init

Gemfile

@@ -1,5 +1,5 @@
 source 'https://rubygems.org'
-
+ruby "2.3.0"
 
 # Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
 gem 'rails', '4.1.4'
@@ -39,12 +39,16 @@ gem 'spring',        group: :development
 # gem 'debugger', group: [:development, :test]
 
 gem 'bundler'
-
+gem 'rails_12factor'
 gem 'bootstrap-sass', '3.3.5'
 gem 'bootstrap-sass-extras'
 gem 'binding_of_caller'
 gem 'tzinfo-data'
 gem 'validates_formatting_of'
+gem 'haml-rails'
+gem 'kaminari'
+gem 'bootstrap-kaminari-views'
+gem 'bulk_insert'
 
 group :development do
   gem 'pry-rails'

Gemfile.lock

@@ -36,12 +36,17 @@ GEM
       rack (>= 0.9.0)
     binding_of_caller (0.7.2)
       debug_inspector (>= 0.0.1)
+    bootstrap-kaminari-views (0.0.5)
+      kaminari (>= 0.13)
+      rails (>= 3.1)
     bootstrap-sass (3.3.5)
       autoprefixer-rails (>= 5.0.0.1)
       sass (>= 3.2.19)
     bootstrap-sass-extras (0.0.7)
       rails (>= 3.1.0)
     builder (3.2.3)
+    bulk_insert (1.3.0)
+      activerecord (>= 4.1.0)
     coderay (1.1.1)
     coffee-rails (4.0.1)
       coffee-script (>= 2.2.0)
@@ -53,7 +58,20 @@ GEM
     debug_inspector (0.0.2)
     erubis (2.7.0)
     execjs (2.7.0)
+    haml (4.0.7)
+      tilt
+    haml-rails (0.9.0)
+      actionpack (>= 4.0.1)
+      activesupport (>= 4.0.1)
+      haml (>= 4.0.6, < 5.0)
+      html2haml (>= 1.0.1)
+      railties (>= 4.0.1)
     hike (1.2.3)
+    html2haml (2.0.0)
+      erubis (~> 2.7.0)
+      haml (~> 4.0.0)
+      nokogiri (~> 1.6.0)
+      ruby_parser (~> 3.5)
     i18n (0.7.0)
     jbuilder (2.6.1)
       activesupport (>= 3.0.0, < 5.1)
@@ -62,13 +80,19 @@ GEM
       railties (>= 3.0, < 5.0)
       thor (>= 0.14, < 2.0)
     json (1.8.6)
+    kaminari (0.17.0)
+      actionpack (>= 3.0.0)
+      activesupport (>= 3.0.0)
     mail (2.5.4)
       mime-types (~> 1.16)
       treetop (~> 1.4.8)
     method_source (0.8.2)
     mime-types (1.25.1)
+    mini_portile2 (2.1.0)
     minitest (5.10.1)
     multi_json (1.12.1)
+    nokogiri (1.6.8.1)
+      mini_portile2 (~> 2.1.0)
     pg (0.19.0)
     polyglot (0.3.5)
     pry (0.10.4)
@@ -90,13 +114,20 @@ GEM
       bundler (>= 1.3.0, < 2.0)
       railties (= 4.1.4)
       sprockets-rails (~> 2.0)
+    rails_12factor (0.0.3)
+      rails_serve_static_assets
+      rails_stdout_logging
+    rails_serve_static_assets (0.0.5)
+    rails_stdout_logging (0.0.5)
     railties (4.1.4)
       actionpack (= 4.1.4)
       activesupport (= 4.1.4)
       rake (>= 0.8.7)
       thor (>= 0.18.1, < 2.0)
     rake (12.0.0)
     rdoc (4.3.0)
+    ruby_parser (3.8.4)
+      sexp_processor (~> 4.1)
     sass (3.2.19)
     sass-rails (4.0.5)
       railties (>= 4.0.0, < 5.0)
@@ -106,6 +137,7 @@ GEM
     sdoc (0.4.2)
       json (~> 1.7, >= 1.7.7)
       rdoc (~> 4.0)
+    sexp_processor (4.7.0)
     slop (3.6.0)
     spring (1.7.2)
     sprockets (2.12.4)
@@ -141,19 +173,27 @@ PLATFORMS
 DEPENDENCIES
   better_errors
   binding_of_caller
+  bootstrap-kaminari-views
   bootstrap-sass (= 3.3.5)
   bootstrap-sass-extras
+  bulk_insert
   bundler
   coffee-rails (~> 4.0.0)
+  haml-rails
   jbuilder (~> 2.0)
   jquery-rails
+  kaminari
   pg
   pry-rails
   rails (= 4.1.4)
+  rails_12factor
   sass-rails (~> 4.0.3)
   sdoc (~> 0.4.0)
   spring
   turbolinks
   tzinfo-data
   uglifier (>= 1.3.0)
   validates_formatting_of
+
+BUNDLED WITH
+   1.11.2

