ChangeTags.php

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<?php
use MediaWiki\HookContainer\HookRunner;
use MediaWiki\Language\RawMessage;
use MediaWiki\MainConfigNames;
use MediaWiki\MediaWikiServices;
use MediaWiki\Permissions\Authority;
use MediaWiki\Storage\NameTableAccessException;
use MediaWiki\User\UserIdentity;
use Wikimedia\Rdbms\Database;
use Wikimedia\Rdbms\IDatabase;
use Wikimedia\Rdbms\SelectQueryBuilder;
 
class ChangeTags {
    public const TAG_CONTENT_MODEL_CHANGE = 'mw-contentmodelchange';
    public const TAG_NEW_REDIRECT = 'mw-new-redirect';
    public const TAG_REMOVED_REDIRECT = 'mw-removed-redirect';
    public const TAG_CHANGED_REDIRECT_TARGET = 'mw-changed-redirect-target';
    public const TAG_BLANK = 'mw-blank';
    public const TAG_REPLACE = 'mw-replace';
    public const TAG_ROLLBACK = 'mw-rollback';
    public const TAG_UNDO = 'mw-undo';
    public const TAG_MANUAL_REVERT = 'mw-manual-revert';
    public const TAG_REVERTED = 'mw-reverted';
    public const TAG_SERVER_SIDE_UPLOAD = 'mw-server-side-upload';
 
    public const REVERT_TAGS = [ self::TAG_ROLLBACK, self::TAG_UNDO, self::TAG_MANUAL_REVERT ];
 
    public const BYPASS_MAX_USAGE_CHECK = 1;
 
    private const MAX_DELETE_USES = 5000;
 
    private const DEFINED_SOFTWARE_TAGS = [
        'mw-contentmodelchange',
        'mw-new-redirect',
        'mw-removed-redirect',
        'mw-changed-redirect-target',
        'mw-blank',
        'mw-replace',
        'mw-rollback',
        'mw-undo',
        'mw-manual-revert',
        'mw-reverted',
        'mw-server-side-upload',
    ];
 
    private const CHANGE_TAG = 'change_tag';
 
    private const CHANGE_TAG_DEF = 'change_tag_def';
 
    public const DISPLAY_TABLE_ALIAS = 'changetagdisplay';
 
    public static $avoidReopeningTablesForTesting = false;
 
    public static function getSoftwareTags( $all = false ) {
        $coreTags = MediaWikiServices::getInstance()->getMainConfig()->get(
            MainConfigNames::SoftwareTags );
        $softwareTags = [];
 
        if ( !is_array( $coreTags ) ) {
            wfWarn( 'wgSoftwareTags should be associative array of enabled tags.
            Please refer to documentation for the list of tags you can enable' );
            return $softwareTags;
        }
 
        $availableSoftwareTags = !$all ?
            array_keys( array_filter( $coreTags ) ) :
            array_keys( $coreTags );
 
        $softwareTags = array_intersect(
            $availableSoftwareTags,
            self::DEFINED_SOFTWARE_TAGS
        );
 
        return $softwareTags;
    }
 
    public static function formatSummaryRow( $tags, $page, MessageLocalizer $localizer = null ) {
        if ( $tags === '' || $tags === null ) {
            return [ '', [] ];
        }
        if ( !$localizer ) {
            $localizer = RequestContext::getMain();
        }
 
        $classes = [];
 
        $tags = explode( ',', $tags );
        $order = array_flip( self::listDefinedTags() );
        usort( $tags, static function ( $a, $b ) use ( $order ) {
            return ( $order[ $a ] ?? INF ) <=> ( $order[ $b ] ?? INF );
        } );
 
        $displayTags = [];
        foreach ( $tags as $tag ) {
            if ( $tag === '' ) {
                continue;
            }
            $classes[] = Sanitizer::escapeClass( "mw-tag-$tag" );
            $description = self::tagDescription( $tag, $localizer );
            if ( $description === false ) {
                continue;
            }
            $displayTags[] = Xml::tags(
                'span',
                [ 'class' => 'mw-tag-marker ' .
                    Sanitizer::escapeClass( "mw-tag-marker-$tag" ) ],
                $description
            );
        }
 
        if ( !$displayTags ) {
            return [ '', $classes ];
        }
 
        $markers = $localizer->msg( 'tag-list-wrapper' )
            ->numParams( count( $displayTags ) )
            ->rawParams( implode( ' ', $displayTags ) )
            ->parse();
        $markers = Xml::tags( 'span', [ 'class' => 'mw-tag-markers' ], $markers );
 
        return [ $markers, $classes ];
    }
 
    public static function tagShortDescriptionMessage( $tag, MessageLocalizer $context ) {
        $msg = $context->msg( "tag-$tag" );
        if ( !$msg->exists() ) {
            // No such message
            // Pass through ->msg(), even though it seems redundant, to avoid requesting
            // the user's language from session-less entry points (T227233)
            return $context->msg( new RawMessage( '$1', [ Message::plaintextParam( $tag ) ] ) );
        }
        if ( $msg->isDisabled() ) {
            // The message exists but is disabled, hide the tag.
            return false;
        }
 
        // Message exists and isn't disabled, use it.
        return $msg;
    }
 
    public static function tagDescription( $tag, MessageLocalizer $context ) {
        $msg = self::tagShortDescriptionMessage( $tag, $context );
        return $msg ? $msg->parse() : false;
    }
 
    public static function tagLongDescriptionMessage( $tag, MessageLocalizer $context ) {
        $msg = $context->msg( "tag-$tag-description" );
        if ( !$msg->exists() ) {
            return false;
        }
        if ( $msg->isDisabled() ) {
            // The message exists but is disabled, hide the description.
            return false;
        }
 
