/***************************************************************************
 *                               ByteQueue.cs
 *                            -------------------
 *   begin                : May 1, 2002
 *   copyright            : (C) The RunUO Software Team
 *   email                : info@runuo.com
 *
 *   $Id$
 *
 ***************************************************************************/

/***************************************************************************
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 ***************************************************************************/

using System;

namespace Server.Network
{
  public class ByteQueue
  {
    private byte[] m_Buffer;
    private int m_Head;
    private int m_Tail;

    public ByteQueue()
    {
      m_Buffer = new byte[2048];
    }

    public int Length{ get; private set; }

    public void Clear()
    {
      m_Head = 0;
      m_Tail = 0;
      Length = 0;
    }

    private void SetCapacity(int capacity)
    {
      byte[] newBuffer = new byte[capacity];

      if (Length > 0)
      {
        if (m_Head < m_Tail)
        {
          Buffer.BlockCopy(m_Buffer, m_Head, newBuffer, 0, Length);
        }
        else
        {
          Buffer.BlockCopy(m_Buffer, m_Head, newBuffer, 0, m_Buffer.Length - m_Head);
          Buffer.BlockCopy(m_Buffer, 0, newBuffer, m_Buffer.Length - m_Head, m_Tail);
        }
      }

      m_Head = 0;
      m_Tail = Length;
      m_Buffer = newBuffer;
    }

    public byte GetPacketID()
    {
      if (Length >= 1)
        return m_Buffer[m_Head];

      return 0xFF;
    }

    public int GetPacketLength()
    {
      if (Length >= 3)
        return (m_Buffer[(m_Head + 1) % m_Buffer.Length] << 8) | m_Buffer[(m_Head + 2) % m_Buffer.Length];

      return 0;
    }

    public int Dequeue(byte[] buffer, int offset, int size)
    {
      if (size > Length)
        size = Length;

      if (size == 0)
        return 0;

      if (m_Head < m_Tail)
      {
        Buffer.BlockCopy(m_Buffer, m_Head, buffer, offset, size);
      }
      else
      {
        int rightLength = m_Buffer.Length - m_Head;

        if (rightLength >= size)
        {
          Buffer.BlockCopy(m_Buffer, m_Head, buffer, offset, size);
        }
        else
        {
          Buffer.BlockCopy(m_Buffer, m_Head, buffer, offset, rightLength);
          Buffer.BlockCopy(m_Buffer, 0, buffer, offset + rightLength, size - rightLength);
        }
      }

      m_Head = (m_Head + size) % m_Buffer.Length;
      Length -= size;

      if (Length == 0)
      {
        m_Head = 0;
        m_Tail = 0;
      }

      return size;
    }

    public void Enqueue(byte[] buffer, int offset, int size)
    {
      if (Length + size > m_Buffer.Length)
        SetCapacity((Length + size + 2047) & ~2047);

      if (m_Head < m_Tail)
      {
        int rightLength = m_Buffer.Length - m_Tail;

        if (rightLength >= size)
        {
          Buffer.BlockCopy(buffer, offset, m_Buffer, m_Tail, size);
        }
        else
        {
          Buffer.BlockCopy(buffer, offset, m_Buffer, m_Tail, rightLength);
          Buffer.BlockCopy(buffer, offset + rightLength, m_Buffer, 0, size - rightLength);
        }
      }
      else
      {
        Buffer.BlockCopy(buffer, offset, m_Buffer, m_Tail, size);
      }

      m_Tail = (m_Tail + size) % m_Buffer.Length;
      Length += size;
    }
  }
}