/***************************************************************************
 *                                  Main.cs
 *                            -------------------
 *   begin                : May 1, 2002
 *   copyright            : (C) The RunUO Software Team
 *   email                : info@runuo.com
 *
 *   $Id$
 *
 ***************************************************************************/

/***************************************************************************
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 ***************************************************************************/

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Reflection;
using System.Runtime;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Server.Json;
using Server.Network;

namespace Server
{
  public static class Core
  {
    private static bool m_Crashed;
    private static Thread timerThread;
    private static string m_BaseDirectory;
    private static string m_ExePath;

    private static bool m_Profiling;
    private static DateTime m_ProfileStart;
    private static TimeSpan m_ProfileTime;

    /*
     * DateTime.Now and DateTime.UtcNow are based on actual system clock time.
     * The resolution is acceptable but large clock jumps are possible and cause issues.
     * GetTickCount and GetTickCount64 have poor resolution.
     * Stopwatch.GetTimestamp() (QueryPerformanceCounter) is high resolution, but
     * somewhat expensive to call because of its difference to DateTime.Now,
     * which is why Stopwatch has been used to verify HRT before calling GetTimestamp(),
     * enabling the usage of DateTime.UtcNow instead.
     */

    private static readonly double m_HighFrequency = 1000.0 / Stopwatch.Frequency;
    private static readonly double m_LowFrequency = 1000.0 / TimeSpan.TicksPerSecond;

    internal static ConsoleEventHandler m_ConsoleEventHandler;

    private static int m_CycleIndex = 1;
    private static readonly float[] m_CyclesPerSecond = new float[100];

    private static readonly AutoResetEvent m_Signal = new AutoResetEvent(true);

    private static int m_ItemCount, m_MobileCount;

    private static readonly Type[] m_SerialTypeArray = { typeof(Serial) };

    public static bool Profiling
    {
      get => m_Profiling;
      set
      {
        if (m_Profiling == value)
          return;

        m_Profiling = value;

        if (m_ProfileStart > DateTime.MinValue)
          m_ProfileTime += DateTime.UtcNow - m_ProfileStart;

        m_ProfileStart = m_Profiling ? DateTime.UtcNow : DateTime.MinValue;
      }
    }

    public static TimeSpan ProfileTime
    {
      get
      {
        if (m_ProfileStart > DateTime.MinValue)
          return m_ProfileTime + (DateTime.UtcNow - m_ProfileStart);

        return m_ProfileTime;
      }
    }

    internal static bool HaltOnWarning { get; private set; }

    public static Assembly Assembly { get; set; }

    public static Version Version => Assembly.GetName().Version;
    public static Process Process { get; private set; }

    public static Thread Thread { get; private set; }

    public static long TickCount => (long)Ticks;

    public static double Ticks =>
      Stopwatch.IsHighResolution
        ? Stopwatch.GetTimestamp() * m_HighFrequency
        : DateTime.UtcNow.Ticks * m_LowFrequency;

    public static bool MultiProcessor { get; private set; }

    public static int ProcessorCount { get; private set; }

    public static bool IsWindows = RuntimeInformation.IsOSPlatform(OSPlatform.Windows);
    public static bool IsDarwin = RuntimeInformation.IsOSPlatform(OSPlatform.OSX);
    public static bool IsFreeBSD = RuntimeInformation.IsOSPlatform(OSPlatform.FreeBSD);
    public static bool IsLinux = RuntimeInformation.IsOSPlatform(OSPlatform.Linux) || IsFreeBSD;
    public static bool Unix = IsDarwin || IsFreeBSD || IsLinux;

    public static string ExePath => m_ExePath ??= Assembly.Location;

    public static string BaseDirectory
    {
      get
      {
        if (m_BaseDirectory == null)
          try
          {
            m_BaseDirectory = ExePath;

            if (m_BaseDirectory.Length > 0)
              m_BaseDirectory = Path.GetDirectoryName(m_BaseDirectory);
          }
          catch
          {
            m_BaseDirectory = "";
          }

        return m_BaseDirectory;
      }
    }

    public static bool Closing { get; private set; }

    public static float CyclesPerSecond => m_CyclesPerSecond[(m_CycleIndex - 1) % m_CyclesPerSecond.Length];

    public static float AverageCPS => m_CyclesPerSecond.Take(m_CycleIndex).Average();

    public static string Arguments
    {
      get
      {
        var sb = new StringBuilder();

        if (m_Profiling)
          Utility.Separate(sb, "-profile", " ");

        if (HaltOnWarning)
          Utility.Separate(sb, "-haltonwarning", " ");

        return sb.ToString();
      }
    }

    public static int GlobalUpdateRange { get; set; } = 18;

    public static int GlobalMaxUpdateRange { get; set; } = 24;

    public static int ScriptItems => m_ItemCount;
    public static int ScriptMobiles => m_MobileCount;

