package tui

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

type Signal byte

const (
	SIGNULL Signal = 0
	SIGINT  Signal = 1
	SIGTERM Signal = 2
	SIGTSTP Signal = 3
	SIGHUP  Signal = 4
	SIGTTIN Signal = 5
	SIGTTOU Signal = 6
	SIGUSR1 Signal = 7
	SIGUSR2 Signal = 8
	SIGALRM Signal = 9
)

func as_signal(which os.Signal) Signal {
	switch which {
	case os.Interrupt:
		return SIGINT
	case syscall.SIGTERM:
		return SIGTERM
	case syscall.SIGTSTP:
		return SIGTSTP
	case syscall.SIGHUP:
		return SIGHUP
	case syscall.SIGTTIN:
		return SIGTTIN
	case syscall.SIGTTOU:
		return SIGTTOU
	case syscall.SIGUSR1:
		return SIGUSR1
	case syscall.SIGUSR2:
		return SIGUSR2
	case syscall.SIGALRM:
		return SIGALRM
	default:
		return SIGNULL
	}
}

const zero_go_signal = syscall.Signal(0)

func as_go_signal(which Signal) os.Signal {
	switch which {
	case SIGINT:
		return os.Interrupt
	case SIGTERM:
		return syscall.SIGTERM
	case SIGTSTP:
		return syscall.SIGTSTP
	case SIGHUP:
		return syscall.SIGHUP
	case SIGTTIN:
		return syscall.SIGTTIN
	case SIGTTOU:
		return syscall.SIGTTOU
	case SIGUSR1:
		return syscall.SIGUSR1
	case SIGUSR2:
		return syscall.SIGUSR2
	case SIGALRM:
		return syscall.SIGALRM
	default:
		return zero_go_signal
	}
}

func write_signal(dest *os.File, which os.Signal) error {
	b := make([]byte, 1)
	b[0] = byte(as_signal(which))
	if b[0] == 0 {
		return nil
	}
	_, err := dest.Write(b)
	return err
}

func notify_signals(c chan os.Signal, signals ...Signal) func() {
	s := make([]os.Signal, len(signals))
	for i, x := range signals {
		g := as_go_signal(x)
		if g != zero_go_signal {
			s[i] = g
		}
	}
	signal.Notify(c, s...)
	return func() { signal.Reset(s...) }
}