MessageCache invalidation improvements

[mediawiki.git] / includes / specials / SpecialUndelete.php

<?php
/**
 * Implements Special:Undelete
 *
 * 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
 * @ingroup SpecialPage
 */
use MediaWiki\MediaWikiServices;

/**
 * Used to show archived pages and eventually restore them.
 *
 * @ingroup SpecialPage
 */
class PageArchive {
        /** @var Title */
        protected $title;

        /** @var Status */
        protected $fileStatus;

        /** @var Status */
        protected $revisionStatus;

        /** @var Config */
        protected $config;

        function __construct( $title, Config $config = null ) {
                if ( is_null( $title ) ) {
                        throw new MWException( __METHOD__ . ' given a null title.' );
                }
                $this->title = $title;
                if ( $config === null ) {
                        wfDebug( __METHOD__ . ' did not have a Config object passed to it' );
                        $config = MediaWikiServices::getInstance()->getMainConfig();
                }
                $this->config = $config;
        }

        public function doesWrites() {
                return true;
        }

        /**
         * List all deleted pages recorded in the archive table. Returns result
         * wrapper with (ar_namespace, ar_title, count) fields, ordered by page
         * namespace/title.
         *
         * @return ResultWrapper
         */
        public static function listAllPages() {
                $dbr = wfGetDB( DB_REPLICA );

                return self::listPages( $dbr, '' );
        }

        /**
         * List deleted pages recorded in the archive table matching the
         * given title prefix.
         * Returns result wrapper with (ar_namespace, ar_title, count) fields.
         *
         * @param string $prefix Title prefix
         * @return ResultWrapper
         */
        public static function listPagesByPrefix( $prefix ) {
                $dbr = wfGetDB( DB_REPLICA );

                $title = Title::newFromText( $prefix );
                if ( $title ) {
                        $ns = $title->getNamespace();
                        $prefix = $title->getDBkey();
                } else {
                        // Prolly won't work too good
                        // @todo handle bare namespace names cleanly?
                        $ns = 0;
                }

                $conds = [
                        'ar_namespace' => $ns,
                        'ar_title' . $dbr->buildLike( $prefix, $dbr->anyString() ),
                ];

                return self::listPages( $dbr, $conds );
        }

        /**
         * @param IDatabase $dbr
         * @param string|array $condition
         * @return bool|ResultWrapper
         */
        protected static function listPages( $dbr, $condition ) {
                return $dbr->select(
                        [ 'archive' ],
                        [
                                'ar_namespace',
                                'ar_title',
                                'count' => 'COUNT(*)'
                        ],
                        $condition,
                        __METHOD__,
                        [
                                'GROUP BY' => [ 'ar_namespace', 'ar_title' ],
                                'ORDER BY' => [ 'ar_namespace', 'ar_title' ],
                                'LIMIT' => 100,
                        ]
                );
        }

        /**
         * List the revisions of the given page. Returns result wrapper with
         * (ar_minor_edit, ar_timestamp, ar_user, ar_user_text, ar_comment) fields.
         *
         * @return ResultWrapper
         */
        function listRevisions() {
                $dbr = wfGetDB( DB_REPLICA );

                $tables = [ 'archive' ];

                $fields = [
                        'ar_minor_edit', 'ar_timestamp', 'ar_user', 'ar_user_text',
                        'ar_comment', 'ar_len', 'ar_deleted', 'ar_rev_id', 'ar_sha1',
                ];

                if ( $this->config->get( 'ContentHandlerUseDB' ) ) {
                        $fields[] = 'ar_content_format';
                        $fields[] = 'ar_content_model';
                }

                $conds = [ 'ar_namespace' => $this->title->getNamespace(),
                        'ar_title' => $this->title->getDBkey() ];

                $options = [ 'ORDER BY' => 'ar_timestamp DESC' ];

                $join_conds = [];

                ChangeTags::modifyDisplayQuery(
                        $tables,
                        $fields,
                        $conds,
                        $join_conds,
                        $options,
                        ''
                );

                return $dbr->select( $tables,
                        $fields,
                        $conds,
                        __METHOD__,
                        $options,
                        $join_conds
                );
        }

        /**
         * List the deleted file revisions for this page, if it's a file page.
         * Returns a result wrapper with various filearchive fields, or null
         * if not a file page.
         *
         * @return ResultWrapper
         * @todo Does this belong in Image for fuller encapsulation?
         */
        function listFiles() {
                if ( $this->title->getNamespace() != NS_FILE ) {
                        return null;
                }

                $dbr = wfGetDB( DB_REPLICA );
                return $dbr->select(
                        'filearchive',
                        ArchivedFile::selectFields(),
                        [ 'fa_name' => $this->title->getDBkey() ],
                        __METHOD__,
                        [ 'ORDER BY' => 'fa_timestamp DESC' ]
                );
        }

        /**
         * Return a Revision object containing data for the deleted revision.
         * Note that the result *may* or *may not* have a null page ID.
         *
         * @param string $timestamp
         * @return Revision|null
         */
        function getRevision( $timestamp ) {
                $dbr = wfGetDB( DB_REPLICA );

                $fields = [
                        'ar_rev_id',
                        'ar_text',
                        'ar_comment',
                        'ar_user',
                        'ar_user_text',
                        'ar_timestamp',
                        'ar_minor_edit',
                        'ar_flags',
                        'ar_text_id',
                        'ar_deleted',
                        'ar_len',
                        'ar_sha1',
                ];

                if ( $this->config->get( 'ContentHandlerUseDB' ) ) {
                        $fields[] = 'ar_content_format';
                        $fields[] = 'ar_content_model';
                }

                $row = $dbr->selectRow( 'archive',
                        $fields,
                        [ 'ar_namespace' => $this->title->getNamespace(),
                                'ar_title' => $this->title->getDBkey(),
                                'ar_timestamp' => $dbr->timestamp( $timestamp ) ],
                        __METHOD__ );

                if ( $row ) {
                        return Revision::newFromArchiveRow( $row, [ 'title' => $this->title ] );
                }

                return null;
        }

        /**
         * Return the most-previous revision, either live or deleted, against
         * the deleted revision given by timestamp.
         *
         * May produce unexpected results in case of history merges or other
         * unusual time issues.
         *
         * @param string $timestamp
         * @return Revision|null Null when there is no previous revision
         */
        function getPreviousRevision( $timestamp ) {
                $dbr = wfGetDB( DB_REPLICA );

                // Check the previous deleted revision...
                $row = $dbr->selectRow( 'archive',
                        'ar_timestamp',
                        [ 'ar_namespace' => $this->title->getNamespace(),
                                'ar_title' => $this->title->getDBkey(),
                                'ar_timestamp < ' .
                                        $dbr->addQuotes( $dbr->timestamp( $timestamp ) ) ],
                        __METHOD__,
                        [
                                'ORDER BY' => 'ar_timestamp DESC',
                                'LIMIT' => 1 ] );
                $prevDeleted = $row ? wfTimestamp( TS_MW, $row->ar_timestamp ) : false;

                $row = $dbr->selectRow( [ 'page', 'revision' ],
                        [ 'rev_id', 'rev_timestamp' ],
                        [
                                'page_namespace' => $this->title->getNamespace(),
                                'page_title' => $this->title->getDBkey(),
                                'page_id = rev_page',
                                'rev_timestamp < ' .
                                        $dbr->addQuotes( $dbr->timestamp( $timestamp ) ) ],
                        __METHOD__,
                        [
                                'ORDER BY' => 'rev_timestamp DESC',
                                'LIMIT' => 1 ] );
                $prevLive = $row ? wfTimestamp( TS_MW, $row->rev_timestamp ) : false;
                $prevLiveId = $row ? intval( $row->rev_id ) : null;

                if ( $prevLive && $prevLive > $prevDeleted ) {
                        // Most prior revision was live
                        return Revision::newFromId( $prevLiveId );
                } elseif ( $prevDeleted ) {
                        // Most prior revision was deleted
                        return $this->getRevision( $prevDeleted );
                }

