// \file service.cpp
//
// Copyright (C) 2014 MicroNeil Research Corporation.
//
// This program is part of the MicroNeil Research Open Library Project. For
// more information go to http://www.microneil.com/OpenLibrary/index.html
//
// 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.
//
// This program is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
// more details.
//
// You should have received a copy of the GNU General Public License along with
// this program; if not, write to the Free Software Foundation, Inc., 59 Temple
// Place, Suite 330, Boston, MA 02111-1307 USA
//==============================================================================

#ifdef WIN32

#include <windows.h>
#include <tchar.h>
#include <strsafe.h>

#else

#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <signal.h>

#endif

#ifdef DEBUG_LOG_FILE
#include <fstream>
#endif

#include <cstdio>
#include <cstdlib>
#include <thread>

#include "service.hpp"

#ifdef WIN32

// Application main entry point for Windows.
int _tmain(int argc, TCHAR *argv[]) {

  CodeDweller::Service &service = CodeDweller::Service::getInstance();

  return service.main(argc, (char **) argv);

}

// Service entry point for Windows.
VOID WINAPI ServiceMain(DWORD argc, LPTSTR *argv) {

  CodeDweller::Service &service = CodeDweller::Service::getInstance();

  return service.serviceMain(argc, argv);

}

/// Control message handler for Windows.
VOID WINAPI ServiceCtrlHandler(DWORD message) {

#ifdef DEBUG_LOG_FILE
  std::ofstream logStream;

  logStream.open(DEBUG_LOG_FILE, std::fstream::app);
  logStream << "ServiceCtrlHandler.  message:  " << message
	    << ".  Calling processCtrlMessage" << std::endl;
  logStream.close();
#endif

  CodeDweller::Service &service = CodeDweller::Service::getInstance();

  service.processCtrlMessage(message);

#ifdef DEBUG_LOG_FILE
  logStream.open(DEBUG_LOG_FILE, std::fstream::app);
  logStream << "ServiceCtrlHandler.  Done." << std::endl;
  logStream.close();
#endif

}

#else

// Main program for *nix daemon.
int main(int argc, char *argv[]) {

  CodeDweller::Service &service = CodeDweller::Service::getInstance();

  return service.main(argc, argv);

}

#endif

namespace CodeDweller {

  std::mutex Service::objectMutex;

  std::vector<std::string> Service::cmdLineArgs;

  bool Service::pauseReceived = false;

  bool Service::resumeReceived = false;

  bool Service::stopReceived = false;

  std::vector<Service::Callback *> Service::pauseCallbacks;

  std::vector<Service::Callback *> Service::resumeCallbacks;

  std::vector<Service::Callback *> Service::stopCallbacks;

  Service::Service() {
  }

  Service &Service::getInstance() {
    std::lock_guard<std::mutex> scopeMutex(objectMutex);
    static Service service;
    return service;
  }

  int Service::main(int argc, char *argv[]) {

    // Under Windows, only arg 0 is passed.  Under *nix, all arguments
    // are passed.
    loadArguments(argc, (char **) argv);

#ifdef DEBUG_LOG_FILE
    std::ofstream logStream;

    logStream.open(DEBUG_LOG_FILE, std::fstream::app);
    logStream << "main.  argc:  " << argc << std::endl;
    for (int i = 0; i < argc; i++) {
      logStream << "arg " << i << ":  '" << argv[i] << "'" << std::endl;
    }
    logStream.close();
#endif

#ifdef WIN32

    SERVICE_TABLE_ENTRY ServiceTable[] = {
      {"", (LPSERVICE_MAIN_FUNCTION) ServiceMain},
      {NULL, NULL}
    };

    if (StartServiceCtrlDispatcher(ServiceTable) == FALSE) {
      return GetLastError();
    }

    return 0;

#else

    pid_t pid;

    // Fork the process.
    pid = fork();
    if (pid < 0) {
      perror("Error from first fork");
      return(EXIT_FAILURE);
    }

    // Terminate the parent.
    if (pid > 0) {
      return(EXIT_SUCCESS);
    }

    // This is the child.  Become the session leader.
    if (setsid() < 0) {
      perror("Error from setsid");
      return(EXIT_FAILURE);
    }

    // Fork again.
    pid = fork();
    if (pid < 0) {
      perror("Error from second fork");
      return(EXIT_FAILURE);
    }

    // Terminate the parent.
    if (pid > 0) {
      return(EXIT_SUCCESS);
    }

    // Set default file permissions.  This call always succeeds.
    umask(0);

    // Disassociate the process from the default directory of the
    // grandparent.
    if (chdir("/") != 0) {
      perror("Error from chdir");
      return(EXIT_FAILURE);
    }

    // Initialize the set of signals to wait for.
    if (sigemptyset(&signalSet) != 0) {
      perror("Error from sigemptyset");
      return(EXIT_FAILURE);
    }

    if ((sigaddset(&signalSet, SIGTSTP) != 0) ||
	(sigaddset(&signalSet, SIGCONT) != 0) ||
	(sigaddset(&signalSet, SIGHUP) != 0) ||
	(sigaddset(&signalSet, SIGTERM) != 0)) {
      perror("Error from sigaddset");
      return(EXIT_FAILURE);
    }

