package net.sf.jasperreports.engine.fill;

class JRDoubleAverageIncrementer extends JRAbstractExtendedIncrementer {
  private static JRDoubleAverageIncrementer mainInstance = new JRDoubleAverageIncrementer();
  
  public static JRDoubleAverageIncrementer getInstance() {
    return mainInstance;
  }
  
  public Object increment(JRCalculable variable, Object expressionValue, AbstractValueProvider valueProvider) {
    if (expressionValue == null) {
      if (variable.isInitialized())
        return null; 
      return variable.getValue();
    } 
    Number countValue = (Number)valueProvider.getValue(variable.getHelperVariable((byte)0));
    Number sumValue = (Number)valueProvider.getValue(variable.getHelperVariable((byte)1));
    return new Double(sumValue.doubleValue() / countValue.doubleValue());
  }
  
  public Object initialValue() {
    return JRDoubleIncrementerFactory.ZERO;
  }
}