//go:build aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd || solaris || zos

package mnemonic

import (
	"bufio"
	"errors"
	"fmt"
	"io"
	"os"

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

// readWithoutEcho reads one line from the terminal on standard input
// with echo turned off. The line ends at a newline or at the end of
// input (Ctrl-D). The terminal is set as term.ReadPassword sets it;
// ReadPassword itself is not used here because it never sees the end
// of input and goes on waiting.
func readWithoutEcho() (string, error) {
	fd := int(os.Stdin.Fd())

	settings, err := unix.IoctlGetTermios(fd, ioctlReadTermios)
	if err != nil {
		return "", fmt.Errorf("reading the terminal settings: %w", err)
	}

	hidden := *settings
	hidden.Lflag &^= unix.ECHO
	hidden.Lflag |= unix.ICANON | unix.ISIG
	hidden.Iflag |= unix.ICRNL

	err = unix.IoctlSetTermios(fd, ioctlWriteTermios, &hidden)
	if err != nil {
		return "", fmt.Errorf("turning echo off: %w", err)
	}

	defer func() { _ = unix.IoctlSetTermios(fd, ioctlWriteTermios, settings) }()

	// With ICANON set, a read from the terminal returns at most one
	// line, so the buffer takes nothing past the newline.
	typed, err := bufio.NewReader(os.Stdin).ReadString('\n')
	if errors.Is(err, io.EOF) {
		return typed, nil
	}

	return typed, err
}