<?php
/**
 * Cache for article titles (prefixed DB keys) and ids linked from one source
 * @package MediaWiki
 * @subpackage Cache
 */

/**
 *
 */
# These are used in incrementalSetup()
define ('LINKCACHE_GOOD', 0);
define ('LINKCACHE_BAD', 1);
define ('LINKCACHE_IMAGE', 2);
define ('LINKCACHE_PAGE', 3);

/**
 * @package MediaWiki
 * @subpackage Cache
 */
class LinkCache {	
	// Increment $mClassVer whenever old serialized versions of this class
	// becomes incompatible with the new version.
	/* private */ var $mClassVer = 3;

	/* private */ var $mPageLinks;
	/* private */ var $mGoodLinks, $mBadLinks, $mActive;
	/* private */ var $mImageLinks, $mCategoryLinks;
	/* private */ var $mPreFilled, $mOldGoodLinks, $mOldBadLinks;
	/* private */ var $mForUpdate;

	/* private */ function getKey( $title ) {
		global $wgDBname;
		return $wgDBname.':lc:title:'.$title;
	}
	
	function LinkCache() {
		$this->mActive = true;
		$this->mPreFilled = false;
		$this->mForUpdate = false;
		$this->mPageLinks = array();
		$this->mGoodLinks = array();
		$this->mBadLinks = array();
		$this->mImageLinks = array();
		$this->mCategoryLinks = array();
		$this->mOldGoodLinks = array();
		$this->mOldBadLinks = array();
		$this->mOldPageLinks = array();
	}

	/**
	 * General accessor to get/set whether SELECT FOR UPDATE should be used
	 */
	function forUpdate( $update = NULL ) { 
		return wfSetVar( $this->mForUpdate, $update );
	}
	
	function getGoodLinkID( $title ) {
		if ( array_key_exists( $title, $this->mGoodLinks ) ) {
			return $this->mGoodLinks[$title];
		} else {
			return 0;
		}
	}

	function isBadLink( $title ) {
		return array_key_exists( $title, $this->mBadLinks ); 
	}

	function addGoodLinkObj( $id, $title ) {
		if ( $this->mActive ) {
			$dbkey = $title->getPrefixedDbKey();
			$this->mGoodLinks[$dbkey] = $id;
			$this->mPageLinks[$dbkey] = $title;
		}
	}

	function addBadLinkObj( $title ) {
		$dbkey = $title->getPrefixedDbKey();
		if ( $this->mActive && ( ! $this->isBadLink( $dbkey ) ) ) {
			$this->mBadLinks[$dbkey] = 1;
			$this->mPageLinks[$dbkey] = $title;
		}
	}

	function addImageLink( $title ) {
		if ( $this->mActive ) { $this->mImageLinks[$title] = 1; }
	}

	function addImageLinkObj( $nt ) {
		if ( $this->mActive ) { $this->mImageLinks[$nt->getDBkey()] = 1; }
	}
	
	function addCategoryLink( $title, $sortkey ) {
		if ( $this->mActive ) { $this->mCategoryLinks[$title] = $sortkey; }
	}
	
	function addCategoryLinkObj( &$nt, $sortkey ) {
		$this->addCategoryLink( $nt->getDBkey(), $sortkey );
	}

	function clearBadLink( $title ) {
		unset( $this->mBadLinks[$title] );
		$this->clearLink( $title );
	}
	
	function clearLink( $title ) {
		global $wgMemc, $wgLinkCacheMemcached;
		if( $wgLinkCacheMemcached )
			$wgMemc->delete( $this->getKey( $title ) );
	}

	function suspend() { $this->mActive = false; }
	function resume() { $this->mActive = true; }
	function getPageLinks() { return $this->mPageLinks; }
	function getGoodLinks() { return $this->mGoodLinks; }
	function getBadLinks() { return array_keys( $this->mBadLinks ); }
	function getImageLinks() { return $this->mImageLinks; }
	function getCategoryLinks() { return $this->mCategoryLinks; }

	function addLink( $title ) {
		$nt = Title::newFromDBkey( $title );
		if( $nt ) {
			return $this->addLinkObj( $nt );
		} else {
			return 0;
		}
	}
	
	function addLinkObj( &$nt ) {
		global $wgMemc, $wgLinkCacheMemcached, $wgAntiLockFlags;
		$title = $nt->getPrefixedDBkey();
		if ( $this->isBadLink( $title ) ) { return 0; }		
		$id = $this->getGoodLinkID( $title );
		if ( 0 != $id ) { return $id; }

		$fname = 'LinkCache::addLinkObj';
		wfProfileIn( $fname );

