var nAttempts=1;
var nAttempts2=1;
var nAttempts3=1;
var nAttempts4=1;

/**
* Enters name and date and starts the problem
*/
function check_intro() {
	//check if filled
	if(document.step0.studentName.value=="" || document.step0.studentId.value=="") {
		alert("Please enter your name and university ID to start the problem.");
	} else {
		//a1.deactivate();
		a2.deactivate();
		a3.deactivate();
		a4.deactivate();
		a5.deactivate();
		var stuName=document.step0.studentName.value;
		var stuId=document.step0.studentId.value;
		stuName=stuName.replace(/<.*>/g,"");
		stuId=stuId.replace(/<.*>/g,"");		
		//document.getElementById("intro").style.display="none";

		//document.getElementById("identification").style.display="block";
		document.getElementById("description").style.display="block";
		//setInnerHTMLById("identification_date",'Loaded at '+full_time());
		//setInnerHTMLById("identification_name",'Name: '+stuName+", Student Number: "+stuId);	
		
		logLogIn();
	}
	return false;
}

/**
* Enters name and date and starts the problem on PHP-enabled
*/
function check_data() {
	//check if filled
	if(isPHPworking) {
		//a1.deactivate();
		a2.deactivate();
		a3.deactivate();
		a4.deactivate();
		a5.deactivate();
		var stuName=userName;
		var stuId=userID;
		stuName=stuName.replace(/<.*>/g,"");
		stuId=stuId.replace(/<.*>/g,"");		
		//document.getElementById("intro").style.display="none";

		//document.getElementById("identification").style.display="block";
		document.getElementById("description").style.display="block";
		//setInnerHTMLById("identification_date",'Loaded at '+full_time());
		//setInnerHTMLById("identification_name",'Name: '+stuName+", Student Number: "+stuId);
		a2.activate();
		logLogIn();
	}
}

/**
* Problem object
*/

	function check_mgso4() {
		
    var AttemptsLimit=3;

	// check for filled with a number
		if (document.step1.mgso4DH.value=="" || isNaN(document.step1.mgso4DH.value)) {
			alert("Please enter a number in the textbox before submitting.");		
		} else {
			var correct="-84.9";
			var isCorrect=relativeError(parseFloat(document.step1.mgso4DH.value),correct,0.003)&&number_sig(document.step1.mgso4DH.value)==3;
			var errorType="UNKNOWN_ERROR";
			
			var message="";
			if (isCorrect) {
				message="Your answer is CORRECT. The literature value for the heat of solution for ";
				message+="MgSO<sub><font size=-1>4<\/font><\/sub> is -84.9 kJ\/mol.  Let's try the next salt.";
				a2.deactivate();
				a3.activate();
				errorType="CORRECT";
				document.getElementById("saltsq2").style.display="block";
				
			} else if (nAttempts>=AttemptsLimit) {
				message="Your answer is WRONG. ";
				message+="The heat of solution for MgSO<sub><font size=-1>4<\/font><\/sub> is: "+format_sig(correct,3)+" kJ\/mol.";
				message+="<br> Try to verify this result in the virtual lab before continuing.<p>";
				a2.deactivate();
				a3.activate();
				document.getElementById("saltsq2").style.display="block";
				
			} else {
				message+="Your result is wrong, but you have still "+(AttemptsLimit-nAttempts)+" attempts left. Check your answer and submit again.";
				message+="<br><i>You may want to review the handout;  the molecular weight for ";
				message+="MgSO<sub><font size=-1>4<\/font><\/sub> is 120.37.<\/i>";
			}
			a2.setFeedback(message,(isCorrect)?1:nAttempts);
						
			logFormCheck("step1",nAttempts,document.step1.mgso4DH.value,format_sig(correct,3),message,isCorrect,errorType);
			nAttempts++;
		}
		return false;
	}	



	function check_k2so4() {
		
    var AttemptsLimit=3;

	// check for filled with a number
		if (document.step2.k2so4DH.value=="" || isNaN(document.step2.k2so4DH.value)) {
			alert("Please enter a number in the textbox before submitting.");		
		} else {
			var correct="26.7";
			var isCorrect=relativeError(parseFloat(document.step2.k2so4DH.value),correct,0.007)&&number_sig(document.step2.k2so4DH.value)==3;
			var errorType="UNKNOWN_ERROR";
			
			var message="";
			if (isCorrect) {
				message="Your answer is CORRECT. The literature value for the heat for solution for ";
				message+="K<sub><font size=-1>2<\/font><\/sub>SO<sub><font size=-1>4<\/font><\/sub> is 26.7 kJ\/mol. Let's try the next salt.";
				a3.deactivate();
				a4.activate();
				errorType="CORRECT";
				document.getElementById("saltsq3").style.display="block";
				