        // Message exists and isn't disabled, use it.
        return $msg;
    }
 
    public static function addTags( $tags, $rc_id = null, $rev_id = null,
        $log_id = null, $params = null, RecentChange $rc = null
    ) {
        $result = self::updateTags( $tags, null, $rc_id, $rev_id, $log_id, $params, $rc );
        return (bool)$result[0];
    }
 
    public static function updateTags( $tagsToAdd, $tagsToRemove, &$rc_id = null,
        &$rev_id = null, &$log_id = null, $params = null, RecentChange $rc = null,
        UserIdentity $user = null
    ) {
        $tagsToAdd = array_filter(
            (array)$tagsToAdd, // Make sure we're submitting all tags...
            static function ( $value ) {
                return ( $value ?? '' ) !== '';
            }
        );
        $tagsToRemove = array_filter(
            (array)$tagsToRemove,
            static function ( $value ) {
                return ( $value ?? '' ) !== '';
            }
        );
 
        if ( !$rc_id && !$rev_id && !$log_id ) {
            throw new BadMethodCallException( 'At least one of: RCID, revision ID, and log ID MUST be ' .
                'specified when adding or removing a tag from a change!' );
        }
 
        $dbw = wfGetDB( DB_PRIMARY );
 
        // Might as well look for rcids and so on.
        if ( !$rc_id ) {
            // Info might be out of date, somewhat fractionally, on replica DB.
            // LogEntry/LogPage and WikiPage match rev/log/rc timestamps,
            // so use that relation to avoid full table scans.
            if ( $log_id ) {
                $rc_id = $dbw->newSelectQueryBuilder()
                    ->select( 'rc_id' )
                    ->from( 'logging' )
                    ->join( 'recentchanges', null, [
                        'rc_timestamp = log_timestamp',
                        'rc_logid = log_id'
                    ] )
                    ->where( [ 'log_id' => $log_id ] )
                    ->caller( __METHOD__ )
                    ->fetchField();
            } elseif ( $rev_id ) {
                $rc_id = $dbw->newSelectQueryBuilder()
                    ->select( 'rc_id' )
                    ->from( 'revision' )
                    ->join( 'recentchanges', null, [
                        'rc_this_oldid = rev_id'
                    ] )
                    ->where( [ 'rev_id' => $rev_id ] )
                    ->caller( __METHOD__ )
                    ->fetchField();
            }
        } elseif ( !$log_id && !$rev_id ) {
            // Info might be out of date, somewhat fractionally, on replica DB.
            $log_id = $dbw->newSelectQueryBuilder()
                ->select( 'rc_logid' )
                ->from( 'recentchanges' )
                ->where( [ 'rc_id' => $rc_id ] )
                ->caller( __METHOD__ )
                ->fetchField();
            $rev_id = $dbw->newSelectQueryBuilder()
                ->select( 'rc_this_oldid' )
                ->from( 'recentchanges' )
                ->where( [ 'rc_id' => $rc_id ] )
                ->caller( __METHOD__ )
                ->fetchField();
        }
 
        if ( $log_id && !$rev_id ) {
            $rev_id = $dbw->newSelectQueryBuilder()
                ->select( 'ls_value' )
                ->from( 'log_search' )
                ->where( [ 'ls_field' => 'associated_rev_id', 'ls_log_id' => $log_id ] )
                ->caller( __METHOD__ )
                ->fetchField();
        } elseif ( !$log_id && $rev_id ) {
            $log_id = $dbw->newSelectQueryBuilder()
                ->select( 'ls_log_id' )
                ->from( 'log_search' )
                ->where( [ 'ls_field' => 'associated_rev_id', 'ls_value' => (string)$rev_id ] )
                ->caller( __METHOD__ )
                ->fetchField();
        }
 
        $prevTags = self::getTags( $dbw, $rc_id, $rev_id, $log_id );
 
        // add tags
        $tagsToAdd = array_values( array_diff( $tagsToAdd, $prevTags ) );
        $newTags = array_unique( array_merge( $prevTags, $tagsToAdd ) );
 
        // remove tags
        $tagsToRemove = array_values( array_intersect( $tagsToRemove, $newTags ) );
        $newTags = array_values( array_diff( $newTags, $tagsToRemove ) );
 
        sort( $prevTags );
        sort( $newTags );
        if ( $prevTags == $newTags ) {
            return [ [], [], $prevTags ];
        }
 
        // insert a row into change_tag for each new tag
        $changeTagDefStore = MediaWikiServices::getInstance()->getChangeTagDefStore();
        if ( count( $tagsToAdd ) ) {
            $changeTagMapping = [];
            foreach ( $tagsToAdd as $tag ) {
                $changeTagMapping[$tag] = $changeTagDefStore->acquireId( $tag );
            }
            $fname = __METHOD__;
            // T207881: update the counts at the end of the transaction
            $dbw->onTransactionPreCommitOrIdle( static function () use ( $dbw, $tagsToAdd, $fname ) {
                $dbw->update(
                    self::CHANGE_TAG_DEF,
                    [ 'ctd_count = ctd_count + 1' ],
                    [ 'ctd_name' => $tagsToAdd ],
                    $fname
                );
            }, $fname );
 
            $tagsRows = [];
            foreach ( $tagsToAdd as $tag ) {
                // Filter so we don't insert NULLs as zero accidentally.
                // Keep in mind that $rc_id === null means "I don't care/know about the
                // rc_id, just delete $tag on this revision/log entry". It doesn't
                // mean "only delete tags on this revision/log WHERE rc_id IS NULL".
                $tagsRows[] = array_filter(
                    [
                        'ct_rc_id' => $rc_id,
                        'ct_log_id' => $log_id,
                        'ct_rev_id' => $rev_id,
                        'ct_params' => $params,
                        'ct_tag_id' => $changeTagMapping[$tag] ?? null,
                    ]
                );
 
            }
 
            $dbw->insert( self::CHANGE_TAG, $tagsRows, __METHOD__, [ 'IGNORE' ] );
        }
 
        // delete from change_tag
        if ( count( $tagsToRemove ) ) {
            $fname = __METHOD__;
            foreach ( $tagsToRemove as $tag ) {
                $conds = array_filter(
                    [
                        'ct_rc_id' => $rc_id,
                        'ct_log_id' => $log_id,
                        'ct_rev_id' => $rev_id,
                        'ct_tag_id' => $changeTagDefStore->getId( $tag ),
                    ]
                );
                $dbw->delete( self::CHANGE_TAG, $conds, __METHOD__ );
                if ( $dbw->affectedRows() ) {
                    // T207881: update the counts at the end of the transaction
                    $dbw->onTransactionPreCommitOrIdle( static function () use ( $dbw, $tag, $fname ) {
                        $dbw->update(
                            self::CHANGE_TAG_DEF,
                            [ 'ctd_count = ctd_count - 1' ],
                            [ 'ctd_name' => $tag ],
                            $fname
                        );
 
