/*
 * 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
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 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

using System;
using System.Runtime.CompilerServices;
using System.Threading;
using log4net;

namespace OpenSim.Framework.Monitoring
{
    /// <summary>
    /// Manages various work items in the simulator.
    /// </summary>
    /// <remarks>
    /// Currently, here work can be started
    ///  * As a long-running and monitored thread.
    ///  * In a thread that will never timeout but where the job is expected to eventually complete.
    ///  * In a threadpool thread that will timeout if it takes a very long time to complete (> 10 mins).
    ///  * As a job which will be run in a single-threaded job engine.  Such jobs must not incorporate delays (sleeps,
    /// network waits, etc.).
    ///
    /// This is an evolving approach to better manage the work that OpenSimulator is asked to do from a very diverse
    /// range of sources (client actions, incoming network, outgoing network calls, etc.).
    ///
    /// </remarks>
    public static class WorkManager
    {
        private static readonly ILog m_log = LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);

        public static JobEngine JobEngine { get; private set; }

        static WorkManager()
        {
            JobEngine = new JobEngine("Non-blocking non-critical job engine", "JOB ENGINE", 30000);

            StatsManager.RegisterStat(
                new Stat(
                    "JobsWaiting",
                    "Number of jobs waiting for processing.",
                    "",
                    "",
                    "server",
                    "jobengine",
                    StatType.Pull,
                    MeasuresOfInterest.None,
                    stat => stat.Value = JobEngine == null ? 0 : JobEngine.JobsWaiting,
                    StatVerbosity.Debug));

            MainConsole.Instance.Commands.AddCommand(
                "Debug",
                false,
                "debug jobengine",
                "debug jobengine <start|stop|status|log>",
                "Start, stop, get status or set logging level of the job engine.",
                "If stopped then all outstanding jobs are processed immediately.",
                HandleControlCommand);
        }

        public static void Stop()
        {
            JobEngine.Stop();
            Watchdog.Stop();
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static Thread StartThread(ThreadStart start, string name, bool alarmIfTimeout = false, bool log = true)
        {
            return StartThread(start, name, ThreadPriority.Normal, true, alarmIfTimeout, null, Watchdog.DEFAULT_WATCHDOG_TIMEOUT_MS, log);
        }

        /// <summary>
        /// Start a new long-lived thread.
        /// </summary>
        /// <param name="start">The method that will be executed in a new thread</param>
        /// <param name="name">A name to give to the new thread</param>
        /// <param name="priority">Priority to run the thread at</param>
        /// <param name="isBackground">True to run this thread as a background thread, otherwise false</param>
        /// <param name="alarmIfTimeout">Trigger an alarm function is we have timed out</param>
        /// <param name="log">If true then creation of thread is logged.</param>
        /// <returns>The newly created Thread object</returns>
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static Thread StartThread(
            ThreadStart start, string name, ThreadPriority priority, bool alarmIfTimeout, bool log = true)
        {
            return StartThread(start, name, priority, true, alarmIfTimeout, null, Watchdog.DEFAULT_WATCHDOG_TIMEOUT_MS, log);
        }

        /// <summary>
        /// Start a new thread that is tracked by the watchdog
        /// </summary>
        /// <param name="start">The method that will be executed in a new thread</param>
        /// <param name="name">A name to give to the new thread</param>
        /// <param name="priority">Priority to run the thread at</param>
        /// <param name="isBackground">True to run this thread as a background
        /// thread, otherwise false</param>
        /// <param name="alarmIfTimeout">Trigger an alarm function is we have timed out</param>
        /// <param name="alarmMethod">
        /// Alarm method to call if alarmIfTimeout is true and there is a timeout.
        /// Normally, this will just return some useful debugging information.
        /// </param>
        /// <param name="timeout">Number of milliseconds to wait until we issue a warning about timeout.</param>
        /// <param name="log">If true then creation of thread is logged.</param>
        /// <returns>The newly created Thread object</returns>
        public static Thread StartThread(
            ThreadStart start, string name, ThreadPriority priority, bool isBackground,
            bool alarmIfTimeout, Func<string> alarmMethod, int timeout, bool log = true, bool SuspendFlow = true)
        {
            Thread thread;
            if(SuspendFlow)
            {
                using (ExecutionContext.SuppressFlow())
                {
                    thread = new Thread(start);
                }
            }
            else
            {
                thread = new Thread(start);
            }

            thread.Priority = priority;
            thread.IsBackground = isBackground;
            thread.Name = name;

            Watchdog.ThreadWatchdogInfo twi = new Watchdog.ThreadWatchdogInfo(thread, timeout, name)
            {
                AlarmIfTimeout = alarmIfTimeout,
                AlarmMethod = alarmMethod
            };

