//*******************************************
//DO NOT REMOVE THIS COPYWRITE INFO!
//Auto Loan Rebate/Financing Comparison
//2002 Daniel C. Peterson ALL RIGHTS RESERVED
//Created: 10/18/2002
//Last Modified: 10/18/2002
//This script may not be copied, edited, distributed or reproduced
//without express written permission from
//Daniel C. Peterson of Web Winder Website Services
//For commercial use rates, contact:
//Dan Peterson:
//Web Winder Website Services
//P.O. Box 11
//Bemidji, MN  56619
//dan@webwinder.com
//http://www.webwinder.com
//Commercial User Licence #:5782-1237-74-1198
//Commercial Licence Date:2008-09-11
//*******************************************



function stripNum(num) {

   num=num.toString();


   var len = num.length;
   var rnum = "";
   var test = "";
   var j = 0;

   var b = num.substring(0,1);
   if(b == "-") {
      rnum = "-";
   }

   for(i = 0; i <= len; i++) {

      b = num.substring(i,i+1);

      if(b == "0" || b == "1" || b == "2" || b == "3" || b == "4" || b == "5" || b == "6" || b == "7" || b == "8" || b == "9" || b == ".") {
         rnum = rnum + "" + b;

      }

   }

   if(rnum == "" || rnum == "-") {
      rnum = 0;
   }

   rnum = Number(rnum);

   return rnum;

}



function computeMonthlyPayment(prin, numPmts, intRate) {

var pmtAmt = 0;

if(intRate == 0) {
   pmtAmt = prin / numPmts;
} else {
   
   if (intRate >= 1.0) {
     intRate = intRate / 100.0;
   }
   intRate /= 12;

   var pow = 1;
   for (var j = 0; j < numPmts; j++)
      pow = pow * (1 + intRate);

   pmtAmt = (prin * pow * intRate) / (pow - 1);

}

return pmtAmt;

}




function computeFixedInterestCost(principal, intRate, pmtAmt) { 

   var i = eval(intRate);
   if(i >= 1) {
   i /= 100;
   }
   i /= 12;

   var prin = eval(principal);
   var intPort = 0;
   var accumInt = 0;
   var prinPort = 0;
   var pmtCount = 0;
   var testForLast = 0;


   //CYCLES THROUGH EACH PAYMENT OF GIVEN DEBT
   while(prin > 0) {

      testForLast = (prin * (1 + i));

      if(pmtAmt < testForLast) {
         intPort = prin * i;
         accumInt = eval(accumInt) + eval(intPort);
         prinPort = eval(pmtAmt) - eval(intPort);
         prin = eval(prin) - eval(prinPort);
      } else {
      //DETERMINE FINAL PAYMENT AMOUNT
      intPort = prin * i;
      accumInt = eval(accumInt) + eval(intPort);
      prinPort = prin;
      prin = 0;
      }

      pmtCount = eval(pmtCount) + eval(1);

      if(pmtCount > 1000 || accumInt > 1000000000) {
         prin = 0;
      }

   }

return accumInt;

}




function formatNumber(num) {

var isNeg=0;

    if(num < 0) {
       num=num*-1;
       isNeg=1;
    }

    
	onum=Math.round(num*100)/100;
		
	integer=Math.floor(onum);

	if (Math.ceil(onum) == integer) {
		decimal="00";
	} else{
		decimal=Math.round((onum-integer)*100)
	}
	decimal=decimal.toString();
	if (decimal.length<2) decimal="0"+decimal;

	integer=integer.toString();
	var tmpnum="";
	var tmpinteger="";
	var y=0;

	for (x=integer.length;x>0;x--) {
		tmpnum=tmpnum+integer.charAt(x-1);
		y=y+1;
		if (y==3 & x>1) {
			tmpnum=tmpnum+",";
			y=0;
		}
	}

	for (x=tmpnum.length;x>0;x--) {
		tmpinteger=tmpinteger+tmpnum.charAt(x-1);
	}
		
	finNum=tmpinteger+"."+decimal;

    if(isNeg == 1) {
       finNum = "-" + finNum;
    }

	return finNum;
}




function ATEarnSingleDep(prin, intRate, numMonths, numCompPerYr, fedStTaxRate) {

var i = 0;
var intEarn = 0;
var singleFV = prin;

if(intRate >= 1) {
   intRate /= 100;
}

if(fedStTaxRate == "" || fedStTaxRate == 0) {
   fedStTaxRate = 0;
} else {
   if(fedStTaxRate >= 1) {
      fedStTaxRate /= 100;
   }
}

