// SPDX-FileCopyrightText: 2026 Echolot contributors
// SPDX-License-Identifier: GPL-3.0-or-later

//go:build linux

package system

import (
	"os"
	"syscall"
	"unsafe"
)

// DisableEcho turns off terminal echo while a password is typed, returning a function that puts
// the terminal back. Both are best-effort: when stdin is a pipe (the automation case) there is
// no terminal to change and nothing to restore.
func DisableEcho(f *os.File) (func(), error) {
	fd := f.Fd()
	var t syscall.Termios
	if _, _, errno := syscall.Syscall6(syscall.SYS_IOCTL, fd,
		syscall.TCGETS, uintptr(unsafe.Pointer(&t)), 0, 0, 0); errno != 0 {
		return nil, errno // not a terminal; nothing to do
	}
	original := t
	t.Lflag &^= syscall.ECHO
	if _, _, errno := syscall.Syscall6(syscall.SYS_IOCTL, fd,
		syscall.TCSETS, uintptr(unsafe.Pointer(&t)), 0, 0, 0); errno != 0 {
		return nil, errno
	}
	return func() {
		_, _, _ = syscall.Syscall6(syscall.SYS_IOCTL, fd,
			syscall.TCSETS, uintptr(unsafe.Pointer(&original)), 0, 0, 0)
	}, nil
}