                // No prior revision on this page.
                return null;
        }

        /**
         * Get the text from an archive row containing ar_text, ar_flags and ar_text_id
         *
         * @param object $row Database row
         * @return string
         */
        function getTextFromRow( $row ) {
                if ( is_null( $row->ar_text_id ) ) {
                        // An old row from MediaWiki 1.4 or previous.
                        // Text is embedded in this row in classic compression format.
                        return Revision::getRevisionText( $row, 'ar_' );
                }

                // New-style: keyed to the text storage backend.
                $dbr = wfGetDB( DB_REPLICA );
                $text = $dbr->selectRow( 'text',
                        [ 'old_text', 'old_flags' ],
                        [ 'old_id' => $row->ar_text_id ],
                        __METHOD__ );

                return Revision::getRevisionText( $text );
        }

        /**
         * Fetch (and decompress if necessary) the stored text of the most
         * recently edited deleted revision of the page.
         *
         * If there are no archived revisions for the page, returns NULL.
         *
         * @return string|null
         */
        function getLastRevisionText() {
                $dbr = wfGetDB( DB_REPLICA );
                $row = $dbr->selectRow( 'archive',
                        [ 'ar_text', 'ar_flags', 'ar_text_id' ],
                        [ 'ar_namespace' => $this->title->getNamespace(),
                                'ar_title' => $this->title->getDBkey() ],
                        __METHOD__,
                        [ 'ORDER BY' => 'ar_timestamp DESC' ] );

                if ( $row ) {
                        return $this->getTextFromRow( $row );
                }

                return null;
        }

        /**
         * Quick check if any archived revisions are present for the page.
         *
         * @return bool
         */
        function isDeleted() {
                $dbr = wfGetDB( DB_REPLICA );
                $n = $dbr->selectField( 'archive', 'COUNT(ar_title)',
                        [ 'ar_namespace' => $this->title->getNamespace(),
                                'ar_title' => $this->title->getDBkey() ],
                        __METHOD__
                );

                return ( $n > 0 );
        }

        /**
         * Restore the given (or all) text and file revisions for the page.
         * Once restored, the items will be removed from the archive tables.
         * The deletion log will be updated with an undeletion notice.
         *
         * This also sets Status objects, $this->fileStatus and $this->revisionStatus
         * (depending what operations are attempted).
         *
         * @param array $timestamps Pass an empty array to restore all revisions,
         *   otherwise list the ones to undelete.
         * @param string $comment
         * @param array $fileVersions
         * @param bool $unsuppress
         * @param User $user User performing the action, or null to use $wgUser
         * @param string|string[] $tags Change tags to add to log entry
         *   ($user should be able to add the specified tags before this is called)
         * @return array(number of file revisions restored, number of image revisions
         *   restored, log message) on success, false on failure.
         */
        function undelete( $timestamps, $comment = '', $fileVersions = [],
                $unsuppress = false, User $user = null, $tags = null
        ) {
                // If both the set of text revisions and file revisions are empty,
                // restore everything. Otherwise, just restore the requested items.
                $restoreAll = empty( $timestamps ) && empty( $fileVersions );

                $restoreText = $restoreAll || !empty( $timestamps );
                $restoreFiles = $restoreAll || !empty( $fileVersions );

                if ( $restoreFiles && $this->title->getNamespace() == NS_FILE ) {
                        $img = wfLocalFile( $this->title );
                        $img->load( File::READ_LATEST );
                        $this->fileStatus = $img->restore( $fileVersions, $unsuppress );
                        if ( !$this->fileStatus->isOK() ) {
                                return false;
                        }
                        $filesRestored = $this->fileStatus->successCount;
                } else {
                        $filesRestored = 0;
                }

                if ( $restoreText ) {
                        $this->revisionStatus = $this->undeleteRevisions( $timestamps, $unsuppress, $comment );
                        if ( !$this->revisionStatus->isOK() ) {
                                return false;
                        }

                        $textRestored = $this->revisionStatus->getValue();
                } else {
                        $textRestored = 0;
                }

                // Touch the log!

                if ( $textRestored && $filesRestored ) {
                        $reason = wfMessage( 'undeletedrevisions-files' )
                                ->numParams( $textRestored, $filesRestored )->inContentLanguage()->text();
                } elseif ( $textRestored ) {
                        $reason = wfMessage( 'undeletedrevisions' )->numParams( $textRestored )
                                ->inContentLanguage()->text();
                } elseif ( $filesRestored ) {
                        $reason = wfMessage( 'undeletedfiles' )->numParams( $filesRestored )
                                ->inContentLanguage()->text();
                } else {
                        wfDebug( "Undelete: nothing undeleted...\n" );

                        return false;
                }

                if ( trim( $comment ) != '' ) {
                        $reason .= wfMessage( 'colon-separator' )->inContentLanguage()->text() . $comment;
                }

                if ( $user === null ) {
                        global $wgUser;
                        $user = $wgUser;
                }

                $logEntry = new ManualLogEntry( 'delete', 'restore' );
                $logEntry->setPerformer( $user );
                $logEntry->setTarget( $this->title );
                $logEntry->setComment( $reason );
                $logEntry->setTags( $tags );

                Hooks::run( 'ArticleUndeleteLogEntry', [ $this, &$logEntry, $user ] );

                $logid = $logEntry->insert();
                $logEntry->publish( $logid );

                return [ $textRestored, $filesRestored, $reason ];
        }

        /**
         * This is the meaty bit -- It restores archived revisions of the given page
         * to the revision table.
         *
         * @param array $timestamps Pass an empty array to restore all revisions,
         *   otherwise list the ones to undelete.
         * @param bool $unsuppress Remove all ar_deleted/fa_deleted restrictions of seletected revs
         * @param string $comment
         * @throws ReadOnlyError
         * @return Status Status object containing the number of revisions restored on success
         */
        private function undeleteRevisions( $timestamps, $unsuppress = false, $comment = '' ) {
                if ( wfReadOnly() ) {
                        throw new ReadOnlyError();
                }

                $dbw = wfGetDB( DB_MASTER );
                $dbw->startAtomic( __METHOD__ );

                $restoreAll = empty( $timestamps );

                # Does this page already exist? We'll have to update it...
                $article = WikiPage::factory( $this->title );
                # Load latest data for the current page (bug 31179)
                $article->loadPageData( 'fromdbmaster' );
                $oldcountable = $article->isCountable();

                $page = $dbw->selectRow( 'page',
                        [ 'page_id', 'page_latest' ],
                        [ 'page_namespace' => $this->title->getNamespace(),
                                'page_title' => $this->title->getDBkey() ],
                        __METHOD__,
                        [ 'FOR UPDATE' ] // lock page
                );

                if ( $page ) {
                        $makepage = false;
                        # Page already exists. Import the history, and if necessary
                        # we'll update the latest revision field in the record.

