/**
 *	Created with MAX's HTML Beauty++ 2004
 *	arsenic5_check.js
 *	@author Amani Ahmed, Jordi Cuadros
 *	@date July 27 2004
*/

var nAttempts = 1;
var curActivity=1;
var thisAttemptNumber=0
/**
 * Check function for Activity 1.0
 */
function act1Check(){
	thisAttemptNumber=nAttempts;
	var isAttemptWrong=true;
	
	var user_dens=new Array(4);
	user_dens[0]=document.activity1.density1.value;
	user_dens[1]=document.activity1.density2.value;
	user_dens[2]=document.activity1.density3.value;
	user_dens[3]=document.activity1.density4.value;
	var user_answer="";

	// check for correct answer
	var correct=new Array(4);
	correct[0] = calcDensity(50);
	correct[1] = calcDensity(5);
	correct[2] = calcDensity(.50);
	correct[3] = calcDensity(.050);
	var correctString="";
	
	for (var i=0;i<4;i++) {
		if(user_dens[i] == ""){
			alert('Please enter an answer before checking.');
			return false;
		}
		correctString += format_sig(correct[i],4)+ ", ";
		user_answer += user_dens[i]+", ";
	}
	correctString=correctString.substring(0,correctString.length-2);
	user_answer=user_answer.substring(0,user_answer.length-2);
	
	var nCorrect=0;
	var nNonSig=0;
	var nApprox=0;
	
	for (var i=0;i<4;i++) {
		if (user_dens[i]==format_sig(correct[i],4)) {
			nCorrect++;
		} else if (format_sig(user_dens[i],4)==format_sig(correct[i],4)){
			nNonSig++;
		} else if (absError(user_dens[i],correct[i],0.001)){
			nApprox++;
		}
	}
	
	// check for expected errors
	var isExpectedError=new Array();
		isExpectedError[0]=false;
	
	// expected error: concentrations ten times larger
	var nErrors=0;
	
	for (var i=0;i<4;i++) {
		if (absError(user_dens[i],calcDensity(500/Math.pow(10,i)),0.002)) {
			nErrors++;
		}
	}
	if (nErrors==4) isExpectedError[0]=true;
	
	var message="";
	
	if (nCorrect==4) {
		message="Excellent, you got all the densities right! Now move to the next question!";
		a1.deactivate();
		a2.activate();
		isAttemptWrong=false;	
		nAttempts=0;
	} else if (nCorrect+nNonSig==4) {
		message="Good job, but your results are not expressed with the correct number of significant figures. ";
		message+= "The expected results are "+ correctString +" g/mL. ";
		message+= "Move to the next question but be more careful next time!";
		a1.deactivate();
		a2.activate();	
		isAttemptWrong=false;	
		nAttempts=0;
	} else if (nCorrect+nNonSig+nApprox==4) {
		message="Pretty good, but your results are not precise enough. ";
		message+= "The correct results are "+ correctString +" g/mL. ";
		message+= "Move to the next question but be more careful next time!";
		a1.deactivate();
		a2.activate();	
		isAttemptWrong=false;	
		nAttempts=0;
	} else if (nAttempts<3) {	
		if (isExpectedError[0]) {
			message="It looks as if your solutions don't have the correct concentrations. ";
			message+="How many grams of solute are in 100 mL of a solution that has a concentration of 50 g/L? ";
			message+="Are you sure that you're using the right amounts?";
		} else if (nCorrect+nApprox>=2) {
			message="Nice! You're doing a good job! ";
			message+= "But " +(4-nCorrect-nApprox-nNonSig)+" of your results have errors larger than expected. ";
			message+= "Go back and check them.";
		} else {
			message="Please try again.";
		}
	} else if (nAttempts==3) {
		message="This was your third attempt and ";
		message+="your results are not precise enough to get to the next question. Please CLICK REFRESH/RELOAD to start over. ";
		a1.deactivate();
	}

	setFeedback(0, message,thisAttemptNumber);		
	if(window.logUserAction) logUserAction("Arsenic5_activity1_check()", "txt", checkString(0,isAttemptWrong,thisAttemptNumber,user_answer+" g/mL",message));	
	nAttempts++;
	
