function input_money(value){
	while ((i=value.indexOf(",")) >= 0) {
		value = value.substring(0,i) + value.substring(i+1,value.length);
	}
	i=parseInt(value);
	return i;
}

function format_money(value) {

	var result = "";
	value += ""; 

	if (value.length > 6)
		result = (value.substring(0, (value.length - 6))) + "," + 
				(value.substring((value.length - 6), (value.length - 3))) + "," + 
				(value.substring((value.length - 3), value.length));
	else{

		if (value.length > 3)
			result = (value.substring(0, (value.length - 3))) + "," + 
					(value.substring((value.length - 3), value.length));

		else 
			result = value;
	}
	return result;
}


function calcRepay(repayments) {

var amt = repayments.loan_amount.value;
amt = input_money(amt);
var interest = parseFloat(repayments.interest_rate.value);
var term = parseInt(repayments.term.options[repayments.term.selectedIndex].value);
var type = repayments.rate_type.options[repayments.rate_type.selectedIndex].value;
var freq = repayments.period.options[repayments.period.selectedIndex].value;

if ((isNaN(amt)) || (amt <= 0)){
	alert("You entered an invalid Loan Amount. Please enter an amount higher than $0.");
	return;
	}

else if ((interest <= 0) || (interest >= 100)){
	alert("You entered an invalid Interest Rate. Please enter a number between 0 and 100.");
	return;
	} 

else {

var int_month = (interest/100.0)/12;
var int_fort = (interest/100.0)/26;
var int_week = (interest/100.0)/52;

if(freq == "month"){

	var calc_term = term * 12;
	var calc_int = (interest/100.0)/12;
	var calc_rate = 1.0+calc_int;
}

else{
	if(freq == "fortnight"){
		var calc_term = term * 26;
		var calc_int = (interest/100.0)/26;
		var calc_rate = 1.0+calc_int;
	}
		else{
			var calc_term = term * 52;
			var calc_int = (interest/100.0)/52;
			var calc_rate = 1.0+calc_int;
		}
}

if (type == "P_and_I") { 
 
	var ann = Math.pow(calc_rate, calc_term);
	var repay = amt * calc_int * ann / (ann - 1);
}

else { 

	var repay = (calc_int * amt);
} 

repay = Math.round(repay);
repay = format_money(repay);
repayments.repay_amount.value = repay;
repayments.loan_amount.value = format_money(amt);
repayments.frequency.value = freq;

} 
}