service.go

// +build windows

package main

import (
	"fmt"
	"log"
	"os"
	"path/filepath"
	"strings"
	"time"

	"golang.org/x/sys/windows/svc"
	"golang.org/x/sys/windows/svc/debug"
	"golang.org/x/sys/windows/svc/eventlog"
	"golang.org/x/sys/windows/svc/mgr"
)

const (
	svcName     = "edca"
	svcDispName = "Elite Dangerous Cockpit Agent"
	svcDesc     = "Feeds the cockpit information and keeps its state in sync with the game state"
)

var elog debug.Log

type monitorService struct{}

func (m *monitorService) Execute(args []string, r <-chan svc.ChangeRequest, changes chan<- svc.Status) (ssec bool, errno uint32) {
	const cmdsAccepted = svc.AcceptStop | svc.AcceptShutdown
	changes <- svc.Status{State: svc.StartPending}
	shorttick := time.Tick(20 * time.Millisecond)
	longtick := time.Tick(10 * time.Second)
	tick := shorttick
	changes <- svc.Status{State: svc.Running, Accepts: cmdsAccepted}
	elog.Info(1, strings.Join(args, "-"))
loop:
	for {
		select {
		case <-tick:
			err := checkStatusAndUpdate()
			if err != nil {
				switch err.(type) {
				case *errorNoSerialConnection:
					tick = longtick
				default:
					elog.Error(1, err.Error())
					break loop
				}
			} else {
				tick = shorttick
			}
		case c := <-r:
			switch c.Cmd {
			case svc.Interrogate:
				changes <- c.CurrentStatus
				// Testing deadlock from https://code.google.com/p/winsvc/issues/detail?id=4
				time.Sleep(100 * time.Millisecond)
				changes <- c.CurrentStatus
			case svc.Stop, svc.Shutdown:
				break loop
			default:
				elog.Error(1, fmt.Sprintf("unexpected control request #%d", c))
			}
		}
	}
	changes <- svc.Status{State: svc.StopPending}
	return
}

func usage(errmsg string) {
	fmt.Fprintf(os.Stderr,
		"%s\n\n"+
			"usage: %s <command>\n"+
			"       where <command> is one of\n"+
			"       configure, install, remove, debug, start, or stop.\n",
		errmsg, os.Args[0])
	os.Exit(2)
}

func main() {
	isIntSess, err := svc.IsAnInteractiveSession()
	if err != nil {
		log.Fatalf("failed to determine if we are running in an interactive session: %v", err)
	}
	if !isIntSess {
		runService(svcName, false)
		return
	}

	if len(os.Args) < 2 {
		usage("no command specified")
	}

	cmd := strings.ToLower(os.Args[1])
	switch cmd {
	case "debug":
		runService(svcName, true)
		return
	case "configure":
		err = interactiveConfig()
	case "install":
		err = installService(svcName, svcDispName, svcDesc)
	case "remove":
		err = removeService(svcName)
	case "start":
		err = startService(svcName)
	case "stop":
		err = controlService(svcName, svc.Stop, svc.Stopped)
	case "pause":
		err = controlService(svcName, svc.Pause, svc.Paused)
	case "continue":
		err = controlService(svcName, svc.Continue, svc.Running)
	default:
		usage(fmt.Sprintf("invalid command %s", cmd))
	}
	if err != nil {
		log.Fatalf("failed to %s %s: %v", cmd, svcName, err)
	}
	return
}

func runService(name string, isDebug bool) {
	var err error
	if isDebug {
		elog = debug.New(name)
	} else {
		elog, err = eventlog.Open(name)
		if err != nil {
			return
		}
	}
	defer elog.Close()

	elog.Info(1, fmt.Sprintf("starting %s service", name))
	run := svc.Run
	if isDebug {
		run = debug.Run
	}
	err = run(name, &monitorService{})
	if err != nil {
		elog.Error(1, fmt.Sprintf("%s service failed: %v", name, err))
		return
	}
	elog.Info(1, fmt.Sprintf("%s service stopped", name))
}

func startService(name string) error {
	m, err := mgr.Connect()
	if err != nil {
		return err
	}
	defer m.Disconnect()
	s, err := m.OpenService(name)
	if err != nil {
		return fmt.Errorf("could not access service: %v", err)
	}
	defer s.Close()
	err = s.Start("is", "manual-started")
	if err != nil {
		return fmt.Errorf("could not start service: %v", err)
	}
	return nil
}

func controlService(name string, c svc.Cmd, to svc.State) error {
	m, err := mgr.Connect()
	if err != nil {
		return err
	}
	defer m.Disconnect()
	s, err := m.OpenService(name)
	if err != nil {
		return fmt.Errorf("could not access service: %v", err)
	}
	defer s.Close()
	status, err := s.Control(c)
	if err != nil {
		return fmt.Errorf("could not send control=%d: %v", c, err)
	}
	timeout := time.Now().Add(10 * time.Second)
	for status.State != to {
		if timeout.Before(time.Now()) {
			return fmt.Errorf("timeout waiting for service to go to state=%d", to)
		}
		time.Sleep(300 * time.Millisecond)
		status, err = s.Query()
		if err != nil {
			return fmt.Errorf("could not retrieve service status: %v", err)
		}
	}
	return nil
}

func exePath() (string, error) {
	prog := os.Args[0]
	p, err := filepath.Abs(prog)
	if err != nil {
		return "", err
	}
	fi, err := os.Stat(p)
	if err == nil {
		if !fi.Mode().IsDir() {
			return p, nil
		}
		err = fmt.Errorf("%s is directory", p)
	}
	if filepath.Ext(p) == "" {
		p += ".exe"
		fi, err := os.Stat(p)
		if err == nil {
			if !fi.Mode().IsDir() {
				return p, nil
			}
			err = fmt.Errorf("%s is directory", p)
		}
	}
	return "", err
}

func installService(name, dispName, desc string) error {
	exepath, err := exePath()
	if err != nil {
		return err
	}

	_, err = os.Stat(configPath())
	if err != nil {
		usage("not configured; run " + os.Args[0] + " configure")
	}

	m, err := mgr.Connect()
	if err != nil {
		return err
	}
	defer m.Disconnect()
	s, err := m.OpenService(name)
	if err == nil {
		s.Close()
		return fmt.Errorf("service %s already exists", name)
	}
	s, err = m.CreateService(name, exepath, mgr.Config{DisplayName: dispName, Description: desc}, "is", "auto-started")
	if err != nil {
		return err
	}
	defer s.Close()
	err = eventlog.InstallAsEventCreate(name, eventlog.Error|eventlog.Warning|eventlog.Info)
	if err != nil {
		s.Delete()
		return fmt.Errorf("SetupEventLogSource() failed: %s", err)
	}
	return nil
}

func removeService(name string) error {
	m, err := mgr.Connect()
	if err != nil {
		return err
	}
	defer m.Disconnect()
	s, err := m.OpenService(name)
	if err != nil {
		return fmt.Errorf("service %s is not installed", name)
	}
	defer s.Close()
	err = s.Delete()
	if err != nil {
		return err
	}
	err = eventlog.Remove(name)
	if err != nil {
		return fmt.Errorf("RemoveEventLogSource() failed: %s", err)
	}
	return nil
}