                        $dbw->delete(
                            self::CHANGE_TAG_DEF,
                            [ 'ctd_name' => $tag, 'ctd_count' => 0, 'ctd_user_defined' => 0 ],
                            $fname
                        );
                    }, $fname );
                }
            }
        }
 
        $userObj = $user ? MediaWikiServices::getInstance()->getUserFactory()->newFromUserIdentity( $user ) : null;
        Hooks::runner()->onChangeTagsAfterUpdateTags( $tagsToAdd, $tagsToRemove, $prevTags,
            $rc_id, $rev_id, $log_id, $params, $rc, $userObj );
 
        return [ $tagsToAdd, $tagsToRemove, $prevTags ];
    }
 
    public static function getTagsWithData(
        IDatabase $db, $rc_id = null, $rev_id = null, $log_id = null
    ) {
        if ( !$rc_id && !$rev_id && !$log_id ) {
            throw new BadMethodCallException( 'At least one of: RCID, revision ID, and log ID MUST be ' .
                'specified when loading tags from a change!' );
        }
 
        $conds = array_filter(
            [
                'ct_rc_id' => $rc_id,
                'ct_rev_id' => $rev_id,
                'ct_log_id' => $log_id,
            ]
        );
        $result = $db->newSelectQueryBuilder()
            ->select( [ 'ct_tag_id', 'ct_params' ] )
            ->from( self::CHANGE_TAG )
            ->where( $conds )
            ->caller( __METHOD__ )
            ->fetchResultSet();
 
        $tags = [];
        $changeTagDefStore = MediaWikiServices::getInstance()->getChangeTagDefStore();
        foreach ( $result as $row ) {
            $tagName = $changeTagDefStore->getName( (int)$row->ct_tag_id );
            $tags[$tagName] = $row->ct_params;
        }
 
        return $tags;
    }
 
    public static function getTags( IDatabase $db, $rc_id = null, $rev_id = null, $log_id = null ) {
        return array_keys( self::getTagsWithData( $db, $rc_id, $rev_id, $log_id ) );
    }
 
    protected static function restrictedTagError( $msgOne, $msgMulti, $tags ) {
        $lang = RequestContext::getMain()->getLanguage();
        $tags = array_values( $tags );
        $count = count( $tags );
        $status = Status::newFatal( ( $count > 1 ) ? $msgMulti : $msgOne,
            $lang->commaList( $tags ), $count );
        $status->value = $tags;
        return $status;
    }
 
    public static function canAddTagsAccompanyingChange(
        array $tags,
        Authority $performer = null,
        $checkBlock = true
    ) {
        $user = null;
        if ( $performer !== null ) {
            if ( !$performer->isAllowed( 'applychangetags' ) ) {
                return Status::newFatal( 'tags-apply-no-permission' );
            }
 
            if ( $checkBlock && $performer->getBlock() && $performer->getBlock()->isSitewide() ) {
                return Status::newFatal(
                    'tags-apply-blocked',
                    $performer->getUser()->getName()
                );
            }
 
            // ChangeTagsAllowedAdd hook still needs a full User object
            $user = MediaWikiServices::getInstance()->getUserFactory()->newFromAuthority( $performer );
        }
 
        // to be applied, a tag has to be explicitly defined
        $allowedTags = self::listExplicitlyDefinedTags();
        Hooks::runner()->onChangeTagsAllowedAdd( $allowedTags, $tags, $user );
        $disallowedTags = array_diff( $tags, $allowedTags );
        if ( $disallowedTags ) {
            return self::restrictedTagError( 'tags-apply-not-allowed-one',
                'tags-apply-not-allowed-multi', $disallowedTags );
        }
 
        return Status::newGood();
    }
 
    public static function addTagsAccompanyingChangeWithChecks(
        array $tags, $rc_id, $rev_id, $log_id, $params, Authority $performer
    ) {
        // are we allowed to do this?
        $result = self::canAddTagsAccompanyingChange( $tags, $performer );
        if ( !$result->isOK() ) {
            $result->value = null;
            return $result;
        }
 
        // do it!
        self::addTags( $tags, $rc_id, $rev_id, $log_id, $params );
 
        return Status::newGood( true );
    }
 
    public static function canUpdateTags(
        array $tagsToAdd,
        array $tagsToRemove,
        Authority $performer = null
    ) {
        if ( $performer !== null ) {
            if ( !$performer->isAllowed( 'changetags' ) ) {
                return Status::newFatal( 'tags-update-no-permission' );
            }
 
            if ( $performer->getBlock() && $performer->getBlock()->isSitewide() ) {
                return Status::newFatal(
                    'tags-update-blocked',
                    $performer->getUser()->getName()
                );
            }
        }
 
        if ( $tagsToAdd ) {
            // to be added, a tag has to be explicitly defined
            // @todo Allow extensions to define tags that can be applied by users...
            $explicitlyDefinedTags = self::listExplicitlyDefinedTags();
            $diff = array_diff( $tagsToAdd, $explicitlyDefinedTags );
            if ( $diff ) {
                return self::restrictedTagError( 'tags-update-add-not-allowed-one',
                    'tags-update-add-not-allowed-multi', $diff );
            }
        }
 
        if ( $tagsToRemove ) {
            // to be removed, a tag must not be defined by an extension, or equivalently it
            // has to be either explicitly defined or not defined at all
            // (assuming no edge case of a tag both explicitly-defined and extension-defined)
            $softwareDefinedTags = self::listSoftwareDefinedTags();
            $intersect = array_intersect( $tagsToRemove, $softwareDefinedTags );
            if ( $intersect ) {
                return self::restrictedTagError( 'tags-update-remove-not-allowed-one',
                    'tags-update-remove-not-allowed-multi', $intersect );
            }
        }
 
        return Status::newGood();
    }
 
    public static function updateTagsWithChecks( $tagsToAdd, $tagsToRemove,
        $rc_id, $rev_id, $log_id, $params, string $reason, Authority $performer
    ) {
        if ( !$tagsToAdd && !$tagsToRemove ) {
            // no-op, don't bother
            return Status::newGood( (object)[
                'logId' => null,
                'addedTags' => [],
                'removedTags' => [],
            ] );
        }
 
