<?php
/**
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @file
 */

namespace MediaWiki\Minerva\Skins;

use ExtensionRegistry;
use Html;
use Language;
use MediaWiki\Linker\LinkTarget;
use MediaWiki\MediaWikiServices;
use MediaWiki\Minerva\Menu\Main\MainMenuDirector;
use MediaWiki\Minerva\Menu\PageActions\PageActionsDirector;
use MediaWiki\Minerva\Menu\User\UserMenuDirector;
use MediaWiki\Minerva\MinervaUI;
use MediaWiki\Minerva\Permissions\IMinervaPagePermissions;
use MediaWiki\Minerva\SkinOptions;
use MWException;
use MWTimestamp;
use ParserOptions;
use ParserOutput;
use RuntimeException;
use SkinMustache;
use SkinTemplate;
use SpecialMobileHistory;
use SpecialPage;
use Title;

/**
 * Minerva: Born from the godhead of Jupiter with weapons!
 * A skin that works on both desktop and mobile
 * @ingroup Skins
 */
class SkinMinerva extends SkinMustache {
	private const NOTIFICATION_BUTTON_CLASSES = [
		'user-button',
		'mw-ui-button',
		'mw-ui-quiet',
		'mw-ui-icon',
		'mw-ui-icon-element',
		'mw-ui-icon-wikimedia-bellOutline-base20'
	];

	/** @const LEAD_SECTION_NUMBER integer which corresponds to the lead section
	 * in editing mode
	 */
	public const LEAD_SECTION_NUMBER = 0;

	/** @var string Name of this skin */
	public $skinname = 'minerva';
	/** @var string Name of this used template */
	public $template = 'MinervaTemplate';

	/** @var SkinOptions */
	private $skinOptions;

	/** @var array|null */
	private $sidebarCachedResult;

	/** @var array|null */
	private $contentNavigationUrls;

	/**
	 * This variable is lazy loaded, please use getPermissions() getter
	 * @see SkinMinerva::getPermissions()
	 * @var IMinervaPagePermissions
	 */
	private $permissions;

	/**
	 * @return SkinOptions
	 */
	private function getSkinOptions() {
		if ( !$this->skinOptions ) {
			$this->skinOptions = MediaWikiServices::getInstance()->getService( 'Minerva.SkinOptions' );
		}
		return $this->skinOptions;
	}

	/**
	 * @return bool
	 */
	private function hasPageActions() {
		$title = $this->getTitle();
		return !$title->isSpecialPage() && !$title->isMainPage() &&
			$this->getContext()->getActionName() === 'view';
	}

	/**
	 * @return bool
	 */
	private function hasSecondaryActions() {
		return !$this->getUserPageHelper()->isUserPage();
	}

	/**
	 * @return bool
	 */
	private function isFallbackEditor() {
		$action = $this->getRequest()->getVal( 'action' );
		return $action === 'edit';
	}

	/**
	 * Returns available page actions if the page has any.
	 *
	 * @param array $nav result of SkinTemplate::buildContentNavigationUrls
	 * @return array|null
	 * @throws MWException
	 */
	private function getPageActions( array $nav ) {
		if ( $this->isFallbackEditor() || !$this->hasPageActions() ) {
			return null;
		}
		$services = MediaWikiServices::getInstance();
		/** @var PageActionsDirector $pageActionsDirector */
		$pageActionsDirector = $services->getService( 'Minerva.Menu.PageActionsDirector' );
		$sidebar = $this->buildSidebar();
		$actions = $nav['actions'] ?? [];
		return $pageActionsDirector->buildMenu( $sidebar['TOOLBOX'], $actions );
	}

	/**
	 * A notification icon that links to Special:Mytalk when Echo is not installed.
	 * Consider upstreaming this to core or removing at a future date.
	 *
	 * @return array
	 */
	private function getNotificationFallbackButton() {
		return [
			'link-class' => [
				'mw-ui-icon',
				'mw-ui-icon-element',
				'mw-ui-icon-wikimedia-bellOutline-base20',
				'mw-ui-button',
				'mw-ui-quiet'
			],
			'href' => SpecialPage::getTitleFor( 'Mytalk' )->getLocalURL(
				[ 'returnto' => $this->getTitle()->getPrefixedText() ]
			),
		];
	}

