From fb6e0f379e65aad58a301129cba0034cba80c40f Mon Sep 17 00:00:00 2001
From: JKuijperM <jkmontero17@gmail.com>
Date: Wed, 21 Jan 2026 20:14:29 +0100
Subject: [PATCH] Prepared view to calculate the previous data

---
 .../templates/expenses/dashboard.html         | 11 +++-
 expenses_manager/expenses/views.py            | 59 ++++++++++++++++++-
 2 files changed, 66 insertions(+), 4 deletions(-)

diff --git a/expenses_manager/expenses/templates/expenses/dashboard.html b/expenses_manager/expenses/templates/expenses/dashboard.html
index 1f6e38e..d8ef8ee 100644
--- a/expenses_manager/expenses/templates/expenses/dashboard.html
+++ b/expenses_manager/expenses/templates/expenses/dashboard.html
@@ -81,6 +81,12 @@
         <!-- Chart -->
         <!-- ========================= -->
 
+        <label>
+            <input type="checkbox" name="compare" value="1"
+                {% if compare %}checked{% endif %}>
+            Comparar con periodo anterior
+        </label>
+        
         <canvas id="expensesChart"></canvas>
 
         <script>
@@ -99,7 +105,10 @@
                     }]
                 }
             });
-        </script>        
+        </script>   
+        
+        <hr>
+
     
 </body>
 </html>
\ No newline at end of file
diff --git a/expenses_manager/expenses/views.py b/expenses_manager/expenses/views.py
index dea71fa..59b3994 100644
--- a/expenses_manager/expenses/views.py
+++ b/expenses_manager/expenses/views.py
@@ -1,7 +1,7 @@
 from datetime import date
-from re import M
 from .models import Expense
 from .forms import ExpenseForm
+# from dateutli.relativedelta import relativedelta
 
 from django.db.models import Sum
 from django.contrib.auth import login
@@ -115,7 +115,9 @@ def dashboard(request):
     current_year = date.today().year
     
     selected_year = year or current_year
-    selected_month = month
+    selected_month = month    
+        
+    compare = request.GET.get("compare") == "1"
     
     # ------------------
     # Queryset base
@@ -188,10 +190,61 @@ def dashboard(request):
         .order_by('year')
     )
     
-    # Prepare data fot ploting in chart
+    # ------------------
+    # Chart
+    # -----------------
     chart_labels = months
     chart_totals = [row['total'] for row in by_month]
     
+    # ------------------
+    # Compare period
+    # -----------------
+    
+    previous_expenses = expenses
+    
+    if month and year:
+        if month == 1:
+            prev_year = year - 1
+            prev_month = 12
+        else:
+            prev_year = year
+            prev_month = month - 1
+        previous_expenses = previous_expenses.filter(
+            date__year=prev_year,
+            date__month=prev_month
+        )
+    elif year and month is None:
+        prev_year = year - 1
+        previous_expenses = previous_expenses.filter(
+            date__year=prev_year
+        )
+    else:
+        today = date.today()
+        year = today.year
+        month = today.month
+        
+        if month == 1:
+            prev_year = year - 1
+            prev_month = 12
+        else:
+            prev_year = year
+            prev_month = month - 1
+        
+        previous_expenses = previous_expenses.filter(
+            date__year=prev_year,
+            date__month=prev_month
+        )
+
+    previous_total = (
+        previous_expenses.aggregate(total=Sum('amount'))['total'] or 0
+    )
+    
+    difference = total_amount - previous_total
+    precentage = (
+        (difference / previous_total) * 100 if previous_total else None
+    )
+
+    
     # Send the data to the dashboard
     return render(request, 'expenses/dashboard.html', {
         'by_category': by_category,