using System;
using System.Diagnostics;
using System.ServiceProcess;
using AppServerWatchDogService.Enums;
using System.Runtime.InteropServices;
using System.Threading;
using System.IO.Pipes;
using System.IO;
using System.Timers;
using System.Threading.Tasks;

namespace AppServerWatchDogService
{
    // sc create AppServerWatchDogService binPath="E:\WorkSpace_cSharp\SafeDispatch_v4\AppServerWatchDogService\bin\Debug\AppServerWatchDogService.exe" start= auto

    public enum ServiceState
    {
        SERVICE_STOPPED = 0x00000001,
        SERVICE_START_PENDING = 0x00000002,
        SERVICE_STOP_PENDING = 0x00000003,
        SERVICE_RUNNING = 0x00000004,
        SERVICE_CONTINUE_PENDING = 0x00000005,
        SERVICE_PAUSE_PENDING = 0x00000006,
        SERVICE_PAUSED = 0x00000007,
    }

    [StructLayout(LayoutKind.Sequential)]
    public struct ServiceStatus
    {
        public int dwServiceType;
        public ServiceState dwCurrentState;
        public int dwControlsAccepted;
        public int dwWin32ExitCode;
        public int dwServiceSpecificExitCode;
        public int dwCheckPoint;
        public int dwWaitHint;
    };

    public partial class AppServerWatchDogService : ServiceBase
    {

        #region Config Values
        public static Boolean restartTCPService = false;
        public static Boolean monitorAppServer = false;

        #endregion
        private static bool isRunning = false;
        private static int smallNrOfWorkersCount = 0;
        public static int tries = 0;

        public static String serviceLocation = System.Reflection.Assembly.GetExecutingAssembly().Location;
        public static String serviceFolder = serviceLocation.Substring(0, serviceLocation.LastIndexOf('\\'));
        public static String appServerFolder = serviceFolder.Substring(0, serviceFolder.LastIndexOf('\\')) + "\\AppServer";
        public static String batFile = appServerFolder + "\\SafeDispatch-StartUp.bat";

        [DllImport("advapi32.dll", SetLastError = true)]
        private static extern bool SetServiceStatus(IntPtr handle, ref ServiceStatus serviceStatus);

        public AppServerWatchDogService()
        {
            InitializeComponent();
            eventLog1 = new EventLog();
            if (!EventLog.SourceExists("MySource"))
            {
                EventLog.CreateEventSource("MySource", "MyNewLog");
            }
            eventLog1.Source = "MySource";
            eventLog1.Log = "MyNewLog";
        }

        protected override void OnStart(string[] args)
        {
            // Update the service state to Start Pending.  
            ServiceStatus serviceStatus = new ServiceStatus();
            serviceStatus.dwCurrentState = ServiceState.SERVICE_START_PENDING;
            serviceStatus.dwWaitHint = 100000;
            SetServiceStatus(this.ServiceHandle, ref serviceStatus);

            System.Timers.Timer timer = new System.Timers.Timer();
            timer.Interval = 60000; // 60 seconds
            timer.Elapsed += new ElapsedEventHandler(this.OnTimer);
            timer.Start();

            WriteEventLog(Program.COMPANY, "WatchDog Started!!!", EventLogEntryType.Information, (Int32)EventId.EVENT_WATCHDOG);

           
            // Update the service state to Running.  
            serviceStatus.dwCurrentState = ServiceState.SERVICE_RUNNING;
            SetServiceStatus(this.ServiceHandle, ref serviceStatus);

            if (!ConfigHelper.HasRestartTCPService || !ConfigHelper.HasTCPServiceName)
            {
                WriteEventLog(Program.COMPANY, "AppSettings does not contain key  \"restartTCPService\" or \"serviceName\"", EventLogEntryType.Error, (int)EventId.EVENT_WATCHDOG);
            }
            else
            {
                restartTCPService = ConfigHelper.RestartTCPService;
            }

            if (!ConfigHelper.HasAppServerMonitor)
            {
                WriteEventLog(Program.COMPANY, "AppSettings does not contain key  \"monitorAppServer\"", EventLogEntryType.Error, (int)EventId.EVENT_WATCHDOG);
            }
            else
            {
                monitorAppServer = ConfigHelper.AppServerMonitor;
            }

            if (!File.Exists(batFile) && ConfigHelper.AppServerMonitor)
                CreateBatFile(batFile);

            if (restartTCPService)
                StartTCPThread();

            if (monitorAppServer)
                StartWatchDog();
        }

        protected override void OnStop()
        {
            if (File.Exists(batFile))
                File.Delete(batFile);
            isRunning = false;
            WriteEventLog(Program.COMPANY, "WatchDog STOPPED!!!", EventLogEntryType.Warning, (Int32)EventId.EVENT_WATCHDOG);

        }

        public void OnTimer(object sender, ElapsedEventArgs args)
        {
            // TODO: Insert monitoring activities here.
        }

        public void StartTCPThread()
        {
            Task.Factory.StartNew(() =>
            {
                RestartTCPClient.Main();
            });
        }

        public void StartWatchDog()
        {
            isRunning = true;
            Thread t = new Thread(WatchDogWorker);
            t.IsBackground = true;
            t.Start();
        }

        private static void WatchDogWorker()
        {
            isRunning = true;
            int count = 0;


            int timeoutBeforeStartingToMonitorInSec = ConfigHelper.TimeoutBeforeStartingToMonitorSec;
            // wait 10 seconds before starting to check for AppServer
            while (count++ < timeoutBeforeStartingToMonitorInSec * 10)
            {
                if (!isRunning)
                    return;

