Wrap balance calculations in a database transaction

Author: akadusei

CHANGELOG.md

@@ -10,6 +10,9 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ### Added
 - Make `Currency` JSON-serializable
 
+### Fixed
+- Wrap balance calculations in a database transaction
+
 ## [0.21.0] - 2025-06-05
 
 ### Added

src/bill/models/mixins/parent_net_amount.cr

@@ -9,8 +9,13 @@ module Bill::ParentNetAmount
     end
 
     def net_amount! : Amount
-      sum = amount!
-      sum -= self.credit_notes_amount! if responds_to?(:credit_notes_amount!)
+      sum = Amount.new(0)
+
+      self.class.database.transaction do
+        sum += amount!
+        sum -= self.credit_notes_amount! if responds_to?(:credit_notes_amount!)
+      end
+
       sum
     end
 

src/bill/utilities/mixins/invoices_ledger.cr

@@ -56,7 +56,12 @@ module Bill::InvoicesLedger
 
       # :ditto:
       def over_owing!(user)
-        balance = @ledger.balance!(user) - amount_not_overdue!(user)
+        balance = Amount.new(0)
+
+        user.class.database.transaction do
+          balance += @ledger.balance!(user) - amount_not_overdue!(user)
+        end
+
         balance if balance.debit?
       end