/*
 * 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 OpenSimulator 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 log4net;
using System;
using System.Threading;
using System.Collections.Generic;
using System.Collections.Concurrent;
using System.IO;
using System.Reflection;
using System.Timers;
using Nini.Config;
using OpenSim.Framework;
using OpenSim.Framework.Monitoring;
using OpenSim.Services.Interfaces;
using OpenMetaverse;

namespace OpenSim.Services.Connectors
{
    public class AssetServicesConnector : BaseServiceConnector, IAssetService
    {
        private static readonly ILog m_log =
                LogManager.GetLogger(
                MethodBase.GetCurrentMethod().DeclaringType);

        const int MAXSENDRETRIESLEN = 30;

        private IAssetCache m_Cache = null;
        private int m_retryCounter;
        private bool m_inRetries;
        private List<AssetBase>[] m_sendRetries = new  List<AssetBase>[MAXSENDRETRIESLEN];
        private System.Timers.Timer m_retryTimer;
        private int m_maxAssetRequestConcurrency = 30;

        private List<String> m_assetServers = new List<String>();

        private delegate void AssetRetrievedEx(AssetBase asset);

        // Keeps track of concurrent requests for the same asset, so that it's only loaded once.
        // Maps: Asset ID -> Handlers which will be called when the asset has been loaded
//        private Dictionary<string, AssetRetrievedEx> m_AssetHandlers = new Dictionary<string, AssetRetrievedEx>();

        private Dictionary<string, List<AssetRetrievedEx>> m_AssetHandlers = new Dictionary<string, List<AssetRetrievedEx>>();

        private Dictionary<string, string> m_UriMap = new Dictionary<string, string>();

        private Thread[] m_fetchThreads;

        public int MaxAssetRequestConcurrency
        {
            get { return m_maxAssetRequestConcurrency; }
            set { m_maxAssetRequestConcurrency = value; }
        }

        public AssetServicesConnector()
        {
        }

        public AssetServicesConnector(string serverURI)
        {
            m_assetServers.AddRange(serverURI.TrimEnd('/').Split(';'));
        }

        public AssetServicesConnector(IConfigSource source)
            : base(source, "AssetService")
        {
            Initialise(source);
        }

        public virtual void Initialise(IConfigSource source)
        {
            IConfig netconfig = source.Configs["Network"];
            if (netconfig != null)
                m_maxAssetRequestConcurrency = netconfig.GetInt("MaxRequestConcurrency",m_maxAssetRequestConcurrency);

            IConfig assetConfig = source.Configs["AssetService"];
            if (assetConfig == null)
            {
                m_log.Error("[ASSET CONNECTOR]: AssetService missing from OpenSim.ini");
                throw new Exception("Asset connector init error");
            }

            m_assetServers.AddRange(assetConfig.GetString("AssetServerURI", String.Empty).Split(';'));
            if (m_assetServers.Count == 0)
            {
                m_log.Error("[ASSET CONNECTOR]: No Server URI named in section AssetService");
                throw new Exception("Asset connector init error");
            }

            m_retryTimer = new System.Timers.Timer();
            m_retryTimer.Elapsed += new ElapsedEventHandler(retryCheck);
            m_retryTimer.AutoReset = true;
            m_retryTimer.Interval = 60000;

            Uri serverUri = new Uri(m_assetServers[0]);

            string groupHost = serverUri.Host;

            for (int i = 0 ; i < 256 ; i++)
            {
                string prefix = i.ToString("x2");
                groupHost = assetConfig.GetString("AssetServerHost_"+prefix, groupHost);

                m_UriMap[prefix] = groupHost;
                //m_log.DebugFormat("[ASSET]: Using {0} for prefix {1}", groupHost, prefix);
            }

            m_fetchThreads = new Thread[2];

            for (int i = 0 ; i < 2 ; i++)
            {
                m_fetchThreads[i] = WorkManager.StartThread(AssetRequestProcessor, String.Format("GetAssetsWorker{0}", i));
            }
        }

        private string MapServer(String m_ServerURI, string id)
        {
            if (m_UriMap.Count == 0)
                return m_ServerURI;

