function checkinput () {
	err = 0;
	if (document.forms.roi.tanksize.value.length == 0) err++;
	if (document.forms.roi.currentavg.value.length == 0) err++;
	if (document.forms.roi.galperyear.value.length == 0) err++;
	if (document.forms.roi.costperdel.value.length == 0) err++;
	if (err > 0) {
		window.alert ("Please fill in all required fields.");
		return false;
	} else {
		return true;
	}
}

function updateROI () {

	if (! checkinput () ) {
		return false;
	}

	tanksize = parseInt(document.forms.roi.tanksize.value);
	currentavg = parseInt(document.forms.roi.currentavg.value);
	galperyear = parseInt(document.forms.roi.galperyear.value);
	costperdel = parseInt(document.forms.roi.costperdel.value);
	numyears = document.forms.roi.time.options[document.forms.roi.time.selectedIndex].value;

	//optgal = Math.round(tanksize * .8);

       
	if(document.forms.roi.optgal.value == '--' || document.forms.roi.optgal.value == ''){
		optgal = Math.round(tanksize * .8);
	}else{
		optgal = parseInt(document.forms.roi.optgal.value);
	}
	document.forms.roi.optgal.value = optgal;

	equipcost = parseInt(document.forms.roi.equipcost.value);
	datacenter = parseInt(document.forms.roi.datacenter.value);
	installcost = parseInt(document.forms.roi.installcost.value);

	annsavings = roundThis (((galperyear / currentavg) - (galperyear / optgal)) * costperdel, 0);

	// document.getElementById("maxsave").innerHTML = "$" + annsavings;

	currentavg_plusten = roundThis (currentavg + (currentavg * .1), 0);
	currentavg_minusten = roundThis (currentavg - (currentavg * .1), 0);
	galperyear_plusten = roundThis (galperyear + (galperyear * .1), 0);
	galperyear_minusten = roundThis (galperyear - (galperyear * .1), 0);

	document.getElementById("col0").innerHTML = currentavg_minusten;
	document.getElementById("col1").innerHTML = currentavg;
	document.getElementById("col2").innerHTML = currentavg_plusten;

	document.getElementById("row0").innerHTML = galperyear_plusten;
	document.getElementById("row1").innerHTML = galperyear;
	document.getElementById("row2").innerHTML = galperyear_minusten;

	document.getElementById("grid00").innerHTML = adddollar (roundThis (((galperyear_plusten / currentavg_minusten) - (galperyear_plusten / optgal)) * costperdel, 0));
	document.getElementById("grid01").innerHTML = adddollar (roundThis (((galperyear_plusten / currentavg) - (galperyear_plusten / optgal)) * costperdel, 0));
	document.getElementById("grid02").innerHTML = adddollar (roundThis (((galperyear_plusten / currentavg_plusten) - (galperyear_plusten / optgal)) * costperdel, 0));
	document.getElementById("grid10").innerHTML = adddollar (roundThis (((galperyear / currentavg_minusten) - (galperyear / optgal)) * costperdel, 0));
	document.getElementById("grid11").innerHTML = adddollar (roundThis (((galperyear / currentavg) - (galperyear / optgal)) * costperdel, 0));
	document.getElementById("grid12").innerHTML = adddollar (roundThis (((galperyear / currentavg_plusten) - (galperyear / optgal)) * costperdel, 0));
	document.getElementById("grid20").innerHTML = adddollar (roundThis (((galperyear_minusten / currentavg_minusten) - (galperyear_minusten / optgal)) * costperdel, 0));
	document.getElementById("grid21").innerHTML = adddollar (roundThis (((galperyear_minusten / currentavg) - (galperyear_minusten / optgal)) * costperdel, 0));
	document.getElementById("grid22").innerHTML = adddollar (roundThis (((galperyear_minusten / currentavg_plusten) - (galperyear_minusten / optgal)) * costperdel, 0));
	document.getElementById("annual_title").innerHTML = "Optimum Gallons Delivered/Stop = "+optgal+ " <br> vs <br> Current Average Gallons Delivered +- 10%";

	total_save = 0;
	total_cost = 0;
	total_net = 0;
	for (x=1; x <= numyears; x++) {
		id_save = "yr" + x + "save";
		id_cost = "yr" + x + "cost";
		id_net = "yr" + x + "net";
		id_label = "yr" + x + "label";

		document.getElementById(id_label).innerHTML = x;