	/**
	 * Minerva differs from other skins in that for users with unread notifications
	 * instead of a bell with a small square indicating the number of notifications
	 * it shows a red circle with a number inside. Ideally Vector and Minerva would
	 * be treated the same but we'd need to talk to a designer about consolidating these
	 * before making such a decision.
	 *
	 * @param array $alert
	 * @return array
	 */
	private function getNotificationCircleButton( array $alert ) {
		$alertCount = $alert['data']['counter-num'] ?? 0;
		$alertText = $alert['data']['counter-text'] ?? $alertCount;
		$alert['html'] =
			Html::rawElement( 'div', [ 'class' => 'circle' ],
				Html::element( 'span', [
					'data-notification-count' => $alertCount,
				], $alertText )
			);
		$alert['class'] = 'notification-count notification-unseen mw-echo-unseen-notifications';
		$alert['link-class'] = array_merge(
			$alert['link-class'],
			self::NOTIFICATION_BUTTON_CLASSES
		);
		return $alert;
	}

	/**
	 * Removes the OOUI icon class and adds Minerva notification classes.
	 *
	 * @param array $alert
	 * @return array
	 */
	private function getNotificationButton( array $alert ) {
		$linkClass = $alert['link-class'];
		$linkClass = array_merge(
			$linkClass,
			self::NOTIFICATION_BUTTON_CLASSES
		);
		$alert['link-class'] = array_filter(
			$linkClass,
			static function ( $class ) {
				return $class !== 'oo-ui-icon-bellOutline';
			}
		);
		return $alert;
	}

	/**
	 * Caches content navigation urls locally for use inside getTemplateData
	 *
	 * @inheritDoc
	 */
	protected function runOnSkinTemplateNavigationHooks( SkinTemplate $skin, &$contentNavigationUrls ) {
		parent::runOnSkinTemplateNavigationHooks( $skin, $contentNavigationUrls );
		// There are some SkinTemplate modifications that occur after the execution of this hook
		// to add rel attributes and ID attributes.
		// The only one Minerva needs is this one so we manually add it.
		$isSpecialPage = $skin->getTitle()->isSpecialPage();
		foreach ( array_keys( $contentNavigationUrls['namespaces'] ) as $id ) {
			if ( in_array( $id, [ 'user_talk', 'talk' ] ) ) {
				$contentNavigationUrls['namespaces'][ $id ]['rel'] = 'discussion';
			}
		}
		// Do not output the "Special page" tab.
		if ( $isSpecialPage ) {
			unset( $contentNavigationUrls['namespaces']['special'] );
		}
		$this->contentNavigationUrls = $contentNavigationUrls;
		if ( $this->getUser()->isRegistered() ) {
			// Unset notice icon. Minerva only shows one entry point to notifications.
			// This can be reconsidered with a solution to https://phabricator.wikimedia.org/T142981
			unset( $contentNavigationUrls['notifications']['notifications-notice'] );
			// Shown to logged in users when Echo is not installed:
			if ( count( $contentNavigationUrls['notifications'] ) === 0 ) {
				$contentNavigationUrls['notifications']['mytalks'] = $this->getNotificationFallbackButton();
			} else {
				$alert = $contentNavigationUrls['notifications']['notifications-alert'] ?? null;
				if ( $alert ) {
					// @phan-suppress-next-line PhanTypeMismatchDimFetch False positive
					$alertCount = $alert['data']['counter-num'] ?? 0;
					$contentNavigationUrls['notifications']['notifications-alert'] = $alertCount > 0 ?
						$this->getNotificationCircleButton( $alert ) : $this->getNotificationButton( $alert );
				}
			}
		}
	}

	/**
	 * @inheritDoc
	 */
	public function getTemplateData(): array {
			$data = parent::getTemplateData();
			// FIXME: Can we use $data instead of calling buildContentNavigationUrls ?
			$nav = $this->contentNavigationUrls;
			if ( $nav === null ) {
				throw new RuntimeException( 'contentNavigationUrls was not set as expected.' );
			}
			if ( !$this->hasCategoryLinks() ) {
				unset( $data['html-categories'] );
			}

			// Special handling for certain pages.
			// This is technical debt that should be upstreamed to core.
			$isUserPage = $this->getUserPageHelper()->isUserPage();
			$isUserPageAccessible = $this->getUserPageHelper()->isUserPageAccessibleToCurrentUser();
			if ( $isUserPage && $isUserPageAccessible ) {
				$data['html-title-heading'] = $this->getUserPageHeadingHtml( $data['html-title-heading' ] );
			}