        $tagsToAdd ??= [];
        $tagsToRemove ??= [];
 
        // are we allowed to do this?
        $result = self::canUpdateTags( $tagsToAdd, $tagsToRemove, $performer );
        if ( !$result->isOK() ) {
            $result->value = null;
            return $result;
        }
 
        // basic rate limiting
        $user = MediaWikiServices::getInstance()->getUserFactory()->newFromAuthority( $performer );
        if ( $user->pingLimiter( 'changetag' ) ) {
            return Status::newFatal( 'actionthrottledtext' );
        }
 
        // do it!
        [ $tagsAdded, $tagsRemoved, $initialTags ] = self::updateTags( $tagsToAdd,
            $tagsToRemove, $rc_id, $rev_id, $log_id, $params, null, $user );
        if ( !$tagsAdded && !$tagsRemoved ) {
            // no-op, don't log it
            return Status::newGood( (object)[
                'logId' => null,
                'addedTags' => [],
                'removedTags' => [],
            ] );
        }
 
        // log it
        $logEntry = new ManualLogEntry( 'tag', 'update' );
        $logEntry->setPerformer( $performer->getUser() );
        $logEntry->setComment( $reason );
 
        // find the appropriate target page
        if ( $rev_id ) {
            $revisionRecord = MediaWikiServices::getInstance()
                ->getRevisionLookup()
                ->getRevisionById( $rev_id );
            if ( $revisionRecord ) {
                $logEntry->setTarget( $revisionRecord->getPageAsLinkTarget() );
            }
        } elseif ( $log_id ) {
            // This function is from revision deletion logic and has nothing to do with
            // change tags, but it appears to be the only other place in core where we
            // perform logged actions on log items.
            $logEntry->setTarget( RevDelLogList::suggestTarget( null, [ $log_id ] ) );
        }
 
        if ( !$logEntry->getTarget() ) {
            // target is required, so we have to set something
            $logEntry->setTarget( SpecialPage::getTitleFor( 'Tags' ) );
        }
 
        $logParams = [
            '4::revid' => $rev_id,
            '5::logid' => $log_id,
            '6:list:tagsAdded' => $tagsAdded,
            '7:number:tagsAddedCount' => count( $tagsAdded ),
            '8:list:tagsRemoved' => $tagsRemoved,
            '9:number:tagsRemovedCount' => count( $tagsRemoved ),
            'initialTags' => $initialTags,
        ];
        $logEntry->setParameters( $logParams );
        $logEntry->setRelations( [ 'Tag' => array_merge( $tagsAdded, $tagsRemoved ) ] );
 
        $dbw = wfGetDB( DB_PRIMARY );
        $logId = $logEntry->insert( $dbw );
        // Only send this to UDP, not RC, similar to patrol events
        $logEntry->publish( $logId, 'udp' );
 
        return Status::newGood( (object)[
            'logId' => $logId,
            'addedTags' => $tagsAdded,
            'removedTags' => $tagsRemoved,
        ] );
    }
 
    public static function modifyDisplayQuery( &$tables, &$fields, &$conds,
        &$join_conds, &$options, $filter_tag = '', bool $exclude = false
    ) {
        $useTagFilter = MediaWikiServices::getInstance()->getMainConfig()->get(
            MainConfigNames::UseTagFilter );
 
        // Normalize to arrays
        $tables = (array)$tables;
        $fields = (array)$fields;
        $conds = (array)$conds;
        $options = (array)$options;
 
        $fields['ts_tags'] = self::makeTagSummarySubquery( $tables );
        // We use an alias and qualify the conditions in case there are
        // multiple joins to this table.
        // In particular for compatibility with the RC filters that extension Translate does.
 
        // Figure out which ID field to use
        if ( in_array( 'recentchanges', $tables ) ) {
            $join_cond = self::DISPLAY_TABLE_ALIAS . '.ct_rc_id=rc_id';
        } elseif ( in_array( 'logging', $tables ) ) {
            $join_cond = self::DISPLAY_TABLE_ALIAS . '.ct_log_id=log_id';
        } elseif ( in_array( 'revision', $tables ) ) {
            $join_cond = self::DISPLAY_TABLE_ALIAS . '.ct_rev_id=rev_id';
        } elseif ( in_array( 'archive', $tables ) ) {
            $join_cond = self::DISPLAY_TABLE_ALIAS . '.ct_rev_id=ar_rev_id';
        } else {
            throw new InvalidArgumentException( 'Unable to determine appropriate JOIN condition for tagging.' );
        }
 
        if ( !$useTagFilter ) {
            return;
        }
 
        if ( !is_array( $filter_tag ) ) {
            // some callers provide false or null
            $filter_tag = (string)$filter_tag;
        }
 
        if ( $filter_tag !== [] && $filter_tag !== '' ) {
            // Somebody wants to filter on a tag.
            // Add an INNER JOIN on change_tag
            $tagTable = self::getDisplayTableName();
            $filterTagIds = [];
            $changeTagDefStore = MediaWikiServices::getInstance()->getChangeTagDefStore();
            foreach ( (array)$filter_tag as $filterTagName ) {
                try {
                    $filterTagIds[] = $changeTagDefStore->getId( $filterTagName );
                } catch ( NameTableAccessException $exception ) {
                }
            }
 
            if ( $exclude ) {
                if ( $filterTagIds !== [] ) {
                    $tables[self::DISPLAY_TABLE_ALIAS] = $tagTable;
                    $join_conds[self::DISPLAY_TABLE_ALIAS] = [
                        'LEFT JOIN',
                        [ $join_cond, self::DISPLAY_TABLE_ALIAS . '.ct_tag_id' => $filterTagIds ]
                    ];
                    $conds[] = self::DISPLAY_TABLE_ALIAS . ".ct_tag_id IS NULL";
                }
            } else {
                $tables[self::DISPLAY_TABLE_ALIAS] = $tagTable;
                $join_conds[self::DISPLAY_TABLE_ALIAS] = [ 'JOIN', $join_cond ];
                if ( $filterTagIds !== [] ) {
                    $conds[self::DISPLAY_TABLE_ALIAS . '.ct_tag_id'] = $filterTagIds;
                } else {
                    // all tags were invalid, return nothing
                    $conds[] = '0=1';
                }
 
                if (
                    is_array( $filter_tag ) && count( $filter_tag ) > 1 &&
                    !in_array( 'DISTINCT', $options )
                ) {
                    $options[] = 'DISTINCT';
                }
            }
        }
    }
 
    public static function getDisplayTableName() {
        $tagTable = self::CHANGE_TAG;
        if ( self::$avoidReopeningTablesForTesting && defined( 'MW_PHPUNIT_TEST' ) ) {
            $db = wfGetDB( DB_REPLICA );
 
            if ( $db->getType() === 'mysql' ) {
                // When filtering by tag, we are using the change_tag table twice:
                // Once in a join for filtering, and once in a sub-query to list all
                // tags for each revision. This does not work with temporary tables
                // on some versions of MySQL, which causes phpunit tests to fail.
                // As a hacky workaround, we copy the temporary table, and join
                // against the copy. It is acknowledged that this is quite horrific.
                // Discuss at T256006.
 
