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The Apache Cassandra Project develops a highly scalable second-generation distributed database, bringing together Dynamo's fully distributed design and Bigtable's ColumnFamily-based data model.
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/*
 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF 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 org.apache.cassandra.locator;

import com.google.common.collect.Iterators;
import org.apache.cassandra.dht.Range;
import org.apache.cassandra.dht.Token;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.net.InetAddress;
import java.util.*;

public class PendingRangeMaps implements Iterable, List>>
{
    private static final Logger logger = LoggerFactory.getLogger(PendingRangeMaps.class);

    /**
     * We have for NavigableMap to be able to search for ranges containing a token efficiently.
     *
     * First two are for non-wrap-around ranges, and the last two are for wrap-around ranges.
     */
    // ascendingMap will sort the ranges by the ascending order of right token
    final NavigableMap, List> ascendingMap;
    /**
     * sorting end ascending, if ends are same, sorting begin descending, so that token (end, end) will
     * come before (begin, end] with the same end, and (begin, end) will be selected in the tailMap.
     */
    static final Comparator> ascendingComparator = new Comparator>()
        {
            @Override
            public int compare(Range o1, Range o2)
            {
                int res = o1.right.compareTo(o2.right);
                if (res != 0)
                    return res;

                return o2.left.compareTo(o1.left);
            }
        };

    // ascendingMap will sort the ranges by the descending order of left token
    final NavigableMap, List> descendingMap;
    /**
     * sorting begin descending, if begins are same, sorting end descending, so that token (begin, begin) will
     * come after (begin, end] with the same begin, and (begin, end) won't be selected in the tailMap.
     */
    static final Comparator> descendingComparator = new Comparator>()
        {
            @Override
            public int compare(Range o1, Range o2)
            {
                int res = o2.left.compareTo(o1.left);
                if (res != 0)
                    return res;

                // if left tokens are same, sort by the descending of the right tokens.
                return o2.right.compareTo(o1.right);
            }
        };

    // these two maps are for warp around ranges.
    final NavigableMap, List> ascendingMapForWrapAround;
    /**
     * for wrap around range (begin, end], which begin > end.
     * Sorting end ascending, if ends are same, sorting begin ascending,
     * so that token (end, end) will come before (begin, end] with the same end, and (begin, end] will be selected in
     * the tailMap.
     */
    static final Comparator> ascendingComparatorForWrapAround = new Comparator>()
    {
        @Override
        public int compare(Range o1, Range o2)
        {
            int res = o1.right.compareTo(o2.right);
            if (res != 0)
                return res;

            return o1.left.compareTo(o2.left);
        }
    };

    final NavigableMap, List> descendingMapForWrapAround;
    /**
     * for wrap around ranges, which begin > end.
     * Sorting end ascending, so that token (begin, begin) will come after (begin, end] with the same begin,
     * and (begin, end) won't be selected in the tailMap.
     */
    static final Comparator> descendingComparatorForWrapAround = new Comparator>()
    {
        @Override
        public int compare(Range o1, Range o2)
        {
            int res = o2.left.compareTo(o1.left);
            if (res != 0)
                return res;
            return o1.right.compareTo(o2.right);
        }
    };

    public PendingRangeMaps()
    {
        this.ascendingMap = new TreeMap, List>(ascendingComparator);
        this.descendingMap = new TreeMap, List>(descendingComparator);
        this.ascendingMapForWrapAround = new TreeMap, List>(ascendingComparatorForWrapAround);
        this.descendingMapForWrapAround = new TreeMap, List>(descendingComparatorForWrapAround);
    }

    static final void addToMap(Range range,
                               InetAddress address,
                               NavigableMap, List> ascendingMap,
                               NavigableMap, List> descendingMap)
    {
        List addresses = ascendingMap.get(range);
        if (addresses == null)
        {
            addresses = new ArrayList(1);
            ascendingMap.put(range, addresses);
            descendingMap.put(range, addresses);
        }
        addresses.add(address);
    }

    public void addPendingRange(Range range, InetAddress address)
    {
        if (Range.isWrapAround(range.left, range.right))
        {
            addToMap(range, address, ascendingMapForWrapAround, descendingMapForWrapAround);
        }
        else
        {
            addToMap(range, address, ascendingMap, descendingMap);
        }
    }

    static final void addIntersections(Set endpointsToAdd,
                                       NavigableMap, List> smallerMap,
                                       NavigableMap, List> biggerMap)
    {
        // find the intersection of two sets
        for (Range range : smallerMap.keySet())
        {
            List addresses = biggerMap.get(range);
            if (addresses != null)
            {
                endpointsToAdd.addAll(addresses);
            }
        }
    }

    public Collection pendingEndpointsFor(Token token)
    {
        Set endpoints = new HashSet<>();

        Range searchRange = new Range(token, token);

        // search for non-wrap-around maps
        NavigableMap, List> ascendingTailMap = ascendingMap.tailMap(searchRange, true);
        NavigableMap, List> descendingTailMap = descendingMap.tailMap(searchRange, false);

        // add intersections of two maps
        if (ascendingTailMap.size() < descendingTailMap.size())
        {
            addIntersections(endpoints, ascendingTailMap, descendingTailMap);
        }
        else
        {
            addIntersections(endpoints, descendingTailMap, ascendingTailMap);
        }

        // search for wrap-around sets
        ascendingTailMap = ascendingMapForWrapAround.tailMap(searchRange, true);
        descendingTailMap = descendingMapForWrapAround.tailMap(searchRange, false);

        // add them since they are all necessary.
        for (Map.Entry, List> entry : ascendingTailMap.entrySet())
        {
            endpoints.addAll(entry.getValue());
        }
        for (Map.Entry, List> entry : descendingTailMap.entrySet())
        {
            endpoints.addAll(entry.getValue());
        }

        return endpoints;
    }

    public String printPendingRanges()
    {
        StringBuilder sb = new StringBuilder();

        for (Map.Entry, List> entry : this)
        {
            Range range = entry.getKey();

            for (InetAddress address : entry.getValue())
            {
                sb.append(address).append(':').append(range);
                sb.append(System.getProperty("line.separator"));
            }
        }

        return sb.toString();
    }

    @Override
    public Iterator, List>> iterator()
    {
        return Iterators.concat(ascendingMap.entrySet().iterator(), ascendingMapForWrapAround.entrySet().iterator());
    }
}