Merge branch 'fix/calculation-accuracy' into main

Combines the decimal migration (int cents → decimal.Decimal via
shopspring/decimal) with main's handler refactor (split space.go into
domain handlers, WithTx/Paginate helpers, recurring deposit removal).

- Repository layer: WithTx pattern + decimal column names/types
- Handler layer: decimal arithmetic (.Sub/.Add) instead of int operators
- Models: deprecated amount_cents fields kept for SELECT * compatibility
- INSERT statements: old columns set to literal 0 for NOT NULL constraints

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/service/budget.go

@@ -7,12 +7,13 @@ import (
 	"git.juancwu.dev/juancwu/budgit/internal/model"
 	"git.juancwu.dev/juancwu/budgit/internal/repository"
 	"github.com/google/uuid"
+	"github.com/shopspring/decimal"
 )
 
 type CreateBudgetDTO struct {
 	SpaceID   string
 	TagIDs    []string
-	Amount    int
+	Amount    decimal.Decimal
 	Period    model.BudgetPeriod
 	StartDate time.Time
 	EndDate   *time.Time
@@ -22,7 +23,7 @@ type CreateBudgetDTO struct {
 type UpdateBudgetDTO struct {
 	ID        string
 	TagIDs    []string
-	Amount    int
+	Amount    decimal.Decimal
 	Period    model.BudgetPeriod
 	StartDate time.Time
 	EndDate   *time.Time
@@ -37,7 +38,7 @@ func NewBudgetService(budgetRepo repository.BudgetRepository) *BudgetService {
 }
 
 func (s *BudgetService) CreateBudget(dto CreateBudgetDTO) (*model.Budget, error) {
-	if dto.Amount <= 0 {
+	if dto.Amount.LessThanOrEqual(decimal.Zero) {
 		return nil, fmt.Errorf("budget amount must be positive")
 	}
 
@@ -47,16 +48,16 @@ func (s *BudgetService) CreateBudget(dto CreateBudgetDTO) (*model.Budget, error)
 
 	now := time.Now()
 	budget := &model.Budget{
-		ID:          uuid.NewString(),
-		SpaceID:     dto.SpaceID,
-		AmountCents: dto.Amount,
-		Period:      dto.Period,
-		StartDate:   dto.StartDate,
-		EndDate:     dto.EndDate,
-		IsActive:    true,
-		CreatedBy:   dto.CreatedBy,
-		CreatedAt:   now,
-		UpdatedAt:   now,
+		ID:        uuid.NewString(),
+		SpaceID:   dto.SpaceID,
+		Amount:    dto.Amount,
+		Period:    dto.Period,
+		StartDate: dto.StartDate,
+		EndDate:   dto.EndDate,
+		IsActive:  true,
+		CreatedBy: dto.CreatedBy,
+		CreatedAt: now,
+		UpdatedAt: now,
 	}
 
 	if err := s.budgetRepo.Create(budget, dto.TagIDs); err != nil {
@@ -99,12 +100,12 @@ func (s *BudgetService) GetBudgetsWithSpent(spaceID string) ([]*model.BudgetWith
 		start, end := GetCurrentPeriodBounds(b.Period, time.Now())
 		spent, err := s.budgetRepo.GetSpentForBudget(spaceID, tagIDs, start, end)
 		if err != nil {
-			spent = 0
+			spent = decimal.Zero
 		}
 
 		var percentage float64
-		if b.AmountCents > 0 {
-			percentage = float64(spent) / float64(b.AmountCents) * 100
+		if b.Amount.GreaterThan(decimal.Zero) {
+			percentage, _ = spent.Div(b.Amount).Mul(decimal.NewFromInt(100)).Float64()
 		}
 
 		var status model.BudgetStatus
@@ -120,7 +121,7 @@ func (s *BudgetService) GetBudgetsWithSpent(spaceID string) ([]*model.BudgetWith
 		bws := &model.BudgetWithSpent{
 			Budget:     *b,
 			Tags:       tags,
-			SpentCents: spent,
+			Spent:      spent,
 			Percentage: percentage,
 			Status:     status,
 		}
@@ -131,7 +132,7 @@ func (s *BudgetService) GetBudgetsWithSpent(spaceID string) ([]*model.BudgetWith
 }
 
 func (s *BudgetService) UpdateBudget(dto UpdateBudgetDTO) (*model.Budget, error) {
-	if dto.Amount <= 0 {
+	if dto.Amount.LessThanOrEqual(decimal.Zero) {
 		return nil, fmt.Errorf("budget amount must be positive")
 	}
 
@@ -144,7 +145,7 @@ func (s *BudgetService) UpdateBudget(dto UpdateBudgetDTO) (*model.Budget, error)
 		return nil, err
 	}
 
-	existing.AmountCents = dto.Amount
+	existing.Amount = dto.Amount
 	existing.Period = dto.Period
 	existing.StartDate = dto.StartDate
 	existing.EndDate = dto.EndDate

internal/service/expense.go

@@ -7,13 +7,14 @@ import (
 	"git.juancwu.dev/juancwu/budgit/internal/model"
 	"git.juancwu.dev/juancwu/budgit/internal/repository"
 	"github.com/google/uuid"
+	"github.com/shopspring/decimal"
 )
 
 type CreateExpenseDTO struct {
 	SpaceID         string
 	UserID          string
 	Description     string
-	Amount          int
+	Amount          decimal.Decimal
 	Type            model.ExpenseType
 	Date            time.Time
 	TagIDs          []string
@@ -25,7 +26,7 @@ type UpdateExpenseDTO struct {
 	ID              string
 	SpaceID         string
 	Description     string
-	Amount          int
+	Amount          decimal.Decimal
 	Type            model.ExpenseType
 	Date            time.Time
 	TagIDs          []string
@@ -48,7 +49,7 @@ func (s *ExpenseService) CreateExpense(dto CreateExpenseDTO) (*model.Expense, er
 	if dto.Description == "" {
 		return nil, fmt.Errorf("expense description cannot be empty")
 	}
-	if dto.Amount <= 0 {
+	if dto.Amount.LessThanOrEqual(decimal.Zero) {
 		return nil, fmt.Errorf("amount must be positive")
 	}
 
