Revision.php

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<?php
use Wikimedia\Rdbms\Database;
use Wikimedia\Rdbms\IDatabase;
use MediaWiki\Linker\LinkTarget;
use MediaWiki\MediaWikiServices;
use Wikimedia\Rdbms\ResultWrapper;
use Wikimedia\Rdbms\FakeResultWrapper;
 
class Revision implements IDBAccessObject {
    protected $mId;
    protected $mPage;
    protected $mUserText;
    protected $mOrigUserText;
    protected $mUser;
    protected $mMinorEdit;
    protected $mTimestamp;
    protected $mDeleted;
    protected $mSize;
    protected $mSha1;
    protected $mParentId;
    protected $mComment;
    protected $mText;
    protected $mTextId;
    protected $mUnpatrolled;
 
    protected $mTextRow;
 
    protected $mTitle;
    protected $mCurrent;
    protected $mContentModel;
    protected $mContentFormat;
 
    protected $mContent;
    protected $mContentHandler;
 
    protected $mQueryFlags = 0;
    protected $mRefreshMutableFields = false;
    protected $mWiki = false;
 
    // Revision deletion constants
    const DELETED_TEXT = 1;
    const DELETED_COMMENT = 2;
    const DELETED_USER = 4;
    const DELETED_RESTRICTED = 8;
    const SUPPRESSED_USER = 12; // convenience
    const SUPPRESSED_ALL = 15; // convenience
 
    // Audience options for accessors
    const FOR_PUBLIC = 1;
    const FOR_THIS_USER = 2;
    const RAW = 3;
 
    const TEXT_CACHE_GROUP = 'revisiontext:10'; // process cache name and max key count
 
    public static function newFromId( $id, $flags = 0 ) {
        return self::newFromConds( [ 'rev_id' => intval( $id ) ], $flags );
    }
 
    public static function newFromTitle( LinkTarget $linkTarget, $id = 0, $flags = 0 ) {
        $conds = [
            'page_namespace' => $linkTarget->getNamespace(),
            'page_title' => $linkTarget->getDBkey()
        ];
        if ( $id ) {
            // Use the specified ID
            $conds['rev_id'] = $id;
            return self::newFromConds( $conds, $flags );
        } else {
            // Use a join to get the latest revision
            $conds[] = 'rev_id=page_latest';
            $db = wfGetDB( ( $flags & self::READ_LATEST ) ? DB_MASTER : DB_REPLICA );
            return self::loadFromConds( $db, $conds, $flags );
        }
    }
 
    public static function newFromPageId( $pageId, $revId = 0, $flags = 0 ) {
        $conds = [ 'page_id' => $pageId ];
        if ( $revId ) {
            $conds['rev_id'] = $revId;
            return self::newFromConds( $conds, $flags );
        } else {
            // Use a join to get the latest revision
            $conds[] = 'rev_id = page_latest';
            $db = wfGetDB( ( $flags & self::READ_LATEST ) ? DB_MASTER : DB_REPLICA );
            return self::loadFromConds( $db, $conds, $flags );
        }
    }
 
    public static function newFromArchiveRow( $row, $overrides = [] ) {
        global $wgContentHandlerUseDB;
 
        $attribs = $overrides + [
            'page'       => isset( $row->ar_page_id ) ? $row->ar_page_id : null,
            'id'         => isset( $row->ar_rev_id ) ? $row->ar_rev_id : null,
            'comment'    => $row->ar_comment,
            'user'       => $row->ar_user,
            'user_text'  => $row->ar_user_text,
            'timestamp'  => $row->ar_timestamp,
            'minor_edit' => $row->ar_minor_edit,
            'text_id'    => isset( $row->ar_text_id ) ? $row->ar_text_id : null,
            'deleted'    => $row->ar_deleted,
            'len'        => $row->ar_len,
            'sha1'       => isset( $row->ar_sha1 ) ? $row->ar_sha1 : null,
            'content_model'   => isset( $row->ar_content_model ) ? $row->ar_content_model : null,
            'content_format'  => isset( $row->ar_content_format ) ? $row->ar_content_format : null,
        ];
 
        if ( !$wgContentHandlerUseDB ) {
            unset( $attribs['content_model'] );
            unset( $attribs['content_format'] );
        }
 
        if ( !isset( $attribs['title'] )
            && isset( $row->ar_namespace )
            && isset( $row->ar_title )
        ) {
            $attribs['title'] = Title::makeTitle( $row->ar_namespace, $row->ar_title );
        }
 
        if ( isset( $row->ar_text ) && !$row->ar_text_id ) {
            // Pre-1.5 ar_text row
            $attribs['text'] = self::getRevisionText( $row, 'ar_' );
            if ( $attribs['text'] === false ) {
                throw new MWException( 'Unable to load text from archive row (possibly T24624)' );
            }
        }
        return new self( $attribs );
    }
 
    public static function newFromRow( $row ) {
        return new self( $row );
    }
 
    public static function loadFromId( $db, $id ) {
        return self::loadFromConds( $db, [ 'rev_id' => intval( $id ) ] );
    }
 
    public static function loadFromPageId( $db, $pageid, $id = 0 ) {
        $conds = [ 'rev_page' => intval( $pageid ), 'page_id' => intval( $pageid ) ];
        if ( $id ) {
            $conds['rev_id'] = intval( $id );
        } else {
            $conds[] = 'rev_id=page_latest';
        }
        return self::loadFromConds( $db, $conds );
    }
 
    public static function loadFromTitle( $db, $title, $id = 0 ) {
        if ( $id ) {
            $matchId = intval( $id );
        } else {
            $matchId = 'page_latest';
        }
        return self::loadFromConds( $db,
            [
                "rev_id=$matchId",
                'page_namespace' => $title->getNamespace(),
                'page_title' => $title->getDBkey()
            ]
        );
    }
 
    public static function loadFromTimestamp( $db, $title, $timestamp ) {
        return self::loadFromConds( $db,
            [
                'rev_timestamp' => $db->timestamp( $timestamp ),
                'page_namespace' => $title->getNamespace(),
                'page_title' => $title->getDBkey()
            ]
        );
    }
 
    private static function newFromConds( $conditions, $flags = 0 ) {
        $db = wfGetDB( ( $flags & self::READ_LATEST ) ? DB_MASTER : DB_REPLICA );
 
