class Headless

# File lib/headless.rb, line 77
def initialize(options = {})
  CliUtil.ensure_application_exists!('Xvfb', 'Xvfb not found on your system')

  @display = options.fetch(:display, DEFAULT_DISPLAY_NUMBER).to_i
  @xvfb_launch_timeout = options.fetch(:xvfb_launch_timeout, DEFAULT_XVFB_LAUNCH_TIMEOUT).to_i
  @autopick_display = options.fetch(:autopick, !options.key?(:display))
  @reuse_display = options.fetch(:reuse, true)
  @dimensions = options.fetch(:dimensions, DEFAULT_DISPLAY_DIMENSIONS)
  @video_capture_options = options.fetch(:video, {})

  already_running = xvfb_running? rescue false
  @destroy_at_exit = options.fetch(:destroy_at_exit, !(@reuse_display && already_running))

  @pid = nil # the pid of the running Xvfb process

  # FIXME Xvfb launch should not happen inside the constructor
  attach_xvfb
end

# File lib/headless.rb, line 140
def self.run(options={}, &block)
  headless = Headless.new(options)
  headless.start
  yield headless
ensure
  headless && headless.destroy
end

# File lib/headless.rb, line 110
def destroy
  stop
  CliUtil.kill_process(pid_filename, preserve_pid_file: true, wait: true)
end

# File lib/headless.rb, line 130
def destroy_at_exit?
  @destroy_at_exit
end

# File lib/headless.rb, line 118
def destroy_sync
  destroy
end

# File lib/headless.rb, line 124
def destroy_without_sync
  stop
  CliUtil.kill_process(pid_filename, preserve_pid_file: true)
end

# File lib/headless.rb, line 97
def start
  @old_display = ENV['DISPLAY']
  ENV['DISPLAY'] = ":#{display}"
  hook_at_exit
end

# File lib/headless.rb, line 104
def stop
  ENV['DISPLAY'] = @old_display
end

# File lib/headless.rb, line 153
def take_screenshot(file_path, options={})
  using = options.fetch(:using, :imagemagick)
  case using
  when :imagemagick
    CliUtil.ensure_application_exists!('import', "imagemagick is not found on your system. Please install it using sudo apt-get install imagemagick")
    system "#{CliUtil.path_to('import')} -display localhost:#{display} -window root #{file_path}"
  when :xwd
    CliUtil.ensure_application_exists!('xwd', "xwd is not found on your system. Please install it using sudo apt-get install X11-apps")
    system "#{CliUtil.path_to('xwd')} -display localhost:#{display} -silent -root -out #{file_path}"
  when :graphicsmagick, :gm
    CliUtil.ensure_application_exists!('gm', "graphicsmagick is not found on your system. Please install it.")
    system "#{CliUtil.path_to('gm')} import -display localhost:#{display} -window root #{file_path}"
  else
    raise Headless::Exception.new('Unknown :using option value')
  end
end

# File lib/headless.rb, line 149
def video
  @video_recorder ||= VideoRecorder.new(display, dimensions, @video_capture_options)
end

# File lib/headless.rb, line 172
def attach_xvfb
  possible_display_set = @autopick_display ? @display..MAX_DISPLAY_NUMBER : Array(@display)
  pick_available_display(possible_display_set, @reuse_display)
end

# File lib/headless.rb, line 200
def ensure_xvfb_launched(out_pipe)
  start_time = Time.now
  errors = ""
  begin
    begin
      errors += out_pipe.read_nonblock(10000)
      if errors.include? "Cannot establish any listening sockets"
        raise Headless::Exception.new("Display socket is taken but lock file is missing - check the Headless troubleshooting guide")
      end
      if errors.include? "Server is already active for display #{display}"
        # This can happen if there is a race to grab the lock file.
        # Not an exception, just return false to let pick_available_display choose another:
        return false
      end
    rescue IO::WaitReadable
      # will retry next cycle
    end
    sleep 0.01 # to avoid cpu hogging
    raise Headless::Exception.new("Xvfb launched but did not complete initialization") if (Time.now-start_time)>=@xvfb_launch_timeout
  # Continue looping until Xvfb has written its pidfile:
  end while !xvfb_running?

  # If for any reason the pid file doesn't match ours, we lost the race to
  # get the file lock:
  return @pid == read_xvfb_pid
end

# File lib/headless.rb, line 245
def hook_at_exit
  unless @at_exit_hook_installed
    @at_exit_hook_installed = true
    at_exit do
      exit_status = $!.status if $!.is_a?(SystemExit)
      destroy if destroy_at_exit?
      exit exit_status if exit_status
    end
  end
end

# File lib/headless.rb, line 187
def launch_xvfb
  out_pipe, in_pipe = IO.pipe
  @pid = Process.spawn(
    CliUtil.path_to("Xvfb"), ":#{display}", "-screen", "0", dimensions, "-ac",
    err: in_pipe)
  raise Headless::Exception.new("Xvfb did not launch - something's wrong") unless @pid
  # According to docs, you should either wait or detach on spawned procs:
  Process.detach @pid
  return ensure_xvfb_launched(out_pipe)
  ensure
    in_pipe.close
end

# File lib/headless.rb, line 177
def pick_available_display(display_set, can_reuse)
  display_set.each do |display_number|
    @display = display_number

    return true if xvfb_running? && can_reuse && (xvfb_mine? || !@autopick_display)
    return true if !xvfb_running? && launch_xvfb
  end
  raise Headless::Exception.new("Could not find an available display")
end

# File lib/headless.rb, line 237
def pid_filename
  "/tmp/.X#{display}-lock"
end

# File lib/headless.rb, line 241
def read_xvfb_pid
  CliUtil.read_pid(pid_filename)
end

# File lib/headless.rb, line 227
def xvfb_mine?
  CliUtil.process_mine?(read_xvfb_pid)
end

# File lib/headless.rb, line 233
def xvfb_running?
  (pid = read_xvfb_pid) && CliUtil.process_running?(pid)
end