feat: prevent two decisions with the same college

tjdests/apps/profile/forms.py

@@ -4,6 +4,7 @@ from crispy_forms.helper import FormHelper
 from crispy_forms.layout import Submit
 
 from django import forms
+from django.core.exceptions import ValidationError
 
 from tjdests.apps.authentication.models import User
 from tjdests.apps.destinations.models import Decision, TestScore
@@ -36,6 +37,44 @@ class DecisionForm(forms.ModelForm):
         model = Decision
         fields = ["college", "decision_type", "admission_status"]
 
+    def __init__(self, *args, **kwargs):
+        self.request = kwargs.pop("request", None)
+        self.is_edit = kwargs.pop("edit", False)
+        super().__init__(*args, **kwargs)
+
+    def clean(self) -> Dict[str, Any]:
+        cleaned_data = super().clean()
+
+        # Ensure that the college is not a duplicate for this user
+        # Yes, this is weird. Basically: if we are not editing
+        # (i.e. creating a new one), we make sure that
+        # the user does not have a Decision object with that college already.
+        # If we are editing, then we ensure that the college
+        # has not changed. If it has changed, then we
+        # make sure that the user does not have a Decision object with that college already.
+        if (
+            not self.is_edit
+            and Decision.objects.filter(
+                user=self.request.user, college=cleaned_data.get("college")
+            ).count()
+            > 0
+        ) or (
+            self.is_edit
+            and Decision.objects.filter(
+                user=self.request.user,
+                id=self.instance.id,
+                college=cleaned_data.get("college"),
+            ).count()
+            != 1
+            and Decision.objects.filter(
+                user=self.request.user, college=cleaned_data.get("college")
+            ).count()
+            > 0
+        ):
+            raise ValidationError("You cannot add a second entry for this college")
+
+        return cleaned_data
+
 
 class TestScoreForm(forms.ModelForm):
     class Meta:

tjdests/apps/profile/views.py

@@ -1,3 +1,5 @@
+from typing import Any, Dict
+
 from django.contrib import messages
 from django.contrib.auth.decorators import login_required
 from django.contrib.auth.mixins import LoginRequiredMixin, UserPassesTestMixin
@@ -10,7 +12,7 @@ from django.views.generic import CreateView, DeleteView, UpdateView
 from tjdests.apps.authentication.decorators import require_accept_tos
 from tjdests.apps.destinations.models import Decision, TestScore
 
-from .forms import ProfilePublishForm, TestScoreForm
+from .forms import DecisionForm, ProfilePublishForm, TestScoreForm
 
 
 @login_required
@@ -103,7 +105,7 @@ class DecisionCreateView(
     LoginRequiredMixin, SuccessMessageMixin, UserPassesTestMixin, CreateView
 ):
     model = Decision
-    fields = ["college", "decision_type", "admission_status"]
+    form_class = DecisionForm
     template_name = "profile/decision_form.html"
     success_message = "Decision created successfully."
 
@@ -111,6 +113,11 @@ class DecisionCreateView(
         form.instance.user = self.request.user
         return super().form_valid(form)
 
+    def get_form_kwargs(self) -> Dict[str, Any]:
+        form_kwargs = super().get_form_kwargs()
+        form_kwargs["request"] = self.request
+        return form_kwargs
+
     def test_func(self):
         return self.request.user.is_senior and self.request.user.accepted_terms
 
@@ -122,7 +129,7 @@ class DecisionUpdateView(
     LoginRequiredMixin, SuccessMessageMixin, UserPassesTestMixin, UpdateView
 ):
     model = Decision
-    fields = ["college", "decision_type", "admission_status"]
+    form_class = DecisionForm
     template_name = "profile/decision_form.html"
     success_message = "Decision created successfully."
 
@@ -130,6 +137,12 @@ class DecisionUpdateView(
         form.instance.user = self.request.user
         return super().form_valid(form)
 
+    def get_form_kwargs(self) -> Dict[str, Any]:
+        form_kwargs = super().get_form_kwargs()
+        form_kwargs["request"] = self.request
+        form_kwargs["edit"] = True
+        return form_kwargs
+
     def get_queryset(self):
         owner = self.request.user
         return self.model.objects.filter(user=owner)