var SKIN_MINERVA_TALK_SIMPLIFIED_CLASS = 'skin-minerva--talk-simplified';

/**
 * @return {boolean}
 */
function isSimplifiedViewEnabled() {
	// eslint-disable-next-line no-jquery/no-class-state
	return $( document.body ).hasClass( SKIN_MINERVA_TALK_SIMPLIFIED_CLASS );
}

/**
 * @param {Object} mobile mobileFrontend component library
 */
function init( mobile ) {
	var
		toast = mobile.toast,
		currentPage = mobile.currentPage(),
		api = new mw.Api(),
		overlayManager = mobile.OverlayManager.getSingleton(),
		// FIXME: This dependency shouldn't exist
		skin = mobile.Skin.getSingleton(),
		talkTitle = currentPage.titleObj.getTalkPage() ?
			currentPage.titleObj.getTalkPage().getPrefixedText() :
			undefined;

	/**
	 * Render a type of talk overlay
	 *
	 * @param {string} className name of talk overlay to create
	 * @param {Object} talkOptions
	 * @return {Overlay|jQuery.Promise}
	 */
	function createOverlay( className, talkOptions ) {
		// eslint-disable-next-line no-restricted-properties
		var M = mw.mobileFrontend;

		return new ( M.require( 'mobile.talk.overlays/' + className ) )( talkOptions );
	}

	/**
	 * Cleanup the listeners previously added in initTalkSection
	 * so that events like clicking on a section) won't cause
	 * scroll changes/things only needed for the simplified view.
	 * Also restore ids for table of contents.
	 */
	function restoreSectionHeadings() {
		// eslint-disable-next-line no-jquery/no-global-selector
		$( '.section-heading' ).each( function () {
			var $heading = $( this ),
				$headline = $heading.find( '.mw-headline' );
			$heading.off( 'click.talkSectionOverlay' );
			// restore for table of contents:
			$headline.attr( 'id', $headline.data( 'id' ) );
		} );
	}

	/**
	 * @param {jQuery.Element} $heading
	 * @param {jQuery.Element} $headline
	 * @param {string} sectionId
	 * @return {jQuery.Promise} A promise that rejects if simplified mode is off.
	 * A promise that resolves to the TalkSectionOverlay otherwise (unless a
	 * network error occurs).
	 */
	function createTalkSectionOverlay( $heading, $headline, sectionId ) {
		if ( !isSimplifiedViewEnabled() ) {
			// If the simplified view is not enabled, we don't want to show the
			// talk section overlay (e.g. when user clicks on a link in TOC)
			return mobile.util.Deferred().reject();
		}

		return createOverlay( 'TalkSectionOverlay', {
			id: sectionId,
			section: new mobile.Section( {
				// Strip out any HTML from the headline to avoid links in T243650.
				line: $( '<span>' ).text( $( $headline ).text() )[ 0 ].outerHTML,
				text: $heading.next().html()
			} ),
			// FIXME: Replace this api param with onSaveComplete
			api: api,
			title: talkTitle,
			// T184273 using `currentPage` because 'wgPageName'
			// contains underscores instead of spaces.
			licenseMsg: skin.getLicenseMsg(),
			onSaveComplete: function () {
				toast.showOnPageReload( mw.msg( 'minerva-talk-reply-success' ) );
				window.location.reload();
			}
		} );
	}

	/**
	 * Initializes code needed to display the TalkSectionOverlay
	 */
	function initTalkSection() {
		// register route for each of the sub-headings
		// eslint-disable-next-line no-jquery/no-global-selector
		$( '.section-heading' ).each( function () {
			var
				sectionId,
				$heading = $( this ),
				$headline = $heading.find( '.mw-headline' ),
				$editLink = $heading.find( '.mw-editsection a' ),
				headlineId = $headline.attr( 'id' ),
				// T238364: Before registering a route with OverlayManager, we need to
				// encode the id first to ensure it forms a valid URI in case the id
				// contains illegal URI characters as defined by RFC3986. This avoids
				// inconsistencies with how different browsers encode illegal URI
				// characters.
				encodedHeadlineId = encodeURIComponent( headlineId );

			if ( !$editLink.length ) {
				// If section id couldn't be parsed, there is no point in continuing
				return;
			}
			sectionId = mw.util.getParamValue( 'section', $editLink[ 0 ].href );