@@ -58,7 +59,7 @@ func (s *ExpenseService) CreateExpense(dto CreateExpenseDTO) (*model.Expense, er
 		SpaceID:         dto.SpaceID,
 		CreatedBy:       dto.UserID,
 		Description:     dto.Description,
-		AmountCents:     dto.Amount,
+		Amount:          dto.Amount,
 		Type:            dto.Type,
 		Date:            dto.Date,
 		PaymentMethodID: dto.PaymentMethodID,
@@ -78,18 +79,18 @@ func (s *ExpenseService) GetExpensesForSpace(spaceID string) ([]*model.Expense,
 	return s.expenseRepo.GetBySpaceID(spaceID)
 }
 
-func (s *ExpenseService) GetBalanceForSpace(spaceID string) (int, error) {
+func (s *ExpenseService) GetBalanceForSpace(spaceID string) (decimal.Decimal, error) {
 	expenses, err := s.expenseRepo.GetBySpaceID(spaceID)
 	if err != nil {
-		return 0, err
+		return decimal.Zero, err
 	}
 
-	var balance int
+	balance := decimal.Zero
 	for _, expense := range expenses {
 		if expense.Type == model.ExpenseTypeExpense {
-			balance -= expense.AmountCents
+			balance = balance.Sub(expense.Amount)
 		} else if expense.Type == model.ExpenseTypeTopup {
-			balance += expense.AmountCents
+			balance = balance.Add(expense.Amount)
 		}
 	}
 
@@ -212,7 +213,7 @@ func (s *ExpenseService) UpdateExpense(dto UpdateExpenseDTO) (*model.Expense, er
 	if dto.Description == "" {
 		return nil, fmt.Errorf("expense description cannot be empty")
 	}
-	if dto.Amount <= 0 {
+	if dto.Amount.LessThanOrEqual(decimal.Zero) {
 		return nil, fmt.Errorf("amount must be positive")
 	}
 
@@ -222,7 +223,7 @@ func (s *ExpenseService) UpdateExpense(dto UpdateExpenseDTO) (*model.Expense, er
 	}
 
 	existing.Description = dto.Description
-	existing.AmountCents = dto.Amount
+	existing.Amount = dto.Amount
 	existing.Type = dto.Type
 	existing.Date = dto.Date
 	existing.PaymentMethodID = dto.PaymentMethodID

internal/service/expense_test.go

@@ -7,6 +7,7 @@ import (
 	"git.juancwu.dev/juancwu/budgit/internal/model"
 	"git.juancwu.dev/juancwu/budgit/internal/repository"
 	"git.juancwu.dev/juancwu/budgit/internal/testutil"
+	"github.com/shopspring/decimal"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
@@ -24,7 +25,7 @@ func TestExpenseService_CreateExpense(t *testing.T) {
 			SpaceID:     space.ID,
 			UserID:      user.ID,
 			Description: "Lunch",
-			Amount:      1500,
+			Amount:      decimal.RequireFromString("15.00"),
 			Type:        model.ExpenseTypeExpense,
 			Date:        time.Now(),
 			TagIDs:      []string{tag.ID},
@@ -32,7 +33,7 @@ func TestExpenseService_CreateExpense(t *testing.T) {
 		require.NoError(t, err)
 		assert.NotEmpty(t, expense.ID)
 		assert.Equal(t, "Lunch", expense.Description)
-		assert.Equal(t, 1500, expense.AmountCents)
+		assert.True(t, decimal.RequireFromString("15.00").Equal(expense.Amount))
 		assert.Equal(t, model.ExpenseTypeExpense, expense.Type)
 	})
 }
@@ -46,7 +47,7 @@ func TestExpenseService_CreateExpense_EmptyDescription(t *testing.T) {
 			SpaceID:     "some-space",
 			UserID:      "some-user",
 			Description: "",
-			Amount:      1000,
+			Amount:      decimal.RequireFromString("10.00"),
 			Type:        model.ExpenseTypeExpense,
 			Date:        time.Now(),
 		})
@@ -64,7 +65,7 @@ func TestExpenseService_CreateExpense_ZeroAmount(t *testing.T) {
 			SpaceID:     "some-space",
 			UserID:      "some-user",
 			Description: "Something",
-			Amount:      0,
+			Amount:      decimal.Zero,
 			Type:        model.ExpenseTypeExpense,
 			Date:        time.Now(),
 		})
@@ -87,7 +88,7 @@ func TestExpenseService_GetExpensesWithTagsForSpacePaginated(t *testing.T) {
 			SpaceID:     space.ID,
 			UserID:      user.ID,
 			Description: "Bus fare",
-			Amount:      250,
+			Amount:      decimal.RequireFromString("2.50"),
 			Type:        model.ExpenseTypeExpense,
 			Date:        time.Now(),
 			TagIDs:      []string{tag.ID},
@@ -99,7 +100,7 @@ func TestExpenseService_GetExpensesWithTagsForSpacePaginated(t *testing.T) {
 			SpaceID:     space.ID,
 			UserID:      user.ID,
 			Description: "Coffee",
-			Amount:      500,
+			Amount:      decimal.RequireFromString("5.00"),
 			Type:        model.ExpenseTypeExpense,
 			Date:        time.Now(),
 		})
@@ -132,12 +133,12 @@ func TestExpenseService_GetBalanceForSpace(t *testing.T) {
 		user := testutil.CreateTestUser(t, dbi.DB, "exp-svc-balance@example.com", nil)
 		space := testutil.CreateTestSpace(t, dbi.DB, user.ID, "Expense Svc Balance Space")
 
