// JavaScript Document
// 401k Calculator
// Author : Jesse Kyzar
// Date : Aug. 6, 2004

function perform_calculations(formObj) {
    //clear out any old results
    reset_results(formObj);

    //validate form fields; proceed no further if errors are found 
    if(validate_fields(formObj)) {
		//determine difference between both dates
		var date_diff = date_difference_in_days(formObj);

		//calculate dayes in period
		if(formObj.num_paychecks.value == 52) {
			var period_days = 7;
		}
		else {
			var period_days = Math.round(365 / formObj.num_paychecks.value);
		}

		//calculate compounding periods in first year
		var compounding_periods = Math.round(date_diff / period_days);
		
		//calculate first progressed age fields
		age_progression(formObj, period_days, compounding_periods, date_diff);

		//line 29; causes page to scroll to results		
		location.href = "#scrollTo";

		//show progress; remove later
		//var progress_check = "Date difference : " + date_diff + "\nDays in period : " + period_days + "\nCompounding periods in first year : " + compounding_periods;
		//alert(progress_check);
   }
}

function validate_fields(formObj) {
	//error tracking variables
	var errors = 0;
	var num_errors = 0;
	var messages = "";
	
	//date variables
	var as_of_date = ""; 
	var year_end_date = "";
	
	//validate contribution : required; must be numeric;
	if(formObj.contribution.value.length == 0) {
		errors = errors | 1;
		num_errors++;
		messages = messages + num_errors +  ". 401(k) contribution per paycheck is required.\n";
	}
	else if(isNaN(formObj.contribution.value)) {
		errors = errors | 1;
		num_errors++;
		messages = messages + num_errors +  ". 401(k) contribution per paycheck must be a number.\n";
	}
	
	//validate emp_contribution : required; must be numeric;
	if(formObj.emp_contribution.value.length == 0) {
		errors = errors | 2;
		num_errors++;
		messages = messages + num_errors +  ". 401(k) employer contribution match per paycheck is required.\n";
	}
	else if(isNaN(formObj.emp_contribution.value)) {
		errors = errors | 2;
		num_errors++;
		messages = messages + num_errors +  ". 401(k) employer contribution match per paycheck must be a number.\n";
	}
	
	//validate num_paychecks : required; 
	if(formObj.num_paychecks.value.length == 0) {
		errors = errors | 4;
		num_errors++;
		messages = messages + num_errors +  ". Paychecks per year is required.\n";
	}
	
	//validate return_rate : required; must be numeric;
	if(formObj.return_rate.value.length == 0) {
		errors = errors | 8;
		num_errors++;
		messages = messages + num_errors +  ". Expected annual rate of return is required.\n";
	}
	else if(isNaN(formObj.return_rate.value)) {
		errors = errors | 8;
		num_errors++;
		messages = messages + num_errors +  ". Expected annual rate of return must be a number.\n";
	}	
	
	//validate investment_age : required; must be numeric; must be less than anticipated retirement age;
	if(formObj.investment_age.value.length == 0) {
		errors = errors | 16;
		num_errors++;
		messages = messages + num_errors +  ". Age as of the end of this tax year is required.\n";
	}
	else if(isNaN(formObj.investment_age.value)) {
		errors = errors | 16;
		num_errors++;
		messages = messages + num_errors +  ". Age as of the end of this tax year must be a number.\n";
	}	

	//validate retirement_age : required; must be numeric; must be greater than age as of end of this tax year and less than 90;
	if(formObj.retirement_age.value.length == 0) {
		errors = errors | 32;
		num_errors++;
		messages = messages + num_errors +  ". Anticipated retirement age is required.\n";
	}
	else if(isNaN(formObj.retirement_age.value)) {
		errors = errors | 32;
		num_errors++;
		messages = messages + num_errors +  ". Anticipated retirement age must be a number.\n";	
	}	

