#!/usr/bin/env ruby

class ColorDemo

  ColorString = "##"
  ColorMode = {'fg' => '38', 'bg' => '48'}

  def show_welcome 
    puts <<-END
+----------------------------------------------------------------------------+
| This program shows 256-color support in xterm-compliant terminals. You may |
| notice some flickering while the color codes are mapped in your terminal.  |
| Please resize your terminal to at least the width of this box. Try this:   |
| xterm -fg beige -bg midnightblue -fa "antialias=true:rgba=0:pixelsize=18"  |
+-------------+--------------------------------------------------------------+
| Color Range | Description                                                  |
+-------------+--------------------------------------------------------------+
|  000 - 015  | Standard ANSI colors, but with more pleasing shades          |
|  016 - 231  | 6x6x6 color cube                                             |
|  232 - 255  | Greyscale ramp, with black and white intentionally omitted   |
+-------------+--------------------------------------------------------------|
| Translation: 256colors.rb by Daniel Butler <yup.com@gmail.com>  2005-10-30 |
| Original: 256colors2.pl by Todd Larason <jtl@molehill.org> v1.1 1999-07-11 |
+----------------------------------------------------------------------------+
  END
  end

  def clear_screen
    system("clear")
  end

  def loop_color_cube(mode = nil)
    (0...6).each do |red|
      (0...6).each do |green|
        (0...6).each do |blue|
          yield red, green, blue
        end
        print nocolor(" ") if mode == :cube
      end
      print "\n" if mode == :cube
    end  
  end

  def setup_color_cube_color
    # Colors 16-231 are a 6x6x6 color cube
    loop_color_cube do |red, green, blue|
      printf("\x1b]4;%d;rgb:%2.2x/%2.2x/%2.2x\x1b\\",
        16 + (red * 36) + (green * 6) + blue,
        (red * 42.5).to_i,
        (green * 42.5).to_i,
        (blue * 42.5).to_i)
    end  
  end

  def setup_color_cube_gray
    # Colors 232-255 are a grayscale ramp, intentionally
    # leaving out black and white
    (0...24).each do |gray|
      level = (gray * 10) + 8
      printf("\x1b]4;%d;rgb:%2.2x/%2.2x/%2.2x\x1b\\",
        232 + gray, level, level, level);
    end
  end

  def colorize(color, text, mode)
    "\x1b[#{ColorMode[mode]};5;#{color}m#{text}"
  end

  def nocolor(text)
    "\x1b[0m#{text}"
  end

  def display_system_colors(mode)
    puts "System colors (#{mode}):"
    (0...16).each do |color|
      print colorize(color, ColorString, mode)
      print nocolor("\n") if [7, 15].include? color
    end
  end

  def display_color_cube(mode)
    puts "Color cube, 6x6x6 (#{mode}):"
    loop_color_cube(:cube) do |red, green, blue| 
      print colorize(16 + (red * 36) + 
        (green * 6) + blue, ColorString, mode)
    end
  end

  def display_grayscale_ramp(mode)
    puts "Grayscale ramp (#{mode}):"
    (232...256).each do |color|
      print colorize(color, ColorString, mode)
    end
    print nocolor("\n")
  end

  def go
    clear_screen
    show_welcome
    setup_color_cube_color
    setup_color_cube_gray
    ['fg', 'bg'].each do |mode|
      display_system_colors(mode)
      display_color_cube(mode)
      display_grayscale_ramp(mode)
    end
  end
end

demo = ColorDemo.new
demo.go