add - import validator for organization quota stats

apps/product/validators/quota_stats_validator.py

@@ -0,0 +1,60 @@
+from django.apps import apps
+from django.core.exceptions import ValidationError
+from rest_framework.exceptions import APIException
+
+
+def get_model(app_label, model_name):
+    return apps.get_model(app_label, model_name)
+
+
+class QuotaStatsValidator:
+    """
+    Validator static methods for distribution/sale/quota edits.
+    """
+
+    @staticmethod
+    def _get_stat(quota, organization):
+        organization_quota_stats = get_model("product", "OrganizationQuotaStats")
+        return organization_quota_stats.objects.filter(quota=quota, organization=organization).first()
+
+    @staticmethod
+    def validate_assigner_has_enough(assigner_org, quota, amount, allow_zero=False):
+        """
+        if organization has enough remaining weight
+        """
+        stat = QuotaStatsValidator._get_stat(quota, assigner_org)
+        if not stat:
+            raise APIException(f"Organization {assigner_org} has no quota record for quota {quota}.")
+
+        remaining = getattr(stat, "remaining_amount", None)
+        if remaining is None:
+            # fallback to quota.remaining_weight subtraction from totals
+            raise APIException("remaining_amount field missing in OrganizationQuotaStats.")
+
+        if amount < 0:
+            raise APIException("Amount must be non-negative.")
+
+        if remaining < amount and not allow_zero:
+            raise APIException(
+                f"Assigning {amount} exceeds remaining amount {remaining} for organization {assigner_org}."
+            )
+
+    @staticmethod
+    def validate_distribution_create(assigner_org, assigned_org, quota, amount, parent_distribution=None):
+        # rule: assigner must have enough remaining weight
+        QuotaStatsValidator.validate_assigner_has_enough(assigner_org, quota, amount)
+
+    @staticmethod
+    def validate_distribution_update(assigner_org, assigned_org, quota, old_amount, new_amount,
+                                     parent_distribution=None):
+        # if diff is positive we must check
+        diff = new_amount - (old_amount or 0)
+        if diff > 0:
+            QuotaStatsValidator.validate_assigner_has_enough(assigner_org, quota, diff)
+
+    @staticmethod
+    def validate_distribution_delete(distribution):
+        # اگر already sold (been_sold > 0) نباید حذف شود
+        been_sold = getattr(distribution, "been_sold", None)
+        if been_sold and been_sold > 0:
+            raise ValidationError("Cannot delete distribution: it has sold items.")