		$ns = $nt->getNamespace();
		$t = $nt->getDBkey();

		if ( '' == $title ) { 
			wfProfileOut( $fname );
			return 0; 
		}
		
		$id = NULL;
		if( $wgLinkCacheMemcached )
			$id = $wgMemc->get( $key = $this->getKey( $title ) );
		if( ! is_integer( $id ) ) {
			if ( $this->mForUpdate ) {
				$db =& wfGetDB( DB_MASTER );
				if ( !( $wgAntiLockFlags & ALF_NO_LINK_LOCK ) ) {
					$options = array( 'FOR UPDATE' );
				}
			} else {
				$db =& wfGetDB( DB_SLAVE );
				$options = array();
			}

			$id = $db->selectField( 'page', 'page_id', array( 'page_namespace' => $ns, 'page_title' => $t ), $fname, $options );
			if ( !$id ) {
				$id = 0;
			}
			if( $wgLinkCacheMemcached )
				$wgMemc->add( $key, $id, 3600*24 );
		}
		
		if( 0 == $id ) {
			$this->addBadLinkObj( $nt );
		} else {
			$this->addGoodLinkObj( $id, $nt );
		}
		wfProfileOut( $fname );
		return $id;
	}

	/**
	 * Bulk-check the pagelinks and page arrays for existence info.
	 * @param Title $fromtitle
	 */
	function preFill( &$fromtitle ) {
		global $wgAntiLockFlags;
		$fname = 'LinkCache::preFill';
		wfProfileIn( $fname );

		$this->suspend();
		$id = $fromtitle->getArticleID();
		$this->resume();
		
		if( $id == 0 ) {
			wfDebug( "$fname - got id 0 for title '" . $fromtitle->getPrefixedDBkey() . "'\n" );
			wfProfileOut( $fname );
			return;
		}
		
		if ( $this->mForUpdate ) {
			$db =& wfGetDB( DB_MASTER );
			if ( !( $wgAntiLockFlags & ALF_NO_LINK_LOCK ) ) {
				$options = 'FOR UPDATE';
			} else {
				$options = '';
			}
		} else {
			$db =& wfGetDB( DB_SLAVE );
			$options = '';
		}

		$page = $db->tableName( 'page' );
		$pagelinks = $db->tableName( 'pagelinks' );

		$sql = "SELECT page_id,pl_namespace,pl_title
			FROM $pagelinks
			LEFT JOIN $page
			ON pl_namespace=page_namespace AND pl_title=page_title
			WHERE pl_from=$id $options";
		$res = $db->query( $sql, $fname );
		while( $s = $db->fetchObject( $res ) ) {
			$title = Title::makeTitle( $s->pl_namespace, $s->pl_title );
			if( $s->page_id ) {
				$this->addGoodLinkObj( $s->page_id, $title );
			} else {
				$this->addBadLinkObj( $title );
			}
		}
		$this->mPreFilled = true;

		wfProfileOut( $fname );
	}

	function getGoodAdditions() {
		return array_diff( $this->mGoodLinks, $this->mOldGoodLinks );
	}

	function getBadAdditions() {
		#wfDebug( "mOldBadLinks: " . implode( ', ', array_keys( $this->mOldBadLinks ) ) . "\n" );
		#wfDebug( "mBadLinks: " . implode( ', ', array_keys( $this->mBadLinks ) ) . "\n" );
		return array_values( array_diff( array_keys( $this->mBadLinks ), array_keys( $this->mOldBadLinks ) ) );
	}

	function getImageAdditions() {
		return array_diff_assoc( $this->mImageLinks, $this->mOldImageLinks );
	}

	function getGoodDeletions() {
		return array_diff( $this->mOldGoodLinks, $this->mGoodLinks );
	}

	function getBadDeletions() {
		return array_values( array_diff( array_keys( $this->mOldBadLinks ), array_keys( $this->mBadLinks ) ));
	}

	function getImageDeletions() {
		return array_diff_assoc( $this->mOldImageLinks, $this->mImageLinks );
	}
	
	function getPageAdditions() {
		$set = array_diff( array_keys( $this->mPageLinks ), array_keys( $this->mOldPageLinks ) );
		$out = array();
		foreach( $set as $key ) {
			$out[$key] = $this->mPageLinks[$key];
		}
		return $out;
	}
	
	function getPageDeletions() {
		$set = array_diff( array_keys( $this->mOldPageLinks ), array_keys( $this->mPageLinks ) );
		$out = array();
		foreach( $set as $key ) {
			$out[$key] = $this->mOldPageLinks[$key];
		}
		return $out;
	}

