/// \brief To create a basic Windows Service in C++.
/// \see https://www.codeproject.com/Articles/499465/Simple-Windows-Service-in-Cplusplus

#include <Windows.h>
#include <tchar.h>
#include <string>

#include "libipc/ipc.h"

SERVICE_STATUS        g_ServiceStatus = {0};
SERVICE_STATUS_HANDLE g_StatusHandle = NULL;
HANDLE                g_ServiceStopEvent = INVALID_HANDLE_VALUE;

VOID WINAPI ServiceMain (DWORD argc, LPTSTR *argv);
VOID WINAPI ServiceCtrlHandler (DWORD);
DWORD WINAPI ServiceWorkerThread (LPVOID lpParam);

#define SERVICE_NAME  _T("My Sample Service")

int _tmain (int argc, TCHAR *argv[]) {
    OutputDebugString(_T("My Sample Service: Main: Entry"));

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

    if (StartServiceCtrlDispatcher (ServiceTable) == FALSE) {
        OutputDebugString(_T("My Sample Service: Main: StartServiceCtrlDispatcher returned error"));
        return GetLastError ();
    }

    OutputDebugString(_T("My Sample Service: Main: Exit"));
    return 0;
}

VOID WINAPI ServiceMain (DWORD argc, LPTSTR *argv) {
    DWORD Status = E_FAIL;

    OutputDebugString(_T("My Sample Service: ServiceMain: Entry"));

    g_StatusHandle = RegisterServiceCtrlHandler (SERVICE_NAME, ServiceCtrlHandler);

    if (g_StatusHandle == NULL) {
        OutputDebugString(_T("My Sample Service: ServiceMain: RegisterServiceCtrlHandler returned error"));
        goto EXIT;
    }

    // Tell the service controller we are starting
    ZeroMemory (&g_ServiceStatus, sizeof (g_ServiceStatus));
    g_ServiceStatus.dwServiceType = SERVICE_WIN32_OWN_PROCESS;
    g_ServiceStatus.dwControlsAccepted = 0;
    g_ServiceStatus.dwCurrentState = SERVICE_START_PENDING;
    g_ServiceStatus.dwWin32ExitCode = 0;
    g_ServiceStatus.dwServiceSpecificExitCode = 0;
    g_ServiceStatus.dwCheckPoint = 0;

    if (SetServiceStatus (g_StatusHandle, &g_ServiceStatus) == FALSE) {
        OutputDebugString(_T("My Sample Service: ServiceMain: SetServiceStatus returned error"));
    }

    /* 
     * Perform tasks neccesary to start the service here
     */
    OutputDebugString(_T("My Sample Service: ServiceMain: Performing Service Start Operations"));

    // Create stop event to wait on later.
    g_ServiceStopEvent = CreateEvent (NULL, TRUE, FALSE, NULL);
    if (g_ServiceStopEvent == NULL) {
        OutputDebugString(_T("My Sample Service: ServiceMain: CreateEvent(g_ServiceStopEvent) returned error"));

        g_ServiceStatus.dwControlsAccepted = 0;
        g_ServiceStatus.dwCurrentState = SERVICE_STOPPED;
        g_ServiceStatus.dwWin32ExitCode = GetLastError();
        g_ServiceStatus.dwCheckPoint = 1;

        if (SetServiceStatus (g_StatusHandle, &g_ServiceStatus) == FALSE) {
            OutputDebugString(_T("My Sample Service: ServiceMain: SetServiceStatus returned error"));
        }
        goto EXIT; 
    }    

    // Tell the service controller we are started
    g_ServiceStatus.dwControlsAccepted = SERVICE_ACCEPT_STOP;
    g_ServiceStatus.dwCurrentState = SERVICE_RUNNING;
    g_ServiceStatus.dwWin32ExitCode = 0;
    g_ServiceStatus.dwCheckPoint = 0;

    if (SetServiceStatus (g_StatusHandle, &g_ServiceStatus) == FALSE) {
        OutputDebugString(_T("My Sample Service: ServiceMain: SetServiceStatus returned error"));
    }

