Show the size of an IP range

We do this catch massive ranges when verifying a provider request.

apps/accounts/admin.py

@@ -1350,6 +1350,9 @@ class ProviderRequestIPRangeInline(AdminOnlyTabularInline):
     model = ProviderRequestIPRange
     extra = 0
 
+    readonly_fields = ["ip_range_size"]
+    fields = ["start", "end", "ip_range_size"]
+
 
 class ProviderRequestEvidenceInline(AdminOnlyTabularInline):
     model = ProviderRequestEvidence

apps/accounts/models/provider_request.py

@@ -23,6 +23,8 @@
     Service,
 )
 
+import ipaddress
+
 logger = logging.getLogger(__name__)  # noqa
 
 
@@ -407,6 +409,23 @@ class ProviderRequestIPRange(models.Model):
     def __str__(self) -> str:
         return f"{self.start} - {self.end}"
 
+    def ip_range_size(self) -> int:
+        """
+        Return the size of the IP range, based on the start and end ip address.
+        """
+        if not self.start or not self.end:
+            return 0
+
+        # Convert string IP addresses to IP address objects
+        start_ip = ipaddress.ip_address(self.start)
+        end_ip = ipaddress.ip_address(self.end)
+
+        # Calculate the difference and add 1 (if start and end IP addresses are the same, we still want it to show as 1)
+        return int(end_ip) - int(start_ip) + 1
+
+    # Add a short description for the admin
+    ip_range_size.short_description = "IP Range Size"
+
     def clean(self) -> None:
         """
         Validates an IP range.
@@ -419,7 +438,12 @@ def clean(self) -> None:
         according to the ModelForm validation logic.
         """
         if self.start and self.end:
-            validate_ip_range(self.start, self.end)
+            try:
+                validate_ip_range(self.start, self.end)
+            except ValueError as e:
+                raise ValidationError({"start": e})
+            except TypeError as e:
+                raise ValidationError({"Mismatching IP ranges": e})
 
 
 class ProviderRequestEvidence(models.Model):

apps/accounts/tests/test_provider_ip_range.py

@@ -0,0 +1,74 @@
+import pytest
+from ..models import ProviderRequest, ProviderRequestIPRange
+
+# add import for django validation error
+from django.core.exceptions import ValidationError
+
+
+@pytest.fixture
+def ip_range():
+    return ProviderRequestIPRange()
+
+
+@pytest.mark.parametrize(
+    "start_ip,end_ip,expected_size",
+    [
+        # IPv4 test cases
+        ("192.168.1.1", "192.168.1.1", 1),  # Single IP
+        ("192.168.1.1", "192.168.1.10", 10),  # Small range
+        ("192.168.1.0", "192.168.1.255", 256),  # Full subnet
+        ("10.0.0.0", "10.0.1.0", 257),  # Across subnet boundary
+        # IPv6 test cases
+        ("2001:db8::1", "2001:db8::1", 1),  # Single IP
+        ("2001:db8::1", "2001:db8::10", 16),  # Small range
+        ("2001:db8::0", "2001:db8::ff", 256),  # Larger range
+        # Edge cases
+        ("0.0.0.0", "0.0.0.255", 256),  # Start of IPv4 range
+        ("255.255.255.0", "255.255.255.255", 256),  # End of IPv4 range
+    ],
+)
+def test_ip_range_size_calculation(ip_range, start_ip, end_ip, expected_size):
+    ip_range.start = start_ip
+    ip_range.end = end_ip
+    assert ip_range.ip_range_size() == expected_size
+
+
+def test_ip_range_size_with_empty_values(ip_range):
+    # Test with no values set
+    assert ip_range.ip_range_size() == 0
+
+    # Test with only start IP
+    ip_range.start = "192.168.1.1"
+    assert ip_range.ip_range_size() == 0
+
+    # Test with only end IP
+    ip_range.start = None
+    ip_range.end = "192.168.1.10"
+    assert ip_range.ip_range_size() == 0
+
+
+# @pytest.mark.django_db
+# def test_full_model_creation():
+#     """Test creating and saving a model instance"""
+#     provider_request = ProviderRequest.objects.create()  # Add necessary fields
+#     ip_range = ProviderRequestIPRange.objects.create(
+#         start="192.168.1.1", end="192.168.1.10", request=provider_request
+#     )
+#     assert ip_range.ip_range_size() == 10
+#     assert str(ip_range) == "192.168.1.1 - 192.168.1.10"
+
+
+@pytest.mark.parametrize(
+    "start_ip,end_ip",
+    [
+        ("192.168.1.10", "192.168.1.1"),  # End IP before start IP
+        ("invalid_ip", "192.168.1.1"),  # Invalid IP format
+        ("192.168.1.1", "invalid_ip"),  # Invalid IP format
+        ("2001:db8::1", "192.168.1.1"),  # Mixed IPv6 and IPv4
+    ],
+)
+def test_invalid_ip_ranges(ip_range, start_ip, end_ip):
+    ip_range.start = start_ip
+    ip_range.end = end_ip
+    with pytest.raises(ValidationError):
+        ip_range.clean()