README.md

Usage:

puts "What is your favourite colour?"
InteractivePrompt.call(%w(red green blue yellow purple orange))

Renders this:

cursor.rb

class Cursor
  CONTROL_SEQ = "\e[".freeze

  class << self
    def show
      "#{CONTROL_SEQ}?25h"
    end

    def hide
      "#{CONTROL_SEQ}?25l"
    end

    def move(dir, n = 1)
      mappings = {
        up:     'A',
        down:   'B',
        left:   'D',
        right:  'C',
      }
      [CONTROL_SEQ, n.to_s, mappings[dir]].join
    end

    def next_line
      move(:down, '') + CONTROL_SEQ + "1G"
    end

    def previous_line
      move(:up, '') + CONTROL_SEQ + "1G"
    end

    def end_of_previous_line
      previous_line + move(:right, "\033[")
    end

    def clear(n = 1)
      n.times.reduce('') do |acc, idx|
        mover = idx == n - 1 ? '' : move(:up)
        clear = CONTROL_SEQ + '2K' + CONTROL_SEQ + "1G"
        acc << clear + mover
      end
    end
  end
end

interactive_prompt.rb

require 'io/console'
require_relative 'cursor'

class InteractivePrompt
  def self.call(options)
    list = self.new(options)
    options[list.call - 1]
  end

  def initialize(options)
    @options = options
    @active = 1
    @marker = '>'
    @answer = nil
  end

  def call
    print(Cursor.hide)
    while @answer.nil?
      render_options
      get_input
      print(Cursor.clear(@options.size + 1))
      print(Cursor.end_of_previous_line + "\n")
    end
    render_options
    @answer
  ensure
    print(Cursor.show)
    print(Cursor.end_of_previous_line + "\n")
  end

  private

  def get_input
    case read_char
    when "\e[A", 'h'    # up
      @active = @active - 1 % @options.length
    when "\e[B", 'j'    # down
      @active = @active + 1 % @options.length
    when " ", "\r"      # enter/select
      @answer = @active
    when "\u0003", "\e" # Control-C or escape
      exit 0
    end
  end

  # Will handle 2-3 character sequences like arrow keys and control-c
  def read_char
    STDIN.echo = false
    STDIN.raw!

    input = STDIN.getc.chr
    return input unless input == "\e"
    input << STDIN.read_nonblock(3) rescue nil
    input << STDIN.read_nonblock(2) rescue nil
  ensure
    STDIN.echo = true
    STDIN.cooked!
    return input
  end

  def render_options
    @options.each_with_index do |choice, index|
      num = index + 1
      message = "  #{num.to_s}. #{choice}"
      message = "\x1b[36> #{message.strip}\x1b[0" if num == @active
      puts message
    end
  end
end