//		Title: 		Pension Caculator
//		Version: 		2.0
//		Last Update:	4 October 2000
//
//

function formatText(num)  {
   var i, count=0;
   var text="";
   
   for (i=num.length;i>=0;i--)  {
      if (count==4) {
         count = 	1;
         text = num.substr(i,1) + "," + text;
      } else {
         text = num.substr(i,1) + text;
      }
      count = count + 1;
   }
   return text;
}

function clearResult(form)  {
   document.all.tb_mandatoryportion.innerHTML = "0";
   document.all.tb_voluntaryportion.innerHTML = "0";
   document.all.tb_amountatretirement.innerHTML = "0";
   document.all.tb_amountattodayvalue.innerHTML = "0";
   document.all.tb_noofyear.innerHTML = "0";
}


function Format()  {
   this.toNumber = toNumber;
}

function toNumber(num)   {
var result = "";

return result;
}
// Field Checking
function checkMonthlyIncome(form) {
   clearResult(form);
   if (form.tb_monthlyincome.value=="") {
      alert("請輸入每月現金入息。"); 
       form.tb_monthlyincome.focus();
      return false;
 }

  if (isNaN(form.tb_monthlyincome.value) || form.tb_monthlyincome.value<0) {
    alert("每月現金入息必須為正數，請再輸入。");
    form.tb_monthlyincome.focus();
    return  false;
 }
  return true;
}

function checkIncomeGrowthRate(form) {
   clearResult(form);
   if (form.tb_incomegrowthrate.value=="") {
      alert("請輸入每年現金入息之加幅。"); 
      form.tb_incomegrowthrate.focus();
      return false;
   }

   if (isNaN(form.tb_incomegrowthrate.value)) {
      alert("每年現金入息之加幅必須為數字，請再輸入。"); 
      form.tb_incomegrowthrate.focus();
      return false;
   }
   return true;
}

function checkEmployerVoluntaryContribution(form) {
   clearResult(form);
   if (form.tb_employervoluntarycontribution.value=="") {
      alert("請輸入僱主之自願性供款佔現金入息。");
      form.tb_employervoluntarycontribution.focus();
      return false;
   }
   if (isNaN(form.tb_employervoluntarycontribution.value)) {
      alert("僱主之自願性供款佔現金入息必須為數字，請再輸入。");
      form.tb_employervoluntarycontribution.focus();
      return false;
   }
   if (form.tb_employervoluntarycontribution.value<0 || form.tb_employervoluntarycontribution.value>100) {
      alert("僱主之自願性供款佔現金入息必須介乎於0至100之間。");
      form.tb_employervoluntarycontribution.focus();
      return false;
   }
   return true;
}

function checkEmployeeVoluntaryContribution(form) {
   clearResult(form);
   if (form.tb_employeevoluntarycontribution.value=="") {
      alert("請輸入閣下之自願性供款佔現金入息。");
      form.tb_employeevoluntarycontribution.focus();
      return false;
   }
   if (isNaN(form.tb_employeevoluntarycontribution.value)) {
      alert("閣下之自願性供款佔現金入息必須為數字，請再輸入。");
      form.tb_employeevoluntarycontribution.focus();
      return false;
   }
   if (form.tb_employeevoluntarycontribution.value<0 || form.tb_employeevoluntarycontribution.value>100) {
      alert("閣下之自願性供款佔現金入息必須介乎於0至100之間。");
      form.tb_employeevoluntarycontribution.focus();
      return false;
   }
   return true;
}

function checkAge(form) {
	
	clearResult(form);
	if ( form.dd_age.value == "" ) {
   		alert("請輸入現時之年齡。");
   		form.dd_age.focus();
   		return false;
	}
	if (isNaN(form.dd_age.value)) {
      	alert("現時之年齡必須為數字，請再輸入。");
      	form.dd_age.focus();
      	return false;
   	}
   	if (form.dd_age.value<18 || form.dd_age.value>65) {
    	alert("現時之年齡必須介乎於18至65之間。");
      	form.dd_age.focus();
      	return false;
   }
   return true;
}

