( function ( $, mw ) {

	var relatedPages = new mw.relatedPages.RelatedPagesGateway(
			new mw.Api(),
			mw.config.get( 'wgPageName' ),
			mw.config.get( 'wgRelatedArticles' ),
			mw.config.get( 'wgRelatedArticlesUseCirrusSearch' ),
			mw.config.get( 'wgRelatedArticlesOnlyUseCirrusSearch' )
		),
		LIMIT = 3,
		debouncedLoad = $.debounce( 100, function () {
			loadRelatedArticles();
		} ),
		$window = $( window );

	/**
	 * Load related articles when the user scrolls past half of the window height.
	 *
	 * @ignore
	 */
	function loadRelatedArticles() {
		var readMore = $( '.read-more-container' ).get( 0 ),
			scrollThreshold = $window.height() * 2;

		if ( mw.viewport.isElementCloseToViewport( readMore, scrollThreshold ) ) {
			$.when(
				// Note we load dependencies here rather than ResourceLoader
				// to avoid PHP exceptions when Cards not installed
				// which should never happen given the if statement.
				mw.loader.using( [ 'ext.cards', 'ext.relatedArticles.readMore' ] ),
				relatedPages.getForCurrentPage( LIMIT )
			).done( function ( _, pages ) {
				if ( pages.length ) {
					mw.track( 'ext.relatedArticles.init', pages );
				} else {
					readMore.remove();
				}
			} );
			// detach handler to stop subsequent loads on scroll
			$window.off( 'scroll', debouncedLoad );
		}
	}

	// Add container to DOM for checking distance on scroll
	// If a skin has marked up a footer content area prepend it there
	if ( $( '.footer-content' ).length ) {
		$( '<div class="read-more-container" />' ).prependTo( '.footer-content' );
	} else {
		$( '<div class="read-more-container post-content" />' )
			.insertAfter( '#content' );
	}

	// try related articles load on scroll
	$window.on( 'scroll', debouncedLoad );
	// try an initial load, in case of no scroll
	loadRelatedArticles();

}( jQuery, mediaWiki ) );