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fix: transfer exceeding available balance allowed
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juancwu 2026-05-04 15:06:12 +00:00
commit f6a873ffc8
4 changed files with 160 additions and 29 deletions
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1
internal/app/app.go
View file

@ -66,6 +66,7 @@ func New(cfg *config.Config) (*App, error) {
allocationService.SetAuditLogger(auditLogService)
transactionService := service.NewTransactionService(transactionRepository, categoryRepository, accountService)
transactionService.SetAuditLogger(txAuditLogService)
transactionService.SetAllocationService(allocationService)
accountActivityService := service.NewAccountActivityService(auditLogService, txAuditLogService)
emailService := service.NewEmailService(
emailClient,

5
internal/handler/space.go
View file

@ -1842,6 +1842,11 @@ func (h *spaceHandler) HandleCreateTransfer(w http.ResponseWriter, r *http.Reque
Description: descriptionInput,
ActorID: actorID,
}); err != nil {
if errors.Is(err, service.ErrTransferExceedsAvailable) {
formProps.AmountErr = "Amount exceeds the available balance for this account."
ui.Render(w, r, forms.CreateTransfer(formProps))
return
}
slog.Error("failed to create transfer", "error", err, "source", accountID, "dest", destInput)
formProps.GeneralErr = "Something went wrong. Please try again."
ui.Render(w, r, forms.CreateTransfer(formProps))

35
internal/service/transaction.go
View file

@ -19,11 +19,18 @@ import (
// instead.
var ErrTransactionPartOfTransfer = errors.New("transaction is part of a transfer")
// ErrTransferExceedsAvailable is returned when a transfer would move more
// funds out of the source than its available balance (balance minus
// allocations). Bills can still overdraft, but transfers must respect what
// has already been allocated to other purposes.
var ErrTransferExceedsAvailable = errors.New("transfer amount exceeds available balance")
type TransactionService struct {
transactionRepo repository.TransactionRepository
categoryRepo repository.CategoryRepository
accountService *AccountService
auditSvc *TransactionAuditLogService
transactionRepo repository.TransactionRepository
categoryRepo repository.CategoryRepository
accountService *AccountService
allocationService *AllocationService
auditSvc *TransactionAuditLogService
}
func NewTransactionService(
@ -43,6 +50,13 @@ func (s *TransactionService) SetAuditLogger(audit *TransactionAuditLogService) {
s.auditSvc = audit
}
// SetAllocationService wires the allocation service so transfers can enforce
// the available-balance constraint. Wired after construction to break the
// circular dependency between allocation and transaction services.
func (s *TransactionService) SetAllocationService(alloc *AllocationService) {
s.allocationService = alloc
}
type PayBillInput struct {
AccountID string
Title string
@ -239,6 +253,19 @@ func (s *TransactionService) Transfer(input TransferInput) (*TransferResult, err
return nil, fmt.Errorf("failed to load destination account: %w", err)
}
// Transfers must respect allocations on the source. A transfer is the user
// committing funds elsewhere — if the unallocated cash isn't there, the
// transfer can't happen. (Bills are still allowed to overdraft.)
if s.allocationService != nil {
summary, err := s.allocationService.SummaryForAccount(source.ID)
if err != nil {
return nil, fmt.Errorf("failed to load source allocations: %w", err)
}
if input.Amount.GreaterThan(summary.Available) {
return nil, ErrTransferExceedsAvailable
}
}
// Cross-currency transfers require a conversion rate; same-currency
// transfers ignore it (or, for symmetry, accept rate=1).
destAmount := input.Amount