                        # Get the time span of this page
                        $previousTimestamp = $dbw->selectField( 'revision', 'rev_timestamp',
                                [ 'rev_id' => $page->page_latest ],
                                __METHOD__ );

                        if ( $previousTimestamp === false ) {
                                wfDebug( __METHOD__ . ": existing page refers to a page_latest that does not exist\n" );

                                $status = Status::newGood( 0 );
                                $status->warning( 'undeleterevision-missing' );
                                $dbw->endAtomic( __METHOD__ );

                                return $status;
                        }
                } else {
                        # Have to create a new article...
                        $makepage = true;
                        $previousTimestamp = 0;
                }

                $oldWhere = [
                        'ar_namespace' => $this->title->getNamespace(),
                        'ar_title' => $this->title->getDBkey(),
                ];
                if ( !$restoreAll ) {
                        $oldWhere['ar_timestamp'] = array_map( [ &$dbw, 'timestamp' ], $timestamps );
                }

                $fields = [
                        'ar_id',
                        'ar_rev_id',
                        'rev_id',
                        'ar_text',
                        'ar_comment',
                        'ar_user',
                        'ar_user_text',
                        'ar_timestamp',
                        'ar_minor_edit',
                        'ar_flags',
                        'ar_text_id',
                        'ar_deleted',
                        'ar_page_id',
                        'ar_len',
                        'ar_sha1'
                ];

                if ( $this->config->get( 'ContentHandlerUseDB' ) ) {
                        $fields[] = 'ar_content_format';
                        $fields[] = 'ar_content_model';
                }

                /**
                 * Select each archived revision...
                 */
                $result = $dbw->select(
                        [ 'archive', 'revision' ],
                        $fields,
                        $oldWhere,
                        __METHOD__,
                        /* options */
                        [ 'ORDER BY' => 'ar_timestamp' ],
                        [ 'revision' => [ 'LEFT JOIN', 'ar_rev_id=rev_id' ] ]
                );

                $rev_count = $result->numRows();
                if ( !$rev_count ) {
                        wfDebug( __METHOD__ . ": no revisions to restore\n" );

                        $status = Status::newGood( 0 );
                        $status->warning( "undelete-no-results" );
                        $dbw->endAtomic( __METHOD__ );

                        return $status;
                }

                // We use ar_id because there can be duplicate ar_rev_id even for the same
                // page.  In this case, we may be able to restore the first one.
                $restoreFailedArIds = [];

                // Map rev_id to the ar_id that is allowed to use it.  When checking later,
                // if it doesn't match, the current ar_id can not be restored.

                // Value can be an ar_id or -1 (-1 means no ar_id can use it, since the
                // rev_id is taken before we even start the restore).
                $allowedRevIdToArIdMap = [];

                $latestRestorableRow = null;

                foreach ( $result as $row ) {
                        if ( $row->ar_rev_id ) {
                                // rev_id is taken even before we start restoring.
                                if ( $row->ar_rev_id === $row->rev_id ) {
                                        $restoreFailedArIds[] = $row->ar_id;
                                        $allowedRevIdToArIdMap[$row->ar_rev_id] = -1;
                                } else {
                                        // rev_id is not taken yet in the DB, but it might be taken
                                        // by a prior revision in the same restore operation. If
                                        // not, we need to reserve it.
                                        if ( isset( $allowedRevIdToArIdMap[$row->ar_rev_id] ) ) {
                                                $restoreFailedArIds[] = $row->ar_id;
                                        } else {
                                                $allowedRevIdToArIdMap[$row->ar_rev_id] = $row->ar_id;
                                                $latestRestorableRow = $row;
                                        }
                                }
                        } else {
                                // If ar_rev_id is null, there can't be a collision, and a
                                // rev_id will be chosen automatically.
                                $latestRestorableRow = $row;
                        }
                }

                $result->seek( 0 ); // move back

                $oldPageId = 0;
                if ( $latestRestorableRow !== null ) {
                        $oldPageId = (int)$latestRestorableRow->ar_page_id; // pass this to ArticleUndelete hook

                        // grab the content to check consistency with global state before restoring the page.
                        $revision = Revision::newFromArchiveRow( $latestRestorableRow,
                                [
                                        'title' => $article->getTitle(), // used to derive default content model
                                ]
                        );
                        $user = User::newFromName( $revision->getUserText( Revision::RAW ), false );
                        $content = $revision->getContent( Revision::RAW );

                        // NOTE: article ID may not be known yet. prepareSave() should not modify the database.
                        $status = $content->prepareSave( $article, 0, -1, $user );
                        if ( !$status->isOK() ) {
                                $dbw->endAtomic( __METHOD__ );

                                return $status;
                        }
                }

                $newid = false; // newly created page ID
                $restored = 0; // number of revisions restored
                /** @var Revision $revision */
                $revision = null;

                // If there are no restorable revisions, we can skip most of the steps.
                if ( $latestRestorableRow === null ) {
                        $failedRevisionCount = $rev_count;
                } else {
                        if ( $makepage ) {
                                // Check the state of the newest to-be version...
                                if ( !$unsuppress
                                        && ( $latestRestorableRow->ar_deleted & Revision::DELETED_TEXT )
                                ) {
                                        $dbw->endAtomic( __METHOD__ );

                                        return Status::newFatal( "undeleterevdel" );
                                }
                                // Safe to insert now...
                                $newid = $article->insertOn( $dbw, $latestRestorableRow->ar_page_id );
                                if ( $newid === false ) {
                                        // The old ID is reserved; let's pick another
                                        $newid = $article->insertOn( $dbw );
                                }
                                $pageId = $newid;
                        } else {
                                // Check if a deleted revision will become the current revision...
                                if ( $latestRestorableRow->ar_timestamp > $previousTimestamp ) {
                                        // Check the state of the newest to-be version...
                                        if ( !$unsuppress
                                                && ( $latestRestorableRow->ar_deleted & Revision::DELETED_TEXT )
                                        ) {
                                                $dbw->endAtomic( __METHOD__ );

                                                return Status::newFatal( "undeleterevdel" );
                                        }
                                }

                                $newid = false;
                                $pageId = $article->getId();
                        }

                        foreach ( $result as $row ) {
                                // Check for key dupes due to needed archive integrity.
                                if ( $row->ar_rev_id && $allowedRevIdToArIdMap[$row->ar_rev_id] !== $row->ar_id ) {
                                        continue;
                                }
                                // Insert one revision at a time...maintaining deletion status
                                // unless we are specifically removing all restrictions...
                                $revision = Revision::newFromArchiveRow( $row,
                                        [
                                                'page' => $pageId,
                                                'title' => $this->title,
                                                'deleted' => $unsuppress ? 0 : $row->ar_deleted
                                        ] );

                                $revision->insertOn( $dbw );
                                $restored++;

                                Hooks::run( 'ArticleRevisionUndeleted',
                                        [ &$this->title, $revision, $row->ar_page_id ] );
                        }

                        // Now that it's safely stored, take it out of the archive
                        // Don't delete rows that we failed to restore
                        $toDeleteConds = $oldWhere;
                        $failedRevisionCount = count( $restoreFailedArIds );
                        if ( $failedRevisionCount > 0 ) {
                                $toDeleteConds[] = 'ar_id NOT IN ( ' . $dbw->makeList( $restoreFailedArIds ) . ' )';
                        }

                        $dbw->delete( 'archive',
                                $toDeleteConds,
                                __METHOD__ );
                }

                $status = Status::newGood( $restored );

                if ( $failedRevisionCount > 0 ) {
                        $status->warning(
                                wfMessage( 'undeleterevision-duplicate-revid', $failedRevisionCount ) );
                }

                // Was anything restored at all?
                if ( $restored ) {
                        $created = (bool)$newid;
                        // Attach the latest revision to the page...
                        $wasnew = $article->updateIfNewerOn( $dbw, $revision );
                        if ( $created || $wasnew ) {
                                // Update site stats, link tables, etc
                                $article->doEditUpdates(
                                        $revision,
                                        User::newFromName( $revision->getUserText( Revision::RAW ), false ),
                                        [
                                                'created' => $created,
                                                'oldcountable' => $oldcountable,
                                                'restored' => true
                                        ]
                                );
                        }

                        Hooks::run( 'ArticleUndelete', [ &$this->title, $created, $comment, $oldPageId ] );
                        if ( $this->title->getNamespace() == NS_FILE ) {
                                DeferredUpdates::addUpdate( new HTMLCacheUpdate( $this->title, 'imagelinks' ) );
                        }
                }

                $dbw->endAtomic( __METHOD__ );

                return $status;
        }

        /**
         * @return Status
         */
        function getFileStatus() {
                return $this->fileStatus;
        }

