using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

using System.Text;      // Encoding
using System.Threading;

namespace BasicAjaxCSharp
{
    public partial class PushServer : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            string[] pictures = new string[3];
            string[] pictureInfo = new string[3];
            int pic = 0;

            // Create an array of images and information
            pictures[0] = "boat.gif";
            pictures[1] = "car.gif";
            pictures[2] = "train.gif";
            pictureInfo[0] = "A boat";
            pictureInfo[1] = "A car";
            pictureInfo[2] = "A train";
            pic = 0;

            // Set the content type
            Response.ContentType = "text/plain";
            Response.ContentEncoding = Encoding.UTF8;

            // Prevent page from being cached when we are polling
            //Response.Expires = -1;

            // Create the HTML for this push page
            // We need to call the heartbeat function of the
            // parent page using this server page.
            Response.Write("<html xmlns='http://www.w3.org/1999/xhtml' >");
            Response.Write("<head>");
            Response.Write("</head>");

            Response.Write("<body>");

            // Loop forever pushing content to the HTML page
            while (true)
            {
                // Every time around the loop push more content to the
                // parent page by calling it's function
                Response.Write("<script type='text/javascript' language='javascript'>");

                // For generic browsers
                //Response.Write("parent.heartbeat();");
                //Response.Write("parent.newpicture('" + pictures[pic] + "', '" + pictureInfo[pic] + "');");

                // For IE
                Response.Write("parent._parent.heartbeat();");   // IE Change here
                Response.Write("parent._parent.newpicture('" + pictures[pic] + "', '" + pictureInfo[pic] + "');");   // IE Change here

                Response.Write("</script>");
                Response.Flush();

                // This example is just for simulation, so we just wait 5 seconds
                // before sending more data. Normally, this page would be
                // monitoring something or fetching new data for display.
                // In theory this works, in practice the web server times out to protect
                // web pages looping forever and killing the servers performance.
                // So in effect I'm cheating and allowing the timeout to happen, which
                // will also cause a reload but the principle idea is illustrated here.
                Thread.Sleep(5000);

                // Just for simulation, here we just pick a new picture
                if (pic + 1 < 3)
                {
                    pic = pic + 1;
                }
                else
                {
                    pic = 0;
                }
            }

            // THIS PAGE ACTUALLY NEVER ENDS BUT LOOPS FOREVER
            // HOWEVER, THE WEBSERVER WILL EVENTUALLY TIMEOUT THE
            // PAGE BECAUSE IT TRYS TO PREVENT BROKEN CODE FROM
            // KILLING THE WEBSERVER
            // CALLING PAGE MUST CHECK FOR THIS AND RELOAD THIS PAGE

            // Never gets here
            //Response.Write("</body>");
            //Response.Write("</html>");
        }
    }
}