/*
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 * See CONTRIBUTORS.TXT for a full list of copyright holders.
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 * modification, are permitted provided that the following conditions are met:
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 *       notice, this list of conditions and the following disclaimer.
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 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
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 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
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 * THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

using System;
using System.Collections.Generic;
using System.Reflection;
using System.Threading;
using System.Timers;
using log4net;
using OpenMetaverse;
using OpenSim.Framework;
using OpenSim.Framework.Serialization;
using OpenSim.Framework.Serialization.External;
using OpenSim.Services.Interfaces;

namespace OpenSim.Region.CoreModules.World.Archiver
{
    /// <summary>
    /// Encapsulate the asynchronous requests for the assets required for an archive operation
    /// </summary>
    class AssetsRequest
    {
        private static readonly ILog m_log = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);

        /// <summary>
        /// Method called when all the necessary assets for an archive request have been received.
        /// </summary>
        public delegate void AssetsRequestCallback(
            ICollection<UUID> assetsFoundUuids, ICollection<UUID> assetsNotFoundUuids, bool timedOut);

        enum RequestState
        {
            Initial,
            Running,
            Completed,
            Aborted
        };
        
        /// <value>
        /// Timeout threshold if we still need assets or missing asset notifications but have stopped receiving them
        /// from the asset service
        /// </value>
        protected const int TIMEOUT = 60 * 1000;

        /// <value>
        /// If a timeout does occur, limit the amount of UUID information put to the console.
        /// </value>
        protected const int MAX_UUID_DISPLAY_ON_TIMEOUT = 3;
       
        protected System.Timers.Timer m_requestCallbackTimer;

        /// <value>
        /// State of this request
        /// </value>
        private RequestState m_requestState = RequestState.Initial;
        
        /// <value>
        /// uuids to request
        /// </value>
        protected IDictionary<UUID, AssetType> m_uuids;

        /// <value>
        /// Callback used when all the assets requested have been received.
        /// </value>
        protected AssetsRequestCallback m_assetsRequestCallback;

        /// <value>
        /// List of assets that were found.  This will be passed back to the requester.
        /// </value>
        protected List<UUID> m_foundAssetUuids = new List<UUID>();
        
        /// <value>
        /// Maintain a list of assets that could not be found.  This will be passed back to the requester.
        /// </value>
        protected List<UUID> m_notFoundAssetUuids = new List<UUID>();

        /// <value>
        /// Record the number of asset replies required so we know when we've finished
        /// </value>
        private int m_repliesRequired;

        /// <value>
        /// Asset service used to request the assets
        /// </value>
        protected IAssetService m_assetService;
        protected IUserAccountService m_userAccountService;
        protected UUID m_scopeID; // the grid ID 

        protected AssetsArchiver m_assetsArchiver;

        protected Dictionary<string, object> m_options;

        protected internal AssetsRequest(
            AssetsArchiver assetsArchiver, IDictionary<UUID, AssetType> uuids, 
            IAssetService assetService, IUserAccountService userService, 
            UUID scope, Dictionary<string, object> options, 
            AssetsRequestCallback assetsRequestCallback)
        {
            m_assetsArchiver = assetsArchiver;
            m_uuids = uuids;
            m_assetsRequestCallback = assetsRequestCallback;
            m_assetService = assetService;
            m_userAccountService = userService;
            m_scopeID = scope;
            m_options = options;
            m_repliesRequired = uuids.Count;

            // FIXME: This is a really poor way of handling the timeout since it will always leave the original requesting thread
            // hanging.  Need to restructure so an original request thread waits for a ManualResetEvent on asset received
            // so we can properly abort that thread.  Or request all assets synchronously, though that would be a more
            // radical change
            m_requestCallbackTimer = new System.Timers.Timer(TIMEOUT);
            m_requestCallbackTimer.AutoReset = false;
            m_requestCallbackTimer.Elapsed += new ElapsedEventHandler(OnRequestCallbackTimeout);
        }

        protected internal void Execute()
        {
            m_requestState = RequestState.Running;
            
            m_log.DebugFormat("[ARCHIVER]: AssetsRequest executed looking for {0} possible assets", m_repliesRequired);
            
            // We can stop here if there are no assets to fetch
            if (m_repliesRequired == 0)
            {
                m_requestState = RequestState.Completed;
                PerformAssetsRequestCallback(false);
                return;
            }

            m_requestCallbackTimer.Enabled = true;

            foreach (KeyValuePair<UUID, AssetType> kvp in m_uuids)
            {
//                m_log.DebugFormat("[ARCHIVER]: Requesting asset {0}", kvp.Key);

//                m_assetService.Get(kvp.Key.ToString(), kvp.Value, PreAssetRequestCallback);
                AssetBase asset = m_assetService.Get(kvp.Key.ToString());
                PreAssetRequestCallback(kvp.Key.ToString(), kvp.Value, asset);
            }
        }

        protected void OnRequestCallbackTimeout(object source, ElapsedEventArgs args)
        {
            bool timedOut = true;

            try
            {
                lock (this)
                {
                    // Take care of the possibilty that this thread started but was paused just outside the lock before
                    // the final request came in (assuming that such a thing is possible)
                    if (m_requestState == RequestState.Completed)
                    {
                        timedOut = false;
                        return;
                    }
                    
                    m_requestState = RequestState.Aborted;
                }

                // Calculate which uuids were not found.  This is an expensive way of doing it, but this is a failure
                // case anyway.
                List<UUID> uuids = new List<UUID>();
                foreach (UUID uuid in m_uuids.Keys)
                {
                    uuids.Add(uuid);
                }

