//<script>
function Calc(whichElement) {
	var f = whichElement.form
	var InitialValue = whichElement.value
	
	//alert(whichElement.name)
	var EstimatedDayUses = f.EstimatedDayUses
	var NightUsers = f.NightUsers
	var DayUsers = f.DayUsers
	var AnnualGrowth = f.AnnualGrowth
	var HowLong = f.HowLong
	var CalcLoad = f.CalcLoad
	var FinalSize = f.FinalSize
	var Microflush = f.Microflush
	var NonFlush = f.NonFlush
	var MaxPeriod = f.MaxPeriod
	var MinSizeMicroFlush = f.MinSizeMicroFlush
	var MinSizeNonFlush = f.MinSizeNonFlush
	
	var MicroFlushFactor = 3.5
	var NonFlushFactor = 1.2
	
	var MicroFlushRating = ""
	var NonFlushRating = ""
	var MFLitres = ""
	var NFLitres = ""
	var SystemRating
	var DayAndNight
	
	if (whichElement == EstimatedDayUses && (whichElement.value != "" && Number(whichElement.value) != 0 ) ) {
		//Disable NightUsers & DayUsers if you are using EstimatedDayUses
		DisableField(NightUsers)
		DisableField(DayUsers)
	} else if (whichElement == EstimatedDayUses && Number(whichElement.value) == 0 ) {
		//Re-enable NightUsers & DayUsers
		EnableField(NightUsers)
		EnableField(DayUsers)
	} else if ((whichElement == NightUsers || whichElement == DayUsers) && whichElement.value != "" && Number(whichElement.value) != 0 ) {
		//Disable EstimatedDayUses if you are using NightUsers or DayUsers
		DisableField(EstimatedDayUses)
	} else if ((whichElement == NightUsers || whichElement == DayUsers) && (Number(NightUsers.value) == 0 && Number(DayUsers.value) == 0) ) {
		//Re-enable EstimatedDayUses
		EnableField(EstimatedDayUses)
		
	} 
	
	var ActualCalcLoadOverride = (whichElement.name == "CalcLoad" || (NightUsers.value == "" && DayUsers.value == "")) && (!isNaN(CalcLoad.value) && CalcLoad.value != "" && CalcLoad.value != "0")
	//Note: ActualCalcLoadOverride is used to determine whether the value in this field shoul be use to calculate the final system rating.
	
	//alert(NightUsers.value == "" )
	//alert(DayUsers.value == "" )
	//alert(!isNaN(CalcLoad.value) && CalcLoad.value != "" && CalcLoad.value != "0" )
	//alert("ActualCalcLoadOverride=" + ActualCalcLoadOverride)
	
	var DayUserAdj = DayUsers.value * 2 / 3.5
	DayAndNight = Number(NightUsers.value) + DayUserAdj

	//alert("DayAndNight = " + DayAndNight )
	
	if (Number(EstimatedDayUses.value) > 0) {
		DayAndNight =  Number(EstimatedDayUses.value) / 3.5 * 1.25
		SystemRating = DayAndNight
	} else {
		SystemRating = DayAndNight * 1.25 //* Math.pow((AnnualGrowth.value * 0.01 + 1), HowLong.value)
	}
	SystemRating = SystemRating * Math.pow((AnnualGrowth.value * 0.01 + 1), HowLong.value)
	
	var ValueHasChanged = false
	if (Math.round(SystemRating) != InitialValue) ValueHasChanged = true 
		
	//alert("SystemRating = " + SystemRating)
	if (ActualCalcLoadOverride) {
		//alert("1")
		var ActualCalcLoad = CalcLoad.value
		var SystemRating = GetRating(ActualCalcLoad)
	} else {
		//alert("2")
		var ActualCalcLoad = SystemRating
		
	}
	//alert("ActualCalcLoad="+ActualCalcLoad)
	
	var IsTooGreat = ActualCalcLoad > 300
	SystemRating = GetRating(ActualCalcLoad)
	
	if (IsTooGreat) {
		//alert("A")
	} else {
		//alert("B")
		var MicroFlushRating = Math.round(SystemRating * MicroFlushFactor)
		var NonFlushRating = Math.round(SystemRating * NonFlushFactor)
		var MaxPeriodValue = ""
		
		if (!isNaN(MaxPeriod.value) && MaxPeriod.value != "") {
			MaxPeriodValue = Number(MaxPeriod.value)
			MFLitres = GetHoldingTankSize(MaxPeriodValue * MicroFlushRating)
			NFLitres = GetHoldingTankSize(MaxPeriodValue * NonFlushRating)
		}
	}
	
	
	if ((NightUsers.value != "" || DayUsers.value != "" || CalcLoad.value != "" ) ) {
		//alert("D")
		if (ActualCalcLoadOverride && ValueHasChanged) {
			NightUsers.value = ""
			DayUsers.value = ""
		} else {
			CalcLoad.value = Math.round(ActualCalcLoad)
		}
			