                Thread.Sleep(100);
            }

            count = 0;

            while (isRunning)
            {
                Thread.Sleep(100);

                if (count++ > 30 && isRunning)
                {
                    using (NamedPipeClientStream pipeClient =
                            new NamedPipeClientStream(".", "appServerPipe", PipeDirection.InOut))
                    {
                        try
                        {
                            // Connect to the pipe or wait until the pipe is available.
                            //WriteEventLog(Program.COMPANY, "Attempting to connect to pipe...", EventLogEntryType.Information, (Int32)EventId.EVENT_WATCHDOG);

                            pipeClient.Connect(1000);

                            //WriteEventLog(Program.COMPANY, "Connected to pipe.", EventLogEntryType.Information, (Int32)EventId.EVENT_WATCHDOG);

                            WriteEventLog(Program.COMPANY, String.Format("There are currently {0} pipe server instances open.", pipeClient.NumberOfServerInstances),
                                EventLogEntryType.Information, (Int32)EventId.EVENT_WATCHDOG);
                            using (StreamReader sr = new StreamReader(pipeClient))
                            {
                                // Display the read text to the console
                                string temp;
                                while ((temp = sr.ReadLine()) != null)
                                {
                                    //WriteEventLog(Program.COMPANY, String.Format("Received from server: {0}", temp), EventLogEntryType.Information, (Int32)EventId.EVENT_WATCHDOG);


                                    String[] split = temp.Split(new char[] { '|' }, StringSplitOptions.RemoveEmptyEntries);
                                    int numberOfWorkersQueueCount = 0;
                                    if (split.Length > 0)
                                        Int32.TryParse(split[0], out numberOfWorkersQueueCount);

                                    if (numberOfWorkersQueueCount < 200)
                                        smallNrOfWorkersCount++;

                                    // restart app server if for the last 5 iterations the number of gps workers was small
                                    if (smallNrOfWorkersCount >= 5)
                                    {
                                        WriteEventLog(Program.COMPANY, String.Format("WatchDog detected slow GPS queue polling : " + smallNrOfWorkersCount),
                                            EventLogEntryType.Warning, (Int32)EventId.EVENT_WATCHDOG);

                                        RestartAppServer();
                                    }
                                }
                            }
                        }
                        catch (Exception ex)
                        {
                            tries++;
                            WriteEventLog(Program.COMPANY, String.Format("WatchDog unable to connect to namedpipe!!! Tries numeber: " + tries.ToString()
                                + Environment.NewLine + ex.ToString()), EventLogEntryType.Error, (Int32)EventId.EVENT_WATCHDOG);
                            if (tries == ConfigHelper.NumberOfMissingPingsWithAppServerAllowed)
                            {
                                RestartAppServer();
                                tries = 0;
                            }
                        }
                    }
                    count = 0;
                }

            }
        }

        private static void RestartAppServer()
        {
            try
            {
                // the name of the application to launch;
                // to launch an application using the full command path simply escape
                // the path with quotes, for example to launch firefox.exe:
                //      String applicationName = "\"C:\\Program Files (x86)\\Mozilla Firefox\\firefox.exe\"";
                String applicationName = batFile;

                // launch the application
                ApplicationLoader.PROCESS_INFORMATION procInfo;
                ApplicationLoader.StartProcessAndBypassUAC(applicationName, out procInfo);
                
                WriteEventLog(Program.COMPANY, "AppServer restarted using: " + batFile.ToString(), EventLogEntryType.Information, (Int32)EventId.EVENT_WATCHDOG);
            }
            catch (Exception ex)
            {
                WriteEventLog(Program.COMPANY, appServerFolder + "\\" + "AppServer.exe", EventLogEntryType.Error, (Int32)EventId.EVENT_WATCHDOG);
                WriteEventLog(Program.COMPANY, ex.ToString(), EventLogEntryType.Error, (Int32)EventId.EVENT_WATCHDOG);
            }

        }

        public static void WriteEventLog(String source, String content, EventLogEntryType type, Int32 eventId)
        {
            try
            {
                if (!EventLog.SourceExists(source))
                    EventLog.CreateEventSource(source, "Application");

                EventLog.WriteEntry(source, content, type, eventId);
            }
            catch (Exception ex)
            {
                throw ex;
            }
        }


        private void CreateBatFile(string batLocation)
        {
            try
            {
                using (StreamWriter sw = new StreamWriter(batLocation))
                {
                    sw.WriteLine("@ECHO off");
                    sw.WriteLine("echo Starting AppServer");
                    sw.WriteLine($"cd /d \"{appServerFolder}\"");
                    sw.WriteLine("start AppServer.exe -c -l");
                }
                WriteEventLog(Program.COMPANY, ".bat file created at: " + batFile.ToString(), EventLogEntryType.Information, (Int32)EventId.EVENT_WATCHDOG);
            }
            catch (Exception ex)
            {
                WriteEventLog(Program.COMPANY, "Failed to create .bat file because: " + Environment.NewLine + ex.ToString(),
                    EventLogEntryType.Error, (Int32)EventId.EVENT_WATCHDOG);
            }
        }
    }
}