        /**
         * @return Status
         */
        function getRevisionStatus() {
                return $this->revisionStatus;
        }
}

/**
 * Special page allowing users with the appropriate permissions to view
 * and restore deleted content.
 *
 * @ingroup SpecialPage
 */
class SpecialUndelete extends SpecialPage {
        private $mAction;
        private $mTarget;
        private $mTimestamp;
        private $mRestore;
        private $mRevdel;
        private $mInvert;
        private $mFilename;
        private $mTargetTimestamp;
        private $mAllowed;
        private $mCanView;
        private $mComment;
        private $mToken;

        /** @var Title */
        private $mTargetObj;

        function __construct() {
                parent::__construct( 'Undelete', 'deletedhistory' );
        }

        public function doesWrites() {
                return true;
        }

        function loadRequest( $par ) {
                $request = $this->getRequest();
                $user = $this->getUser();

                $this->mAction = $request->getVal( 'action' );
                if ( $par !== null && $par !== '' ) {
                        $this->mTarget = $par;
                } else {
                        $this->mTarget = $request->getVal( 'target' );
                }

                $this->mTargetObj = null;

                if ( $this->mTarget !== null && $this->mTarget !== '' ) {
                        $this->mTargetObj = Title::newFromText( $this->mTarget );
                }

                $this->mSearchPrefix = $request->getText( 'prefix' );
                $time = $request->getVal( 'timestamp' );
                $this->mTimestamp = $time ? wfTimestamp( TS_MW, $time ) : '';
                $this->mFilename = $request->getVal( 'file' );

                $posted = $request->wasPosted() &&
                        $user->matchEditToken( $request->getVal( 'wpEditToken' ) );
                $this->mRestore = $request->getCheck( 'restore' ) && $posted;
                $this->mRevdel = $request->getCheck( 'revdel' ) && $posted;
                $this->mInvert = $request->getCheck( 'invert' ) && $posted;
                $this->mPreview = $request->getCheck( 'preview' ) && $posted;
                $this->mDiff = $request->getCheck( 'diff' );
                $this->mDiffOnly = $request->getBool( 'diffonly', $this->getUser()->getOption( 'diffonly' ) );
                $this->mComment = $request->getText( 'wpComment' );
                $this->mUnsuppress = $request->getVal( 'wpUnsuppress' ) && $user->isAllowed( 'suppressrevision' );
                $this->mToken = $request->getVal( 'token' );

                if ( $this->isAllowed( 'undelete' ) && !$user->isBlocked() ) {
                        $this->mAllowed = true; // user can restore
                        $this->mCanView = true; // user can view content
                } elseif ( $this->isAllowed( 'deletedtext' ) ) {
                        $this->mAllowed = false; // user cannot restore
                        $this->mCanView = true; // user can view content
                        $this->mRestore = false;
                } else { // user can only view the list of revisions
                        $this->mAllowed = false;
                        $this->mCanView = false;
                        $this->mTimestamp = '';
                        $this->mRestore = false;
                }

                if ( $this->mRestore || $this->mInvert ) {
                        $timestamps = [];
                        $this->mFileVersions = [];
                        foreach ( $request->getValues() as $key => $val ) {
                                $matches = [];
                                if ( preg_match( '/^ts(\d{14})$/', $key, $matches ) ) {
                                        array_push( $timestamps, $matches[1] );
                                }

                                if ( preg_match( '/^fileid(\d+)$/', $key, $matches ) ) {
                                        $this->mFileVersions[] = intval( $matches[1] );
                                }
                        }
                        rsort( $timestamps );
                        $this->mTargetTimestamp = $timestamps;
                }
        }

        /**
         * Checks whether a user is allowed the permission for the
         * specific title if one is set.
         *
         * @param string $permission
         * @param User $user
         * @return bool
         */
        protected function isAllowed( $permission, User $user = null ) {
                $user = $user ?: $this->getUser();
                if ( $this->mTargetObj !== null ) {
                        return $this->mTargetObj->userCan( $permission, $user );
                } else {
                        return $user->isAllowed( $permission );
                }
        }

        function userCanExecute( User $user ) {
                return $this->isAllowed( $this->mRestriction, $user );
        }

        function execute( $par ) {
                $this->useTransactionalTimeLimit();

                $user = $this->getUser();

                $this->setHeaders();
                $this->outputHeader();

                $this->loadRequest( $par );
                $this->checkPermissions(); // Needs to be after mTargetObj is set

                $out = $this->getOutput();

                if ( is_null( $this->mTargetObj ) ) {
                        $out->addWikiMsg( 'undelete-header' );

                        # Not all users can just browse every deleted page from the list
                        if ( $user->isAllowed( 'browsearchive' ) ) {
                                $this->showSearchForm();
                        }

                        return;
                }

                $this->addHelpLink( 'Help:Undelete' );
                if ( $this->mAllowed ) {
                        $out->setPageTitle( $this->msg( 'undeletepage' ) );
                } else {
                        $out->setPageTitle( $this->msg( 'viewdeletedpage' ) );
                }

                $this->getSkin()->setRelevantTitle( $this->mTargetObj );

                if ( $this->mTimestamp !== '' ) {
                        $this->showRevision( $this->mTimestamp );
                } elseif ( $this->mFilename !== null && $this->mTargetObj->inNamespace( NS_FILE ) ) {
                        $file = new ArchivedFile( $this->mTargetObj, '', $this->mFilename );
                        // Check if user is allowed to see this file
                        if ( !$file->exists() ) {
                                $out->addWikiMsg( 'filedelete-nofile', $this->mFilename );
                        } elseif ( !$file->userCan( File::DELETED_FILE, $user ) ) {
                                if ( $file->isDeleted( File::DELETED_RESTRICTED ) ) {
                                        throw new PermissionsError( 'suppressrevision' );
                                } else {
                                        throw new PermissionsError( 'deletedtext' );
                                }
                        } elseif ( !$user->matchEditToken( $this->mToken, $this->mFilename ) ) {
                                $this->showFileConfirmationForm( $this->mFilename );
                        } else {
                                $this->showFile( $this->mFilename );
                        }
                } elseif ( $this->mAction === "submit" ) {
                        if ( $this->mRestore ) {
                                $this->undelete();
                        } elseif ( $this->mRevdel ) {
                                $this->redirectToRevDel();
                        }

                } else {
                        $this->showHistory();
                }
        }

        /**
         * Convert submitted form data to format expected by RevisionDelete and
         * redirect the request
         */
        private function redirectToRevDel() {
                $archive = new PageArchive( $this->mTargetObj );

                $revisions = [];

                foreach ( $this->getRequest()->getValues() as $key => $val ) {
                        $matches = [];
                        if ( preg_match( "/^ts(\d{14})$/", $key, $matches ) ) {
                                $revisions[ $archive->getRevision( $matches[1] )->getId() ] = 1;
                        }
                }
                $query = [
                        "type" => "revision",
                        "ids" => $revisions,
                        "target" => $this->mTargetObj->getPrefixedText()
                ];
                $url = SpecialPage::getTitleFor( 'Revisiondelete' )->getFullURL( $query );
                $this->getOutput()->redirect( $url );
        }

        function showSearchForm() {
                $out = $this->getOutput();
                $out->setPageTitle( $this->msg( 'undelete-search-title' ) );
                $out->addHTML(
                        Xml::openElement( 'form', [ 'method' => 'get', 'action' => wfScript() ] ) .
                                Xml::fieldset( $this->msg( 'undelete-search-box' )->text() ) .
                                Html::hidden( 'title', $this->getPageTitle()->getPrefixedDBkey() ) .
                                Html::rawElement(
                                        'label',
                                        [ 'for' => 'prefix' ],
                                        $this->msg( 'undelete-search-prefix' )->parse()
                                ) .
                                Xml::input(
                                        'prefix',
                                        20,
                                        $this->mSearchPrefix,
                                        [ 'id' => 'prefix', 'autofocus' => '' ]
                                ) . ' ' .
                                Xml::submitButton( $this->msg( 'undelete-search-submit' )->text() ) .
                                Xml::closeElement( 'fieldset' ) .
                                Xml::closeElement( 'form' )
                );

