Quiz Stats - Maintain ERB compatibility

This patch makes it so that if you want to get the new stats from the
back-end, you'll have to explicitly pass a "legacy=false" parameter to
the report generator routine. Old code will use the old output, new code
will use the CanvasQuizStatistics gem for stats.

Closes CNVS-13198

TEST PLAN
---- ----

  - create a quiz with a bunch of questions and take it by multiple
    students
  - visit the ERB stats page at
    /courses/:course_id/quizzes/:quiz_id/statistics
    - verify that the page renders and looks just like how it was before
      the work on its ember counterpart
  - visit the ember stats page at
    /courses/:course_id/quizzes/fabulous_quizzes#:quiz_id/statistics
    - verify the ember page is still functional

Change-Id: I0a9e8d69eacc64a8727f238fc0c2e2acd44c0451
Reviewed-on: https://gerrit.instructure.com/35167
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Caleb Guanzon <cguanzon@instructure.com>
Reviewed-by: Derek DeVries <ddevries@instructure.com>
Product-Review: Ahmad Amireh <ahmad@instructure.com>

app/models/quizzes/quiz_question/essay_question.rb

@@ -26,4 +26,17 @@ class Quizzes::QuizQuestion::EssayQuestion < Quizzes::QuizQuestion::Base
     user_answer.answer_details[:text] = Sanitize.clean(user_answer.answer_text, config) || ""
     nil
   end
+
+  def stats(responses)
+    stats = {:essay_responses => []}
+
+    responses.each do |response|
+      stats[:essay_responses] << {
+        :user_id => response[:user_id],
+        :text => response[:text].to_s.strip
+      }
+    end
+
+    @question_data.merge stats
+  end
 end

app/models/quizzes/quiz_statistics/item_analysis.rb

@@ -34,7 +34,7 @@ class Quizzes::QuizStatistics::ItemAnalysis < Quizzes::QuizStatistics::Report
 
   MIN_STATS_FOR_ALPHA = 15
 
-  def generate
+  def generate(legacy=true)
     stats = summary_stats_for_quiz
     stats.map do |item|
       question_item_analysis = {

app/models/quizzes/quiz_statistics/student_analysis.rb

@@ -45,7 +45,7 @@ class Quizzes::QuizStatistics::StudentAnalysis < Quizzes::QuizStatistics::Report
   #   :submission_correct_count_average=>1,
   #   :questions=>
   #     [output of stats_for_question for every question in submission_data]
-  def generate
+  def generate(legacy=true)
     submissions = submissions_for_statistics
     # questions: questions from quiz#quiz_data
     #{1022=>
@@ -144,7 +144,7 @@ class Quizzes::QuizStatistics::StudentAnalysis < Quizzes::QuizStatistics::Report
         end
       end
       if obj[:answers] && obj[:question_type] != 'text_only_question'
-        stat = stats_for_question(obj, responses_for_question[obj[:id]])
+        stat = stats_for_question(obj, responses_for_question[obj[:id]], legacy)
         stats[:questions] << ['question', stat]
       end
     end
@@ -358,8 +358,8 @@ class Quizzes::QuizStatistics::StudentAnalysis < Quizzes::QuizStatistics::Report
   #   "unexpected_response_values"=>[],
   #   "user_ids"=>[1,2,3],
   #   "multiple_responses"=>false}],
-  def stats_for_question(question, responses)
-    if CQS.can_analyze?(question)
+  def stats_for_question(question, responses, legacy=true)
+    if !legacy && CQS.can_analyze?(question)
       # the gem expects all hash keys to be symbols:
       question = CQS::Util.deep_symbolize_keys(question)
       responses = responses.map(&CQS::Util.method(:deep_symbolize_keys))

app/serializers/quizzes/quiz_statistics_serializer.rb

@@ -125,11 +125,11 @@ module Quizzes
     private
 
     def student_analysis_report
-      @student_analysis_report ||= object[:student_analysis].report.generate
+      @student_analysis_report ||= object[:student_analysis].report.generate(false)
     end
 
     def item_analysis_report
-      @item_analysis_report ||= object[:item_analysis].report.generate
+      @item_analysis_report ||= object[:item_analysis].report.generate(false)
     end
 
     def remove_unwanted_fields(question)

spec/models/quizzes/quiz_statistics/student_analysis_spec.rb

@@ -328,11 +328,22 @@ describe Quizzes::QuizStatistics::StudentAnalysis do
           with(question_data, responses).
           returns({ some_metric: 5 })
 
-      output = subject.send(:stats_for_question, question_data, responses)
+      output = subject.send(:stats_for_question, question_data, responses, false)
       output.should == {
         question_type: 'essay_question',
         some_metric: 5
       }.with_indifferent_access
     end
+
+    it "shouldn't proxy if the legacy flag is on" do
+      question_data = {
+        question_type: 'essay_question',
+        answers: []
+      }
+
+      CanvasQuizStatistics.expects(:analyze).never
+
+      subject.send(:stats_for_question, question_data, [])
+    end
   end
 end