Add export functionality

app/controllers/home_controller.rb

@@ -6,4 +6,9 @@ class HomeController < ApplicationController
     @talks = Talk.ordered_by_rating
     @ratings = Ratings.new
   end
+
+  def export
+    @talks = Talk.all
+    @talk_preferences = TalkPreference.all
+  end
 end

app/models/talk_preference.rb

@@ -5,6 +5,10 @@ class TalkPreference < ActiveRecord::Base
 
   before_create :assign_new_unique_id
 
+  def include?(id)
+    talks.include? id.to_s
+  end
+
   private
 
   def assign_new_unique_id

app/views/home/_talk_preference.csv.erb

@@ -0,0 +1 @@
+<%= CSV.generate_line([talk_preference.hashed_unique_id, talk_preference.created_at] + @talks.map(&:id).map { |talk| talk_preference.include? talk }).html_safe -%>

app/views/home/export.csv.erb

@@ -0,0 +1,3 @@
+<%- headers = ['ID', 'Created at'] + @talks.map(&:id) -%>
+<%= CSV.generate_line headers -%>
+<%= render partial: 'talk_preference', collection: @talk_preferences %>

config/routes.rb

@@ -2,4 +2,5 @@ Rails.application.routes.draw do
   resources :talk_preferences, only: [:index, :show, :create, :update]
   root to: 'home#index'
   get 'ratings' => 'home#ratings'
+  get 'export' => 'home#export'
 end