feat(networth): add a chart with the currency difference between each month

app/apps/net_worth/utils/calculate_net_worth.py

@@ -182,3 +182,29 @@ def calculate_historical_account_balance(queryset):
         historical_account_balance[date_filter(end_date, "b Y")] = month_data
 
     return historical_account_balance
+
+
+def calculate_monthly_net_worth_difference(historical_net_worth):
+    diff_dict = OrderedDict()
+    if not historical_net_worth:
+        return diff_dict
+
+    # Get all currencies
+    currencies = set()
+    for data in historical_net_worth.values():
+        currencies.update(data.keys())
+
+    # Initialize prev_values for all currencies
+    prev_values = {currency: Decimal("0.00") for currency in currencies}
+
+    for month, values in historical_net_worth.items():
+        diff_values = {}
+        for currency in sorted(list(currencies)):
+            current_val = values.get(currency, Decimal("0.00"))
+            prev_val = prev_values.get(currency, Decimal("0.00"))
+            diff_values[currency] = current_val - prev_val
+
+        diff_dict[month] = diff_values
+        prev_values = values.copy()
+
+    return diff_dict

app/apps/net_worth/views.py

@@ -8,6 +8,7 @@ from django.views.decorators.http import require_http_methods
 from apps.net_worth.utils.calculate_net_worth import (
     calculate_historical_currency_net_worth,
     calculate_historical_account_balance,
+    calculate_monthly_net_worth_difference,
 )
 from apps.transactions.models import Transaction
 from apps.transactions.utils.calculations import (
@@ -96,6 +97,38 @@ def net_worth(request):
 
     chart_data_currency_json = json.dumps(chart_data_currency, cls=DjangoJSONEncoder)
 
+    monthly_difference_data = calculate_monthly_net_worth_difference(
+        historical_net_worth=historical_currency_net_worth
+    )
+
+    diff_labels = (
+        list(monthly_difference_data.keys()) if monthly_difference_data else []
+    )
+    diff_currencies = (
+        list(monthly_difference_data[diff_labels[0]].keys())
+        if monthly_difference_data and diff_labels
+        else []
+    )
+
+    diff_datasets = []
+    for i, currency in enumerate(diff_currencies):
+        data = [
+            float(month_data.get(currency, 0))
+            for month_data in monthly_difference_data.values()
+        ]
+        diff_datasets.append(
+            {
+                "label": currency,
+                "data": data,
+                "borderWidth": 3,
+            }
+        )
+
+    chart_data_monthly_difference = {"labels": diff_labels, "datasets": diff_datasets}
+    chart_data_monthly_difference_json = json.dumps(
+        chart_data_monthly_difference, cls=DjangoJSONEncoder
+    )
+
     historical_account_balance = calculate_historical_account_balance(
         queryset=transactions_account_queryset
     )
@@ -140,6 +173,7 @@ def net_worth(request):
             "chart_data_accounts_json": chart_data_accounts_json,
             "accounts": accounts,
             "type": view_type,
+            "chart_data_monthly_difference_json": chart_data_monthly_difference_json,
         },
     )