Now, the user can't select as category parent itself or childrens

expenses_manager/expenses/forms.py

@@ -92,9 +92,42 @@ class CategoryForm(forms.ModelForm):
         super().__init__(*args, **kwargs)
         
         if user:
-            self.fields["parent"].queryset = Category.objects.filter(
+            queryset = Category.objects.filter(owner=user)
-                owner=user,
+            
+            if self.instance.pk:
+                queryset = queryset.exclude(
+                    pk__in=self._self_and_descendant_ids(self.instance)
+                )
+            
+            self.fields["parent"].queryset = queryset
+    
+    @staticmethod
+    def _self_and_descendant_ids(category):
+        ids = [category.pk]
+        pending = [category.pk]
+        
+        while pending:
+            children = list(
+                Category.objects.filter(parent_id__in=pending)
+                .exclude(pk__in=ids)
+                .values_list("pk", flat=True)
             )
+            ids.extend(children)
+            pending = children
+        
+        return ids
+    
+    def clean_parent(self):
+        parent = self.cleaned_data.get("parent")
+
+        if parent and self.instance.pk:
+            if parent.pk in self._self_and_descendant_ids(self.instance):
+                raise forms.ValidationError(
+                    "Una categoría no puede ser su propio padre ni depender "
+                    "de una de sus subcategorías."
+                )
+
+        return parent
 
 
 class GoalForm(forms.ModelForm):

expenses_manager/expenses/templates/categories/confirm_delete.html

@@ -0,0 +1,38 @@
+{% extends "expenses/base.html" %}
+
+{% block title %}
+    Categorías
+{% endblock %}
+
+{% block content %}
+    <h2>Eliminar categoría</h2>
+
+    <p>¿Seguro que quieres eliminar la categoría <strong>{{ category.name }}</strong>?</p>
+
+    {% if expense_count %}
+        <p class="form-errors">
+            Esta categoría tiene {{ expense_count }} gasto{{ expense_count|pluralize }} asociado{{ expense_count|pluralize }}
+            y no se puede eliminar. Reasigna esos gastos a otra categoría primero.
+        </p>
+    {% else %}
+        {% if children %}
+            <p class="form-errors">
+                Atención: también se eliminarán sus subcategorías:
+                {% for child in children %}<strong>{{child.name}}</strong>{% if not forloop.last %}, {% endif %}{% endfor %}.
+            </p>
+        {% endif %}
+
+        {% if goal_count %}
+            <p class="form-errors">
+                Atención: se eliminarán también {{ goal_count }} objetivo{{ goal_count|pluralize }} asociado{{ goal_count|pluralize }} a esta categoría.
+            </p>
+        {% endif %}
+    {% endif %}
+
+    <form method="post">
+        {% csrf_token %}
+        {{ form.as_p }}
+        <button class="btn danger">Eliminar</button>
+        <a class="btn" href="{% url 'category_list' %}">Cancelar</a>
+    </form>
+{% endblock %}

expenses_manager/expenses/templates/categories/form.html

@@ -0,0 +1,16 @@
+{% extends "expenses/base.html" %}
+
+{% block title %}
+    Categorías
+{% endblock %}
+
+{% block content %}
+    <h2>Editar categoría</h2>
+
+    <form method="post">
+        {% csrf_token %}
+        {{ form.as_p }}
+        <button type="submit">Guardar</button>
+        <a class="btn" href="{% url 'category_list' %}">Cancelar</a>
+    </form>
+{% endblock %}

expenses_manager/expenses/templates/categories/list.html

@@ -30,6 +30,10 @@
                 <tr>
                     <td>{{ category.name }}</td>
                     <td>{% if category.parent %}{{ category.parent.name }}{% endif %}</td>
+                    <td class="table-actions">
+                        <a href="{% url 'category_edit' category.id %}">Editar</a>
+                        <a href="{% url 'category_delete' category.id %}" class="danger">Eliminar</a>
+                    </td>
                 </tr>
             {% endfor %}
         </tbody>

expenses_manager/expenses/urls.py

@@ -24,6 +24,8 @@ urlpatterns = [
     path('fuel/create/', views.fuel_create, name='fuel_create'),
     path('fuel/<int:pk>/edit/', views.fuel_edit, name='fuel_edit'),
     path('categories/', views.category_list, name='category_list'),
+    path('categories/<int:pk>/edit/', views.category_edit, name='category_edit'),
+    path('categories/<int:pk>/delete/', views.category_delete, name='category_delete'),
     path('settings/', views.settings_index, name='settings_index'),
     path('goals/', views.goal_list, name='goal_list'),
     path('goals/new/', views.goal_create, name='goal_create'),

expenses_manager/expenses/views.py

@@ -13,8 +13,8 @@ from .forms import (
     GoalForm,
 )
 
-from django.db.models import Sum
 from django.core.paginator import Paginator
+from django.db.models import Sum, ProtectedError
 from django.db.models.functions import ExtractMonth, ExtractYear, ExtractDay
 
 from django.contrib.auth.decorators import login_required
@@ -859,6 +859,60 @@ def category_list(request):
     )
 
 
+@login_required
+def category_edit(request, pk):
+    category = get_object_or_404(Category, pk=pk, owner=request.user)
+    
+    if request.method == "POST":
+        form = CategoryForm(request.POST, instance=category, user=request.user)
+        if form.is_valid():
+            form.save()
+            messages.success(request, "Categoría actualizada")
+            return redirect("category_list")
+    else:
+        form = CategoryForm(instance=category, user=request.user)
+    
+    return render(
+        request,
+        "categories/form.html",
+        {
+            "active_menu": "settings",
+            "form":form,
+            "category": category,
+        }
+    )
+
+
+@login_required
+def category_delete(request, pk):
+    category = get_object_or_404(Category, pk=pk, owner=request.user)
+    
+    if request.method == "POST":
+        try:
+            category.delete()
+        except ProtectedError:
+            messages.error(
+                request,
+                f"No se puede eliminar «{category.name}»; tiene gastos asociados. "
+                "Reasigna esos gastos a otra categoría antes de borrarla."
+            )
+        else: 
+            messages.success(request, "Categoría eliminada.")
+        return redirect("category_list")
+    
+    return render(
+        request,
+        "categories/confirm_delete.html",
+        {
+            "active_menu": "settings",
+            "category": category,
+            "children": category.children.all(),
+            "expense_count": category.expenses.count(),
+            "goal_count": category.goal_set.count(),
+        },
+    )
+
+
 @login_required
 def goal_list(request):
     goals = Goal.objects.filter(owner=request.user)