// copied from "sigs.k8s.io/controller-runtime/pkg/manager/signals"
package signals

import (
	"context"
	"fmt"
	"os"
	"os/signal"
	"syscall"
)

var onlyOneSignalHandler = make(chan struct{})

var shutdownSignals = []os.Signal{os.Interrupt, syscall.SIGTERM}

// SetupSignalHandler registers for SIGTERM and SIGINT. A context is returned
// which is canceled on one of these signals. If a second signal is caught, the program
// is terminated with exit code 1.
func SetupSignalHandler() context.Context {
	close(onlyOneSignalHandler) // panics when called twice

	ctx, cancel := context.WithCancelCause(context.Background())

	c := make(chan os.Signal, 2)
	signal.Notify(c, shutdownSignals...)
	go func() {
		s := <-c
		cancel(fmt.Errorf("received a signal %s", s.String()))
		<-c
		os.Exit(1) // second signal. Exit directly.
	}()

	return ctx
}