            Watchdog.AddThread(twi, name, log);

            thread.Start();

            return thread;
        }

        public static Thread StartThread(
            ThreadStart start, string name, ThreadPriority priority, int stackSize = -1, bool suspendflow = true)
        {
            Thread thread;
            if (suspendflow)
            {
                using (ExecutionContext.SuppressFlow())
                {
                    if (stackSize > 0)
                        thread = new Thread(start, stackSize);
                    else
                        thread = new Thread(start);
                }
            }
            else
            {
                if (stackSize > 0)
                    thread = new Thread(start, stackSize);
                else
                    thread = new Thread(start);
            }

            thread.Priority = priority;
            thread.IsBackground = true;
            thread.Name = name;

            Watchdog.ThreadWatchdogInfo twi = new Watchdog.ThreadWatchdogInfo(thread, Watchdog.DEFAULT_WATCHDOG_TIMEOUT_MS, name)
            {
                AlarmIfTimeout = false,
                AlarmMethod = null
            };

            Watchdog.AddThread(twi, name, false);

            thread.Start();

            return thread;
        }

        /// <summary>
        /// Run the callback in a new thread immediately.  If the thread exits with an exception log it but do
        /// not propogate it.
        /// </summary>
        /// <param name="callback">Code for the thread to execute.</param>
        /// <param name="obj">Object to pass to the thread.</param>
        /// <param name="name">Name of the thread</param>
        public static void RunInThread(WaitCallback callback, object obj, string name, bool log = false)
        {
            if (Util.FireAndForgetMethod == FireAndForgetMethod.RegressionTest)
            {
                Culture.SetCurrentCulture();
                callback(obj);
                return;
            }

            ThreadStart ts = new ThreadStart(delegate()
            {
                try
                {
                    Culture.SetCurrentCulture();
                    callback(obj);
                }
                catch (Exception e)
                {
                    m_log.Error(string.Format("[WATCHDOG]: Exception in thread {0}.", name), e);
                }
                finally
                {
                    try
                    {
                        Watchdog.RemoveThread(log: false);
                    }
                    catch { }
                }
            });

            StartThread(ts, name, false, log);
        }

        /// <summary>
        /// Run the callback via a threadpool thread.
        /// </summary>
        /// <remarks>
        /// Such jobs may run after some delay but must always complete.
        /// </remarks>
        /// <param name="callback"></param>
        /// <param name="obj"></param>
        /// <param name="name">The name of the job.  This is used in monitoring and debugging.</param>
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void RunInThreadPool(WaitCallback callback, object obj, string name, bool timeout = true)
        {
            Util.FireAndForget(callback, obj, name, timeout);
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void RunInThreadPool(WaitCallback callback, string name, bool timeout = true)
        {
            Util.FireAndForget(callback, null, name, timeout);
        }

        private static void HandleControlCommand(string module, string[] args)
        {
            //            if (SceneManager.Instance.CurrentScene != null && SceneManager.Instance.CurrentScene != m_udpServer.Scene)
            //                return;

            if (args.Length < 3)
            {
                MainConsole.Instance.Output("Usage: debug jobengine <stop|start|status|log>");
                return;
            }

            string subCommand = args[2];

            if (subCommand == "stop")
            {
                JobEngine.Stop();
                MainConsole.Instance.Output("Stopped job engine.");
            }
            else if (subCommand == "start")
            {
                JobEngine.Start();
                MainConsole.Instance.Output("Started job engine.");
            }
            else if (subCommand == "status")
            {
                MainConsole.Instance.Output("Job engine running: {0}", JobEngine.IsRunning);
                MainConsole.Instance.Output(
                    "Jobs waiting: {0}", JobEngine.IsRunning ? JobEngine.JobsWaiting.ToString() : "n/a");
                MainConsole.Instance.Output("Log Level: {0}", JobEngine.LogLevel);
            }
            else if (subCommand == "log")
            {
                if (args.Length < 4)
                {
                    MainConsole.Instance.Output("Usage: debug jobengine log <level>");
                    return;
                }

                //                int logLevel;
                int logLevel = int.Parse(args[3]);
                //                if (ConsoleUtil.TryParseConsoleInt(MainConsole.Instance, args[4], out logLevel))
                //                {
                JobEngine.LogLevel = logLevel;
                MainConsole.Instance.Output("Set debug log level to {0}", JobEngine.LogLevel);
                //                }
            }
            else
            {
                MainConsole.Instance.Output("Unrecognized job engine subcommand {0}", subCommand);
            }
        }
    }
}