			$usermessage = $data['html-user-message'] ?? '';
			if ( $usermessage ) {
				$data['html-user-message'] = Html::warningBox(
					'<span class="mw-ui-icon mw-ui-icon-wikimedia-userTalk-warning"></span>&nbsp;'
						. $usermessage,
					'minerva-anon-talk-message'
				);
			}
			return $data + [
				'array-minerva-banners' => $this->prepareBanners( $data['html-site-notice'] ),
				'data-minerva-main-menu' => $this->getMainMenu()->getMenuData(
					$nav,
					$this->buildSidebar()
				)['items'],
				'html-minerva-tagline' => $this->getTaglineHtml(),
				'html-minerva-post-heading' => $this->isTalkPageWithViewAction()
					? $this->getTalkPagePostHeadingHtml()
					: '',
				'html-minerva-user-menu' => $this->getPersonalToolsMenu( $nav['user-menu'] ),
				'is-minerva-beta' => $this->getSkinOptions()->get( SkinOptions::BETA_MODE ),
				'data-minerva-tabs' => $this->getTabsData( $nav ),
				'data-minerva-page-actions' => $this->getPageActions( $nav ),
				'data-minerva-secondary-actions' => $this->getSecondaryActions( $nav ),
				'html-minerva-subject-link' => $this->getSubjectPage(),
				'data-minerva-history-link' => $this->getHistoryLink( $this->getTitle() ),
			];
	}

	/**
	 * Tabs are available if a page has page actions but is not the talk page of
	 * the main page.
	 *
	 * Special pages have tabs if SkinOptions::TABS_ON_SPECIALS is enabled.
	 * This is used by Extension:GrowthExperiments
	 *
	 * @return bool
	 */
	private function hasPageTabs() {
		$title = $this->getTitle();
		$skinOptions = $this->getSkinOptions();
		$isSpecialPage = $title->isSpecialPage();
		$subjectPage = MediaWikiServices::getInstance()->getNamespaceInfo()
			->getSubjectPage( $title );
		$isMainPageTalk = Title::newFromLinkTarget( $subjectPage )->isMainPage();
		return (
				$this->hasPageActions() && !$isMainPageTalk &&
				$skinOptions->get( SkinOptions::TALK_AT_TOP )
			) || (
				$isSpecialPage &&
				$skinOptions->get( SkinOptions::TABS_ON_SPECIALS )
			);
	}

	/**
	 * @param array $contentNavigationUrls
	 * @return array
	 */
	private function getTabsData( array $contentNavigationUrls ) {
		$hasPageTabs = $this->hasPageTabs();
		if ( !$hasPageTabs ) {
			return [];
		}
		return $contentNavigationUrls ? [
			'items' => array_values( $contentNavigationUrls['namespaces'] ),
		] : [];
	}

	/**
	 * Lazy load the permissions object. We don't want to initialize it as it requires many
	 * dependencies, sometimes some of those dependencies cannot be fulfilled (like missing Title
	 * object)
	 * @return IMinervaPagePermissions
	 */
	private function getPermissions(): IMinervaPagePermissions {
		if ( $this->permissions === null ) {
			$this->permissions = MediaWikiServices::getInstance()
				->getService( 'Minerva.Permissions' )
				->setContext( $this->getContext() );
		}
		return $this->permissions;
	}

	/**
	 * Initalized main menu. Please use getter.
	 * @var MainMenuDirector
	 */
	private $mainMenu;

	/**
	 * Build the Main Menu Director by passing the skin options
	 *
	 * @return MainMenuDirector
	 */
	protected function getMainMenu(): MainMenuDirector {
		if ( !$this->mainMenu ) {
			$this->mainMenu = MediaWikiServices::getInstance()->getService( 'Minerva.Menu.MainDirector' );
		}
		return $this->mainMenu;
	}

	/**
	 * Prepare all Minerva menus
	 *
	 * @param array $personalUrls result of SkinTemplate::buildPersonalUrls
	 * @return string|null
	 */
	private function getPersonalToolsMenu( array $personalUrls ) {
		$services = MediaWikiServices::getInstance();
		/** @var UserMenuDirector $userMenuDirector */
		$userMenuDirector = $services->getService( 'Minerva.Menu.UserMenuDirector' );
		return $userMenuDirector->renderMenuData( $personalUrls );
	}

	/**
	 * @return string
	 */
	protected function getSubjectPage() {
		$services = MediaWikiServices::getInstance();
		$title = $this->getTitle();
		$skinOptions = $this->getSkinOptions();

		// If it's a talk page, add a link to the main namespace page
		// In AMC we do not need to do this as there is an easy way back to the article page
		// via the talk/article tabs.
		if ( $title->isTalkPage() && !$skinOptions->get( SkinOptions::TALK_AT_TOP ) ) {
			// if it's a talk page for which we have a special message, use it
			switch ( $title->getNamespace() ) {
				case NS_USER_TALK:
					$msg = 'mobile-frontend-talk-back-to-userpage';
					break;
				case NS_PROJECT_TALK:
					$msg = 'mobile-frontend-talk-back-to-projectpage';
					break;
				case NS_FILE_TALK:
					$msg = 'mobile-frontend-talk-back-to-filepage';
					break;
				default: // generic (all other NS)
					$msg = 'mobile-frontend-talk-back-to-page';
			}
			$subjectPage = $services->getNamespaceInfo()->getSubjectPage( $title );

			return MediaWikiServices::getInstance()->getLinkRenderer()->makeLink(
				$subjectPage,
				$this->msg( $msg, $title->getText() )->text(),
				[
					'data-event-name' => 'talk.returnto',
					'class' => 'return-link'
				]
			);
		} else {
			return '';
		}
	}