    // Block the signals.
    if (sigprocmask(SIG_BLOCK, &signalSet, NULL) != 0) {
      perror("Error from sigprocmask");
      return(EXIT_FAILURE);
    }

    // Close all open file descriptors.
    for (int fd = 2; fd >= 0; fd--) {
      if (close(fd) != 0) {
	// There is no controlling terminal to send any message to.
	return(EXIT_FAILURE);
      }
    }

    // Connect standard I/O to the null device.
    int fd;

    // stdin.
    fd = open("/dev/null", O_RDONLY);
    if (fd < 0) {
      return(EXIT_FAILURE);
    }

    // stdout.
    fd = open("/dev/null", O_WRONLY);
    if (fd < 0) {
      return(EXIT_FAILURE);
    }
    // stderr.
    fd = open("/dev/null", O_WRONLY);
    if (fd < 0) {
      return(EXIT_FAILURE);
    }

    // Start the thread to process messages.
    std::thread messageThread(&Service::processMessages, this);

    // Run the service.
    int status;
    status = run();

    // Send a Stop message so that messageThread exits.
    pthread_kill(messageThread.native_handle(), SIGTERM);

    messageThread.join();

    return(status);
#endif
  }

#ifdef WIN32

  void Service::serviceMain(DWORD argc, LPTSTR *argv) {

    // Arg 0 contains the service name; skip it.  The remaining
    // arguments contain the command-line arguments, excluding the
    // executable name; append them to the object's argument list.
    loadArguments(argc - 1, (char **) argv + 1);

    DWORD Status = E_FAIL;

    // Register the service control handler with the SCM.
    serviceStatusHandle =
      RegisterServiceCtrlHandler("", ServiceCtrlHandler);

#ifdef DEBUG_LOG_FILE
    std::ofstream logStream;

    logStream.open(DEBUG_LOG_FILE, std::fstream::app);
    logStream << "ServiceMain.  argc:  " << argc << std::endl;
    for (DWORD i = 0; i < argc; i++) {
      logStream << "arg " << i << ":  '" << argv[i] << "'" << std::endl;
    }
    logStream << "  serviceStatusHandle == NULL:  " <<
      (NULL == serviceStatusHandle) << std::endl;
    logStream.close();
#endif

    if (serviceStatusHandle == NULL) {
      return;
    }

    ZeroMemory(&serviceStatus, sizeof(serviceStatus));
    serviceStatus.dwServiceType = SERVICE_WIN32_OWN_PROCESS;
    serviceStatus.dwControlsAccepted = 0;
    serviceStatus.dwCurrentState = SERVICE_START_PENDING;
    serviceStatus.dwWin32ExitCode = NO_ERROR;
    serviceStatus.dwServiceSpecificExitCode = 0;
    serviceStatus.dwCheckPoint = 0;
    serviceStatus.dwWaitHint = 5000;

    (void) SetServiceStatus(serviceStatusHandle, &serviceStatus);

    // Tell the service controller that the service has started.
    serviceStatus.dwControlsAccepted =
      SERVICE_ACCEPT_STOP |
      SERVICE_ACCEPT_PAUSE_CONTINUE;
    serviceStatus.dwCurrentState = SERVICE_RUNNING;
    serviceStatus.dwWin32ExitCode = 0;
    serviceStatus.dwCheckPoint = 0;
    (void) SetServiceStatus(serviceStatusHandle, &serviceStatus);

#ifdef DEBUG_LOG_FILE
    logStream.open(DEBUG_LOG_FILE, std::fstream::app);
    logStream << "Starting application thread." << std::endl;
    logStream.close();
#endif

    // Start the application thread.
    int status;

    status = run();

    // Change status to stopped.
    serviceStatus.dwControlsAccepted = 0;
    serviceStatus.dwCurrentState = SERVICE_STOPPED;
    serviceStatus.dwWin32ExitCode = NO_ERROR;
    serviceStatus.dwCheckPoint = 0;
    (void) SetServiceStatus(serviceStatusHandle, &serviceStatus);

#ifdef DEBUG_LOG_FILE
    logStream.open(DEBUG_LOG_FILE, std::fstream::app);
    logStream << "Exiting." << std::endl;
    logStream.close();
#endif

    return;

