ncurses-based list

pemis.rb

#!/usr/bin/env ruby
# -*- coding: utf-8 -*-

require 'curses'

# Prepare curses and cleanup after application is finished
def with_curses
  Curses.noecho      # Do not print input keys
  Curses.curs_set 0  # Remove cursor
  Curses.init_screen
  Curses.start_color # Enable colors
  # Load color settings for list elements
  Curses.init_pair(1, Curses::COLOR_BLACK,  Curses::COLOR_YELLOW) # Highlighted element
  Curses.init_pair(2, Curses::COLOR_YELLOW, Curses::COLOR_BLACK)  # Ordinary element
  begin
    yield
  ensure
    Curses.close_screen
  end
end

class CursedList
  attr_reader :elems

  def initialize elems = []
    @elems = elems.map { |x| x.to_s.rjust Curses.cols }
    @current = 0
    @top = 0
    display
  end

  def display
    h = Curses.lines
    @top &&= [0, @current - h / 2].max if @current + h / 2 - 1 < @elems.size
    @bottom = [@elems.size - 1, @top + h - 1].min
    @elems[@top..@bottom].each_with_index do |elem, index|
      Curses.setpos(index, 0)
      Curses.attron(Curses.color_pair(if index + @top == @current then 1 else 2 end))
      Curses.addstr(elem)
    end
    @forced = false
  end

  def move direction
    case direction
    when :up   then @current -= 1 unless @current <= 0
    when :down then @current += 1 unless @current >= @elems.size - 1
    end
    display
  end

  def append elem
    @elems << elem
    @top += 1 if @top != 0
    display
  end
end

class CursedList
  def open
    append(@elems.max.to_i.succ.to_s.rjust(Curses.cols))
  end

  def download
  end
end

with_curses do
  xs = CursedList.new
  loop do
    case Curses.getch
    when ?q then break
    when ?k then xs.move(:up)
    when ?j then xs.move(:down)
    when ?o then xs.open
    when ?d then xs.download
    end
  end
end