            UriBuilder serverUri = new UriBuilder(m_ServerURI);

            string prefix = id.Substring(0, 2).ToLower();

            string host;

            // HG URLs will not be valid UUIDS
            if (m_UriMap.ContainsKey(prefix))
                host = m_UriMap[prefix];
            else
                host = m_UriMap["00"];

            serverUri.Host = host;

            // m_log.DebugFormat("[ASSET]: Using {0} for host name for prefix {1}", host, prefix);

            string ret = serverUri.Uri.AbsoluteUri;
            if (ret.EndsWith("/"))
                ret = ret.Substring(0, ret.Length - 1);
            return ret;
        }

        protected void retryCheck(object source, ElapsedEventArgs e)
        {
            lock(m_sendRetries)
            {
                if(m_inRetries)
                    return;
                m_inRetries = true;
            }

            m_retryCounter++;
            if(m_retryCounter >= 61 ) // avoid overflow 60 is max in use below
                m_retryCounter = 1;

            int inUse = 0;
            int nextlevel;
            int timefactor;
            List<AssetBase> retrylist;
            // we need to go down
            for(int i = MAXSENDRETRIESLEN - 1; i >= 0; i--)
            {
                lock(m_sendRetries)
                    retrylist = m_sendRetries[i];

                if(retrylist == null)
                    continue;

                inUse++;
                nextlevel = i + 1;

                //We exponentially fall back on frequency until we reach one attempt per hour
                //The net result is that we end up in the queue for roughly 24 hours..
                //24 hours worth of assets could be a lot, so the hope is that the region admin
                //will have gotten the asset connector back online quickly!
                if(i == 0)
                    timefactor = 1;
                else
                {
                    timefactor = 1 << nextlevel;
                    if (timefactor > 60)
                        timefactor = 60;
                }

                if(m_retryCounter < timefactor)
                    continue; // to update inUse;

                if (m_retryCounter % timefactor != 0)
                    continue;

                // a list to retry
                lock(m_sendRetries)
                    m_sendRetries[i] = null;

                // we are the only ones with a copy of this retrylist now
                foreach(String server in m_assetServers)
                    foreach (AssetBase ass in retrylist)
                        retryStore(server, ass, nextlevel);
            }

            lock(m_sendRetries)
            {
                if(inUse == 0 )
                    m_retryTimer.Stop();

                m_inRetries = false;
            }
        }

        protected void SetCache(IAssetCache cache)
        {
            m_Cache = cache;
        }

        public AssetBase Get(string id)
        {
            foreach(String serverURL in m_assetServers)
            {
                AssetBase asset = Get(serverURL, id);

                if (asset != null)
                    return asset;
            }

            return null;
        }

        public AssetBase Get(String m_ServerURI, string id)
        {
            AssetBase asset = null;
            if (m_Cache != null)
            {
                if (!m_Cache.Get(id, out asset))
                    return null;
            }

            if (asset == null || asset.Data == null || asset.Data.Length == 0)
            {
                string uri = MapServer(m_ServerURI, id) + "/assets/" + id;
                asset = SynchronousRestObjectRequester.MakeRequest<int, AssetBase>("GET", uri, 0, m_Auth);
                if (m_Cache != null)
                {
                    if (asset != null)
                        m_Cache.Cache(asset);
                    else
                        m_Cache.CacheNegative(id);
                }
            }
            return asset;
        }

        public AssetBase GetCached(string id)
        {
//            m_log.DebugFormat("[ASSET SERVICE CONNECTOR]: Cache request for {0}", id);