	/**
	 * Overrides Skin::doEditSectionLink
	 * @param Title $nt The title being linked to (may not be the same as
	 *   the current page, if the section is included from a template)
	 * @param string $section
	 * @param string|null $tooltip
	 * @param Language $lang
	 * @return string
	 */
	public function doEditSectionLink( Title $nt, $section, $tooltip, Language $lang ) {
		if ( $this->getPermissions()->isAllowed( IMinervaPagePermissions::EDIT_OR_CREATE ) &&
			 !$nt->isMainPage() ) {
			$message = $this->msg( 'mobile-frontend-editor-edit' )->inLanguage( $lang )->text();
			$html = Html::openElement( 'span', [ 'class' => 'mw-editsection' ] );
			$html .= Html::element( 'a', [
				'href' => $nt->getLocalURL( [ 'action' => 'edit', 'section' => $section ] ),
				'title' => $this->msg( 'editsectionhint', $tooltip )->inLanguage( $lang )->text(),
				'data-section' => $section,
				// Note visibility of the edit section link button is controlled by .edit-page in ui.less so
				// we default to enabled even though this may not be true.
				'class' => MinervaUI::iconClass(
					'edit-base20', 'element', 'edit-page mw-ui-icon-flush-right', 'wikimedia'
				),
			], $message );
			$html .= Html::closeElement( 'span' );
			return $html;
		}
		return '';
	}

	/**
	 * Takes a title and returns classes to apply to the body tag
	 * @param Title $title
	 * @return string
	 */
	public function getPageClasses( $title ) {
		$skinOptions = $this->getSkinOptions();
		$className = parent::getPageClasses( $title );
		$className .= ' ' . ( $skinOptions->get( SkinOptions::BETA_MODE )
				? 'beta' : 'stable' );

		if ( $title->isMainPage() ) {
			$className .= ' page-Main_Page ';
		}

		if ( $this->getUser()->isRegistered() ) {
			$className .= ' is-authenticated';
		}
		// The new treatment should only apply to the main namespace
		if (
			$title->getNamespace() === NS_MAIN &&
			$skinOptions->get( SkinOptions::PAGE_ISSUES )
		) {
			$className .= ' issues-group-B';
		}
		return $className;
	}

	/**
	 * Whether the output page contains category links and the category feature is enabled.
	 * @return bool
	 */
	private function hasCategoryLinks() {
		$skinOptions = $this->getSkinOptions();
		if ( !$skinOptions->get( SkinOptions::CATEGORIES ) ) {
			return false;
		}
		$categoryLinks = $this->getOutput()->getCategoryLinks();

		if ( !count( $categoryLinks ) ) {
			return false;
		}
		return !empty( $categoryLinks['normal'] ) || !empty( $categoryLinks['hidden'] );
	}

	/**
	 * @return SkinUserPageHelper
	 */
	public function getUserPageHelper() {
		return MediaWikiServices::getInstance()->getService( 'Minerva.SkinUserPageHelper' );
	}

	/**
	 * Get a history link which describes author and relative time of last edit
	 * @param Title $title The Title object of the page being viewed
	 * @param string $timestamp
	 * @return array
	 */
	protected function getRelativeHistoryLink( Title $title, $timestamp ) {
		$user = $this->getUser();
		$userDate = $this->getLanguage()->userDate( $timestamp, $user );
		$text = $this->msg(
			'minerva-last-modified-date', $userDate,
			$this->getLanguage()->userTime( $timestamp, $user )
		)->parse();
		return [
			// Use $edit['timestamp'] (Unix format) instead of $timestamp (MW format)
			'data-timestamp' => wfTimestamp( TS_UNIX, $timestamp ),
			'href' => $this->getHistoryUrl( $title ),
			'text' => $text,
		] + $this->getRevisionEditorData( $title );
	}

	/**
	 * Get a history link which makes no reference to user or last edited time
	 * @param Title $title The Title object of the page being viewed
	 * @return array
	 */
	protected function getGenericHistoryLink( Title $title ) {
		$text = $this->msg( 'mobile-frontend-history' )->plain();
		return [
			'href' => $this->getHistoryUrl( $title ),
			'text' => $text,
		];
	}

