From 444f5e6a2da48372b75af7dd2943efd4e66d23da Mon Sep 17 00:00:00 2001
From: William Wei Ming <280573057+bittensorrider@users.noreply.github.com>
Date: Thu, 21 May 2026 02:28:26 +0800
Subject: [PATCH] optimize net_category_totals() by using memoized cache
 (#1881)

* optimize net_category_totals() by using memoized cache

* fix issue - net_category_totals cache is never populated - suggested by coderabbitAI
---
 app/models/income_statement.rb | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/app/models/income_statement.rb b/app/models/income_statement.rb
index f885e3f81..6082f8e74 100644
--- a/app/models/income_statement.rb
+++ b/app/models/income_statement.rb
@@ -30,14 +30,23 @@ class IncomeStatement
   end
 
   def expense_totals(period: Period.current_month)
-    build_period_total(classification: "expense", period: period)
+    # Memoized per instance so callers that also invoke `net_category_totals`
+    @expense_totals_by_period ||= {}
+    @expense_totals_by_period[period_cache_key(period)] ||=
+      build_period_total(classification: "expense", period: period)
   end
 
   def income_totals(period: Period.current_month)
-    build_period_total(classification: "income", period: period)
+    @income_totals_by_period ||= {}
+    @income_totals_by_period[period_cache_key(period)] ||=
+      build_period_total(classification: "income", period: period)
   end
 
   def net_category_totals(period: Period.current_month)
+    @net_category_totals_by_period ||= {}
+    cached = @net_category_totals_by_period[period_cache_key(period)]
+    return cached if cached
+
     expense = expense_totals(period: period)
     income = income_totals(period: period)
 
@@ -87,7 +96,7 @@ class IncomeStatement
       CategoryTotal.new(category: r[:category], total: r[:total], currency: family.currency, weight: weight)
     end
 
-    NetCategoryTotals.new(
+    @net_category_totals_by_period[period_cache_key(period)] = NetCategoryTotals.new(
       net_expense_categories: net_expense_categories,
       net_income_categories: net_income_categories,
       total_net_expense: total_net_expense,
@@ -126,6 +135,10 @@ class IncomeStatement
       @categories ||= family.categories.all.to_a
     end
 
+    def period_cache_key(period)
+      [ period.start_date, period.end_date ]
+    end
+
     def build_period_total(classification:, period:)
       # Exclude pending transactions from budget calculations
       totals = totals_query(transactions_scope: family.transactions.visible.excluding_pending.in_period(period), date_range: period.date_range).select { |t| t.classification == classification }