    // Start the thread that will perform the main task of the service
    HANDLE hThread = CreateThread (NULL, 0, ServiceWorkerThread, NULL, 0, NULL);

    OutputDebugString(_T("My Sample Service: ServiceMain: Waiting for Worker Thread to complete"));

    // Wait until our worker thread exits effectively signaling that the service needs to stop
    WaitForSingleObject (hThread, INFINITE);
    
    OutputDebugString(_T("My Sample Service: ServiceMain: Worker Thread Stop Event signaled"));
    
    
    /* 
     * Perform any cleanup tasks
     */
    OutputDebugString(_T("My Sample Service: ServiceMain: Performing Cleanup Operations"));

    CloseHandle (g_ServiceStopEvent);

    g_ServiceStatus.dwControlsAccepted = 0;
    g_ServiceStatus.dwCurrentState = SERVICE_STOPPED;
    g_ServiceStatus.dwWin32ExitCode = 0;
    g_ServiceStatus.dwCheckPoint = 3;

    if (SetServiceStatus (g_StatusHandle, &g_ServiceStatus) == FALSE) {
        OutputDebugString(_T("My Sample Service: ServiceMain: SetServiceStatus returned error"));
    }
    
EXIT:
    OutputDebugString(_T("My Sample Service: ServiceMain: Exit"));
    return;
}

VOID WINAPI ServiceCtrlHandler (DWORD CtrlCode) {
    OutputDebugString(_T("My Sample Service: ServiceCtrlHandler: Entry"));

    switch (CtrlCode) {
    case SERVICE_CONTROL_STOP :

        OutputDebugString(_T("My Sample Service: ServiceCtrlHandler: SERVICE_CONTROL_STOP Request"));

        if (g_ServiceStatus.dwCurrentState != SERVICE_RUNNING)
           break;

        /* 
         * Perform tasks neccesary to stop the service here 
         */
        
        g_ServiceStatus.dwControlsAccepted = 0;
        g_ServiceStatus.dwCurrentState = SERVICE_STOP_PENDING;
        g_ServiceStatus.dwWin32ExitCode = 0;
        g_ServiceStatus.dwCheckPoint = 4;

        if (SetServiceStatus (g_StatusHandle, &g_ServiceStatus) == FALSE) {
            OutputDebugString(_T("My Sample Service: ServiceCtrlHandler: SetServiceStatus returned error"));
        }

        // This will signal the worker thread to start shutting down
        SetEvent (g_ServiceStopEvent);

        break;

    default:
        break;
    }

    OutputDebugString(_T("My Sample Service: ServiceCtrlHandler: Exit"));
}

DWORD WINAPI ServiceWorkerThread (LPVOID lpParam) {
    OutputDebugString(_T("My Sample Service: ServiceWorkerThread: Entry"));
    ipc::channel ipc_r{ipc::prefix{"Global\\"}, "service ipc r", ipc::sender};
    ipc::channel ipc_w{ipc::prefix{"Global\\"}, "service ipc w", ipc::receiver};

    //  Periodically check if the service has been requested to stop
    while (WaitForSingleObject(g_ServiceStopEvent, 0) != WAIT_OBJECT_0) {        
        /* 
         * Perform main service function here
         */
        if (!ipc_r.send("Hello, World!")) {
            OutputDebugString(_T("My Sample Service: send failed."));
        }
        else {
            OutputDebugString(_T("My Sample Service: send [Hello, World!]"));
            auto msg = ipc_w.recv(1000);
            if (msg.empty()) {
                OutputDebugString(_T("My Sample Service: recv error"));
            } else {
                OutputDebugStringA((std::string{"My Sample Service: recv ["} + msg.get<char const *>() + "]").c_str());
            }
        }
        Sleep(3000);
    }

    OutputDebugString(_T("My Sample Service: ServiceWorkerThread: Exit"));

    return ERROR_SUCCESS;
}