// JavaScript Document

function compute_down(which){

	var mortgage = document.MortgageForm;
	var percentvalue, down, loan;
	/* preprocess loanamount */

	loan = mortgage.loanamount.value;
	while ((pos=loan.indexOf(",")) >= 0){
		temp1 = loan.substring(0, pos);
		temp2 = loan.substring(pos+1, loan.length);
		loan = temp1 + temp2;
    }

    /* preprocess downamount */
    down = mortgage.downamount.value;
    while ((pos=down.indexOf(",")) >= 0){
	    temp1 = down.substring(0, pos);
    	temp2 = down.substring(pos+1, down.length);
    	down = temp1 + temp2;
    }

	if (which == "downamount"){
		percentvalue = Math.floor((parseFloat(down)/parseFloat(loan)*100.0)*100) / 100;
		mortgage.percent.value = percentvalue;
	}
	
	if (which == "percent"){
		down = parseInt(parseFloat(loan) * parseFloat(mortgage.percent.value) / 100.0);
		mortgage.downamount.value = down;
	}

	/* put comma in dollar values */
	
	mortgage.loanamount.value = comma_it(mortgage.loanamount.value);
	mortgage.downamount.value = comma_it(mortgage.downamount.value);
}

function compute(){

	var mortgage = document.MortgageForm;
	var annualRate, monthRate, months, principle, payment;
	var loan, down, pos, temp1, temp2;

    /* validate certain values */
    if (parseInt(mortgage.loanamount.value) <= 0){
	    if (parseInt(mortgage.loanamount.defaultValue) > 0){
	        mortgage.loanamount.value = mortgage.loanamount.defaultValue;
		}
		else {
	        mortgage.loanamount.value = "250000";
		}
	}

    if (parseInt(mortgage.downamount.value) < 0){
	    if (parseInt(mortgage.downamount.defaultValue) >= 0){
			mortgage.downamount.value = mortgage.downamount.defaultValue;
			mortgage.percent.value = mortgage.percent.defaultValue;
		}
		else {
	        mortgage.downamount.value = parseInt(parseFloat(mortgage.loanamount.value) * 20.0 / 100.0);
			mortgage.percent.value = "20.0";
		}
	}

    if (parseInt(mortgage.percent.value) < 0){
	    if (parseInt(mortgage.percent.defaultValue) >= 0){
			mortgage.downamount.value = mortgage.downamount.defaultValue;
			mortgage.percent.value = mortgage.percent.defaultValue;
		}
		else {
			mortgage.downamount.value = parseInt(parseFloat(mortgage.loanamount.value) * 20.0 / 100.0);
			mortgage.percent.value = "20.0";
		}
	}

    if (parseFloat(mortgage.rate.value) < 0.0){
		if (parseFloat(mortgage.rate.defaultValue) > 0.0){
			mortgage.rate.value = mortgage.rate.defaultValue;
		}
	    else {
		mortgage.rate.value = "8.5";
		}
	}

    if (parseInt(mortgage.year.value) <= 0) {
	    if (parseInt(mortgage.year.defaultValue) > 0) {
			mortgage.year.value = mortgage.year.defaultValue;
		}
		else {
			mortgage.year.value = "30";
		}
	}

    /* preprocess loanamount */
    loan = mortgage.loanamount.value;
    while ((pos=loan.indexOf(",")) >= 0) {
	    temp1 = loan.substring(0, pos);
    	temp2 = loan.substring(pos+1, loan.length);
    	loan = temp1 + temp2;
    }

    /* preprocess downamount */
    down = mortgage.downamount.value;
    while ((pos=down.indexOf(",")) >= 0) {
		temp1 = down.substring(0, pos);
		temp2 = down.substring(pos+1, down.length);
		down = temp1 + temp2;
    }

    /* the real computation */
    annualRate = parseFloat(mortgage.rate.value) / 100;
    monthRate = annualRate / 12.0;
    months = parseInt(mortgage.year.value) * 12;
    principle = parseInt(loan) - parseInt(down);
    payment = Math.floor((principle*monthRate)/(1-Math.pow((1+monthRate),(-1*months)))*100)/100;

    /* put value up */
    document.getElementById("mortgage.loan").innerHTML = formatNumber( principle, 2 );
    document.getElementById("mortgage.numberof").innerHTML = months;
    document.getElementById("mortgage.monthly").innerHTML = formatNumber( payment, 2 );

    /* put comma in dollar values */
		mortgage.loanamount.value = comma_it(mortgage.loanamount.value);
    mortgage.downamount.value = comma_it(mortgage.downamount.value);
}

function comma_it(target){

	var newtarget, decimal, pos, temp1, temp2, i;
	newtarget = "";

    /* get rid of existing commas */
	while ((pos=target.indexOf(",")) >= 0) {
		temp1 = target.substring(0, pos);
		temp2 = target.substring(pos+1, target.length);
		target = temp1 + temp2;
    }

    /* extract decimals for safe keeping */
    decimal = "";
    if ((pos=target.indexOf(".")) >= 0){
	    decimal = target.substring(pos, target.length);
		target = target.substring(0, pos);
	}

    /* here comes the real work */
    for (i = target.length-1; i >= 0; i--) {
		if (((target.length-i-1) % 3) == 0) {
			if ((target.length-i-1) > 0) {
				newtarget = "," + newtarget;
			}
		}
	
	newtarget = target.substring(i,i+1) + newtarget;
	}

    /* add on any decimals */
    newtarget = newtarget + decimal;
    return newtarget;
}