  }

#endif

  void Service::loadArguments(int argc, char *argv[]) {

    for (int i = 0; i < argc; i++) {
      cmdLineArgs.push_back(argv[i]);
    }

  }

  const std::vector<std::string> &Service::arguments() {
    return cmdLineArgs;
  }

  void Service::onPauseCall(Callback &pauseFunctor) {
    std::lock_guard<std::mutex> scopeMutex(objectMutex);
    pauseCallbacks.push_back(&pauseFunctor);
  }

  void Service::onResumeCall(Callback &resumeFunctor) {
    std::lock_guard<std::mutex> scopeMutex(objectMutex);
    resumeCallbacks.push_back(&resumeFunctor);
  }

  void Service::onStopCall(Callback &stopFunctor) {
    std::lock_guard<std::mutex> scopeMutex(objectMutex);
    stopCallbacks.push_back(&stopFunctor);
  }

  bool Service::receivedPause() {
    return (pauseReceived);
  }

  bool Service::receivedResume() {
    return (resumeReceived);
  }

  bool Service::receivedStop() {
    return (stopReceived);
  }

  void Service::clearReceivedPause() {
    pauseReceived = false;
  }

  void Service::clearReceivedResume() {
    resumeReceived = false;
  }

  void Service::clearReceivedStop() {
    stopReceived = false;
  }

#ifdef WIN32

  void Service::processCtrlMessage(DWORD message) {

#ifdef DEBUG_LOG_FILE
    std::ofstream logStream;
    logStream.open(DEBUG_LOG_FILE, std::fstream::app);
    logStream << "processCtrlMessage.  message:  " << message << std::endl;
    logStream.close();
#endif

    switch (message) {

    case SERVICE_CONTROL_PAUSE:

#ifdef DEBUG_LOG_FILE
      logStream.open(DEBUG_LOG_FILE, std::fstream::app);
      logStream << "processCtrlMessage.  Received Pause" << std::endl;
      logStream.close();
#endif

      serviceStatus.dwControlsAccepted = 0;
      serviceStatus.dwCurrentState = SERVICE_PAUSE_PENDING;
      serviceStatus.dwWin32ExitCode = NO_ERROR;
      serviceStatus.dwCheckPoint = 1;
      serviceStatus.dwWaitHint = 5000;
      (void) SetServiceStatus(serviceStatusHandle, &serviceStatus);

      pauseReceived = true;

      for (auto callback : pauseCallbacks) {
	(*callback)();
      }

      serviceStatus.dwControlsAccepted =
	SERVICE_ACCEPT_STOP |
	SERVICE_ACCEPT_PAUSE_CONTINUE;
      serviceStatus.dwCurrentState = SERVICE_PAUSED;
      serviceStatus.dwWin32ExitCode = NO_ERROR;
      serviceStatus.dwCheckPoint = 0;
      (void) SetServiceStatus(serviceStatusHandle, &serviceStatus);

      break;

    case SERVICE_CONTROL_CONTINUE:

#ifdef DEBUG_LOG_FILE
      logStream.open(DEBUG_LOG_FILE, std::fstream::app);
      logStream << "processCtrlMessage.  Received Resume" << std::endl;
      logStream.close();
#endif

      serviceStatus.dwControlsAccepted = 0;
      serviceStatus.dwCurrentState = SERVICE_CONTINUE_PENDING;
      serviceStatus.dwWin32ExitCode = NO_ERROR;
      serviceStatus.dwCheckPoint = 1;
      serviceStatus.dwWaitHint = 5000;
      (void) SetServiceStatus(serviceStatusHandle, &serviceStatus);

      resumeReceived = true;

      for (auto callback : resumeCallbacks) {
	(*callback)();
      }

      serviceStatus.dwControlsAccepted =
	SERVICE_ACCEPT_STOP |
	SERVICE_ACCEPT_PAUSE_CONTINUE;
      serviceStatus.dwCurrentState = SERVICE_RUNNING;
      serviceStatus.dwWin32ExitCode = NO_ERROR;
      serviceStatus.dwCheckPoint = 0;
      (void) SetServiceStatus(serviceStatusHandle, &serviceStatus);

      break;

    case SERVICE_CONTROL_STOP:

#ifdef DEBUG_LOG_FILE
      logStream.open(DEBUG_LOG_FILE, std::fstream::app);
      logStream << "processCtrlMessage.  Received STOP" << std::endl;
      logStream.close();
#endif

      serviceStatus.dwControlsAccepted = 0;
      serviceStatus.dwCurrentState = SERVICE_STOP_PENDING;
      serviceStatus.dwWin32ExitCode = NO_ERROR;
      serviceStatus.dwCheckPoint = 1;
      serviceStatus.dwWaitHint = 5000;
      (void) SetServiceStatus(serviceStatusHandle, &serviceStatus);

      stopReceived = true;

      for (auto callback : stopCallbacks) {
	(*callback)();
      }

      break;

    default:
      break;
    }

  }

#else

  void Service::processMessages() {

    int sigNum;
    int status;

    while (true) {

      // Wait for a signal.
      status = sigwait(&signalSet, &sigNum);
      if (0 != status) {
	perror("Error from sigwait");
	// TODO:  Implement recovery.
	;
      }

      // Process the message.
      switch (sigNum) {

      case SIGTSTP:
	pauseReceived = true;

	for (auto callback : pauseCallbacks) {
	  (*callback)();
	}

	break;

      case SIGCONT:
	resumeReceived = true;

	for (auto callback : resumeCallbacks) {
	  (*callback)();
	}

	break;

      case SIGTERM:
	stopReceived = true;

	for (auto callback : stopCallbacks) {
	  (*callback)();
	}

	// Exit.
	return;

	break;

      default:
	;

      } // switch.

    } // while.

  }

#endif
}