                $tagTable = 'change_tag_for_display_query';
                if ( !$db->tableExists( $tagTable ) ) {
                    $db->query(
                        'CREATE TEMPORARY TABLE IF NOT EXISTS ' . $db->tableName( $tagTable )
                        . ' LIKE ' . $db->tableName( self::CHANGE_TAG ),
                        __METHOD__
                    );
                    $db->query(
                        'INSERT IGNORE INTO ' . $db->tableName( $tagTable )
                        . ' SELECT * FROM ' . $db->tableName( self::CHANGE_TAG ),
                        __METHOD__
                    );
                }
            }
        }
        return $tagTable;
    }
 
    public static function makeTagSummarySubquery( $tables ) {
        // Normalize to arrays
        $tables = (array)$tables;
 
        // Figure out which ID field to use
        if ( in_array( 'recentchanges', $tables ) ) {
            $join_cond = 'ct_rc_id=rc_id';
        } elseif ( in_array( 'logging', $tables ) ) {
            $join_cond = 'ct_log_id=log_id';
        } elseif ( in_array( 'revision', $tables ) ) {
            $join_cond = 'ct_rev_id=rev_id';
        } elseif ( in_array( 'archive', $tables ) ) {
            $join_cond = 'ct_rev_id=ar_rev_id';
        } else {
            throw new InvalidArgumentException( 'Unable to determine appropriate JOIN condition for tagging.' );
        }
 
        $tagTables = [ self::CHANGE_TAG, self::CHANGE_TAG_DEF ];
        $join_cond_ts_tags = [ self::CHANGE_TAG_DEF => [ 'JOIN', 'ct_tag_id=ctd_id' ] ];
        $field = 'ctd_name';
 
        return wfGetDB( DB_REPLICA )->buildGroupConcatField(
            ',', $tagTables, $field, $join_cond, $join_cond_ts_tags
        );
    }
 
    public static function buildTagFilterSelector(
        $selected = '', $ooui = false, IContextSource $context = null
    ) {
        if ( !$context ) {
            $context = RequestContext::getMain();
        }
 
        $config = $context->getConfig();
        if ( !$config->get( MainConfigNames::UseTagFilter ) ||
        !count( self::listDefinedTags() ) ) {
            return [];
        }
 
        $tags = self::getChangeTagList( $context, $context->getLanguage() );
        $autocomplete = [];
        foreach ( $tags as $tagInfo ) {
            $autocomplete[ $tagInfo['label'] ] = $tagInfo['name'];
        }
 
        $data = [
            Html::rawElement(
                'label',
                [ 'for' => 'tagfilter' ],
                $context->msg( 'tag-filter' )->parse()
            )
        ];
 
        if ( $ooui ) {
            $options = Xml::listDropDownOptionsOoui( $autocomplete );
 
            $data[] = new OOUI\ComboBoxInputWidget( [
                'id' => 'tagfilter',
                'name' => 'tagfilter',
                'value' => $selected,
                'classes' => 'mw-tagfilter-input',
                'options' => $options,
            ] );
        } else {
            $datalist = new XmlSelect( false, 'tagfilter-datalist' );
            $datalist->setTagName( 'datalist' );
            $datalist->addOptions( $autocomplete );
 
            $data[] = Xml::input(
                'tagfilter',
                20,
                $selected,
                [
                    'class' => 'mw-tagfilter-input mw-ui-input mw-ui-input-inline',
                    'id' => 'tagfilter',
                    'list' => 'tagfilter-datalist',
                ]
            ) . $datalist->getHTML();
        }
 
        return $data;
    }
 
    public static function defineTag( $tag ) {
        $dbw = wfGetDB( DB_PRIMARY );
        $tagDef = [
            'ctd_name' => $tag,
            'ctd_user_defined' => 1,
            'ctd_count' => 0
        ];
        $dbw->upsert(
            self::CHANGE_TAG_DEF,
            $tagDef,
            'ctd_name',
            [ 'ctd_user_defined' => 1 ],
            __METHOD__
        );
 
        // clear the memcache of defined tags
        self::purgeTagCacheAll();
    }
 
    public static function undefineTag( $tag ) {
        $dbw = wfGetDB( DB_PRIMARY );
 
        $dbw->update(
            self::CHANGE_TAG_DEF,
            [ 'ctd_user_defined' => 0 ],
            [ 'ctd_name' => $tag ],
            __METHOD__
        );
 
        $dbw->delete(
            self::CHANGE_TAG_DEF,
            [ 'ctd_name' => $tag, 'ctd_count' => 0 ],
            __METHOD__
        );
 
        // clear the memcache of defined tags
        self::purgeTagCacheAll();
    }
 
    protected static function logTagManagementAction( string $action, string $tag, string $reason,
        UserIdentity $user, $tagCount = null, array $logEntryTags = []
    ) {
        $dbw = wfGetDB( DB_PRIMARY );
 
        $logEntry = new ManualLogEntry( 'managetags', $action );
        $logEntry->setPerformer( $user );
        // target page is not relevant, but it has to be set, so we just put in
        // the title of Special:Tags
        $logEntry->setTarget( Title::newFromText( 'Special:Tags' ) );
        $logEntry->setComment( $reason );
 