        $rev = self::loadFromConds( $db, $conditions, $flags );
        // Make sure new pending/committed revision are visibile later on
        // within web requests to certain avoid bugs like T93866 and T94407.
        if ( !$rev
            && !( $flags & self::READ_LATEST )
            && wfGetLB()->getServerCount() > 1
            && wfGetLB()->hasOrMadeRecentMasterChanges()
        ) {
            $flags = self::READ_LATEST;
            $db = wfGetDB( DB_MASTER );
            $rev = self::loadFromConds( $db, $conditions, $flags );
        }
 
        if ( $rev ) {
            $rev->mQueryFlags = $flags;
        }
 
        return $rev;
    }
 
    private static function loadFromConds( $db, $conditions, $flags = 0 ) {
        $row = self::fetchFromConds( $db, $conditions, $flags );
        if ( $row ) {
            $rev = new Revision( $row );
            $rev->mWiki = $db->getWikiID();
 
            return $rev;
        }
 
        return null;
    }
 
    public static function fetchRevision( LinkTarget $title ) {
        $row = self::fetchFromConds(
            wfGetDB( DB_REPLICA ),
            [
                'rev_id=page_latest',
                'page_namespace' => $title->getNamespace(),
                'page_title' => $title->getDBkey()
            ]
        );
 
        return new FakeResultWrapper( $row ? [ $row ] : [] );
    }
 
    private static function fetchFromConds( $db, $conditions, $flags = 0 ) {
        $fields = array_merge(
            self::selectFields(),
            self::selectPageFields(),
            self::selectUserFields()
        );
        $options = [];
        if ( ( $flags & self::READ_LOCKING ) == self::READ_LOCKING ) {
            $options[] = 'FOR UPDATE';
        }
        return $db->selectRow(
            [ 'revision', 'page', 'user' ],
            $fields,
            $conditions,
            __METHOD__,
            $options,
            [ 'page' => self::pageJoinCond(), 'user' => self::userJoinCond() ]
        );
    }
 
    public static function userJoinCond() {
        return [ 'LEFT JOIN', [ 'rev_user != 0', 'user_id = rev_user' ] ];
    }
 
    public static function pageJoinCond() {
        return [ 'INNER JOIN', [ 'page_id = rev_page' ] ];
    }
 
    public static function selectFields() {
        global $wgContentHandlerUseDB;
 
        $fields = [
            'rev_id',
            'rev_page',
            'rev_text_id',
            'rev_timestamp',
            'rev_comment',
            'rev_user_text',
            'rev_user',
            'rev_minor_edit',
            'rev_deleted',
            'rev_len',
            'rev_parent_id',
            'rev_sha1',
        ];
 
        if ( $wgContentHandlerUseDB ) {
            $fields[] = 'rev_content_format';
            $fields[] = 'rev_content_model';
        }
 
        return $fields;
    }
 
    public static function selectArchiveFields() {
        global $wgContentHandlerUseDB;
        $fields = [
            'ar_id',
            'ar_page_id',
            'ar_rev_id',
            'ar_text',
            'ar_text_id',
            'ar_timestamp',
            'ar_comment',
            'ar_user_text',
            'ar_user',
            'ar_minor_edit',
            'ar_deleted',
            'ar_len',
            'ar_parent_id',
            'ar_sha1',
        ];
 
        if ( $wgContentHandlerUseDB ) {
            $fields[] = 'ar_content_format';
            $fields[] = 'ar_content_model';
        }
        return $fields;
    }
 
    public static function selectTextFields() {
        return [
            'old_text',
            'old_flags'
        ];
    }
 
    public static function selectPageFields() {
        return [
            'page_namespace',
            'page_title',
            'page_id',
            'page_latest',
            'page_is_redirect',
            'page_len',
        ];
    }
 
    public static function selectUserFields() {
        return [ 'user_name' ];
    }
 
    public static function getParentLengths( $db, array $revIds ) {
        $revLens = [];
        if ( !$revIds ) {
            return $revLens; // empty
        }
        $res = $db->select( 'revision',
            [ 'rev_id', 'rev_len' ],
            [ 'rev_id' => $revIds ],
            __METHOD__ );
        foreach ( $res as $row ) {
            $revLens[$row->rev_id] = $row->rev_len;
        }
        return $revLens;
    }
 
    function __construct( $row ) {
        if ( is_object( $row ) ) {
            $this->mId = intval( $row->rev_id );
            $this->mPage = intval( $row->rev_page );
            $this->mTextId = intval( $row->rev_text_id );
            $this->mComment = $row->rev_comment;
            $this->mUser = intval( $row->rev_user );
            $this->mMinorEdit = intval( $row->rev_minor_edit );
            $this->mTimestamp = $row->rev_timestamp;
            $this->mDeleted = intval( $row->rev_deleted );
 
            if ( !isset( $row->rev_parent_id ) ) {
                $this->mParentId = null;
            } else {
                $this->mParentId = intval( $row->rev_parent_id );
            }
 
            if ( !isset( $row->rev_len ) ) {
                $this->mSize = null;
            } else {
                $this->mSize = intval( $row->rev_len );
            }
 
            if ( !isset( $row->rev_sha1 ) ) {
                $this->mSha1 = null;
            } else {
                $this->mSha1 = $row->rev_sha1;
            }
 
            if ( isset( $row->page_latest ) ) {
                $this->mCurrent = ( $row->rev_id == $row->page_latest );
                $this->mTitle = Title::newFromRow( $row );
            } else {
                $this->mCurrent = false;
                $this->mTitle = null;
            }
 
            if ( !isset( $row->rev_content_model ) ) {
                $this->mContentModel = null; # determine on demand if needed
            } else {
                $this->mContentModel = strval( $row->rev_content_model );
            }
 
            if ( !isset( $row->rev_content_format ) ) {
                $this->mContentFormat = null; # determine on demand if needed
            } else {
                $this->mContentFormat = strval( $row->rev_content_format );
            }
 
