/*
 * JBoss, Home of Professional Open Source.
 * See the COPYRIGHT.txt file distributed with this work for information
 * regarding copyright ownership.  Some portions may be licensed
 * to Red Hat, Inc. under one or more contributor license agreements.
 * 
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * 
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301 USA.
 */

package org.teiid.core.util;

import java.util.Arrays;

/**
 * Utilities to test the equivalence (see method-specific definitions) of any
 * two object/array references.
 */
public class EquivalenceUtil {
    
    /**
     * Cannot be instantiated
     */
    protected EquivalenceUtil() {
    }
    
    /**
     * Tests whether two object references refer to equal objects. The object
     * references can both be null, in which case they are also considered equal.
     * @param obj1 object reference
     * @param obj2 object reference
     * @return true if both references are null, OR if neither is null and both
     * objects are equal; false otherwise
     */
    public static boolean areEqual(Object obj1, Object obj2) {
        if (obj1 == obj2) {
            return true;
        } else if (obj1 == null || obj2 == null) {
            return false;
        } else {
            return obj1.equals(obj2);
        }
    }
    
    /**
     * Tests whether two arrays are equivalent. This method ignores the array
     * types, but checks the number of references in each array, and the
     * equivalence of those references (in ascending index order).
     * @param array1 an object array
     * @param array2 an object array
     */
    public static boolean areEquivalent(Object[] array1, Object[] array2) {
        return Arrays.equals(array1, array2);
    }
    
    /**
     * Tests whether two objects references are equivalent but not the same object.
     * If both references are the same, this method will return false;
     * @param obj1 object reference
     * @param obj2 object reference
     * @return true if the two references are unequal, and the objects they
     * refer to are equal
     */
    public static boolean areStrictlyEquivalent(Object obj1, Object obj2) {
        if (obj1 == obj2 || obj1 == null || obj2 == null) {
            return false;
        }
        return areEqual(obj1, obj2);
    }
    
    /**
     * Tests whether the array references are equivalent, but are not the same.
     * This method checks for the strict equivalence of each pair of objects
     * in the two arrays (i.e. corresponding objects cannot be the same but must
     * be equivalent) in ascending index order. This method also considers a
     * null array and a 0-length array equivalent, and ignores the array type.
     * @param array1 an object array
     * @param array2 an object array
     * @return true if the arrays are equivalent, but not the same.
     */
    public static boolean areStrictlyEquivalent(Object[] array1, Object[] array2) {
        if (array1 == array2) {
            return false;
        } else if (array1 == null) {
            return array2.length == 0;
        } else if (array2 == null) {
            return array1.length == 0;
        } else if (array1.length != array2.length) {
             return false;
        } else {
            for (int i = 0; i < array1.length; i++) {
                if (!areStrictlyEquivalent(array1[i], array2[i])) {
                    return false;
                }
            }
        }
        return true;
    }
}
