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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.thrift;

import java.util.ArrayList;

import java.util.Arrays;

import java.util.Collection;

import java.util.HashSet;

import java.util.Iterator;

import java.util.List;

import java.util.Set;

/**

 * IntRangeSet is a specialized Set<Integer> implementation designed 

 * specifically to make the generated validate() method calls faster. It groups

 * the set values into ranges, and in the contains() call, it does 

 * num ranges * 2 comparisons max. For the common case, which is a single, 

 * contiguous range, this approach is about 60% faster than using a HashSet. If

 * you had a very ragged value set, like all the odd numbers, for instance, 

 * then you would end up with pretty poor running time.  

 */

public class IntRangeSet implements Set<Integer> {

  /**

   * This array keeps the bounds of each extent in alternating cells, always 

   * increasing. Example: [0,5,10,15], which corresponds to 0-5, 10-15.

   */

  private int[] extents;

  /**

   * We'll keep a duplicate, real HashSet around internally to satisfy some of

   * the other set operations. 

   */

  private Set<Integer> realSet = new HashSet<Integer>();

  public IntRangeSet(int... values) {

    Arrays.sort(values);

    List<Integer> extent_list = new ArrayList<Integer>();

    int ext_start = values[0];

    int ext_end_so_far = values[0];

    for (int i = 1; i < values.length; i++) {

      realSet.add(values[i]);

      if (values[i] == ext_end_so_far + 1) {

        // advance the end so far

        ext_end_so_far = values[i];

      } else {

        // create an extent for everything we saw so far, move on to the next one

        extent_list.add(ext_start);

        extent_list.add(ext_end_so_far);

        ext_start = values[i];

        ext_end_so_far = values[i];

      }

    }

    extent_list.add(ext_start);

    extent_list.add(ext_end_so_far);

    extents = new int[extent_list.size()];

    for (int i = 0; i < extent_list.size(); i++) {

      extents[i] = extent_list.get(i);

    }

  }

  public boolean add(Integer i) {

    throw new UnsupportedOperationException();

  }

  public void clear() {

    throw new UnsupportedOperationException();

  }

  public boolean addAll(Collection<? extends Integer> arg0) {

    throw new UnsupportedOperationException();

  }

  /**

   * While this method is here for Set interface compatibility, you should avoid 

   * using it. It incurs boxing overhead! Use the int method directly, instead.

   */

  public boolean contains(Object arg0) {

    return contains(((Integer)arg0).intValue());

  }

  /**

   * This is much faster, since it doesn't stop at Integer on the way through.

   * @param val the value you want to check set membership for

   * @return true if val was found, false otherwise

   */

  public boolean contains(int val) {

    for (int i = 0; i < extents.length / 2; i++) {

      if (val < extents[i*2]) {

        return false;

      } else if (val <= extents[i*2+1]) {

        return true;

      }

    }

    return false;

  }

  public boolean containsAll(Collection<?> arg0) {

    for (Object o : arg0) {

      if (!contains(o)) {

        return false;

      }

    }

    return true;

  }

  public boolean isEmpty() {

    return realSet.isEmpty();

  }

  public Iterator<Integer> iterator() {

    return realSet.iterator();

  }

  public boolean remove(Object arg0) {

    throw new UnsupportedOperationException();

  }

  public boolean removeAll(Collection<?> arg0) {

    throw new UnsupportedOperationException();

  }

  public boolean retainAll(Collection<?> arg0) {

    throw new UnsupportedOperationException();

  }

  public int size() {

    return realSet.size();

  }

  public Object[] toArray() {

    return realSet.toArray();

  }

  public <T> T[] toArray(T[] arg0) {

    return realSet.toArray(arg0);

  }

  @Override

  public String toString() {

    String buf = "";

    for (int i = 0; i < extents.length / 2; i++) {

      if (i != 0) { 

        buf += ", ";

      }

      buf += "[" + extents[i*2] + "," + extents[i*2+1] + "]"; 

    }

    return buf;

  }

}