function checkRetirementAge(form)  {
   clearResult(form);
   if ( form.dd_retirementage.value == "" ) {
   		alert("請輸入退休年齡。");
   		form.dd_retirementage.focus();
   		return false;
	}
	if (isNaN(form.dd_retirementage.value)) {
      	alert("退休年齡必須為數字，請再輸入。");
      	form.dd_retirementage.focus();
      	return false;
   	}
   	if (form.dd_retirementage.value<60 || form.dd_retirementage.value>65) {
    	alert("退休年齡必須介乎於60至65之間。");
      	form.dd_retirementage.focus();
      	return false;
   }
   return true;
}

function checkInvestmentReturn(form) {
   clearResult(form);
   if (form.tb_investmentreturn.value=="") {
      alert("請輸入投資回報率。");
      form.tb_investmentreturn.focus();
      return false;
   }
   if (isNaN(form.tb_investmentreturn.value)) {
      alert("投資回報率必須為數字，請再輸入。");
      form.tb_investmentreturn.focus();
      return false;
   }
   if (form.tb_investmentreturn.value<-100 || form.tb_investmentreturn.value>100)   {
      alert("投資回報率必須介乎於-100至100之間，請再輸入。");
      form.tb_investmentreturn.focus();
      return false;
   }
   return true;
}

function checkInflationRate(form) {
   clearResult(form);
   if (form.tb_inflationrate.value=="") {
      alert("請輸入通脹率。");
      form.tb_inflationrate.focus();
      return false;
   }
   if (isNaN(form.tb_inflationrate.value)) {
      alert("通脹率必須為數字，請再輸入。");
      form.tb_inflationrate.focus();
      return false;
   }
   if (form.tb_inflationrate.value<-50 || form.tb_inflationrate.value>50)   {
      alert("通脹率必須介乎於-50至50之間，請再輸入。");
      form.tb_inflationrate.focus();
      return false;
   }
   return true;
}

function checkAgeDiff(form)   {
   clearResult(form);
   if (form.dd_age.value=="") {
      alert("請輸入現時之年齡。");
      form.dd_age.focus();
      return false;
   }
   
   if (isNaN(form.dd_age.value)) {
      	alert("現時之年齡必須為數字，請再輸入。");
      	form.dd_age.focus();
      	return false;
   	}
   	if (form.dd_age.value<18 || form.dd_age.value>65) {
    	alert("現時之年齡必須介乎於18至65之間。");
      	form.dd_age.focus();
      	return false;
   }

   if (form.dd_retirementage.value=="") {
      alert("請輸入退休年齡。");
      form.dd_retirementage.focus();
      return false;
   }
   
   if (isNaN(form.dd_retirementage.value)) {
      	alert("退休年齡必須為數字，請再輸入。");
      	form.dd_retirementage.focus();
      	return false;
   	}
   	if (form.dd_retirementage.value<60 || form.dd_retirementage.value>65) {
    	alert("退休年齡必須介乎於60至65之間。");
      	form.dd_retirementage.focus();
      	return false;
   }
   
   if ((form.dd_retirementage.value-form.dd_age.value) <= 0 )   {
      alert("退休年齡必須大於現時之年齡。");
      form.dd_age.focus();
      return false; 
   }
   return true;
}
   
   
// Employee
function Employee(form)  {
 this.MonthlyIncome = getMonthlyIncome(form);
 this.IncomeGrowthRate = getIncomeGrowthRate(form);
 this.EmployerVoluntaryContribution = getEmployerVoluntaryContribution(form);
 this.EmployeeVoluntaryContribution = getEmployeeVoluntaryContribution(form);
 this.Age = getAge(form);
 this.RetirementAge = getRetirementAge(form);
 this.InvestmentReturn = getInvestmentReturn(form);
 this.InflationRate = getInflationRate(form);
}

