/*
    *
    * 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.util;
  
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.Iterator;
  import java.util.List;
  import java.util.SortedSet;
  
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.Cell;
  import org.apache.hadoop.hbase.KeyValue;
  import org.apache.hadoop.hbase.regionserver.NonReversedNonLazyKeyValueScanner;
  
  /**
   * Utility scanner that wraps a sortable collection and serves
   * as a KeyValueScanner.
   */
  @InterfaceAudience.Private
  public class CollectionBackedScanner extends NonReversedNonLazyKeyValueScanner {
    final private Iterable<Cell> data;
    final KeyValue.KVComparator comparator;
    private Iterator<Cell> iter;
    private Cell current;
  
    public CollectionBackedScanner(SortedSet<Cell> set) {
      this(set, KeyValue.COMPARATOR);
    }
  
    public CollectionBackedScanner(SortedSet<Cell> set,
        KeyValue.KVComparator comparator) {
      this.comparator = comparator;
      data = set;
      init();
    }
  
    public CollectionBackedScanner(List<Cell> list) {
      this(list, KeyValue.COMPARATOR);
    }
  
    public CollectionBackedScanner(List<Cell> list,
        KeyValue.KVComparator comparator) {
      Collections.sort(list, comparator);
      this.comparator = comparator;
      data = list;
      init();
    }
  
    public CollectionBackedScanner(KeyValue.KVComparator comparator,
        Cell... array) {
      this.comparator = comparator;
  
      List<Cell> tmp = new ArrayList<Cell>(array.length);
      Collections.addAll(tmp, array);
      Collections.sort(tmp, comparator);
      data = tmp;
      init();
    }
  
    private void init() {
      iter = data.iterator();
      if(iter.hasNext()){
        current = iter.next();
      }
    }
  
    @Override
    public Cell peek() {
      return current;
    }
  
    @Override
    public Cell next() {
      Cell oldCurrent = current;
      if(iter.hasNext()){
        current = iter.next();
      } else {
        current = null;
      }
      return oldCurrent;
    }
  
   @Override
   public boolean seek(Cell seekCell) {
     // restart iterator
     iter = data.iterator();
     return reseek(seekCell);
   }
 
   @Override
   public boolean reseek(Cell seekCell) {
     while(iter.hasNext()){
       Cell next = iter.next();
       int ret = comparator.compare(next, seekCell);
       if(ret >= 0){
         current = next;
         return true;
       }
     }
     return false;
   }
 
   @Override
   public long getSequenceID() {
     return 0;
   }
 
   @Override
   public void close() {
     // do nothing
   }
 }