/*
* 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:
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*       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
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* 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 System.Text;
using System.Threading;
using libsecondlife;
using Nini.Config;
using OpenSim.Framework;
using OpenSim.Region.Environment.Scenes.Scripting;

namespace OpenSim.Region.ScriptEngine.Common.ScriptEngineBase
{
    /// <summary>
    /// Because every thread needs some data set for it (time started to execute current function), it will do its work within a class
    /// </summary>
    public class EventQueueThreadClass: iScriptEngineFunctionModule
    {
        /// <summary>
        /// How many ms to sleep if queue is empty
        /// </summary>
        private int nothingToDoSleepms;// = 50;
        private ThreadPriority MyThreadPriority;

        public long LastExecutionStarted;
        public bool InExecution = false;
        public bool KillCurrentScript = false;

        private EventQueueManager eventQueueManager;
        public Thread EventQueueThread;
        private static int ThreadCount = 0;

        private string ScriptEngineName = "ScriptEngine.Common";

        public EventQueueThreadClass(EventQueueManager eqm)
        {
            eventQueueManager = eqm;
            ReadConfig();
            Start();
        }

        ~EventQueueThreadClass()
        {
            Stop();
        }

        public void ReadConfig()
        {
            ScriptEngineName = eventQueueManager.m_ScriptEngine.ScriptEngineName;
            nothingToDoSleepms = eventQueueManager.m_ScriptEngine.ScriptConfigSource.GetInt("SleepTimeIfNoScriptExecutionMs", 50);

            // Later with ScriptServer we might want to ask OS for stuff too, so doing this a bit manually
            string pri = eventQueueManager.m_ScriptEngine.ScriptConfigSource.GetString("ScriptThreadPriority", "BelowNormal");
            switch (pri.ToLower())
            {
                case "lowest":
                    MyThreadPriority = ThreadPriority.Lowest;
                    break;
                case "belownormal":
                    MyThreadPriority = ThreadPriority.BelowNormal;
                    break;
                case "normal":
                    MyThreadPriority = ThreadPriority.Normal;
                    break;
                case "abovenormal":
                    MyThreadPriority = ThreadPriority.AboveNormal;
                    break;
                case "highest":
                    MyThreadPriority = ThreadPriority.Highest;
                    break;
                default:
                    MyThreadPriority = ThreadPriority.BelowNormal; // Default
                    eventQueueManager.m_ScriptEngine.Log.Error("[ScriptEngineBase]: Unknown priority type \"" + pri + "\" in config file. Defaulting to \"BelowNormal\".");
                    break;
            }

            // Now set that priority
            if (EventQueueThread != null)
                if (EventQueueThread.IsAlive)
                    EventQueueThread.Priority = MyThreadPriority;
        }

        /// <summary>
        /// Start thread
        /// </summary>
        private void Start()
        {
            EventQueueThread = new Thread(EventQueueThreadLoop);
            EventQueueThread.IsBackground = true;
            
            EventQueueThread.Priority = MyThreadPriority;
            EventQueueThread.Name = "EventQueueManagerThread_" + ThreadCount;
            EventQueueThread.Start();

            // Look at this... Don't you wish everyone did that solid coding everywhere? :P
            if (ThreadCount == int.MaxValue)
                ThreadCount = 0;
            ThreadCount++;
        }

        public void Stop()
        {
            PleaseShutdown = true;                  // Set shutdown flag
            Thread.Sleep(100);                       // Wait a bit
            if (EventQueueThread != null && EventQueueThread.IsAlive == true)
            {
                try
                {
                    EventQueueThread.Abort();               // Send abort
                    EventQueueThread.Join();                // Wait for it
                }
                catch (Exception)
                {
                    //myScriptEngine.Log.Info("[" + ScriptEngineName + "]: EventQueueManager Exception killing worker thread: " + e.ToString());
                }
            }
        }

        /// <summary>
        /// Queue processing thread loop
        /// </summary>
        private void EventQueueThreadLoop()
        {
            //myScriptEngine.Log.Info("[" + ScriptEngineName + "]: EventQueueManager Worker thread spawned");
            try
            {
               while (true)
                {
                    try
                    {
                        EventQueueManager.QueueItemStruct BlankQIS = new EventQueueManager.QueueItemStruct();
                        while (true)
                        {
                            // Every now and then check if we should shut down
                            if (PleaseShutdown || eventQueueManager.ThreadsToExit > 0)
                            {
                                // Someone should shut down, lets get exclusive lock
                                lock (eventQueueManager.ThreadsToExitLock)
                                {
                                    // Lets re-check in case someone grabbed it
                                    if (eventQueueManager.ThreadsToExit > 0)
                                    {
                                        // Its crowded here so we'll shut down
                                        eventQueueManager.ThreadsToExit--;
                                        Stop();
                                        return;
                                    }
                                    else
                                    {
                                        // We have been asked to shut down
                                        Stop();
                                        return;
                                    }
                                }
                            }

                            //try
                            //  {
                            EventQueueManager.QueueItemStruct QIS = BlankQIS;
                            bool GotItem = false;

                            if (PleaseShutdown)
                                return;