            // Lazy extraction...
            $this->mText = null;
            if ( isset( $row->old_text ) ) {
                $this->mTextRow = $row;
            } else {
                // 'text' table row entry will be lazy-loaded
                $this->mTextRow = null;
            }
 
            // Use user_name for users and rev_user_text for IPs...
            $this->mUserText = null; // lazy load if left null
            if ( $this->mUser == 0 ) {
                $this->mUserText = $row->rev_user_text; // IP user
            } elseif ( isset( $row->user_name ) ) {
                $this->mUserText = $row->user_name; // logged-in user
            }
            $this->mOrigUserText = $row->rev_user_text;
        } elseif ( is_array( $row ) ) {
            // Build a new revision to be saved...
            global $wgUser; // ugh
 
            # if we have a content object, use it to set the model and type
            if ( !empty( $row['content'] ) ) {
                // @todo when is that set? test with external store setup! check out insertOn() [dk]
                if ( !empty( $row['text_id'] ) ) {
                    throw new MWException( "Text already stored in external store (id {$row['text_id']}), " .
                        "can't serialize content object" );
                }
 
                $row['content_model'] = $row['content']->getModel();
                # note: mContentFormat is initializes later accordingly
                # note: content is serialized later in this method!
                # also set text to null?
            }
 
            $this->mId = isset( $row['id'] ) ? intval( $row['id'] ) : null;
            $this->mPage = isset( $row['page'] ) ? intval( $row['page'] ) : null;
            $this->mTextId = isset( $row['text_id'] ) ? intval( $row['text_id'] ) : null;
            $this->mUserText = isset( $row['user_text'] )
                ? strval( $row['user_text'] ) : $wgUser->getName();
            $this->mUser = isset( $row['user'] ) ? intval( $row['user'] ) : $wgUser->getId();
            $this->mMinorEdit = isset( $row['minor_edit'] ) ? intval( $row['minor_edit'] ) : 0;
            $this->mTimestamp = isset( $row['timestamp'] )
                ? strval( $row['timestamp'] ) : wfTimestampNow();
            $this->mDeleted = isset( $row['deleted'] ) ? intval( $row['deleted'] ) : 0;
            $this->mSize = isset( $row['len'] ) ? intval( $row['len'] ) : null;
            $this->mParentId = isset( $row['parent_id'] ) ? intval( $row['parent_id'] ) : null;
            $this->mSha1 = isset( $row['sha1'] ) ? strval( $row['sha1'] ) : null;
 
            $this->mContentModel = isset( $row['content_model'] )
                ? strval( $row['content_model'] ) : null;
            $this->mContentFormat = isset( $row['content_format'] )
                ? strval( $row['content_format'] ) : null;
 
            // Enforce spacing trimming on supplied text
            $this->mComment = isset( $row['comment'] ) ? trim( strval( $row['comment'] ) ) : null;
            $this->mText = isset( $row['text'] ) ? rtrim( strval( $row['text'] ) ) : null;
            $this->mTextRow = null;
 
            $this->mTitle = isset( $row['title'] ) ? $row['title'] : null;
 
            // if we have a Content object, override mText and mContentModel
            if ( !empty( $row['content'] ) ) {
                if ( !( $row['content'] instanceof Content ) ) {
                    throw new MWException( '`content` field must contain a Content object.' );
                }
 
                $handler = $this->getContentHandler();
                $this->mContent = $row['content'];
 
                $this->mContentModel = $this->mContent->getModel();
                $this->mContentHandler = null;
 
                $this->mText = $handler->serializeContent( $row['content'], $this->getContentFormat() );
            } elseif ( $this->mText !== null ) {
                $handler = $this->getContentHandler();
                $this->mContent = $handler->unserializeContent( $this->mText );
            }
 
            // If we have a Title object, make sure it is consistent with mPage.
            if ( $this->mTitle && $this->mTitle->exists() ) {
                if ( $this->mPage === null ) {
                    // if the page ID wasn't known, set it now
                    $this->mPage = $this->mTitle->getArticleID();
                } elseif ( $this->mTitle->getArticleID() !== $this->mPage ) {
                    // Got different page IDs. This may be legit (e.g. during undeletion),
                    // but it seems worth mentioning it in the log.
                    wfDebug( "Page ID " . $this->mPage . " mismatches the ID " .
                        $this->mTitle->getArticleID() . " provided by the Title object." );
                }
            }
 
            $this->mCurrent = false;
 
            // If we still have no length, see it we have the text to figure it out
            if ( !$this->mSize && $this->mContent !== null ) {
                $this->mSize = $this->mContent->getSize();
            }
 
            // Same for sha1
            if ( $this->mSha1 === null ) {
                $this->mSha1 = $this->mText === null ? null : self::base36Sha1( $this->mText );
            }
 
