Implement _priority_weight_case() function

Author: AAdewunmi

policylens/apps/claims/queue.py

@@ -0,0 +1,44 @@
+# path: policylens/apps/claims/queue.py
+"""
+Queue building logic for ops review.
+
+Ordering rules (Week 3):
+1. SLA breached first
+2. SLA due soon (within N hours) next
+3. Higher priority first
+4. Older claims first (created_at ascending)
+
+Filters:
+- status (optional)
+- priority (optional)
+- sla: breached | due_soon | ok (optional)
+"""
+
+from __future__ import annotations
+
+from datetime import timedelta
+
+from django.db.models import Case, IntegerField, Q, Value, When
+from django.utils import timezone
+
+from apps.claims.models import Claim
+
+
+DUE_SOON_WINDOW = timedelta(hours=6)
+
+PRIORITY_WEIGHT = {
+    Claim.Priority.HIGH: 3,
+    Claim.Priority.NORMAL: 2,
+    Claim.Priority.LOW: 1,
+}
+
+
+def _priority_weight_case() -> Case:
+    """Return a DB CASE expression for priority weighting."""
+    return Case(
+        When(priority=Claim.Priority.HIGH, then=Value(PRIORITY_WEIGHT[Claim.Priority.HIGH])),
+        When(priority=Claim.Priority.NORMAL, then=Value(PRIORITY_WEIGHT[Claim.Priority.NORMAL])),
+        When(priority=Claim.Priority.LOW, then=Value(PRIORITY_WEIGHT[Claim.Priority.LOW])),
+        default=Value(PRIORITY_WEIGHT[Claim.Priority.NORMAL]),
+        output_field=IntegerField(),
+    )