                # List undeletable articles
                if ( $this->mSearchPrefix ) {
                        $result = PageArchive::listPagesByPrefix( $this->mSearchPrefix );
                        $this->showList( $result );
                }
        }

        /**
         * Generic list of deleted pages
         *
         * @param ResultWrapper $result
         * @return bool
         */
        private function showList( $result ) {
                $out = $this->getOutput();

                if ( $result->numRows() == 0 ) {
                        $out->addWikiMsg( 'undelete-no-results' );

                        return false;
                }

                $out->addWikiMsg( 'undeletepagetext', $this->getLanguage()->formatNum( $result->numRows() ) );

                $undelete = $this->getPageTitle();
                $out->addHTML( "<ul>\n" );
                foreach ( $result as $row ) {
                        $title = Title::makeTitleSafe( $row->ar_namespace, $row->ar_title );
                        if ( $title !== null ) {
                                $item = Linker::linkKnown(
                                        $undelete,
                                        htmlspecialchars( $title->getPrefixedText() ),
                                        [],
                                        [ 'target' => $title->getPrefixedText() ]
                                );
                        } else {
                                // The title is no longer valid, show as text
                                $item = Html::element(
                                        'span',
                                        [ 'class' => 'mw-invalidtitle' ],
                                        Linker::getInvalidTitleDescription(
                                                $this->getContext(),
                                                $row->ar_namespace,
                                                $row->ar_title
                                        )
                                );
                        }
                        $revs = $this->msg( 'undeleterevisions' )->numParams( $row->count )->parse();
                        $out->addHTML( "<li>{$item} ({$revs})</li>\n" );
                }
                $result->free();
                $out->addHTML( "</ul>\n" );

                return true;
        }

        private function showRevision( $timestamp ) {
                if ( !preg_match( '/[0-9]{14}/', $timestamp ) ) {
                        return;
                }

                $archive = new PageArchive( $this->mTargetObj, $this->getConfig() );
                if ( !Hooks::run( 'UndeleteForm::showRevision', [ &$archive, $this->mTargetObj ] ) ) {
                        return;
                }
                $rev = $archive->getRevision( $timestamp );

                $out = $this->getOutput();
                $user = $this->getUser();

                if ( !$rev ) {
                        $out->addWikiMsg( 'undeleterevision-missing' );

                        return;
                }

                if ( $rev->isDeleted( Revision::DELETED_TEXT ) ) {
                        if ( !$rev->userCan( Revision::DELETED_TEXT, $user ) ) {
                                $out->wrapWikiMsg(
                                        "<div class='mw-warning plainlinks'>\n$1\n</div>\n",
                                $rev->isDeleted( Revision::DELETED_RESTRICTED ) ?
                                        'rev-suppressed-text-permission' : 'rev-deleted-text-permission'
                                );

                                return;
                        }

                        $out->wrapWikiMsg(
                                "<div class='mw-warning plainlinks'>\n$1\n</div>\n",
                                $rev->isDeleted( Revision::DELETED_RESTRICTED ) ?
                                        'rev-suppressed-text-view' : 'rev-deleted-text-view'
                        );
                        $out->addHTML( '<br />' );
                        // and we are allowed to see...
                }

                if ( $this->mDiff ) {
                        $previousRev = $archive->getPreviousRevision( $timestamp );
                        if ( $previousRev ) {
                                $this->showDiff( $previousRev, $rev );
                                if ( $this->mDiffOnly ) {
                                        return;
                                }

                                $out->addHTML( '<hr />' );
                        } else {
                                $out->addWikiMsg( 'undelete-nodiff' );
                        }
                }

                $link = Linker::linkKnown(
                        $this->getPageTitle( $this->mTargetObj->getPrefixedDBkey() ),
                        htmlspecialchars( $this->mTargetObj->getPrefixedText() )
                );

                $lang = $this->getLanguage();

                // date and time are separate parameters to facilitate localisation.
                // $time is kept for backward compat reasons.
                $time = $lang->userTimeAndDate( $timestamp, $user );
                $d = $lang->userDate( $timestamp, $user );
                $t = $lang->userTime( $timestamp, $user );
                $userLink = Linker::revUserTools( $rev );

                $content = $rev->getContent( Revision::FOR_THIS_USER, $user );

                $isText = ( $content instanceof TextContent );

                if ( $this->mPreview || $isText ) {
                        $openDiv = '<div id="mw-undelete-revision" class="mw-warning">';
                } else {
                        $openDiv = '<div id="mw-undelete-revision">';
                }
                $out->addHTML( $openDiv );

                // Revision delete links
                if ( !$this->mDiff ) {
                        $revdel = Linker::getRevDeleteLink( $user, $rev, $this->mTargetObj );
                        if ( $revdel ) {
                                $out->addHTML( "$revdel " );
                        }
                }

                $out->addHTML( $this->msg( 'undelete-revision' )->rawParams( $link )->params(
                        $time )->rawParams( $userLink )->params( $d, $t )->parse() . '</div>' );

                if ( !Hooks::run( 'UndeleteShowRevision', [ $this->mTargetObj, $rev ] ) ) {
                        return;
                }

                if ( ( $this->mPreview || !$isText ) && $content ) {
                        // NOTE: non-text content has no source view, so always use rendered preview

                        // Hide [edit]s
                        $popts = $out->parserOptions();
                        $popts->setEditSection( false );

                        $pout = $content->getParserOutput( $this->mTargetObj, $rev->getId(), $popts, true );
                        $out->addParserOutput( $pout );
                }

                if ( $isText ) {
                        // source view for textual content
                        $sourceView = Xml::element(
                                'textarea',
                                [
                                        'readonly' => 'readonly',
                                        'cols' => $user->getIntOption( 'cols' ),
                                        'rows' => $user->getIntOption( 'rows' )
                                ],
                                $content->getNativeData() . "\n"
                        );

                        $previewButton = Xml::element( 'input', [
                                'type' => 'submit',
                                'name' => 'preview',
                                'value' => $this->msg( 'showpreview' )->text()
                        ] );
                } else {
                        $sourceView = '';
                        $previewButton = '';
                }

                $diffButton = Xml::element( 'input', [
                        'name' => 'diff',
                        'type' => 'submit',
                        'value' => $this->msg( 'showdiff' )->text() ] );

                $out->addHTML(
                        $sourceView .
                                Xml::openElement( 'div', [
                                        'style' => 'clear: both' ] ) .
                                Xml::openElement( 'form', [
                                        'method' => 'post',
                                        'action' => $this->getPageTitle()->getLocalURL( [ 'action' => 'submit' ] ) ] ) .
                                Xml::element( 'input', [
                                        'type' => 'hidden',
                                        'name' => 'target',
                                        'value' => $this->mTargetObj->getPrefixedDBkey() ] ) .
                                Xml::element( 'input', [
                                        'type' => 'hidden',
                                        'name' => 'timestamp',
                                        'value' => $timestamp ] ) .
                                Xml::element( 'input', [
                                        'type' => 'hidden',
                                        'name' => 'wpEditToken',
                                        'value' => $user->getEditToken() ] ) .
                                $previewButton .
                                $diffButton .
                                Xml::closeElement( 'form' ) .
                                Xml::closeElement( 'div' )
                );
        }

        /**
         * Build a diff display between this and the previous either deleted
         * or non-deleted edit.
         *
         * @param Revision $previousRev
         * @param Revision $currentRev
         * @return string HTML
         */
        function showDiff( $previousRev, $currentRev ) {
                $diffContext = clone $this->getContext();
                $diffContext->setTitle( $currentRev->getTitle() );
                $diffContext->setWikiPage( WikiPage::factory( $currentRev->getTitle() ) );