-		testutil.CreateTestExpense(t, dbi.DB, space.ID, user.ID, "Topup", 10000, model.ExpenseTypeTopup)
-		testutil.CreateTestExpense(t, dbi.DB, space.ID, user.ID, "Groceries", 3000, model.ExpenseTypeExpense)
+		testutil.CreateTestExpense(t, dbi.DB, space.ID, user.ID, "Topup", decimal.RequireFromString("100.00"), model.ExpenseTypeTopup)
+		testutil.CreateTestExpense(t, dbi.DB, space.ID, user.ID, "Groceries", decimal.RequireFromString("30.00"), model.ExpenseTypeExpense)
 
 		balance, err := svc.GetBalanceForSpace(space.ID)
 		require.NoError(t, err)
-		assert.Equal(t, 7000, balance)
+		assert.True(t, decimal.RequireFromString("70.00").Equal(balance))
 	})
 }
 
@@ -156,7 +157,7 @@ func TestExpenseService_GetExpensesByTag(t *testing.T) {
 			SpaceID:     space.ID,
 			UserID:      user.ID,
 			Description: "Dinner",
-			Amount:      2500,
+			Amount:      decimal.RequireFromString("25.00"),
 			Type:        model.ExpenseTypeExpense,
 			Date:        now,
 			TagIDs:      []string{tag.ID},
@@ -169,7 +170,7 @@ func TestExpenseService_GetExpensesByTag(t *testing.T) {
 		require.NoError(t, err)
 		require.Len(t, summaries, 1)
 		assert.Equal(t, tag.ID, summaries[0].TagID)
-		assert.Equal(t, 2500, summaries[0].TotalAmount)
+		assert.True(t, decimal.RequireFromString("25.00").Equal(summaries[0].TotalAmount))
 	})
 }
 
@@ -185,7 +186,7 @@ func TestExpenseService_UpdateExpense(t *testing.T) {
 			SpaceID:     space.ID,
 			UserID:      user.ID,
 			Description: "Old Description",
-			Amount:      1000,
+			Amount:      decimal.RequireFromString("10.00"),
 			Type:        model.ExpenseTypeExpense,
 			Date:        time.Now(),
 		})
@@ -195,13 +196,13 @@ func TestExpenseService_UpdateExpense(t *testing.T) {
 			ID:          created.ID,
 			SpaceID:     space.ID,
 			Description: "New Description",
-			Amount:      2000,
+			Amount:      decimal.RequireFromString("20.00"),
 			Type:        model.ExpenseTypeExpense,
 			Date:        time.Now(),
 		})
 		require.NoError(t, err)
 		assert.Equal(t, "New Description", updated.Description)
-		assert.Equal(t, 2000, updated.AmountCents)
+		assert.True(t, decimal.RequireFromString("20.00").Equal(updated.Amount))
 	})
 }
 
@@ -217,7 +218,7 @@ func TestExpenseService_DeleteExpense(t *testing.T) {
 			SpaceID:     space.ID,
 			UserID:      user.ID,
 			Description: "Doomed Expense",
-			Amount:      500,
+			Amount:      decimal.RequireFromString("5.00"),
 			Type:        model.ExpenseTypeExpense,
 			Date:        time.Now(),
 		})

internal/service/loan.go

@@ -7,6 +7,7 @@ import (
 	"git.juancwu.dev/juancwu/budgit/internal/model"
 	"git.juancwu.dev/juancwu/budgit/internal/repository"
 	"github.com/google/uuid"
+	"github.com/shopspring/decimal"
 )
 
 type CreateLoanDTO struct {
@@ -14,7 +15,7 @@ type CreateLoanDTO struct {
 	UserID          string
 	Name            string
 	Description     string
-	OriginalAmount  int
+	OriginalAmount  decimal.Decimal
 	InterestRateBps int
 	StartDate       time.Time
 	EndDate         *time.Time
@@ -24,7 +25,7 @@ type UpdateLoanDTO struct {
 	ID              string
 	Name            string
 	Description     string
-	OriginalAmount  int
+	OriginalAmount  decimal.Decimal
 	InterestRateBps int
 	StartDate       time.Time
 	EndDate         *time.Time
@@ -48,24 +49,24 @@ func (s *LoanService) CreateLoan(dto CreateLoanDTO) (*model.Loan, error) {
 	if dto.Name == "" {
 		return nil, fmt.Errorf("loan name cannot be empty")
 	}
-	if dto.OriginalAmount <= 0 {
+	if dto.OriginalAmount.LessThanOrEqual(decimal.Zero) {
 		return nil, fmt.Errorf("amount must be positive")
 	}
 
 	now := time.Now()
 	loan := &model.Loan{
-		ID:                  uuid.NewString(),
-		SpaceID:             dto.SpaceID,
-		Name:                dto.Name,
-		Description:         dto.Description,
-		OriginalAmountCents: dto.OriginalAmount,
-		InterestRateBps:     dto.InterestRateBps,
-		StartDate:           dto.StartDate,
-		EndDate:             dto.EndDate,
-		IsPaidOff:           false,
-		CreatedBy:           dto.UserID,
-		CreatedAt:           now,
-		UpdatedAt:           now,
+		ID:              uuid.NewString(),
+		SpaceID:         dto.SpaceID,
+		Name:            dto.Name,
+		Description:     dto.Description,
+		OriginalAmount:  dto.OriginalAmount,
+		InterestRateBps: dto.InterestRateBps,
+		StartDate:       dto.StartDate,
+		EndDate:         dto.EndDate,
+		IsPaidOff:       false,
+		CreatedBy:       dto.UserID,
+		CreatedAt:       now,
+		UpdatedAt:       now,
 	}
 
 	if err := s.loanRepo.Create(loan); err != nil {
@@ -95,10 +96,10 @@ func (s *LoanService) GetLoanWithSummary(id string) (*model.LoanWithPaymentSumma
 	}
 
 	return &model.LoanWithPaymentSummary{
-		Loan:           *loan,
-		TotalPaidCents: totalPaid,
-		RemainingCents: loan.OriginalAmountCents - totalPaid,
-		ReceiptCount:   receiptCount,
+		Loan:         *loan,
+		TotalPaid:    totalPaid,
+		Remaining:    loan.OriginalAmount.Sub(totalPaid),
+		ReceiptCount: receiptCount,
 	}, nil
 }
 