            // force lazy init
            $this->getContentModel();
            $this->getContentFormat();
        } else {
            throw new MWException( 'Revision constructor passed invalid row format.' );
        }
        $this->mUnpatrolled = null;
    }
 
    public function getId() {
        return $this->mId;
    }
 
    public function setId( $id ) {
        $this->mId = (int)$id;
    }
 
    public function setUserIdAndName( $id, $name ) {
        $this->mUser = (int)$id;
        $this->mUserText = $name;
        $this->mOrigUserText = $name;
    }
 
    public function getTextId() {
        return $this->mTextId;
    }
 
    public function getParentId() {
        return $this->mParentId;
    }
 
    public function getSize() {
        return $this->mSize;
    }
 
    public function getSha1() {
        return $this->mSha1;
    }
 
    public function getTitle() {
        if ( $this->mTitle !== null ) {
            return $this->mTitle;
        }
        // rev_id is defined as NOT NULL, but this revision may not yet have been inserted.
        if ( $this->mId !== null ) {
            $dbr = wfGetLB( $this->mWiki )->getConnectionRef( DB_REPLICA, [], $this->mWiki );
            $row = $dbr->selectRow(
                [ 'page', 'revision' ],
                self::selectPageFields(),
                [ 'page_id=rev_page', 'rev_id' => $this->mId ],
                __METHOD__
            );
            if ( $row ) {
                // @TODO: better foreign title handling
                $this->mTitle = Title::newFromRow( $row );
            }
        }
 
        if ( $this->mWiki === false || $this->mWiki === wfWikiID() ) {
            // Loading by ID is best, though not possible for foreign titles
            if ( !$this->mTitle && $this->mPage !== null && $this->mPage > 0 ) {
                $this->mTitle = Title::newFromID( $this->mPage );
            }
        }
 
        return $this->mTitle;
    }
 
    public function setTitle( $title ) {
        $this->mTitle = $title;
    }
 
    public function getPage() {
        return $this->mPage;
    }
 
    public function getUser( $audience = self::FOR_PUBLIC, User $user = null ) {
        if ( $audience == self::FOR_PUBLIC && $this->isDeleted( self::DELETED_USER ) ) {
            return 0;
        } elseif ( $audience == self::FOR_THIS_USER && !$this->userCan( self::DELETED_USER, $user ) ) {
            return 0;
        } else {
            return $this->mUser;
        }
    }
 
    public function getRawUser() {
        wfDeprecated( __METHOD__, '1.25' );
        return $this->getUser( self::RAW );
    }
 
    public function getUserText( $audience = self::FOR_PUBLIC, User $user = null ) {
        $this->loadMutableFields();
 
        if ( $audience == self::FOR_PUBLIC && $this->isDeleted( self::DELETED_USER ) ) {
            return '';
        } elseif ( $audience == self::FOR_THIS_USER && !$this->userCan( self::DELETED_USER, $user ) ) {
            return '';
        } else {
            if ( $this->mUserText === null ) {
                $this->mUserText = User::whoIs( $this->mUser ); // load on demand
                if ( $this->mUserText === false ) {
                    # This shouldn't happen, but it can if the wiki was recovered
                    # via importing revs and there is no user table entry yet.
                    $this->mUserText = $this->mOrigUserText;
                }
            }
            return $this->mUserText;
        }
    }
 
    public function getRawUserText() {
        wfDeprecated( __METHOD__, '1.25' );
        return $this->getUserText( self::RAW );
    }
 
    function getComment( $audience = self::FOR_PUBLIC, User $user = null ) {
        if ( $audience == self::FOR_PUBLIC && $this->isDeleted( self::DELETED_COMMENT ) ) {
            return '';
        } elseif ( $audience == self::FOR_THIS_USER && !$this->userCan( self::DELETED_COMMENT, $user ) ) {
            return '';
        } else {
            return $this->mComment;
        }
    }
 
    public function getRawComment() {
        wfDeprecated( __METHOD__, '1.25' );
        return $this->getComment( self::RAW );
    }
 
    public function isMinor() {
        return (bool)$this->mMinorEdit;
    }
 
    public function isUnpatrolled() {
        if ( $this->mUnpatrolled !== null ) {
            return $this->mUnpatrolled;
        }
        $rc = $this->getRecentChange();
        if ( $rc && $rc->getAttribute( 'rc_patrolled' ) == 0 ) {
            $this->mUnpatrolled = $rc->getAttribute( 'rc_id' );
        } else {
            $this->mUnpatrolled = 0;
        }
        return $this->mUnpatrolled;
    }
 
    public function getRecentChange( $flags = 0 ) {
        $dbr = wfGetDB( DB_REPLICA );
 
        list( $dbType, ) = DBAccessObjectUtils::getDBOptions( $flags );
 
        return RecentChange::newFromConds(
            [
                'rc_user_text' => $this->getUserText( Revision::RAW ),
                'rc_timestamp' => $dbr->timestamp( $this->getTimestamp() ),
                'rc_this_oldid' => $this->getId()
            ],
            __METHOD__,
            $dbType
        );
    }
 
    public function isDeleted( $field ) {
        if ( $this->isCurrent() && $field === self::DELETED_TEXT ) {
            // Current revisions of pages cannot have the content hidden. Skipping this
            // check is very useful for Parser as it fetches templates using newKnownCurrent().
            // Calling getVisibility() in that case triggers a verification database query.
            return false; // no need to check
        }
 
        return ( $this->getVisibility() & $field ) == $field;
    }
 
    public function getVisibility() {
        $this->loadMutableFields();
 
        return (int)$this->mDeleted;
    }
 
    public function getContent( $audience = self::FOR_PUBLIC, User $user = null ) {
        if ( $audience == self::FOR_PUBLIC && $this->isDeleted( self::DELETED_TEXT ) ) {
            return null;
        } elseif ( $audience == self::FOR_THIS_USER && !$this->userCan( self::DELETED_TEXT, $user ) ) {
            return null;
        } else {
            return $this->getContentInternal();
        }
    }
 
    public function getSerializedData() {
        if ( $this->mText === null ) {
            // Revision is immutable. Load on demand.
            $this->mText = $this->loadText();
        }
 
        return $this->mText;
    }
 
    protected function getContentInternal() {
        if ( $this->mContent === null ) {
            $text = $this->getSerializedData();
 
            if ( $text !== null && $text !== false ) {
                // Unserialize content
                $handler = $this->getContentHandler();
                $format = $this->getContentFormat();
 
