICENSE.txt
 */

/**
 * Target loader.
 *
 * Light-weight loader that loads ResourceLoader modules for VisualEditor
 * and HTML and page data from the API. Also handles plugin registration.
 *
 * @class mw.libs.ve.targetLoader
 * @singleton
 */
( function () {
	var prefName, prefValue,
		uri = new mw.Uri(),
		conf = mw.config.get( 'wgVisualEditorConfig' ),
		pluginCallbacks = [],
		modules = [ 'ext.visualEditor.articleTarget' ]
			// Add modules from $wgVisualEditorPluginModules
			.concat( conf.pluginModules.filter( mw.loader.getState ) );

	// Provide the new wikitext editor
	if (
		conf.enableWikitext &&
		(
			mw.user.options.get( 'visualeditor-newwikitext' ) ||
			uri.query.veaction === 'editsource'
		) &&
		mw.loader.getState( 'ext.visualEditor.mwwikitext' )
	) {
		modules.push( 'ext.visualEditor.mwwikitext' );
	}

	// Allow signing posts in select namespaces
	if ( conf.signatureNamespaces.length ) {
		modules.push( 'ext.visualEditor.mwsignature' );
	}

	// Add preference modules
	for ( prefName in conf.preferenceModules ) {
		prefValue = mw.user.options.get( prefName );
		// Check "0" (T89513)
		if ( prefValue && prefValue !== '0' ) {
			modules.push( conf.preferenceModules[ prefName ] );
		}
	}

	mw.libs.ve = mw.libs.ve || {};

	mw.libs.ve.targetLoader = {
		/**
		 * Add a plugin module or callback.
		 *
		 * If a module name is passed, that module will be loaded alongside the other modules.
		 *
		 * If a callback is passed, it will be executed after the modules have loaded. The callback
		 * may optionally return a jQuery.Promise; if it does, loading won't be complete until
		 * that promise is resolved.
		 *
		 * @param {string|Function} plugin Plugin module name or callback
		 */
		addPlugin: function ( plugin ) {
			if ( typeof plugin === 'string' ) {
				modules.push( plugin );
			} else if ( $.isFunction( plugin ) ) {
				pluginCallbacks.push( plugin );
			}
		},

		/**
		 * Load modules needed for VisualEditor, as well as plugins.
		 *
		 * This loads the base VE modules as well as any registered plugin modules.
		 * Once those are loaded, any registered plugin callbacks are executed,
		 * and we wait for all promises returned by those callbacks to resolve.
		 *
		 * @return {jQuery.Promise} Promise resolved when the loading process is complete
		 */
		loadModules: function () {
			ve.track( 'trace.moduleLoad.enter' );
			return mw.loader.using( modules )
				.then( function () {
					ve.track( 'trace.moduleLoad.exit' );
					pluginCallbacks.push( ve.init.platform.getInitializedPromise.bind( ve.init.platform ) );
					// Execute plugin callbacks and collect promises
					return $.when.apply( $, pluginCallbacks.map( function ( callback ) {
						return callback();
					} ) );
				} );
		},

		/**
		 * Request the page data and various metadata from the MediaWiki API (which will use
		 * Parsoid or RESTBase).
		 *
		 * @param {string} mode Target mode: 'visual' or 'source'
		 * @param {string} pageName Page name to request
		 * @param {Object} [options] Options
		 * @param {number|string} [options.section] Section to edit, number or 'new' (currently just source mode)
		 * @param {number} [options.oldId] Old revision ID. Current if omitted.
		 * @param {string} [options.targetName] Optional target name for tracking
		 * @param {boolean} [options.modified] The page was been modified before loading (e.g. in source mode)
		 * @param {string} [options.wikitext] Wikitext to convert to HTML. The original document is fetched if undefined.
		 * @param {string} [preload] Name of a page to use as preloaded content if pageName is empty
		 * @param {Array} [preloadparams] Parameters to substitute into preload if it's used
		 * @return {jQuery.Promise} Abortable promise resolved with a JSON object
		 */
		requestPageData: function ( mode, pageName, options ) {
			if ( mode === 'source' ) {
				return this.requestWikitext( pageName, options );
			} else {
				return this.requestParsoidData( pageName, options );
			}
		},

		/**
		 * Request the page HTML and various metadata from the MediaWiki API (which will use
		 * Parsoid or RESTBase).
		 *
		 * @param {string} pageName See #requestPageData
		 * @param {Object} [options] See #requestPageData
		 * @return {jQuery.Promise} Abortable promise resolved with a JSON object
		 */
		requestParsoidData: function ( pageName, options ) {
			var start, apiXhr, restbaseXhr, apiPromise, restbasePromise, dataPromise, pageHtmlUrl, headers,
				switched = false,
				fromEditedState = false,
				data = {
					action: 'visualeditor',
					paction: ( conf.fullRestbaseUrl || conf.restbaseUrl ) ? 'metadata' : 'parse',
					page: pageName,
					uselang: mw.config.get( 'wgUserLanguage' ),
					editintro: uri.query.editintro,
					preload: options.preload,
					preloadparams: options.preloadparams
				};

			options = options || {};

