That Stupid Thing I Wrote the Other Day, part 2

require 'time'

class Album < Array
  def age
    map { |track| track.age }.max
  end
  def score
    total / Math.log(age)
  end
  def total
    inject(0.0) do |total_score, track|
      total_score + track.score
    end
  end
  def self.parse(file)
    today = Time.now
    d = {}
    library = Hash.new { |h,k| h[k] = Album.new }

    IO.foreach(File.expand_path(file)) do |line|
      if line =~ /<key>(Name|Artist|Album|Date Added|Play Count|Rating)<\/key><.*?>(.*)<\/.*?>/ then
        key = $1.downcase.split.first
        val = $2
        d[key.intern] = val

        if d.size == 6 then
          date = d[:date].sub(/T.*/, '')
          key = "#{d[:album]} by #{d[:artist]}"
          age = ((today - Time.parse(date)) / 86400.0).to_i
          library[key] << Track.new(age, d[:play].to_i, d[:rating].to_i / 20)

          d.clear
        end
      end
    end
    library
  end
end

Track = Struct.new(:age, :count, :rating)
class Track
  def score
    rating * count.to_f
  end
end

max = (ARGV.shift || 10).to_i
file = ARGV.shift || "~/Music/iTunes/iTunes Music Library.xml"
library = Album.parse(file)

top = library.sort_by { |h,k| -k.score }[0...max]
top.each_with_index do |(artist_album, album), c|
  puts "%-3d = (%4d tot, %5.2f adj): %s" % [c+1, album.total, album.score, artist_album,]
  album.each do |t|
    puts "  #{t.age} days old, #{t.count} count, #{t.rating} rating = #{t.score}"
  end if $DEBUG
end