");
        // print("found subPrefix $subPrefix\n");
        // print_r($imageStacks);
        // die(0);
        
        function subPrefixSort($imageStackA, $imageStackB) {
            return strcmp($imageStackA['subPrefix'], $imageStackB['subPrefix']);
        }
        if (! $subPrefix) {
            usort($imageStacks, 'subPrefixSort');
            $subPrefix = $imageStacks[0]['subPrefix'];
        }
        
        self::$cbData = $subPrefix;
        function subPrefixFilter($imageStack) {
            return $imageStack['subPrefix'] == BookReaderMeta::$cbData;
        }
        $imageStacks = array_filter($imageStacks, 'subPrefixFilter');
                
        function formatSort($imageStackA, $imageStackB) {
            $formatA = $imageStackA['imageFormat'];
            $formatB = $imageStackB['imageFormat'];
            if ($formatA == $formatB) {
                return 0;
            }
            
            $indexA = array_search($formatA, $imageFormatOrder);
            $indexB = array_search($formatB, $imageFormatOrder);
            // We already matched base on format, so both indices should be set
            if ($indexA == $indexB) {
                return 0;
            }
            return ($indexA < $indexB) ? 1 : -1;
        }
        usort($imageStacks, 'formatSort'); // necessary to remap keys
        
        if ( count($imageStacks) > 0 ) {
            return $imageStacks[0];
        } else {
            return array('imageFormat' => 'unknown', 'archiveFormat' => 'unknown', 'imageStackFile' => 'unknown');
        }
    }
    
    function isValidCallback($identifier) {
        $pattern = '/^[a-zA-Z_$][a-zA-Z0-9_$]*$/';
        return preg_match($pattern, $identifier) == 1;
    }
    
    function indexForLeaf($leafNum, $leafNums) {
        $key = array_search($leafNum, $leafNums);
        if ($key === FALSE) {
            return NULL;
        } else {
            return $key;
        }
    }
    
    function leafForIndex($index, $leafNums) {
        return $leafNums[$index]; // $$$ todo change to instance variables
    }
    
    function imageURL($leafNum, $metadata, $scale = null, $rotate = null) {
        // "Under the hood", non-public, dynamically changing (achtung!) image URLs currently look like:
        // http://{server}/BookReader/BookReaderImages.php?zip={zipPath}&file={filePath}&scale={scale}&rotate={rotate}
        // e.g. http://ia311213.us.archive.org/BookReader/BookReaderImages.php?zip=/0/items/coloritsapplicat00andriala/coloritsapplicat00andriala_jp2.zip&file=coloritsapplicat00andriala_jp2/coloritsapplicat00andriala_0009.jp2&scale=8&rotate=0
        
    
        $filePath = $this->imageFilePath($leafNum, $metadata['subPrefix'], $metadata['imageFormat']);
        $url = 'http://' . $metadata['server'] . '/BookReader/BookReaderImages.php?zip=' . $metadata['zip'] . '&file=' . $filePath;
        
        if ($scale !== null) {
            $url .= '&scale=' . $scale;
        }
        if ($rotate !== null) {
            $url .= '&rotate=' . $rotate;
        }
        
        return $url;
    }
    
    // $$$ move inside BookReaderPreview
    function previewURL($page, $metadata) {
        $query = array(
            'id' => $metadata['itemId'],
            'subPrefix' => $metadata['subPrefix'],
            'itemPath' => $metadata['itemPath'],
            'server' => $metadata['server'],
            'page' => $page,
        );
        
        return 'http://' . $metadata['server'] . '/BookReader/BookReaderPreview.php?' . http_build_query($query, '', '&');
    }
    
    function imageFilePath($leafNum, $subPrefix, $format) {
        $pathParts = pathinfo($subPrefix);
        $almostIdentifier = $pathParts['basename'];
        return sprintf("%s_%s/%s_%04d.%s", $almostIdentifier, $format, $almostIdentifier, intval($leafNum), $format);
    }
    
    // Parse date from _meta.xml to integer
    function parseYear($dateFromMetaXML) {
        // grab the first run of digits
        if (preg_match('|(\d+)|', $dateFromMetaXML, $matches)) {
            return (int)$matches[1];
        }
        return null;
    }
    
    function processRequest($requestEnv) {
        $id = $requestEnv['itemId']; // $$$ renamed
        $itemPath = $requestEnv['itemPath'];
        $subPrefix = $requestEnv['subPrefix']; // $$$ renamed
        $server = $requestEnv['server'];
        
        // Check if we're on a dev vhost and point to JSIA in the user's public_html on the datanode
        // $$$ TODO consolidate this logic
        $devHosts = array('testflip', 'rkumar', 'mang');
        foreach ($devHosts as $host) {
            if (strpos($_SERVER["REQUEST_URI"], '/~' . $host) === 0) { // Serving out of home dir
                $server .= ':80/' . $host;
            }
        }
        
        $this->emitResponse( $this->buildMetadata($id, $itemPath, $subPrefix, $server) );
    }
    
    function checkPrivs($filename) {
        if (!is_readable($filename)) {
            header('HTTP/1.1 403 Forbidden');
            exit(0);
        }
    }

}

?>