Fix duplicate visited regions

backend/server/worldtravel/models.py

@@ -1,5 +1,6 @@
 from django.db import models
 from django.contrib.auth import get_user_model
+from django.core.exceptions import ValidationError
 
 
 User = get_user_model()
@@ -57,3 +58,8 @@ class VisitedRegion(models.Model):
 
     def __str__(self):
         return f'{self.region.name} ({self.region.country.country_code}) visited by: {self.user_id.username}'
+    
+    def save(self, *args, **kwargs):
+        if VisitedRegion.objects.filter(user_id=self.user_id, region=self.region).exists():
+            raise ValidationError("Region already visited by user.")
+        super().save(*args, **kwargs)

backend/server/worldtravel/views.py

@@ -51,6 +51,8 @@ class VisitedRegionViewSet(viewsets.ModelViewSet):
 
     def create(self, request, *args, **kwargs):
         request.data['user_id'] = request.user
+        if VisitedRegion.objects.filter(user_id=request.user.id, region=request.data['region']).exists():
+            return Response({"error": "Region already visited by user."}, status=400)
         serializer = self.get_serializer(data=request.data)
         serializer.is_valid(raise_exception=True)
         self.perform_create(serializer)

frontend/src/routes/worldtravel/[id]/+page.svelte

@@ -9,6 +9,11 @@
 	console.log(data);
 
 	let numRegions: number = regions.length;
+
+	visitedRegions = visitedRegions.filter(
+		(visitedRegion, index, self) =>
+			index === self.findIndex((t) => t.region === visitedRegion.region)
+	);
 	let numVisitedRegions: number = visitedRegions.length;
 </script>