/**
    * Logback: the reliable, generic, fast and flexible logging framework.
    * Copyright (C) 1999-2015, 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);
      }
  
      @SuppressWarnings("unchecked")
      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;
         }
     }
 }