Add NormalCase model, views, filters, and templates for managing normal cases

atlas/models.py

@@ -611,6 +611,83 @@ class Case(models.Model, AuthorMixin, QuestionMixin):
 
         return json.dumps(results)
 
+
+class NormalCase(models.Model):
+    """Marks a Case as a 'normal' example used in the Atlas normals section.
+
+    We store a nearest-year age (age_years) and optional primary
+    examination/modality to make filtering simple and fast. A OneToOne
+    relation keeps normal-specific fields separate from the main Case
+    object and is non-destructive.
+    """
+    case = models.OneToOneField(
+        Case,
+        on_delete=models.CASCADE,
+        related_name="normal_case",
+        help_text="The Case that is marked as a normal example.",
+    )
+
+    age_years = models.PositiveSmallIntegerField(
+        null=True,
+        blank=True,
+        validators=[MinValueValidator(0), MaxValueValidator(150)],
+        help_text="Age of the patient at scan in years (rounded to nearest year).",
+    )
+
+    examination = models.ForeignKey(
+        Examination,
+        null=True,
+        blank=True,
+        on_delete=models.SET_NULL,
+        related_name="normal_cases",
+        help_text="Primary examination for this normal case (optional).",
+    )
+
+    modality = models.ForeignKey(
+        Modality,
+        null=True,
+        blank=True,
+        on_delete=models.SET_NULL,
+        related_name="normal_cases",
+        help_text="Primary modality for this normal case (optional).",
+    )
+
+    added_by = models.ForeignKey(
+        settings.AUTH_USER_MODEL,
+        null=True,
+        blank=True,
+        on_delete=models.SET_NULL,
+        related_name="added_normals",
+    )
+
+    added_date = models.DateTimeField(default=timezone.now)
+
+    notes = models.TextField(null=True, blank=True)
+
+    class Meta:
+        ordering = ["-added_date"]
+
+    def __str__(self):
+        return f"Normal: {self.case} ({self.age_years or 'unknown'}y)"
+
+    def get_absolute_url(self):
+        return self.case.get_absolute_url()
+
+    def save(self, *args, **kwargs):
+        # If examination/modality not specified, try to infer from the first series
+        try:
+            if (self.examination is None or self.modality is None) and self.case.series.exists():
+                first_series = self.case.series.first()
+                if self.examination is None and getattr(first_series, 'examination', None) is not None:
+                    self.examination = first_series.examination
+                if self.modality is None and getattr(first_series, 'modality', None) is not None:
+                    self.modality = first_series.modality
+        except Exception:
+            # Be defensive: if anything goes wrong whilst inferring, continue and save as-is
+            pass
+
+        super().save(*args, **kwargs)
+
 def extract_image_dicom_json_from_ds(ds, url, image_index):
     to_keep = [
         "Columns",