		FinalSize.value = SystemRating
		Microflush.value = MicroFlushRating
		NonFlush.value = NonFlushRating
			
		MinSizeMicroFlush.value = MFLitres
		MinSizeNonFlush.value = NFLitres
		
	} else {
		//alert("E")
		CalcLoad.value = "0"
		FinalSize.value = "0"
		Microflush.value = "0"
		NonFlush.value = "0"
		MinSizeMicroFlush.value = "0"
		MinSizeNonFlush.value = "0"
		//NightUsers.focus()
	}
//	alert ("SystemRating = " + SystemRating)
//	alert("MicroFlushRating = " + MicroFlushRating)
//	alert("NonFlushRating = " + NonFlushRating)

	if (!isNaN(whichElement.value) && whichElement.value != "") whichElement.value = Number(whichElement.value)
	
	//HandleKeyPress()
	
	return false
}


function GetRating(v) {
	var r
	v = Number(v)
	if (v == 0) {
		r = 0
	} else if (Math.max(v,6) == 6){
		r = 6
	} else if (Math.max(v,10)==10) {
		r = 10
	} else if (Math.max(v,25)==25) {
		r = 25
	} else if (Math.max(v,50)==50) {
		r = 50
	} else if (Math.max(v,75)==75) {
		r = 75
	} else if (Math.max(v,100)==100){
		r = 100
	} else if (Math.max(v,125)==125){
		r = 125
	} else if (Math.max(v,150)==150) {
		r = 150
	} else if (Math.max(v,175)==175){
		r = 175
	} else if (Math.max(v,200)==200){
		r = 200
	} else if (Math.max(v,225)==225){
		r = 225
	} else if (Math.max(v,250)==250){
		r = 250
	} else if (Math.max(v,275)==275){
		r = 275
	} else if (Math.max(v,300)==300){
		r = 300
	} else if (v > 300) {
		r = "> 300"
	}
	return r
}

function GetHoldingTankSize(v) {
	var r
	v = Number(v)
	if (Math.max(v,200) == 200){
		r = 200
	} else if (Math.max(v,600)== 600) {
		r = 600
	} else if (Math.max(v,1000)==1000) {
		r = 1000
	} else if (Math.max(v,2500)==2500) {
		r = 2500
	} else if (Math.max(v,5500)==5500) {
		r = 5500
	} else if (v > 5500) {
		r = "See Note"
	} 
	return r
}
function PrintFriendly(b) {
	if (b.name == "PrintFriendlyButton") {
		var f = document.CalcForm
		f.method = "POST"
		f.action = "hts_calc_print.asp"
		f.target = "_blank"
		f.submit()
	}
	return false
}

function HandleKeyPress()
{
	if (document.activeElement) {
		var AE = document.activeElement
		
		switch (event.keyCode) {
			case 13 :
				if (AE.type && AE.type.toUpperCase() != "TEXTAREA") {
					event.returnValue=false;
					var f = document.CalcForm
					//var ElementFound = false
					var nextAvailableField = ""
					for (var i = 0; i < f.elements.length; i++) {
						
						if (f.elements[i] == AE) {
							//move cursor to next available field
							//alert("match : " + f.elements[i].name)
							//break;
							for (var j = i; j < f.elements.length; j++ ) {
								//search for the next selectable field
								
								//alert(f.elements[j].name)
								
								if (!f.elements[j].disabled && f.elements[j].focus) {
									
									nextAvailableField = f.elements[j]
									alert(nextAvailableField.name)
									
									if (nextAvailableField != "" && !nextAvailableField.disabled && nextAvailableField.focus && nextAvailableField.select) {
										nextAvailableField.focus()
										nextAvailableField.select()
										
									}
									
									break;
								}
								
								//if (nextAvailableField != "" ) break;
							}
							break;
						}
						
						//if (nextAvailableField != "" ) break;
					}
					//DoSearch();
					//alert()
					//break
				}
			default:
				break
		}
	}
	return false
}
function DisableField (whichElement) {
	whichElement.disabled = true
	whichElement.value = "Unused"
	//if (whichElement.form.activeElement == whichElement) {
		
	//}
}

function EnableField (whichElement) {
	whichElement.disabled = false
	whichElement.value = ""
}

//document.onkeypress=HandleKeyPress;