Include data in chart tags instead of using AJAX

Now that we've moved the logic to generate the events data to a model,
and we've got access to the model in the component rendering the chart,
we can render the data inside the chart instead of doing an extra AJAX
request to get the same data.

Originally, this was problaby done this way so the page wouldn't take
several seconds to load while preparing the data for the chart when
there are thousands of dates being displayed. With an AJAX call, the
page would load as fast as usual, and then the chart would render after
a few seconds. However, we can have an even better performance
improvement in this scenario if we use a Set instead of an Array. The
method `Array#include?`, which we were calling for every date in the
data, is much slower that `Set#merge`. So now both the page and the
chart load as fast as expected.

We could also use something like:

```
def add
  (...)
  shared_keys.push(*collection.keys)
end

def build
  (...)
  shared_keys.uniq.each do |k|
  (...)
end

def shared_keys
  @shared_keys ||= []
end
```

Or other approaches to avoid using `Array#include?`. The performance
would be similar to the one we get when using `Set`. We're using a `Set`
because it makes more obvious that `shared_keys` is supposed to contain
unique elements.

We've had some tests failing in the past due to these AJAX requests
being triggered automatically during the tests and no expectations
checking the requests have finished, so now we're reducing the amount of
flaky tests.

app/assets/javascripts/stats.js

@@ -5,14 +5,12 @@
   var buildGraph;
 
   buildGraph = function(el) {
-    var conf, url;
+    var conf;
-    url = $(el).data("graph");
     conf = {
       bindto: el,
       data: {
         x: "x",
-        url: url,
+        json: $(el).data("graph")
-        mimeType: "json"
       },
       axis: {
         x: {

app/components/admin/stats/chart_component.rb

@@ -16,7 +16,7 @@ class Admin::Stats::ChartComponent < ApplicationComponent
     end
 
     def chart_tag
-      tag.div("data-graph": admin_api_stats_path(event: event))
+      tag.div("data-graph": chart.data_points.to_json)
     end
 
     def title

app/controllers/admin/api/stats_controller.rb

@@ -1,9 +0,0 @@
-class Admin::Api::StatsController < Admin::Api::BaseController
-  def show
-    if params[:event].present?
-      render json: Ahoy::Chart.new(params[:event]).data_points
-    else
-      render json: {}, status: :bad_request
-    end
-  end
-end

app/models/ahoy/data_source.rb

@@ -9,7 +9,7 @@ module Ahoy
     # chart
     def add(name, collection)
       collections.push data: collection, name: name
-      collection.each_key { |key| add_key key }
+      shared_keys.merge(collection.keys)
     end
 
     def build
@@ -36,11 +36,7 @@ module Ahoy
       end
 
       def shared_keys
-        @shared_keys ||= []
+        @shared_keys ||= Set.new
-      end
-
-      def add_key(key)
-        shared_keys.push(key) unless shared_keys.include? key
       end
   end
 end

config/routes/admin.rb

@@ -241,10 +241,6 @@ namespace :admin do
     end
   end
 
-  namespace :api do
-    resource :stats, only: :show
-  end
-
   resources :geozones, only: [:index, :new, :create, :edit, :update, :destroy]
 
   namespace :site_customization do

spec/components/admin/stats/chart_component_spec.rb

@@ -0,0 +1,13 @@
+require "rails_helper"
+
+describe Admin::Stats::ChartComponent do
+  it "renders a tag with JSON data" do
+    create(:user, :level_three, verified_at: "2009-09-09")
+    chart = Ahoy::Chart.new(:level_3_user)
+
+    render_inline Admin::Stats::ChartComponent.new(chart)
+
+    expect(page).to have_css "h2", exact_text: "Level 3 users verified (1)"
+    expect(page).to have_css "[data-graph='{\"x\":[\"2009-09-09\"],\"Level 3 users verified\":[1]}']"
+  end
+end

spec/controllers/admin/api/stats_controller_spec.rb

@@ -1,36 +0,0 @@
-require "rails_helper"
-
-describe Admin::Api::StatsController, :admin do
-  describe "GET index" do
-    context "events or visits not present" do
-      it "responds with bad_request" do
-        get :show
-
-        expect(response).not_to be_ok
-        expect(response).to have_http_status 400
-      end
-    end
-
-    context "events present" do
-      before do
-        time_1 = Time.zone.local(2015, 01, 01)
-        time_2 = Time.zone.local(2015, 01, 02)
-        time_3 = Time.zone.local(2015, 01, 03)
-
-        create(:proposal, created_at: time_1)
-        create(:proposal, created_at: time_1)
-        create(:proposal, created_at: time_2)
-        create(:debate, created_at: time_1)
-        create(:debate, created_at: time_3)
-        create(:debate, created_at: time_3)
-      end
-
-      it "returns single events formated for working with c3.js" do
-        get :show, params: { event: "proposal_created" }
-
-        expect(response).to be_ok
-        expect(response.parsed_body).to eq "x" => ["2015-01-01", "2015-01-02"], "Citizen proposals created" => [2, 1]
-      end
-    end
-  end
-end