feat(rules): add rule function to fetch transactions totals and balance

app/apps/rules/tasks.py

@@ -2,7 +2,6 @@ import decimal
 import logging
 from datetime import datetime, date
 from decimal import Decimal
-from typing import Any
 
 from cachalot.api import cachalot_disabled
 from dateutil.relativedelta import relativedelta
@@ -11,6 +10,7 @@ from procrastinate.contrib.django import app
 from simpleeval import EvalWithCompoundTypes
 
 from apps.accounts.models import Account
+from apps.common.middleware.thread_local import write_current_user, delete_current_user
 from apps.rules.models import (
     TransactionRule,
     TransactionRuleAction,
@@ -21,7 +21,7 @@ from apps.transactions.models import (
     TransactionTag,
     TransactionEntity,
 )
-from apps.common.middleware.thread_local import write_current_user, delete_current_user
+from apps.rules.utils import transactions
 
 logger = logging.getLogger(__name__)
 
@@ -58,6 +58,7 @@ def check_for_transaction_rules(
                 "decimal": decimal.Decimal,
                 "datetime": datetime,
                 "date": date,
+                "transactions": transactions.TransactionsGetter,
             }
 
             names = _get_names(instance)

app/apps/rules/utils/transactions.py

@@ -0,0 +1,58 @@
+import logging
+from decimal import Decimal
+
+from django.db.models import Sum, Value, DecimalField, Case, When, F
+from django.db.models.functions import Coalesce
+
+from apps.transactions.models import (
+    Transaction,
+)
+
+logger = logging.getLogger(__name__)
+
+
+class TransactionsGetter:
+    def __init__(self, **filters):
+        self.__queryset = Transaction.objects.filter(**filters)
+
+    @property
+    def sum(self):
+        return self.__queryset.aggregate(
+            total=Coalesce(
+                Sum("amount"), Value(Decimal("0")), output_field=DecimalField()
+            )
+        )["total"]
+
+    @property
+    def balance(self):
+        return abs(
+            self.__queryset.aggregate(
+                balance=Coalesce(
+                    Sum(
+                        Case(
+                            When(type=Transaction.Type.EXPENSE, then=-F("amount")),
+                            default=F("amount"),
+                            output_field=DecimalField(),
+                        )
+                    ),
+                    Value(Decimal("0")),
+                    output_field=DecimalField(),
+                )
+            )["balance"]
+        )
+
+    @property
+    def raw_balance(self):
+        return self.__queryset.aggregate(
+            balance=Coalesce(
+                Sum(
+                    Case(
+                        When(type=Transaction.Type.EXPENSE, then=-F("amount")),
+                        default=F("amount"),
+                        output_field=DecimalField(),
+                    )
+                ),
+                Value(Decimal("0")),
+                output_field=DecimalField(),
+            )
+        )["balance"]