            AssetBase asset = null;
            if (m_Cache != null)
            {
                m_Cache.Get(id, out asset);
            }

            return asset;
        }

        public AssetMetadata GetMetadata(string id)
        {
            foreach (String serverURL in m_assetServers)
            {
                AssetMetadata meta = GetMetadata(serverURL, id);

                if (meta != null)
                    return meta;
            }

            return null;
        }

        public AssetMetadata GetMetadata(String m_ServerURI, string id)
        {
            if (m_Cache != null)
            {
                AssetBase fullAsset;
                if (!m_Cache.Get(id, out fullAsset))
                    return null;

                if (fullAsset != null)
                    return fullAsset.Metadata;
            }

            string uri = MapServer(m_ServerURI, id) + "/assets/" + id + "/metadata";

            AssetMetadata asset = SynchronousRestObjectRequester.MakeRequest<int, AssetMetadata>("GET", uri, 0, m_Auth);
            return asset;
        }

        public byte[] GetData(string id)
        {
            foreach (String serverURL in m_assetServers)
            {
                byte[] data = GetData(serverURL, id);

                if (data != null)
                    return data;
            }

            return null;
        }

        public byte[] GetData(String m_ServerURI, string id)
        {
            if (m_Cache != null)
            {
                AssetBase fullAsset;
                if (!m_Cache.Get(id, out fullAsset))
                    return null;

                if (fullAsset != null)
                    return fullAsset.Data;
            }

            using (RestClient rc = new RestClient(MapServer(m_ServerURI, id)))
            {
                rc.AddResourcePath("assets");
                rc.AddResourcePath(id);
                rc.AddResourcePath("data");

                rc.RequestMethod = "GET";

                using (Stream s = rc.Request(m_Auth))
                {
                    if (s == null)
                        return null;

                    if (s.Length > 0)
                    {
                        byte[] ret = new byte[s.Length];
                        s.Read(ret, 0, (int)s.Length);

                        return ret;
                    }
                }
                return null;
            }
        }

        private class QueuedAssetRequest
        {
            public string uri;
            public string id;
        }

        private BlockingCollection<QueuedAssetRequest> m_requestQueue = new BlockingCollection<QueuedAssetRequest>();

        private void AssetRequestProcessor()
        {
            QueuedAssetRequest r;

            while (true)
            {
                if(!m_requestQueue.TryTake(out r, 4500) || r == null)
                {
                    Watchdog.UpdateThread();
                    continue;
                }

                Watchdog.UpdateThread();
                string uri = r.uri;
                string id = r.id;

                try
                {
                    AssetBase a = SynchronousRestObjectRequester.MakeRequest<int, AssetBase>("GET", uri, 0, 30000, m_Auth);

                    if (a != null && m_Cache != null)
                        m_Cache.Cache(a);

                    List<AssetRetrievedEx> handlers;
                    lock (m_AssetHandlers)
                    {
                        handlers = m_AssetHandlers[id];
                        m_AssetHandlers.Remove(id);
                    }

                    if(handlers != null)
                    {
                        Util.FireAndForget(x =>
                        {
                            foreach (AssetRetrievedEx h in handlers)
                            {
                                try { h.Invoke(a); }
                                catch { }
                            }
                            handlers.Clear();
                        });
                    }
                }
                catch { }
            }
        }

        public bool Get(string id, Object sender, AssetRetrieved handler)
        {
            foreach(String serverURL in m_assetServers)
            {
                bool result = Get(serverURL, id, sender, handler);

                if (result == true)
                    return result;
            }

            return false;
        }

        public bool Get(String m_ServerURI, string id, Object sender, AssetRetrieved handler)
        {
            string uri = MapServer(m_ServerURI, id) + "/assets/" + id;

            AssetBase asset = null;
            if (m_Cache != null)
            {
                if (!m_Cache.Get(id, out asset))
                    return false;
            }

            if (asset == null || asset.Data == null || asset.Data.Length == 0)
            {
                lock (m_AssetHandlers)
                {
                    AssetRetrievedEx handlerEx = new AssetRetrievedEx(delegate(AssetBase _asset) { handler(id, sender, _asset); });

