# Used to detect the Linux window manager.
#
# This information is used to determine the default screensaver command.
class Breaktime::LinuxWinManager
  # Thrown if the window manager can't be detected.
  class ManagerUnknown < StandardError; end

  @@managers = {'kcmserver' => 'dcop kdesktop KScreensaverIface lock',
               'gnome-session' => 'gnome-screensaver-command -a',
               'xfce-mcs-manage' => 'xscreensaver-command --lock'}

  attr_reader :cmd

  # Check the process list for known window manager services.
  #
  # If the service is found, return the associated command for starting the
  # screensaver.
  def self.detect_command(log)
    log.debug { "Checking for known window manager processes: #{@@managers.keys.join(", ")}" }
    lines = `ps -eo args|egrep "#{@@managers.keys.join("|")}"|grep -v "egrep"`.split "\n"

    lines.any? or raise ManagerUnknown, 'Unable to detect a known window manager'

    m = @@managers.keys.select {|k| lines.first.include? k}
    log.debug { "Found #{m.first}" }
    @@managers[m.first]
  end
end