148
internal/service/transaction_test.go
View file

@ -29,12 +29,16 @@ func newTxnFixture(t *testing.T, dbi testutil.DBInfo) *txnFixture {
txnRepo := repository.NewTransactionRepository(dbi.DB)
categoryRepo := repository.NewCategoryRepository(dbi.DB)
accountRepo := repository.NewAccountRepository(dbi.DB)
allocationRepo := repository.NewAllocationRepository(dbi.DB)
auditRepo := repository.NewTransactionAuditLogRepository(dbi.DB)
accountSvc := NewAccountService(accountRepo)
accountSvc.SetAllocationRepository(allocationRepo)
allocationSvc := NewAllocationService(allocationRepo, accountSvc)
auditSvc := NewTransactionAuditLogService(auditRepo)
svc := NewTransactionService(txnRepo, categoryRepo, accountSvc)
svc.SetAuditLogger(auditSvc)
svc.SetAllocationService(allocationSvc)
user := testutil.CreateTestUser(t, dbi.DB, t.Name()+"@example.com", nil)
space := testutil.CreateTestSpace(t, dbi.DB, user.ID, "S")
@ -251,6 +255,13 @@ func TestTransactionService_Transfer_HappyPath(t *testing.T) {
f := newTxnFixture(t, dbi)
dest := testutil.CreateTestAccount(t, dbi.DB, f.account.SpaceID, "Savings")
// Seed source so the transfer respects the available-balance constraint.
_, err := f.svc.Deposit(DepositInput{
AccountID: f.account.ID, Title: "seed", Amount: decimal.NewFromInt(50),
OccurredAt: time.Now(), ActorID: f.user.ID,
})
require.NoError(t, err)
result, err := f.svc.Transfer(TransferInput{
SourceAccountID: f.account.ID,
DestAccountID: dest.ID,
@ -267,10 +278,9 @@ func TestTransactionService_Transfer_HappyPath(t *testing.T) {
assert.Equal(t, f.account.ID, result.Withdrawal.AccountID)
assert.Equal(t, dest.ID, result.Deposit.AccountID)
// Source went from 0 → -50 (overdraft allowed); dest 0 → +50.
src, err := f.accounts.ByID(f.account.ID)
require.NoError(t, err)
assert.True(t, decimal.NewFromInt(-50).Equal(src.Balance))
assert.True(t, decimal.Zero.Equal(src.Balance))
dst, err := f.accounts.ByID(dest.ID)
require.NoError(t, err)
assert.True(t, decimal.NewFromInt(50).Equal(dst.Balance))
@ -301,12 +311,12 @@ func TestTransactionService_Transfer_HappyPath(t *testing.T) {
})
}
func TestTransactionService_Transfer_AllowsOverdraft(t *testing.T) {
func TestTransactionService_Transfer_RejectsOverdraft(t *testing.T) {
testutil.ForEachDB(t, func(t *testing.T, dbi testutil.DBInfo) {
f := newTxnFixture(t, dbi)
dest := testutil.CreateTestAccount(t, dbi.DB, f.account.SpaceID, "B")
// Seed source to 100, then transfer 200 → -100.
// Seed source to 100, then attempt to transfer 200 — must be refused.
_, err := f.svc.Deposit(DepositInput{
AccountID: f.account.ID, Title: "seed", Amount: decimal.NewFromInt(100),
OccurredAt: time.Now(), ActorID: f.user.ID,
@ -316,22 +326,15 @@ func TestTransactionService_Transfer_AllowsOverdraft(t *testing.T) {
SourceAccountID: f.account.ID, DestAccountID: dest.ID,
Title: "T1", Amount: decimal.NewFromInt(200), OccurredAt: time.Now(), ActorID: f.user.ID,
})
require.NoError(t, err)
require.ErrorIs(t, err, ErrTransferExceedsAvailable)
// Balances are untouched.
src, err := f.accounts.ByID(f.account.ID)
require.NoError(t, err)
assert.True(t, decimal.NewFromInt(-100).Equal(src.Balance), "expected -100, got %s", src.Balance.String())
// Transfer another 200 from -100 → -300.
_, err = f.svc.Transfer(TransferInput{
SourceAccountID: f.account.ID, DestAccountID: dest.ID,
Title: "T2", Amount: decimal.NewFromInt(200), OccurredAt: time.Now(), ActorID: f.user.ID,
})
assert.True(t, decimal.NewFromInt(100).Equal(src.Balance))
dst, err := f.accounts.ByID(dest.ID)
require.NoError(t, err)
src, err = f.accounts.ByID(f.account.ID)
require.NoError(t, err)