		yrSave = annsavings;
		document.getElementById(id_save).innerHTML = adddollar (yrSave);
		total_save = total_save + yrSave;

		if (x == 1) yrCost = datacenter + equipcost + installcost; else yrCost = datacenter;
		document.getElementById(id_cost).innerHTML = adddollar (yrCost);
		total_cost = total_cost + yrCost;

		yrNet = yrSave - yrCost;
		document.getElementById(id_net).innerHTML = adddollar (yrNet);
		total_net = total_net + yrNet;
	}
	document.getElementById("totalsave").innerHTML = adddollar (total_save);
	document.getElementById("totalcost").innerHTML = adddollar (total_cost);
	document.getElementById("totalnet").innerHTML = adddollar (total_net);

	maxreturn = roundThis (parseFloat (total_net) / parseFloat (total_cost)  * 100, 0);
	document.getElementById("totalreturn").innerHTML = maxreturn  + "%";
	document.getElementById("annualreturn").innerHTML = roundThis ((maxreturn / 5), 0) + "%";

	while (x <= 5) {
		id_save = "yr" + x + "save";
		id_cost = "yr" + x + "cost";
		id_net = "yr" + x + "net";
		id_label = "yr" + x + "label";
		document.getElementById(id_save).innerHTML = " ";
		document.getElementById(id_cost).innerHTML = " ";
		document.getElementById(id_net).innerHTML = " ";
		document.getElementById(id_label).innerHTML = " ";
		x++;
	}

/*

	totalsavings = roundThis (annsavings * 5, 0);
	document.getElementById("yr1save").innerHTML = adddollar (annsavings);
	document.getElementById("yr2save").innerHTML = adddollar (annsavings);
	document.getElementById("yr3save").innerHTML = adddollar (annsavings);
	document.getElementById("yr4save").innerHTML = adddollar (annsavings);
	document.getElementById("yr5save").innerHTML = adddollar (annsavings);
	document.getElementById("totalsave").innerHTML = adddollar (totalsavings);

	maxcost = roundThis ((equipcost + datacenter + installcost) + (datacenter * 4), 0);
	document.getElementById("yr1cost").innerHTML = adddollar (roundThis (equipcost + datacenter + installcost, 0));
	document.getElementById("yr2cost").innerHTML = adddollar (datacenter);
	document.getElementById("yr3cost").innerHTML = adddollar (datacenter);
	document.getElementById("yr4cost").innerHTML = adddollar (datacenter);
	document.getElementById("yr5cost").innerHTML = adddollar (datacenter);
	document.getElementById("totalcost").innerHTML = adddollar (maxcost);

	document.getElementById("yr1net").innerHTML = roundThis (parseFloat (annsavings) - parseFloat (equipcost + datacenter + installcost), 0);
	document.getElementById("yr2net").innerHTML = roundThis (parseFloat (annsavings) - parseFloat (datacenter), 0);
	document.getElementById("yr3net").innerHTML = roundThis (parseFloat (annsavings) - parseFloat (datacenter), 0);
	document.getElementById("yr4net").innerHTML = roundThis (parseFloat (annsavings) - parseFloat (datacenter), 0);
	document.getElementById("yr5net").innerHTML = roundThis (parseFloat (annsavings) - parseFloat (datacenter), 0);
	document.getElementById("totalnet").innerHTML = roundThis (parseFloat (annsavings) + parseFloat (datacenter * 4));

	maxreturn = roundThis (parseFloat (document.getElementById("totalnet").innerHTML) / parseFloat (document.getElementById("totalcost").innerHTML)  * 100, 0);
	document.getElementById("totalreturn").innerHTML = maxreturn  + "%";
	document.getElementById("annualreturn").innerHTML = roundThis ((maxreturn / 5), 0) + "%";
	// document.getElementById("maxroi").innerHTML = roundThis ((maxreturn / 5), 0) + "%";
*/

}

function roundThis (num, dec) {
	factor = Math.pow (10, parseInt (dec));
	newnum = Math.round (num * factor);
	return newnum / factor;
}

function updateopt () {
	tanksize = parseInt(document.forms.roi.tanksize.value);
	optgal = Math.round(tanksize * .8);
	document.forms.roi.optgal.value = optgal;
}

function adddollar (str) {
	str = str.toString();
	if (str.substr(0,1) == "-") {
		ret = "-$" + str.substring(1);
	} else {
		ret = "$" + str;
	}
	return ret;
}