                    List<AssetRetrievedEx> handlers;
                    if (m_AssetHandlers.TryGetValue(id, out handlers))
                    {
                        // Someone else is already loading this asset. It will notify our handler when done.
                        handlers.Add(handlerEx);
                        return true;
                    }

                    handlers = new List<AssetRetrievedEx>();
                    handlers.Add(handlerEx);

                    m_AssetHandlers.Add(id, handlers);

                    QueuedAssetRequest request = new QueuedAssetRequest();
                    request.id = id;
                    request.uri = uri;
                    m_requestQueue.Add(request);
                }
            }
            else
            {
                handler(id, sender, asset);
            }

            return true;
        }

        public virtual bool[] AssetsExist(string[] ids)
        {
            foreach (String serverURL in m_assetServers)
            {
                bool[] result = AssetsExist(serverURL, ids);

                return result;
            }

            return null;
        }

        public virtual bool[] AssetsExist(String m_ServerURI, string[] ids)
        {
            string uri = m_ServerURI + "/get_assets_exist";

            bool[] exist = null;
            try
            {
                exist = SynchronousRestObjectRequester.MakeRequest<string[], bool[]>("POST", uri, ids, m_Auth);
            }
            catch (Exception)
            {
                // This is most likely to happen because the server doesn't support this function,
                // so just silently return "doesn't exist" for all the assets.
            }

            if (exist == null)
                exist = new bool[ids.Length];

            return exist;
        }

        string stringUUIDZero = UUID.Zero.ToString();

        public string Store(AssetBase asset)
        {
            String result = null;

            foreach (String serverURL in m_assetServers)
            {
                result = Store(serverURL, asset);
            }

            return result;
        }

        public string Store(String m_ServerURI, AssetBase asset)
        {
            // Have to assign the asset ID here. This isn't likely to
            // trigger since current callers don't pass emtpy IDs
            // We need the asset ID to route the request to the proper
            // cluster member, so we can't have the server assign one.
            if (asset.ID == string.Empty || asset.ID == stringUUIDZero)
            {
                if (asset.FullID == UUID.Zero)
                {
                    asset.FullID = UUID.Random();
                }
                m_log.WarnFormat("[Assets] Zero ID: {0}",asset.Name);
                asset.ID = asset.FullID.ToString();
            }

            if (asset.FullID == UUID.Zero)
            {
                UUID uuid = UUID.Zero;
                if (UUID.TryParse(asset.ID, out uuid))
                {
                    asset.FullID = uuid;
                }
                if(asset.FullID == UUID.Zero)
                {
                    m_log.WarnFormat("[Assets] Zero IDs: {0}",asset.Name);
                    asset.FullID = UUID.Random();
                    asset.ID = asset.FullID.ToString();
                }
            }

            if (m_Cache != null)
                m_Cache.Cache(asset);

            if (asset.Temporary || asset.Local)
            {
                return asset.ID;
            }

            string uri = MapServer(m_ServerURI, asset.FullID.ToString()) + "/assets/";

            string newID = null;
            try
            {
                newID = SynchronousRestObjectRequester.
                        MakeRequest<AssetBase, string>("POST", uri, asset, 10000, m_Auth);
            }
            catch
            {
                newID = null;
            }

            if (newID == null || newID == String.Empty || newID == stringUUIDZero)
            {
                //The asset upload failed, try later
                lock(m_sendRetries)
                {
                    if (m_sendRetries[0] == null)
                        m_sendRetries[0] = new List<AssetBase>();
                    List<AssetBase> m_queue = m_sendRetries[0];
                    m_queue.Add(asset);
                    m_log.WarnFormat("[Assets] Upload failed: {0} type {1} will retry later",
                            asset.ID.ToString(), asset.Type.ToString());
                    m_retryTimer.Start();
                }
            }
            else
            {
                if (newID != asset.ID)
                {
                    // Placing this here, so that this work with old asset servers that don't send any reply back
                    // SynchronousRestObjectRequester returns somethins that is not an empty string

