using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Topshelf;
using log4net;
using System.Net.Sockets;
using System.Net;
using System.Collections.Concurrent;
using System.Diagnostics;
using System.IO.Pipes;

namespace kmProcessServer;

internal class ServiceMain : ServiceControl
{
  ILog appLog = LogManager.GetLogger(Program.AppName);
  ConcurrentBag<Task> tasks = new();
  ConcurrentBag<MdlProcess> ChildProcesses = new();

  public bool Start(HostControl hostControl)
  {
    appLog.Info(string.Format("Service successfully started."));
    tasks.Add(Task.Run(() => { StartTasks(); }));
    return true;
  } //Start

  public bool Stop(HostControl hostControl)
  {
    Program.isExiting = true;
    Task.WaitAll(tasks.ToArray());
    tasks.Clear();
    appLog.Debug("++ Service shutdown successful.");
    return true;
  } //Stop

  void StartTasks()
  {
    var rn = new Random();

    try
    {
      foreach (var f0 in Directory.GetFiles(Program.AppPath + "Procs", "*.exe"))
      {
        var px = new MdlProcess()
        {
          ProgramToRun = f0,
          ExecutableName = Path.GetFileName(f0)
        };
        var si = new ProcessStartInfo()
        {
          FileName = px.ProgramToRun,
          Verb = "OPEN",
          WorkingDirectory = Path.GetDirectoryName(f0),
          RedirectStandardError = true,
          UseShellExecute = false
        };
        px.theProcess = new Process() { StartInfo = si };
        px.theProcess.Start();
        px.StartTime = DateTimeOffset.Now;
        px.IPCChannel = string.Format("kmProcess_IPCChannel.{0}", px.theProcess.Id);
        ChildProcesses.Add(px);
        appLog.DebugFormat("++ Launched Process '{0}' having PID of {1}", px.ExecutableName, px.theProcess.Id);
      }
    }
    catch (Exception ex)
    {
      appLog.Error(ex);
    }

    while (!Program.isExiting)
    {
      Thread.Sleep(rn.Next(900, 3000));
    }

    // First, try to stop them all gracefully...
    foreach (var px in ChildProcesses)
    {
      appLog.DebugFormat("Sending request to shut down process '{0}'...", px.ExecutableName);
      try
      {
        using (var ch = new NamedPipeClientStream(".", px.IPCChannel, PipeDirection.Out))
        {
          if (ch.ConnectAsync().Wait(3000))
          {
            using (var w = new StreamWriter(ch))
            {
              w.WriteLine("EXIT_NOW");
              w.Flush();
            }
          }
        }
      }
      catch (Exception ex)
      {
        appLog.Error(ex);
      }
      Thread.Sleep(100);
    }

    // Anyone still running? Use the hammer.
    foreach (var px in ChildProcesses)
    {
      if (px.theProcess != null)
      {
        if (!px.theProcess.HasExited)
          Thread.Sleep(5000); //Give it a little time to gracefully exit
        if (!px.theProcess.HasExited)
        {
          try { px.theProcess.Kill(); }
          catch { }
        }
        try { px.theProcess.Dispose(); }
        catch { }
      }
    }
    ChildProcesses.Clear();
  }

  #region "Private Models and Such"
  class MdlProcess
  {
    public string ProgramToRun { get; set; } = string.Empty;
    public string ExecutableName { get; set; } = string.Empty;
    public Process? theProcess { get; set; } = null;
    public DateTimeOffset StartTime { get; set; } = DateTimeOffset.Now;
    /// <summary>
    /// Used for interprocess communications
    /// </summary>
    public string IPCChannel { get; set; } = string.Empty;
  }
  #endregion
}