/*
 * Copyright 2015, The Querydsl Team (http://www.querydsl.com/team)
 *
 * 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 com.querydsl.collections;

import java.io.Serializable;
import java.util.Comparator;

import com.mysema.codegen.Evaluator;
import com.querydsl.core.util.NullSafeComparableComparator;

/**
 * {@code MultiComparator} compares arrays
 *
 * @param <T> element type
 *
 * @author tiwe
 */
public class MultiComparator<T> implements Comparator<T>, Serializable {

    @SuppressWarnings("unchecked")
    private static final Comparator<Object> naturalOrder = new NullSafeComparableComparator();

    private static final long serialVersionUID = 1121416260773566299L;

    private final boolean[] asc;

    private final transient Evaluator<Object[]> ev;

    public MultiComparator(Evaluator<Object[]> ev, boolean[] directions) {
        this.ev = ev;
        this.asc = directions.clone();
    }

    @Override
    public int compare(T o1, T o2) {
        if (o1.getClass().isArray()) {
            return innerCompare(ev.evaluate((Object[]) o1), ev.evaluate((Object[]) o2));
        } else {
            return innerCompare(ev.evaluate(o1), ev.evaluate(o2));
        }
    }

    private int innerCompare(Object[] o1, Object[] o2) {
        for (int i = 0; i < o1.length; i++) {
            int res;
            if (o1[i] == null) {
                res = o2[i] == null ? 0 : -1;
            } else if (o2[i] == null) {
                res = 1;
            } else {
                res = naturalOrder.compare(o1[i], o2[i]);
            }
            if (res != 0) {
                return asc[i] ? res : -res;
            }
        }
        return 0;
    }

}