|| applet xmlhttprequest-tutorial.curl
|| maintained by: sadman

|| Basic tutorial applet for sadXMLHtpRequest

|| Distributed under the New BSD License:
|#
  Copyright (c) 2006, Steve Adams
  All rights reserved.

  Redistribution and use in source and binary forms, with or without modification, are permitted 
  provided that the following conditions are met:

    * Redistributions of source code must retain the above copyright notice, this list of conditions 
      and the following disclaimer.
    * Redistributions in binary form must reproduce the above copyright notice, this list of conditions 
      and the following disclaimer in the documentation and/or other materials provided with the distribution.
    * Neither the name of curlr nor the names of its contributors may be used to endorse or promote products 
      derived from this software without specific prior written permission.

  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED 
  WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A 
  PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY 
  DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 
  PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 
  HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 
  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, 
  EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#|
{curl 5.0 applet}
{curl-file-attributes character-encoding = "utf8"}
{applet
    {compiler-directives careful? = true}
}

|| import the XML package
{import * from COM.CURLR.XML,
    location = "../lib/xml/load.scurl",
    location = "../lib/xml/load.pcurl"
}

|| A value block returns the evaluation of the code block it contains.
|| For top level code, the result is rendered into the browser
{value
    || Step 1. Create a sadXMLHttpRequest object
    let xmlhttp:sadXMLHttpRequest = {new sadXMLHttpRequest}

    || Step 2. Create an event handler that will issue a request 
    let request-button:CommandButton =
        {CommandButton
            label="get headers",
            {on Action do
                {xmlhttp.open HttpRequestMethod.head, {url "http://www.curlr.org/"}, async? = true}
            }
        }
    
    || Step 3. Create a procedure to be called when the state of the sadXMLHttpRequest object changes.
    || first make a Frame to put the returned headers
    let display-frame:Frame = {Frame}
    set xmlhttp.onreadystatechange =
        || We could also use a static procedure
        {proc {}:void
            || use a switch statement on the state
            {switch xmlhttp.readyState
             case readyStateEnum.Open do
                || we could make the send call immediately after the open call,
                || doing it here shows the handling of the state change
                {xmlhttp.send}
             case readyStateEnum.Loaded do
                {if-non-null hdrs = {xmlhttp.getAllResponseHeaders} then
                    || headers are returned as a string
                    || show them in the frame
                    {display-frame.add replace? = true,
                        {pre {value hdrs}}
                    }
                }
            }            
        }

    || display the command button and the Frame
    {VBox
        request-button,
        display-frame
    }
}