function getMonthlyIncome(form) {
   var income = 0;
   income = form.tb_monthlyincome.value * 1;
   return income;
}

function getIncomeGrowthRate(form) {
   var rate = 0;
   rate = form.tb_incomegrowthrate.value * 1;
   return rate;
}

function getEmployerVoluntaryContribution(form) {
   var contribution = 0;
   contribution = form.tb_employervoluntarycontribution.value * 1;
   return contribution;
}

function getEmployeeVoluntaryContribution(form) {
   var contribution = 0;
   contribution = form.tb_employeevoluntarycontribution.value * 1;
   return contribution;
}

function getAge(form) {
   var age = 0;
   age = form.dd_age.value * 1;
   return age;
}

function getRetirementAge(form) {
   var age = 0;
   age = form.dd_retirementage.value * 1;
   return age;
}

function getInvestmentReturn(form) {
   var rate = 0;
   rate = form.tb_investmentreturn.value * 1;
   return rate;
}

function getInflationRate(form) {
   var rate = 0;
   rate = form.tb_inflationrate.value * 1;
   return rate;
}
                                                                                                                             
// Employee's Pension
function EmployeePension(employee) {
   var monthly_income = employee.MonthlyIncome;
   var income_growth_rate = employee.IncomeGrowthRate;
   var employer_voluntary_contribution = employee.EmployerVoluntaryContribution;
   var employee_voluntary_contribution = employee.EmployeeVoluntaryContribution;
   var current_age = employee.Age;
   var investment_return = employee.InvestmentReturn;
   var retirement_age = employee.RetirementAge;
   var employer_mandatory_contribution = 5;
   var employee_mandatory_contribution = 5;
   var inflation_rate = employee.InflationRate;
   var max_income = 20000;  // max. amount to be invested of each month under the government law
   var actual_retirement_age = employee.RetirementAge;  // retiremnet age under the government law
   var year = 0;
   var mandatory = 0;
   var voluntary = 0;
   var return_on_mandatory = 0;
   var return_on_voluntary = 0;
   var amount_mandatory_portion = 0;
   var amount_voluntary_portion = 0;
   var amount_at_today_value = 0;

   // the remaining time to retirement age
   var period = retirement_age - current_age;
   
   // calculate the return of each year
   for (year=0;year<period;year++) {

    // calulate the actual monthly income of that year
      if ((year > 0)) {
         monthly_income = monthly_income * (1 + (income_growth_rate/100));
      }
      
    // calulate the actual max income of that year
      if ((year > 0) && (year % 3 == 0)) {
         max_income = max_income * Math.pow(1 + (inflation_rate/100), 3);
         max_income = Math.round(max_income/1000)*1000;
      }      

    // calculate the actual amount of mandatory contribution to be invested
      if (monthly_income > max_income) {
           if (monthly_income >= 5000) { // if monthly income < 5000, employee would not to contribution
               mandatory = max_income * ((employee_mandatory_contribution + employer_mandatory_contribution)/100);            
           } else {
               mandatory = max_income * ((employer_mandatory_contribution)/100);            
           }
      } else {
           if (monthly_income >= 5000) { // if monthly income < 5000, employee would not to contribution
               mandatory = monthly_income * ((employee_mandatory_contribution + employer_mandatory_contribution)/100);
           } else {
               mandatory = monthly_income * ((employer_mandatory_contribution)/100);
           }
      }
   
    // calculate the actual amount of voluntary contribution to be invested
      voluntary = monthly_income * ((employee_voluntary_contribution + employer_voluntary_contribution)/100);

      //alert(mandatory);
      //alert(voluntary);
      
    // calculate the amount of investment return base on the budget of the mandatory contribution
      return_on_mandatory = calculateYearlyReturn(mandatory, investment_return/100, (actual_retirement_age-current_age-year-1));
	// calculate the amount of investment return base on the budget of the voluntory contribution
      return_on_voluntary = calculateYearlyReturn(voluntary, investment_return/100, (actual_retirement_age-current_age-year-1));   
     
