Apex Plug-In that calculates monthly payment (for Force.com Cloud Flow Designer Workbook)

MortgageCalculator.txt

global class MortgageCalculator implements Process.Plugin
{
    global Process.PluginResult invoke(Process.PluginRequest request)
    {
        Double amount = (Double)request.inputParameters.get('Amount');
        Double term = (Double)request.inputParameters.get('Term');
        // in addition to to adding the calculation below, to use this in the Visual Workflow Workbook, tutorial #3,
        // a third input called "Rate" will need to be defined for the calculate quote step: the screen input field "Interest_Rate".
        Double rate = (Double)request.inputParameters.get('Rate');
        Double monthlyrate = rate/(12*100);
        Double cMonthlyPayment = amount * (monthlyrate/(1 - Math.pow(1 + monthlyrate, -term)));
        Map<String, Object> result = new Map<String, Object>();
        result.put('MonthlyPayment', cMonthlyPayment);
        return new Process.PluginResult(result);
    }
    global Process.PluginDescribeResult describe()
    {
        Process.PluginDescribeResult result = new Process.PluginDescribeResult();
        result.description='This plug-in generates a monthly payment quote given the term and amount.';
        result.tag='Mortgage Quote';
        result.inputParameters = new List<Process.PluginDescribeResult.InputParameter> {
            new Process.PluginDescribeResult.InputParameter('Amount',
                Process.PluginDescribeResult.ParameterType.DOUBLE, true),
            new Process.PluginDescribeResult.InputParameter('Term',
                Process.PluginDescribeResult.ParameterType.DOUBLE, true),
            new Process.PluginDescribeResult.InputParameter('Rate',
                Process.PluginDescribeResult.ParameterType.DOUBLE, true)
        };
        result.outputParameters = new List<Process.PluginDescribeResult.OutputParameter> {
            new Process.PluginDescribeResult.OutputParameter('MonthlyPayment',
                Process.PluginDescribeResult.ParameterType.DOUBLE)
        };
        return result;
    }
}