User:Mr. Stradivarius/gadgets/DiffOnly.js

/*                            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/w/index.php?title=User:HighInBC/common.js&oldid=682081230
 */

$( document ).ready( function() {
	var DOT_SEPARATOR = '&nbsp;<b>·</b> ';
	var BASE_URL = (new URL( window.location ) ).origin;
	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;
		config.contributions = 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 = URL.parse( $diffLink.attr( 'href' ), BASE_URL );
		if ( !diffUri.searchParams.has( 'diffonly' ) ) {
			diffUri.searchParams.append( '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 = URL.parse( $diffLink.attr( 'href' ), BASE_URL );
		diffUri.searchParams.delete( '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'
			|| config.contributions && mwConfig.wgCanonicalSpecialPageName == 'Contributions')
	{
		handleChangeList( '.mw-changeslist-diff' );
	}
} );