<?php

/**
 * Validates a rel/rev link attribute against a directive of allowed values
 * @note We cannot use Enum because link types allow multiple
 *       values.
 * @note Assumes link types are ASCII text
 */
class HTMLPurifier_AttrDef_HTML_LinkTypes extends HTMLPurifier_AttrDef
{
    
    /** Name config attribute to pull. */
    protected $name;
    
    public function __construct($name) {
        $configLookup = array(
            'rel' => 'AllowedRel',
            'rev' => 'AllowedRev'
        );
        if (!isset($configLookup[$name])) {
            trigger_error('Unrecognized attribute name for link '.
                'relationship.', E_USER_ERROR);
            return;
        }
        $this->name = $configLookup[$name];
    }
    
    public function validate($string, $config, $context) {
        
        $allowed = $config->get('Attr', $this->name);
        if (empty($allowed)) return false;
        
        $string = $this->parseCDATA($string);
        $parts = explode(' ', $string);
        
        // lookup to prevent duplicates
        $ret_lookup = array();
        foreach ($parts as $part) {
            $part = strtolower(trim($part));
            if (!isset($allowed[$part])) continue;
            $ret_lookup[$part] = true;
        }
        
        if (empty($ret_lookup)) return false;
        
        $ret_array = array();
        foreach ($ret_lookup as $part => $bool) $ret_array[] = $part;
        $string = implode(' ', $ret_array);
        
        return $string;
        
    }
    
}