	//validate investment_age and retirement_age; retirement_age must be greater;
	if((!isNaN(formObj.investment_age.value)) && (!isNaN(formObj.retirement_age.value)) && ((formObj.investment_age.value > formObj.retirement_age.value) || (formObj.retirement_age.value >= 90))) {
		errors = errors | 16;
		errors = errors | 32;
		num_errors++;
		messages = messages + num_errors + ". Anticipated retirement age must be greater than age as of the end of this tax year and less than 90.\n";
	}
	
	//validate current_value : required; must be numeric;
	if(formObj.current_value.value.length == 0) {
		errors = errors | 64;
		num_errors++;
		messages = messages + num_errors +  ". Current value of 401(k) is required.\n";
	}	
	else if(isNaN(formObj.current_value.value)) {
		errors = errors | 64;
		num_errors++;
		messages = messages + num_errors +  ". Current value of 401(k) must be a number.\n";	
	}
	
	//validate as-of date : must be a valid date; must be less than year-end date;
	if(!validate_dates(formObj.aod_month.value, formObj.aod_day.value, formObj.aod_year.value)) {
		errors = errors | 128;
		num_errors++;
		messages = messages + num_errors +  ". Date (the \"as of\" date for the current value) is invalid.\n";
	}
	else {
		as_of_date = new Date(formObj.aod_month.value + " " + formObj.aod_day.value + ", " + formObj.aod_year.value);
	}
	
	//validate year-end date : must be a valid date; must be greater than as-of date;
	if(!validate_dates(formObj.eoy_month.value, formObj.eoy_day.value, formObj.eoy_year.value)) {
		errors = errors | 256;
		num_errors++;
		messages = messages + num_errors +  ". The date of the year end is invalid.\n";
	}
	else {
		year_end_date = new Date(formObj.eoy_month.value + " " + formObj.eoy_day.value + ", " + formObj.eoy_year.value);
	}
	
	//validate as-of and year end dates; year-end must be greater than as-of;
	if(as_of_date > year_end_date) {
		errors = errors | 128;
		errors = errors | 256;
		num_errors++;
		messages = messages + num_errors + ". The date of the year end must be later than date (the \"as of\" date for the current value).\n";
	}
	
	//validate tax_rate : required; must be numeric;
	if(formObj.tax_rate.value.length == 0) {
		errors = errors | 512;
		num_errors++;
		messages = messages + num_errors +  ". Marginal tax rate is required.";
	}
	else if(isNaN(formObj.tax_rate.value)) {
		errors = errors | 512;
		num_errors++;
		messages = messages + num_errors +  ". Marginal tax rate must be a number.\n";	
	}
	
	if(num_errors == 1) {
	    messages = "An error was found in the information you provided:\n" + messages;
		alert(messages);
		return false;
	}
	else if(num_errors > 1) {
		messages = num_errors + " errors were found in the information you provided:\n" + messages;
		alert(messages);
		return false;	
	} 
	else {
		return true;
	}	
}

function date_difference_in_days(formObj) {
	var as_of_date = new Date(formObj.aod_month.value + " " + formObj.aod_day.value + ", " + formObj.aod_year.value);
	var year_end_date = new Date(formObj.eoy_month.value + " " + formObj.eoy_day.value + ", " + formObj.eoy_year.value);
	return Math.round((((((year_end_date - as_of_date) / 1000) /60) / 60) / 24));
}

function validate_dates(checkMonth, checkDay, checkYear) {
  //make sure month and day are valid 
  switch(checkMonth) {
    //take leap years into account
  	case "February":
		if(checkDay == 29) {
			if((checkYear == 2004) || (checkYear == 2008) || (checkYear == 2012)) {
				return 1;
			}
			else {
				return 0;
			}
		}
		else if(checkDay > 29) {
			return 0;
		}
		else {
			return 1;
		}
	break;
	case "April":
		if(checkDay > 30) {
			return 0;
		}
		else {
			return 1;
		}
	break;
	case "June":
		if(checkDay > 30) {
			return 0;
		}
		else {
			return 1;
		}
	break;	
	case "September":
		if(checkDay > 30) {
			return 0;
		}
		else {
			return 1;
		}
	break;	
	case "November":
		if(checkDay > 30) {
			return 0;
		}
		else {
			return 1;
		}
	break;	
	default :
		return 1;
	break;	
  }
}

function age_progression(formObj, period_days, compounding_periods, date_diff) {
	//determine difference between retirement age and age as of the end of this tax year
	var age_diff = formObj.retirement_age.value - formObj.investment_age.value;

