includes/specials/SpecialRandompage.php

   1 <?php
   2
   3 /**
   4  * Special page to direct the user to a random page
   5  *
   6  * @ingroup SpecialPage
   7  * @author Rob Church <robchur@gmail.com>, Ilmari Karonen
   8  * @license GNU General Public Licence 2.0 or later
   9  */
  10 class RandomPage extends SpecialPage {
  11         private $namespaces;  // namespaces to select pages from
  12
  13         function __construct( $name = 'Randompage' ){
  14                 global $wgContentNamespaces;
  15
  16                 $this->namespaces = $wgContentNamespaces;
  17
  18                 parent::__construct( $name );
  19         }
  20
  21         public function getNamespaces() {
  22                 return $this->namespaces;
  23         }
  24
  25         public function setNamespace ( $ns ) {
  26                 if( !$ns || $ns < NS_MAIN ) $ns = NS_MAIN;
  27                 $this->namespaces = array( $ns );
  28         }
  29
  30         // select redirects instead of normal pages?
  31         // Overriden by SpecialRandomredirect
  32         public function isRedirect(){
  33                 return false;
  34         }
  35
  36         public function execute( $par ) {
  37                 global $wgOut, $wgContLang;
  38
  39                 if ($par) {
  40                         $this->setNamespace( $wgContLang->getNsIndex( $par ) );
  41                 }
  42
  43                 $title = $this->getRandomTitle();
  44
  45                 if( is_null( $title ) ) {
  46                         $this->setHeaders();
  47                         $wgOut->addWikiMsg( strtolower( $this->mName ) . '-nopages',  $wgContLang->getNsText( $this->namespace ) );
  48                         return;
  49                 }
  50
  51                 $query = $this->isRedirect() ? 'redirect=no' : '';
  52                 $wgOut->redirect( $title->getFullUrl( $query ) );
  53         }
  54
  55
  56         /**
  57          * Choose a random title.
  58          * @return Title object (or null if nothing to choose from)
  59          */
  60         public function getRandomTitle() {
  61                 $randstr = wfRandom();
  62                 $row = $this->selectRandomPageFromDB( $randstr );
  63
  64                 /* If we picked a value that was higher than any in
  65                  * the DB, wrap around and select the page with the
  66                  * lowest value instead!  One might think this would
  67                  * skew the distribution, but in fact it won't cause
  68                  * any more bias than what the page_random scheme
  69                  * causes anyway.  Trust me, I'm a mathematician. :)
  70                  */
  71                 if( !$row )
  72                         $row = $this->selectRandomPageFromDB( "0" );
  73
  74                 if( $row )
  75                         return Title::makeTitleSafe( $row->page_namespace, $row->page_title );
  76                 else
  77                         return null;
  78         }
  79
  80         private function selectRandomPageFromDB( $randstr ) {
  81                 global $wgExtraRandompageSQL;
  82                 $dbr = wfGetDB( DB_SLAVE );
  83
  84                 $use_index = $dbr->useIndexClause( 'page_random' );
  85                 $page = $dbr->tableName( 'page' );
  86
  87                 $ns = implode( ",", $this->namespaces );
  88                 $redirect = $this->isRedirect() ? 1 : 0;
  89
  90                 $extra = $wgExtraRandompageSQL ? "AND ($wgExtraRandompageSQL)" : "";
  91                 $extra .= $this->addExtraSQL() ? "AND (".$this->addExtraSQL().")" : "";
  92                 $sql = "SELECT page_title, page_namespace
  93                         FROM $page $use_index
  94                         WHERE page_namespace IN ( $ns )
  95                         AND page_is_redirect = $redirect
  96                         AND page_random >= $randstr
  97                         $extra
  98                         ORDER BY page_random";
  99
 100                 $sql = $dbr->limitResult( $sql, 1, 0 );
 101                 $res = $dbr->query( $sql, __METHOD__ );
 102                 return $dbr->fetchObject( $res );
 103         }
 104
 105         // an alternative to $wgExtraRandompageSQL so extensions
 106         // can add their own SQL by overriding this function
 107         public function addExtraSQL() {
 108                 return '';
 109         }
 110 }