        $params = [ '4::tag' => $tag ];
        if ( $tagCount !== null ) {
            $params['5:number:count'] = $tagCount;
        }
        $logEntry->setParameters( $params );
        $logEntry->setRelations( [ 'Tag' => $tag ] );
        $logEntry->addTags( $logEntryTags );
 
        $logId = $logEntry->insert( $dbw );
        $logEntry->publish( $logId );
        return $logId;
    }
 
    public static function canActivateTag( $tag, Authority $performer = null ) {
        if ( $performer !== null ) {
            if ( !$performer->isAllowed( 'managechangetags' ) ) {
                return Status::newFatal( 'tags-manage-no-permission' );
            }
            if ( $performer->getBlock() && $performer->getBlock()->isSitewide() ) {
                return Status::newFatal(
                    'tags-manage-blocked',
                    $performer->getUser()->getName()
                );
            }
        }
 
        // defined tags cannot be activated (a defined tag is either extension-
        // defined, in which case the extension chooses whether or not to active it;
        // or user-defined, in which case it is considered active)
        $definedTags = self::listDefinedTags();
        if ( in_array( $tag, $definedTags ) ) {
            return Status::newFatal( 'tags-activate-not-allowed', $tag );
        }
 
        // non-existing tags cannot be activated
        $tagUsage = self::tagUsageStatistics();
        if ( !isset( $tagUsage[$tag] ) ) { // we already know the tag is undefined
            return Status::newFatal( 'tags-activate-not-found', $tag );
        }
 
        return Status::newGood();
    }
 
    public static function activateTagWithChecks( string $tag, string $reason, Authority $performer,
        bool $ignoreWarnings = false, array $logEntryTags = []
    ) {
        // are we allowed to do this?
        $result = self::canActivateTag( $tag, $performer );
        if ( $ignoreWarnings ? !$result->isOK() : !$result->isGood() ) {
            $result->value = null;
            return $result;
        }
 
        // do it!
        self::defineTag( $tag );
 
        // log it
        $logId = self::logTagManagementAction( 'activate', $tag, $reason, $performer->getUser(),
            null, $logEntryTags );
 
        return Status::newGood( $logId );
    }
 
    public static function canDeactivateTag( $tag, Authority $performer = null ) {
        if ( $performer !== null ) {
            if ( !$performer->isAllowed( 'managechangetags' ) ) {
                return Status::newFatal( 'tags-manage-no-permission' );
            }
            if ( $performer->getBlock() && $performer->getBlock()->isSitewide() ) {
                return Status::newFatal(
                    'tags-manage-blocked',
                    $performer->getUser()->getName()
                );
            }
        }
 
        // only explicitly-defined tags can be deactivated
        $explicitlyDefinedTags = self::listExplicitlyDefinedTags();
        if ( !in_array( $tag, $explicitlyDefinedTags ) ) {
            return Status::newFatal( 'tags-deactivate-not-allowed', $tag );
        }
        return Status::newGood();
    }
 
    public static function deactivateTagWithChecks( string $tag, string $reason, Authority $performer,
        bool $ignoreWarnings = false, array $logEntryTags = []
    ) {
        // are we allowed to do this?
        $result = self::canDeactivateTag( $tag, $performer );
        if ( $ignoreWarnings ? !$result->isOK() : !$result->isGood() ) {
            $result->value = null;
            return $result;
        }
 
        // do it!
        self::undefineTag( $tag );
 
        // log it
        $logId = self::logTagManagementAction( 'deactivate', $tag, $reason,
            $performer->getUser(), null, $logEntryTags );
 
        return Status::newGood( $logId );
    }
 
    public static function isTagNameValid( $tag ) {
        // no empty tags
        if ( $tag === '' ) {
            return Status::newFatal( 'tags-create-no-name' );
        }
 
        // tags cannot contain commas (used to be used as a delimiter in tag_summary table),
        // pipe (used as a delimiter between multiple tags in
        // SpecialRecentchanges and friends), or slashes (would break tag description messages in
        // MediaWiki namespace)
        if ( strpos( $tag, ',' ) !== false || strpos( $tag, '|' ) !== false
            || strpos( $tag, '/' ) !== false ) {
            return Status::newFatal( 'tags-create-invalid-chars' );
        }
 
        // could the MediaWiki namespace description messages be created?
        $title = Title::makeTitleSafe( NS_MEDIAWIKI, "Tag-$tag-description" );
        if ( $title === null ) {
            return Status::newFatal( 'tags-create-invalid-title-chars' );
        }
 
        return Status::newGood();
    }
 
    public static function canCreateTag( $tag, Authority $performer = null ) {
        $user = null;
        if ( $performer !== null ) {
            if ( !$performer->isAllowed( 'managechangetags' ) ) {
                return Status::newFatal( 'tags-manage-no-permission' );
            }
            if ( $performer->getBlock() && $performer->getBlock()->isSitewide() ) {
                return Status::newFatal(
                    'tags-manage-blocked',
                    $performer->getUser()->getName()
                );
            }
            // ChangeTagCanCreate hook still needs a full User object
            $user = MediaWikiServices::getInstance()->getUserFactory()->newFromAuthority( $performer );
        }
 
        $status = self::isTagNameValid( $tag );
        if ( !$status->isGood() ) {
            return $status;
        }
 
        // does the tag already exist?
        $tagUsage = self::tagUsageStatistics();
        if ( isset( $tagUsage[$tag] ) || in_array( $tag, self::listDefinedTags() ) ) {
            return Status::newFatal( 'tags-create-already-exists', $tag );
        }
 
        // check with hooks
        $canCreateResult = Status::newGood();
        Hooks::runner()->onChangeTagCanCreate( $tag, $user, $canCreateResult );
        return $canCreateResult;
    }
 
    public static function createTagWithChecks( string $tag, string $reason, Authority $performer,
        bool $ignoreWarnings = false, array $logEntryTags = []
    ) {
        // are we allowed to do this?
        $result = self::canCreateTag( $tag, $performer );
        if ( $ignoreWarnings ? !$result->isOK() : !$result->isGood() ) {
            $result->value = null;
            return $result;
        }
 
        // do it!
        self::defineTag( $tag );
 
        // log it
        $logId = self::logTagManagementAction( 'create', $tag, $reason,
            $performer->getUser(), null, $logEntryTags );
 
        return Status::newGood( $logId );
    }
 
    public static function deleteTagEverywhere( $tag ) {
        $dbw = wfGetDB( DB_PRIMARY );
        $dbw->startAtomic( __METHOD__ );
 
