Initial

app/base/signals/__init__.py

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+from app.base.signals.booking import booking_post_save
+from app.base.signals.person import person_post_save
+from app.base.signals.transaction import (
+    transaction_pre_save,
+    transaction_post_save,
+    transaction_pre_delete
+)

app/base/signals/booking.py

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+from django.db.models.signals import post_save
+from django.dispatch import receiver
+
+from app.base.models import Transaction, Booking
+
+
+@receiver(post_save, sender=Booking)
+def booking_post_save(sender, instance: Booking, created: bool, **kwargs):
+    amount = instance.calculated_price
+    with_transaction = instance.end_time and amount
+    description = f'{instance.type.label} ({instance.duration or 0} Min)'
+
+    # Create or update existing Transaction
+    transaction = Transaction.objects.filter(booking=instance).first()
+    if transaction:
+        if with_transaction:
+            transaction.amount = amount
+            transaction.description = description
+            transaction.save()
+        else:
+            transaction.delete()
+
+    elif with_transaction:
+        Transaction.objects.create(
+            account=instance.user.account,
+            amount=amount,
+            description=description,
+            booking=instance,
+        )

app/base/signals/person.py

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+from django.dispatch import receiver
+from django.db.models.signals import post_save
+from app.base.models import Person, Account
+
+
+@receiver(post_save, sender=Person)
+def person_post_save(sender, instance: Person, created: bool, **kwargs):
+    if created:
+        Account.objects.create(user=instance)

app/base/signals/transaction.py

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+from django.dispatch import receiver
+from django.db.models.signals import pre_save, post_save, pre_delete
+from app.base.models import Transaction
+
+
+@receiver(pre_save, sender=Transaction)
+def transaction_pre_save(sender, instance: Transaction, **kwargs):
+    if instance.pk:
+        pre_edit = Transaction.objects.get(pk=instance.pk)
+
+        if pre_edit.amount != instance.amount:
+            delta = pre_edit.amount - instance.amount
+            account = instance.account
+            account.balance = account.balance - delta
+            account.save()
+
+
+@receiver(post_save, sender=Transaction)
+def transaction_post_save(sender, instance: Transaction, created, **kwargs):
+    if created:
+        instance.account.balance += instance.amount
+        instance.account.save()
+
+
+@receiver(pre_delete, sender=Transaction)
+def transaction_pre_delete(sender, instance: Transaction, **kwargs):
+    instance.account.balance -= instance.amount
+    instance.account.save()