var ajax_req = false;

function numericOnly(event) {
   var unicode = event.charCode ? event.charCode : event.keyCode;
   var chars = new Array(8,9,37,38,39,41,46,48,49,50,51,52,53,54,55,56,57,127);
   
   for(var i=0; i<chars.length; i++) {
      if(chars[i] == unicode) {
         return true;
      }
   }
   
   return false;
}

function ajax(url, id) {
   if(window.XMLHttpRequest) {
      ajax_req = new XMLHttpRequest();
      if (ajax_req.overrideMimeType) {
         ajax_req.overrideMimeType('text/plain');
      }
   } else if(window.ActiveXObject) {
      try {
         ajax_req = new ActiveXObject("Msxml2.XMLHTTP");
      } catch (e) {
         try {
            ajax_req = new ActiveXObject("Microsoft.XMLHTTP");
         } catch (e) { }
      }
   }
   if(!ajax_req) {
      alert("Your browser does not support AJAX.  Please see the help section for a list of supported browsers.");
      return false;
   }
   ajax_req.onreadystatechange = function() {
      if(ajax_req.readyState == 4) {
         if(ajax_req.status == 200) {
            document.getElementById(id).innerHTML = ajax_req.responseText;
         }
      }  
   }
   ajax_req.open("GET", url, true);
   ajax_req.send(null); 
}

function startUpload() {
   document.getElementById('picture_preview').style.height = "150px";
   document.getElementById('picture_preview').innerHTML = "<img src='images/loading.gif' />";
   document.getElementById('submit_button').disabled = true;
}

function finishUpload(file_id) {
   parent.document.getElementById('picture_id').value = file_id;
   parent.document.getElementById('picture_preview').innerHTML = "<img src='image.php?id=" + file_id + "' />";
   parent.document.getElementById('submit_button').disabled = false;
   if(file_id < 0) {
      document.getElementById('picture_preview').style.height = "50px";
   }
}
function checkExtension(file_name) {
   var extensions = ['.png', '.gif', '.jpg', '.jpeg'];
   var ext = file_name.substr(file_name.lastIndexOf('.')).toLowerCase();
   for(var i=0; i<extensions.length; i++) {
      if(ext == extensions[i]) {
         return true;
      }
   }
   return false;
}