Allow filtering external user statistics by tag

app/controllers/external_users_controller.rb

@@ -14,12 +14,12 @@ class ExternalUsersController < ApplicationController
     authorize!
   end
 
-  def working_time_query
+  def working_time_query(tag=nil)
     """
     SELECT user_id,
-           exercise_id,
+           bar.exercise_id,
            max(score) as maximum_score,
-           count(id) as runs,
+           count(bar.id) as runs,
            sum(working_time_new) AS working_time
     FROM
       (SELECT user_id,
@@ -42,9 +42,12 @@ class ExternalUsersController < ApplicationController
             AND user_type = 'ExternalUser'
           GROUP BY exercise_id,
                    user_id,
-                   id) AS foo) AS bar
+                   id
+          ) AS foo
+      ) AS bar
+    #{tag.nil? ? '' : ' JOIN exercise_tags et ON et.exercise_id = bar.exercise_id AND et.tag_id = ' + tag + ' '}
     GROUP BY user_id,
-             exercise_id;
+             bar.exercise_id;
     """
   end
 
@@ -54,7 +57,7 @@ class ExternalUsersController < ApplicationController
 
     statistics = {}
 
-    ActiveRecord::Base.connection.execute(working_time_query).each do |tuple|
+    ActiveRecord::Base.connection.execute(working_time_query(params[:tag])).each do |tuple|
       statistics[tuple["exercise_id"].to_i] = tuple
     end
 

app/views/external_users/statistics.html.slim

@@ -1,6 +1,6 @@
 h1 = t('.title')
 
-- exercises = Exercise.where(:id => @user.submissions.group(:exercise_id).select(:exercise_id).distinct())
+- exercises = Exercise.where(:id => @user.submissions.group(:exercise_id).select(:exercise_id).distinct)
 
 .table-responsive
   table.table.table-striped.sortable
@@ -10,9 +10,10 @@ h1 = t('.title')
           th.header = t(title)
     tbody
       - exercises.each do |exercise|
-        - if statistics[exercise.id] then stats = statistics[exercise.id] else stats = {"working_time" => 0, "runs" => 0, "score" => 0}
-        tr
-          td = link_to exercise, controller: "exercises", action: "statistics", external_user_id: @user.id, id: exercise.id
-          td = stats["maximum_score"] or 0
-          td = stats["runs"] or 0
-          td = stats["working_time"] or 0
+        - if statistics[exercise.id]
+          - stats = statistics[exercise.id]
+          tr
+            td = link_to exercise, controller: "exercises", action: "statistics", external_user_id: @user.id, id: exercise.id
+            td = stats["maximum_score"] or 0
+            td = stats["runs"] or 0
+            td = stats["working_time"] or 0