using System;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Web;
using System.Web.SessionState;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;
using System.Data.SqlClient;
using System.Text;

namespace Stuff
{
    /// <summary>
    /// Summary description for MessageBox.
    /// </summary>
    public class MessageBox
    {
        private static Hashtable m_executingPages = new Hashtable();

        private MessageBox(){}

        public static void Show( string sMessage )
        {
            // If this is the first time a page has called this method then
            if( !m_executingPages.Contains( HttpContext.Current.Handler ) )
            {
                // Attempt to cast HttpHandler as a Page.
                Page executingPage = HttpContext.Current.Handler as Page;

                if( executingPage != null )
                {
                    // Create a Queue to hold one or more messages.
                    Queue messageQueue = new Queue();

                    // Add our message to the Queue
                    messageQueue.Enqueue( sMessage );

                    // Add our message queue to the hash table. Use our page reference
                    // (IHttpHandler) as the key.
                    m_executingPages.Add( HttpContext.Current.Handler, messageQueue );

                    // Wire up Unload event so that we can inject 
                    // some JavaScript for the alerts.
                    executingPage.Unload += new EventHandler( ExecutingPage_Unload );
                }   
            }
            else
            {
                // If were here then the method has allready been 
                // called from the executing Page.
                // We have allready created a message queue and stored a
                // reference to it in our hastable. 
                Queue queue = (Queue) m_executingPages[ HttpContext.Current.Handler ];

                // Add our message to the Queue
                queue.Enqueue( sMessage );
            }
        }


        // Our page has finished rendering so lets output the
        // JavaScript to produce the alert's
        private static void ExecutingPage_Unload(object sender, EventArgs e)
        {
            // Get our message queue from the hashtable
            Queue queue = (Queue) m_executingPages[ HttpContext.Current.Handler ];

            if( queue != null )
            {
                StringBuilder sb = new StringBuilder();

                // How many messages have been registered?
                int iMsgCount = queue.Count;

                // Use StringBuilder to build up our client slide JavaScript.
                sb.Append( "<script language='javascript'>" );

                // Loop round registered messages
                string sMsg;
                while( iMsgCount-- > 0 )
                {
                    sMsg = (string) queue.Dequeue();
                    sMsg = sMsg.Replace( "\n", "\\n" );
                    sMsg = sMsg.Replace( "\"", "'" );
                    sb.Append( @"alert( """ + sMsg + @""" );" );
                }

                // Close our JS
                sb.Append( @"</script>" );

                // Were done, so remove our page reference from the hashtable
                m_executingPages.Remove( HttpContext.Current.Handler );

                // Write the JavaScript to the end of the response stream.
                HttpContext.Current.Response.Write( sb.ToString() );
            }
        }
    }
}