First pass attempt at generation exceptions

apps/submissions/api.py

@@ -2,42 +2,59 @@
 Public interface for the submissions app.
 
 """
-from datetime import datetime
-
+from django.db import DatabaseError
 from django.utils.encoding import force_unicode
 
 from submissions.serializers import SubmissionSerializer
 from submissions.models import Submission, StudentItem, SubmissionStruct
 
 
-def create_submission(student_item_struct, answer, submitted_at=None, attempt_number=None):
+class SubmissionAccessError(Exception):
+    pass
+
+class SubmissionNotFoundError(Exception):
+    pass
+
+
+def create_submission(student_item_struct, answer, submitted_at=None,
+                      attempt_number=None):
     """Creates a submission for evaluation.
 
     Generic means by which to submit an answer for evaluation.
 
     Args:
-        student_item_struct (StudentItemStruct): The student_item this submission is associated with. This is used to
-            determine which course, student, and location this submission belongs to.
+        student_item_struct (StudentItemStruct): The student_item this
+            submission is associated with. This is used to determine which
+            course, student, and location this submission belongs to.
         answer (str): The answer given by the student to be evaluated.
-        submitted_at (date): The date in which this submission was submitted. If not specified, defaults to the current
-            date.
-        attempt_number (int): A student may be able to submit multiple attempts per question. This allows the designated
-            attempt to be overridden. If the attempt is not specified, it will be incremented by the number of
-            submissions associated with this student_item.
+        submitted_at (date): The date in which this submission was submitted.
+            If not specified, defaults to the current date.
+        attempt_number (int): A student may be able to submit multiple attempts
+            per question. This allows the designated attempt to be overridden.
+            If the attempt is not specified, it will be incremented by the
+            number of submissions associated with this student_item.
 
     Returns:
         SubmissionStruct: A representation of the created Submission.
 
+    Raises:
+        SubmissionAccessError: Raised when information regarding the student
+            item cannot be accessed or the submission cannot be saved.
+
     """
-    student_item_model, _ = StudentItem.objects.get_or_create(
-        student_id=student_item_struct.student_id,
-        course_id=student_item_struct.course_id,
-        item_id=student_item_struct.item_id,
-        item_type=student_item_struct.item_type,
-    )
+    try:
+        student_item_model, _ = StudentItem.objects.get_or_create(
+            student_item_struct._asdict())
+    except DatabaseError as err:
+        raise SubmissionAccessError(err)
+
 
     if attempt_number is None:
-        submissions = Submission.objects.filter(student_item=student_item_model)[:0]
+        try:
+            submissions = Submission.objects.filter(
+                student_item=student_item_model)[:0]
+        except DatabaseError as err:
+            raise SubmissionAccessError(err)
         attempt_number = submissions[0].attempt_number + 1 if submissions else 1
 
     model_kwargs = {
@@ -48,38 +65,56 @@ def create_submission(student_item_struct, answer, submitted_at=None, attempt_nu
     if submitted_at:
         model_kwargs["submitted_at"] = submitted_at
 
-    submission = Submission.objects.create(**model_kwargs)
+    try:
+        submission = Submission.objects.create(**model_kwargs)
+    except DatabaseError as err:
+        raise SubmissionAccessError(err)
     return SubmissionStruct(**SubmissionSerializer(submission).data)
 
 
 def get_submissions(student_item_struct, limit=None):
-    """Retrieves the specified submission.
+    """Retrieves the submissions for the specified student item,
+    ordered by most recent submitted date.
 
-    Returns the requested submission relative to the student item. Exception thrown if no submission is found relative
-    to this location.
+    Returns the submissions relative to the specified student item. Exception
+    thrown if no submission is found relative to this location.
 
     Args:
-        student_item_struct (StudentItemStruct): The location of the problem this submission is associated with, as
-            defined by a course, student, and item.
-        limit (int): Optional parameter for limiting the returned number of submissions associated with this student
-            item. If not specified, all associated submissions are returned.
+        student_item_struct (StudentItemStruct): The location of the problem
+            this submission is associated with, as defined by a course, student,
+            and item.
+        limit (int): Optional parameter for limiting the returned number of
+            submissions associated with this student item. If not specified, all
+            associated submissions are returned.
 
     Returns:
-        List SubmissionStruct: A list of SubmissionStruct for the associated student item.
+        List SubmissionStruct: A list of SubmissionStruct for the associated
+            student item.
+
+    Raises:
+        SubmissionAccessError: Raised when the associated student item cannot
+            be accessed.
+        SubmissionNotFoundError: Raised when a submission cannot be found for
+            the associated student item.
 
     """
-    student_item_model, _ = StudentItem.objects.get_or_create(
-        student_id=student_item_struct.student_id,
-        course_id=student_item_struct.course_id,
-        item_id=student_item_struct.item_id,
-        item_type=student_item_struct.item_type,
-    )
-
-    submission_models = Submission.objects.filter(student_item=student_item_model)
+    try:
+        student_item_model, _ = StudentItem.objects.get_or_create(
+            student_item_struct._asdict())
+    except DatabaseError as err:
+        raise SubmissionAccessError(err)
+
+    try:
+        submission_models = Submission.objects.filter(
+            student_item=student_item_model)
+    except DatabaseError:
+        raise SubmissionNotFoundError()
+
     if limit:
         submission_models = submission_models[:limit]
 
-    return [SubmissionStruct(**SubmissionSerializer(submission).data) for submission in submission_models]
+    return [SubmissionStruct(**SubmissionSerializer(submission).data) for
+            submission in submission_models]
 
 
 def get_score(student_item):

apps/submissions/tests/test_api.py

@@ -47,7 +47,8 @@ class TestApi(TestCase):
         submissions = get_submissions(STUDENT_ITEM)
         self._assert_submission(submissions[0], ANSWER_ONE, 1, 2)
 
-    def _assert_submission(self, submission, expected_answer, expected_item, expected_attempt):
+    def _assert_submission(self, submission, expected_answer, expected_item,
+                           expected_attempt):
         self.assertIsNotNone(submission)
         self.assertEqual(submission.answer, expected_answer)
         self.assertEqual(submission.student_item, expected_item)