    public static string FindDataFile(string path, bool throwNotFound = true, bool warnNotFound = false)
    {
      string fullPath = null;

      foreach (var p in ServerConfiguration.DataDirectories)
      {
        fullPath = Path.Combine(p, path);

        if (File.Exists(fullPath))
          break;

        fullPath = null;
      }

      if (fullPath == null && (throwNotFound || warnNotFound))
      {
        Utility.PushColor(ConsoleColor.Red);
        Console.WriteLine($"Data: {path} was not found");
        Console.WriteLine("Make sure modernuo.json is properly configured");
        Utility.PopColor();
        if (throwNotFound)
          throw new FileNotFoundException($"Data: {path} was not found");
      }

      return fullPath;
    }

    private static void CurrentDomain_UnhandledException(object sender, UnhandledExceptionEventArgs e)
    {
      Console.WriteLine(e.IsTerminating ? "Error:" : "Warning:");
      Console.WriteLine(e.ExceptionObject);

      if (e.IsTerminating)
      {
        m_Crashed = true;

        var close = false;

        try
        {
          var args = new ServerCrashedEventArgs(e.ExceptionObject as Exception);

          EventSink.InvokeServerCrashed(args);

          close = args.Close;
        }
        catch
        {
          // ignored
        }

        if (!close)
        {
          try
          {
            // Close all listeners
          }
          catch
          {
            // ignored
          }

          Console.WriteLine("This exception is fatal, press return to exit");
          Console.ReadLine();
        }

        Kill();
      }
    }

    private static bool OnConsoleEvent(ConsoleEventType type)
    {
      if (World.Saving || type == ConsoleEventType.CTRL_LOGOFF_EVENT)
        return true;

      Kill(); // Kill -> HandleClosed will handle waiting for the completion of flushing to disk

      return true;
    }

    private static void CurrentDomain_ProcessExit(object sender, EventArgs e)
    {
      HandleClosed();
    }

    public static void Kill(bool restart = false)
    {
      HandleClosed();

      if (restart)
        Process.Start(ExePath, Arguments);

      Process.Kill();
    }

    private static void HandleClosed()
    {
      if (Closing)
        return;

      Closing = true;

      Console.Write("Exiting...");

      World.WaitForWriteCompletion();

      if (!m_Crashed)
        EventSink.InvokeShutdown();

      Timer.TimerThread.Set();

      Console.WriteLine("done");
    }

    public static void Set()
    {
      m_Signal.Set();
    }

    private static string assembliesConfiguration = "Configuration/assemblies.json";

    public static void Main(string[] args)
    {
      AppDomain.CurrentDomain.UnhandledException += CurrentDomain_UnhandledException;
      AppDomain.CurrentDomain.ProcessExit += CurrentDomain_ProcessExit;

      foreach (var a in args)
        if (Insensitive.Equals(a, "-profile"))
          Profiling = true;
        else if (Insensitive.Equals(a, "-haltonwarning"))
          HaltOnWarning = true;

      Thread = Thread.CurrentThread;
      Process = Process.GetCurrentProcess();
      Assembly = Assembly.GetEntryAssembly();

      if (Assembly == null)
        throw new Exception("Core: Assembly entry is missing.");

      if (Thread != null)
        Thread.Name = "Core Thread";

      if (BaseDirectory.Length > 0)
        Directory.SetCurrentDirectory(BaseDirectory);

      var ver = Assembly.GetName().Version ?? new Version();

      Utility.PushColor(ConsoleColor.Green);
      // Added to help future code support on forums, as a 'check' people can ask for to it see if they recompiled core or not
      Console.WriteLine("ModernUO - [https://github.com/modernuo/modernuo] Version {0}.{1}.{2}.{3}", ver.Major,
        ver.Minor, ver.Build,
        ver.Revision);
      Console.WriteLine("Core: Running on {0}\n", RuntimeInformation.FrameworkDescription);
      Utility.PopColor();

      var ttObj = new Timer.TimerThread();
      timerThread = new Thread(ttObj.TimerMain)
      {
        Name = "Timer Thread"
      };

      var s = Arguments;

      if (s.Length > 0)
        Console.WriteLine("Core: Running with arguments: {0}", s);

      ProcessorCount = Environment.ProcessorCount;

      if (ProcessorCount > 1)
        MultiProcessor = true;

      if (MultiProcessor)
        Console.WriteLine("Core: Optimizing for {0} processor{1}", ProcessorCount, ProcessorCount == 1 ? "" : "s");

      if (IsWindows)
      {
        m_ConsoleEventHandler = OnConsoleEvent;
        UnsafeNativeMethods.SetConsoleCtrlHandler(m_ConsoleEventHandler, true);
      }

      if (GCSettings.IsServerGC)
        Console.WriteLine("Core: Server garbage collection mode enabled");

      Console.WriteLine("Core: High resolution timing ({0})",
        Stopwatch.IsHighResolution ? "Supported" : "Unsupported");

      ServerConfiguration.Load();

