script.rb

require 'osaka'
require 'growl'

def get_player_position
  Osaka::ScriptRunner.execute(%q(tell application "iTunes" to get the player position)).to_f
end

def get_track_description
  Osaka::ScriptRunner.execute(%q(tell application "iTunes" to get the current track's long description))
end

def get_tracklist(description)
  description.lines.map(&:strip)
    .map { |line| [line, line.match(/\[(\d+):(\d+):(\d+)\]/)] }
    .reject { |text, match| match.nil? }
    .map { |text, match| { text: text, time: match_to_time(match) } }
end

def match_to_time(m)
  m[1].to_f * 3600 + m[2].to_f * 60 + m[3].to_f
end

current_position = -Float::INFINITY

loop do
  last_position, current_position = [current_position, get_player_position]
  tracklist = get_tracklist(get_track_description)
  new_song = tracklist.reverse.find { |track|
      last_position < track[:time] && track[:time] <= current_position }
  if new_song
    Growl.notify new_song[:text], name: 'cuegrowler', title: 'New Track'
    puts "\n[#{Time.now}]"
    puts new_song[:text]
  end
  sleep 2
end