Add a helper for build c3.js chart compatible data

app/models/ahoy/data_source.rb

@@ -0,0 +1,49 @@
+# This class combines multiple collections with shared keys into a
+# hash of collections compatible with C3.js charts
+#----------------------------------------------------------------------
+
+module Ahoy
+  class DataSource
+
+    # Adds a collection with the datasource
+    # Name is the name of the collection and will be showed in the
+    # chart
+    def add(name, collection)
+      collections.push data:  collection, name: name
+      collection.each{ |k,v| add_key k }
+    end
+
+    def build
+      data = { x: [] }
+      keys.each do |k|
+        # Add the key with a valid date format
+        data[:x].push k.strftime("%Y-%m-%d")
+
+        # Add the value for each column, or 0 if not present
+        collections.each do |col|
+          data[col[:name]] ||= []
+          count = col[:data][k] || 0
+          data[col[:name]].push count
+        end
+      end
+
+      return data
+    end
+
+    private
+
+    def collections
+      @collections ||= []
+    end
+
+    def keys
+      @keys ||= []
+    end
+
+    def add_key(key)
+      keys.push(key) unless keys.include? key
+    end
+
+  end
+
+end

spec/models/ahoy/data_source_spec.rb

@@ -0,0 +1,36 @@
+require 'rails_helper'
+
+describe Ahoy::DataSource do
+  describe '#build' do
+    before :each do
+      time_1 = DateTime.parse("2015-01-01")
+      time_2 = DateTime.parse("2015-01-02")
+      time_3 = DateTime.parse("2015-01-03")
+
+      create :ahoy_event, name: 'foo', time: time_1
+      create :ahoy_event, name: 'foo', time: time_1
+      create :ahoy_event, name: 'foo', time: time_2
+      create :ahoy_event, name: 'bar', time: time_1
+      create :ahoy_event, name: 'bar', time: time_3
+      create :ahoy_event, name: 'bar', time: time_3
+    end
+
+    it 'should work without data sources' do
+      ds = Ahoy::DataSource.new
+      expect(ds.build).to eq x: []
+    end
+
+    it 'should work with single data sources' do
+      ds = Ahoy::DataSource.new
+      ds.add 'foo', Ahoy::Event.where(name: 'foo').group_by_day(:time).count
+      expect(ds.build).to eq :x=>["2015-01-01", "2015-01-02"], "foo"=>[2, 1]
+    end
+
+    it 'should combine data sources' do
+      ds = Ahoy::DataSource.new
+      ds.add 'foo', Ahoy::Event.where(name: 'foo').group_by_day(:time).count
+      ds.add 'bar', Ahoy::Event.where(name: 'bar').group_by_day(:time).count
+      expect(ds.build).to eq :x=>["2015-01-01", "2015-01-02", "2015-01-03"], "foo"=>[2, 1, 0], "bar"=>[1, 0, 2]
+    end
+  end
+end