	//set results fields
	if(age_diff <= 5) {
		formObj.results_401k_age1.value = formObj.investment_age.value;
		formObj.results_savings_age1.value = formObj.investment_age.value;
		formObj.results_401k_value1.value = Math.round(((((date_diff / 365) * convert_percent(parseFloat(formObj.return_rate.value))) + 1) * parseFloat(formObj.current_value.value))) + Math.round(future_value((convert_percent(formObj.return_rate.value) / (365 / parseInt(period_days))), parseInt(compounding_periods), (parseFloat(formObj.contribution.value) + parseFloat(formObj.emp_contribution.value))));
		formObj.results_savings_value1.value = Math.round(((((1 - convert_percent(formObj.tax_rate.value)) * convert_percent(formObj.return_rate.value)) * date_diff / 365) + 1) * parseFloat(formObj.current_value.value)) + Math.round(future_value(((1 - convert_percent(formObj.tax_rate.value)) * convert_percent(formObj.return_rate.value)) / (365 / period_days), compounding_periods, (parseFloat(formObj.contribution.value) + parseFloat(formObj.emp_contribution.value))));

		formObj.results_401k_age2.value = formObj.retirement_age.value;
		formObj.results_savings_age2.value = formObj.retirement_age.value;
		formObj.results_401k_value2.value = Math.round(parseInt(formObj.results_401k_value1.value) * (Math.pow((1 + convert_percent(formObj.return_rate.value)), (parseInt(formObj.results_401k_age2.value) - parseInt(formObj.results_401k_age1.value))))) + Math.round(future_value(convert_percent(formObj.return_rate.value) / parseInt(formObj.num_paychecks.value), (parseInt(formObj.results_401k_age2.value) - parseInt(formObj.results_401k_age1.value)) * parseInt(formObj.num_paychecks.value), (parseFloat(formObj.contribution.value) + parseFloat(formObj.emp_contribution.value))));
		formObj.results_savings_value2.value = Math.round(Math.pow((((1 - convert_percent(parseFloat(formObj.tax_rate.value))) * convert_percent(parseFloat(formObj.return_rate.value))) + 1), (parseInt(formObj.results_savings_age2.value) - parseInt(formObj.results_savings_age1.value))) * parseFloat(formObj.results_savings_value1.value)) + Math.round(future_value((convert_percent(parseFloat(formObj.return_rate.value)) * (1 - convert_percent(parseFloat(formObj.tax_rate.value)))) / parseInt(formObj.num_paychecks.value), (parseInt(formObj.results_savings_age2.value) - parseInt(formObj.results_savings_age1.value)) * parseInt(formObj.num_paychecks.value), (parseFloat(formObj.contribution.value) + parseFloat(formObj.emp_contribution.value))));	
	
		formObj.monthly_income_401k.value = payment(parseInt(formObj.results_401k_value2.value), convert_percent(parseFloat(formObj.return_rate.value)), ((90 - parseInt(formObj.retirement_age.value)) * 12));	
		formObj.monthly_income_savings.value = payment(parseInt(formObj.results_savings_value2.value), convert_percent(parseFloat(formObj.return_rate.value)), ((90 - parseInt(formObj.retirement_age.value)) * 12));
	}
	else if((age_diff > 5) && (age_diff <= 15)) {
		formObj.results_401k_age1.value = formObj.investment_age.value;
		formObj.results_savings_age1.value = formObj.investment_age.value;
		formObj.results_401k_value1.value = Math.round(((((date_diff / 365) * convert_percent(parseFloat(formObj.return_rate.value))) + 1) * parseFloat(formObj.current_value.value))) + Math.round(future_value((convert_percent(formObj.return_rate.value) / (365 / parseInt(period_days))), parseInt(compounding_periods), (parseFloat(formObj.contribution.value) + parseFloat(formObj.emp_contribution.value))));
		formObj.results_savings_value1.value = Math.round(((((1 - convert_percent(formObj.tax_rate.value)) * convert_percent(formObj.return_rate.value)) * date_diff / 365) + 1) * parseFloat(formObj.current_value.value)) + Math.round(future_value(((1 - convert_percent(formObj.tax_rate.value)) * convert_percent(formObj.return_rate.value)) / (365 / period_days), compounding_periods, (parseFloat(formObj.contribution.value) + parseFloat(formObj.emp_contribution.value))));

