Category.php

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<?php
class Category {
    private $mName = null;
    private $mID = null;
    private $mTitle = null;
    private $mPages = null, $mSubcats = null, $mFiles = null;

    private function __construct() {
    }

    protected function initialize() {
        if ( $this->mName === null && $this->mID === null ) {
            throw new MWException( __METHOD__ . ' has both names and IDs null' );
        } elseif ( $this->mID === null ) {
            $where = [ 'cat_title' => $this->mName ];
        } elseif ( $this->mName === null ) {
            $where = [ 'cat_id' => $this->mID ];
        } else {
            # Already initialized
            return true;
        }

        $dbr = wfGetDB( DB_REPLICA );
        $row = $dbr->selectRow(
            'category',
            [ 'cat_id', 'cat_title', 'cat_pages', 'cat_subcats', 'cat_files' ],
            $where,
            __METHOD__
        );

        if ( !$row ) {
            # Okay, there were no contents.  Nothing to initialize.
            if ( $this->mTitle ) {
                # If there is a title object but no record in the category table,
                # treat this as an empty category.
                $this->mID = false;
                $this->mName = $this->mTitle->getDBkey();
                $this->mPages = 0;
                $this->mSubcats = 0;
                $this->mFiles = 0;

                # If the title exists, call refreshCounts to add a row for it.
                if ( $this->mTitle->exists() ) {
                    DeferredUpdates::addCallableUpdate( [ $this, 'refreshCounts' ] );
                }

                return true;
            } else {
                return false; # Fail
            }
        }

        $this->mID = $row->cat_id;
        $this->mName = $row->cat_title;
        $this->mPages = $row->cat_pages;
        $this->mSubcats = $row->cat_subcats;
        $this->mFiles = $row->cat_files;

        # (bug 13683) If the count is negative, then 1) it's obviously wrong
        # and should not be kept, and 2) we *probably* don't have to scan many
        # rows to obtain the correct figure, so let's risk a one-time recount.
        if ( $this->mPages < 0 || $this->mSubcats < 0 || $this->mFiles < 0 ) {
            $this->mPages = max( $this->mPages, 0 );
            $this->mSubcats = max( $this->mSubcats, 0 );
            $this->mFiles = max( $this->mFiles, 0 );

            DeferredUpdates::addCallableUpdate( [ $this, 'refreshCounts' ] );
        }

        return true;
    }

    public static function newFromName( $name ) {
        $cat = new self();
        $title = Title::makeTitleSafe( NS_CATEGORY, $name );

        if ( !is_object( $title ) ) {
            return false;
        }

        $cat->mTitle = $title;
        $cat->mName = $title->getDBkey();

        return $cat;
    }

    public static function newFromTitle( $title ) {
        $cat = new self();

        $cat->mTitle = $title;
        $cat->mName = $title->getDBkey();

        return $cat;
    }

    public static function newFromID( $id ) {
        $cat = new self();
        $cat->mID = intval( $id );
        return $cat;
    }

    public static function newFromRow( $row, $title = null ) {
        $cat = new self();
        $cat->mTitle = $title;

        # NOTE: the row often results from a LEFT JOIN on categorylinks. This may result in
        #       all the cat_xxx fields being null, if the category page exists, but nothing
        #       was ever added to the category. This case should be treated link an empty
        #       category, if possible.

        if ( $row->cat_title === null ) {
            if ( $title === null ) {
                # the name is probably somewhere in the row, for example as page_title,
                # but we can't know that here...
                return false;
            } else {
                # if we have a title object, fetch the category name from there
                $cat->mName = $title->getDBkey();
            }