                $this->mContent = $handler->unserializeContent( $text, $format );
            }
        }
 
        // NOTE: copy() will return $this for immutable content objects
        return $this->mContent ? $this->mContent->copy() : null;
    }
 
    public function getContentModel() {
        if ( !$this->mContentModel ) {
            $title = $this->getTitle();
            if ( $title ) {
                $this->mContentModel = ContentHandler::getDefaultModelFor( $title );
            } else {
                $this->mContentModel = CONTENT_MODEL_WIKITEXT;
            }
 
            assert( !empty( $this->mContentModel ) );
        }
 
        return $this->mContentModel;
    }
 
    public function getContentFormat() {
        if ( !$this->mContentFormat ) {
            $handler = $this->getContentHandler();
            $this->mContentFormat = $handler->getDefaultFormat();
 
            assert( !empty( $this->mContentFormat ) );
        }
 
        return $this->mContentFormat;
    }
 
    public function getContentHandler() {
        if ( !$this->mContentHandler ) {
            $model = $this->getContentModel();
            $this->mContentHandler = ContentHandler::getForModelID( $model );
 
            $format = $this->getContentFormat();
 
            if ( !$this->mContentHandler->isSupportedFormat( $format ) ) {
                throw new MWException( "Oops, the content format $format is not supported for "
                    . "this content model, $model" );
            }
        }
 
        return $this->mContentHandler;
    }
 
    public function getTimestamp() {
        return wfTimestamp( TS_MW, $this->mTimestamp );
    }
 
    public function isCurrent() {
        return $this->mCurrent;
    }
 
    public function getPrevious() {
        if ( $this->getTitle() ) {
            $prev = $this->getTitle()->getPreviousRevisionID( $this->getId() );
            if ( $prev ) {
                return self::newFromTitle( $this->getTitle(), $prev );
            }
        }
        return null;
    }
 
    public function getNext() {
        if ( $this->getTitle() ) {
            $next = $this->getTitle()->getNextRevisionID( $this->getId() );
            if ( $next ) {
                return self::newFromTitle( $this->getTitle(), $next );
            }
        }
        return null;
    }
 
    private function getPreviousRevisionId( $db ) {
        if ( $this->mPage === null ) {
            return 0;
        }
        # Use page_latest if ID is not given
        if ( !$this->mId ) {
            $prevId = $db->selectField( 'page', 'page_latest',
                [ 'page_id' => $this->mPage ],
                __METHOD__ );
        } else {
            $prevId = $db->selectField( 'revision', 'rev_id',
                [ 'rev_page' => $this->mPage, 'rev_id < ' . $this->mId ],
                __METHOD__,
                [ 'ORDER BY' => 'rev_id DESC' ] );
        }
        return intval( $prevId );
    }
 
    public static function getRevisionText( $row, $prefix = 'old_', $wiki = false ) {
        $textField = $prefix . 'text';
        $flagsField = $prefix . 'flags';
 
        if ( isset( $row->$flagsField ) ) {
            $flags = explode( ',', $row->$flagsField );
        } else {
            $flags = [];
        }
 
        if ( isset( $row->$textField ) ) {
            $text = $row->$textField;
        } else {
            return false;
        }
 
        // Use external methods for external objects, text in table is URL-only then
        if ( in_array( 'external', $flags ) ) {
            $url = $text;
            $parts = explode( '://', $url, 2 );
            if ( count( $parts ) == 1 || $parts[1] == '' ) {
                return false;
            }
 
            if ( isset( $row->old_id ) && $wiki === false ) {
                // Make use of the wiki-local revision text cache
                $cache = MediaWikiServices::getInstance()->getMainWANObjectCache();
                // The cached value should be decompressed, so handle that and return here
                return $cache->getWithSetCallback(
                    $cache->makeKey( 'revisiontext', 'textid', $row->old_id ),
                    self::getCacheTTL( $cache ),
                    function () use ( $url, $wiki, $flags ) {
                        // No negative caching per Revision::loadText()
                        $text = ExternalStore::fetchFromURL( $url, [ 'wiki' => $wiki ] );
 
                        return self::decompressRevisionText( $text, $flags );
                    },
                    [ 'pcGroup' => self::TEXT_CACHE_GROUP, 'pcTTL' => $cache::TTL_PROC_LONG ]
                );
            } else {
                $text = ExternalStore::fetchFromURL( $url, [ 'wiki' => $wiki ] );
            }
        }
 
        return self::decompressRevisionText( $text, $flags );
    }
 
    public static function compressRevisionText( &$text ) {
        global $wgCompressRevisions;
        $flags = [];
 