		formObj.results_401k_age2.value = parseInt(formObj.investment_age.value) + 5;
		formObj.results_savings_age2.value = parseInt(formObj.investment_age.value) + 5;
		formObj.results_401k_value2.value = Math.round(parseInt(formObj.results_401k_value1.value) * (Math.pow((1 + convert_percent(formObj.return_rate.value)), (parseInt(formObj.results_401k_age2.value) - parseInt(formObj.results_401k_age1.value))))) + Math.round(future_value(convert_percent(formObj.return_rate.value) / parseInt(formObj.num_paychecks.value), (parseInt(formObj.results_401k_age2.value) - parseInt(formObj.results_401k_age1.value)) * parseInt(formObj.num_paychecks.value), (parseFloat(formObj.contribution.value) + parseFloat(formObj.emp_contribution.value))));
		formObj.results_savings_value2.value = Math.round(Math.pow((((1 - convert_percent(parseFloat(formObj.tax_rate.value))) * convert_percent(parseFloat(formObj.return_rate.value))) + 1), (parseInt(formObj.results_savings_age2.value) - parseInt(formObj.results_savings_age1.value))) * parseFloat(formObj.results_savings_value1.value)) + Math.round(future_value((convert_percent(parseFloat(formObj.return_rate.value)) * (1 - convert_percent(parseFloat(formObj.tax_rate.value)))) / parseInt(formObj.num_paychecks.value), (parseInt(formObj.results_savings_age2.value) - parseInt(formObj.results_savings_age1.value)) * parseInt(formObj.num_paychecks.value), (parseFloat(formObj.contribution.value) + parseFloat(formObj.emp_contribution.value))));

		formObj.results_401k_age3.value = formObj.retirement_age.value;
		formObj.results_savings_age3.value = formObj.retirement_age.value;
		formObj.results_401k_value3.value = Math.round(parseInt(formObj.results_401k_value2.value) * (Math.pow((1 + convert_percent(formObj.return_rate.value)), (parseInt(formObj.results_401k_age3.value) - parseInt(formObj.results_401k_age2.value))))) + Math.round(future_value(convert_percent(formObj.return_rate.value) / parseInt(formObj.num_paychecks.value), (parseInt(formObj.results_401k_age3.value) - parseInt(formObj.results_401k_age2.value)) * parseInt(formObj.num_paychecks.value), (parseFloat(formObj.contribution.value) + parseFloat(formObj.emp_contribution.value))));
		formObj.results_savings_value3.value = Math.round(Math.pow((((1 - convert_percent(parseFloat(formObj.tax_rate.value))) * convert_percent(parseFloat(formObj.return_rate.value))) + 1), (parseInt(formObj.results_savings_age3.value) - parseInt(formObj.results_savings_age2.value))) * parseFloat(formObj.results_savings_value2.value)) + Math.round(future_value((convert_percent(parseFloat(formObj.return_rate.value)) * (1 - convert_percent(parseFloat(formObj.tax_rate.value)))) / parseInt(formObj.num_paychecks.value), (parseInt(formObj.results_savings_age3.value) - parseInt(formObj.results_savings_age2.value)) * parseInt(formObj.num_paychecks.value), (parseFloat(formObj.contribution.value) + parseFloat(formObj.emp_contribution.value))));
				
