includes/SpecialRandompage.php

   1 <?php
   2
   3 /**
   4  * Special page to direct the user to a random page
   5  *
   6  * @addtogroup SpecialPage
   7  * @author Rob Church <robchur@gmail.com>, Ilmari Karonen
   8  * @license GNU General Public Licence 2.0 or later
   9  */
  10
  11 /**
  12  * Main execution point
  13  * @param $par Namespace to select the page from
  14  */
  15 function wfSpecialRandompage( $par = null ) {
  16         global $wgOut, $wgContLang;
  17
  18         $rnd = new RandomPage();
  19         $rnd->setNamespace( $wgContLang->getNsIndex( $par ) );
  20         $rnd->setRedirect( false );
  21
  22         $title = $rnd->getRandomTitle();
  23
  24         if( is_null( $title ) ) {
  25                 $wgOut->addWikiText( wfMsg( 'randompage-nopages' ) );
  26                 return;
  27         }
  28
  29         $wgOut->reportTime();
  30         $wgOut->redirect( $title->getFullUrl() );
  31 }
  32
  33
  34 class RandomPage {
  35         private $namespace = NS_MAIN;  // namespace to select pages from
  36         private $redirect = false;     // select redirects instead of normal pages?
  37
  38         public function getNamespace ( ) {
  39                 return $this->namespace;
  40         }
  41         public function setNamespace ( $ns ) {
  42                 if( $ns < NS_MAIN ) $ns = NS_MAIN;
  43                 $this->namespace = $ns;
  44         }
  45         public function getRedirect ( ) {
  46                 return $this->redirect;
  47         }
  48         public function setRedirect ( $redirect ) {
  49                 $this->redirect = $redirect;
  50         }
  51
  52         /**
  53          * Choose a random title.
  54          * @return Title object (or null if nothing to choose from)
  55          */
  56         public function getRandomTitle ( ) {
  57                 $randstr = wfRandom();
  58                 $row = $this->selectRandomPageFromDB( $randstr );
  59
  60                 /* If we picked a value that was higher than any in
  61                  * the DB, wrap around and select the page with the
  62                  * lowest value instead!  One might think this would
  63                  * skew the distribution, but in fact it won't cause
  64                  * any more bias than what the page_random scheme
  65                  * causes anyway.  Trust me, I'm a mathematician. :)
  66                  */
  67                 if( !$row )
  68                         $row = $this->selectRandomPageFromDB( "0" );
  69
  70                 if( $row )
  71                         return Title::makeTitleSafe( $this->namespace, $row->page_title );
  72                 else
  73                         return null;
  74         }
  75
  76         private function selectRandomPageFromDB ( $randstr ) {
  77                 global $wgExtraRandompageSQL;
  78                 $fname = 'RandomPage::selectRandomPageFromDB';
  79
  80                 $dbr = wfGetDB( DB_SLAVE );
  81
  82                 $use_index = $dbr->useIndexClause( 'page_random' );
  83                 $page = $dbr->tableName( 'page' );
  84
  85                 $ns = (int) $this->namespace;
  86                 $redirect = $this->redirect ? 1 : 0;
  87
  88                 $extra = $wgExtraRandompageSQL ? "AND ($wgExtraRandompageSQL)" : "";
  89                 $sql = "SELECT page_title
  90                         FROM $page $use_index
  91                         WHERE page_namespace = $ns
  92                         AND page_is_redirect = $redirect
  93                         AND page_random >= $randstr
  94                         $extra
  95                         ORDER BY page_random";
  96
  97                 $sql = $dbr->limitResult( $sql, 1, 0 );
  98                 $res = $dbr->query( $sql, $fname );
  99                 return $dbr->fetchObject( $res );
 100         }
 101 }
 102
 103 ?>