        # Revisions not marked this way will be converted
        # on load if $wgLegacyCharset is set in the future.
        $flags[] = 'utf-8';
 
        if ( $wgCompressRevisions ) {
            if ( function_exists( 'gzdeflate' ) ) {
                $deflated = gzdeflate( $text );
 
                if ( $deflated === false ) {
                    wfLogWarning( __METHOD__ . ': gzdeflate() failed' );
                } else {
                    $text = $deflated;
                    $flags[] = 'gzip';
                }
            } else {
                wfDebug( __METHOD__ . " -- no zlib support, not compressing\n" );
            }
        }
        return implode( ',', $flags );
    }
 
    public static function decompressRevisionText( $text, $flags ) {
        global $wgLegacyEncoding, $wgContLang;
 
        if ( $text === false ) {
            // Text failed to be fetched; nothing to do
            return false;
        }
 
        if ( in_array( 'gzip', $flags ) ) {
            # Deal with optional compression of archived pages.
            # This can be done periodically via maintenance/compressOld.php, and
            # as pages are saved if $wgCompressRevisions is set.
            $text = gzinflate( $text );
 
            if ( $text === false ) {
                wfLogWarning( __METHOD__ . ': gzinflate() failed' );
                return false;
            }
        }
 
        if ( in_array( 'object', $flags ) ) {
            # Generic compressed storage
            $obj = unserialize( $text );
            if ( !is_object( $obj ) ) {
                // Invalid object
                return false;
            }
            $text = $obj->getText();
        }
 
        if ( $text !== false && $wgLegacyEncoding
            && !in_array( 'utf-8', $flags ) && !in_array( 'utf8', $flags )
        ) {
            # Old revisions kept around in a legacy encoding?
            # Upconvert on demand.
            # ("utf8" checked for compatibility with some broken
            #  conversion scripts 2008-12-30)
            $text = $wgContLang->iconv( $wgLegacyEncoding, 'UTF-8', $text );
        }
 
        return $text;
    }
 
    public function insertOn( $dbw ) {
        global $wgDefaultExternalStore, $wgContentHandlerUseDB;
 
        // We're inserting a new revision, so we have to use master anyway.
        // If it's a null revision, it may have references to rows that
        // are not in the replica yet (the text row).
        $this->mQueryFlags |= self::READ_LATEST;
 
        // Not allowed to have rev_page equal to 0, false, etc.
        if ( !$this->mPage ) {
            $title = $this->getTitle();
            if ( $title instanceof Title ) {
                $titleText = ' for page ' . $title->getPrefixedText();
            } else {
                $titleText = '';
            }
            throw new MWException( "Cannot insert revision$titleText: page ID must be nonzero" );
        }
 
        $this->checkContentModel();
 
        $data = $this->mText;
        $flags = self::compressRevisionText( $data );
 
        # Write to external storage if required
        if ( $wgDefaultExternalStore ) {
            // Store and get the URL
            $data = ExternalStore::insertToDefault( $data );
            if ( !$data ) {
                throw new MWException( "Unable to store text to external storage" );
            }
            if ( $flags ) {
                $flags .= ',';
            }
            $flags .= 'external';
        }
 
        # Record the text (or external storage URL) to the text table
        if ( $this->mTextId === null ) {
            $old_id = $dbw->nextSequenceValue( 'text_old_id_seq' );
            $dbw->insert( 'text',
                [
                    'old_id' => $old_id,
                    'old_text' => $data,
                    'old_flags' => $flags,
                ], __METHOD__
            );
            $this->mTextId = $dbw->insertId();
        }
 
        if ( $this->mComment === null ) {
            $this->mComment = "";
        }
 
        # Record the edit in revisions
        $rev_id = $this->mId !== null
            ? $this->mId
            : $dbw->nextSequenceValue( 'revision_rev_id_seq' );
        $row = [
            'rev_id'         => $rev_id,
            'rev_page'       => $this->mPage,
            'rev_text_id'    => $this->mTextId,
            'rev_comment'    => $this->mComment,
            'rev_minor_edit' => $this->mMinorEdit ? 1 : 0,
            'rev_user'       => $this->mUser,
            'rev_user_text'  => $this->mUserText,
            'rev_timestamp'  => $dbw->timestamp( $this->mTimestamp ),
            'rev_deleted'    => $this->mDeleted,
            'rev_len'        => $this->mSize,
            'rev_parent_id'  => $this->mParentId === null
                ? $this->getPreviousRevisionId( $dbw )
                : $this->mParentId,
            'rev_sha1'       => $this->mSha1 === null
                ? Revision::base36Sha1( $this->mText )
                : $this->mSha1,
        ];
 
        if ( $wgContentHandlerUseDB ) {
            // NOTE: Store null for the default model and format, to save space.
            // XXX: Makes the DB sensitive to changed defaults.
            // Make this behavior optional? Only in miser mode?
 
            $model = $this->getContentModel();
            $format = $this->getContentFormat();
 
            $title = $this->getTitle();
 
            if ( $title === null ) {
                throw new MWException( "Insufficient information to determine the title of the "
                    . "revision's page!" );
            }
 
            $defaultModel = ContentHandler::getDefaultModelFor( $title );
            $defaultFormat = ContentHandler::getForModelID( $defaultModel )->getDefaultFormat();
 
            $row['rev_content_model'] = ( $model === $defaultModel ) ? null : $model;
            $row['rev_content_format'] = ( $format === $defaultFormat ) ? null : $format;
        }
 
        $dbw->insert( 'revision', $row, __METHOD__ );
 
        $this->mId = $rev_id !== null ? $rev_id : $dbw->insertId();
 
        // Assertion to try to catch T92046
        if ( (int)$this->mId === 0 ) {
            throw new UnexpectedValueException(
                'After insert, Revision mId is ' . var_export( $this->mId, 1 ) . ': ' .
                    var_export( $row, 1 )
            );
        }
 
        // Avoid PHP 7.1 warning of passing $this by reference
        $revision = $this;
        Hooks::run( 'RevisionInsertComplete', [ &$revision, $data, $flags ] );
 
        return $this->mId;
    }
 
    protected function checkContentModel() {
        global $wgContentHandlerUseDB;
 
        // Note: may return null for revisions that have not yet been inserted
        $title = $this->getTitle();
 
        $model = $this->getContentModel();
        $format = $this->getContentFormat();
        $handler = $this->getContentHandler();
 
        if ( !$handler->isSupportedFormat( $format ) ) {
            $t = $title->getPrefixedDBkey();
 
            throw new MWException( "Can't use format $format with content model $model on $t" );
        }
 
        if ( !$wgContentHandlerUseDB && $title ) {
            // if $wgContentHandlerUseDB is not set,
            // all revisions must use the default content model and format.
 
