/*
 * Copyright (c) Contributors, http://opensimulator.org/
 * See CONTRIBUTORS.TXT for a full list of copyright holders.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of the OpenSim Project nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

using System;
using System.Collections.Generic;
using OpenMetaverse;
using OpenMetaverse.Packets;

namespace OpenSim.Framework
{
    public sealed class PacketPool
    {
        private static readonly PacketPool instance = new PacketPool();

        private bool packetPoolEnabled = false;

        private readonly Dictionary<PacketType, Stack<Packet>> pool = new Dictionary<PacketType, Stack<Packet>>();

        static PacketPool()
        {
        }

        public static PacketPool Instance
        {
            get { return instance; }
        }

        public Packet GetPacket(PacketType type)
        {
            Packet packet;

            if (!packetPoolEnabled)
                return Packet.BuildPacket(type);

            lock (pool)
            {
                if (!pool.ContainsKey(type) || pool[type] == null || (pool[type]).Count == 0)
                {
                    // Creating a new packet if we cannot reuse an old package
                    packet = Packet.BuildPacket(type);
                }
                else
                {
                    // Recycle old packages
                    packet = (pool[type]).Pop();
                }
            }

            return packet;
        }

        // private byte[] decoded_header = new byte[10];
        private static PacketType GetType(byte[] bytes)
        {
            byte[] decoded_header = new byte[10 + 8];
            ushort id;
            PacketFrequency freq;

            if ((bytes[0] & Helpers.MSG_ZEROCODED) != 0)
            {
                Helpers.ZeroDecode(bytes, 16, decoded_header);
            }
            else
            {
                Buffer.BlockCopy(bytes, 0, decoded_header, 0, 10);
            }

            if (decoded_header[6] == 0xFF)
            {
                if (decoded_header[7] == 0xFF)
                {
                    id = (ushort) ((decoded_header[8] << 8) + decoded_header[9]);
                    freq = PacketFrequency.Low;
                }
                else
                {
                    id = decoded_header[7];
                    freq = PacketFrequency.Medium;
                }
            }
            else
            {
                id = decoded_header[6];
                freq = PacketFrequency.High;
            }

            return Packet.GetType(id, freq);
        }

        public Packet GetPacket(byte[] bytes, ref int packetEnd, byte[] zeroBuffer)
        {
            PacketType type = GetType(bytes);

            int z;
            for (z = 0 ; z < zeroBuffer.Length ; z++)
                zeroBuffer[z] = 0;

            int i = 0;
            Packet packet = GetPacket(type);
            packet.FromBytes(bytes, ref i, ref packetEnd, zeroBuffer);
            return packet;
        }

        /// <summary>
        /// Return a packet to the packet pool
        /// </summary>
        /// <param name="packet"></param>
        public void ReturnPacket(Packet packet)
        {
            if (!packetPoolEnabled)
                return;

            switch (packet.Type)
            {
                // List pooling packets here
                case PacketType.PacketAck:
                    lock (pool)
                    {
                        PacketType type = packet.Type;

                        if (!pool.ContainsKey(type))
                        {
                            pool[type] = new Stack<Packet>();
                        }
                        if ((pool[type]).Count < 50)
                        {
                            (pool[type]).Push(packet);
                        }
                    }
                    break;
                
                // Other packets wont pool
                default:
                    return;
            }
        }
    }
}
