prvi kod za live uporabu

backend/modules/invoicing/utils.py

@@ -0,0 +1,26 @@
+import datetime
+from django.apps import apps
+from django.db import transaction
+
+def generate_invoice_number():
+    """
+    Generira novi broj fakture u formatu INV-YYYY-XXXX.
+    Koristi transakciju kako bi se spriječilo dupliciranje brojeva.
+    """
+    with transaction.atomic():
+        Invoice = apps.get_model('invoicing', 'Invoice')
+
+        current_year = datetime.date.today().year
+        
+        # Zaključavamo tablicu za čitanje kako bismo izbjegli Race Condition
+        last_invoice = Invoice.objects.filter(
+            invoice_number__startswith=f"INV-{current_year}-"
+        ).select_for_update().order_by('-invoice_number').first()
+
+        if last_invoice:
+            last_num = int(last_invoice.invoice_number.split('-')[-1])
+            new_num = last_num + 1
+        else:
+            new_num = 1
+            
+        return f"INV-{current_year}-{new_num:04d}"