                    asset.ID = newID;
                }
            }
            if (m_Cache != null)
                m_Cache.Cache(asset);

            return asset.ID;
        }

        public void retryStore(AssetBase asset, int nextRetryLevel)
        {
            foreach (String serverURL in m_assetServers)
            {
                retryStore(serverURL, asset, nextRetryLevel);
            }
        }

        public void retryStore(String m_ServerURI, AssetBase asset, int nextRetryLevel)
        {
/* this may be bad, so excluding
            if (m_Cache != null && !m_Cache.Check(asset.ID))
            {
                m_log.WarnFormat("[Assets] Upload giveup asset bc no longer in local cache: {0}",
                    asset.ID.ToString();
                return; // if no longer in cache, it was deleted or expired
            }
*/
            string uri = MapServer(m_ServerURI, asset.FullID.ToString()) + "/assets/";

            string newID = null;
            try
            {
                newID = SynchronousRestObjectRequester.
                        MakeRequest<AssetBase, string>("POST", uri, asset, 100000, m_Auth);
            }
            catch
            {
                newID = null;
            }

            if (newID == null || newID == String.Empty || newID == stringUUIDZero)
            {
                if(nextRetryLevel >= MAXSENDRETRIESLEN)
                    m_log.WarnFormat("[Assets] Giving up on uploading after {2} retries id: {0} type {1}",
                            asset.ID.ToString(), asset.Type.ToString(), MAXSENDRETRIESLEN);
                else
                {
                    lock(m_sendRetries)
                    {
                        if (m_sendRetries[nextRetryLevel] == null)
                        {
                            m_sendRetries[nextRetryLevel] = new List<AssetBase>();
                        }
                        List<AssetBase> m_queue = m_sendRetries[nextRetryLevel];
                        m_queue.Add(asset);
                    m_log.WarnFormat("[Assets] Upload failed: {0} type {1} will retry later",
                            asset.ID.ToString(), asset.Type.ToString());
                    }
                }
            }
            else
            {
                m_log.InfoFormat("[Assets] Upload of {0} succeeded after {1} failed attempts", asset.ID.ToString(), nextRetryLevel.ToString());
                if (newID != asset.ID)
                {
                     asset.ID = newID;
                }
            }

            m_Cache?.Cache(asset);
        }

        public bool UpdateContent(string id, byte[] data)
        {
            bool result = false;

            foreach (String serverURL in m_assetServers)
            {
                result = UpdateContent(serverURL, id, data);
            }

            return result;
        }

        public bool UpdateContent(String m_ServerURI, string id, byte[] data)
        {
            AssetBase asset = null;

            m_Cache?.Get(id, out asset);

            if (asset == null)
            {
                AssetMetadata metadata = GetMetadata(m_ServerURI, id);
                if (metadata == null)
                    return false;

                asset = new AssetBase(metadata.FullID, metadata.Name, metadata.Type, UUID.Zero.ToString());
                asset.Metadata = metadata;
            }
            asset.Data = data;

            string uri = MapServer(m_ServerURI, id) + "/assets/" + id;

            if (SynchronousRestObjectRequester.MakeRequest<AssetBase, bool>("POST", uri, asset, m_Auth))
            {
                m_Cache?.Cache(asset, true);
                return true;
            }
            return false;
        }

        public bool Delete(string id)
        {
            bool result = false;

            foreach (String serverURL in m_assetServers)
            {
                result = Delete(serverURL, id);
            }

            return result;
        }

        public bool Delete(String m_ServerURI, string id)
        {
            string uri = MapServer(m_ServerURI, id) + "/assets/" + id;

            if (SynchronousRestObjectRequester.MakeRequest<int, bool>("DELETE", uri, 0, m_Auth))
            {
                if (m_Cache != null)
                    m_Cache.Expire(id);

                return true;
            }
            return false;
        }
    }
}