Delete learner's state in staff debug

WIP
- implement the callback clear_student_state
- add a new submission to indicate existing answers are deleted
- add (but commented out) code to partially support revising score
manually.  But full support will require adding logic to persist the
score within xblock
- fix issue with same explanation displayed multiple times in Step 2

ubcpi/answer_pool.py

@@ -227,48 +227,46 @@ def get_other_answers_simple(pool, seeded_answers, get_student_item_dict, num_re
     ret = []
     # clean up answers so that all keys are int
     pool = {int(k): v for k, v in pool.items()}
-    total_in_pool = len(seeded_answers)
     merged_pool = convert_seeded_answers(seeded_answers)
     student_id = get_student_item_dict()['student_id']
     # merge the dictionaries in the answer dictionary
     for key in pool:
-        total_in_pool += len(pool[key])
-        # if student_id has value, we assume the student just submitted an answer. So removing it
-        # from total number in the pool
-        if student_id in pool[key].keys():
-            total_in_pool -= 1
-        if key in merged_pool:
-            merged_pool[key].update(pool[key].items())
-        else:
-            merged_pool[key] = pool[key]
-
-    # remember which option+student_id is selected, so that we don't have duplicates in the result
-    selected = []
+        merged_pool.setdefault(key, {})
+        merged_pool[key].update(pool[key].items())
+        # Pop student's own answer, if exists
+        merged_pool[key].pop(student_id, None)
 
-    # loop until we have enough answers to return
-    while len(ret) < min(num_responses, total_in_pool):
+    # loop until we have enough answers to return or when there is nothing more to return
+    while len(ret) < num_responses and merged_pool:
         for option, students in merged_pool.items():
-            student = student_id
-            i = 0
-            while (student == student_id or i > 100) and (str(option) + student) not in selected:
-                # retry until we got a different one or after 100 retries
-                # we are suppose to get a different student answer or a seeded one in a few tries
-                # as we have at least one seeded answer for each option in the algo. And it is not
-                # suppose to overflow i order to break the loop
+            rationale = None
+            while students:
                 student = random.choice(students.keys())
-                i += 1
-            selected.append(str(option)+student)
-            if student.startswith('seeded'):
-                # seeded answer, get the rationale from local
-                rationale = students[student]
-            else:
-                student_item = get_student_item_dict(student)
-                submission = sas_api.get_answers_for_student(student_item)
-                rationale = submission.get_rationale(0)
-            ret.append({'option': option, 'rationale': rationale})
+                content = students[student]
+                # remove the choosen answer from pool
+                students.pop(student, None)
+
+                if student.startswith('seeded'):
+                    # seeded answer, get the rationale from local
+                    rationale = content
+                else:
+                    student_item = get_student_item_dict(student)
+                    submission = sas_api.get_answers_for_student(student_item)
+                    # Make sure the option is still the one we want.
+                    # It may have changed (e.g. instructor deleted the student state
+                    # and the student re-submitted a diff answer)
+                    if submission.has_revision(0) and submission.get_vote(0) == option:
+                        rationale = submission.get_rationale(0)
+
+                if rationale:
+                    ret.append({'option': option, 'rationale': rationale})
+                    break
+
+            if not students:
+                merged_pool.pop(option, None)
 
             # check if we have enough answers
-            if len(ret) >= min(num_responses, total_in_pool):
+            if len(ret) >= num_responses:
                 break
 
     return {"answers": ret}
@@ -316,8 +314,11 @@ def get_other_answers_random(pool, seeded_answers, get_student_item_dict, num_re
         else:
             student_item = get_student_item_dict(student)
             submission = sas_api.get_answers_for_student(student_item)
-            rationale = submission.get_rationale(0)
-            option = submission.get_vote(0)
+            if submission.has_revision(0):
+                rationale = submission.get_rationale(0)
+                option = submission.get_vote(0)
+            else:
+                continue
         ret.append({'option': option, 'rationale': rationale})
 
     return {"answers": ret}

ubcpi/persistence.py

@@ -17,6 +17,8 @@
 """
 
 ANSWER_LIST_KEY = 'answers'
+DELETE_INDICATOR = 'deleted'
+REQUEST_USER_ID_KEY = 'requesting_user_id'
 
