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package org.gvsig.legend.aggregate.lib.impl.operation;

import java.text.MessageFormat;

import org.apache.commons.lang3.StringUtils;

import org.gvsig.fmap.dal.feature.Feature;

import org.gvsig.legend.aggregate.lib.api.AbstractOperation;

public class AvgOperation extends AbstractOperation {

    private double avg = 0;

    private int count = 0;

    public AvgOperation() {

        super(

            "_Average", 

            "_Calculate_the_average_of_the_selected_attribute_for_the_grouped_features"

        );

    }

    @Override

    public boolean isAttributeRequiered() {

        return true;

    }

    @Override

    public boolean isAditionalValueRequiered() {

        return true;

    }

    @Override

    public void reset() {

        avg = 0;

        count = 0;

    }

    @Override

    public void perform(Feature feature) {

            try {

                double value = feature.getDouble(this.getAttributeName());

                avg = ( avg * count + value ) / (count+1);

                count++;

            } catch(Exception ex) {

            }

    }

    @Override

    public Object getValue() {

        return this.avg;

    }

    @Override

    public String format() {

        if( StringUtils.isEmpty(this.getAditionalValue()) ) {

            return super.format(); 

        }

        try {

            return MessageFormat.format("{0,number,"+this.getAditionalValue()+"}", this.getValue());

        } catch(Exception ex) {

            return super.format(); 

        }

    }

}