/**
    * Logback: the reliable, generic, fast and flexible logging framework.
    * Copyright (C) 1999-2011, QOS.ch. All rights reserved.
    *
    * This program and the accompanying materials are dual-licensed under
    * either the terms of the Eclipse Public License v1.0 as published by
    * the Eclipse Foundation
    *
    *   or (per the licensee's choosing)
   *
   * under the terms of the GNU Lesser General Public License version 2.1
   * as published by the Free Software Foundation.
   */
  package ch.qos.logback.core.helpers;
  
  import java.util.ArrayList;
  import java.util.List;
  
  /**
   * CyclicBuffer holds values in a cyclic array.
   * 
   * <p>It allows read access to any element in the buffer not just the first or
   * last element.
   * 
   * @author Ceki G&uuml;lc&uuml;
   */
  public class CyclicBuffer<E> {
  
    E[] 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 CyclicBuffer(int maxSize) throws IllegalArgumentException {
      if (maxSize < 1) {
        throw new IllegalArgumentException("The maxSize argument (" + maxSize
            + ") is not a positive integer.");
      }
      init(maxSize);
    }
  
    public CyclicBuffer(CyclicBuffer<E> other) {
     this.maxSize = other.maxSize;
     ea = (E[]) new Object[maxSize];
     System.arraycopy(other.ea, 0, this.ea, 0, maxSize);
     this.last = other.last;
     this.first = other.first;
     this.numElems = other.numElems;
    }
  
    @SuppressWarnings("unchecked")
    private void init(int maxSize) {
      this.maxSize = maxSize;
      ea = (E[]) new Object[maxSize];
      first = 0;
      last = 0;
      numElems = 0;
    }
  
    /**
     * Clears the buffer and resets all attributes.
     */
    public void clear() {
      init(this.maxSize);
    }
  
    /**
     * Add an <code>event</code> as the last event in the buffer.
     * 
     */
    public void add(E event) {
      ea[last] = event;
      if (++last == maxSize)
        last = 0;
  
      if (numElems < maxSize)
        numElems++;
      else if (++first == maxSize)
        first = 0;
    }
  
    /**
     * 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 E get(int i) {
      if (i < 0 || i >= numElems)
        return null;
  
     return ea[(first + i) % maxSize];
   }
 
   public int getMaxSize() {
     return maxSize;
   }
 
   /**
    * Get the oldest (first) element in the buffer. The oldest element is removed
    * from the buffer.
    */
   public E get() {
     E r = null;
     if (numElems > 0) {
       numElems--;
       r = ea[first];
       ea[first] = null;
       if (++first == maxSize)
         first = 0;
     }
     return r;
   }
   
   public List<E> asList() {
     List<E> tList = new ArrayList<E>();
     for(int i = 0; i < length(); i++) {
       tList.add(get(i));
     }
     return tList;
   }
 
   /**
    * 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 length() {
     return numElems;
   }
 
   /**
    * Resize the cyclic buffer to <code>newSize</code>.
    * 
    * @throws IllegalArgumentException
    *                 if <code>newSize</code> is negative.
    */
   @SuppressWarnings("unchecked")
   public void resize(int newSize) {
     if (newSize < 0) {
       throw new IllegalArgumentException("Negative array size [" + newSize
           + "] not allowed.");
     }
     if (newSize == numElems)
       return; // nothing to do
 
     // 
     E[] temp = (E[]) 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;
     }
   }
 }