From 9e063415643ff0e8a871a95c41fd2d8fa5077e85 Mon Sep 17 00:00:00 2001
From: Cosmo <cosmo@digital-home.site>
Date: Sun, 1 Mar 2026 05:22:56 +0000
Subject: [PATCH] feat: cumulative balance with carried_over in finance summary

---
 internal/model/finance.go      |  1 +
 internal/repository/finance.go | 23 +++++++++++++++++++++--
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/internal/model/finance.go b/internal/model/finance.go
index 4a6210e..3fdfc16 100644
--- a/internal/model/finance.go
+++ b/internal/model/finance.go
@@ -73,6 +73,7 @@ type UpdateFinanceTransactionRequest struct {
 }
 
 type FinanceSummary struct {
+	CarriedOver  float64              `json:"carried_over"`
 	Balance      float64              `json:"balance"`
 	TotalIncome  float64              `json:"total_income"`
 	TotalExpense float64              `json:"total_expense"`
diff --git a/internal/repository/finance.go b/internal/repository/finance.go
index 17bcc7a..ac4a885 100644
--- a/internal/repository/finance.go
+++ b/internal/repository/finance.go
@@ -237,15 +237,34 @@ func (r *FinanceRepository) DeleteTransaction(id, userID int64) error {
 func (r *FinanceRepository) GetSummary(userID int64, month, year int) (*model.FinanceSummary, error) {
 	summary := &model.FinanceSummary{}
 
+	// First day of selected month and last day of selected month
+	firstDay := time.Date(year, time.Month(month), 1, 0, 0, 0, 0, time.UTC)
+	lastDay := firstDay.AddDate(0, 1, -1)
+
+	// Carried over: balance of all transactions BEFORE the selected month
+	err := r.db.QueryRow(`SELECT COALESCE(SUM(CASE WHEN type='income' THEN amount ELSE -amount END), 0)
+		FROM finance_transactions WHERE user_id=$1 AND date < $2`,
+		userID, firstDay).Scan(&summary.CarriedOver)
+	if err != nil {
+		return nil, err
+	}
+
 	// Total income & expense for the month
-	err := r.db.QueryRow(`SELECT COALESCE(SUM(CASE WHEN type='income' THEN amount ELSE 0 END),0),
+	err = r.db.QueryRow(`SELECT COALESCE(SUM(CASE WHEN type='income' THEN amount ELSE 0 END),0),
 		COALESCE(SUM(CASE WHEN type='expense' THEN amount ELSE 0 END),0)
 		FROM finance_transactions WHERE user_id=$1 AND EXTRACT(MONTH FROM date)=$2 AND EXTRACT(YEAR FROM date)=$3`,
 		userID, month, year).Scan(&summary.TotalIncome, &summary.TotalExpense)
 	if err != nil {
 		return nil, err
 	}
-	summary.Balance = summary.TotalIncome - summary.TotalExpense
+
+	// Cumulative balance: all transactions up to end of selected month
+	err = r.db.QueryRow(`SELECT COALESCE(SUM(CASE WHEN type='income' THEN amount ELSE -amount END), 0)
+		FROM finance_transactions WHERE user_id=$1 AND date <= $2`,
+		userID, lastDay).Scan(&summary.Balance)
+	if err != nil {
+		return nil, err
+	}
 
 	// By category
 	rows, err := r.db.Query(`SELECT c.id, c.name, c.emoji, t.type, SUM(t.amount) as amount