package main

import (
	"fmt"
	"os"
	"os/exec"
	"strings"
)

// yesno asks a y/n question with a default. Reads a single keypress.
func yesno(prompt string, def bool) bool {
	suffix := " y/N ? "
	if def {
		suffix = " Y/n ? "
	}
	ans := strings.ToLower(strings.TrimSpace(getkey(prompt + suffix)))
	if ans == "" {
		return def
	}
	return ans == "y" || ans == "yes"
}

// getkey reads a single keypress from the terminal without echo. It reads a
// single byte directly from stdin; readline is not reading at this point (we
// are inside command execution), so there is no reader to desync with.
func getkey(prompt string) string {
	fmt.Print(prompt)
	stty("-icanon", "-echo")
	var buf [1]byte
	n, err := os.Stdin.Read(buf[:])
	stty("icanon", "echo")
	key := ""
	if err == nil && n > 0 {
		key = strings.Trim(string(buf[:n]), "\r\n\t")
	}
	fmt.Println(key)
	return key
}

func stty(args ...string) {
	c := exec.Command("stty", args...)
	c.Stdin = os.Stdin
	c.Stdout = os.Stdout
	c.Stderr = os.Stderr
	c.Run()
}