README.md

@@ -12,6 +12,40 @@ To receive JSON run:
 curl -H"ACCEPT: application/json" http://simplehabitrecommender.herokuapp.com?recommendations?subtopic=XYZ
 ```
 
+## Challenge Instructions
+
+For this exercise, we want to be able to build a simple recommendation engine for Simple Habit meditators. To do this, we’ve included a list of all the meditations that have been completed by users on our site — this file is called ‘listens.json’. The format of this file is a JSON array that contains objects that contain three properties:
+
+    subtopic: a UUID of the subtopic that was listened to
+    listenDate: an ISO date string of when the listen occurred
+    user: a UUID of the user who listened to the meditation
+
+For reference, there is also a table of subtopics that can translate the subtopic UUIDs into real names and descriptions. The format of this document is a JSON array that contains objects that match:
+
+    id: The UUID of the subtopic
+    name: The name of the subtopic
+    description: A description of the subtopic
+
+Subtopics correspond to the multi-day series on our platform.
+
+We want to build a very simple recommendation engine here. After a user finishes a meditation, we want to recommend them other series to listen to. The most basic algorithm here is conditional probability. Basically, for every subtopic S, we want to determine the most popular subtopics that users who listened to S also listened to. So for example, if the listens look like:
+
+    User A: listened to 1, 4, 5
+    User B: listened to 1, 3, 5
+    User C: listened to 2, 3, 5
+
+A recommendation for meditation 1 would be meditation 5, since of the two users who listened to meditation 1, 100% of them also listened to meditation 5. Similarly, the recommendations for meditation 5 would be meditations 1 or 3, based on co-occurrences. (There are definitely better recommendation engines than this, but this is the simplest to explain.)
+
+The deliverable here will be a server that will service one route: /recommendations?subtopic=X that will return a list of subtopics to recommend, given that a user just listened to X.
+
+- Feel free to use any language you feel comfortable using.
+- Feel free also to use any third party libraries or external services you feel comfortable using, for example using a MySQL or Mongo engine is fine.
+- The return format of the API should be a JSON list of the top 4 subtopic UUIDs that the engine would recommend. If there are not enough recommendations, then showing fewer is fine.
+- The startup time of the server can take as long as you need.
+- No need to support live updates to the recommendation engine — assume this data is all that is needed.
+- In terms of performance, we want the service times of the API call to be as fast as possible.
+- When you have a server implementation, create a .zip file of it and whatever other scripts you produced and send it back via email.
+
 ## Getting Started
 
 1. Install Rails at the command prompt if you haven't yet:

app/assets/javascripts/listens.js.coffee

@@ -0,0 +1,3 @@
+# Place all the behaviors and hooks related to the matching controller here.
+# All this logic will automatically be available in application.js.
+# You can use CoffeeScript in this file: http://coffeescript.org/

app/assets/javascripts/recommendations.js.coffee

@@ -0,0 +1,3 @@
+# Place all the behaviors and hooks related to the matching controller here.
+# All this logic will automatically be available in application.js.
+# You can use CoffeeScript in this file: http://coffeescript.org/

app/assets/javascripts/sub_topics.js.coffee

@@ -0,0 +1,3 @@
+# Place all the behaviors and hooks related to the matching controller here.
+# All this logic will automatically be available in application.js.
+# You can use CoffeeScript in this file: http://coffeescript.org/

app/assets/javascripts/users.js.coffee

@@ -0,0 +1,3 @@
+# Place all the behaviors and hooks related to the matching controller here.
+# All this logic will automatically be available in application.js.
+# You can use CoffeeScript in this file: http://coffeescript.org/

app/assets/stylesheets/application.css.scss

@@ -14,13 +14,9 @@
 *= require_self
 */
 @import "bootstrap_configuration";
-
 @import "bootstrap-sprockets";
-
 @import "bootstrap";
 
-//->Prelang (ui_framework:twitter_bootstrap)
-
 // Give everything in 'yield' margin to separate it.
 .yield {
   margin: 30px;

app/assets/stylesheets/listens.css.scss

@@ -0,0 +1,3 @@
+// Place all the styles related to the listens controller here.
+// They will automatically be included in application.css.
+// You can use Sass (SCSS) here: http://sass-lang.com/

