(feat) Add monthly view for cashflow income statement page

internal/server/income_statement.go

@@ -36,7 +36,8 @@ type RunningBalance struct {
 func GetIncomeStatement(db *gorm.DB) gin.H {
 	postings := query.Init(db).All()
 	statements := computeStatement(db, postings)
-	return gin.H{"yearly": statements}
+	monthlyStatements := computeMonthlyStatement(db, postings)
+	return gin.H{"yearly": statements, "monthly": monthlyStatements}
 }
 
 func computeStatement(db *gorm.DB, postings []posting.Posting) map[string]IncomeStatement {
@@ -132,6 +133,123 @@ func computeStatement(db *gorm.DB, postings []posting.Posting) map[string]Income
 	return statements
 }
 
+func computeMonthlyStatement(db *gorm.DB, postings []posting.Posting) map[string]map[string]IncomeStatement {
+	monthlyStatements := make(map[string]map[string]IncomeStatement)
+
+	grouped := utils.GroupByFY(postings)
+	fys := lo.Keys(grouped)
+	sort.Strings(fys)
+
+	for _, fy := range fys {
+		fyPostings := grouped[fy]
+		monthlyStatements[fy] = make(map[string]IncomeStatement)
+
+		// Group postings by month within the financial year
+		monthlyGrouped := utils.GroupByMonth(fyPostings)
+
+		// Get all months in the financial year
+		start, end := utils.ParseFY(fy)
+		current := start
+
+		runnings := make(map[string]RunningBalance)
+		startingBalance := decimal.Zero
+
+		for current.Before(end) || current.Equal(end) {
+			monthKey := current.Format("2006-01")
+			incomeStatement := IncomeStatement{}
+			incomeStatement.Date = current
+			incomeStatement.StartingBalance = startingBalance
+			incomeStatement.Income = make(map[string]decimal.Decimal)
+			incomeStatement.Interest = make(map[string]decimal.Decimal)
+			incomeStatement.Equity = make(map[string]decimal.Decimal)
+			incomeStatement.Pnl = make(map[string]decimal.Decimal)
+			incomeStatement.Liabilities = make(map[string]decimal.Decimal)
+			incomeStatement.Tax = make(map[string]decimal.Decimal)
+			incomeStatement.Expenses = make(map[string]decimal.Decimal)
+
+			monthPostings := monthlyGrouped[monthKey]
+
+			for _, p := range monthPostings {
+				category := utils.FirstName(p.Account)
+
+				switch category {
+				case "Income":
+					if service.IsCapitalGains(p) {
+						sourceAccount := service.CapitalGainsSourceAccount(p.Account)
+						r := runnings[sourceAccount]
+						if r.quantity == nil {
+							r.quantity = make(map[string]decimal.Decimal)
+						}
+						r.amount = r.amount.Add(p.Amount)
+						runnings[sourceAccount] = r
+					} else if strings.HasPrefix(p.Account, "Income:Interest") {
+						incomeStatement.Interest[p.Account] = incomeStatement.Interest[p.Account].Add(p.Amount)
+					} else {
+						incomeStatement.Income[p.Account] = incomeStatement.Income[p.Account].Add(p.Amount)
+					}
+				case "Equity":
+					incomeStatement.Equity[p.Account] = incomeStatement.Equity[p.Account].Add(p.Amount)
+				case "Expenses":
+					if strings.HasPrefix(p.Account, "Expenses:Tax") {
+						incomeStatement.Tax[p.Account] = incomeStatement.Tax[p.Account].Add(p.Amount)
+					} else {
+						incomeStatement.Expenses[p.Account] = incomeStatement.Expenses[p.Account].Add(p.Amount)
+					}
+				case "Liabilities":
+					incomeStatement.Liabilities[p.Account] = incomeStatement.Liabilities[p.Account].Add(p.Amount)
+				case "Assets":
+					r := runnings[p.Account]
+					if r.quantity == nil {
+						r.quantity = make(map[string]decimal.Decimal)
+					}
+					r.amount = r.amount.Add(p.Amount)
+					r.quantity[p.Commodity] = r.quantity[p.Commodity].Add(p.Quantity)
+					runnings[p.Account] = r
+				default:
+					// ignore
+				}
+			}
+
+			// Calculate PnL for this month
+			monthEndDate := current.AddDate(0, 1, -1) // Last day of current month
+			if monthEndDate.After(end) {
+				monthEndDate = end
+			}
+
+			for account, r := range runnings {
+				diff := r.amount.Neg()
+				for commodity, quantity := range r.quantity {
+					diff = diff.Add(service.GetPrice(db, commodity, quantity, monthEndDate))
+				}
+				if !diff.IsZero() {
+					incomeStatement.Pnl[account] = diff
+				}
+
+				r.amount = r.amount.Add(diff)
+				runnings[account] = r
+			}
+
+			startingBalance = startingBalance.
+				Add(sumBalance(incomeStatement.Income).Neg()).
+				Add(sumBalance(incomeStatement.Interest).Neg()).
+				Add(sumBalance(incomeStatement.Equity).Neg()).
+				Add(sumBalance(incomeStatement.Tax).Neg()).
+				Add(sumBalance(incomeStatement.Expenses).Neg()).
+				Add(sumBalance(incomeStatement.Pnl)).
+				Add(sumBalance(incomeStatement.Liabilities).Neg())
+
+			incomeStatement.EndingBalance = startingBalance
+
+			monthlyStatements[fy][monthKey] = incomeStatement
+
+			// Move to next month
+			current = current.AddDate(0, 1, 0)
+		}
+	}
+
+	return monthlyStatements
+}
+
 func sumBalance(breakdown map[string]decimal.Decimal) decimal.Decimal {
 	total := decimal.Zero
 	for k, v := range breakdown {