assert.True(t, decimal.NewFromInt(-300).Equal(src.Balance), "expected -300, got %s", src.Balance.String())
assert.True(t, decimal.Zero.Equal(dst.Balance))
})
}
@ -351,6 +354,13 @@ func TestTransactionService_Transfer_AppearsInActivityFeeds(t *testing.T) {
NewTransactionAuditLogService(f.txAudit),
)
// Seed source so the transfer respects the available-balance constraint.
_, err := f.svc.Deposit(DepositInput{
AccountID: f.account.ID, Title: "seed", Amount: decimal.NewFromInt(75),
OccurredAt: time.Now(), ActorID: f.user.ID,
})
require.NoError(t, err)
result, err := f.svc.Transfer(TransferInput{
SourceAccountID: f.account.ID,
DestAccountID: dest.ID,
@ -361,10 +371,11 @@ func TestTransactionService_Transfer_AppearsInActivityFeeds(t *testing.T) {
})
require.NoError(t, err)
// Source account activity sees the withdrawal half.
// Source account activity sees the withdrawal half (newest first; the
// seed deposit appears below).
srcRows, err := activitySvc.List(f.account.ID, 10, 0)
require.NoError(t, err)
require.Len(t, srcRows, 1, "source account feed should include the withdrawal half")
require.Len(t, srcRows, 2, "source account feed should include the seed deposit and the withdrawal half")
require.NotNil(t, srcRows[0].TxLog)
assert.Equal(t, result.Withdrawal.ID, srcRows[0].TxLog.TransactionID)
assertTransferRole(t, srcRows[0].TxLog, "source", dest.ID)
@ -377,10 +388,10 @@ func TestTransactionService_Transfer_AppearsInActivityFeeds(t *testing.T) {
assert.Equal(t, result.Deposit.ID, dstRows[0].TxLog.TransactionID)
assertTransferRole(t, dstRows[0].TxLog, "destination", f.account.ID)
// Space-level activity feed sees both halves.
// Space-level activity feed sees both transfer halves alongside the seed.
spaceRows, err := activitySvc.ListSpace(f.account.SpaceID, 10, 0)
require.NoError(t, err)
require.Len(t, spaceRows, 2, "space feed should include both halves of the transfer")
require.Len(t, spaceRows, 3, "space feed should include the seed deposit and both transfer halves")
ids := []string{}
for _, r := range spaceRows {
require.NotNil(t, r.TxLog)
@ -392,15 +403,13 @@ func TestTransactionService_Transfer_AppearsInActivityFeeds(t *testing.T) {
// Counts agree with what the feed returns (pagination relies on this).
srcCount, err := activitySvc.Count(f.account.ID)
require.NoError(t, err)
assert.Equal(t, 1, srcCount)
assert.Equal(t, 2, srcCount)
dstCount, err := activitySvc.Count(dest.ID)
require.NoError(t, err)
assert.Equal(t, 1, dstCount)
spaceCount, err := activitySvc.CountSpace(f.account.SpaceID)
require.NoError(t, err)
// Source account had no activity before the transfer, dest is brand-new;
// the only activity in the space is the two transfer halves.
assert.Equal(t, 2, spaceCount)
assert.Equal(t, 3, spaceCount)
})
}
@ -444,6 +453,12 @@ func TestTransactionService_Update_RejectsTransferTransactions(t *testing.T) {
f := newTxnFixture(t, dbi)
dest := testutil.CreateTestAccount(t, dbi.DB, f.account.SpaceID, "Savings")
_, err := f.svc.Deposit(DepositInput{
AccountID: f.account.ID, Title: "seed", Amount: decimal.NewFromInt(20),
OccurredAt: time.Now(), ActorID: f.user.ID,
})
require.NoError(t, err)
result, err := f.svc.Transfer(TransferInput{
SourceAccountID: f.account.ID,
DestAccountID: dest.ID,
@ -572,6 +587,12 @@ func TestTransactionService_DeleteTransaction_RejectsTransferHalves(t *testing.T
f := newTxnFixture(t, dbi)
dest := testutil.CreateTestAccount(t, dbi.DB, f.account.SpaceID, "Savings")
_, err := f.svc.Deposit(DepositInput{
AccountID: f.account.ID, Title: "seed", Amount: decimal.NewFromInt(20),
OccurredAt: time.Now(), ActorID: f.user.ID,
})
require.NoError(t, err)
result, err := f.svc.Transfer(TransferInput{