app/assets/stylesheets/recommendations.css.scss

@@ -0,0 +1,3 @@
+// Place all the styles related to the recommendations controller here.
+// They will automatically be included in application.css.
+// You can use Sass (SCSS) here: http://sass-lang.com/

app/assets/stylesheets/sub_topics.css.scss

@@ -0,0 +1,3 @@
+// Place all the styles related to the sub_topics controller here.
+// They will automatically be included in application.css.
+// You can use Sass (SCSS) here: http://sass-lang.com/

app/assets/stylesheets/users.css.scss

@@ -0,0 +1,3 @@
+// Place all the styles related to the users controller here.
+// They will automatically be included in application.css.
+// You can use Sass (SCSS) here: http://sass-lang.com/

app/controllers/listens_controller.rb

@@ -0,0 +1,5 @@
+class ListensController < ApplicationController
+  def index
+    @listens = Listen.all.page params[:page]
+  end
+end

app/controllers/recommendations_controller.rb

@@ -0,0 +1,18 @@
+class RecommendationsController < ApplicationController
+  def index
+    if params[:subtopic].blank?
+      flash[:alert] = "Please provide a subtopic parameter: '/recommendations?subtopic=X' or paste the subtopic into the search field above."
+      redirect_to root_path and return
+    end
+
+    @sub_topic = SubTopic.find_by_subtopic_id params[:subtopic]
+    @recommender = Recommender.new @sub_topic, params.fetch(:per, 4), params[:page]
+
+    respond_to do |format|
+      format.html
+      format.json do
+        render json: { recommended_subtopics: @recommender.ask.map(&:first) }
+      end
+    end
+  end
+end

app/controllers/sub_topics_controller.rb

@@ -0,0 +1,9 @@
+class SubTopicsController < ApplicationController
+  def index
+    @sub_topics = SubTopic.all.page(params[:page]).per 20
+  end
+
+  def show
+    @sub_topic = SubTopic.find params[:id]
+  end
+end

app/controllers/users_controller.rb

@@ -0,0 +1,9 @@
+class UsersController < ApplicationController
+  def index
+    @users = User.all.includes(:listens).page(params[:page]).per 20
+  end
+
+  def show
+    @user = User.find params[:id]
+  end
+end

app/helpers/application_helper.rb

@@ -1,2 +1,5 @@
 module ApplicationHelper
+  def paginate(objects, options = {})
+    super objects, options.reverse_merge!(theme: 'twitter-bootstrap-3')
+  end
 end

app/helpers/listens_helper.rb

@@ -0,0 +1,2 @@
+module ListensHelper
+end

app/helpers/recommendations_helper.rb

@@ -0,0 +1,2 @@
+module RecommendationsHelper
+end

app/helpers/sub_topics_helper.rb

@@ -0,0 +1,2 @@
+module SubTopicsHelper
+end

app/helpers/users_helper.rb

@@ -0,0 +1,2 @@
+module UsersHelper
+end

app/models/listen.rb

@@ -1,2 +1,23 @@
+# == Schema Information
+#
+# Table name: listens
+#
+#  id          :integer          not null, primary key
+#  user_id     :string(255)
+#  listen_date :datetime
+#  subtopic_id :string(255)
+#  created_at  :datetime
+#  updated_at  :datetime
+#
+
 class Listen < ActiveRecord::Base
+  belongs_to :user, primary_key: "user_id"
+  belongs_to :sub_topic, primary_key: :subtopic_id, foreign_key: :subtopic_id
+  scope :uniq_by_user, -> { select("DISTINCT ON (listens.user_id) listens.*").order :user_id }
+  default_scope -> { order listen_date: :desc }
+  paginates_per 20
+
+  def self.uniq_user_count
+    count "DISTINCT user_id"
+  end
 end

app/models/recommendation.rb

@@ -1,2 +1,15 @@
+# == Schema Information
+#
+# Table name: recommendations
+#
+#  id                       :integer          not null, primary key
+#  subtopic_id              :string(255)
+#  recommended_subtopic_ids :text
+#  created_at               :datetime
+#  updated_at               :datetime
+#
+
 class Recommendation < ActiveRecord::Base
+  belongs_to :subtopic
+  serialize :recommended_subtopic_ids, Array
 end

app/models/sub_topic.rb

@@ -1,2 +1,15 @@
+# == Schema Information
+#
+# Table name: sub_topics
+#
+#  id          :integer          not null, primary key
+#  subtopic_id :string(255)
+#  name        :string(255)
+#  description :text
+#  created_at  :datetime
+#  updated_at  :datetime
+#
+
 class SubTopic < ActiveRecord::Base
+  has_many :listens, primary_key: :subtopic_id, foreign_key: :subtopic_id
 end

app/models/user.rb

@@ -1,2 +1,19 @@
+# == Schema Information
+#
+# Table name: users
+#
+#  id         :integer          not null, primary key
+#  user_id    :string(255)
+#  created_at :datetime
+#  updated_at :datetime
+#
+
 class User < ActiveRecord::Base
+  has_many :listens, primary_key: :user_id
+  validates :user_id, uniqueness: true
+
+  scope :who_listened_to, -> subtopic_id { 
+    joins("RIGHT JOIN listens ON listens.user_id = users.user_id").
+    where listens: { subtopic_id: subtopic_id }
+  }
 end