                $diffEngine = $currentRev->getContentHandler()->createDifferenceEngine( $diffContext );
                $diffEngine->showDiffStyle();

                $formattedDiff = $diffEngine->generateContentDiffBody(
                        $previousRev->getContent( Revision::FOR_THIS_USER, $this->getUser() ),
                        $currentRev->getContent( Revision::FOR_THIS_USER, $this->getUser() )
                );

                $formattedDiff = $diffEngine->addHeader(
                        $formattedDiff,
                        $this->diffHeader( $previousRev, 'o' ),
                        $this->diffHeader( $currentRev, 'n' )
                );

                $this->getOutput()->addHTML( "<div>$formattedDiff</div>\n" );
        }

        /**
         * @param Revision $rev
         * @param string $prefix
         * @return string
         */
        private function diffHeader( $rev, $prefix ) {
                $isDeleted = !( $rev->getId() && $rev->getTitle() );
                if ( $isDeleted ) {
                        /// @todo FIXME: $rev->getTitle() is null for deleted revs...?
                        $targetPage = $this->getPageTitle();
                        $targetQuery = [
                                'target' => $this->mTargetObj->getPrefixedText(),
                                'timestamp' => wfTimestamp( TS_MW, $rev->getTimestamp() )
                        ];
                } else {
                        /// @todo FIXME: getId() may return non-zero for deleted revs...
                        $targetPage = $rev->getTitle();
                        $targetQuery = [ 'oldid' => $rev->getId() ];
                }

                // Add show/hide deletion links if available
                $user = $this->getUser();
                $lang = $this->getLanguage();
                $rdel = Linker::getRevDeleteLink( $user, $rev, $this->mTargetObj );

                if ( $rdel ) {
                        $rdel = " $rdel";
                }

                $minor = $rev->isMinor() ? ChangesList::flag( 'minor' ) : '';

                $tags = wfGetDB( DB_REPLICA )->selectField(
                        'tag_summary',
                        'ts_tags',
                        [ 'ts_rev_id' => $rev->getId() ],
                        __METHOD__
                );
                $tagSummary = ChangeTags::formatSummaryRow( $tags, 'deleteddiff', $this->getContext() );

                // FIXME This is reimplementing DifferenceEngine#getRevisionHeader
                // and partially #showDiffPage, but worse
                return '<div id="mw-diff-' . $prefix . 'title1"><strong>' .
                        Linker::link(
                                $targetPage,
                                $this->msg(
                                        'revisionasof',
                                        $lang->userTimeAndDate( $rev->getTimestamp(), $user ),
                                        $lang->userDate( $rev->getTimestamp(), $user ),
                                        $lang->userTime( $rev->getTimestamp(), $user )
                                )->escaped(),
                                [],
                                $targetQuery
                        ) .
                        '</strong></div>' .
                        '<div id="mw-diff-' . $prefix . 'title2">' .
                        Linker::revUserTools( $rev ) . '<br />' .
                        '</div>' .
                        '<div id="mw-diff-' . $prefix . 'title3">' .
                        $minor . Linker::revComment( $rev ) . $rdel . '<br />' .
                        '</div>' .
                        '<div id="mw-diff-' . $prefix . 'title5">' .
                        $tagSummary[0] . '<br />' .
                        '</div>';
        }

        /**
         * Show a form confirming whether a tokenless user really wants to see a file
         * @param string $key
         */
        private function showFileConfirmationForm( $key ) {
                $out = $this->getOutput();
                $lang = $this->getLanguage();
                $user = $this->getUser();
                $file = new ArchivedFile( $this->mTargetObj, '', $this->mFilename );
                $out->addWikiMsg( 'undelete-show-file-confirm',
                        $this->mTargetObj->getText(),
                        $lang->userDate( $file->getTimestamp(), $user ),
                        $lang->userTime( $file->getTimestamp(), $user ) );
                $out->addHTML(
                        Xml::openElement( 'form', [
                                        'method' => 'POST',
                                        'action' => $this->getPageTitle()->getLocalURL( [
                                                'target' => $this->mTarget,
                                                'file' => $key,
                                                'token' => $user->getEditToken( $key ),
                                        ] ),
                                ]
                        ) .
                                Xml::submitButton( $this->msg( 'undelete-show-file-submit' )->text() ) .
                                '</form>'
                );
        }

        /**
         * Show a deleted file version requested by the visitor.
         * @param string $key
         */
        private function showFile( $key ) {
                $this->getOutput()->disable();

                # We mustn't allow the output to be CDN cached, otherwise
                # if an admin previews a deleted image, and it's cached, then
                # a user without appropriate permissions can toddle off and
                # nab the image, and CDN will serve it
                $response = $this->getRequest()->response();
                $response->header( 'Expires: ' . gmdate( 'D, d M Y H:i:s', 0 ) . ' GMT' );
                $response->header( 'Cache-Control: no-cache, no-store, max-age=0, must-revalidate' );
                $response->header( 'Pragma: no-cache' );

                $repo = RepoGroup::singleton()->getLocalRepo();
                $path = $repo->getZonePath( 'deleted' ) . '/' . $repo->getDeletedHashPath( $key ) . $key;
                $repo->streamFile( $path );
        }

        protected function showHistory() {
                $this->checkReadOnly();

                $out = $this->getOutput();
                if ( $this->mAllowed ) {
                        $out->addModules( 'mediawiki.special.undelete' );
                }
                $out->wrapWikiMsg(
                        "<div class='mw-undelete-pagetitle'>\n$1\n</div>\n",
                        [ 'undeletepagetitle', wfEscapeWikiText( $this->mTargetObj->getPrefixedText() ) ]
                );

                $archive = new PageArchive( $this->mTargetObj, $this->getConfig() );
                Hooks::run( 'UndeleteForm::showHistory', [ &$archive, $this->mTargetObj ] );
                /*
                $text = $archive->getLastRevisionText();
                if( is_null( $text ) ) {
                        $out->addWikiMsg( 'nohistory' );
                        return;
                }
                */
                $out->addHTML( '<div class="mw-undelete-history">' );
                if ( $this->mAllowed ) {
                        $out->addWikiMsg( 'undeletehistory' );
                        $out->addWikiMsg( 'undeleterevdel' );
                } else {
                        $out->addWikiMsg( 'undeletehistorynoadmin' );
                }
                $out->addHTML( '</div>' );

                # List all stored revisions
                $revisions = $archive->listRevisions();
                $files = $archive->listFiles();

                $haveRevisions = $revisions && $revisions->numRows() > 0;
                $haveFiles = $files && $files->numRows() > 0;

                # Batch existence check on user and talk pages
                if ( $haveRevisions ) {
                        $batch = new LinkBatch();
                        foreach ( $revisions as $row ) {
                                $batch->addObj( Title::makeTitleSafe( NS_USER, $row->ar_user_text ) );
                                $batch->addObj( Title::makeTitleSafe( NS_USER_TALK, $row->ar_user_text ) );
                        }
                        $batch->execute();
                        $revisions->seek( 0 );
                }
                if ( $haveFiles ) {
                        $batch = new LinkBatch();
                        foreach ( $files as $row ) {
                                $batch->addObj( Title::makeTitleSafe( NS_USER, $row->fa_user_text ) );
                                $batch->addObj( Title::makeTitleSafe( NS_USER_TALK, $row->fa_user_text ) );
                        }
                        $batch->execute();
                        $files->seek( 0 );
                }

                if ( $this->mAllowed ) {
                        $action = $this->getPageTitle()->getLocalURL( [ 'action' => 'submit' ] );
                        # Start the form here
                        $top = Xml::openElement(
                                'form',
                                [ 'method' => 'post', 'action' => $action, 'id' => 'undelete' ]
                        );
                        $out->addHTML( $top );
                }