@@ -154,10 +155,10 @@ func (s *LoanService) attachSummaries(loans []*model.Loan) ([]*model.LoanWithPay
 			return nil, err
 		}
 		result[i] = &model.LoanWithPaymentSummary{
-			Loan:           *loan,
-			TotalPaidCents: totalPaid,
-			RemainingCents: loan.OriginalAmountCents - totalPaid,
-			ReceiptCount:   receiptCount,
+			Loan:         *loan,
+			TotalPaid:    totalPaid,
+			Remaining:    loan.OriginalAmount.Sub(totalPaid),
+			ReceiptCount: receiptCount,
 		}
 	}
 	return result, nil
@@ -167,7 +168,7 @@ func (s *LoanService) UpdateLoan(dto UpdateLoanDTO) (*model.Loan, error) {
 	if dto.Name == "" {
 		return nil, fmt.Errorf("loan name cannot be empty")
 	}
-	if dto.OriginalAmount <= 0 {
+	if dto.OriginalAmount.LessThanOrEqual(decimal.Zero) {
 		return nil, fmt.Errorf("amount must be positive")
 	}
 
@@ -178,7 +179,7 @@ func (s *LoanService) UpdateLoan(dto UpdateLoanDTO) (*model.Loan, error) {
 
 	existing.Name = dto.Name
 	existing.Description = dto.Description
-	existing.OriginalAmountCents = dto.OriginalAmount
+	existing.OriginalAmount = dto.OriginalAmount
 	existing.InterestRateBps = dto.InterestRateBps
 	existing.StartDate = dto.StartDate
 	existing.EndDate = dto.EndDate

internal/service/money_account.go

@@ -8,6 +8,7 @@ import (
 	"git.juancwu.dev/juancwu/budgit/internal/model"
 	"git.juancwu.dev/juancwu/budgit/internal/repository"
 	"github.com/google/uuid"
+	"github.com/shopspring/decimal"
 )
 
 type CreateMoneyAccountDTO struct {
@@ -23,7 +24,7 @@ type UpdateMoneyAccountDTO struct {
 
 type CreateTransferDTO struct {
 	AccountID string
-	Amount    int
+	Amount    decimal.Decimal
 	Direction model.TransferDirection
 	Note      string
 	CreatedBy string
@@ -77,7 +78,7 @@ func (s *MoneyAccountService) GetAccountsForSpace(spaceID string) ([]model.Money
 		}
 		result[i] = model.MoneyAccountWithBalance{
 			MoneyAccount: *acct,
-			BalanceCents: balance,
+			Balance:      balance,
 		}
 	}
 
@@ -113,8 +114,8 @@ func (s *MoneyAccountService) DeleteAccount(id string) error {
 	return s.accountRepo.Delete(id)
 }
 
-func (s *MoneyAccountService) CreateTransfer(dto CreateTransferDTO, availableSpaceBalance int) (*model.AccountTransfer, error) {
-	if dto.Amount <= 0 {
+func (s *MoneyAccountService) CreateTransfer(dto CreateTransferDTO, availableSpaceBalance decimal.Decimal) (*model.AccountTransfer, error) {
+	if dto.Amount.LessThanOrEqual(decimal.Zero) {
 		return nil, fmt.Errorf("amount must be positive")
 	}
 
@@ -123,7 +124,7 @@ func (s *MoneyAccountService) CreateTransfer(dto CreateTransferDTO, availableSpa
 	}
 
 	if dto.Direction == model.TransferDirectionDeposit {
-		if dto.Amount > availableSpaceBalance {
+		if dto.Amount.GreaterThan(availableSpaceBalance) {
 			return nil, fmt.Errorf("insufficient available balance")
 		}
 	}
@@ -133,19 +134,19 @@ func (s *MoneyAccountService) CreateTransfer(dto CreateTransferDTO, availableSpa
 		if err != nil {
 			return nil, err
 		}
-		if dto.Amount > accountBalance {
+		if dto.Amount.GreaterThan(accountBalance) {
 			return nil, fmt.Errorf("insufficient account balance")
 		}
 	}
 
 	transfer := &model.AccountTransfer{
-		ID:          uuid.NewString(),
-		AccountID:   dto.AccountID,
-		AmountCents: dto.Amount,
-		Direction:   dto.Direction,
-		Note:        strings.TrimSpace(dto.Note),
-		CreatedBy:   dto.CreatedBy,
-		CreatedAt:   time.Now(),
+		ID:        uuid.NewString(),
+		AccountID: dto.AccountID,
+		Amount:    dto.Amount,
+		Direction: dto.Direction,
+		Note:      strings.TrimSpace(dto.Note),
+		CreatedBy: dto.CreatedBy,
+		CreatedAt: time.Now(),
 	}
 
 	err := s.accountRepo.CreateTransfer(transfer)
@@ -164,11 +165,11 @@ func (s *MoneyAccountService) DeleteTransfer(id string) error {
 	return s.accountRepo.DeleteTransfer(id)
 }
 
-func (s *MoneyAccountService) GetAccountBalance(accountID string) (int, error) {
+func (s *MoneyAccountService) GetAccountBalance(accountID string) (decimal.Decimal, error) {
 	return s.accountRepo.GetAccountBalance(accountID)
 }
 
-func (s *MoneyAccountService) GetTotalAllocatedForSpace(spaceID string) (int, error) {
+func (s *MoneyAccountService) GetTotalAllocatedForSpace(spaceID string) (decimal.Decimal, error) {
 	return s.accountRepo.GetTotalAllocatedForSpace(spaceID)
 }
 

internal/service/money_account_test.go

@@ -6,6 +6,7 @@ import (
 	"git.juancwu.dev/juancwu/budgit/internal/model"
 	"git.juancwu.dev/juancwu/budgit/internal/repository"
 	"git.juancwu.dev/juancwu/budgit/internal/testutil"
+	"github.com/shopspring/decimal"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
@@ -53,13 +54,13 @@ func TestMoneyAccountService_GetAccountsForSpace(t *testing.T) {
 		user := testutil.CreateTestUser(t, dbi.DB, "acct-svc-list@example.com", nil)
 		space := testutil.CreateTestSpace(t, dbi.DB, user.ID, "Account Svc List Space")
 		account := testutil.CreateTestMoneyAccount(t, dbi.DB, space.ID, "Checking", user.ID)
-		testutil.CreateTestTransfer(t, dbi.DB, account.ID, 5000, model.TransferDirectionDeposit, user.ID)
+		testutil.CreateTestTransfer(t, dbi.DB, account.ID, decimal.RequireFromString("50.00"), model.TransferDirectionDeposit, user.ID)
 
 		accounts, err := svc.GetAccountsForSpace(space.ID)
 		require.NoError(t, err)
 		require.Len(t, accounts, 1)
 		assert.Equal(t, "Checking", accounts[0].Name)
-		assert.Equal(t, 5000, accounts[0].BalanceCents)
+		assert.True(t, decimal.RequireFromString("50.00").Equal(accounts[0].Balance))
 	})
 }
 