SourceAccountID: f.account.ID,
DestAccountID: dest.ID,
@ -602,7 +623,7 @@ func TestTransactionService_DeleteTransaction_RejectsTransferHalves(t *testing.T
src, err := f.accounts.ByID(f.account.ID)
require.NoError(t, err)
assert.True(t, decimal.NewFromInt(-20).Equal(src.Balance))
assert.True(t, decimal.Zero.Equal(src.Balance))
dst, err := f.accounts.ByID(dest.ID)
require.NoError(t, err)
assert.True(t, decimal.NewFromInt(20).Equal(dst.Balance))
@ -662,6 +683,83 @@ func TestTransactionService_DeleteTransaction_RequiresID(t *testing.T) {
})
}
func TestTransactionService_Transfer_RejectsExceedingAvailable(t *testing.T) {
testutil.ForEachDB(t, func(t *testing.T, dbi testutil.DBInfo) {
f := newTxnFixture(t, dbi)
dest := testutil.CreateTestAccount(t, dbi.DB, f.account.SpaceID, "Savings")
allocRepo := repository.NewAllocationRepository(dbi.DB)
allocSvc := NewAllocationService(allocRepo, NewAccountService(repository.NewAccountRepository(dbi.DB)))
allocSvc.SetAuditLogger(NewSpaceAuditLogService(repository.NewSpaceAuditLogRepository(dbi.DB)))
// Source: balance 100, allocate 60 → available 40.
_, err := f.svc.Deposit(DepositInput{
AccountID: f.account.ID, Title: "seed", Amount: decimal.NewFromInt(100),
OccurredAt: time.Now(), ActorID: f.user.ID,
})
require.NoError(t, err)
_, err = allocSvc.Create(CreateAllocationInput{
AccountID: f.account.ID, Name: "Rent", Amount: decimal.NewFromInt(60), ActorID: f.user.ID,
})
require.NoError(t, err)
// 50 > 40 available, must be refused.
_, err = f.svc.Transfer(TransferInput{
SourceAccountID: f.account.ID, DestAccountID: dest.ID,
Title: "Too much", Amount: decimal.NewFromInt(50), OccurredAt: time.Now(), ActorID: f.user.ID,
})
require.ErrorIs(t, err, ErrTransferExceedsAvailable)
// Balances untouched.
src, err := f.accounts.ByID(f.account.ID)
require.NoError(t, err)
assert.True(t, decimal.NewFromInt(100).Equal(src.Balance))
dst, err := f.accounts.ByID(dest.ID)
require.NoError(t, err)
assert.True(t, decimal.Zero.Equal(dst.Balance))
// 40 (== available) is allowed.
_, err = f.svc.Transfer(TransferInput{
SourceAccountID: f.account.ID, DestAccountID: dest.ID,
Title: "Exact", Amount: decimal.NewFromInt(40), OccurredAt: time.Now(), ActorID: f.user.ID,
})
require.NoError(t, err)
src, err = f.accounts.ByID(f.account.ID)
require.NoError(t, err)
assert.True(t, decimal.NewFromInt(60).Equal(src.Balance))
dst, err = f.accounts.ByID(dest.ID)
require.NoError(t, err)
assert.True(t, decimal.NewFromInt(40).Equal(dst.Balance))
})
}
func TestTransactionService_Transfer_AllowsUpToAvailable_NoAllocations(t *testing.T) {
testutil.ForEachDB(t, func(t *testing.T, dbi testutil.DBInfo) {
f := newTxnFixture(t, dbi)
dest := testutil.CreateTestAccount(t, dbi.DB, f.account.SpaceID, "Savings")
// With no allocations, available == balance, so transferring the full
// balance is allowed but transferring more is not.
_, err := f.svc.Deposit(DepositInput{
AccountID: f.account.ID, Title: "seed", Amount: decimal.NewFromInt(30),
OccurredAt: time.Now(), ActorID: f.user.ID,
})
require.NoError(t, err)
_, err = f.svc.Transfer(TransferInput{
SourceAccountID: f.account.ID, DestAccountID: dest.ID,
Title: "Over", Amount: decimal.NewFromInt(31), OccurredAt: time.Now(), ActorID: f.user.ID,
})
require.ErrorIs(t, err, ErrTransferExceedsAvailable)
_, err = f.svc.Transfer(TransferInput{
SourceAccountID: f.account.ID, DestAccountID: dest.ID,
Title: "Full", Amount: decimal.NewFromInt(30), OccurredAt: time.Now(), ActorID: f.user.ID,
})
require.NoError(t, err)
})
}
func TestTransactionService_Validations(t *testing.T) {
testutil.ForEachDB(t, func(t *testing.T, dbi testutil.DBInfo) {
f := newTxnFixture(t, dbi)