	/**
	 * Parameters:
	 * @param $which is one of the LINKCACHE_xxx constants
	 * @param $del,$add are the incremental update arrays which will be filled.
	 *
	 * @return Returns whether or not it's worth doing the incremental version.
	 *
	 * For example, if [[List of mathematical topics]] was blanked,
	 * it would take a long, long time to do incrementally.
	 */
	function incrementalSetup( $which, &$del, &$add ) {
		if ( ! $this->mPreFilled ) {
			return false;
		}

		switch ( $which ) {
			case LINKCACHE_GOOD:
				$old =& $this->mOldGoodLinks;
				$cur =& $this->mGoodLinks;
				$del = $this->getGoodDeletions();
				$add = $this->getGoodAdditions();
				break;
			case LINKCACHE_BAD:
				$old =& $this->mOldBadLinks;
				$cur =& $this->mBadLinks;
				$del = $this->getBadDeletions();
				$add = $this->getBadAdditions();
				break;
			case LINKCACHE_PAGE:
				$old =& $this->mOldPageLinks;
				$cur =& $this->mPageLinks;
				$del = $this->getPageDeletions();
				$add = $this->getPageAdditions();
				break;
			default: # LINKCACHE_IMAGE
				return false;		
		}
		
		return true;
	}

	/**
	 * Clears cache 
	 */
	function clear() {
		$this->mPageLinks = array();
		$this->mGoodLinks = array();
		$this->mBadLinks = array();
		$this->mImageLinks = array();
		$this->mCategoryLinks = array();
		$this->mOldGoodLinks = array();
		$this->mOldBadLinks = array();
		$this->mOldPageLinks = array();
	}

	/**
	 * Swaps old and current link registers
	 */
	function swapRegisters() {
		swap( $this->mGoodLinks, $this->mOldGoodLinks );
		swap( $this->mBadLinks, $this->mOldBadLinks );
		swap( $this->mImageLinks, $this->mOldImageLinks );
		swap( $this->mPageLinks, $this->mOldPageLinks );
	}
}

/**
 * Class representing a list of titles
 * The execute() method checks them all for existence and adds them to a LinkCache object
 +
 * @package MediaWiki
 * @subpackage Cache
 */
class LinkBatch {
	/** 
	 * 2-d array, first index namespace, second index dbkey, value arbitrary
	 */
	var $data = array();

	function LinkBatch( $arr = array() ) {
		foreach( $arr as $item ) {
			$this->addObj( $item );
		}
	}
	
	function addObj( $title ) {
		$this->add( $title->getNamespace(), $title->getDBkey() );
	}

	function add( $ns, $dbkey ) {
		if ( $ns < 0 ) {
			return;
		}
		if ( !array_key_exists( $ns, $this->data ) ) {
			$this->data[$ns] = array();
		}

		$this->data[$ns][$dbkey] = 1;
	}

	function execute( &$cache ) {
		$fname = 'LinkBatch::execute';
		$namespaces = array();

		if ( !count( $this->data ) ) {
			return;
		}

		wfProfileIn( $fname );

		// Construct query
		// This is very similar to Parser::replaceLinkHolders
		$dbr = wfGetDB( DB_SLAVE );
		$page = $dbr->tableName( 'page' );
		$sql = "SELECT page_id, page_namespace, page_title FROM $page WHERE "
			. $this->constructSet( 'page', $dbr );
		
		// Do query
		$res = $dbr->query( $sql, $fname );

		// Process results
		// For each returned entry, add it to the list of good links, and remove it from $remaining

		$remaining = $this->data;
		while ( $row = $dbr->fetchObject( $res ) ) {
			$title = Title::makeTitle( $row->page_namespace, $row->page_title );
			$cache->addGoodLinkObj( $row->page_id, $title );
			unset( $remaining[$row->page_namespace][$row->page_title] );
		}
		$dbr->freeResult( $res );

		// The remaining links in $data are bad links, register them as such
		foreach ( $remaining as $ns => $dbkeys ) {
			foreach ( $dbkeys as $dbkey => $nothing ) {
				$title = Title::makeTitle( $ns, $dbkey );
				$cache->addBadLinkObj( $title );
			}
		}

		wfProfileOut( $fname );
	}
	
	/**
	 * Construct a WHERE clause which will match all the given titles.
	 * Give the appropriate table's field name prefix ('page', 'pl', etc).
	 *
	 * @param string $prefix
	 * @return string
	 * @access public
	 */
	function constructSet( $prefix, $db ) {
		$first = true;
		$sql = '';
		foreach ( $this->data as $ns => $dbkeys ) {
			if ( !count( $dbkeys ) ) {
				continue;
			}

			if ( $first ) {
				$first = false;
			} else {
				$sql .= ' OR ';
			}
			$sql .= "({$prefix}_namespace=$ns AND {$prefix}_title IN (";

			$firstTitle = true;
			foreach( $dbkeys as $dbkey => $nothing ) {
				if ( $firstTitle ) {
					$firstTitle = false;
				} else {
					$sql .= ',';
				}
				$sql .= $db->addQuotes( $dbkey );
			}

			$sql .= '))';
		}
		return $sql;
	}
}

?>