@@ -74,14 +75,14 @@ func TestMoneyAccountService_CreateTransfer_Deposit(t *testing.T) {
 
 		transfer, err := svc.CreateTransfer(CreateTransferDTO{
 			AccountID: account.ID,
-			Amount:    3000,
+			Amount:    decimal.RequireFromString("30.00"),
 			Direction: model.TransferDirectionDeposit,
 			Note:      "Initial deposit",
 			CreatedBy: user.ID,
-		}, 10000)
+		}, decimal.RequireFromString("100.00"))
 		require.NoError(t, err)
 		assert.NotEmpty(t, transfer.ID)
-		assert.Equal(t, 3000, transfer.AmountCents)
+		assert.True(t, decimal.RequireFromString("30.00").Equal(transfer.Amount))
 		assert.Equal(t, model.TransferDirectionDeposit, transfer.Direction)
 	})
 }
@@ -97,11 +98,11 @@ func TestMoneyAccountService_CreateTransfer_InsufficientBalance(t *testing.T) {
 
 		transfer, err := svc.CreateTransfer(CreateTransferDTO{
 			AccountID: account.ID,
-			Amount:    5000,
+			Amount:    decimal.RequireFromString("50.00"),
 			Direction: model.TransferDirectionDeposit,
 			Note:      "Too much",
 			CreatedBy: user.ID,
-		}, 1000)
+		}, decimal.RequireFromString("10.00"))
 		assert.Error(t, err)
 		assert.Nil(t, transfer)
 	})
@@ -115,18 +116,18 @@ func TestMoneyAccountService_CreateTransfer_Withdrawal(t *testing.T) {
 		user := testutil.CreateTestUser(t, dbi.DB, "acct-svc-withdraw@example.com", nil)
 		space := testutil.CreateTestSpace(t, dbi.DB, user.ID, "Account Svc Withdraw Space")
 		account := testutil.CreateTestMoneyAccount(t, dbi.DB, space.ID, "Withdraw Account", user.ID)
-		testutil.CreateTestTransfer(t, dbi.DB, account.ID, 5000, model.TransferDirectionDeposit, user.ID)
+		testutil.CreateTestTransfer(t, dbi.DB, account.ID, decimal.RequireFromString("50.00"), model.TransferDirectionDeposit, user.ID)
 
 		transfer, err := svc.CreateTransfer(CreateTransferDTO{
 			AccountID: account.ID,
-			Amount:    2000,
+			Amount:    decimal.RequireFromString("20.00"),
 			Direction: model.TransferDirectionWithdrawal,
 			Note:      "Withdrawal",
 			CreatedBy: user.ID,
-		}, 0)
+		}, decimal.Zero)
 		require.NoError(t, err)
 		assert.NotEmpty(t, transfer.ID)
-		assert.Equal(t, 2000, transfer.AmountCents)
+		assert.True(t, decimal.RequireFromString("20.00").Equal(transfer.Amount))
 		assert.Equal(t, model.TransferDirectionWithdrawal, transfer.Direction)
 	})
 }
@@ -140,14 +141,14 @@ func TestMoneyAccountService_GetTotalAllocatedForSpace(t *testing.T) {
 		space := testutil.CreateTestSpace(t, dbi.DB, user.ID, "Account Svc Total Space")
 
 		account1 := testutil.CreateTestMoneyAccount(t, dbi.DB, space.ID, "Account 1", user.ID)
-		testutil.CreateTestTransfer(t, dbi.DB, account1.ID, 3000, model.TransferDirectionDeposit, user.ID)
+		testutil.CreateTestTransfer(t, dbi.DB, account1.ID, decimal.RequireFromString("30.00"), model.TransferDirectionDeposit, user.ID)
 
 		account2 := testutil.CreateTestMoneyAccount(t, dbi.DB, space.ID, "Account 2", user.ID)
-		testutil.CreateTestTransfer(t, dbi.DB, account2.ID, 2000, model.TransferDirectionDeposit, user.ID)
+		testutil.CreateTestTransfer(t, dbi.DB, account2.ID, decimal.RequireFromString("20.00"), model.TransferDirectionDeposit, user.ID)
 
 		total, err := svc.GetTotalAllocatedForSpace(space.ID)
 		require.NoError(t, err)
-		assert.Equal(t, 5000, total)
+		assert.True(t, decimal.RequireFromString("50.00").Equal(total))
 	})
 }
 
