var xmlHttp;
var currentInstructor;
var scrollDistance = 4;
var scrollDistance2 = 0;
var scrollSpeed = 10;
var objScrolling = {
    'up': 'up',
    'down': 'down',
    'undefined': 'undefined'
}
var scrolling = objScrolling.undefined;
var instructorTopOffset = 40;

function getInstructor(id)
{ 
    xmlHttp=GetXmlHttpObject();
    if (xmlHttp == null)
    {
      alert ("Your browser does not support AJAX!");
      return;
    } 
    var url = "GetInstructor.aspx";
    url = url + "?instructorID=" + id;
    url = url + "&sid=" + Math.random();
    xmlHttp.onreadystatechange = stateChanged;
    xmlHttp.open("GET", url, true);
    xmlHttp.send(null);
}

function stateChanged() 
{ 
    if (xmlHttp.readyState==4)
    { 
        document.getElementById("DivInstructor").innerHTML = xmlHttp.responseText;
        document.getElementById("DivShadow").innerHTML = xmlHttp.responseText;
    }
    else
    {
        document.getElementById("DivInstructor").innerHTML = "Loading instructor...<br /><br />";
        document.getElementById("DivShadow").innerHTML = "Loading instructor...<br /><br />";
    }
}

function GetXmlHttpObject()
{
    var xmlHttp=null;
    try
      {
          // Firefox, Opera 8.0+, Safari
          xmlHttp=new XMLHttpRequest();
      }
    catch (e)
      {
          // Internet Explorer
          try
            {
                xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");
            }
          catch (e)
            {
                xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
            }
      }
    return xmlHttp;
}

function showInstructor(instructorID, top, left) {
    var EmergencyDiv = document.getElementById('EmergencyMessage');
    var offsetEmergencyDiv = 0;
    var offsetEmergencyDiv2 = 0;
    if (EmergencyDiv) {
        offsetEmergencyDiv = EmergencyDiv.offsetHeight;
    }
    //alert(navigator.userAgent);
    //if(navigator.userAgent.indexOf('Firefox') > -1)offsetEmergencyDiv2 = 30;
    if (currentInstructor == null){ currentInstructor = instructorID; }
    getInstructor(instructorID);
    var instructorDiv = document.getElementById('DivInstructor');
    var shadowDiv = document.getElementById('DivShadow');
    //alert(offsetEmergencyDiv2);
    top = (top + offsetEmergencyDiv) - offsetEmergencyDiv2;
    instructorDiv.style.top = top + 'px';
    instructorDiv.style.left = left + 'px';
    shadowDiv.style.top = (top + 10) + 'px';
    shadowDiv.style.left = (left + 10) + 'px';
    if(instructorDiv.style.display == 'block' && currentInstructor != instructorID){
        instructorDiv.style.display = 'block';
        shadowDiv.style.display = 'block';
        currentInstructor = instructorID;
        //scrolling needs to be undefined
        adjustPageScroll(top);
        return;
    }
    if(instructorDiv.style.display == 'none'){
        instructorDiv.style.display = 'block';
        shadowDiv.style.display = 'block';
        //scrolling needs to be undefined
        adjustPageScroll(top);
    } else {
        instructorDiv.style.display = 'none';
        shadowDiv.style.display = 'none';
    }
    currentInstructor = instructorID;
}

function closeInstructor(){
    document.getElementById('DivInstructor').style.display = 'none';
    document.getElementById('DivShadow').style.display = 'none';
}

function adjustPageScroll(top) {
    var currentScrollPos = $(window).scrollTop();
    var myTop = (top - instructorTopOffset);
    if (currentScrollPos >= myTop && (scrolling == objScrolling.undefined || scrolling == objScrolling.down)) {
        scrolling = objScrolling.down;
        setTimeout(function() {
            if (currentScrollPos <= myTop) { //stop scrolling
                scrolling = objScrolling.undefined;
                return;
            }
            $(window).scrollTop(currentScrollPos - scrollDistance);
            adjustPageScroll(top);
        }, scrollSpeed);
    } else if (scrolling == objScrolling.undefined || scrolling == objScrolling.up) {
        scrolling = objScrolling.up;
        setTimeout(function() {
            if (currentScrollPos >= myTop) { //stop scrolling
                scrolling = objScrolling.undefined;
                return;
            }
            
            var testNumber = currentScrollPos - myTop;
            if (testNumber < -400) {
                scrollDistance2 = scrollDistance * 30;
            }
            else if (testNumber < -350) {
                scrollDistance2 = scrollDistance * 25;
            }
            else if (testNumber < -300) {
                scrollDistance2 = scrollDistance * 20;
            }
            else if (testNumber < -200) {
                scrollDistance2 = scrollDistance * 15;
            }
            else if (testNumber < -100) {
                scrollDistance2 = scrollDistance * 2;
            }
            if (testNumber >= -50) {
                scrollDistance2 = scrollDistance;
            }
            $(window).scrollTop(currentScrollPos + scrollDistance2);
            adjustPageScroll(top);
        }, scrollSpeed);
    } else {
        scrolling = objScrolling.undefined;
    }
}