//go:build !windows

package version

import (
	"errors"
	"os"
	"os/exec"
	"syscall"

	"golang.org/x/sys/unix"
)

func processAlive(pid int) bool {
	if pid <= 0 {
		return false
	}
	err := unix.Kill(pid, 0)
	return err == nil || errors.Is(err, unix.EPERM)
}

func processMatches(pid int, expectedToken string) bool {
	if !processAlive(pid) {
		return false
	}
	if expectedToken == "" {
		// Backward compatibility for journals written before process identity
		// tokens were introduced.
		return true
	}
	actualToken, err := processIdentityToken(pid)
	return err == nil && actualToken == expectedToken
}

// configureIdentityCommand gives the identity probe its own process group and
// replaces CommandContext's cancellation hook so descendants cannot survive a
// timed-out or cancelled probe.
func configureIdentityCommand(cmd *exec.Cmd) {
	cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
	cmd.Cancel = func() error {
		if cmd.Process == nil {
			return os.ErrProcessDone
		}
		err := syscall.Kill(-cmd.Process.Pid, syscall.SIGKILL)
		if errors.Is(err, syscall.ESRCH) {
			return os.ErrProcessDone
		}
		return err
	}
}