package main

import (
	"os"

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

// hideTyping turns a terminal's echo off while a secret is typed at it, and gives back what restores it. On
// anything that is not a terminal (a pipe, a file) it does nothing.
func hideTyping(f *os.File) func() {
	fd := int(f.Fd())
	before, err := unix.IoctlGetTermios(fd, unix.TCGETS)
	if err != nil {
		return func() {}
	}
	hidden := *before
	hidden.Lflag &^= unix.ECHO
	if err := unix.IoctlSetTermios(fd, unix.TCSETS, &hidden); err != nil {
		return func() {}
	}
	return func() {
		_ = unix.IoctlSetTermios(fd, unix.TCSETS, before)
		_, _ = os.Stderr.WriteString("\n")
	}
}