@@ -177,7 +178,7 @@ func TestMoneyAccountService_DeleteTransfer(t *testing.T) {
 		user := testutil.CreateTestUser(t, dbi.DB, "acct-svc-deltx@example.com", nil)
 		space := testutil.CreateTestSpace(t, dbi.DB, user.ID, "Account Svc DelTx Space")
 		account := testutil.CreateTestMoneyAccount(t, dbi.DB, space.ID, "DelTx Account", user.ID)
-		transfer := testutil.CreateTestTransfer(t, dbi.DB, account.ID, 1000, model.TransferDirectionDeposit, user.ID)
+		transfer := testutil.CreateTestTransfer(t, dbi.DB, account.ID, decimal.RequireFromString("10.00"), model.TransferDirectionDeposit, user.ID)
 
 		err := svc.DeleteTransfer(transfer.ID)
 		require.NoError(t, err)

internal/service/receipt.go

@@ -7,12 +7,13 @@ import (
 	"git.juancwu.dev/juancwu/budgit/internal/model"
 	"git.juancwu.dev/juancwu/budgit/internal/repository"
 	"github.com/google/uuid"
+	"github.com/shopspring/decimal"
 )
 
 type FundingSourceDTO struct {
 	SourceType model.FundingSourceType
 	AccountID  string
-	Amount     int
+	Amount     decimal.Decimal
 }
 
 type CreateReceiptDTO struct {
@@ -20,7 +21,7 @@ type CreateReceiptDTO struct {
 	SpaceID            string
 	UserID             string
 	Description        string
-	TotalAmount        int
+	TotalAmount        decimal.Decimal
 	Date               time.Time
 	FundingSources     []FundingSourceDTO
 	RecurringReceiptID *string
@@ -31,7 +32,7 @@ type UpdateReceiptDTO struct {
 	SpaceID        string
 	UserID         string
 	Description    string
-	TotalAmount    int
+	TotalAmount    decimal.Decimal
 	Date           time.Time
 	FundingSources []FundingSourceDTO
 }
@@ -57,7 +58,7 @@ func NewReceiptService(
 }
 
 func (s *ReceiptService) CreateReceipt(dto CreateReceiptDTO) (*model.ReceiptWithSources, error) {
-	if dto.TotalAmount <= 0 {
+	if dto.TotalAmount.LessThanOrEqual(decimal.Zero) {
 		return nil, fmt.Errorf("amount must be positive")
 	}
 	if len(dto.FundingSources) == 0 {
@@ -65,15 +66,15 @@ func (s *ReceiptService) CreateReceipt(dto CreateReceiptDTO) (*model.ReceiptWith
 	}
 
 	// Validate funding sources sum to total
-	var sum int
+	sum := decimal.Zero
 	for _, src := range dto.FundingSources {
-		if src.Amount <= 0 {
+		if src.Amount.LessThanOrEqual(decimal.Zero) {
 			return nil, fmt.Errorf("each funding source amount must be positive")
 		}
-		sum += src.Amount
+		sum = sum.Add(src.Amount)
 	}
-	if sum != dto.TotalAmount {
-		return nil, fmt.Errorf("funding source amounts (%d) must equal total amount (%d)", sum, dto.TotalAmount)
+	if !sum.Equal(dto.TotalAmount) {
+		return nil, fmt.Errorf("funding source amounts (%s) must equal total amount (%s)", sum, dto.TotalAmount)
 	}
 
 	// Validate loan exists and is not paid off
@@ -91,7 +92,7 @@ func (s *ReceiptService) CreateReceipt(dto CreateReceiptDTO) (*model.ReceiptWith
 		LoanID:             dto.LoanID,
 		SpaceID:            dto.SpaceID,
 		Description:        dto.Description,
-		TotalAmountCents:   dto.TotalAmount,
+		TotalAmount:        dto.TotalAmount,
 		Date:               dto.Date,
 		RecurringReceiptID: dto.RecurringReceiptID,
 		CreatedBy:          dto.UserID,
@@ -107,7 +108,7 @@ func (s *ReceiptService) CreateReceipt(dto CreateReceiptDTO) (*model.ReceiptWith
 
 	// Check if loan is now fully paid off
 	totalPaid, err := s.loanRepo.GetTotalPaidForLoan(dto.LoanID)
-	if err == nil && totalPaid >= loan.OriginalAmountCents {
+	if err == nil && totalPaid.GreaterThanOrEqual(loan.OriginalAmount) {
 		_ = s.loanRepo.SetPaidOff(loan.ID, true)
 	}
 
@@ -127,10 +128,10 @@ func (s *ReceiptService) buildLinkedRecords(
 
 	for _, src := range fundingSources {
 		fs := model.ReceiptFundingSource{
-			ID:          uuid.NewString(),
-			ReceiptID:   receipt.ID,
-			SourceType:  src.SourceType,
-			AmountCents: src.Amount,
+			ID:         uuid.NewString(),
+			ReceiptID:  receipt.ID,
+			SourceType: src.SourceType,
+			Amount:     src.Amount,
 		}
 
 		if src.SourceType == model.FundingSourceBalance {
@@ -139,7 +140,7 @@ func (s *ReceiptService) buildLinkedRecords(
 				SpaceID:     spaceID,
 				CreatedBy:   userID,
 				Description: fmt.Sprintf("Loan payment: %s", description),
-				AmountCents: src.Amount,
+				Amount:      src.Amount,
 				Type:        model.ExpenseTypeExpense,
 				Date:        date,
 				CreatedAt:   now,
@@ -151,13 +152,13 @@ func (s *ReceiptService) buildLinkedRecords(
 			acctID := src.AccountID
 			fs.AccountID = &acctID
 			transfer := &model.AccountTransfer{
-				ID:          uuid.NewString(),
-				AccountID:   src.AccountID,
-				AmountCents: src.Amount,
-				Direction:   model.TransferDirectionWithdrawal,
-				Note:        fmt.Sprintf("Loan payment: %s", description),
-				CreatedBy:   userID,
-				CreatedAt:   now,
+				ID:        uuid.NewString(),
+				AccountID: src.AccountID,
+				Amount:    src.Amount,
+				Direction: model.TransferDirectionWithdrawal,
+				Note:      fmt.Sprintf("Loan payment: %s", description),
+				CreatedBy: userID,
+				CreatedAt: now,
 			}
 			accountTransfers = append(accountTransfers, transfer)
 			fs.LinkedTransferID = &transfer.ID
@@ -255,7 +256,7 @@ func (s *ReceiptService) DeleteReceipt(id string, spaceID string) error {
 	if err != nil {
 		return nil
 	}
-	if loan.IsPaidOff && totalPaid < loan.OriginalAmountCents {
+	if loan.IsPaidOff && totalPaid.LessThan(loan.OriginalAmount) {
 		_ = s.loanRepo.SetPaidOff(loan.ID, false)
 	}
 
