/*
    * 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.
   * <p>
   * Original CyclicBuffer @author Ceki G&uuml;lc&uuml;
   * <p>
   * This implementation (although there's very little change) @author Paul Smith &lt;psmith@apache.org&gt;
   */
  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.
       * <p>
       * 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;
 
     }
 
 }