            $cat->mID = false;
            $cat->mSubcats = 0;
            $cat->mPages = 0;
            $cat->mFiles = 0;
        } else {
            $cat->mName = $row->cat_title;
            $cat->mID = $row->cat_id;
            $cat->mSubcats = $row->cat_subcats;
            $cat->mPages = $row->cat_pages;
            $cat->mFiles = $row->cat_files;
        }

        return $cat;
    }

    public function getName() {
        return $this->getX( 'mName' );
    }

    public function getID() {
        return $this->getX( 'mID' );
    }

    public function getPageCount() {
        return $this->getX( 'mPages' );
    }

    public function getSubcatCount() {
        return $this->getX( 'mSubcats' );
    }

    public function getFileCount() {
        return $this->getX( 'mFiles' );
    }

    public function getTitle() {
        if ( $this->mTitle ) {
            return $this->mTitle;
        }

        if ( !$this->initialize() ) {
            return false;
        }

        $this->mTitle = Title::makeTitleSafe( NS_CATEGORY, $this->mName );
        return $this->mTitle;
    }

    public function getMembers( $limit = false, $offset = '' ) {

        $dbr = wfGetDB( DB_REPLICA );

        $conds = [ 'cl_to' => $this->getName(), 'cl_from = page_id' ];
        $options = [ 'ORDER BY' => 'cl_sortkey' ];

        if ( $limit ) {
            $options['LIMIT'] = $limit;
        }

        if ( $offset !== '' ) {
            $conds[] = 'cl_sortkey > ' . $dbr->addQuotes( $offset );
        }

        $result = TitleArray::newFromResult(
            $dbr->select(
                [ 'page', 'categorylinks' ],
                [ 'page_id', 'page_namespace', 'page_title', 'page_len',
                    'page_is_redirect', 'page_latest' ],
                $conds,
                __METHOD__,
                $options
            )
        );

        return $result;
    }

    private function getX( $key ) {
        if ( !$this->initialize() ) {
            return false;
        }
        return $this->{$key};
    }

    public function refreshCounts() {
        if ( wfReadOnly() ) {
            return false;
        }

        # If we have just a category name, find out whether there is an
        # existing row. Or if we have just an ID, get the name, because
        # that's what categorylinks uses.
        if ( !$this->initialize() ) {
            return false;
        }

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

        $cond1 = $dbw->conditional( [ 'page_namespace' => NS_CATEGORY ], 1, 'NULL' );
        $cond2 = $dbw->conditional( [ 'page_namespace' => NS_FILE ], 1, 'NULL' );
        $result = $dbw->selectRow(
            [ 'categorylinks', 'page' ],
            [ 'pages' => 'COUNT(*)',
                'subcats' => "COUNT($cond1)",
                'files' => "COUNT($cond2)"
            ],
            [ 'cl_to' => $this->mName, 'page_id = cl_from' ],
            __METHOD__,
            [ 'LOCK IN SHARE MODE' ]
        );

        $shouldExist = $result->pages > 0 || $this->getTitle()->exists();

        if ( $this->mID ) {
            if ( $shouldExist ) {
                # The category row already exists, so do a plain UPDATE instead
                # of INSERT...ON DUPLICATE KEY UPDATE to avoid creating a gap
                # in the cat_id sequence. The row may or may not be "affected".
                $dbw->update(
                    'category',
                    [
                        'cat_pages' => $result->pages,
                        'cat_subcats' => $result->subcats,
                        'cat_files' => $result->files
                    ],
                    [ 'cat_title' => $this->mName ],
                    __METHOD__
                );
            } else {
                # The category is empty and has no description page, delete it
                $dbw->delete(
                    'category',
                    [ 'cat_title' => $this->mName ],
                    __METHOD__
                );
                $this->mID = false;
            }
        } elseif ( $shouldExist ) {
            # The category row doesn't exist but should, so create it. Use
            # upsert in case of races.
            $dbw->upsert(
                'category',
                [
                    'cat_title' => $this->mName,
                    'cat_pages' => $result->pages,
                    'cat_subcats' => $result->subcats,
                    'cat_files' => $result->files
                ],
                [ 'cat_title' ],
                [
                    'cat_pages' => $result->pages,
                    'cat_subcats' => $result->subcats,
                    'cat_files' => $result->files
                ],
                __METHOD__
            );
            // @todo: Should we update $this->mID here? Or not since Category
            // objects tend to be short lived enough to not matter?
        }

        $dbw->endAtomic( __METHOD__ );

        # Now we should update our local counts.
        $this->mPages = $result->pages;
        $this->mSubcats = $result->subcats;
        $this->mFiles = $result->files;

        return true;
    }
}