                # Show relevant lines from the deletion log:
                $deleteLogPage = new LogPage( 'delete' );
                $out->addHTML( Xml::element( 'h2', null, $deleteLogPage->getName()->text() ) . "\n" );
                LogEventsList::showLogExtract( $out, 'delete', $this->mTargetObj );
                # Show relevant lines from the suppression log:
                $suppressLogPage = new LogPage( 'suppress' );
                if ( $this->getUser()->isAllowed( 'suppressionlog' ) ) {
                        $out->addHTML( Xml::element( 'h2', null, $suppressLogPage->getName()->text() ) . "\n" );
                        LogEventsList::showLogExtract( $out, 'suppress', $this->mTargetObj );
                }

                if ( $this->mAllowed && ( $haveRevisions || $haveFiles ) ) {
                        # Format the user-visible controls (comment field, submission button)
                        # in a nice little table
                        if ( $this->getUser()->isAllowed( 'suppressrevision' ) ) {
                                $unsuppressBox =
                                        "<tr>
                                                <td>&#160;</td>
                                                <td class='mw-input'>" .
                                                Xml::checkLabel( $this->msg( 'revdelete-unsuppress' )->text(),
                                                        'wpUnsuppress', 'mw-undelete-unsuppress', $this->mUnsuppress ) .
                                                "</td>
                                        </tr>";
                        } else {
                                $unsuppressBox = '';
                        }

                        $table = Xml::fieldset( $this->msg( 'undelete-fieldset-title' )->text() ) .
                                Xml::openElement( 'table', [ 'id' => 'mw-undelete-table' ] ) .
                                "<tr>
                                        <td colspan='2' class='mw-undelete-extrahelp'>" .
                                $this->msg( 'undeleteextrahelp' )->parseAsBlock() .
                                "</td>
                        </tr>
                        <tr>
                                <td class='mw-label'>" .
                                Xml::label( $this->msg( 'undeletecomment' )->text(), 'wpComment' ) .
                                "</td>
                                <td class='mw-input'>" .
                                Xml::input(
                                        'wpComment',
                                        50,
                                        $this->mComment,
                                        [ 'id' => 'wpComment', 'autofocus' => '' ]
                                ) .
                                "</td>
                        </tr>
                        <tr>
                                <td>&#160;</td>
                                <td class='mw-submit'>" .
                                Xml::submitButton(
                                        $this->msg( 'undeletebtn' )->text(),
                                        [ 'name' => 'restore', 'id' => 'mw-undelete-submit' ]
                                ) . ' ' .
                                Xml::submitButton(
                                        $this->msg( 'undeleteinvert' )->text(),
                                        [ 'name' => 'invert', 'id' => 'mw-undelete-invert' ]
                                ) .
                                "</td>
                        </tr>" .
                                $unsuppressBox .
                                Xml::closeElement( 'table' ) .
                                Xml::closeElement( 'fieldset' );

                        $out->addHTML( $table );
                }

                $out->addHTML( Xml::element( 'h2', null, $this->msg( 'history' )->text() ) . "\n" );

                if ( $haveRevisions ) {
                        # Show the page's stored (deleted) history

                        if ( $this->getUser()->isAllowed( 'deleterevision' ) ) {
                                $out->addHTML( Html::element(
                                        'button',
                                        [
                                                'name' => 'revdel',
                                                'type' => 'submit',
                                                'class' => 'deleterevision-log-submit mw-log-deleterevision-button'
                                        ],
                                        $this->msg( 'showhideselectedversions' )->text()
                                ) . "\n" );
                        }

                        $out->addHTML( '<ul>' );
                        $remaining = $revisions->numRows();
                        $earliestLiveTime = $this->mTargetObj->getEarliestRevTime();

                        foreach ( $revisions as $row ) {
                                $remaining--;
                                $out->addHTML( $this->formatRevisionRow( $row, $earliestLiveTime, $remaining ) );
                        }
                        $revisions->free();
                        $out->addHTML( '</ul>' );
                } else {
                        $out->addWikiMsg( 'nohistory' );
                }

                if ( $haveFiles ) {
                        $out->addHTML( Xml::element( 'h2', null, $this->msg( 'filehist' )->text() ) . "\n" );
                        $out->addHTML( '<ul>' );
                        foreach ( $files as $row ) {
                                $out->addHTML( $this->formatFileRow( $row ) );
                        }
                        $files->free();
                        $out->addHTML( '</ul>' );
                }

                if ( $this->mAllowed ) {
                        # Slip in the hidden controls here
                        $misc = Html::hidden( 'target', $this->mTarget );
                        $misc .= Html::hidden( 'wpEditToken', $this->getUser()->getEditToken() );
                        $misc .= Xml::closeElement( 'form' );
                        $out->addHTML( $misc );
                }

                return true;
        }

        protected function formatRevisionRow( $row, $earliestLiveTime, $remaining ) {
                $rev = Revision::newFromArchiveRow( $row,
                        [
                                'title' => $this->mTargetObj
                        ] );

                $revTextSize = '';
                $ts = wfTimestamp( TS_MW, $row->ar_timestamp );
                // Build checkboxen...
                if ( $this->mAllowed ) {
                        if ( $this->mInvert ) {
                                if ( in_array( $ts, $this->mTargetTimestamp ) ) {
                                        $checkBox = Xml::check( "ts$ts" );
                                } else {
                                        $checkBox = Xml::check( "ts$ts", true );
                                }
                        } else {
                                $checkBox = Xml::check( "ts$ts" );
                        }
                } else {
                        $checkBox = '';
                }

                // Build page & diff links...
                $user = $this->getUser();
                if ( $this->mCanView ) {
                        $titleObj = $this->getPageTitle();
                        # Last link
                        if ( !$rev->userCan( Revision::DELETED_TEXT, $this->getUser() ) ) {
                                $pageLink = htmlspecialchars( $this->getLanguage()->userTimeAndDate( $ts, $user ) );
                                $last = $this->msg( 'diff' )->escaped();
                        } elseif ( $remaining > 0 || ( $earliestLiveTime && $ts > $earliestLiveTime ) ) {
                                $pageLink = $this->getPageLink( $rev, $titleObj, $ts );
                                $last = Linker::linkKnown(
                                        $titleObj,
                                        $this->msg( 'diff' )->escaped(),
                                        [],
                                        [
                                                'target' => $this->mTargetObj->getPrefixedText(),
                                                'timestamp' => $ts,
                                                'diff' => 'prev'
                                        ]
                                );
                        } else {
                                $pageLink = $this->getPageLink( $rev, $titleObj, $ts );
                                $last = $this->msg( 'diff' )->escaped();
                        }
                } else {
                        $pageLink = htmlspecialchars( $this->getLanguage()->userTimeAndDate( $ts, $user ) );
                        $last = $this->msg( 'diff' )->escaped();
                }

                // User links
                $userLink = Linker::revUserTools( $rev );

                // Minor edit
                $minor = $rev->isMinor() ? ChangesList::flag( 'minor' ) : '';

                // Revision text size
                $size = $row->ar_len;
                if ( !is_null( $size ) ) {
                        $revTextSize = Linker::formatRevisionSize( $size );
                }

                // Edit summary
                $comment = Linker::revComment( $rev );

                // Tags
                $attribs = [];
                list( $tagSummary, $classes ) = ChangeTags::formatSummaryRow(
                        $row->ts_tags,
                        'deletedhistory',
                        $this->getContext()
                );
                if ( $classes ) {
                        $attribs['class'] = implode( ' ', $classes );
                }