if(numCompPerYr == "" || numCompPerYr == 0) {
   numCompPerYr = 12;
}
intRate /= numCompPerYr;

var numPeriods = numMonths / 12 * numCompPerYr;

var accumAnnInt = 0;
var accumTotEarn = 0;
var tax = 0;

for(i=1; i <= numPeriods; i++) {
   intEarn = singleFV * intRate;

   accumAnnInt = eval(accumAnnInt) + eval(intEarn);
   accumTotEarn = eval(accumTotEarn) + eval(intEarn);
   singleFV = eval(singleFV) + eval(intEarn);

   if(i % numCompPerYr == 0) {
      tax = fedStTaxRate * accumAnnInt;
      accumTotEarn = eval(accumTotEarn) - eval(tax);
      singleFV = eval(singleFV) - eval(tax);
      accumAnnInt = 0;
   }
   
}

return accumTotEarn;

}

function computeForm(form) {
if(form.specIntRate.value.length == 0) {
   alert("Please the special dealer financing rate.");
   form.specIntRate.focus();
} else
if(form.regIntRate.value.length == 0) {
   alert("Please the regular (non-rebate) financing rate.");
   form.regIntRate.focus();
} else
if(form.rebateAmt.value.length == 0) {
   alert("Please the amount of the rebate.");
   form.rebateAmt.focus();
} else
if(form.saveIntRate.value.length == 0) {
   alert("Please enter your savings interest rate.");
   form.saveIntRate.focus();
} else
if(form.price.value.length == 0 || form.price.value == 0) {
   alert("Please enter the price of your vehicle.");
   form.price.focus();
} else
if(form.months.value.length == 0 || form.months.value == 0) {
   alert("Please enter the loan term expressed as number of months.");
   form.months.focus();
} else
if(form.taxRate.value.length == 0) {
   alert("Please enter your combined state and federal tax rate.");
   form.months.focus();
} else {

var VspecIntRate = stripNum(form.specIntRate.value);
var VregIntRate = stripNum(form.regIntRate.value);
var VrebateAmt = stripNum(form.rebateAmt.value);
var VsaveIntRate = stripNum(form.saveIntRate.value);
var Vprice = stripNum(form.price.value);
var VdownPay = stripNum(form.downPay.value);
var Vmonths = stripNum(form.months.value);
var VtaxRate = stripNum(form.taxRate.value);
var VrebateApply = form.rebateApply.selectedIndex;

//CALCULATE POTENTIAL INTEREST EARNINGS ON REBATE
var savingsEarn = ATEarnSingleDep(VrebateAmt, VsaveIntRate, Vmonths, 12, VtaxRate);

//COMPUTE PRINCIPAL & PAYMENT FOR SPECIAL FINANCING
var VspecialPrin = eval(Vprice) - eval(VdownPay);
var VspecialPmt = computeMonthlyPayment(VspecialPrin, Vmonths, VspecIntRate);

//COMPUTE INTEREST COST FOR SPECIAL FINANCING
var VspecialIntCost = computeFixedInterestCost(VspecialPrin, VspecIntRate, VspecialPmt);


//IF APPLYING REBATE TO DOWNPAYMENT
if(VrebateApply == 1) {
   VdownPay = eval(VdownPay) + eval(VrebateAmt);
}

//COMPUTE INTEREST COST FOR REBATE FINANCING
var VrebatePrin = eval(Vprice) - eval(VdownPay);
var VrebatePmt = computeMonthlyPayment(VrebatePrin, Vmonths, VregIntRate);

var VrebateIntCost = computeFixedInterestCost(VrebatePrin, VregIntRate, VrebatePmt);

//SUBTRACT REBATE FROM REBATE LOAN INTEREST COST
VrebateIntCost = eval(VrebateIntCost) - eval(VrebateAmt);

//IF INVEST REBATE INTO SAVINGS, SUBTRACT INT EARN FROM INT COST
if(VrebateApply == 0) {
   VrebateIntCost = eval(VrebateIntCost) - eval(savingsEarn);
}

var VloanType = "";
var Vsavings = 0;

if(VrebateIntCost < VspecialIntCost) {
   VloanType = "Rebate";
   Vsavings = eval(VspecialIntCost) - eval(VrebateIntCost);
} else {
   VloanType = "Special financing";
   Vsavings = eval(VrebateIntCost) - eval(VspecialIntCost);
}

form.loanType.value = VloanType;
form.savings.value = formatNumber(Vsavings);

   }
}

function clearResults(form) {

form.loanType.value = "";
form.savings.value = "";

}