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/*
 * Copyright 2003-2010 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.codehaus.groovy.runtime;

import groovy.lang.GroovyRuntimeException;
import org.codehaus.groovy.runtime.typehandling.DefaultTypeTransformation;

import java.util.Comparator;

/**
 * Compares two objects using Groovy's friendly comparison algorithm, i.e.
 * handles nulls gracefully (nul being less than everything else) and
 * performs numeric type coercion if required.
 */
public class NumberAwareComparator implements Comparator {
    public int compare(T o1, T o2) {
        try {
            return DefaultTypeTransformation.compareTo(o1, o2);
        } catch (ClassCastException cce) {
            /* ignore */
        } catch (GroovyRuntimeException gre) {
            /* ignore */
        }
        // since the object does not have a valid compareTo method
        // we compare using the hashcodes. null cases are handled by
        // DefaultTypeTransformation.compareTo
        // This is not exactly a mathematical valid approach, since we compare object
        // that cannot be compared. To avoid strange side effects we do a pseudo order
        // using hashcodes, but without equality. Since then an x and y with the same
        // hashcodes will behave different depending on if we compare x with y or
        // x with y, the result might be unstable as well. Setting x and y to equal
        // may mean the removal of x or y in a sorting operation, which we don't want.
        int x1 = o1.hashCode();
        int x2 = o2.hashCode();
        if (x1 > x2) return 1;
        return -1;
    }
}