            $defaultModel = ContentHandler::getDefaultModelFor( $title );
            $defaultHandler = ContentHandler::getForModelID( $defaultModel );
            $defaultFormat = $defaultHandler->getDefaultFormat();
 
            if ( $this->getContentModel() != $defaultModel ) {
                $t = $title->getPrefixedDBkey();
 
                throw new MWException( "Can't save non-default content model with "
                    . "\$wgContentHandlerUseDB disabled: model is $model, "
                    . "default for $t is $defaultModel" );
            }
 
            if ( $this->getContentFormat() != $defaultFormat ) {
                $t = $title->getPrefixedDBkey();
 
                throw new MWException( "Can't use non-default content format with "
                    . "\$wgContentHandlerUseDB disabled: format is $format, "
                    . "default for $t is $defaultFormat" );
            }
        }
 
        $content = $this->getContent( Revision::RAW );
        $prefixedDBkey = $title->getPrefixedDBkey();
        $revId = $this->mId;
 
        if ( !$content ) {
            throw new MWException(
                "Content of revision $revId ($prefixedDBkey) could not be loaded for validation!"
            );
        }
        if ( !$content->isValid() ) {
            throw new MWException(
                "Content of revision $revId ($prefixedDBkey) is not valid! Content model is $model"
            );
        }
    }
 
    public static function base36Sha1( $text ) {
        return Wikimedia\base_convert( sha1( $text ), 16, 36, 31 );
    }
 
    private static function getCacheTTL( WANObjectCache $cache ) {
        global $wgRevisionCacheExpiry;
 
        if ( $cache->getQoS( $cache::ATTR_EMULATION ) <= $cache::QOS_EMULATION_SQL ) {
            // Do not cache RDBMs blobs in...the RDBMs store
            $ttl = $cache::TTL_UNCACHEABLE;
        } else {
            $ttl = $wgRevisionCacheExpiry ?: $cache::TTL_UNCACHEABLE;
        }
 
        return $ttl;
    }
 
    private function loadText() {
        $cache = ObjectCache::getMainWANInstance();
 
        // No negative caching; negative hits on text rows may be due to corrupted replica DBs
        return $cache->getWithSetCallback(
            $cache->makeKey( 'revisiontext', 'textid', $this->getTextId() ),
            self::getCacheTTL( $cache ),
            function () {
                return $this->fetchText();
            },
            [ 'pcGroup' => self::TEXT_CACHE_GROUP, 'pcTTL' => $cache::TTL_PROC_LONG ]
        );
    }
 
    private function fetchText() {
        $textId = $this->getTextId();
 
        // If we kept data for lazy extraction, use it now...
        if ( $this->mTextRow !== null ) {
            $row = $this->mTextRow;
            $this->mTextRow = null;
        } else {
            $row = null;
        }
 
        // Callers doing updates will pass in READ_LATEST as usual. Since the text/blob tables
        // do not normally get rows changed around, set READ_LATEST_IMMUTABLE in those cases.
        $flags = $this->mQueryFlags;
        $flags |= DBAccessObjectUtils::hasFlags( $flags, self::READ_LATEST )
            ? self::READ_LATEST_IMMUTABLE
            : 0;
 
        list( $index, $options, $fallbackIndex, $fallbackOptions ) =
            DBAccessObjectUtils::getDBOptions( $flags );
 
        if ( !$row ) {
            // Text data is immutable; check replica DBs first.
            $row = wfGetDB( $index )->selectRow(
                'text',
                [ 'old_text', 'old_flags' ],
                [ 'old_id' => $textId ],
                __METHOD__,
                $options
            );
        }
 
        // Fallback to DB_MASTER in some cases if the row was not found
        if ( !$row && $fallbackIndex !== null ) {
            // Use FOR UPDATE if it was used to fetch this revision. This avoids missing the row
            // due to REPEATABLE-READ. Also fallback to the master if READ_LATEST is provided.
            $row = wfGetDB( $fallbackIndex )->selectRow(
                'text',
                [ 'old_text', 'old_flags' ],
                [ 'old_id' => $textId ],
                __METHOD__,
                $fallbackOptions
            );
        }
 
        if ( !$row ) {
            wfDebugLog( 'Revision', "No text row with ID '$textId' (revision {$this->getId()})." );
        }
 
        $text = self::getRevisionText( $row );
        if ( $row && $text === false ) {
            wfDebugLog( 'Revision', "No blob for text row '$textId' (revision {$this->getId()})." );
        }
 
        return is_string( $text ) ? $text : false;
    }
 
    public static function newNullRevision( $dbw, $pageId, $summary, $minor, $user = null ) {
        global $wgContentHandlerUseDB, $wgContLang;
 
        $fields = [ 'page_latest', 'page_namespace', 'page_title',
                        'rev_text_id', 'rev_len', 'rev_sha1' ];
 
        if ( $wgContentHandlerUseDB ) {
            $fields[] = 'rev_content_model';
            $fields[] = 'rev_content_format';
        }
 
        $current = $dbw->selectRow(
            [ 'page', 'revision' ],
            $fields,
            [
                'page_id' => $pageId,
                'page_latest=rev_id',
            ],
            __METHOD__,
            [ 'FOR UPDATE' ] // T51581
        );
 
        if ( $current ) {
            if ( !$user ) {
                global $wgUser;
                $user = $wgUser;
            }
 
