bitmap_editor.rb

class BitmapEditor
  VALID_SIZE_RANGE = (1..250)
  DEFAULT_COLOR = 'O'
  
  def clear(c = cols, r = rows)
    return unless VALID_SIZE_RANGE === r && 
                  VALID_SIZE_RANGE === c
    @bitmap = Array.new(r) { Array.new(c) { DEFAULT_COLOR }}
  end
  
  def color(x, y, color = DEFAULT_COLOR)
    @bitmap[y - 1][x - 1] = color if pixel_exists?(x - 1, y - 1)
  end
  
  def color_row(x1, x2, y, color)
    (x1..x2).each do |x|
      color(x, y, color)
    end
  end
  
  def color_col(x, y1, y2, color)
    (y1..y2).each do |y|
      color(x, y, color)
    end
  end
  
  def to_s
    @bitmap.map { |el| el.join }.join("\n")
  end
  
  def output
    return unless @bitmap
    puts self.to_s
  end
  
  private
  def rows
    @bitmap ? @bitmap.length : 0
  end
  
  def cols
    @bitmap ? @bitmap.first.length : 0
  end
  
  def pixel_exists?(x, y)
    (0..cols - 1) === x && (0..rows - 1) === y
  end  
end

class Handler
  def initialize(editor = BitmapEditor.new, parser_class = Parser)
    @editor = editor
    @parser = parser_class.new(@editor)
  end

  def run(file)
    return puts "please provide correct file" if file.nil? || !File.exists?(file)
    File.open(file).each do |line|
      @parser.parse(line)
    end
  end
  
end

class Parser
  VALID_COMMANDS = /^(C|S|I|L|V|H)\s?(\d{1,3})?\s?(\d{1,3})?\s?([0-9A-Z]{1,3})?\s?([A-Z])?/
  COMMANDS = {
    'C' => :clear,
    'S' => :output,
    'I' => :clear,
    'L' => :color,
    'V' => :color_col,
    'H' => :color_row
  }
  def initialize(editor)
    @editor = editor
  end
  def parse(line)
    matchdata = VALID_COMMANDS.match(line)
    if matchdata
      command, *args = matchdata.captures.compact.map { |el| el =~ /\d{1,3}/ ? el.to_i : el }
      @editor.send(COMMANDS[command], *args)
    end
  end
end

c = Parser.new(BitmapEditor.new)
s = <<-EOF
I 5 6
L 1 3 A
V 2 3 6 W
H 3 5 2 Z
S
EOF
s.each_line { |e| c.parse(e) }