// +build linux

package node

import (
	"os/exec"
	"sync"

	"github.com/pkg/errors"
)

var (
	systemdHasCollectModeOnce sync.Once
	systemdHasCollectMode     bool
	systemdHasCollectModeErr  error

	systemdHasAllowedCPUsOnce sync.Once
	systemdHasAllowedCPUs     bool
	systemdHasAllowedCPUsErr  error
)

func SystemdHasCollectMode() bool {
	systemdHasCollectModeOnce.Do(func() {
		systemdHasCollectMode, systemdHasCollectModeErr = systemdSupportsProperty("CollectMode")
	})
	return systemdHasCollectMode
}

func SystemdHasAllowedCPUs() bool {
	systemdHasAllowedCPUsOnce.Do(func() {
		systemdHasAllowedCPUs, systemdHasAllowedCPUsErr = systemdSupportsProperty("AllowedCPUs")
	})
	return systemdHasAllowedCPUs
}

// systemdSupportsProperty checks whether systemd supports a property
// It returns an error if it does not.
func systemdSupportsProperty(property string) (bool, error) {
	output, err := exec.Command("systemctl", "show", "-p", property, "systemd").Output()
	if err != nil {
		return false, errors.Wrapf(err, "check systemd %s", property)
	}
	if len(output) == 0 {
		return false, nil
	}
	return true, nil
}