                $revisionRow = $this->msg( 'undelete-revision-row2' )
                        ->rawParams(
                                $checkBox,
                                $last,
                                $pageLink,
                                $userLink,
                                $minor,
                                $revTextSize,
                                $comment,
                                $tagSummary
                        )
                        ->escaped();

                return Xml::tags( 'li', $attribs, $revisionRow ) . "\n";
        }

        private function formatFileRow( $row ) {
                $file = ArchivedFile::newFromRow( $row );
                $ts = wfTimestamp( TS_MW, $row->fa_timestamp );
                $user = $this->getUser();

                $checkBox = '';
                if ( $this->mCanView && $row->fa_storage_key ) {
                        if ( $this->mAllowed ) {
                                $checkBox = Xml::check( 'fileid' . $row->fa_id );
                        }
                        $key = urlencode( $row->fa_storage_key );
                        $pageLink = $this->getFileLink( $file, $this->getPageTitle(), $ts, $key );
                } else {
                        $pageLink = $this->getLanguage()->userTimeAndDate( $ts, $user );
                }
                $userLink = $this->getFileUser( $file );
                $data = $this->msg( 'widthheight' )->numParams( $row->fa_width, $row->fa_height )->text();
                $bytes = $this->msg( 'parentheses' )
                        ->rawParams( $this->msg( 'nbytes' )->numParams( $row->fa_size )->text() )
                        ->plain();
                $data = htmlspecialchars( $data . ' ' . $bytes );
                $comment = $this->getFileComment( $file );

                // Add show/hide deletion links if available
                $canHide = $this->isAllowed( 'deleterevision' );
                if ( $canHide || ( $file->getVisibility() && $this->isAllowed( 'deletedhistory' ) ) ) {
                        if ( !$file->userCan( File::DELETED_RESTRICTED, $user ) ) {
                                // Revision was hidden from sysops
                                $revdlink = Linker::revDeleteLinkDisabled( $canHide );
                        } else {
                                $query = [
                                        'type' => 'filearchive',
                                        'target' => $this->mTargetObj->getPrefixedDBkey(),
                                        'ids' => $row->fa_id
                                ];
                                $revdlink = Linker::revDeleteLink( $query,
                                        $file->isDeleted( File::DELETED_RESTRICTED ), $canHide );
                        }
                } else {
                        $revdlink = '';
                }

                return "<li>$checkBox $revdlink $pageLink . . $userLink $data $comment</li>\n";
        }

        /**
         * Fetch revision text link if it's available to all users
         *
         * @param Revision $rev
         * @param Title $titleObj
         * @param string $ts Timestamp
         * @return string
         */
        function getPageLink( $rev, $titleObj, $ts ) {
                $user = $this->getUser();
                $time = $this->getLanguage()->userTimeAndDate( $ts, $user );

                if ( !$rev->userCan( Revision::DELETED_TEXT, $user ) ) {
                        return '<span class="history-deleted">' . $time . '</span>';
                }

                $link = Linker::linkKnown(
                        $titleObj,
                        htmlspecialchars( $time ),
                        [],
                        [
                                'target' => $this->mTargetObj->getPrefixedText(),
                                'timestamp' => $ts
                        ]
                );

                if ( $rev->isDeleted( Revision::DELETED_TEXT ) ) {
                        $link = '<span class="history-deleted">' . $link . '</span>';
                }

                return $link;
        }

        /**
         * Fetch image view link if it's available to all users
         *
         * @param File|ArchivedFile $file
         * @param Title $titleObj
         * @param string $ts A timestamp
         * @param string $key A storage key
         *
         * @return string HTML fragment
         */
        function getFileLink( $file, $titleObj, $ts, $key ) {
                $user = $this->getUser();
                $time = $this->getLanguage()->userTimeAndDate( $ts, $user );

                if ( !$file->userCan( File::DELETED_FILE, $user ) ) {
                        return '<span class="history-deleted">' . $time . '</span>';
                }

                $link = Linker::linkKnown(
                        $titleObj,
                        htmlspecialchars( $time ),
                        [],
                        [
                                'target' => $this->mTargetObj->getPrefixedText(),
                                'file' => $key,
                                'token' => $user->getEditToken( $key )
                        ]
                );

                if ( $file->isDeleted( File::DELETED_FILE ) ) {
                        $link = '<span class="history-deleted">' . $link . '</span>';
                }

                return $link;
        }

        /**
         * Fetch file's user id if it's available to this user
         *
         * @param File|ArchivedFile $file
         * @return string HTML fragment
         */
        function getFileUser( $file ) {
                if ( !$file->userCan( File::DELETED_USER, $this->getUser() ) ) {
                        return '<span class="history-deleted">' .
                                $this->msg( 'rev-deleted-user' )->escaped() .
                                '</span>';
                }

                $link = Linker::userLink( $file->getRawUser(), $file->getRawUserText() ) .
                        Linker::userToolLinks( $file->getRawUser(), $file->getRawUserText() );

                if ( $file->isDeleted( File::DELETED_USER ) ) {
                        $link = '<span class="history-deleted">' . $link . '</span>';
                }

                return $link;
        }

        /**
         * Fetch file upload comment if it's available to this user
         *
         * @param File|ArchivedFile $file
         * @return string HTML fragment
         */
        function getFileComment( $file ) {
                if ( !$file->userCan( File::DELETED_COMMENT, $this->getUser() ) ) {
                        return '<span class="history-deleted"><span class="comment">' .
                                $this->msg( 'rev-deleted-comment' )->escaped() . '</span></span>';
                }

                $link = Linker::commentBlock( $file->getRawDescription() );

                if ( $file->isDeleted( File::DELETED_COMMENT ) ) {
                        $link = '<span class="history-deleted">' . $link . '</span>';
                }

                return $link;
        }

        function undelete() {
                if ( $this->getConfig()->get( 'UploadMaintenance' )
                        && $this->mTargetObj->getNamespace() == NS_FILE
                ) {
                        throw new ErrorPageError( 'undelete-error', 'filedelete-maintenance' );
                }

                $this->checkReadOnly();

                $out = $this->getOutput();
                $archive = new PageArchive( $this->mTargetObj, $this->getConfig() );
                Hooks::run( 'UndeleteForm::undelete', [ &$archive, $this->mTargetObj ] );
                $ok = $archive->undelete(
                        $this->mTargetTimestamp,
                        $this->mComment,
                        $this->mFileVersions,
                        $this->mUnsuppress,
                        $this->getUser()
                );

                if ( is_array( $ok ) ) {
                        if ( $ok[1] ) { // Undeleted file count
                                Hooks::run( 'FileUndeleteComplete', [
                                        $this->mTargetObj, $this->mFileVersions,
                                        $this->getUser(), $this->mComment ] );
                        }

                        $link = Linker::linkKnown( $this->mTargetObj );
                        $out->addHTML( $this->msg( 'undeletedpage' )->rawParams( $link )->parse() );
                } else {
                        $out->setPageTitle( $this->msg( 'undelete-error' ) );
                }

                // Show revision undeletion warnings and errors
                $status = $archive->getRevisionStatus();
                if ( $status && !$status->isGood() ) {
                        $out->addWikiText( '<div class="error">' .
                                $status->getWikiText(
                                        'cannotundelete',
                                        'cannotundelete'
                                ) . '</div>'
                        );
                }

                // Show file undeletion warnings and errors
                $status = $archive->getFileStatus();
                if ( $status && !$status->isGood() ) {
                        $out->addWikiText( '<div class="error">' .
                                $status->getWikiText(
                                        'undelete-error-short',
                                        'undelete-error-long'
                                ) . '</div>'
                        );
                }
        }

        /**
         * Return an array of subpages beginning with $search that this special page will accept.
         *
         * @param string $search Prefix to search for
         * @param int $limit Maximum number of results to return (usually 10)
         * @param int $offset Number of results to skip (usually 0)
         * @return string[] Matching subpages
         */
        public function prefixSearchSubpages( $search, $limit, $offset ) {
                return $this->prefixSearchString( $search, $limit, $offset );
        }

        protected function getGroupName() {
                return 'pagetools';
        }
}