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//
// ooo-util - a place for OOO utilities
// Copyright (C) 2011 Three Rings Design, Inc., All Rights Reserved
// http://github.com/threerings/ooo-util/blob/master/LICENSE

package com.threerings.util;

import com.google.common.base.Function;
import com.google.common.collect.ImmutableMultiset;
import com.google.common.collect.Multiset;
import com.google.common.collect.Ordering;
import com.google.common.primitives.Ints;

/**
 * Convenience functions for working with Multisets.
 */
public class MultisetUtil
{
    /** An Ordering that compares Multiset.Entrys by count. */
    public static final Ordering> ENTRY_COUNT_ORDERING =
        new Ordering>() {
            public int compare (Multiset.Entry left, Multiset.Entry right) {
                return Ints.compare(left.getCount(), right.getCount());
            }
        };

    /**
     * Return a Function that will transform objects to their corresponding count in the
     * specified Multiset.
     */
    public static Function countFunction (final Multiset set)
    {
        return new Function() {
            public Integer apply (Object o) {
                return set.count(o);
            }
        };
    }

    /**
     * Create an ImmutableMultiset with a single element with the specified count.
     */
    public static  ImmutableMultiset singleton (T element, int count)
    {
        return ImmutableMultiset.builder()
            .addCopies(element, count)
            .build();
    }
}