@@ -263,22 +264,22 @@ func (s *ReceiptService) DeleteReceipt(id string, spaceID string) error {
 }
 
 func (s *ReceiptService) UpdateReceipt(dto UpdateReceiptDTO) (*model.ReceiptWithSources, error) {
-	if dto.TotalAmount <= 0 {
+	if dto.TotalAmount.LessThanOrEqual(decimal.Zero) {
 		return nil, fmt.Errorf("amount must be positive")
 	}
 	if len(dto.FundingSources) == 0 {
 		return nil, fmt.Errorf("at least one funding source is required")
 	}
 
-	var sum int
+	sum := decimal.Zero
 	for _, src := range dto.FundingSources {
-		if src.Amount <= 0 {
+		if src.Amount.LessThanOrEqual(decimal.Zero) {
 			return nil, fmt.Errorf("each funding source amount must be positive")
 		}
-		sum += src.Amount
+		sum = sum.Add(src.Amount)
 	}
-	if sum != dto.TotalAmount {
-		return nil, fmt.Errorf("funding source amounts (%d) must equal total amount (%d)", sum, dto.TotalAmount)
+	if !sum.Equal(dto.TotalAmount) {
+		return nil, fmt.Errorf("funding source amounts (%s) must equal total amount (%s)", sum, dto.TotalAmount)
 	}
 
 	existing, err := s.receiptRepo.GetByID(dto.ID)
@@ -290,7 +291,7 @@ func (s *ReceiptService) UpdateReceipt(dto UpdateReceiptDTO) (*model.ReceiptWith
 	}
 
 	existing.Description = dto.Description
-	existing.TotalAmountCents = dto.TotalAmount
+	existing.TotalAmount = dto.TotalAmount
 	existing.Date = dto.Date
 	existing.UpdatedAt = time.Now()
 
@@ -305,9 +306,9 @@ func (s *ReceiptService) UpdateReceipt(dto UpdateReceiptDTO) (*model.ReceiptWith
 	if err == nil {
 		totalPaid, err := s.loanRepo.GetTotalPaidForLoan(existing.LoanID)
 		if err == nil {
-			if totalPaid >= loan.OriginalAmountCents && !loan.IsPaidOff {
+			if totalPaid.GreaterThanOrEqual(loan.OriginalAmount) && !loan.IsPaidOff {
 				_ = s.loanRepo.SetPaidOff(loan.ID, true)
-			} else if totalPaid < loan.OriginalAmountCents && loan.IsPaidOff {
+			} else if totalPaid.LessThan(loan.OriginalAmount) && loan.IsPaidOff {
 				_ = s.loanRepo.SetPaidOff(loan.ID, false)
 			}
 		}

internal/service/recurring_expense.go

@@ -8,13 +8,14 @@ import (
 	"git.juancwu.dev/juancwu/budgit/internal/model"
 	"git.juancwu.dev/juancwu/budgit/internal/repository"
 	"github.com/google/uuid"
+	"github.com/shopspring/decimal"
 )
 
 type CreateRecurringExpenseDTO struct {
 	SpaceID         string
 	UserID          string
 	Description     string
-	Amount          int
+	Amount          decimal.Decimal
 	Type            model.ExpenseType
 	PaymentMethodID *string
 	Frequency       model.Frequency
@@ -26,7 +27,7 @@ type CreateRecurringExpenseDTO struct {
 type UpdateRecurringExpenseDTO struct {
 	ID              string
 	Description     string
-	Amount          int
+	Amount          decimal.Decimal
 	Type            model.ExpenseType
 	PaymentMethodID *string
 	Frequency       model.Frequency
@@ -55,7 +56,7 @@ func (s *RecurringExpenseService) CreateRecurringExpense(dto CreateRecurringExpe
 	if dto.Description == "" {
 		return nil, fmt.Errorf("description cannot be empty")
 	}
-	if dto.Amount <= 0 {
+	if dto.Amount.LessThanOrEqual(decimal.Zero) {
 		return nil, fmt.Errorf("amount must be positive")
 	}
 
@@ -65,7 +66,7 @@ func (s *RecurringExpenseService) CreateRecurringExpense(dto CreateRecurringExpe
 		SpaceID:         dto.SpaceID,
 		CreatedBy:       dto.UserID,
 		Description:     dto.Description,
-		AmountCents:     dto.Amount,
+		Amount:          dto.Amount,
 		Type:            dto.Type,
 		PaymentMethodID: dto.PaymentMethodID,
 		Frequency:       dto.Frequency,
@@ -127,7 +128,7 @@ func (s *RecurringExpenseService) UpdateRecurringExpense(dto UpdateRecurringExpe
 	if dto.Description == "" {
 		return nil, fmt.Errorf("description cannot be empty")
 	}
-	if dto.Amount <= 0 {
+	if dto.Amount.LessThanOrEqual(decimal.Zero) {
 		return nil, fmt.Errorf("amount must be positive")
 	}
 
@@ -137,7 +138,7 @@ func (s *RecurringExpenseService) UpdateRecurringExpense(dto UpdateRecurringExpe
 	}
 
 	existing.Description = dto.Description
-	existing.AmountCents = dto.Amount
+	existing.Amount = dto.Amount
 	existing.Type = dto.Type
 	existing.PaymentMethodID = dto.PaymentMethodID
 	existing.Frequency = dto.Frequency
@@ -229,7 +230,7 @@ func (s *RecurringExpenseService) processRecurrence(re *model.RecurringExpense,
 			SpaceID:            re.SpaceID,
 			CreatedBy:          re.CreatedBy,
 			Description:        re.Description,
-			AmountCents:        re.AmountCents,
+			Amount:             re.Amount,
 			Type:               re.Type,
 			Date:               re.NextOccurrence,
 			PaymentMethodID:    re.PaymentMethodID,

internal/service/recurring_receipt.go

@@ -8,6 +8,7 @@ import (
 	"git.juancwu.dev/juancwu/budgit/internal/model"
 	"git.juancwu.dev/juancwu/budgit/internal/repository"
 	"github.com/google/uuid"
+	"github.com/shopspring/decimal"
 )
 