 VOTE_KEY = 'vote'
 RATIONALE_KEY = 'rationale'
@@ -39,6 +41,8 @@ def get_answers_for_student(student_item):
 
     latest_submission = submissions[0]
     latest_answer_item = latest_submission.get('answer', {})
+    if latest_answer_item.get(DELETE_INDICATOR, False):
+        return Answers()
     return Answers(latest_answer_item.get(ANSWER_LIST_KEY, []))
 
 
@@ -59,6 +63,19 @@ def add_answer_for_student(student_item, vote, rationale):
         ANSWER_LIST_KEY: answers.get_answers_as_list()
     })
 
+def delete_answer_for_student(student_item, requesting_user_id):
+    """
+    Create a new submission to indicate student's answer is deleted
+
+    Args:
+        student_item (dict): The location of the problem this submission is
+            associated with, as defined by a course, student, and item.
+        requesting_user_id: The user that is requesting to delete student answer
+    """
+    sub_api.create_submission(student_item, {
+        DELETE_INDICATOR: True,
+        REQUEST_USER_ID_KEY: requesting_user_id,
+    })
 
 class Answers:
     """

ubcpi/ubcpi.py

@@ -11,6 +11,8 @@
 from webob import Response
 from xblock.core import XBlock
 from xblock.exceptions import JsonHandlerError
+# For supporting manual revision of scores.  Commented out for now.
+# from xblock.scorable import ScorableXBlockMixin, Score
 from xblock.fields import Scope, String, List, Dict, Integer, DateTime, Float
 from xblock.fragment import Fragment
 from xblockutils.publish_event import PublishEventMixin
@@ -256,8 +258,6 @@ class PeerInstructionXBlock(XBlock, MissingDataFetcherMixin, PublishEventMixin):
         help=_("The algorithm for selecting which answers to be presented to students"),
     )
 
-    # Declare that we are not part of the grading System. Disabled for now as for the concern about the loading
-    # speed of the progress page.
     has_score = True
 
     start = DateTime(
@@ -293,6 +293,57 @@ def max_score(self):
         """
         return 1
 
+    # def calculate_score(self):
+    #     answers = self.get_answers_for_student()
+    #     if answers.has_revision(0) and answers.has_revision(1):
+    #         return Score(1, 1)
+    #     return Score(0, 1)
+    #
+    # def set_score(self, score):
+    #     # TODO persisting score
+    #     pass
+    #
+    # def get_score(self):
+    #     # TODO Since we are not persisting score, always return 1.
+    #     # That means the Overriding Score function will always set the score to 1
+    #     # Instructors can reset the score to 0 by deleting learner's state
+    #     return Score(1, 1)
+
+    def clear_student_state(self, user_id, course_id, item_id, requesting_user_id):
+        """
+        Being notified that student state is going to be deleted.  Mark student's
+        submissions as deleted
+        """
+        student_item = dict(
+            student_id=user_id,
+            item_id=item_id,
+            course_id=course_id,
+            item_type='ubcpi'
+        )
+
+        # TODO currently not possible to revise the stats as they are defined with scope Scope.user_state_summary.
+        # The stats are not available when clear_student_state is called
+        # answers = sas_api.get_answers_for_student(student_item)
+        # stats = self.get_current_stats()
+        # if answers.has_revision(0):
+        #     num_resp = stats['original'].setdefault(answers.get_vote(0), 0)
+        #     if num_resp > 0:
+        #         stats['original'][answers.get_vote(0)] = num_resp - 1
+        # if answers.has_revision(1):
+        #     num_resp = stats['revised'].setdefault(answers.get_vote(1), 0)
+        #     if num_resp > 0:
+        #         stats['revised'][answers.get_vote(1)] = num_resp - 1
+
+        # mark existing submission as deleted
+        sas_api.delete_answer_for_student(student_item, requesting_user_id)
+
+    # def has_submitted_answer(self):
+    #     answers = self.get_answers_for_student()
+    #     return answers.has_revision(0) and answers.has_revision(1)
+    #
+    # def publish_grade(self):
+    #     self._publish_grade(self.get_score())
+
     def studio_view(self, context=None):
         """
         view function for studio edit