      // Load UOContent.dll
      string[] assemblyFiles = JsonConfig.Deserialize<List<string>>(
        Path.Join(BaseDirectory, assembliesConfiguration)
      ).Select(t => Path.Join(BaseDirectory, "Assemblies", t)).ToArray();
      AssemblyHandler.LoadScripts(assemblyFiles);

      VerifySerialization();

      AssemblyHandler.Invoke("Configure");

      RegionLoader.LoadRegions();
      World.Load();

      AssemblyHandler.Invoke("Initialize");

      AssemblyHandler.Invoke("RegisterListeners");

      timerThread.Start();

      foreach (var m in Map.AllMaps)
        m.Tiles.Force();

      EventSink.InvokeServerStarted();

      // Start net socket server
      var host = TcpServer.CreateWebHostBuilder().Build();
      var life = host.Services.GetRequiredService<IHostApplicationLifetime>();
      life.ApplicationStopping.Register(() => { Kill(); });

      host.Run();
    }

    public static void RunEventLoop(IMessagePumpService messagePumpService)
    {
      try
      {
        var last = TickCount;

        const int sampleInterval = 100;
        const float ticksPerSecond = 1000.0f * sampleInterval;

        long sample = 0;

        while (!Closing)
        {
          m_Signal.WaitOne();

          Task.WaitAll(
            Task.Run(Mobile.ProcessDeltaQueue),
            Task.Run(Item.ProcessDeltaQueue));

          Timer.Slice();
          messagePumpService.DoWork();

          NetState.ProcessDisposedQueue();

          if (sample++ % sampleInterval != 0)
            continue;

          var now = TickCount;
          m_CyclesPerSecond[m_CycleIndex++ % m_CyclesPerSecond.Length] = ticksPerSecond / (now - last);
          last = now;
        }
      }
      catch (Exception e)
      {
        CurrentDomain_UnhandledException(null, new UnhandledExceptionEventArgs(e, true));
      }
    }

    public static void VerifySerialization()
    {
      m_ItemCount = 0;
      m_MobileCount = 0;

      var ca = Assembly.GetCallingAssembly();

      VerifySerialization(ca);

      foreach (var a in AssemblyHandler.Assemblies)
        if (a != ca) VerifySerialization(a);
    }

    private static void VerifyType(Type t)
    {
      var isItem = t.IsSubclassOf(typeof(Item));

      if (!isItem && !t.IsSubclassOf(typeof(Mobile))) return;

      if (isItem)
        Interlocked.Increment(ref m_ItemCount);
      else
        Interlocked.Increment(ref m_MobileCount);

      StringBuilder warningSb = null;

      try
      {
        if (t.GetConstructor(m_SerialTypeArray) == null)
        {
          warningSb = new StringBuilder();
          warningSb.AppendLine("       - No serialization constructor");
        }

        if (
          t.GetMethod(
            "Serialize",
            BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.DeclaredOnly) ==
          null)
        {
          warningSb ??= new StringBuilder();
          warningSb.AppendLine("       - No Serialize() method");
        }

        if (t.GetMethod(
              "Deserialize",
              BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.DeclaredOnly) ==
            null)
        {
          warningSb ??= new StringBuilder();
          warningSb.AppendLine("       - No Deserialize() method");
        }

        if (warningSb?.Length > 0) Console.WriteLine("Warning: {0}\n{1}", t, warningSb);
      }
      catch
      {
        Console.WriteLine("Warning: Exception in serialization verification of type {0}", t);
      }
    }

    private static void VerifySerialization(Assembly a)
    {
      if (a != null) Parallel.ForEach(a.GetTypes(), VerifyType);
    }

    internal enum ConsoleEventType
    {
      CTRL_C_EVENT,
      CTRL_BREAK_EVENT,
      CTRL_CLOSE_EVENT,
      CTRL_LOGOFF_EVENT = 5,
      CTRL_SHUTDOWN_EVENT
    }

    internal delegate bool ConsoleEventHandler(ConsoleEventType type);

    internal class UnsafeNativeMethods
    {
      [DllImport("Kernel32")]
      internal static extern bool SetConsoleCtrlHandler(ConsoleEventHandler callback, bool add);
    }

    public static Expansion Expansion { get; set; }

    public static bool T2A => Expansion >= Expansion.T2A;

    public static bool UOR => Expansion >= Expansion.UOR;

    public static bool UOTD => Expansion >= Expansion.UOTD;

    public static bool LBR => Expansion >= Expansion.LBR;

    public static bool AOS => Expansion >= Expansion.AOS;

    public static bool SE => Expansion >= Expansion.SE;

    public static bool ML => Expansion >= Expansion.ML;

    public static bool SA => Expansion >= Expansion.SA;

    public static bool HS => Expansion >= Expansion.HS;

    public static bool TOL => Expansion >= Expansion.TOL;

    public static bool EJ => Expansion >= Expansion.EJ;
  }
}