<?php
/**
 * @file
 * Interwiki table entry
 */

/**
 * The interwiki class
 * All information is loaded on creation when called by Interwiki::fetch( $prefix ).
 * All work is done on slave, because this should *never* change (except during schema updates etc, which arent wiki-related)
 */
class Interwiki {

	// Cache - removes oldest entry when it hits limit
	protected static $smCache = array();
	const CACHE_LIMIT = 100; // 0 means unlimited, any other value is max number of entries.

	protected $mPrefix, $mURL, $mLocal, $mTrans;

	public function __construct( $prefix = null, $url = '', $local = 0, $trans = 0 ) {
		$this->mPrefix = $prefix;
		$this->mURL = $url;
		$this->mLocal = $local;
		$this->mTrans = $trans;
	}

	/**
	 * Check whether an interwiki prefix exists
	 *
	 * @param $prefix String: interwiki prefix to use
	 * @return Boolean: whether it exists
	 */
	static public function isValidInterwiki( $prefix ) {
		$result = self::fetch( $prefix );
		return (bool)$result;
	}

	/**
	 * Fetch an Interwiki object
	 *
	 * @param $prefix String: interwiki prefix to use
	 * @return Interwiki Object, or null if not valid
	 */
	static public function fetch( $prefix ) {
		global $wgContLang;
		if( $prefix == '' ) {
			return null;
		}
		$prefix = $wgContLang->lc( $prefix );
		if( isset( self::$smCache[$prefix] ) ) {
			return self::$smCache[$prefix];
		}
		global $wgInterwikiCache;
		if( $wgInterwikiCache ) {
			$iw = Interwiki::getInterwikiCached( $prefix );
		} else {
			$iw = Interwiki::load( $prefix );
			if( !$iw ) {
				$iw = false;
			}
		}
		if( self::CACHE_LIMIT && count( self::$smCache ) >= self::CACHE_LIMIT ) {
			reset( self::$smCache );
			unset( self::$smCache[ key( self::$smCache ) ] );
		}
		self::$smCache[$prefix] = $iw;
		return $iw;
	}

	/**
	 * Fetch interwiki prefix data from local cache in constant database.
	 *
	 * @note More logic is explained in DefaultSettings.
	 *
	 * @param $prefix String: interwiki prefix
	 * @return Interwiki object
	 */
	protected static function getInterwikiCached( $prefix ) {
		$value = self::getInterwikiCacheEntry( $prefix );

		$s = new Interwiki( $prefix );
		if ( $value != '' ) {
			// Split values
			list( $local, $url ) = explode( ' ', $value, 2 );
			$s->mURL = $url;
			$s->mLocal = (int)$local;
		} else {
			$s = false;
		}
		return $s;
	}

	/**
	 * Get entry from interwiki cache
	 *
	 * @note More logic is explained in DefaultSettings.
	 *
	 * @param $prefix String: database key
	 * @return String: the entry
	 */
	protected static function getInterwikiCacheEntry( $prefix ) {
		global $wgInterwikiCache, $wgInterwikiScopes, $wgInterwikiFallbackSite;
		static $db, $site;

		wfDebug( __METHOD__ . "( $prefix )\n" );
		if( !$db ) {
			$db = CdbReader::open( $wgInterwikiCache );
		}
		/* Resolve site name */
		if( $wgInterwikiScopes>=3 && !$site ) {
			$site = $db->get( '__sites:' . wfWikiID() );
			if ( $site == '' ) {
				$site = $wgInterwikiFallbackSite;
			}
		}

		$value = $db->get( wfMemcKey( $prefix ) );
		// Site level
		if ( $value == '' && $wgInterwikiScopes >= 3 ) {
			$value = $db->get( "_{$site}:{$prefix}" );
		}
		// Global Level
		if ( $value == '' && $wgInterwikiScopes >= 2 ) {
			$value = $db->get( "__global:{$prefix}" );
		}
		if ( $value == 'undef' )
			$value = '';

		return $value;
	}

	/**
	 * Load the interwiki, trying first memcached then the DB
	 *
	 * @param $prefix The interwiki prefix
	 * @return Boolean: the prefix is valid
	 */
	protected static function load( $prefix ) {
		global $wgMemc, $wgInterwikiExpiry;
		$key = wfMemcKey( 'interwiki', $prefix );
		$mc = $wgMemc->get( $key );
		$iw = false;
		if( $mc && is_array( $mc ) ) { // is_array is hack for old keys
			$iw = Interwiki::loadFromArray( $mc );
			if( $iw ) {
				return $iw;
			}
		}

		$db = wfGetDB( DB_SLAVE );

		$row = $db->fetchRow( $db->select( 'interwiki', '*', array( 'iw_prefix' => $prefix ),
			__METHOD__ ) );
		$iw = Interwiki::loadFromArray( $row );
		if ( $iw ) {
			$mc = array( 'iw_url' => $iw->mURL, 'iw_local' => $iw->mLocal, 'iw_trans' => $iw->mTrans );
			$wgMemc->add( $key, $mc, $wgInterwikiExpiry );
			return $iw;
		}

		return false;
	}

	/**
	 * Fill in member variables from an array (e.g. memcached result, Database::fetchRow, etc)
	 *
	 * @param $mc Associative array: row from the interwiki table
	 * @return Boolean: whether everything was there
	 */
	protected static function loadFromArray( $mc ) {
		if( isset( $mc['iw_url'] ) && isset( $mc['iw_local'] ) && isset( $mc['iw_trans'] ) ) {
			$iw = new Interwiki();
			$iw->mURL = $mc['iw_url'];
			$iw->mLocal = $mc['iw_local'];
			$iw->mTrans = $mc['iw_trans'];
			return $iw;
		}
		return false;
	}

	/**
	 * Get the URL for a particular title (or with $1 if no title given)
	 * 
	 * @param $title String: what text to put for the article name
	 * @return String: the URL
	 */
	public function getURL( $title = null ) {
		$url = $this->mURL;
		if( $title != null ) {
			$url = str_replace( "$1", $title, $url );
		}
		return $url;
	}

	/**
	 * Is this a local link from a sister project, or is
	 * it something outside, like Google
	 *
	 * @return Boolean
	 */
	public function isLocal() {
		return $this->mLocal;
	}

	/**
	 * Can pages from this wiki be transcluded?
	 * Still requires $wgEnableScaryTransclusion
	 *
	 * @return Boolean
	 */
	public function isTranscludable() {
		return $this->mTrans;
	}

	/**
	 * Get the name for the interwiki site
	 *
	 * @return String
	 */
	public function getName() {
		$key = 'interwiki-name-' . $this->mPrefix;
		$msg = wfMsgForContent( $key );
		return wfEmptyMsg( $key, $msg ) ? '' : $msg;
	}

	/**
	 * Get a description for this interwiki
	 *
	 * @return String
	 */
	public function getDescription() {
		$key = 'interwiki-desc-' . $this->mPrefix;
		$msg = wfMsgForContent( $key );
		return wfEmptyMsg( $key, $msg ) ? '' : $msg;
	}
}
