Add finishing rate to exercise statistics

app/models/exercise.rb

@@ -352,7 +352,11 @@ class Exercise < ActiveRecord::Base
   end
 
   def has_user_solved(user)
-    return maximum_score(user).to_i == maximum_score.to_i
+    maximum_score(user).to_i == maximum_score.to_i
+  end
+
+  def finishers
+    ExternalUser.joins(:submissions).where(submissions: {exercise_id: id, score: maximum_score, cause: %w(submit assess)}).distinct
   end
 
   def set_default_values

app/views/exercises/statistics.html.slim

@@ -2,9 +2,15 @@ script src="http://labratrevenge.com/d3-tip/javascripts/d3.tip.v0.6.3.js"
 h1 = @exercise
 
 = row(label: '.participants', value: @exercise.users.distinct.count)
+
 - [:intermediate, :final].each do |scope|
   = row(label: ".#{scope}_submissions") do
     = "#{@exercise.submissions.send(scope).count} (#{t('.users', count: @exercise.submissions.send(scope).distinct.count(:user_id))})"
+
+= row(label: '.finishing_rate') do
+  p == @exercise.finishers.count ? "#{t('shared.out_of', maximum_value: @exercise.users.distinct.count, value: @exercise.finishers.count)} #{t('exercises.statistics.external_users')}" : empty
+  p = progress_bar((100.0 / @exercise.users.distinct.count * @exercise.finishers.count).round(2))
+
 = row(label: '.average_score') do
   p == @exercise.average_score ? t('shared.out_of', maximum_value: @exercise.maximum_score, value: @exercise.average_score.round(2)) : empty
   p = progress_bar(@exercise.average_percentage)
@@ -40,4 +46,4 @@ h1 = @exercise
             td = link_to_if symbol==:external_users, label, {controller: "exercises", action: "statistics", external_user_id: user.id, id: @exercise.id}
             td = us['maximum_score'] or 0
             td = us['runs']
-            td = @exercise.average_working_time_for(user.id) or 0
+            td = @exercise.average_working_time_for(user.id) or 0