	return false;
}

/**
 * Check function for Activity 2.0
 */
function act2Check(){
	var message="";
	user_answer=document.activity2.density2.value;
	var isAttemptWrong=true;
	
	if(user_answer == ""){
		alert('Please enter an answer before checking');
	} else {	
		var gNaAsO2=parseFloat(unk*129.28);
		var volumeNaAsO2mL=gNaAsO2/129.28*22.99/2.66+gNaAsO2/129.28*106.29/8.3;
		var volumeWatermL=water*18.016;
		var correct=gNaAsO2/(volumeWatermL+volumeNaAsO2mL)*1000;
		var badc_answers=new Array ();
			badc_answers[1]= calcDensity(correct);
			badc_answers[2]= calcDensity(correct)/calcDensity(50)*50;
			badc_answers[3]= calcDensity(correct)/calcDensity(5)*5;
			badc_answers[4]= calcDensity(correct)/calcDensity(0.5)*0.5;
			badc_answers[5]= calcDensity(correct)/calcDensity(0.05)*0.05;
			badc_answers[6]= (calcDensity(50)-1)*50/(calcDensity(correct)-1);
			badc_answers[7]= (calcDensity(5)-1)*5/(calcDensity(correct)-1);
		
		if(relativeError(user_answer,correct,0.05) && number_sig(user_answer)==4){
			message+="Excellent! You did a good job!";
			isAttemptWrong=false;
			a2.deactivate();
		} else if(nAttempts < 3){					
			if(relativeError(user_answer, correct, 0.05))
				message+="You're pretty close, but your result is not expressed with the correct number of significant figures.";
			else if(relativeError(user_answer, badc_answers[1],0.02))
				message+="Remember that density and concentration are different concepts; check the video for this unit";
			else if(relativeError(user_answer, badc_answers[2],0.02) || relativeError(user_answer, badc_answers[3],0.02)
					|| relativeError(user_answer, badc_answers[4],0.02) || relativeError(user_answer, badc_answers[5],0.02))
				message+="Remember that the change in density is related to the change in concentration";
			else if(relativeError(user_answer, badc_answers[6],0.02)|| relativeError(user_answer, badc_answers[7],0.02))
				message+="It seems that you're stating that the higher the density of the solution is, the lower the concentration. Are you sure that's right?";
			else if(user_answer>1000 || user_answer<0)
				message+="You're giving an unlikely value for an answer. You should check whether your result makes sense before submitting it.";
			else
				message+="Please check your answer and try again.";
		} else if (nAttempts==3) {
			message+="This was your third attempt and your answer wasn't correct. ";
			message+="The correct concentration of arsenite is "+format_sig(correct,4)+" g/L. Please CLICK REFRESH/RELOAD to start over with a new problem.";
			a2.deactivate();
		} else if (nAttempts > 3) {
			message="You have taken three attempts for this question. Please CLICK REFRESH/RELOAD to start over with a new problem.";
			a2.deactivate();
		}
		setFeedback(1, message,nAttempts);
		if(window.logUserAction) logUserAction("Arsenic5_activity2_check()", "txt", checkString(1,isAttemptWrong,nAttempts,user_answer+" g/L",message));	
		nAttempts++;
	}
	return false;	
}

/**	
 * Constructs a string that reports the statistics of the user's latest attempt of the 
 * problem including the attempt number, user-given answers and feedback
 *
 * @return toTrace		a string containing information about the user's last attempt
*/
function checkString(fIndex,isWrong,nAtt,usAns,message) {
    var toTrace=isWrong?"Wrong":"Correct";
    	toTrace += " checking of form "+fIndex;
		toTrace += "(attempt "+nAtt+ "). ";	
		toTrace += "The delivered answer is "+usAns+". ";
		toTrace += "The system answers: "+message;
	return toTrace;
}

/**
* Calculate density(g/mL) from concentration (in g/L)
*/
function calcDensity(conc) {
	var gNaAsO2=parseFloat(conc);
	var volumeNaAsO2mL=gNaAsO2/129.28*22.99/2.66+gNaAsO2/129.28*106.29/8.3;
	var volumeWatermL=1000-volumeNaAsO2mL;
	var gWater=volumeWatermL;
	return (gWater+gNaAsO2)/(volumeNaAsO2mL+volumeWatermL);
}