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GraphHopper is a fast and memory efficient Java road routing engine working seamlessly with OpenStreetMap data.
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/*
 *  Licensed to GraphHopper and Peter Karich under one or more contributor
 *  license agreements. See the NOTICE file distributed with this work for 
 *  additional information regarding copyright ownership.
 * 
 *  GraphHopper licenses this file to you 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.graphhopper.coll;

import gnu.trove.iterator.TIntIterator;
import gnu.trove.set.hash.TIntHashSet;

import java.util.Map.Entry;
import java.util.TreeMap;

/**
 * A priority queue implemented by a treemap to allow fast key update. Or should we use a standard
 * b-tree?
 * 
 * @author Peter Karich
 */
public class GHSortedCollection
{
    private int size;
    private int slidingMeanValue = 20;
    private TreeMap map;

    public GHSortedCollection()
    {
        this(0);
    }

    public GHSortedCollection( int size )
    {
        // use size as indicator for maxEntries => try radix sort?
        map = new TreeMap();
    }

    public void clear()
    {
        size = 0;
        map.clear();
    }

    void remove( int key, int value )
    {
        TIntHashSet set = map.get(value);
        if (set == null || !set.remove(key))
        {
            throw new IllegalStateException("cannot remove key " + key + " with value " + value
                    + " - did you insert " + key + "," + value + " before?");
        }
        size--;
        if (set.isEmpty())
        {
            map.remove(value);
        }
    }

    public void update( int key, int oldValue, int value )
    {
        remove(key, oldValue);
        insert(key, value);
    }

    public void insert( int key, int value )
    {
        TIntHashSet set = map.get(value);
        if (set == null)
        {
            map.put(value, set = new TIntHashSet(slidingMeanValue));
        }
//        else
//            slidingMeanValue = Math.max(5, (slidingMeanValue + set.size()) / 2);
        if (!set.add(key))
        {
            throw new IllegalStateException("use update if you want to update " + key);
        }
        size++;
    }

    public int peekValue()
    {
        if (size == 0)
        {
            throw new IllegalStateException("collection is already empty!?");
        }
        Entry e = map.firstEntry();
        if (e.getValue().isEmpty())
        {
            throw new IllegalStateException("internal set is already empty!?");
        }
        return map.firstEntry().getKey();
    }

    public int peekKey()
    {
        if (size == 0)
        {
            throw new IllegalStateException("collection is already empty!?");
        }
        TIntHashSet set = map.firstEntry().getValue();
        if (set.isEmpty())
        {
            throw new IllegalStateException("internal set is already empty!?");
        }
        return set.iterator().next();
    }

    /**
     * @return removes the smallest entry (key and value) from this collection
     */
    public int pollKey()
    {
        size--;
        if (size < 0)
        {
            throw new IllegalStateException("collection is already empty!?");
        }
        Entry e = map.firstEntry();
        TIntHashSet set = e.getValue();
        TIntIterator iter = set.iterator();
        if (set.isEmpty())
        {
            throw new IllegalStateException("internal set is already empty!?");
        }
        int val = iter.next();
        iter.remove();
        if (set.isEmpty())
        {
            map.remove(e.getKey());
        }
        return val;
    }

    public int getSize()
    {
        return size;
    }

    public boolean isEmpty()
    {
        return size == 0;
    }

    public int getSlidingMeanValue()
    {
        return slidingMeanValue;
    }

    @Override
    public String toString()
    {
        int min = Integer.MAX_VALUE;
        int max = Integer.MIN_VALUE;
        for (Entry e : map.entrySet())
        {
            int tmpSize = e.getValue().size();
            if (min > tmpSize)
            {
                min = tmpSize;
            }
            if (max < tmpSize)
            {
                max = tmpSize;
            }
        }
        String str = "";
        if (!isEmpty())
        {
            str = ", minEntry=(" + peekKey() + "=>" + peekValue() + ")";
        }
        return "size=" + size + ", treeMap.size=" + map.size()
                + ", averageNo=" + size * 1f / map.size()
                + ", minNo=" + min + ", maxNo=" + max + str;
    }
}