		formObj.monthly_income_401k.value = payment(parseInt(formObj.results_401k_value3.value), convert_percent(parseFloat(formObj.return_rate.value)),  ((90 - parseInt(formObj.retirement_age.value)) * 12));	
		formObj.monthly_income_savings.value = payment(parseInt(formObj.results_savings_value3.value), convert_percent(parseFloat(formObj.return_rate.value)),  ((90 - parseInt(formObj.retirement_age.value)) * 12));		
	}
	else {
		formObj.results_401k_age1.value = formObj.investment_age.value;
		formObj.results_savings_age1.value = formObj.investment_age.value;
		formObj.results_401k_value1.value = Math.round(((((date_diff / 365) * convert_percent(parseFloat(formObj.return_rate.value))) + 1) * parseFloat(formObj.current_value.value))) + Math.round(future_value((convert_percent(formObj.return_rate.value) / (365 / parseInt(period_days))), parseInt(compounding_periods), (parseFloat(formObj.contribution.value) + parseFloat(formObj.emp_contribution.value))));
		formObj.results_savings_value1.value = Math.round(((((1 - convert_percent(formObj.tax_rate.value)) * convert_percent(formObj.return_rate.value)) * date_diff / 365) + 1) * parseFloat(formObj.current_value.value)) + Math.round(future_value(((1 - convert_percent(formObj.tax_rate.value)) * convert_percent(formObj.return_rate.value)) / (365 / period_days), compounding_periods, (parseFloat(formObj.contribution.value) + parseFloat(formObj.emp_contribution.value))));

		formObj.results_401k_age2.value = parseInt(formObj.investment_age.value) + 5;
		formObj.results_savings_age2.value = parseInt(formObj.investment_age.value) + 5;
		formObj.results_401k_value2.value = Math.round(parseInt(formObj.results_401k_value1.value) * (Math.pow((1 + convert_percent(formObj.return_rate.value)), (parseInt(formObj.results_401k_age2.value) - parseInt(formObj.results_401k_age1.value))))) + Math.round(future_value(convert_percent(formObj.return_rate.value) / parseInt(formObj.num_paychecks.value), (parseInt(formObj.results_401k_age2.value) - parseInt(formObj.results_401k_age1.value)) * parseInt(formObj.num_paychecks.value), (parseFloat(formObj.contribution.value) + parseFloat(formObj.emp_contribution.value))));
		formObj.results_savings_value2.value = Math.round(Math.pow((((1 - convert_percent(parseFloat(formObj.tax_rate.value))) * convert_percent(parseFloat(formObj.return_rate.value))) + 1), (parseInt(formObj.results_savings_age2.value) - parseInt(formObj.results_savings_age1.value))) * parseFloat(formObj.results_savings_value1.value)) + Math.round(future_value((convert_percent(parseFloat(formObj.return_rate.value)) * (1 - convert_percent(parseFloat(formObj.tax_rate.value)))) / parseInt(formObj.num_paychecks.value), (parseInt(formObj.results_savings_age2.value) - parseInt(formObj.results_savings_age1.value)) * parseInt(formObj.num_paychecks.value), (parseFloat(formObj.contribution.value) + parseFloat(formObj.emp_contribution.value))));

		formObj.results_401k_age3.value = parseInt(formObj.investment_age.value) + 15;
		formObj.results_savings_age3.value = parseInt(formObj.investment_age.value) + 15;
		formObj.results_401k_value3.value = Math.round(parseInt(formObj.results_401k_value2.value) * (Math.pow((1 + convert_percent(formObj.return_rate.value)), (parseInt(formObj.results_401k_age3.value) - parseInt(formObj.results_401k_age2.value))))) + Math.round(future_value(convert_percent(formObj.return_rate.value) / parseInt(formObj.num_paychecks.value), (parseInt(formObj.results_401k_age3.value) - parseInt(formObj.results_401k_age2.value)) * parseInt(formObj.num_paychecks.value), (parseFloat(formObj.contribution.value) + parseFloat(formObj.emp_contribution.value))));
		formObj.results_savings_value3.value = Math.round(Math.pow((((1 - convert_percent(parseFloat(formObj.tax_rate.value))) * convert_percent(parseFloat(formObj.return_rate.value))) + 1), (parseInt(formObj.results_savings_age3.value) - parseInt(formObj.results_savings_age2.value))) * parseFloat(formObj.results_savings_value2.value)) + Math.round(future_value((convert_percent(parseFloat(formObj.return_rate.value)) * (1 - convert_percent(parseFloat(formObj.tax_rate.value)))) / parseInt(formObj.num_paychecks.value), (parseInt(formObj.results_savings_age3.value) - parseInt(formObj.results_savings_age2.value)) * parseInt(formObj.num_paychecks.value), (parseFloat(formObj.contribution.value) + parseFloat(formObj.emp_contribution.value))));