        // fetch tag id, this must be done before calling undefineTag(), see T225564
        $tagId = MediaWikiServices::getInstance()->getChangeTagDefStore()->getId( $tag );
 
        // set ctd_user_defined = 0
        self::undefineTag( $tag );
 
        // delete from change_tag
        $dbw->delete( self::CHANGE_TAG, [ 'ct_tag_id' => $tagId ], __METHOD__ );
        $dbw->delete( self::CHANGE_TAG_DEF, [ 'ctd_name' => $tag ], __METHOD__ );
        $dbw->endAtomic( __METHOD__ );
 
        // give extensions a chance
        $status = Status::newGood();
        Hooks::runner()->onChangeTagAfterDelete( $tag, $status );
        // let's not allow error results, as the actual tag deletion succeeded
        if ( !$status->isOK() ) {
            wfDebug( 'ChangeTagAfterDelete error condition downgraded to warning' );
            $status->setOK( true );
        }
 
        // clear the memcache of defined tags
        self::purgeTagCacheAll();
 
        return $status;
    }
 
    public static function canDeleteTag( $tag, Authority $performer = null, int $flags = 0 ) {
        $tagUsage = self::tagUsageStatistics();
        $user = null;
        if ( $performer !== null ) {
            if ( !$performer->isAllowed( 'deletechangetags' ) ) {
                return Status::newFatal( 'tags-delete-no-permission' );
            }
            if ( $performer->getBlock() && $performer->getBlock()->isSitewide() ) {
                return Status::newFatal(
                    'tags-manage-blocked',
                    $performer->getUser()->getName()
                );
            }
            // ChangeTagCanDelete hook still needs a full User object
            $user = MediaWikiServices::getInstance()->getUserFactory()->newFromAuthority( $performer );
        }
 
        if ( !isset( $tagUsage[$tag] ) && !in_array( $tag, self::listDefinedTags() ) ) {
            return Status::newFatal( 'tags-delete-not-found', $tag );
        }
 
        if ( $flags !== self::BYPASS_MAX_USAGE_CHECK &&
            isset( $tagUsage[$tag] ) &&
            $tagUsage[$tag] > self::MAX_DELETE_USES
        ) {
            return Status::newFatal( 'tags-delete-too-many-uses', $tag, self::MAX_DELETE_USES );
        }
 
        $softwareDefined = self::listSoftwareDefinedTags();
        if ( in_array( $tag, $softwareDefined ) ) {
            // extension-defined tags can't be deleted unless the extension
            // specifically allows it
            $status = Status::newFatal( 'tags-delete-not-allowed' );
        } else {
            // user-defined tags are deletable unless otherwise specified
            $status = Status::newGood();
        }
 
        Hooks::runner()->onChangeTagCanDelete( $tag, $user, $status );
        return $status;
    }
 
    public static function deleteTagWithChecks( string $tag, string $reason, Authority $performer,
        bool $ignoreWarnings = false, array $logEntryTags = []
    ) {
        // are we allowed to do this?
        $result = self::canDeleteTag( $tag, $performer );
        if ( $ignoreWarnings ? !$result->isOK() : !$result->isGood() ) {
            $result->value = null;
            return $result;
        }
 
        // store the tag usage statistics
        $tagUsage = self::tagUsageStatistics();
        $hitcount = $tagUsage[$tag] ?? 0;
 
        // do it!
        $deleteResult = self::deleteTagEverywhere( $tag );
        if ( !$deleteResult->isOK() ) {
            return $deleteResult;
        }
 
        // log it
        $logId = self::logTagManagementAction( 'delete', $tag, $reason, $performer->getUser(),
            $hitcount, $logEntryTags );
 
        $deleteResult->value = $logId;
        return $deleteResult;
    }
 
    public static function listSoftwareActivatedTags() {
        // core active tags
        $tags = self::getSoftwareTags();
        $hookContainer = MediaWikiServices::getInstance()->getHookContainer();
        if ( !$hookContainer->isRegistered( 'ChangeTagsListActive' ) ) {
            return $tags;
        }
        $hookRunner = new HookRunner( $hookContainer );
        $cache = MediaWikiServices::getInstance()->getMainWANObjectCache();
        return $cache->getWithSetCallback(
            $cache->makeKey( 'active-tags' ),
            WANObjectCache::TTL_MINUTE * 5,
            static function ( $oldValue, &$ttl, array &$setOpts ) use ( $tags, $hookRunner ) {
                $setOpts += Database::getCacheSetOptions( wfGetDB( DB_REPLICA ) );
 
                // Ask extensions which tags they consider active
                $hookRunner->onChangeTagsListActive( $tags );
                return $tags;
            },
            [
                'checkKeys' => [ $cache->makeKey( 'active-tags' ) ],
                'lockTSE' => WANObjectCache::TTL_MINUTE * 5,
                'pcTTL' => WANObjectCache::TTL_PROC_LONG
            ]
        );
    }
 
    public static function listDefinedTags() {
        $tags1 = self::listExplicitlyDefinedTags();
        $tags2 = self::listSoftwareDefinedTags();
        return array_values( array_unique( array_merge( $tags1, $tags2 ) ) );
    }
 
    public static function listExplicitlyDefinedTags() {
        $fname = __METHOD__;
 
        $cache = MediaWikiServices::getInstance()->getMainWANObjectCache();
        return $cache->getWithSetCallback(
            $cache->makeKey( 'valid-tags-db' ),
            WANObjectCache::TTL_MINUTE * 5,
            static function ( $oldValue, &$ttl, array &$setOpts ) use ( $fname ) {
                $dbr = wfGetDB( DB_REPLICA );
 