			$heading.on( 'click.talkSectionOverlay', function ( ev ) {
				ev.preventDefault();
				window.location.hash = '#' + encodedHeadlineId;

			} ).attr( 'data-event-name', 'talkpage.section' );

			// remove the `id` to avoid conflicts with the overlay route.
			// Without JS the id will still be present. With JS the overlay will open.
			$headline.removeAttr( 'id' );
			// however cache it to data for cooperation with the 'read as wiki page' button.
			$headline.data( 'id', headlineId );
			$headline.attr( 'data-event-name', 'talkpage.section' );

			overlayManager.add( encodedHeadlineId, function () {
				return createTalkSectionOverlay( $heading, $headline, sectionId );
			} );
		} );
	}

	/**
	 * Initializes code needed to display the TalkSectionAddOverlay
	 */
	function initTalkSectionAdd() {
		overlayManager.add( /^\/talk\/new$/, function () {
			return createOverlay( 'TalkSectionAddOverlay', {
				api: api,
				title: talkTitle,
				// T184273 using `currentPage` because 'wgPageName'
				// contains underscores instead of spaces.
				licenseMsg: skin.getLicenseMsg(),

				currentPageTitle: currentPage.title,
				onSaveComplete: function () {
					toast.showOnPageReload( mw.msg( 'minerva-talk-topic-feedback' ) );
					window.location = currentPage.titleObj.getTalkPage().getUrl();
				}
			} );
		} );
	}

	/**
	 * T230695: In the simplified view, we need to display a "Read as wikipage"
	 * button which enables the user to switch from simplified mode to the regular
	 * version of the mobile talk page (with TOC and sections that you can
	 * expand/collapse).
	 */
	function renderReadAsWikiPageButton() {
		$( '<button>' )
			.addClass( 'minerva-talk-full-page-button' )
			.attr( 'data-event-name', 'talkpage.readAsWiki' )
			.text( mw.msg( 'minerva-talk-full-page' ) )
			.on( 'click', function () {
				restoreSectionHeadings();
				$( document.body ).removeClass( 'skin-minerva--talk-simplified' );
				$( this ).remove();
				// send user back up to top of page so they don't land awkwardly in
				// middle of page when it expands
				window.scrollTo( 0, 0 );
			} )
			.appendTo( '#content' );
	}

	/**
	 * Sets up necessary event handlers related to the talk page and talk buttons.
	 * Also renders the "Read as wikipage" button for the simplified mode
	 * (T230695).
	 */
	function doInit() {
		var promise,
			// eslint-disable-next-line no-jquery/no-global-selector
			$addTalk = $( '.minerva-talk-add-button' );

		$addTalk.on( 'click', function ( ev ) {
			// avoid navigating to original URL in anchor element
			ev.preventDefault();
			window.location.hash = '#/talk/new';
		} );

		// We only want the talk section add overlay to show when the user is on the
		// view action (default action) of the talk page and not when the user is on
		// other actions of the talk page (e.g. like the history action)
		if ( currentPage.titleObj.isTalkPage() && mw.config.get( 'wgAction' ) === 'view' ) {
			promise = mw.loader.using( 'mobile.talk.overlays' )
				.then( initTalkSectionAdd );
		} else {
			return;
		}

		// SkinMinerva sets a class on the body which effectively controls when this
		// mode is on
		if ( isSimplifiedViewEnabled() ) {
			promise.then( initTalkSection )
				.then( renderReadAsWikiPageButton );
		}
	}

	if ( talkTitle ) {
		doInit();
	}
}

module.exports = {
	init: init,
	isSimplifiedViewEnabled: isSimplifiedViewEnabled
};