Compare previous period by category

expenses_manager/expenses/templates/expenses/dashboard.html

@@ -144,6 +144,39 @@
             </tbody>
         </table>
         
+        {% if compare_enabled %}
+            <h3>Comparativa por categoría</h3>
+
+            <table>
+                <thead>
+                    <tr>
+                        <th>Categoría</th>
+                        <th>Actual</th>
+                        <th>Anterior</th>
+                        <th>Diferencia</th>
+                    </tr>
+                </thead>
+                <tbody>
+                    {% for row in category_comparison %}
+                    <tr>
+                        <td>{{ row.category }}</td>
+                        <td>{{ row.current }}</td>
+                        <td>{{ row.previous }}</td>
+                        <td>
+                            {% if row.difference > 0 %}
+                                ▲ {{ row.difference }}
+                            {% elif row.difference < 0 %}
+                                ▼ {{ row.difference }}
+                            {% else %}
+                                =
+                            {% endif %}
+                        </td>
+                    </tr>
+                    {% endfor %}
+                </tbody>
+            </table>
+        {% endif %}
+
         <hr>
 
         <!-- ========================= -->

expenses_manager/expenses/views.py

@@ -207,6 +207,7 @@ def dashboard(request):
     previous_total = None
     difference = None
     percentage = None
+    category_comparison = None
     
     if compare_enabled:
         previous_expenses = Expense.objects.filter(owner=request.user)
@@ -240,6 +241,41 @@ def dashboard(request):
         if previous_total:
             percentage = (difference / previous_total) * 100
 
+    # ------------------
+    # Previous expenses by category
+    # ------------------
+    
+        previous_by_category = (
+            previous_expenses
+            .values('category__name')
+            .annotate(total=Sum('amount'))
+        )
+        
+        current_map = {
+            row['category__name']: row['total']
+            for row in by_category
+        }
+        
+        previous_map = {
+            row['category__name']: row['total']
+            for row in previous_by_category
+        }
+        
+        all_categories = set(current_map.keys()) | set(previous_map.keys())
+        
+        category_comparison = []
+        for category in all_categories:
+            current_total = current_map.get(category, 0)
+            previous_total_cat = previous_map.get(category, 0)
+            
+            difference = current_total - previous_total_cat
+            
+            category_comparison.append({
+                'category': category,
+                'current': current_total,
+                'previous': previous_total_cat,
+                'difference': difference,
+            })
     
     # Send the data to the dashboard
     return render(request, 'expenses/dashboard.html', {
@@ -258,4 +294,5 @@ def dashboard(request):
         'kpi_previous_total': previous_total,
         'kpi_difference': difference,
         'kpi_percentage': percentage,
+        'category_comparison': category_comparison,
     })