/*                            DiffOnly

 * 

 * This gadget adds a "diff only" link next to the "Next edit" and "Previous

 * edit" links on diff pages. Clicking on the "diff only" link will show you

 * the diff with no page content. These links usually load a lot faster

 * than normal diff links, which can be handy for looking through lots of diffs.

 * 

 * To install it, add the following to your [[Special:MyPage/common.js]]:



importScript('User:Mr. Stradivarius/gadgets/DiffOnly.js') // Linkback: [[User:Mr. Stradivarius/gadgets/DiffOnly.js]]



 * Note that you can choose to never show the page content when viewing diffs

 * by going to Preferences → Appearance → Diffs, and by selecting the "Do not

 * show page content below diffs" checkbox. This should be preferred over using

 * this gadget if you do not want the option to choose between diffs with and

 * without page content.

 *

 * This script is based on code by HighInBC at

 * https://en.wikipedia.org/?title=User:HighInBC/common.js&oldid=682081230

 */



mw.loader.using( 'mediawiki.Uri'], function () {

	var DOT_SEPARATOR = '&nbsp;<b>·</b> ';

	var mwConfig = mw.config.get( 

		'wgAction',

		'wgCanonicalSpecialPageName'

	 );



	// Load user config

	var config = window.DiffOnly;

	if ( config === 'all' ) {

		config = { all: true };

	} else if ( typeof config !== 'object' ) {

		config = {};

	}

	if ( config.diff === undefined ) {

		// Turn diff page links on by default

		config.diff = true;

	}

	if ( config.all !== undefined ) {

		config.diff = config.all;

		config.history = config.all;

		config.recentchanges = config.all;

		config.watchlist = config.all;

	}



	/**************************************************************************\

	* Helper functions

	\**************************************************************************/



	// Make a diff-only link, based on the normal diff link $diffLink.

	// $diffLink should be a jQuery object consisting of exactly one <a>

	// element.

	function makeDiffOnlyLink( $diffLink, display ) {

		var diffUri, $diffOnlyLink;



		if ( $diffLink.length !== 1 ) {

			throw Error( 'makeDiffOnlyLink must be passed a jQuery object of length 1' );

		}

		if ( !$diffLink.attr( 'href' ) ) {

			return;

		}



		// Make the new diff-only URL

		diffUri = new mw.Uri( $diffLink.attr( 'href' ) );

		diffUri.extend( { diffonly: 1 } );



		// Make the diff-only link

		$diffOnlyLink = $( '<a>' )

			.attr( 'href', diffUri.toString() )

			.text( display );

		if ( $diffLink.attr( 'title' ) )  {

			$diffOnlyLink.attr( 'title', $diffLink.attr( 'title' ) );

		}



		return $diffOnlyLink;

	}



	/**************************************************************************\

	* Add diff-only links to diff pages

	\**************************************************************************/



	// Handle a "Next edit" or "Previous edit" link on a diff page. 

	function handleDiffPageLink( options ) {

		var $diffOnlyLink, diffUri,

			$diffLink = $( options.selector );



		if ( $diffLink.length !== 1 ) {

			return;

		}



		$diffOnlyLink = makeDiffOnlyLink( $diffLink, 'diff only' );



		// Add the diff-only link and the arrow.

		$diffLink.parent()

			.append( DOT_SEPARATOR )

			.append( $diffOnlyLink )

			 options.jqueryMethod ]( ' ' )

			 options.jqueryMethod ]( options.arrow );



		// The standard diff links on diff pages have the arrow inside the <a>

		// element. However, we don't want that, as it looks wrong when we

		// introduce the other link. To fix it, we set the text again.

		//

		// Also, if we navigated to this diff page from a diff-only link, then

		// the standard diff link will have a diffonly parameter. We don't want

		// to have two diff-only links, so we delete the diffonly parameter

		// in the original diff link.

		diffUri = new mw.Uri( $diffLink.attr( 'href' ) );

		delete diffUri.query.diffonly;

		$diffLink

			.attr( 'href', diffUri.toString() )

			.text( options.diffLinkDisplay );

	}



	if ( config.diff ) {

		handleDiffPageLink( {

			selector: '#differences-prevlink',

			jqueryMethod: 'prepend',

			diffLinkDisplay: 'Previous edit',

			arrow: '←'

		} );

		handleDiffPageLink( {

			selector: '#differences-nextlink',

			jqueryMethod: 'append',

			diffLinkDisplay: 'Next edit',

			arrow: '→'

		} );

	}



	/**************************************************************************\

	* Add diff-only links to lists of changes

	\**************************************************************************/



	// Handle a page with multiple diffs on, like Special:RecentChanges,

	// Special:Watchlist, or history pages.

	// The selector should select all the diff links on the page.

	function handleChangeList( selector ) {

		$( selector ).each( function () {

			// Make the diff-only link

			var $diffLink = $( this );

			var $diffOnlyLink = makeDiffOnlyLink( $diffLink, 'only' );

			

			// Insert the diff only link after the diff link, and then separate

			// them with the dot-separator.

			$diffLink.after( $diffOnlyLink );

			$diffLink.after( DOT_SEPARATOR );

		} );

	}



	// Handle history diff links

	if ( config.history && mwConfig.wgAction == "history" ) {

		handleChangeList( '.mw-history-histlinks>a' );

	}



	// Handle recent changes and watchlist diff links

	if ( config.recentchanges && mwConfig.wgCanonicalSpecialPageName == "Recentchanges"

			|| config.watchlist && mwConfig.wgCanonicalSpecialPageName == 'Watchlist' )

	{

		handleChangeList( '.mw-changeslist-diff' );

	}

} );