<?php
/**
 * Insert HTML
 *
 * $Id$
 *
 * @author gERD Schaufelberger <gerd@php-tools.net>
 * @license PHP License
 * @package WB
 * @subpackage base
 */

/**
 * Insert HTML
 * 
 * Basic interface to insert some HTML
 *
 * @version 0.1.1
 * @package WB
 * @subpackage html
 */
class WBHtml extends WBStdClass
{
    const AREA_HEAD = 1;
    const AREA_FOOT = 2;
    const AREA_JS_ONLOAD = 4;
        
   /**
    * actual HTML
    * @var array
    */
    private static $html = array();
    
    /**
     * list of callbacks to finalize html
     * 
     * @see get()
     * @see setFinalizer()
     * @var array
     */
    private static $finalize = array();

    /**
     * constructor
     * 
     * Avoid creating object
     */
    private function __construct()
    {        
    }
    
    /**
     * static constructor
     * 
     * Setupd internal HTML buffer
     */
    public static function staticConstruct()
    {
        self::$html[self::AREA_HEAD]    =   array();
        self::$html[self::AREA_FOOT]    =   array();
        self::$html[self::AREA_JS_ONLOAD]  =   array();
    }
    
    /**
     * add HTML
     * 
     * add string that will be included in HTML at the end
     * 
     * @param string $html
     * @param in $area 
     */
    public static function add($html, $area = self::AREA_HEAD)
    {
        self::checkArea($area);
        self::$html[$area][]    =   $html;
    }

    /**
     * fetch MTML
     * 
     * Receive HTML string of specified area
     * 
     * @param int $area
     * @return string 
     */
    public static function get($area = self::AREA_HEAD)
    {
        self::checkArea($area);
        foreach (self::$finalize as $callback) {
            call_user_func($callback);    
        }
        // prevent second call
        self::$finalize =   array();
        
        return implode("\n", self::$html[$area]);
    }

    /**
     * set callback for get
     * 
     * @param $callback
     */
    public static function addFinalizer($callback)
    {
        self::$finalize[]   =   $callback;
    }
    
    /**
     * Check whether area parameter is valid
     * 
     * @throws WBException_Parameter
     * @param $area
     */
    protected static function checkArea($area)
    {
        if (!isset(self::$html[$area])) {
            WBClass::load('WBException_Argument');
            throw new WBException_Argument('Invalid area: ' . $area, 1, __CLASS__);
        }
    }
    
}
?>