package or.apache.commons.collections.comparators;

import java.util.Comparator;

/**
 * Decorates another Comparator with transformation behavior. That is, the
 * return value from the transform operation will be passed to the decorated
 * <CODE>Comparator#compare</CODE> method.
 * <p>
 * @see org.apache.commons.collections.Transformer
 * @see org.apache.commons.collections.comparators.ComparableComparator
 */
public class TransformingComparator implements Comparator
{
    protected Comparator decorated;
    protected Transformer transformer;

    /**
     * Constructs an instance with the given Transformer and a ComparableComparator.
     * @param transformer what will transform the instance.
     */
    public TransformingComparator(Transformer transformer)
    {
        this(transformer, new ComparableComparator());
    }

    /**
     * Constructs an instance with the given Transformer and Comparator
     * @param decorated  the decorated Comparator
     * @param getterName    the getter name
     */
    public TransformingComparator(Transformer transformer, Comparator decorated)
    {
        this.decorated = decorated;
        this.transformer = transformer;
    }

    /**
     * Returns the result of comparing the values from the transform operation.
     * @return the result of comparing the values from the transform operation
     */
    public int compare(Object o1, Object o2)
    {
        Object value1 = this.transformer.transform(o1);
        Object value2 = this.transformer.transform(o2);
        return this.decorated.compare(value1, value2);
    }

}