			// Only request the API to explicitly load the currently visible revision if we're restoring
			// from oldid. Otherwise we should load the latest version. This prevents us from editing an
			// old version if an edit was made while the user was viewing the page and/or the user is
			// seeing (slightly) stale cache.
			if ( options.oldId !== undefined ) {
				data.oldid = options.oldId;
			}
			// Load DOM
			start = ve.now();
			ve.track( 'trace.apiLoad.enter' );

			apiXhr = new mw.Api().get( data );
			apiPromise = apiXhr.then( function ( data, jqxhr ) {
				ve.track( 'trace.apiLoad.exit' );
				ve.track( 'mwtiming.performance.system.apiLoad', {
					bytes: $.byteLength( jqxhr.responseText ),
					duration: ve.now() - start,
					cacheHit: /hit/i.test( jqxhr.getResponseHeader( 'X-Cache' ) ),
					targetName: options.targetName
				} );
				return data;
			} );

			if ( conf.fullRestbaseUrl || conf.restbaseUrl ) {
				ve.track( 'trace.restbaseLoad.enter' );

				// Should be synchronised with ApiVisualEditor.php
				headers = {
					Accept: 'text/html; charset=utf-8; profile="mediawiki.org/specs/html/1.2.0"',
					'Api-User-Agent': 'VisualEditor-MediaWiki/' + mw.config.get( 'wgVersion' )
				};

				// Convert specified Wikitext to HTML
				if (
					// wikitext can be an empty string
					options.wikitext !== undefined &&
					!$( '[name=wpSection]' ).val()
				) {
					if ( conf.fullRestbaseUrl ) {
						pageHtmlUrl = conf.fullRestbaseUrl + 'v1/transform/wikitext/to/html/';
					} else {
						pageHtmlUrl = conf.restbaseUrl.replace( 'v1/page/html/', 'v1/transform/wikitext/to/html/' );
					}
					switched = true;
					fromEditedState = options.modified;
					window.onbeforeunload = null;
					$( window ).off( 'beforeunload' );
					restbaseXhr = $.ajax( {
						url: pageHtmlUrl + encodeURIComponent( pageName ) +
							( data.oldid === undefined ? '' : '/' + data.oldid ),
						type: 'POST',
						data: {
							title: pageName,
							oldid: data.oldid,
							wikitext: options.wikitext,
							stash: 'true'
						},
						headers: headers,
						dataType: 'text'
					} );
				} else {
					// Fetch revision
					if ( conf.fullRestbaseUrl ) {
						pageHtmlUrl = conf.fullRestbaseUrl + 'v1/page/html/';
					} else {
						pageHtmlUrl = conf.restbaseUrl;
					}
					restbaseXhr = $.ajax( {
						url: pageHtmlUrl + encodeURIComponent( pageName ) +
							( data.oldid === undefined ? '' : '/' + data.oldid ) + '?redirect=false',
						type: 'GET',
						headers: headers,
						dataType: 'text'
					} );
				}
				restbasePromise = restbaseXhr.then(
					function ( data, status, jqxhr ) {
						ve.track( 'trace.restbaseLoad.exit' );
						ve.track( 'mwtiming.performance.system.restbaseLoad', {
							bytes: $.byteLength( jqxhr.responseText ),
							duration: ve.now() - start,
							targetName: options.targetName
						} );
						return [ data, jqxhr.getResponseHeader( 'etag' ) ];
					},
					function ( xhr, code, _ ) {
						if ( xhr.status === 404 ) {
							// Page does not exist, so let the user start with a blank document.
							return $.Deferred().resolve( [ '', undefined ] ).promise();
						} else {
							mw.log.warn( 'RESTBase load failed: ' + xhr.statusText );
							return $.Deferred().reject( code, xhr, _ ).promise();
						}
					}
				);

				dataPromise = $.when( apiPromise, restbasePromise )
					.then( function ( apiData, restbaseData ) {
						if ( apiData.visualeditor ) {
							if ( restbaseData[ 0 ] || !apiData.visualeditor.content ) {
								// If we have actual content loaded, use it.
								// Otherwise, allow fallback content if present.
								// If no fallback content, this will give us an empty string for
								// content, which is desirable.
								apiData.visualeditor.content = restbaseData[ 0 ];
								apiData.visualeditor.etag = restbaseData[ 1 ];
							}
							apiData.visualeditor.switched = switched;
							apiData.visualeditor.fromEditedState = fromEditedState;
						}
						return apiData;
					} )
					.promise( { abort: function () {
						apiXhr.abort();
						restbaseXhr.abort();
					} } );
			} else {
				dataPromise = apiPromise.promise( { abort: apiXhr.abort } );
			}

			return dataPromise;
		},

		/**
		 * Request the page wikitext and various metadata from the MediaWiki API.
		 *
		 * @param {string} pageName See #requestPageData
		 * @param {Object} [options] See #requestPageData
		 * @return {jQuery.Promise} Abortable promise resolved with a JSON object
		 */
		requestWikitext: function ( pageName, options ) {
			var data = {
				action: 'visualeditor',
				paction: 'wikitext',
				page: pageName,
				uselang: mw.config.get( 'wgUserLanguage' ),
				editintro: uri.query.editintro,
				preload: options.preload,
				preloadparams: options.preloadparams
			};

			// section should never really be undefined, but check just in case
			if ( options.section !== null && options.section !== undefined ) {
				data.section = options.section;
			}

			if ( options.oldId !== undefined ) {
				data.oldid = options.oldId;
			}

			return new mw.Api().get( data );
		}
	};
}() );