 type CreateRecurringReceiptDTO struct {
@@ -15,7 +16,7 @@ type CreateRecurringReceiptDTO struct {
 	SpaceID        string
 	UserID         string
 	Description    string
-	TotalAmount    int
+	TotalAmount    decimal.Decimal
 	Frequency      model.Frequency
 	StartDate      time.Time
 	EndDate        *time.Time
@@ -25,7 +26,7 @@ type CreateRecurringReceiptDTO struct {
 type UpdateRecurringReceiptDTO struct {
 	ID             string
 	Description    string
-	TotalAmount    int
+	TotalAmount    decimal.Decimal
 	Frequency      model.Frequency
 	StartDate      time.Time
 	EndDate        *time.Time
@@ -57,36 +58,36 @@ func NewRecurringReceiptService(
 }
 
 func (s *RecurringReceiptService) CreateRecurringReceipt(dto CreateRecurringReceiptDTO) (*model.RecurringReceiptWithSources, error) {
-	if dto.TotalAmount <= 0 {
+	if dto.TotalAmount.LessThanOrEqual(decimal.Zero) {
 		return nil, fmt.Errorf("amount must be positive")
 	}
 	if len(dto.FundingSources) == 0 {
 		return nil, fmt.Errorf("at least one funding source is required")
 	}
 
-	var sum int
+	sum := decimal.Zero
 	for _, src := range dto.FundingSources {
-		sum += src.Amount
+		sum = sum.Add(src.Amount)
 	}
-	if sum != dto.TotalAmount {
+	if !sum.Equal(dto.TotalAmount) {
 		return nil, fmt.Errorf("funding source amounts must equal total amount")
 	}
 
 	now := time.Now()
 	rr := &model.RecurringReceipt{
-		ID:               uuid.NewString(),
-		LoanID:           dto.LoanID,
-		SpaceID:          dto.SpaceID,
-		Description:      dto.Description,
-		TotalAmountCents: dto.TotalAmount,
-		Frequency:        dto.Frequency,
-		StartDate:        dto.StartDate,
-		EndDate:          dto.EndDate,
-		NextOccurrence:   dto.StartDate,
-		IsActive:         true,
-		CreatedBy:        dto.UserID,
-		CreatedAt:        now,
-		UpdatedAt:        now,
+		ID:             uuid.NewString(),
+		LoanID:         dto.LoanID,
+		SpaceID:        dto.SpaceID,
+		Description:    dto.Description,
+		TotalAmount:    dto.TotalAmount,
+		Frequency:      dto.Frequency,
+		StartDate:      dto.StartDate,
+		EndDate:        dto.EndDate,
+		NextOccurrence: dto.StartDate,
+		IsActive:       true,
+		CreatedBy:      dto.UserID,
+		CreatedAt:      now,
+		UpdatedAt:      now,
 	}
 
 	sources := make([]model.RecurringReceiptSource, len(dto.FundingSources))
@@ -95,7 +96,7 @@ func (s *RecurringReceiptService) CreateRecurringReceipt(dto CreateRecurringRece
 			ID:                 uuid.NewString(),
 			RecurringReceiptID: rr.ID,
 			SourceType:         src.SourceType,
-			AmountCents:        src.Amount,
+			Amount:             src.Amount,
 		}
 		if src.SourceType == model.FundingSourceAccount {
 			acctID := src.AccountID
@@ -142,7 +143,7 @@ func (s *RecurringReceiptService) GetRecurringReceiptsWithSourcesForLoan(loanID
 }
 
 func (s *RecurringReceiptService) UpdateRecurringReceipt(dto UpdateRecurringReceiptDTO) (*model.RecurringReceipt, error) {
-	if dto.TotalAmount <= 0 {
+	if dto.TotalAmount.LessThanOrEqual(decimal.Zero) {
 		return nil, fmt.Errorf("amount must be positive")
 	}
 
@@ -152,7 +153,7 @@ func (s *RecurringReceiptService) UpdateRecurringReceipt(dto UpdateRecurringRece
 	}
 
 	existing.Description = dto.Description
-	existing.TotalAmountCents = dto.TotalAmount
+	existing.TotalAmount = dto.TotalAmount
 	existing.Frequency = dto.Frequency
 	existing.StartDate = dto.StartDate
 	existing.EndDate = dto.EndDate
@@ -168,7 +169,7 @@ func (s *RecurringReceiptService) UpdateRecurringReceipt(dto UpdateRecurringRece
 			ID:                 uuid.NewString(),
 			RecurringReceiptID: existing.ID,
 			SourceType:         src.SourceType,
-			AmountCents:        src.Amount,
+			Amount:             src.Amount,
 		}
 		if src.SourceType == model.FundingSourceAccount {
 			acctID := src.AccountID
@@ -262,7 +263,7 @@ func (s *RecurringReceiptService) processRecurrence(rr *model.RecurringReceipt,
 			fundingSources[i] = FundingSourceDTO{
 				SourceType: src.SourceType,
 				AccountID:  accountID,
-				Amount:     src.AmountCents,
+				Amount:     src.Amount,
 			}
 		}
 
@@ -272,7 +273,7 @@ func (s *RecurringReceiptService) processRecurrence(rr *model.RecurringReceipt,
 			SpaceID:            rr.SpaceID,
 			UserID:             rr.CreatedBy,
 			Description:        rr.Description,
-			TotalAmount:        rr.TotalAmountCents,
+			TotalAmount:        rr.TotalAmount,
 			Date:               rr.NextOccurrence,
 			FundingSources:     fundingSources,
 			RecurringReceiptID: &rrID,

internal/service/report.go

@@ -73,7 +73,7 @@ func (s *ReportService) GetSpendingReport(spaceID string, from, to time.Time) (*
 		TopExpenses:     topWithTags,
 		TotalIncome:     totalIncome,
 		TotalExpenses:   totalExpenses,
-		NetBalance:      totalIncome - totalExpenses,
+		NetBalance:      totalIncome.Sub(totalExpenses),
 	}, nil
 }