//==========================================
// create the request
//==========================================
function createRequest()
{
    var request = null; 
    try
    {
        request = new XMLHttpRequest();
    }
    catch(trymicrosoft)
    {
	try
	{
	    request = new ActiveXObject("Msxml2.XMLHTTP");
	}
	catch(othermicrosoft)
	{
	    try
	    {
	        request = new ActiveXObject("Microsoft.XMLHTTP");
	    }
	    catch(failed)
	    {
	        request = null;
	    }
	}
    }

    if (request == null)
    {
        alert ("Error creating request object!");
    }
    else
    {
	return request;
    }
}

var request = createRequest();


//==========================================
// get new teachers list
//==========================================
function updateTeacher(schoolId, classId, periodTeacher, periodClass, schoolTerm)
{
    var v_classId = classId.value
//alert ("schoolId: " + schoolId);
//alert ("v_classId: " + v_classId);
//alert ("periodTeacher: " + periodTeacher);
    var url = "includes/updateTeacherList.php?schoolId=" + schoolId + "&classId=" + v_classId + "&periodTeacher=" + periodTeacher + "&periodClass=" + periodClass + "&schoolTerm=" + schoolTerm;
    url = url + "&dummy=" + new Date().getTime();
    request.open("GET", url, true);
    request.onreadystatechange = updateTeachersList;
    request.send(null);
}


//==========================================
// update teachers list
//==========================================
function updateTeachersList() {
	//alert (request.readyState);
  if (request.readyState == 4) 
  {
	//alert (request.status);
    if (request.status == 200)
    {
	var A_teacher = new Array();
	var teacherName = "";
	var teacherId = "";
	//========================================
	// new list of teachers names and ids
	//========================================
	var newList = request.responseText;
	//alert ("newList: " + newList);
	
	//========================================
	// get which period to update
	//========================================
    	var A_tempList = newList.split("#");
	var period = A_tempList[0];
	//alert ("period: " + period);

	//========================================
	// get names and ids
	//========================================
    	var A_newList = A_tempList[1].split(";");
        //alert ("size of A_newList: " + A_newList.length);
   	switch (period) {
      	    case "foo":
	    	var lgth = document.studForm.foo.options.length;
	    	document.studForm.foo.options.length = 0;
	    	lgth = document.studForm.foo.options.length;
		for (var i = 0; i <  A_newList.length; i++) {
	    	    A_teacher = A_newList[i].split(":");
	    	    teacherName = A_teacher[0];
	    	    teacherId = A_teacher[1];
	    	    document.studForm.foo.options[i] = new Option(teacherName, teacherId);
		}
	    	lgth = document.studForm.foo.options.length;
         	document.studForm.foo.length = lgth;
            break;
      
      	    case "period1Teacher":
	    	var lgth = document.studForm.period1Teacher.options.length;
	    	document.studForm.period1Teacher.options.length = 0;
	    	lgth = document.studForm.period1Teacher.options.length;
		for (var i = 0; i <  A_newList.length; i++) {
	    	    A_teacher = A_newList[i].split(":");
	    	    teacherName = A_teacher[0];
	    	    teacherId = A_teacher[1];
	    	    document.studForm.period1Teacher.options[i] = new Option(teacherName, teacherId);
		}
	    	lgth = document.studForm.period1Teacher.options.length;
         	document.studForm.period1Teacher.length = lgth;
            break;
      
      	    case "period2Teacher":
	    	var lgth = document.studForm.period2Teacher.options.length;
	    	document.studForm.period2Teacher.options.length = 0;
	    	lgth = document.studForm.period2Teacher.options.length;
		for (var i = 0; i <  A_newList.length; i++) {
	    	    A_teacher = A_newList[i].split(":");
	    	    teacherName = A_teacher[0];
	    	    teacherId = A_teacher[1];
	    	    document.studForm.period2Teacher.options[i] = new Option(teacherName, teacherId);
		}
	    	lgth = document.studForm.period2Teacher.options.length;
         	document.studForm.period2Teacher.length = lgth;
            break;
      
      	    case "periodHTeacher":
	    	var lgth = document.studForm.periodHTeacher.options.length;
	    	document.studForm.periodHTeacher.options.length = 0;
	    	lgth = document.studForm.periodHTeacher.options.length;
		for (var i = 0; i <  A_newList.length; i++) {
	    	    A_teacher = A_newList[i].split(":");
	    	    teacherName = A_teacher[0];
	    	    teacherId = A_teacher[1];
	    	    document.studForm.periodHTeacher.options[i] = new Option(teacherName, teacherId);
		}
	    	lgth = document.studForm.periodHTeacher.options.length;
         	document.studForm.periodHTeacher.length = lgth;
            break;
      
      	    case "period3Teacher":
	    	var lgth = document.studForm.period3Teacher.options.length;
	    	document.studForm.period3Teacher.options.length = 0;
	    	lgth = document.studForm.period3Teacher.options.length;
		for (var i = 0; i <  A_newList.length; i++) {
	    	    A_teacher = A_newList[i].split(":");
	    	    teacherName = A_teacher[0];
	    	    teacherId = A_teacher[1];
	    	    document.studForm.period3Teacher.options[i] = new Option(teacherName, teacherId);
		}
	    	lgth = document.studForm.period3Teacher.options.length;
         	document.studForm.period3Teacher.length = lgth;
            break;
      
      	    case "period4Teacher":
	    	var lgth = document.studForm.period4Teacher.options.length;
	    	document.studForm.period4Teacher.options.length = 0;
	    	lgth = document.studForm.period4Teacher.options.length;
		for (var i = 0; i <  A_newList.length; i++) {
	    	    A_teacher = A_newList[i].split(":");
	    	    teacherName = A_teacher[0];
	    	    teacherId = A_teacher[1];
	    	    document.studForm.period4Teacher.options[i] = new Option(teacherName, teacherId);
		}
	    	lgth = document.studForm.period4Teacher.options.length;
         	document.studForm.period4Teacher.length = lgth;
            break;
      
      	    case "period5Teacher":
	    	var lgth = document.studForm.period5Teacher.options.length;
	    	document.studForm.period5Teacher.options.length = 0;
	    	lgth = document.studForm.period5Teacher.options.length;
		for (var i = 0; i <  A_newList.length; i++) {
	    	    A_teacher = A_newList[i].split(":");
	    	    teacherName = A_teacher[0];
	    	    teacherId = A_teacher[1];
	    	    document.studForm.period5Teacher.options[i] = new Option(teacherName, teacherId);
		}
	    	lgth = document.studForm.period5Teacher.options.length;
         	document.studForm.period5Teacher.length = lgth;
            break;
      
      	    case "period6Teacher":
	    	var lgth = document.studForm.period6Teacher.options.length;
	    	document.studForm.period6Teacher.options.length = 0;
	    	lgth = document.studForm.period6Teacher.options.length;
		for (var i = 0; i <  A_newList.length; i++) {
	    	    A_teacher = A_newList[i].split(":");
	    	    teacherName = A_teacher[0];
	    	    teacherId = A_teacher[1];
	    	    document.studForm.period6Teacher.options[i] = new Option(teacherName, teacherId);
		}
	    	lgth = document.studForm.period6Teacher.options.length;
         	document.studForm.period6Teacher.length = lgth;
            break;
      
   	}
    }
  }
}