8tracks_backup.md

##Models:

• Album
• Artist
• Favorite
• Follow
• Genre
• Like
• PlaylistSongs
• PlaylistTags
• Playlist
• Song
• StaffPick
• Tag
• User

##Schema:

ActiveRecord::Schema.define(version: 20160717230059) do

  # These are extensions that must be enabled in order to support this database
  enable_extension "plpgsql"

  create_table "albums", force: :cascade do |t|
    t.string   "title"
    t.integer  "artist_id"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
  end

  add_index "albums", ["artist_id"], name: "index_albums_on_artist_id", using: :btree

  create_table "artists", force: :cascade do |t|
    t.string   "name"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.integer  "genre_id"
  end

  add_index "artists", ["genre_id"], name: "index_artists_on_genre_id", using: :btree

  create_table "genres", force: :cascade do |t|
    t.string   "type"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
  end

  create_table "playlist_songs", force: :cascade do |t|
    t.integer  "playlist_id"
    t.integer  "song_id"
    t.datetime "created_at",  null: false
    t.datetime "updated_at",  null: false
  end

  add_index "playlist_songs", ["playlist_id"], name: "index_playlist_songs_on_playlist_id", using: :btree
  add_index "playlist_songs", ["song_id"], name: "index_playlist_songs_on_song_id", using: :btree

  create_table "playlist_tags", force: :cascade do |t|
    t.integer  "playlist_id"
    t.integer  "tag_id"
    t.datetime "created_at",  null: false
    t.datetime "updated_at",  null: false
  end

  add_index "playlist_tags", ["playlist_id"], name: "index_playlist_tags_on_playlist_id", using: :btree
  add_index "playlist_tags", ["tag_id"], name: "index_playlist_tags_on_tag_id", using: :btree

  create_table "playlists", force: :cascade do |t|
    t.string   "name"
    t.integer  "user_id"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.boolean  "staff_pick"
  end

  add_index "playlists", ["user_id"], name: "index_playlists_on_user_id", using: :btree

  create_table "songs", force: :cascade do |t|
    t.string   "title"
    t.integer  "artist_id"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.integer  "album_id"
  end

  add_index "songs", ["album_id"], name: "index_songs_on_album_id", using: :btree
  add_index "songs", ["artist_id"], name: "index_songs_on_artist_id", using: :btree

  create_table "tags", force: :cascade do |t|
    t.string   "name"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
  end

  create_table "users", force: :cascade do |t|
    t.string   "name"
    t.string   "email"
    t.string   "password_digest"
    t.datetime "created_at",      null: false
    t.datetime "updated_at",      null: false
  end

  add_foreign_key "albums", "artists"
  add_foreign_key "artists", "genres"
  add_foreign_key "playlist_songs", "playlists"
  add_foreign_key "playlist_songs", "songs"
  add_foreign_key "playlist_tags", "playlists"
  add_foreign_key "playlist_tags", "tags"
  add_foreign_key "playlists", "users"
  add_foreign_key "songs", "albums"
  add_foreign_key "songs", "artists"
end

###How it works:

1. After login, the homepage is loaded @ 'home#index'.

      class HomeController < ApplicationController
        
        def index
          @suggestions = current_user.fetch_suggestions
        end
      
      end
   

2. The 'fetch_suggestions' in the user model gathers attributes of likes, follows, favorites, and staff picks, and cycles through creating suggestions until 50 have been made. The suggestions are then saved to a redis store with an expiration of 3 hours.

      class User < ActiveRecord::Base
        has_many :likes
        has_many :favorites
        has_many :followers
        
        has_secure_password
        
        def fetch_suggestions
          suggestions = $redis.get('suggestions')
          if suggestions.nil?
            suggestions = gather_suggestions.to_json
            $redis.set('suggestions', suggestions)
            $redis.expire('suggestions', 3.hour.to_i)
          end
          JSON.load suggestions
        end
        
        def gather_suggestions
          suggestions = []
          while suggestions.count <= 50
            current_attributes = attributes_array[suggestions.count%4]
            suggestions << current_attributes[-1].generate_suggestion
            current_attributes.rotate!(-1)
          end
          suggestions
        end
        
        def attributes_array
          array ||= [self.favorites, self.likes, self.follows, StaffPicks.all].select {|el| !el.empty? || el != nil}
          array
        end
      end
   

3. Each different model type in the 'attributes_array' has a 'generate_suggestion' method that varies depending on what process is needed.

• Example 1: Like

          class Like < ActiveRecord::Base
  
            belongs_to :user
            belongs_to :playlist
            
            def generate_suggestion
              suggestion = SuggestionService.find_suggestion(self.playlist.tags)
              { reason: 'Because you liked "#{self.playlist.name}", playlist: suggestion} 
            end
            
          end
  

• Example 2: StaffPick

          class StaffPicks < ActiveRecord::Base
  
            def generate_suggestion
              suggestion = User.find_by(name: 'staff_picks').last
              { reason: 'Staff Pick', playlist: suggestion } 
            end
  
          end
  

• Example 3: Favorite

          class Favorite < ActiveRecord::Base
          
            belongs_to :user
            belongs_to :song
  
            def generate_suggestion
              tags = [self.artist.name] + [self.artist.genres]
              suggestion = SuggestionService.find_suggestions(tags)
              { reason: "Because you favorited #{self.title} by #{self.song.artist"}, playlist: suggestion }
            end
          end
  

  (Note: The arguments passed through SuggestionService.find_suggestions(argument), would be treated as the name of a tag on the other end. From there similar playlists would be found through similar tags throughout 8tracks playlists.

4. These suggestions are returned to the view and iterated over as cards.

###Optimization:

1. Dynamic Pagination: Instead of loading all 50 suggestions to the homepage at once, implementing a dynamic scroll based pagination could speed things up considerably. An AJAX call would load the first 10 suggested playlists (page 1) onto the view. Once the user scrolls to the bottom of the page, an AJAX call would be made for page 2 of results and so on.

- AJAX call:

        $.ajax({
          url: "/api/v1/home/" + pageNumber,
          type: "GET",
          success: function(response){
            console.log("Success!", response.suggestions)
            appendSuggestions(response)
          }
        });

- API Controller
  
        class Api::V1::HomeController < Api::ApiController
  
          respond_to :json
        
          def index
            respond_with current_user.get_suggestions(params[:page])
          end

        end

2. With the pagination above, using 'ActionContoller::Metal' rather than 'Base' could speed up the load times for scrolling considerably.

3. Grabbing suggestions in batches rather than individually by changing 'generate_suggestion', to 'generate_suggestions(amount)'. This would speed up the initail suggestion grab, but would end in a less hetergeneous feed.