    //  alert(return_on_mandatory);
    //  alert(return_on_voluntary);
      
     // accumulate the amount of investment return of the mandatory contribution
     amount_mandatory_portion = amount_mandatory_portion + return_on_mandatory;     
    // accumulate the amount of investment return of the voluntary contribution
     amount_voluntary_portion = amount_voluntary_portion + return_on_voluntary;
   }

   this.MandatoryPortion = amount_mandatory_portion;
   this.VoluntaryPortion = amount_voluntary_portion;
   this.AmountAtRetirement = Math.round(amount_voluntary_portion + amount_mandatory_portion);
   this.AmountAtTodayValue = this.AmountAtRetirement / Math.pow(1 + (inflation_rate/100), (actual_retirement_age - current_age));
}

function calculateYearlyReturn(principle, rate, period)   {
   var amount=0;
   var rate1=0;
   
   rate1 = Math.pow((1+(rate/12)),12) - 1;
   amount = FV(rate/12,12,principle);
   amount = amount * Math.pow((1+rate1),period);
   
   return amount;
   
}

function FV(rate, period, amount)   {
   var value = 0;
   
   if (rate==0)   {
      value = amount * period;
   } else {
      value = Math.pow(1+rate, period) - 1;
      value = amount*(value/rate);
   } 
     
   return value;
}

// Main
function main(form)  {

  // Valid all required field before calculating the pension
  if (!checkMonthlyIncome(form)) return;
  if (!checkIncomeGrowthRate(form)) return;
  if (!checkEmployerVoluntaryContribution(form)) return;
  if (!checkEmployeeVoluntaryContribution(form)) return;
  if (!checkAge(form)) return;
  if (!checkInvestmentReturn(form)) return;
  if (!checkInflationRate(form)) return;
  if (!checkAgeDiff(form)) return;

  // Create the object of Employee, to collect all required information about the employee
   e = new Employee(form);

  // Create the object of Pension Calculator, to evaluate the pension of the employee
   ep = new EmployeePension(e);

  // Output the results
   //alert(ep.MandatoryPortion);
   //alert(ep.VoluntaryPortion);
   //alert(ep.AmountAtRetirement);
   //alert(ep.AmountAtTodayValue);
   
   document.all.tb_mandatoryportion.innerHTML = Math.round(ep.MandatoryPortion);
   document.all.tb_voluntaryportion.innerHTML = Math.round(ep.VoluntaryPortion);
   document.all.tb_amountatretirement.innerHTML = Math.round(ep.AmountAtRetirement);
   document.all.tb_amountattodayvalue.innerHTML = Math.round(ep.AmountAtTodayValue);
   document.all.tb_noofyear.innerHTML = e.RetirementAge - e.Age;
   
   document.all.tb_mandatoryportion.innerHTML = formatText(document.all.tb_mandatoryportion.innerHTML);
   document.all.tb_voluntaryportion.innerHTML = formatText(document.all.tb_voluntaryportion.innerHTML);
   document.all.tb_amountatretirement.innerHTML = formatText(document.all.tb_amountatretirement.innerHTML);
   document.all.tb_amountattodayvalue.innerHTML = formatText(document.all.tb_amountattodayvalue.innerHTML);
}

function reset(form)
{
	form.tb_monthlyincome.value="";
	form.tb_incomegrowthrate.value="";
	form.dd_age.value="";
	form.dd_retirementage.value="";
	
	form.tb_employervoluntarycontribution.value="";
	form.tb_employeevoluntarycontribution.value="";
	
	form.tb_investmentreturn.value=""
	form.tb_inflationrate.value=""
	
   	document.all.tb_mandatoryportion.innerHTML = "0";
   	document.all.tb_voluntaryportion.innerHTML = "0";
   	document.all.tb_amountatretirement.innerHTML = "0";
   	document.all.tb_amountattodayvalue.innerHTML = "0";
   	document.all.tb_noofyear.innerHTML = "0";
}