			} else if (nAttempts2>=AttemptsLimit) {
				message="Your answer is WRONG. ";
				message+="The heat of solution for K<sub><font size=-1>2<\/font><\/sub>SO<sub><font size=-1>4<\/font><\/sub>";
				message+=" is: "+format_sig(correct,3)+" kJ\/mol. <br> Try to verify this result in the virtual lab before continuing.<p>";
				a3.deactivate();
				a4.activate();
				document.getElementById("saltsq3").style.display="block";
				
			} else {
				message+="Your result is wrong, but you have still "+(AttemptsLimit-nAttempts2)+" attempts left. Check your answer and submit again.";
				message+="<br><i>Hint: You may want to review the handout;  the "
				message+="molecular weight for K<sub><font size=-1>2<\/font><\/sub>SO<sub><font size=-1>4<\/font><\/sub> is 174.254.<\/i>";
			}
			a3.setFeedback(message,(isCorrect)?1:nAttempts2);
						
			logFormCheck("step2",nAttempts2,document.step2.k2so4DH.value,format_sig(correct,3),message,isCorrect,errorType);
			nAttempts2++;
		}
		return false;
	}	



	function check_kno3() {
		
    var AttemptsLimit=3;

	// check for filled with a number
		if (document.step3.kno3DH.value=="" || isNaN(document.step3.kno3DH.value)) {
			alert("Please enter a number in the textbox before submitting.");		
		} else {
			var correct="35.6";
			var isCorrect=relativeError(parseFloat(document.step3.kno3DH.value),correct,0.003)&&number_sig(document.step3.kno3DH.value)==3;
			var errorType="UNKNOWN_ERROR";
			
			var message="";
			if (isCorrect) {
				message="Your answer is CORRECT. The literature value for the heat for solution for ";
				message+="KNO<sub><font size=-1>3<\/font><\/sub> is 35.6 kJ\/mol. Let's try the next salt.";
				a4.deactivate();
				a5.activate();
				errorType="CORRECT";
				document.getElementById("saltsq4").style.display="block";
				
			} else if (nAttempts3>=AttemptsLimit) {
				message="Your answer is WRONG. ";
				message+="The heat of solution for KNO<sub><font size=-1>3<\/font><\/sub> ";
				message+="is: "+format_sig(correct,3)+" kJ\/mol. <br> Try to verify this result in the virtual lab before continuing.<p>";
				a4.deactivate();
				a5.activate();
				document.getElementById("saltsq4").style.display="block";
				
			} else {
				message+="Your result is wrong, but you have still "+(AttemptsLimit-nAttempts3)+" attempts left. Check your answer and submit again.";
				message+="<br><i>Hint: You may want to review the handout;  the "
				message+="molecular weight for KNO<sub><font size=-1>3<\/font><\/sub> is 101.103 .<\/i>";
			}
			a4.setFeedback(message,(isCorrect)?1:nAttempts3);
						
			logFormCheck("step3",nAttempts3,document.step3.kno3DH.value,format_sig(correct,3),message,isCorrect,errorType);
			nAttempts3++;
		}
		return false;
	}	

	function check_nh4no3() {
		
    var AttemptsLimit=3;

	// check for filled with a number
		if (document.step4.nh4no3DH.value=="" || isNaN(document.step4.nh4no3DH.value)) {
			alert("Please enter a number in the textbox before submitting.");		
		} else {
			var correct="26.4";
			var isCorrect=relativeError(parseFloat(document.step4.nh4no3DH.value),correct,0.006)&&number_sig(document.step4.nh4no3DH.value)==3;
			var errorType="UNKNOWN_ERROR";
			
			var message="";
			if (isCorrect) {
				message="Your answer is CORRECT. The literature value for the heat for solution for ";
				message+="NH<sub><font size=-1>4</font></sub>NO<sub><font size=-1>3</font></sub> is 26.4 kJ\/mol.";
				a5.deactivate();
				errorType="CORRECT";
				document.getElementById("done").style.display="block";
				document.getElementById("vlab").style.display="none";
				
			} else if (nAttempts4>=AttemptsLimit) {
				message="Your answer is WRONG. ";
				message+="The heat of solution for NH<sub><font size=-1>4</font></sub>NO<sub><font size=-1>3</font></sub> ";
				message+="is: "+format_sig(correct,3)+" kJ\/mol. <br> Try to verify this result in the virtual lab before continuing.<p>";
				a5.deactivate();
			document.getElementById("done").style.display="block";
			document.getElementById("vlab").style.display="none";
				
			} else {
				message+="Your result is wrong, but you have still "+(AttemptsLimit-nAttempts4)+" attempts left. Check your answer and submit again.";
				message+="<br><i>Hint: You may want to review equation 7 in the handout;  the "
				message+="molecular weight for NH<sub><font size=-1>4</font></sub>NO<sub><font size=-1>3</font></sub> is 80.043.<\/i>";
			}
			a5.setFeedback(message,(isCorrect)?1:nAttempts4);
						
			logFormCheck("step4",nAttempts4,document.step4.nh4no3DH.value,format_sig(correct,3),message,isCorrect,errorType);
			nAttempts4++;
		}
		return false;
	}