Extract pie chart data logic into model layer

Move most of the tests for this logic into the unit test layer.

app/models/stats/pie_chart_data.rb

@@ -0,0 +1,37 @@
+module Stats
+  class PieChartData
+
+    attr_reader :all_actions_per_context, :values, :labels, :ids, :alpha, :title
+    def initialize(all_actions_per_context, title, alpha)
+      @all_actions_per_context = all_actions_per_context
+      @title = title
+      @alpha = alpha
+    end
+
+    def calculate
+      sum = all_actions_per_context.inject(0){|sum, apc| sum + apc['total']}
+
+      pie_cutoff=10
+      size = [all_actions_per_context.size, pie_cutoff].min
+
+      # explicitly copy contents of hash to avoid ending up with two arrays pointing to same hashes
+      actions_per_context = Array.new(size){|i| {
+        'name' => all_actions_per_context[i]['name'],
+        'total' => all_actions_per_context[i]['total'],
+        'id' => all_actions_per_context[i]['id']
+      } }
+
+      if all_actions_per_context.size > pie_cutoff
+        actions_per_context[-1]['name']=I18n.t('stats.other_actions_label')
+        actions_per_context[-1]['id']=-1
+        size.upto(all_actions_per_context.size-1){ |i| actions_per_context[-1]['total']+=(all_actions_per_context[i]['total']) }
+      end
+
+      @values = Array.new(size){|i| actions_per_context[i]['total']*100/sum }
+      @labels = Array.new(size){|i| actions_per_context[i]['name'].truncate(15, :omission => '...') }
+      @ids = Array.new(size){|i| actions_per_context[i]['id']}
+    end
+
+
+  end
+end