            // Truncate for whole multibyte characters
            $summary = $wgContLang->truncate( $summary, 255 );
 
            $row = [
                'page'       => $pageId,
                'user_text'  => $user->getName(),
                'user'       => $user->getId(),
                'comment'    => $summary,
                'minor_edit' => $minor,
                'text_id'    => $current->rev_text_id,
                'parent_id'  => $current->page_latest,
                'len'        => $current->rev_len,
                'sha1'       => $current->rev_sha1
            ];
 
            if ( $wgContentHandlerUseDB ) {
                $row['content_model'] = $current->rev_content_model;
                $row['content_format'] = $current->rev_content_format;
            }
 
            $row['title'] = Title::makeTitle( $current->page_namespace, $current->page_title );
 
            $revision = new Revision( $row );
        } else {
            $revision = null;
        }
 
        return $revision;
    }
 
    public function userCan( $field, User $user = null ) {
        return self::userCanBitfield( $this->getVisibility(), $field, $user );
    }
 
    public static function userCanBitfield( $bitfield, $field, User $user = null,
        Title $title = null
    ) {
        if ( $bitfield & $field ) { // aspect is deleted
            if ( $user === null ) {
                global $wgUser;
                $user = $wgUser;
            }
            if ( $bitfield & self::DELETED_RESTRICTED ) {
                $permissions = [ 'suppressrevision', 'viewsuppressed' ];
            } elseif ( $field & self::DELETED_TEXT ) {
                $permissions = [ 'deletedtext' ];
            } else {
                $permissions = [ 'deletedhistory' ];
            }
            $permissionlist = implode( ', ', $permissions );
            if ( $title === null ) {
                wfDebug( "Checking for $permissionlist due to $field match on $bitfield\n" );
                return call_user_func_array( [ $user, 'isAllowedAny' ], $permissions );
            } else {
                $text = $title->getPrefixedText();
                wfDebug( "Checking for $permissionlist on $text due to $field match on $bitfield\n" );
                foreach ( $permissions as $perm ) {
                    if ( $title->userCan( $perm, $user ) ) {
                        return true;
                    }
                }
                return false;
            }
        } else {
            return true;
        }
    }
 
    static function getTimestampFromId( $title, $id, $flags = 0 ) {
        $db = ( $flags & self::READ_LATEST )
            ? wfGetDB( DB_MASTER )
            : wfGetDB( DB_REPLICA );
        // Casting fix for databases that can't take '' for rev_id
        if ( $id == '' ) {
            $id = 0;
        }
        $conds = [ 'rev_id' => $id ];
        $conds['rev_page'] = $title->getArticleID();
        $timestamp = $db->selectField( 'revision', 'rev_timestamp', $conds, __METHOD__ );
 
        return ( $timestamp !== false ) ? wfTimestamp( TS_MW, $timestamp ) : false;
    }
 
    static function countByPageId( $db, $id ) {
        $row = $db->selectRow( 'revision', [ 'revCount' => 'COUNT(*)' ],
            [ 'rev_page' => $id ], __METHOD__ );
        if ( $row ) {
            return $row->revCount;
        }
        return 0;
    }
 
    static function countByTitle( $db, $title ) {
        $id = $title->getArticleID();
        if ( $id ) {
            return self::countByPageId( $db, $id );
        }
        return 0;
    }
 
    public static function userWasLastToEdit( $db, $pageId, $userId, $since ) {
        if ( !$userId ) {
            return false;
        }
 
        if ( is_int( $db ) ) {
            $db = wfGetDB( $db );
        }
 
        $res = $db->select( 'revision',
            'rev_user',
            [
                'rev_page' => $pageId,
                'rev_timestamp > ' . $db->addQuotes( $db->timestamp( $since ) )
            ],
            __METHOD__,
            [ 'ORDER BY' => 'rev_timestamp ASC', 'LIMIT' => 50 ] );
        foreach ( $res as $row ) {
            if ( $row->rev_user != $userId ) {
                return false;
            }
        }
        return true;
    }
 
    public static function newKnownCurrent( IDatabase $db, $pageId, $revId ) {
        $cache = MediaWikiServices::getInstance()->getMainWANObjectCache();
        return $cache->getWithSetCallback(
            // Page/rev IDs passed in from DB to reflect history merges
            $cache->makeGlobalKey( 'revision', $db->getWikiID(), $pageId, $revId ),
            $cache::TTL_WEEK,
            function ( $curValue, &$ttl, array &$setOpts ) use ( $db, $pageId, $revId ) {
                $setOpts += Database::getCacheSetOptions( $db );
 
                $rev = Revision::loadFromPageId( $db, $pageId, $revId );
                // Reflect revision deletion and user renames
                if ( $rev ) {
                    $rev->mTitle = null; // mutable; lazy-load
                    $rev->mRefreshMutableFields = true;
                }
 
                return $rev ?: false; // don't cache negatives
            }
        );
    }
 
    private function loadMutableFields() {
        if ( !$this->mRefreshMutableFields ) {
            return; // not needed
        }
 
        $this->mRefreshMutableFields = false;
        $dbr = wfGetLB( $this->mWiki )->getConnectionRef( DB_REPLICA, [], $this->mWiki );
        $row = $dbr->selectRow(
            [ 'revision', 'user' ],
            [ 'rev_deleted', 'user_name' ],
            [ 'rev_id' => $this->mId, 'user_id = rev_user' ],
            __METHOD__
        );
        if ( $row ) { // update values
            $this->mDeleted = (int)$row->rev_deleted;
            $this->mUserText = $row->user_name;
        }
    }
}