feat: start can_allocate() implementation

enterprise_access/apps/content_assignments/api.py

@@ -0,0 +1,43 @@
+"""
+Primary Python API for interacting with Assignment
+records and business logic.
+"""
+from django.db.models import Sum
+
+from .constants import LearnerContentAssignmentStateChoices
+from .models import LearnerContentAssignment
+
+
+def get_assignments_for_policy(
+    subsidy_access_policy,
+    state=LearnerContentAssignmentStateChoices.ALLOCATED,
+    learner_emails=None,
+):
+    """
+    Returns a queryset of all ``LearnerContentAssignment`` records
+    for the given policy, optionally filtered to only those
+    associated with the given ``learner_emails``.
+    """
+    queryset = LearnerContentAssignment.objects.select_related(
+        'assignment_policy',
+    ).filter(
+        assignment_policy=subsidy_access_policy,
+        state=state,
+    )
+    if learner_emails:
+        queryset = queryset.filter(
+            learner_email__in=learner_emails,
+        )
+    return queryset
+
+
+def get_allocated_quantity_for_policy(subsidy_access_policy):
+    """
+    Returns a float representing the total quantity, in USD cents, currently allocated
+    via Assignments for the given policy.
+    """
+    assignments_queryset = get_assignments_for_policy(subsidy_access_policy)
+    aggregate = assignments_queryset.aggregate(
+        total_quantity=Sum('content_quantity'),
+    )
+    return aggregate['total_quantity']

enterprise_access/apps/content_assignments/models.py

@@ -7,8 +7,6 @@
 from django_extensions.db.models import TimeStampedModel
 from simple_history.models import HistoricalRecords
 
-from enterprise_access.apps.subsidy_access_policy.models import SubsidyAccessPolicy
-
 from .constants import LearnerContentAssignmentStateChoices
 
 
@@ -25,7 +23,7 @@ class AssignmentPolicy(TimeStampedModel):
         unique=True,
     )
     subsidy_access_policy = models.ForeignKey(
-        SubsidyAccessPolicy,
+        'subsidy_access_policy.SubsidyAccessPolicy',
         related_name="assignment_policy",
         on_delete=models.CASCADE,
         db_index=True,

enterprise_access/apps/subsidy_access_policy/models.py

@@ -15,6 +15,7 @@
 from edx_django_utils.cache.utils import get_cache_key
 
 from enterprise_access.apps.api_client.lms_client import LmsApiClient
+from enterprise_access.apps.content_assignments import api as assignments_api
 
 from .constants import (
     CREDIT_POLICY_TYPE_PRIORITY,
@@ -809,3 +810,49 @@ def can_redeem(self, lms_user_id, content_key, skip_customer_user_check=False):
 
     def redeem(self, lms_user_id, content_key, all_transactions, metadata=None):
         raise NotImplementedError
+
+    def can_allocate(self, number_of_learners, content_key, content_price_cents):
+        """
+        """
+        # inactive policy
+        if not self.active:
+            return (False, REASON_POLICY_EXPIRED)
+
+        # no content key in catalog
+        if not self.catalog_contains_content_key(content_key):
+            return (False, REASON_CONTENT_NOT_IN_CATALOG)
+
+        if not self.is_subsidy_active:
+            return (False, REASON_SUBSIDY_EXPIRED)
+
+        # Determine total cost, in cents, of content to potentially allocated
+        total_price_cents = number_of_learners * content_price_cents
+
+        # Determine total amount, in cents, already transacted via this policy.
+        # This is a number <= 0
+        spent_amount_cents = self.aggregates_for_policy().get('total_quantity') or 0
+
+        # Determine total amount, in cents, of assignments already
+        # allocated via this policy. This is a number <= 0
+        total_allocated_assignments_cents = assignments_api.get_allocated_quantity_for_policy(self)
+        total_allocated_and_spent_cents = spent_amount_cents + total_allocated_assignments_cents
+
+        # Use all of these pieces to ensure that the assignments to potentially
+        # allocate won't exceed the remaining balance of the related subsidy.
+        if self.content_would_exceed_limit(
+            total_allocated_and_spent_cents,
+            self.subsidy_balance(),
+            total_price_cents,
+        ):
+            return (False, REASON_NOT_ENOUGH_VALUE_IN_SUBSIDY)
+
+        # Lastly, use all of these pieces to ensure that the assignments to potentially
+        # allocate won't exceed the spend limit of this policy
+        if self.content_would_exceed_limit(
+            total_allocated_and_spent_cents,
+            self.spend_limit,
+            total_price_cents,
+        ):
+            return (False, REASON_POLICY_SPEND_LIMIT_REACHED)
+
+        return (True, None)

enterprise_access/apps/subsidy_access_policy/tests/factories.py

@@ -9,6 +9,7 @@
 
 from enterprise_access.apps.subsidy_access_policy.constants import AccessMethods
 from enterprise_access.apps.subsidy_access_policy.models import (
+    AssignedLearnerCreditAccessPolicy,
     PerLearnerEnrollmentCreditAccessPolicy,
     PerLearnerSpendCreditAccessPolicy
 )
@@ -47,3 +48,16 @@ class PerLearnerSpendCapLearnerCreditAccessPolicyFactory(SubsidyAccessPolicyFact
 
     class Meta:
         model = PerLearnerSpendCreditAccessPolicy
+
+
+class AssignedLearnerCreditAccessPolicyFactory(SubsidyAccessPolicyFactory):
+    """
+    Test factory for the `AssignedLearnerCreditAccessPolicy` model.
+    """
+
+    class Meta:
+        model = AssignedLearnerCreditAccessPolicy
+
+    access_method = AccessMethods.ASSIGNED
+    per_learner_spend_limit = None
+    per_learner_enrollment_limit = None