		formObj.results_401k_age4.value = formObj.retirement_age.value;
		formObj.results_savings_age4.value = formObj.retirement_age.value;
		formObj.results_401k_value4.value = Math.round(parseInt(formObj.results_401k_value3.value) * (Math.pow((1 + convert_percent(formObj.return_rate.value)), (parseInt(formObj.results_401k_age4.value) - parseInt(formObj.results_401k_age3.value))))) + Math.round(future_value(convert_percent(formObj.return_rate.value) / parseInt(formObj.num_paychecks.value), (parseInt(formObj.results_401k_age4.value) - parseInt(formObj.results_401k_age3.value)) * parseInt(formObj.num_paychecks.value), (parseFloat(formObj.contribution.value) + parseFloat(formObj.emp_contribution.value))));
		formObj.results_savings_value4.value = Math.round(Math.pow((((1 - convert_percent(parseFloat(formObj.tax_rate.value))) * convert_percent(parseFloat(formObj.return_rate.value))) + 1), (parseInt(formObj.results_savings_age4.value) - parseInt(formObj.results_savings_age3.value))) * parseFloat(formObj.results_savings_value3.value)) + Math.round(future_value((convert_percent(parseFloat(formObj.return_rate.value)) * (1 - convert_percent(parseFloat(formObj.tax_rate.value)))) / parseInt(formObj.num_paychecks.value), (parseInt(formObj.results_savings_age4.value) - parseInt(formObj.results_savings_age3.value)) * parseInt(formObj.num_paychecks.value), (parseFloat(formObj.contribution.value) + parseFloat(formObj.emp_contribution.value))));
	
		formObj.monthly_income_401k.value = payment(parseInt(formObj.results_401k_value4.value), convert_percent(parseFloat(formObj.return_rate.value)), ((90 - parseInt(formObj.retirement_age.value)) * 12));
		formObj.monthly_income_savings.value = payment(parseInt(formObj.results_savings_value4.value), convert_percent(parseFloat(formObj.return_rate.value)), ((90 - parseInt(formObj.retirement_age.value)) * 12));
	}
}

function reset_results(formObj) {
	formObj.results_401k_age1.value = "";
	formObj.results_401k_age2.value = "";
	formObj.results_401k_age3.value = "";
	formObj.results_401k_age4.value = "";
	formObj.results_401k_value1.value = "";
	formObj.results_401k_value2.value = "";
	formObj.results_401k_value3.value = "";
	formObj.results_401k_value4.value = "";
	formObj.results_savings_age1.value = "";
	formObj.results_savings_age2.value = "";
	formObj.results_savings_age3.value = "";
	formObj.results_savings_age4.value = "";
	formObj.results_savings_value1.value = "";
	formObj.results_savings_value2.value = "";
	formObj.results_savings_value3.value = "";
	formObj.results_savings_value4.value = "";
	formObj.monthly_income_401k.value = "";
	formObj.monthly_income_savings.value = "";
}

function future_value(int_rate, per_term, payment) {
	return (((Math.pow((1 + int_rate), per_term) - 1) / int_rate) * payment);
}

function convert_percent(num) {
	//converts num to decimal
	return (parseFloat(num) * 0.01);
}

function payment(principal, interest, months) {
	return Math.round(((principal * interest)/ 12) / (1 - (Math.pow(1 / ((interest / 12) + 1), months))));
}