//go:build windows

package windowsservice

import (
	"context"
	"errors"
	"fmt"
	"syscall"
	"time"

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

func connect() (*mgr.Mgr, error) {
	return mgr.Connect()
}

func installNative(spec InstallSpec) error {
	if err := spec.Validate(); err != nil {
		return err
	}
	manager, err := connect()
	if err != nil {
		return fmt.Errorf("connect to service control manager: %w", err)
	}
	defer manager.Disconnect()
	startup := uint32(mgr.StartAutomatic)
	if spec.Startup == StartupManual {
		startup = mgr.StartManual
	}
	configuration := mgr.Config{
		ServiceType:      windows.SERVICE_WIN32_OWN_PROCESS,
		StartType:        startup,
		ErrorControl:     mgr.ErrorNormal,
		DisplayName:      DisplayName,
		Description:      Description,
		ServiceStartName: "LocalSystem",
	}
	service, openErr := manager.OpenService(Name)
	if errors.Is(openErr, windows.ERROR_SERVICE_DOES_NOT_EXIST) {
		service, err = manager.CreateService(Name, spec.ExecutablePath, configuration, "--service", "--config", spec.ConfigPath)
		if err != nil {
			return fmt.Errorf("create %s service: %w", Name, err)
		}
	} else if openErr != nil {
		return fmt.Errorf("open %s service: %w", Name, openErr)
	} else {
		configuration, err = service.Config()
		if err != nil {
			return fmt.Errorf("query %s service configuration: %w", Name, err)
		}
		configuration.ServiceType = windows.SERVICE_WIN32_OWN_PROCESS
		configuration.StartType = startup
		configuration.ErrorControl = mgr.ErrorNormal
		configuration.BinaryPathName = serviceImage(spec)
		configuration.DisplayName = DisplayName
		configuration.Description = Description
		configuration.ServiceStartName = "LocalSystem"
		if err := service.UpdateConfig(configuration); err != nil {
			return fmt.Errorf("update %s service configuration: %w", Name, err)
		}
	}
	defer service.Close()
	if err := service.Start(); err != nil && !errors.Is(err, windows.ERROR_SERVICE_ALREADY_RUNNING) {
		return fmt.Errorf("start %s service: %w", Name, err)
	}
	return nil
}

func serviceImage(spec InstallSpec) string {
	return syscall.EscapeArg(spec.ExecutablePath) + " --service --config " + syscall.EscapeArg(spec.ConfigPath)
}

func uninstallNative() error {
	manager, err := connect()
	if err != nil {
		return fmt.Errorf("connect to service control manager: %w", err)
	}
	defer manager.Disconnect()
	service, err := manager.OpenService(Name)
	if errors.Is(err, windows.ERROR_SERVICE_DOES_NOT_EXIST) {
		return nil
	}
	if err != nil {
		return fmt.Errorf("open %s service: %w", Name, err)
	}
	defer service.Close()
	if err := stopService(service, 30*time.Second); err != nil {
		return err
	}
	if err := service.Delete(); err != nil && !errors.Is(err, windows.ERROR_SERVICE_MARKED_FOR_DELETE) {
		return fmt.Errorf("delete %s service: %w", Name, err)
	}
	return nil
}

func startNative() error {
	manager, err := connect()
	if err != nil {
		return err
	}
	defer manager.Disconnect()
	service, err := manager.OpenService(Name)
	if errors.Is(err, windows.ERROR_SERVICE_DOES_NOT_EXIST) {
		return fmt.Errorf("%s service is not installed", Name)
	}
	if err != nil {
		return err
	}
	defer service.Close()
	if err := service.Start(); err != nil && !errors.Is(err, windows.ERROR_SERVICE_ALREADY_RUNNING) {
		return err
	}
	return nil
}

func stopNative(timeoutSeconds uint32) error {
	manager, err := connect()
	if err != nil {
		return err
	}
	defer manager.Disconnect()
	service, err := manager.OpenService(Name)
	if errors.Is(err, windows.ERROR_SERVICE_DOES_NOT_EXIST) {
		return nil
	}
	if err != nil {
		return err
	}
	defer service.Close()
	timeout := 30 * time.Second
	if timeoutSeconds > 0 {
		timeout = time.Duration(timeoutSeconds) * time.Second
	}
	return stopService(service, timeout)
}

func stopService(service *mgr.Service, timeout time.Duration) error {
	status, err := service.Query()
	if err != nil {
		return fmt.Errorf("query %s service: %w", Name, err)
	}
	if status.State == svc.Stopped {
		return nil
	}
	if _, err := service.Control(svc.Stop); err != nil && !errors.Is(err, windows.ERROR_SERVICE_NOT_ACTIVE) {
		return fmt.Errorf("stop %s service: %w", Name, err)
	}
	deadline := time.Now().Add(timeout)
	for {
		status, err = service.Query()
		if err != nil {
			return fmt.Errorf("query %s service while stopping: %w", Name, err)
		}
		if status.State == svc.Stopped {
			return nil
		}
		if time.Now().After(deadline) {
			return fmt.Errorf("timed out stopping %s service", Name)
		}
		time.Sleep(100 * time.Millisecond)
	}
}

type handler struct {
	run func(context.Context) error
}

func (serviceHandler handler) Execute(_ []string, changes <-chan svc.ChangeRequest, status chan<- svc.Status) (bool, uint32) {
	if serviceHandler.run == nil {
		return false, 1
	}
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	status <- svc.Status{State: svc.StartPending, WaitHint: 10_000}
	done := make(chan error, 1)
	go func() { done <- serviceHandler.run(ctx) }()
	status <- svc.Status{State: svc.Running, Accepts: svc.AcceptStop | svc.AcceptShutdown}
	for {
		select {
		case request := <-changes:
			if request.Cmd == svc.Stop || request.Cmd == svc.Shutdown {
				status <- svc.Status{State: svc.StopPending, WaitHint: 30_000}
				cancel()
				err := <-done
				if err != nil {
					return true, 1
				}
				status <- svc.Status{State: svc.Stopped}
				return false, 0
			}
		case err := <-done:
			if err != nil {
				return true, 1
			}
			status <- svc.Status{State: svc.Stopped}
			return false, 0
		}
	}
}

func runNative(run func(context.Context) error) error {
	return svc.Run(Name, handler{run: run})
}