	/**
	 * Get the URL for the history page for the given title using Special:History
	 * when available.
	 * @param Title $title The Title object of the page being viewed
	 * @return string
	 */
	protected function getHistoryUrl( Title $title ) {
		return ExtensionRegistry::getInstance()->isLoaded( 'MobileFrontend' ) &&
			SpecialMobileHistory::shouldUseSpecialHistory( $title, $this->getUser() ) ?
			SpecialPage::getTitleFor( 'History', $title )->getLocalURL() :
			$title->getLocalURL( [ 'action' => 'history' ] );
	}

	/**
	 * Prepare the content for the 'last edited' message, e.g. 'Last edited on 30 August
	 * 2013, at 23:31'. This message is different for the main page since main page
	 * content is typically transcluded rather than edited directly.
	 *
	 * The relative time is only rendered on the latest revision.
	 * For older revisions the last modified information will not render with a relative time
	 * nor will it show the name of the editor.
	 * @param Title $title The Title object of the page being viewed
	 * @return array|null
	 */
	protected function getHistoryLink( Title $title ) {
		if ( !$title->exists() ||
			$this->getContext()->getActionName() !== 'view'
		) {
			return null;
		}

		$out = $this->getOutput();

		if ( !$out->getRevisionId() || !$out->isRevisionCurrent() || $title->isMainPage() ) {
			$historyLink = $this->getGenericHistoryLink( $title );
		} else {
			// Get rev_timestamp of current revision (preloaded by MediaWiki core)
			$timestamp = $out->getRevisionTimestamp();
			if ( !$timestamp ) {
				# No cached timestamp, load it from the database
				$revisionLookup = MediaWikiServices::getInstance()->getRevisionLookup();
				$timestamp = $revisionLookup->getTimestampFromId( $out->getRevisionId() );
			}
			$historyLink = $this->getRelativeHistoryLink( $title, $timestamp );
		}

		return $historyLink + [
			'historyIconClass' => MinervaUI::iconClass(
				'history-base20', 'mw-ui-icon-small', '', 'wikimedia'
			),
			'arrowIconClass' => MinervaUI::iconClass(
				'expand-gray', 'small',
				'mf-mw-ui-icon-rotate-anti-clockwise indicator',
				// Uses icon in MobileFrontend so must be prefixed mf.
				// Without MobileFrontend it will not render.
				// Rather than maintain 2 versions (and variants) of the arrow icon which can conflict
				// with each othe and bloat CSS, we'll
				// use the MobileFrontend one. Long term when T177432 and T160690 are resolved
				// we should be able to use one icon definition and break this dependency.
				'mf'
			),
		];
	}

	/**
	 * Returns data attributes representing the editor for the current revision.
	 * @param LinkTarget $title The Title object of the page being viewed
	 * @return array representing user with name and gender fields. Empty if the editor no longer
	 *   exists in the database or is hidden from public view.
	 */
	private function getRevisionEditorData( LinkTarget $title ) {
		$services = MediaWikiServices::getInstance();
		$rev = $services->getRevisionLookup()
			->getRevisionByTitle( $title );
		$result = [];
		if ( $rev ) {
			$revUser = $rev->getUser();
			// Note the user will only be returned if that information is public
			if ( $revUser ) {
				$editorName = $revUser->getName();
				$editorGender = $services->getGenderCache()->getGenderOf( $revUser, __METHOD__ );
				$result += [
					'data-user-name' => $editorName,
					'data-user-gender' => $editorGender,
				];
			}
		}
		return $result;
	}

	/**
	 * Returns the HTML representing the tagline
	 * @return string HTML for tagline
	 */
	protected function getTaglineHtml() {
		$tagline = '';

		if ( $this->getUserPageHelper()->isUserPage() ) {
			$pageUser = $this->getUserPageHelper()->getPageUser();
			$fromDate = $pageUser->getRegistration();

			if ( $this->getUserPageHelper()->isUserPageAccessibleToCurrentUser() && is_string( $fromDate ) ) {
				$fromDateTs = wfTimestamp( TS_UNIX, $fromDate );
				$genderCache = MediaWikiServices::getInstance()->getGenderCache();

				// This is shown when js is disabled. js enhancement made due to caching
				$tagline = $this->msg( 'mobile-frontend-user-page-member-since',
						$this->getLanguage()->userDate( new MWTimestamp( $fromDateTs ), $this->getUser() ),
						$pageUser )->text();

				// Define html attributes for usage with js enhancement (unix timestamp, gender)
				$attrs = [ 'id' => 'tagline-userpage',
					'data-userpage-registration-date' => $fromDateTs,
					'data-userpage-gender' => $genderCache->getGenderOf( $pageUser, __METHOD__ ) ];
			}
		} else {
			$title = $this->getTitle();
			if ( $title ) {
				$out = $this->getOutput();
				$tagline = $out->getProperty( 'wgMFDescription' );
			}
		}

