function calculatorValue(field)
{
	//this function works only with html input textboxes
	var el = document.getElementById(field);
	if (el == null)
		return 0;
		
	var v = el.value;
	v = convertAmount(v);
	try
	{
		t = parseFloat(v);
		if (isNaN(t))
			return 0;
		
		return t;
	}
	catch(e)
	{
		return 0;
	}
}

function convertAmount(val)
{
	return val;
}

function calculatorSetLabel(field, text)
{
	var el = document.getElementById(field)
	if (el == null)
		return;

	switch(el.tagName.toLowerCase())
	{
		case "span":
			el.innerHTML = text;
			break;
		case "input":
			el.value = text;
			break;
	}
}

function calculateMaximum(submit)
{
	if (submit != null)
	{
		//on submit, some fields are required
		if (calculatorValue('i1') == 0 || calculatorValue('d1') == 0)
		{
			calculatorSetLabel('calculatorerrortext', 'Inkomen en woonlasten zijn verplicht<br/>');
			return 0;
		}
		else
			calculatorSetLabel('calculatorerrortext', '');
	}	
	
	var l = 0;
	var it = calculatorValue('i1') + calculatorValue('i2');
	//levensonderhoud
	if (calculatorValue('i2') == 0)
		l = calculateLO(calculatorValue('i1'), 600);
	else
		l = calculateLO(it, 750);
		
	if (dt >= 3000)
		l = 0.3 * dt;

	var dt = calculatorValue('d1') + calculatorValue('d2') + calculatorValue('d3') + l;
	var t = (it - dt) * 50;
	
	
	calculatorSetLabel('total', t);
	return t;
}

function calculateLO(income, minAmount)
{
	var o = 0.35 * income;
	return Math.max(o, minAmount);
	
}

function calculatorSubmit()
{
	var t = calculateMaximum(true);
	if (t > 0)
		location.href = 'lening-aanvragen.aspx?amount=' + t;
}