/*
    * 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.log4j.chainsaw;
  
  import java.util.AbstractList;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.List;
  
  
  /**
   *
   * CyclicBuffer implementation that is Object generic, and implements the List interface.
   *
   * Original CyclicBuffer @author Ceki Gülcü
   *
   * This implementation (although there's very little change) @author Paul Smith <psmith@apache.org>
   *
   */
  public class CyclicBufferList extends AbstractList implements List {
    Object[] ea;
    int first;
    int last;
    int numElems;
    int maxSize;
  
    /**
       Instantiate a new CyclicBuffer of at most <code>maxSize</code> events.
  
       The <code>maxSize</code> argument must a positive integer.
  
       @param maxSize The maximum number of elements in the buffer.
    */
    public CyclicBufferList(int maxSize) {
      if (maxSize < 1) {
        throw new IllegalArgumentException(
          "The maxSize argument (" + maxSize + ") is not a positive integer.");
      }
      this.maxSize = maxSize;
      clear();
    }
  
    public CyclicBufferList() {
      this(5000);
    }
  
    /**
     * Removes the element at the specified position in this list.
     * Shifts any subsequent elements to the left (subtracts one from their
     * indices).
     *
     * @param index the index of the element to removed.
     * @return the element that was removed from the list.
     * @throws    IndexOutOfBoundsException if index out of range <tt>(index
     *      &lt; 0 || index &gt;= size())</tt>.
     */
    public Object remove(int index) {
      Object oldValue = ea[index];
  
      List list = new ArrayList(Arrays.asList(ea));
      list.remove(index);
      ea = list.toArray(ea);
      numElems = ea.length;
      
      numElems--;
      if (--last <= 0) {
        last = numElems;
      }
  
      if (first == maxSize) {
        first = 0;
      }
      return oldValue;
    }
  
    public Object set(int index, Object element) {
      Object previous = ea[index];
      ea[index] = element;
  
      return previous;
    }
  
    /**
       Add an <code>event</code> as the last event in the buffer.
 
    */
   public boolean add(Object event) {
     ea[last] = event;
 
     if (++last == maxSize) {
       last = 0;
     }
 
     if (numElems < maxSize) {
       numElems++;
     } else if (++first == maxSize) {
       first = 0;
     }
 
     return true;
   }
 
   /**
      Get the <i>i</i>th oldest event currently in the buffer. If
      <em>i</em> is outside the range 0 to the number of elements
      currently in the buffer, then <code>null</code> is returned.
 
 
   */
   public Object get(int i) {
     if ((i < 0) || (i >= numElems)) {
       return null;
     }
 
     return ea[(first + i) % maxSize];
   }
 
   public int getMaxSize() {
     return maxSize;
   }
   
   public int getLast() {
       return last;
   }
 
   /**
      Get the oldest (first) element in the buffer. The oldest element
      is removed from the buffer.
   */
   public Object get() {
     Object r = null;
 
     if (numElems > 0) {
       numElems--;
       r = ea[first];
       ea[first] = null;
 
       if (++first == maxSize) {
         first = 0;
       }
     }
 
     return r;
   }
 
   /**
      Get the number of elements in the buffer. This number is
      guaranteed to be in the range 0 to <code>maxSize</code>
      (inclusive).
   */
   public int size() {
     return numElems;
   }
 
   /**
      Resize the cyclic buffer to <code>newSize</code>.
 
      @throws IllegalArgumentException if <code>newSize</code> is negative.
    */
   public void resize(int newSize) {
     if (newSize < 0) {
       throw new IllegalArgumentException(
         "Negative array size [" + newSize + "] not allowed.");
     }
 
     if (newSize == numElems) {
       return; // nothing to do
     }
 
     Object[] temp = new Object[newSize];
 
     int loopLen = (newSize < numElems) ? newSize : numElems;
 
     for (int i = 0; i < loopLen; i++) {
       temp[i] = ea[first];
       ea[first] = null;
 
       if (++first == numElems) {
         first = 0;
       }
     }
 
     ea = temp;
     first = 0;
     numElems = loopLen;
     maxSize = newSize;
 
     if (loopLen == newSize) {
       last = 0;
     } else {
       last = loopLen;
     }
   }
   /* (non-Javadoc)
    * @see java.util.Collection#clear()
    */
   public void clear() {
     ea = new Object[maxSize];
     first = 0;
     last = 0;
     numElems = 0;
     
   }
 
 }