cassandra-trunk/src/java/org/apache/cassandra/dht/Bounds.java
/*
 * 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.dht;

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

import com.google.common.collect.Iterators;
import com.google.common.collect.Lists;
import com.google.common.collect.PeekingIterator;
import com.google.common.collect.Sets;

import org.apache.cassandra.db.PartitionPosition;
import org.apache.cassandra.utils.Pair;

/**
 * AbstractBounds containing both its endpoints: [left, right].  Used by "classic" by-key range scans.
 */
public class Bounds<T extends RingPosition<T>> extends AbstractBounds<T>
{
    public Bounds(T left, T right)
    {
        super(left, right);
        // unlike a Range, a Bounds may not wrap
        assert !strictlyWrapsAround(left, right) : "[" + left + "," + right + "]";
    }

    public boolean contains(T position)
    {
        // Range.contains doesnt work correctly if left == right (unless both
        // are minimum) because for Range that means a wrapping range that select
        // the whole ring. So we must explicitely handle this case
        return left.equals(position) || ((right.isMinimum() || !left.equals(right)) && Range.contains(left, right, position));
    }

    public Pair<AbstractBounds<T>, AbstractBounds<T>> split(T position)
    {
        assert contains(position);
        // Check if the split would have no effect on the range
        if (position.equals(right))
            return null;

        AbstractBounds<T> lb = new Bounds<T>(left, position);
        AbstractBounds<T> rb = new Range<T>(position, right);
        return Pair.create(lb, rb);
    }

    public boolean inclusiveLeft()
    {
        return true;
    }

    public boolean inclusiveRight()
    {
        return true;
    }

    public boolean intersects(Bounds<T> that)
    {
        // We either contains one of the that bounds, or we are fully contained into that.
        return contains(that.left) || contains(that.right) || that.contains(left);
    }

    public List<? extends AbstractBounds<T>> unwrap()
    {
        // Bounds objects never wrap
        return Collections.<AbstractBounds<T>>singletonList(this);
    }

    @Override
    public boolean equals(Object o)
    {
        if (!(o instanceof Bounds))
            return false;
        Bounds<?> rhs = (Bounds<?>)o;
        return left.equals(rhs.left) && right.equals(rhs.right);
    }

    @Override
    public String toString()
    {
        return "[" + left + "," + right + "]";
    }

    protected String getOpeningString()
    {
        return "[";
    }

    protected String getClosingString()
    {
        return "]";
    }

    public static <T extends RingPosition<T>> boolean isInBounds(T token, Iterable<Bounds<T>> bounds)
    {
        assert bounds != null;

        for (Bounds<T> bound : bounds)
        {
            if (bound.contains(token))
            {
                return true;
            }
        }
        return false;
    }

    public boolean isStartInclusive()
    {
        return true;
    }

    public boolean isEndInclusive()
    {
        return true;
    }

    /**
     * Compute a bounds of keys corresponding to a given bounds of token.
     */
    public static Bounds<PartitionPosition> makeRowBounds(Token left, Token right)
    {
        return new Bounds<PartitionPosition>(left.minKeyBound(), right.maxKeyBound());
    }

    public AbstractBounds<T> withNewRight(T newRight)
    {
        return new Bounds<T>(left, newRight);
    }

    /**
     * Retrieves non-overlapping bounds for the list of input bounds
     *
     * Assume we have the following bounds
     * (brackets representing left/right bound):
     * [   ] [   ]    [   ]   [  ]
     * [   ]         [       ]
     * This method will return the following bounds:
     * [         ]    [          ]
     *
     * @param bounds unsorted bounds to find overlaps
     * @return the non-overlapping bounds
     */
    public static <T extends RingPosition<T>> Set<Bounds<T>> getNonOverlappingBounds(Iterable<Bounds<T>> bounds)
    {
        ArrayList<Bounds<T>> sortedBounds = Lists.newArrayList(bounds);
        Collections.sort(sortedBounds, new Comparator<Bounds<T>>()
        {
            public int compare(Bounds<T> o1, Bounds<T> o2)
            {
                return o1.left.compareTo(o2.left);
            }
        });

        Set<Bounds<T>> nonOverlappingBounds = Sets.newHashSet();

        PeekingIterator<Bounds<T>> it = Iterators.peekingIterator(sortedBounds.iterator());
        while (it.hasNext())
        {
            Bounds<T> beginBound = it.next();
            Bounds<T> endBound = beginBound;
            while (it.hasNext() && endBound.right.compareTo(it.peek().left) >= 0)
                endBound = it.next();
            nonOverlappingBounds.add(new Bounds<>(beginBound.left, endBound.right));
        }

        return nonOverlappingBounds;
    }
}