                            if (eventQueueManager.eventQueue.Count == 0)
                            {
                                // Nothing to do? Sleep a bit waiting for something to do
                                Thread.Sleep(nothingToDoSleepms);
                            }
                            else
                            {
                                // Something in queue, process
                                //myScriptEngine.Log.Info("[" + ScriptEngineName + "]: Processing event for localID: " + QIS.localID + ", itemID: " + QIS.itemID + ", FunctionName: " + QIS.FunctionName);

                                // OBJECT BASED LOCK - TWO THREADS WORKING ON SAME OBJECT IS NOT GOOD
                                lock (eventQueueManager.queueLock)
                                {
                                    GotItem = false;
                                    for (int qc = 0; qc < eventQueueManager.eventQueue.Count; qc++)
                                    {
                                        // Get queue item
                                        QIS = eventQueueManager.eventQueue.Dequeue();

                                        // Check if object is being processed by someone else
                                        if (eventQueueManager.TryLock(QIS.localID) == false)
                                        {
                                            // Object is already being processed, requeue it
                                            eventQueueManager.eventQueue.Enqueue(QIS);
                                        }
                                        else
                                        {
                                            // We have lock on an object and can process it
                                            GotItem = true;
                                            break;
                                        }
                                    } // go through queue
                                } // lock

                                if (GotItem == true)
                                {
                                    // Execute function
                                    try
                                    {
#if DEBUG
                                        eventQueueManager.m_ScriptEngine.Log.Debug("[" + ScriptEngineName + "]: " +
                                                                                      "Executing event:\r\n"
                                                                                      + "QIS.localID: " + QIS.localID
                                                                                      + ", QIS.itemID: " + QIS.itemID
                                                                                      + ", QIS.functionName: " +
                                                                                      QIS.functionName);
#endif
                                        LastExecutionStarted = DateTime.Now.Ticks;
                                        KillCurrentScript = false;
                                        InExecution = true;
                                        eventQueueManager.m_ScriptEngine.m_ScriptManager.ExecuteEvent(QIS.localID,
                                                                                                      QIS.itemID,
                                                                                                      QIS.functionName,
                                                                                                      QIS.llDetectParams,
                                                                                                      QIS.param);
                                        InExecution = false;
                                    }
                                    catch (Exception e)
                                    {
                                        InExecution = false;
                                        // DISPLAY ERROR INWORLD
                                        string text = "Error executing script function \"" + QIS.functionName +
                                                      "\":\r\n";
                                        if (e.InnerException != null)
                                        {
                                            // Send inner exception
                                            text += e.InnerException.Message.ToString();
                                        }
                                        else
                                        {
                                            text += "\r\n";
                                            // Send normal
                                            text += e.Message.ToString();
                                        }
                                        if (KillCurrentScript)
                                            text += "\r\nScript will be deactivated!";

                                        try
                                        {
                                            if (text.Length > 1500)
                                                text = text.Substring(0, 1500);
                                            IScriptHost m_host =
                                                eventQueueManager.m_ScriptEngine.World.GetSceneObjectPart(QIS.localID);
                                            //if (m_host != null)
                                            //{
                                            eventQueueManager.m_ScriptEngine.World.SimChat(Helpers.StringToField(text),
                                                                                           ChatTypeEnum.Say, 0,
                                                                                           m_host.AbsolutePosition,
                                                                                           m_host.Name, m_host.UUID);
                                        }
                                        catch
                                        {
                                            //}
                                            //else
                                            //{
                                            // T oconsole
                                            eventQueueManager.m_ScriptEngine.Log.Error("[" + ScriptEngineName + "]: " +
                                                                                          "Unable to send text in-world:\r\n" +
                                                                                          text);
                                        }
                                        finally
                                        {
                                            // So we are done sending message in-world
                                            if (KillCurrentScript)
                                            {
                                                eventQueueManager.m_ScriptEngine.m_ScriptManager.StopScript(
                                                    QIS.localID, QIS.itemID);
                                            }
                                        }
                                    }
                                    finally
                                    {
                                        InExecution = false;
                                        eventQueueManager.ReleaseLock(QIS.localID);
                                    }
                                }
                            } // Something in queue
                        }
                    }
                    catch (ThreadAbortException tae)
                    {
                        eventQueueManager.m_ScriptEngine.Log.Info("[" + ScriptEngineName + "]: ThreadAbortException while executing function.");
                    }
                    catch (Exception e)
                    {
                        eventQueueManager.m_ScriptEngine.Log.Error("[" + ScriptEngineName + "]: Exception in EventQueueThreadLoop: " + e.ToString());
                    }
                } // while
            } // try
            catch (ThreadAbortException)
            {
                //myScriptEngine.Log.Info("[" + ScriptEngineName + "]: EventQueueManager Worker thread killed: " + tae.Message);
            }
        }

        /// <summary>
        /// If set to true then threads and stuff should try to make a graceful exit
        /// </summary>
        public bool PleaseShutdown
        {
            get { return _PleaseShutdown; }
            set { _PleaseShutdown = value; }
        }
        private bool _PleaseShutdown = false;
    }
}