playlist.rb

class Playlist < AR::Base
  belongs_to :owner, :class_name => 'User'
end
  

class DefaultPlaylist < Playlist

  def name
    "On the go"
  end
  
end

class VirtualPlaylist < Playlist
  
  Track_limit = 50
  
  attr_accessor :mode
  
  serilize :track_ids

  def tracks
    refresh! unless track_ids
    Track.all(:conditions => {:id=> track_ids}) 
  end
  
  def refresh!
    case mode
    when :recent
      self.track_ids = Activity.played(
        :select   => 'target_id',
        :include  => :target,
        :conditions => { :target_type => 'played'}, 
        :limit    => Track_limit,
        :group    => 'target_type, target_id'
      ).map(&:target_id)
    when :favourite
    
    when :popular
    
    end
    
    self.save
  end
end