                foreach (UUID uuid in m_foundAssetUuids)
                {
                    uuids.Remove(uuid);
                }
    
                foreach (UUID uuid in m_notFoundAssetUuids)
                {
                    uuids.Remove(uuid);
                }
    
                m_log.ErrorFormat(
                    "[ARCHIVER]: Asset service failed to return information about {0} requested assets", uuids.Count);
    
                int i = 0;
                foreach (UUID uuid in uuids)
                {
                    m_log.ErrorFormat("[ARCHIVER]: No information about asset {0} received", uuid);
    
                    if (++i >= MAX_UUID_DISPLAY_ON_TIMEOUT)
                        break;
                }
    
                if (uuids.Count > MAX_UUID_DISPLAY_ON_TIMEOUT)
                    m_log.ErrorFormat(
                        "[ARCHIVER]: (... {0} more not shown)", uuids.Count - MAX_UUID_DISPLAY_ON_TIMEOUT);

                m_log.Error("[ARCHIVER]: Archive save aborted.  PLEASE DO NOT USE THIS ARCHIVE, IT WILL BE INCOMPLETE.");
            }
            catch (Exception e)
            {
                m_log.ErrorFormat("[ARCHIVER]: Timeout handler exception {0}{1}", e.Message, e.StackTrace);
            }
            finally
            {
                if (timedOut)
                    Util.FireAndForget(PerformAssetsRequestCallback, true);
            }
        }

        protected void PreAssetRequestCallback(string fetchedAssetID, object assetType, AssetBase fetchedAsset)
        {
            // Check for broken asset types and fix them with the AssetType gleaned by UuidGatherer
            if (fetchedAsset != null && fetchedAsset.Type == (sbyte)AssetType.Unknown)
            {
                AssetType type = (AssetType)assetType;
                m_log.InfoFormat("[ARCHIVER]: Rewriting broken asset type for {0} to {1}", fetchedAsset.ID, type);
                fetchedAsset.Type = (sbyte)type;
            }

            AssetRequestCallback(fetchedAssetID, this, fetchedAsset);
        }

        /// <summary>
        /// Called back by the asset cache when it has the asset
        /// </summary>
        /// <param name="assetID"></param>
        /// <param name="asset"></param>
        public void AssetRequestCallback(string id, object sender, AssetBase asset)
        {
            Culture.SetCurrentCulture();
            
            try
            {
                lock (this)
                {
                    //m_log.DebugFormat("[ARCHIVER]: Received callback for asset {0}", id);
                    
                    m_requestCallbackTimer.Stop();
                    
                    if ((m_requestState == RequestState.Aborted) || (m_requestState == RequestState.Completed))
                    {
                        m_log.WarnFormat(
                            "[ARCHIVER]: Received information about asset {0} while in state {1}.  Ignoring.", 
                            id, m_requestState);

                        return;
                    }
                                                           
                    if (asset != null)
                    {
                        if (m_options.ContainsKey("verbose"))
                            m_log.InfoFormat("[ARCHIVER]: Writing asset {0}", id);

                        m_foundAssetUuids.Add(asset.FullID);

                        m_assetsArchiver.WriteAsset(PostProcess(asset));
                    }
                    else
                    {
                        if (m_options.ContainsKey("verbose"))
                            m_log.InfoFormat("[ARCHIVER]: Recording asset {0} as not found", id);

                        m_notFoundAssetUuids.Add(new UUID(id));
                    }
        
                    if (m_foundAssetUuids.Count + m_notFoundAssetUuids.Count >= m_repliesRequired)
                    {
                        m_requestState = RequestState.Completed;
                        
                        m_log.DebugFormat(
                            "[ARCHIVER]: Successfully added {0} assets ({1} assets not found but these may be expected invalid references)",
                            m_foundAssetUuids.Count, m_notFoundAssetUuids.Count);
                        
                        // We want to stop using the asset cache thread asap 
                        // as we now need to do the work of producing the rest of the archive
                        Util.FireAndForget(PerformAssetsRequestCallback, false);
                    }
                    else
                    {
                        m_requestCallbackTimer.Start();
                    }
                }
            }
            catch (Exception e)
            {
                m_log.ErrorFormat("[ARCHIVER]: AssetRequestCallback failed with {0}", e);
            }
        }

        /// <summary>
        /// Perform the callback on the original requester of the assets
        /// </summary>
        protected void PerformAssetsRequestCallback(object o)
        {
            Culture.SetCurrentCulture();

            Boolean timedOut = (Boolean)o;

            try
            {
                m_assetsRequestCallback(m_foundAssetUuids, m_notFoundAssetUuids, timedOut);
            }
            catch (Exception e)
            {
                m_log.ErrorFormat(
                    "[ARCHIVER]: Terminating archive creation since asset requster callback failed with {0}", e);
            }
        }

        protected AssetBase PostProcess(AssetBase asset)
        {
            if (asset.Type == (sbyte)AssetType.Object && asset.Data != null && m_options.ContainsKey("home"))
            {
                //m_log.DebugFormat("[ARCHIVER]: Rewriting object data for {0}", asset.ID);
                string xml = ExternalRepresentationUtils.RewriteSOP(Utils.BytesToString(asset.Data), m_options["home"].ToString(), m_userAccountService, m_scopeID);
                asset.Data = Utils.StringToBytes(xml);
            }
            return asset;
        }
    }
}