		$attrs[ 'class' ] = 'tagline';
		return Html::element( 'div', $attrs, $tagline );
	}

	/**
	 * Returns the HTML representing the heading.
	 *
	 * @param string $heading The heading suggested by core.
	 * @return string HTML for header
	 */
	private function getUserPageHeadingHtml( $heading ) {
		// The heading is just the username without namespace
		// This is escaped as a precaution (user name should be safe).
		return Html::rawElement( 'h1',
			// These IDs and classes should match Skin::getTemplateData
			[
				'id' => 'firstHeading',
				'class' => 'firstHeading mw-first-heading mw-minerva-user-heading',
			],
			htmlspecialchars(
				$this->getUserPageHelper()->getPageUser()->getName()
			)
		);
	}

	/**
	 * @return bool Whether or not current title is a Talk page with the default
	 * action ('view')
	 */
	private function isTalkPageWithViewAction() {
		$title = $this->getTitle();

		// Hook is @unstable and only for use by DiscussionTools. Do not use for any other purpose.
		$hookContainer = MediaWikiServices::getInstance()->getHookContainer();
		if ( !$hookContainer->run( 'MinervaNeueTalkPageOverlay', [ $title, $this->getOutput() ] ) ) {
			return false;
		}

		return $title->isTalkPage() && $this->getContext()->getActionName() === "view";
	}

	/**
	 * @internal Should not be used outside Minerva.
	 * @todo Find better place for this.
	 *
	 * @return bool Whether or not the simplified talk page is enabled and action is 'view'
	 */
	public function isSimplifiedTalkPageEnabled(): bool {
		$title = $this->getTitle();
		$skinOptions = $this->getSkinOptions();

		return $this->isTalkPageWithViewAction() &&
			$skinOptions->get( SkinOptions::SIMPLIFIED_TALK ) &&
			// Only if viewing the latest revision, as we can't get the section numbers otherwise
			// (and even if we could, they would be useless, because edits often add and remove sections).
			$this->getOutput()->getRevisionId() === $title->getLatestRevID() &&
			$title->getContentModel() === CONTENT_MODEL_WIKITEXT;
	}

	/**
	 * Returns the postheadinghtml for the talk page with view action
	 *
	 * @return string HTML for postheadinghtml
	 */
	private function getTalkPagePostHeadingHtml() {
		$title = $this->getTitle();
		$html = '';

		// T237589: We don't want to show the add discussion button on Flow pages,
		// only wikitext pages
		if ( $this->getPermissions()->isTalkAllowed() &&
			$title->getContentModel() === CONTENT_MODEL_WIKITEXT
		) {
			$addTopicButton = $this->getTalkButton( $title, wfMessage(
				'minerva-talk-add-topic' )->text(), true );
			$html = Html::element( 'a', $addTopicButton['attributes'] + [
				'data-event-name' => 'talkpage.add-topic'
			], $addTopicButton['label'] );
		}

		$title = $this->getTitle();
		if ( $this->isSimplifiedTalkPageEnabled() && $title->canExist() ) {
			$parserOutputAccess = MediaWikiServices::getInstance()->getParserOutputAccess();
			$parserOptions = ParserOptions::newFromContext( $this->getContext() );
			$pageRecord = $title->toPageRecord();
			$status = $parserOutputAccess->getParserOutput( $pageRecord, $parserOptions );
			$statusValue = $status->getValue();
			$sectionCount = ( $status->isGood() && $statusValue instanceof ParserOutput )
				? count( $statusValue->getSections() )
				: 0;
			$message = $sectionCount > 0 ? wfMessage( 'minerva-talk-explained' )
				: wfMessage( 'minerva-talk-explained-empty' );
			$html .= Html::element( 'div', [ 'class' =>
				'minerva-talk-content-explained' ], $message->text() );
		}

		return $html;
	}

	/**
	 * Load internal banner content to show in pre content in template
	 * Beware of HTML caching when using this function.
	 * Content set as "internalbanner"
	 * @param string $siteNotice HTML fragment
	 * @return array
	 */
	protected function prepareBanners( $siteNotice ) {
		$banners = [];
		if ( $siteNotice && $this->getConfig()->get( 'MinervaEnableSiteNotice' ) ) {
			$banners[] = '<div id="siteNotice">' . $siteNotice . '</div>';
		} else {
			$banners[] = '<div id="siteNotice"></div>';
		}
		return $banners;
	}

	/**
	 * Returns an array with details for a language button.
	 * @return array
	 */
	protected function getLanguageButton() {
		$languageUrl = SpecialPage::getTitleFor(
			'MobileLanguages',
			$this->getSkin()->getTitle()
		)->getLocalURL();

		return [
			'attributes' => [
				'class' => 'language-selector',
				'href' => $languageUrl,
			],
			'label' => $this->msg( 'mobile-frontend-language-article-heading' )->text()
		];
	}

