/**
	 * Create a link element that opens the issues overlay.
	 *
	 * @ignore
	 *
	 * @param {string} labelText The text value of the element
	 * @return {JQuery}
	 */
	function createLinkElement( labelText ) {
		return $( '<a class="cleanup mw-mf-cleanup"></a>' )
			.text( labelText );
	}

	/**
	 * Creates a "read more" button with given text.
	 * @param {string} msg
	 * @return {JQuery}
	 */
	function createLearnMoreLink( msg ) {
		return $( '<span>' )
			.addClass( 'ambox-learn-more' )
			.text( msg );
	}

	/**
	 * Modifies the `issue` DOM to create a banner designed for
	 * single issue templates, and handles event-binding for that issues overlay.
	 *
	 * @param {IssueSummary} issue
	 * @param {string} msg
	 * @param {string} overlayUrl
	 * @param {Object} overlayManager
	 */
	function createPageIssueBanner( issue, msg, overlayUrl, overlayManager ) {
		var $learnMoreEl = createLearnMoreLink( msg ),
			$issueContainer = issue.$el.find( '.mbox-text' );

		$issueContainer.prepend( issue.iconString );
		$issueContainer.prepend( $learnMoreEl );

		issue.$el.click( function () {
			overlayManager.router.navigate( overlayUrl );
			return false;
		} );
	}

	/**
	 * Modifies the `issue` DOM to create a banner designed for
	 * multiple issue templates, and handles event-binding for that issues overlay.
	 *
	 * @param {IssueSummary} issue
	 * @param {string} msg
	 * @param {string} overlayUrl
	 * @param {Object} overlayManager
	 */
	function createPageIssueBannerMultiple( issue, msg, overlayUrl, overlayManager ) {
		var $learnMoreEl = createLearnMoreLink( msg ),
			$parentContentContainer = issue.$el.parents( '.mbox-text-span, .mbox-text-div' ),
			$parentContainer = issue.$el.parents( '.mbox-text' );

		$parentContentContainer.prepend( issue.iconString );
		$parentContentContainer.prepend( $learnMoreEl );

		$parentContainer.click( function () {
			overlayManager.router.navigate( overlayUrl );
			return false;
		} );
	}

	/**
	 * Modifies the page DOM to insert a page-issue notice below the title of the page,
	 * containing a link with a message like "this page has issues".
	 * Used on talk & category namespaces, or when page-issue banners have been disabled.s
	 *
	 * @param {string} labelText
	 * @param {string} section
	 */
	function createPageIssueNotice( labelText, section ) {
		var $link = createLinkElement( labelText );
		$link.attr( 'href', '#/issues/' + section );
		$link.insertAfter( $( 'h1#section_0' ) );
	}

	/**
	 * Render a banner in a containing element.
	 * if in group B, a learn more link will be append to any amboxes inside $container
	 * if in group A or control, any amboxes in container will be removed and a link "page issues"
	 * will be rendered above the heading.
	 * This function comes with side effects. It will populate a global "allIssues" object which
	 * will link section numbers to issues.
	 * @param {Page} page to search for page issues inside
	 * @param {string} labelText what the label of the page issues banner should say
	 * @param {string} section that the banner and its issues belong to.
	 *  If string KEYWORD_ALL_SECTIONS banner should apply to entire page.
	 * @param {boolean} inline - if true the first ambox in the section will become the entry point
	 *                           for the issues overlay
	 *  and if false, a link will be rendered under the heading.
	 * @param {OverlayManager} overlayManager
	 * @ignore
	 *
	 * @return {JQuery.Object}
	 */
	function createBanner( page, labelText, section, inline, overlayManager ) {
		var
			$metadata,
			issueUrl = section === KEYWORD_ALL_SECTIONS ? '#/issues/' + KEYWORD_ALL_SECTIONS : '#/issues/' + section,
			selector = 'table.ambox, table.tmbox, table.cmbox, table.fmbox',
			issueSummaries = [];

		if ( section === KEYWORD_ALL_SECTIONS ) {
			$metadata = page.$( selector );
		} else {
			// find heading associated with the section
			$metadata = page.findChildInSectionLead( parseInt( section, 10 ), selector );
		}
		// clean it up a little
		$metadata.find( '.NavFrame' ).remove();
		$metadata.each( function () {
			var issueSummary,
				$this = $( this );

			if ( $this.find( selector ).length === 0 ) {
				issueSummary = pageIssuesParser.extract( $this );
				// Some issues after "extract" has been run will have no text.
				// For example in Template:Talk header the table will be removed and no issue found.
				// These should not be rendered.
				if ( issueSummary.text ) {
					issueSummaries.push( issueSummary );
				}
			}
		} );
		// store it for later
		allIssues[section] = issueSummaries;

		if ( inline ) {
			issueSummaries.forEach( function ( issueSummary, i ) {
				var isGrouped = issueSummary.issue.grouped,
					lastIssueIsGrouped = issueSummaries[ i - 1] &&
						issueSummaries[ i - 1].issue.grouped;
				// only render the first grouped issue of each group
				if ( isGrouped && !lastIssueIsGrouped ) {
					createPageIssueBannerMultiple( issueSummary, mw.msg( 'skin-minerva-issue-learn-more' ), issueUrl, overlayManager );
				} else {
					createPageIssueBanner( issueSummary, mw.msg( 'skin-minerva-issue-learn-more' ), issueUrl, overlayManager );
				}
			} );
		} else if ( issueSummaries.length ) {
			createPageIssueNotice( labelText, section );
		}

		return $metadata;
	}

	/**
	 * Obtains the list of issues for the current page and provided section
	 * @param {number|string} section either KEYWORD_ALL_SECTIONS or a number relating to the
	 *                                section the issues belong to
	 * @return {jQuery.Object[]} array of all issues.
	 */
	function getIssues( section ) {
		if ( section !== KEYWORD_ALL_SECTIONS ) {
			return allIssues[section] || [];
		}
		// Note section.all may not exist, depending on the structure of the HTML page.
		// It will only exist when Minerva has been run in desktop mode.
		// If it's absent, we'll reduce all the other lists into one.
		return allIssues.all || Object.keys( allIssues ).reduce(
			function ( all, key ) {
				return all.concat( allIssues[key] );
			},
			[]
		);
	}