VRFS-2822 : Add options to query for both filtering on artist and grouping on artist (to get a list of artists through existing query infrastructure).

ruby/lib/jam_ruby/models/jam_track.rb

@@ -57,6 +57,18 @@ module JamRuby
     accepts_nested_attributes_for :jam_track_tap_ins, allow_destroy: true
 
     class << self 
+      # @return array[artist_name(string)]
+      def all_artists 
+        JamTrack.select("original_artist").
+                 group("original_artist").
+                 collect{|jam_track|jam_track.original_artist}
+      end
+
+      # @return array[JamTrack] for given artist_name
+      def tracks_for_artist(artist_name)
+        JamTrack.where("original_artist=?", artist_name).all
+      end
+
       def index(options, user)
         limit = options[:limit]
         limit ||= 20
@@ -72,6 +84,14 @@ module JamRuby
           query = query.joins(:jam_track_rights)
           query = query.where("jam_track_rights.user_id = ?", user.id)
         end
+
+        if options[:artist_name]
+          query = query.where("original_artist=?", options[:artist_name])
+        end
+
+        if options[:group_artist]
+          query = query.group("original_artist")
+        end
         
         query = query.where("jam_tracks.available = ?", true) unless user.admin
         query = query.where("jam_tracks.genre_id = '#{options[:genre]}'") unless options[:genre].blank?