	/**
	 * Returns an array with details for a talk button.
	 * @param Title $talkTitle Title object of the talk page
	 * @param string $label Button label
	 * @param bool $addSection (optional) when added the talk button will render
	 *  as an add topic button. Defaults to false.
	 * @return array
	 */
	protected function getTalkButton( $talkTitle, $label, $addSection = false ) {
		if ( $addSection ) {
			$params = [ 'action' => 'edit', 'section' => 'new' ];
			$className = 'minerva-talk-add-button ' . MinervaUI::buttonClass( 'progressive', 'button' );
		} else {
			$params = [];
			$className = 'talk';
		}

		return [
			'attributes' => [
				'href' => $talkTitle->getLinkURL( $params ),
				'data-title' => $talkTitle->getFullText(),
				'class' => $className,
			],
			'label' => $label,
		];
	}

	/**
	 * Returns an array of links for page secondary actions
	 * @param array $contentNavigationUrls
	 * @return array|null
	 */
	protected function getSecondaryActions( array $contentNavigationUrls ) {
		if ( $this->isFallbackEditor() || !$this->hasSecondaryActions() ) {
			return null;
		}

		$services = MediaWikiServices::getInstance();
		$skinOptions = $this->getSkinOptions();
		$namespaceInfo = $services->getNamespaceInfo();
		/** @var \MediaWiki\Minerva\LanguagesHelper $languagesHelper */
		$languagesHelper = $services->getService( 'Minerva.LanguagesHelper' );
		$buttons = [];
		// always add a button to link to the talk page
		// it will link to the wikitext talk page
		$title = $this->getTitle();
		$subjectPage = Title::newFromLinkTarget( $namespaceInfo->getSubjectPage( $title ) );
		$talkAtBottom = !$skinOptions->get( SkinOptions::TALK_AT_TOP ) ||
			$subjectPage->isMainPage();
		if ( !$this->getUserPageHelper()->isUserPage() &&
			$this->getPermissions()->isTalkAllowed() && $talkAtBottom &&
			// When showing talk at the bottom we restrict this so it is not shown to anons
			// https://phabricator.wikimedia.org/T54165
			// This whole code block can be removed when SkinOptions::TALK_AT_TOP is always true
			$this->getUser()->isRegistered() &&
			!$this->isTalkPageWithViewAction()
		) {
			$namespaces = $contentNavigationUrls['namespaces'];
			// FIXME [core]: This seems unnecessary..
			$subjectId = $title->getNamespaceKey( '' );
			$talkId = $subjectId === 'main' ? 'talk' : "{$subjectId}_talk";

			if ( isset( $namespaces[$talkId] ) ) {
				$talkButton = $namespaces[$talkId];
				$talkTitle = Title::newFromLinkTarget( $namespaceInfo->getTalkPage( $title ) );

				$buttons['talk'] = $this->getTalkButton( $talkTitle, $talkButton['text'] );
			}
		}

		if ( $languagesHelper->doesTitleHasLanguagesOrVariants( $title ) && $title->isMainPage() ) {
			$buttons['language'] = $this->getLanguageButton();
		}

		return $buttons;
	}

	/**
	 * @inheritDoc
	 * @return array
	 */
	protected function getJsConfigVars(): array {
		$title = $this->getTitle();
		$skinOptions = $this->getSkinOptions();

		return array_merge( parent::getJsConfigVars(), [
			'wgMinervaPermissions' => [
				'watch' => $this->getPermissions()->isAllowed( IMinervaPagePermissions::WATCH ),
				'talk' => $this->getUserPageHelper()->isUserPage() ||
					( $this->getPermissions()->isTalkAllowed() || $title->isTalkPage() ) &&
					$this->isWikiTextTalkPage()
			],
			'wgMinervaFeatures' => $skinOptions->getAll(),
			'wgMinervaDownloadNamespaces' => $this->getConfig()->get( 'MinervaDownloadNamespaces' ),
		] );
	}

	/**
	 * Returns true, if the talk page of this page is wikitext-based.
	 * @return bool
	 */
	protected function isWikiTextTalkPage() {
		$title = $this->getTitle();
		if ( !$title->isTalkPage() ) {
			$namespaceInfo = MediaWikiServices::getInstance()->getNamespaceInfo();
			$title = Title::newFromLinkTarget( $namespaceInfo->getTalkPage( $title ) );
		}
		return $title->isWikitextPage();
	}

	/**
	 * Returns the javascript entry modules to load. Only modules that need to
	 * be overriden or added conditionally should be placed here.
	 * @return array
	 */
	public function getDefaultModules() {
		$modules = parent::getDefaultModules();

