//go:build unix

package runner

import (
	"os"
	"os/exec"
	"os/signal"
	"syscall"
)

// startSignalForwarding installs handlers for SIGINT, SIGTERM, and SIGHUP and
// forwards them to proc. The returned stop function removes the handlers and
// drains the channel; callers should defer-call it.
//
// We deliberately do NOT exit on signal receipt — the child gets the signal
// and owns its shutdown lifecycle; we just relay and keep waiting for it.
func startSignalForwarding(proc *os.Process) func() {
	ch := make(chan os.Signal, 4)
	signal.Notify(ch, syscall.SIGINT, syscall.SIGTERM, syscall.SIGHUP)

	done := make(chan struct{})
	go func() {
		for {
			select {
			case sig := <-ch:
				_ = proc.Signal(sig)
			case <-done:
				return
			}
		}
	}()

	return func() {
		signal.Stop(ch)
		close(done)
	}
}

// extractSignal pulls the signal from an *exec.ExitError on Unix.
// If the error wasn't a signal termination, ok is false.
func extractSignal(exitErr *exec.ExitError) (syscall.Signal, bool) {
	ws, ok := exitErr.Sys().(syscall.WaitStatus)
	if !ok {
		return 0, false
	}
	if !ws.Signaled() {
		return 0, false
	}
	return ws.Signal(), true
}