function get_next_page(){
    tmp_next_page = current_page_id +1;
    if (all_sub_pages_id[tmp_next_page])
    {
        current_page_id = tmp_next_page;
	    prev_page_id = current_page_id -1 ;
	    next_page_id = current_page_id+1;
        if (undefined != next_page_content["page_content"] )
        {
            show_page(next_page_content['page_content']);
            prev_page_content = current_page_content;
            current_page_content = next_page_content;
            tmp_next_page = current_page_id +1;
            next_page_content = "";
	    $("btn_next").disabled = true;
            getPage( all_sub_pages_id[tmp_next_page], process_ajax_response , "next" )
        }
    }
    else
    {
        //alert('page not loaded yet');
    }
}
function get_prev_page()
{
    tmp_prev_page = current_page_id - 1;
    
    if (all_sub_pages_id[tmp_prev_page])
    {
       current_page_id = tmp_prev_page;
       prev_page_id = current_page_id -1 ;
       next_page_id = current_page_id+1;
       if (undefined != prev_page_content["page_content"] )
       {
           if (prev_page_id < 0)
           {
               //$("btn_prev").value = "First";
               $("btn_prev").disabled = true;
			   if (all_sub_pages_id.length>1)
			   {
			       $("btn_next").disabled = false;
				   $("btn_next").value = "Next";

			   }
           } 
	       show_page( prev_page_content['page_content'] );
           next_page_content = current_page_content;
           current_page_content = prev_page_content;
           tmp_prev_page = current_page_id - 1;
           prev_page_content = "";
	   if ( undefined != all_sub_pages_id[tmp_prev_page] ) 
           {
               $("btn_prev").disabled = true;
	       getPage( all_sub_pages_id[tmp_prev_page], process_ajax_response , "prev" );
           }     
       }
    }
}

function load_first_page( req_flag )
{
	if (req_flag == "play" )
    {
	    current_page_id = 0;
	    prev_page_id    = 0;
	    next_page_id    = 0;
	    current_page_content =  first_page_content;
	    next_page_content    =  second_page_content;
    }
	
    show_page(current_page_content['page_content']);
    var page_title_cointainer = $("page_title_cointainer");
	if( null != page_title_cointainer  ){
		page_title_cointainer.innerHTML = current_page_content['page_title'];
	}
    
	
	next_page_id = 1;
	prev_page_id = null;
	enabled_disabled_prev_next_btn();
	
    
    
}
function play_page( btn_obj ){
   
	if ("Stop" == btn_obj.value )
    {
		clearInterval(play_handle);
		is_play_action = false;
		$("btn_play").value = "Play";
    }
	else{
	    is_play_action = true;
        load_first_page( "play" );
	    $("btn_play").value = "Stop";
        play_handle = setInterval( "get_next_page()", play_interval ); 
    }
}

function show_page( content ){
    obj_container = $("page_content_container");
    obj_container.innerHTML = format_output(content);
    
}


function getPage( page_id, callback , action_name ){
   var ajex=getAjexObject();
    if (ajex){
        url = "ajax-page-req.php?p="+page_id;
        ajex.onreadystatechange  = function() 
              {
                  if(ajex.readyState == 4) {
                      if(ajex.status == 200) {
                          ajexResponse = ajex.responseText;
                          if (ajexResponse!=""){        
                              callback(ajexResponse , action_name);
                          }
                      }
                  }    
              };
        ajex.open("GET",url, true ); //true for Asynchronious 
        ajex.send(null);

    }

}

function format_output(s){
    s =  s.replace(/\\r|\\n/g, '');
    return s;
}

function process_ajax_response( arg, action_name ){
    if( "next" == action_name  ){
        next_page_content = "";
        eval(arg);
        next_page_content = requested_page_content;
	
	enabled_disabled_prev_next_btn();

    }else if( "prev" == action_name  ){
        prev_page_content = "";
        eval(arg);
        prev_page_content = requested_page_content;
	enabled_disabled_prev_next_btn();
    }
}

function enabled_disabled_prev_next_btn(  )
{
    if (all_sub_pages_id[next_page_id]){
	$("btn_next").disabled = false;
	$("btn_next").value = "Next";
    }else{
	//$("btn_next").value = "Last";
	$("btn_next").disabled = true;
	if(is_play_action)
	{
	    clearInterval(play_handle);
	    is_play_action = false;
		$("btn_play").value = "Play";
	}
	
    }
    
    if (all_sub_pages_id[prev_page_id]){
	$("btn_prev").disabled = false;
	$("btn_prev").value = "Previous";
    }else{
	//$("btn_prev").value = "First";
	$("btn_prev").disabled = true;
    }
    //alert("current_page"+ current_page_id+"\nPrevid"+prev_page_id+"\nNext"+next_page_id);

}