/*******************************************************************************
 *
 * Copyright (c) 2004-2010 Oracle Corporation.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *
 *
 *******************************************************************************/ 

package hudson.model.queue;

import hudson.model.Queue.BuildableItem;

import java.util.Collections;
import java.util.Comparator;
import java.util.List;

/**
 * Partial implementation of {@link QueueSorter} in terms of {@link Comparator}.
 *
 * @author Kohsuke Kawaguchi
 * @since 1.343
 */
public abstract class AbstractQueueSorterImpl extends QueueSorter implements Comparator<BuildableItem> {

    @Override
    public void sortBuildableItems(List<BuildableItem> buildables) {
        Collections.sort(buildables, this); // sort is ascending order
    }

    /**
     * Override this method to provide the ordering of the sort.
     *
     * <p> if lhs should be build before rhs, return a negative value. Or put
     * another way, think of the comparison as a process of converting a
     * {@link BuildableItem} into a number, then doing num(lhs)-num(rhs).
     *
     * <p> The default implementation does FIFO.
     */
    public int compare(BuildableItem lhs, BuildableItem rhs) {
        return compare(lhs.buildableStartMilliseconds, rhs.buildableStartMilliseconds);
    }

    /**
     * sign(a-b).
     */
    protected static int compare(long a, long b) {
        if (a > b) {
            return 1;
        }
        if (a < b) {
            return -1;
        }
        return 0;
    }

    /**
     * sign(a-b).
     */
    protected static int compare(int a, int b) {
        if (a > b) {
            return 1;
        }
        if (a < b) {
            return -1;
        }
        return 0;
    }
}