                $setOpts += Database::getCacheSetOptions( $dbr );
                $tags = $dbr->newSelectQueryBuilder()
                    ->select( 'ctd_name' )
                    ->from( self::CHANGE_TAG_DEF )
                    ->where( [ 'ctd_user_defined' => 1 ] )
                    ->caller( $fname )
                    ->fetchFieldValues();
 
                return array_unique( $tags );
            },
            [
                'checkKeys' => [ $cache->makeKey( 'valid-tags-db' ) ],
                'lockTSE' => WANObjectCache::TTL_MINUTE * 5,
                'pcTTL' => WANObjectCache::TTL_PROC_LONG
            ]
        );
    }
 
    public static function listSoftwareDefinedTags() {
        // core defined tags
        $tags = self::getSoftwareTags( true );
        $hookContainer = MediaWikiServices::getInstance()->getHookContainer();
        if ( !$hookContainer->isRegistered( 'ListDefinedTags' ) ) {
            return $tags;
        }
        $hookRunner = new HookRunner( $hookContainer );
        $cache = MediaWikiServices::getInstance()->getMainWANObjectCache();
        return $cache->getWithSetCallback(
            $cache->makeKey( 'valid-tags-hook' ),
            WANObjectCache::TTL_MINUTE * 5,
            static function ( $oldValue, &$ttl, array &$setOpts ) use ( $tags, $hookRunner ) {
                $setOpts += Database::getCacheSetOptions( wfGetDB( DB_REPLICA ) );
 
                $hookRunner->onListDefinedTags( $tags );
                return array_unique( $tags );
            },
            [
                'checkKeys' => [ $cache->makeKey( 'valid-tags-hook' ) ],
                'lockTSE' => WANObjectCache::TTL_MINUTE * 5,
                'pcTTL' => WANObjectCache::TTL_PROC_LONG
            ]
        );
    }
 
    public static function purgeTagCacheAll() {
        $cache = MediaWikiServices::getInstance()->getMainWANObjectCache();
 
        $cache->touchCheckKey( $cache->makeKey( 'active-tags' ) );
        $cache->touchCheckKey( $cache->makeKey( 'valid-tags-db' ) );
        $cache->touchCheckKey( $cache->makeKey( 'valid-tags-hook' ) );
        $cache->touchCheckKey( $cache->makeKey( 'tags-usage-statistics' ) );
 
        MediaWikiServices::getInstance()->getChangeTagDefStore()->reloadMap();
    }
 
    public static function tagUsageStatistics() {
        $fname = __METHOD__;
 
        $cache = MediaWikiServices::getInstance()->getMainWANObjectCache();
        return $cache->getWithSetCallback(
            $cache->makeKey( 'tags-usage-statistics' ),
            WANObjectCache::TTL_MINUTE * 5,
            static function ( $oldValue, &$ttl, array &$setOpts ) use ( $fname ) {
                $dbr = wfGetDB( DB_REPLICA );
                $res = $dbr->newSelectQueryBuilder()
                    ->select( [ 'ctd_name', 'ctd_count' ] )
                    ->from( self::CHANGE_TAG_DEF )
                    ->orderBy( 'ctd_count', SelectQueryBuilder::SORT_DESC )
                    ->caller( $fname )
                    ->fetchResultSet();
 
                $out = [];
                foreach ( $res as $row ) {
                    $out[$row->ctd_name] = $row->ctd_count;
                }
 
                return $out;
            },
            [
                'checkKeys' => [ $cache->makeKey( 'tags-usage-statistics' ) ],
                'lockTSE' => WANObjectCache::TTL_MINUTE * 5,
                'pcTTL' => WANObjectCache::TTL_PROC_LONG
            ]
        );
    }
 
    private const TAG_DESC_CHARACTER_LIMIT = 120;
 
    public static function getChangeTagListSummary( MessageLocalizer $localizer, Language $lang ) {
        $cache = MediaWikiServices::getInstance()->getMainWANObjectCache();
        return $cache->getWithSetCallback(
            $cache->makeKey( 'tags-list-summary', $lang->getCode() ),
            WANObjectCache::TTL_DAY,
            static function ( $oldValue, &$ttl, array &$setOpts ) use ( $localizer ) {
                $tagHitCounts = self::tagUsageStatistics();
 
                $result = [];
                // Only list tags that are still actively defined
                foreach ( self::listDefinedTags() as $tagName ) {
                    // Only list tags with more than 0 hits
                    $hits = $tagHitCounts[$tagName] ?? 0;
                    if ( $hits <= 0 ) {
                        continue;
                    }
 
                    $labelMsg = self::tagShortDescriptionMessage( $tagName, $localizer );
                    $descriptionMsg = self::tagLongDescriptionMessage( $tagName, $localizer );
                    // Don't cache the message object, use the correct MessageLocalizer to parse later.
                    $result[] = [
                        'name' => $tagName,
                        'labelMsg' => (bool)$labelMsg,
                        'label' => $labelMsg ? $labelMsg->plain() : $tagName,
                        'descriptionMsg' => (bool)$descriptionMsg,
                        'description' => $descriptionMsg ? $descriptionMsg->plain() : '',
                        'cssClass' => Sanitizer::escapeClass( 'mw-tag-' . $tagName ),
                    ];
                }
                return $result;
            }
        );
    }
 
    public static function getChangeTagList( MessageLocalizer $localizer, Language $lang ) {
        $tags = self::getChangeTagListSummary( $localizer, $lang );
        foreach ( $tags as &$tagInfo ) {
            if ( $tagInfo['labelMsg'] ) {
                // Use localizer with the correct page title to parse plain message from the cache.
                $labelMsg = new RawMessage( $tagInfo['label'] );
                $tagInfo['label'] = Sanitizer::stripAllTags( $localizer->msg( $labelMsg )->parse() );
            } else {
                $tagInfo['label'] = $localizer->msg( 'tag-hidden', $tagInfo['name'] )->text();
            }
            if ( $tagInfo['descriptionMsg'] ) {
                $descriptionMsg = new RawMessage( $tagInfo['description'] );
                $tagInfo['description'] = $lang->truncateForVisual(
                    Sanitizer::stripAllTags( $localizer->msg( $descriptionMsg )->parse() ),
                    self::TAG_DESC_CHARACTER_LIMIT
                );
            }
            unset( $tagInfo['labelMsg'] );
            unset( $tagInfo['descriptionMsg'] );
        }
 
        // Instead of sorting by hit count (disabled for now), sort by display name
        usort( $tags, static function ( $a, $b ) {
            return strcasecmp( $a['label'], $b['label'] );
        } );
        return $tags;
    }
 
    public static function showTagEditingUI( Authority $performer ) {
        return $performer->isAllowed( 'changetags' ) && (bool)self::listExplicitlyDefinedTags();
    }
}