ruby - mozrepl

module MozRepl
  require 'base64'
  require 'net/telnet'

  PROMPT = /\nrepl>\s/

  class Telnet < Net::Telnet
    alias_method :old_cmd, :cmd
    def cmd(options, &blk)
      old_cmd(options, &blk).gsub!(MozRepl::PROMPT, '')
    end
  end

  def self.connect(args={})
    session = MozRepl::Telnet.new(args)
    session.waitfor /Welcome to MozRepl.\s*/im
    yield session
    session.close
  end
end

connect_args = {"Host" => 'localhost', "Port" => 4242, "Timeout" => 3}

MozRepl.connect(connect_args) do |session|
  canvas_b64 = %Q[
    var win = getBrowser().selectedTab.linkedBrowser.contentWindow;
    var page_height = win.innerHeight + win.scrollMaxY;
    var page_width = win.document.getElementsByTagName('html')[0].offsetWidth + win.scrollMaxX

    var canvas = document.createElementNS('http://www.w3.org/1999/xhtml', 'canvas');
    canvas.mozOpaque = true;
    canvas.scrollTop = 0;
    canvas.scrollLeft = 0;
    canvas.width = page_width;
    canvas.height = page_height;

    var ctx = canvas.getContext('2d');
    ctx.drawWindow(win, 0, 0, page_width, page_height, 'rgb(255,255,255)');

    canvas.toDataURL();
  ]
  image_b64 = session.cmd(canvas_b64)

  # strip html content type and quotes
  image_b64 = image_b64[23..-2]
  File.open('/Users/adacosta/Desktop/moztest.png', 'w') {|f| f.write(Base64.decode64(image_b64)) }
end