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* Copyright (c) Contributors, http://opensimulator.org/
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* THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY
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*/

using System;
using System.Collections.Generic;
using libsecondlife;
using OpenSim.Framework;
using OpenSim.Framework.Console;
using OpenSim.Region.Environment.Scenes;

namespace OpenSim.Region.Environment.Modules
{
    /// <summary>
    /// This module sets up texture senders in response to client texture requests, and places them on a
    /// processing queue once those senders have the appropriate data (i.e. a texture retrieved from the 
    /// asset cache).
    /// </summary>
    public class UserTextureDownloadService
    {
        private static readonly log4net.ILog m_log 
            = log4net.LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);
        
        /// <summary>
        /// Holds texture senders before they have received the appropriate texture from the asset cache.
        /// </summary>
        private readonly Dictionary<LLUUID, TextureSender> m_textureSenders = new Dictionary<LLUUID, TextureSender>();
        
        /// <summary>
        /// Texture Senders are placed in this queue once they have received their texture from the asset
        /// cache.  Another module actually invokes the send.
        /// </summary>
        private readonly BlockingQueue<TextureSender> m_sharedSendersQueue;
        
        private readonly Scene m_scene;

        public UserTextureDownloadService(Scene scene, BlockingQueue<TextureSender> sharedQueue)
        {
            m_scene = scene;
            m_sharedSendersQueue = sharedQueue;
        }

        /// <summary>
        /// Handle a texture request.  This involves creating a texture sender and placing it on the 
        /// previously passed in shared queue.
        /// </summary>
        /// <param name="client"> </param>
        /// <param name="e"></param>
        public void HandleTextureRequest(IClientAPI client, TextureRequestArgs e)
        {
            TextureSender textureSender;

            //TODO: should be working out the data size/ number of packets to be sent for each discard level
            if ((e.DiscardLevel >= 0) || (e.Priority != 0))
            {
                lock (m_textureSenders)
                {
                    if (m_textureSenders.TryGetValue(e.RequestedAssetID, out textureSender))
                    {
                        textureSender.UpdateRequest(e.DiscardLevel, e.PacketNumber);

                        if ((textureSender.ImageLoaded) &&
                            (textureSender.Sending == false))
                        {
                            EnqueueTextureSender(textureSender);
                        }
                    }
                    else
                    {
                        TextureSender requestHandler =
                            new TextureSender(client, e.DiscardLevel, e.PacketNumber);                        
                        m_textureSenders.Add(e.RequestedAssetID, requestHandler);
                        
                        m_scene.AssetCache.GetAsset(e.RequestedAssetID, TextureCallback, true);
                    }
                }
            }
            else
            {
                lock (m_textureSenders)
                {
                    if (m_textureSenders.TryGetValue(e.RequestedAssetID, out textureSender))
                    {
                        textureSender.Cancel = true;
                    }
                }
            }
        }

        /// <summary>
        /// The callback for the asset cache when a texture has been retrieved.  This method queues the
        /// texture sender for processing.
        /// </summary>
        /// <param name="textureID"></param>
        /// <param name="asset"></param>
        public void TextureCallback(LLUUID textureID, AssetBase texture)
        {
            lock (m_textureSenders)
            {
                TextureSender textureSender;

                if (m_textureSenders.TryGetValue(textureID, out textureSender))
                {
                    if (null != texture)
                    {
                        if (!textureSender.ImageLoaded)
                        {
                            textureSender.TextureReceived(texture);
                            EnqueueTextureSender(textureSender);
                        }
                    }
                    else
                    {
                        // Right now, leaving it up to lower level asset server code to post the fact that
                        // this texture could not be found
                        
                        // TODO Send packet back to the client telling it not to expect the texture
                        // The absence of this packet doesn't appear to be causing it a problem right now
                        
                        //m_log.InfoFormat("Removing {0} from pending downloads count", textureID);
                        m_scene.AddPendingDownloads(-1);
                    }
                    
                    //m_log.InfoFormat("[TEXTURE SENDER] Removing texture sender with uuid {0}", textureID);
                    m_textureSenders.Remove(textureID);                    
                    //m_log.InfoFormat("[TEXTURE SENDER] Current texture senders in dictionary: {0}", m_textureSenders.Count);
                }
                else
                {
                    throw new Exception("Got a texture with no sender object to handle it, this shouldn't happen");
                }
            }
        }

        /// <summary>
        /// Place a ready texture sender on the processing queue.
        /// </summary>
        /// <param name="textureSender"></param>
        private void EnqueueTextureSender(TextureSender textureSender)
        {
            textureSender.Cancel = false;
            textureSender.Sending = true;
            textureSender.counter = 0;

            if (!m_sharedSendersQueue.Contains(textureSender))
            {
                m_sharedSendersQueue.Enqueue(textureSender);
            }
        }

        /// <summary>
        /// Close this module.
        /// </summary>
        internal void Close()
        {
            lock (m_textureSenders)
            {
                foreach( TextureSender textureSender in m_textureSenders.Values )
                {
                    textureSender.Cancel = true;
                }

                m_textureSenders.Clear();
            }
        }
    }
}