/**
    *
    * 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.hadoop.hbase.regionserver;
  
  import com.google.common.annotations.VisibleForTesting;
  
  import java.util.Collection;
  import java.util.Comparator;
  import java.util.Iterator;
  import java.util.NavigableSet;
  import java.util.SortedSet;
  import java.util.concurrent.ConcurrentNavigableMap;
  import java.util.concurrent.ConcurrentSkipListMap;
  
  import org.apache.hadoop.hbase.Cell;
  import org.apache.hadoop.hbase.KeyValue;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  
  /**
   * A {@link java.util.Set} of {@link Cell}s implemented on top of a
   * {@link java.util.concurrent.ConcurrentSkipListMap}.  Works like a
   * {@link java.util.concurrent.ConcurrentSkipListSet} in all but one regard:
   * An add will overwrite if already an entry for the added key.  In other words,
   * where CSLS does "Adds the specified element to this set if it is not already
   * present.", this implementation "Adds the specified element to this set EVEN
   * if it is already present overwriting what was there previous".  The call to
   * add returns true if no value in the backing map or false if there was an
   * entry with same key (though value may be different).
   * <p>Otherwise,
   * has same attributes as ConcurrentSkipListSet: e.g. tolerant of concurrent
   * get and set and won't throw ConcurrentModificationException when iterating.
   */
  @InterfaceAudience.Private
  public class CellSkipListSet implements NavigableSet<Cell> {
    private final ConcurrentNavigableMap<Cell, Cell> delegatee;
  
    CellSkipListSet(final KeyValue.KVComparator c) {
      this.delegatee = new ConcurrentSkipListMap<Cell, Cell>(c);
    }
  
    CellSkipListSet(final ConcurrentNavigableMap<Cell, Cell> m) {
      this.delegatee = m;
    }
  
    public Cell ceiling(Cell e) {
      throw new UnsupportedOperationException("Not implemented");
    }
  
    public Iterator<Cell> descendingIterator() {
      return this.delegatee.descendingMap().values().iterator();
    }
  
    public NavigableSet<Cell> descendingSet() {
      throw new UnsupportedOperationException("Not implemented");
    }
  
    public Cell floor(Cell e) {
      throw new UnsupportedOperationException("Not implemented");
    }
  
    public SortedSet<Cell> headSet(final Cell toElement) {
      return headSet(toElement, false);
    }
  
    public NavigableSet<Cell> headSet(final Cell toElement,
        boolean inclusive) {
      return new CellSkipListSet(this.delegatee.headMap(toElement, inclusive));
    }
  
    public Cell higher(Cell e) {
      throw new UnsupportedOperationException("Not implemented");
    }
  
    public Iterator<Cell> iterator() {
      return this.delegatee.values().iterator();
    }
  
    public Cell lower(Cell e) {
      throw new UnsupportedOperationException("Not implemented");
    }
  
    public Cell pollFirst() {
      throw new UnsupportedOperationException("Not implemented");
   }
 
   public Cell pollLast() {
     throw new UnsupportedOperationException("Not implemented");
   }
 
   public SortedSet<Cell> subSet(Cell fromElement, Cell toElement) {
     throw new UnsupportedOperationException("Not implemented");
   }
 
   public NavigableSet<Cell> subSet(Cell fromElement,
       boolean fromInclusive, Cell toElement, boolean toInclusive) {
     throw new UnsupportedOperationException("Not implemented");
   }
 
   public SortedSet<Cell> tailSet(Cell fromElement) {
     return tailSet(fromElement, true);
   }
 
   public NavigableSet<Cell> tailSet(Cell fromElement, boolean inclusive) {
     return new CellSkipListSet(this.delegatee.tailMap(fromElement, inclusive));
   }
 
   public Comparator<? super Cell> comparator() {
     throw new UnsupportedOperationException("Not implemented");
   }
 
   public Cell first() {
     return this.delegatee.get(this.delegatee.firstKey());
   }
 
   public Cell last() {
     return this.delegatee.get(this.delegatee.lastKey());
   }
 
   public boolean add(Cell e) {
     return this.delegatee.put(e, e) == null;
   }
 
   public boolean addAll(Collection<? extends Cell> c) {
     throw new UnsupportedOperationException("Not implemented");
   }
 
   public void clear() {
     this.delegatee.clear();
   }
 
   public boolean contains(Object o) {
     //noinspection SuspiciousMethodCalls
     return this.delegatee.containsKey(o);
   }
 
   public boolean containsAll(Collection<?> c) {
     throw new UnsupportedOperationException("Not implemented");
   }
 
   public boolean isEmpty() {
     return this.delegatee.isEmpty();
   }
 
   public boolean remove(Object o) {
     return this.delegatee.remove(o) != null;
   }
 
   public boolean removeAll(Collection<?> c) {
     throw new UnsupportedOperationException("Not implemented");
   }
 
   public boolean retainAll(Collection<?> c) {
     throw new UnsupportedOperationException("Not implemented");
   }
 
   public Cell get(Cell kv) {
     return this.delegatee.get(kv);
   }
 
   public int size() {
     if (delegatee instanceof ConcurrentSkipListMap) {
       throw new UnsupportedOperationException("ConcurrentSkipListMap.size() is time-consuming");
     }
     return this.delegatee.size();
   }
 
   public Object[] toArray() {
     throw new UnsupportedOperationException("Not implemented");
   }
 
   public <T> T[] toArray(T[] a) {
     throw new UnsupportedOperationException("Not implemented");
   }
 
   @VisibleForTesting
   int sizeForTests() {
     return this.delegatee.size();
   }
 }