		// FIXME: T223204: Dequeue default content modules except for the history
		// action. Allow default history action content modules
		// in order to enable toggling of the
		// filters. Long term this won't be necessary when T111565 is resolved and a
		// more general solution can be used.
		if ( $this->getContext()->getActionName() !== 'history' ) {
			// dequeue default content modules (toc, sortable, collapsible, etc.)
			$modules['content'] = array_diff( $modules['content'], [
				// T233340
				'jquery.tablesorter',
				// T111565
				'jquery.makeCollapsible',
				// Minerva provides its own implementation. Loading this will break display.
				'mediawiki.toc'
			] );
			// dequeue styles associated with `content` key.
			$modules['styles']['content'] = array_diff( $modules['styles']['content'], [
				// T233340
				'jquery.tablesorter.styles',
				// T111565
				'jquery.makeCollapsible.styles',
			] );
		}
		$modules['styles']['core'] = $this->getSkinStyles();

		$modules['minerva'] = [
			'skins.minerva.scripts'
		];

		return $modules;
	}

	/**
	 * Provide styles required to present the server rendered page in this skin. Additional styles
	 * may be loaded dynamically by the client.
	 *
	 * Any styles returned by this method are loaded on the critical rendering path as linked
	 * stylesheets. I.e., they are required to load on the client before first paint.
	 *
	 * @return array
	 */
	protected function getSkinStyles(): array {
		$title = $this->getTitle();
		$skinOptions = $this->getSkinOptions();
		$styles = [
			'skins.minerva.base.styles',
			'skins.minerva.content.styles.images',
			'mediawiki.hlist',
			'mediawiki.ui.icon',
			'mediawiki.ui.button',
			'skins.minerva.icons.wikimedia',
			'skins.minerva.mainMenu.icons',
			'skins.minerva.mainMenu.styles',
		];
		if ( $title->isMainPage() ) {
			$styles[] = 'skins.minerva.mainPage.styles';
		} elseif ( $this->getUserPageHelper()->isUserPage() ) {
			$styles[] = 'skins.minerva.userpage.styles';
		} elseif ( $this->isTalkPageWithViewAction() ) {
			$styles[] = 'skins.minerva.talk.styles';
		}

		if ( $this->hasCategoryLinks() ) {
			$styles[] = 'skins.minerva.categories.styles';
		}

		if ( $this->getUser()->isRegistered() ) {
			$styles[] = 'skins.minerva.loggedin.styles';
			$styles[] = 'skins.minerva.icons.loggedin';
		}

		// When any of these features are enabled in production
		// remove the if condition
		// and move the associated LESS file inside `skins.minerva.amc.styles`
		// into a more appropriate module.
		if (
			$skinOptions->get( SkinOptions::PERSONAL_MENU ) ||
			$skinOptions->get( SkinOptions::TALK_AT_TOP ) ||
			$skinOptions->get( SkinOptions::HISTORY_IN_PAGE_ACTIONS ) ||
			$skinOptions->get( SkinOptions::TOOLBAR_SUBMENU )
		) {
			// SkinOptions::PERSONAL_MENU + SkinOptions::TOOLBAR_SUBMENU uses ToggleList
			// SkinOptions::TALK_AT_TOP uses tabs.less
			// SkinOptions::HISTORY_IN_PAGE_ACTIONS + SkinOptions::TOOLBAR_SUBMENU uses pageactions.less
			$styles[] = 'skins.minerva.amc.styles';
		}

		if ( $skinOptions->get( SkinOptions::PERSONAL_MENU ) ) {
			// If ever enabled as the default, please remove the duplicate icons
			// inside skins.minerva.mainMenu.icons. See comment for MAIN_MENU_EXPANDED
			$styles[] = 'skins.minerva.personalMenu.icons';
		}

		if (
			$skinOptions->get( SkinOptions::MAIN_MENU_EXPANDED )
		) {
			// If ever enabled as the default, please review skins.minerva.mainMenu.icons
			// and remove any unneeded icons
			$styles[] = 'skins.minerva.mainMenu.advanced.icons';
		}
		if (
			$skinOptions->get( SkinOptions::PERSONAL_MENU ) ||
			$skinOptions->get( SkinOptions::TOOLBAR_SUBMENU )
		) {
			// SkinOptions::PERSONAL_MENU requires the `userTalk` icon.
			// SkinOptions::TOOLBAR_SUBMENU requires the rest of the icons including `overflow`.
			// Note `skins.minerva.overflow.icons` is pulled down by skins.minerva.scripts but the menu can
			// work without JS.
			$styles[] = 'skins.minerva.overflow.icons';
		}

		return $styles;
	}
}