Fix relation between MultipleChoiceOption and FeedbackOption

When a MultipleChoiceOption is created via the API call PUT /mult-choice, a new FeedbackOption is now automatically inserted into the database that links to the same problem as the MultipleChoiceOption.

The response of PUT /mult-choice will now contain an mc_id that shows the ID of the new MultipleChoiceQuestion and a feedback_id with the ID of the new FeedbackOption.

The relation between MultipleChoiceOption and Problem is now removed. A new relation from FeedbackOption to MultipleChoiceOption is created. However, it is still possible to use problem.mc_options with a hybrid attribute that essentially runs a query in the background.

TODO:

• Ensure that if a FeedbackOption is deleted, the related MultipleChoiceOption is also deleted.

Closes #35 (closed) and #36 (closed).

zesje/api/mult_choice.py

 from flask_restful import Resource, reqparse
 
-from ..database import db, MultipleChoiceOption
+from ..database import db, MultipleChoiceOption, FeedbackOption
 
 
-def set_mc_data(mc_entry, name, x, y, mc_type, problem_id, feedback_id, label):
+def set_mc_data(mc_entry, name, x, y, mc_type, feedback_id, label):
     """Sets the data of a MultipleChoiceOption ORM object.
 
     Parameters:
     -----------
     mc_entry: The MultipleChoiceOption object
+    name: The name of the MultipleChoiceOption widget
     x: the x-position of the MultipleChoiceOption object.
     y: the y-position of the MultipleChoiceOption object.
-    problem_id: the problem the MultipleChoiceOption refers to
+    type: the polymorphic type used to distinguish the MultipleChoiceOption widget
+        from other widgets
     feedback_id: the feedback the MultipleChoiceOption refers to
     label: label for the checkbox that this MultipleChoiceOption represents
     """
@@ -19,7 +21,6 @@ def set_mc_data(mc_entry, name, x, y, mc_type, problem_id, feedback_id, label):
     mc_entry.x = x
     mc_entry.y = y
     mc_entry.type = mc_type
-    mc_entry.problem_id = problem_id
     mc_entry.feedback_id = feedback_id
     mc_entry.label = label
 
@@ -33,8 +34,7 @@ class MultipleChoice(Resource):
     put_parser.add_argument('x', type=int, required=True)
     put_parser.add_argument('y', type=int, required=True)
     put_parser.add_argument('label', type=str, required=False)
-    put_parser.add_argument('problem_id', type=int, required=True)
-    put_parser.add_argument('feedback_id', type=int, required=True)
+    put_parser.add_argument('problem_id', type=int, required=True)  # Used for FeedbackOption
 
     def put(self, id=None):
         """Adds or updates a multiple choice option to the database
@@ -42,6 +42,10 @@ class MultipleChoice(Resource):
         If the parameter id is not present, a new multiple choice question
         will be inserted with the data provided in the request body.
 
+        For each new multiple choice option, a feedback option that links to
+        the multiple choice option is inserted into the database. The new
+        feedback option also refers to same problem as the MultipleChoiceOption
+
         Parameters
         ----------
             id: The id of the multiple choice option
@@ -55,20 +59,26 @@ class MultipleChoice(Resource):
         y = args['y']
         label = args['label']
         problem_id = args['problem_id']
-        feedback_id = args['feedback_id']
 
         # TODO: Set type here or add to request?
         mc_type = 'mcq_widget'
 
         if not id:
+            # Insert new empty feedback option that links to the same problem
+            new_feedback_option = FeedbackOption(problem_id=problem_id, text='')
+            db.session.add(new_feedback_option)
+            db.session.commit()
+
             # Insert new entry into the database
             mc_entry = MultipleChoiceOption()
-            set_mc_data(mc_entry, name, x, y, mc_type, problem_id, feedback_id, label)
+            set_mc_data(mc_entry, name, x, y, mc_type, new_feedback_option.id, label)
 
             db.session.add(mc_entry)
             db.session.commit()
 
-            return dict(status=200, message=f'New multiple choice question with id {mc_entry.id} inserted'), 200
+            return dict(status=200, mult_choice_id=mc_entry.id, feedback_id=new_feedback_option.id,
+                        message=f'New multiple choice question with id {mc_entry.id} inserted. '
+                        + f'New feedback option with id {new_feedback_option.id} inserted.'), 200
 
         # Update existing entry otherwise
         mc_entry = MultipleChoiceOption.query.get(id)
@@ -76,7 +86,7 @@ class MultipleChoice(Resource):
         if not mc_entry:
             return dict(status=404, message=f"Multiple choice question with id {id} does not exist"), 404
 
-        set_mc_data(mc_entry, name, x, y, mc_type, problem_id, feedback_id, label)
+        set_mc_data(mc_entry, name, x, y, mc_type, label)
         db.session.commit()
 
         return dict(status=200, message=f'Multiple choice question with id {id} updated'), 200
@@ -103,20 +113,21 @@ class MultipleChoice(Resource):
             'x': mult_choice.x,
             'y': mult_choice.y,
             'type': mult_choice.type,
-            'problem_id': mult_choice.problem_id
+            'feedback_id': mult_choice.feedback_id
         }
 
         # Nullable database fields
         if mult_choice.label:
             json['label'] = mult_choice.label
 
-        if mult_choice.feedback_id:
-            json['feedback_id'] = mult_choice.feedback_id
-
         return json
 
     def delete(self, id):
-        """Deletes a multiple choice option from the database
+        """Deletes a multiple choice option from the database.
+        Also deletes the associated feedback option with this multiple choice option.
+
+        An error will be thrown if the user tries to delete a feedback option
+        associated with a multiple choice option in a finalized exam.
 
         Parameters
         ----------
@@ -131,7 +142,20 @@ class MultipleChoice(Resource):
         if not mult_choice:
             return dict(status=404, message=f'Multiple choice question with id {id} does not exist.'), 404
 
+        if not mult_choice.feedback:
+            return dict(status=404, message=f'Multiple choice question with id {id}'
+                        + ' is not associated with a feedback option.'), 404
+
+        # Check if the exam is finalized, do not delete the multiple choice option otherwise
+        exam = mult_choice.feedback.problem.exam
+
+        if exam.finalized:
+            return dict(status=401, message='Cannot delete feedback option'
+                        + ' attached to a multiple choice option in a finalized exam.'), 401
+
         db.session.delete(mult_choice)
+        db.session.delete(mult_choice.feedback)
         db.session.commit()
 
-        return dict(status=200, message=f'Multiple choice question with id {id} deleted.'), 200
+        return dict(status=200, message=f'Multiple choice question with id {id} deleted.'
+                    + f'Feedback option with id {mult_choice.feedback_id} deleted.'), 200