Implement a endpoint for model solutions

Author: nygrenh

app/controllers/api/v8/exercises/model_solutions_controller.rb

@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+
+module Api
+  module V8
+    module Exercises
+      class ModelSolutionsController < Api::V8::BaseController
+        def index
+          unauthorize_guest!
+          exercise = Exercise.find(params[:exercise_id])
+          course = exercise.course
+          authorize! :read, exercise
+          solution = exercise.solution
+          begin
+            authorize! :read, solution
+          rescue CanCan::AccessDenied
+            model_solution_token_used_on_this_exercise = tokens_used = ModelSolutionTokenUsed.where(user: current_user, course: course, exercise_name: ex.name).count > 0
+            grant_model_solution_token_every_nth_completed_exercise = course.grant_model_solution_token_every_nth_completed_exercise
+            if grant_model_solution_token_every_nth_completed_exercise && grant_model_solution_token_every_nth_completed_exercise > 0
+              completed_exercises_count = course.submissions.where(all_tests_passed: true, user: current_user).distinct.select(:exercise_name).count
+              total_model_solution_tokens = completed_exercises_count / grant_model_solution_token_every_nth_completed_exercise
+
+              tokens_used = ModelSolutionTokenUsed.where(user: current_user, course: course).count
+              available_model_solution_tokens = total_model_solution_tokens - tokens_used
+              if available_model_solution_tokens > 0
+                ModelSolutionTokenUsed.create!(user: current_user, course: course, exercise_name: exercise.name)
+              else
+                raise CanCan::AccessDenied
+              end
+            else
+              raise CanCan::AccessDenied unless model_solution_token_used_on_this_exercise
+            end
+          end
+          ModelSolutionAccessLog.create!(user: current_user, course: course, exercise_name: exercise.name)
+          present(
+            exercise: {
+              id: exercise.id
+            },
+            solution: {
+              files: solution.files
+            }
+          )
+        end
+      end
+    end
+  end
+end

config/routes.rb

@@ -99,6 +99,10 @@
         end
       end
 
+      resources :exercises, only: [] do
+        resources :model_solutions, only: [:index], module: :exercises
+      end
+
       namespace :core, defaults: { format: 'json' } do
         resources :courses, only: [:show] do
           resource :unlock, module: :courses, only: [:create]

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20181213161532) do
+ActiveRecord::Schema.define(version: 20181213163959) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -190,6 +190,17 @@
     t.datetime "updated_at"
   end
 
+  create_table "model_solution_token_useds", force: :cascade do |t|
+    t.integer  "user_id"
+    t.integer  "course_id"
+    t.string   "exercise_name"
+    t.datetime "created_at",    null: false
+    t.datetime "updated_at",    null: false
+  end
+
+  add_index "model_solution_token_useds", ["course_id"], name: "index_model_solution_token_useds_on_course_id", using: :btree
+  add_index "model_solution_token_useds", ["user_id"], name: "index_model_solution_token_useds_on_user_id", using: :btree
+
   create_table "oauth_access_grants", force: :cascade do |t|
     t.integer  "resource_owner_id", null: false
     t.integer  "application_id",    null: false
@@ -455,6 +466,8 @@
   add_foreign_key "feedback_answers", "feedback_questions", on_delete: :cascade
   add_foreign_key "feedback_answers", "submissions", on_delete: :nullify
   add_foreign_key "feedback_questions", "courses", on_delete: :cascade
+  add_foreign_key "model_solution_token_useds", "courses"
+  add_foreign_key "model_solution_token_useds", "users"
   add_foreign_key "reviews", "submissions", on_delete: :cascade
   add_foreign_key "reviews", "users", column: "reviewer_id"
   add_foreign_key "submission_data", "submissions", on_delete: :cascade