accounts: Credit and debit accounts kvdb additions prep

accounts/interface.go

@@ -225,9 +225,14 @@ type Store interface {
 	AddAccountInvoice(ctx context.Context, id AccountID,
 		hash lntypes.Hash) error
 
-	// IncreaseAccountBalance increases the balance of the account with the
+	// CreditAccount increases the balance of the account with the
 	// given ID by the given amount.
-	IncreaseAccountBalance(ctx context.Context, id AccountID,
+	CreditAccount(ctx context.Context, id AccountID,
+		amount lnwire.MilliSatoshi) error
+
+	// DebitAccount decreases the balance of the account with the
+	// given ID by the given amount.
+	DebitAccount(ctx context.Context, id AccountID,
 		amount lnwire.MilliSatoshi) error
 
 	// UpsertAccountPayment updates or inserts a payment entry for the given

accounts/service.go

@@ -563,7 +563,7 @@ func (s *InterceptorService) invoiceUpdate(ctx context.Context,
 	// If we get here, the current account has the invoice associated with
 	// it that was just paid. Credit the amount to the account and update it
 	// in the DB.
-	err := s.store.IncreaseAccountBalance(ctx, acctID, invoice.AmountPaid)
+	err := s.store.CreditAccount(ctx, acctID, invoice.AmountPaid)
 	if err != nil {
 		return s.disableAndErrorfUnsafe("error increasing account "+
 			"balance account: %w", err)

accounts/store_kvdb.go

@@ -223,11 +223,11 @@ func (s *BoltStore) AddAccountInvoice(_ context.Context, id AccountID,
 	return s.updateAccount(id, update)
 }
 
-// IncreaseAccountBalance increases the balance of the account with the given ID
+// CreditAccount increases the balance of the account with the given ID
 // by the given amount.
 //
 // NOTE: This is part of the Store interface.
-func (s *BoltStore) IncreaseAccountBalance(_ context.Context, id AccountID,
+func (s *BoltStore) CreditAccount(_ context.Context, id AccountID,
 	amount lnwire.MilliSatoshi) error {
 
 	update := func(account *OffChainBalanceAccount) error {
@@ -244,6 +244,33 @@ func (s *BoltStore) IncreaseAccountBalance(_ context.Context, id AccountID,
 	return s.updateAccount(id, update)
 }
 
+// DebitAccount decreases the balance of the account with the given ID
+// by the given amount.
+//
+// NOTE: This is part of the Store interface.
+func (s *BoltStore) DebitAccount(_ context.Context, id AccountID,
+	amount lnwire.MilliSatoshi) error {
+
+	if amount > math.MaxInt64 {
+		return fmt.Errorf("amount %v exceeds the maximum of %v",
+			amount, int64(math.MaxInt64))
+	}
+
+	update := func(account *OffChainBalanceAccount) error {
+		if account.CurrentBalance-int64(amount) < 0 {
+			return fmt.Errorf("cannot debit %v from the account "+
+				"balance, as the resulting balance would be "+
+				"below 0", int64(amount/1000))
+		}
+
+		account.CurrentBalance -= int64(amount)
+
+		return nil
+	}
+
+	return s.updateAccount(id, update)
+}
+
 // UpsertAccountPayment updates or inserts a payment entry for the given
 // account. Various functional options can be passed to modify the behavior of
 // the method. The returned boolean is true if the payment was already known

accounts/store_test.go

@@ -2,6 +2,7 @@ package accounts
 
 import (
 	"context"
+	"github.com/lightningnetwork/lnd/lnwire"
 	"testing"
 	"time"
 
@@ -71,6 +72,14 @@ func TestAccountStore(t *testing.T) {
 	)
 	require.NoError(t, err)
 
+	// Adjust the account balance by first crediting 10000, and then
+	// debiting 5000.
+	err = store.CreditAccount(ctx, acct1.ID, lnwire.MilliSatoshi(10000))
+	require.NoError(t, err)
+
+	err = store.DebitAccount(ctx, acct1.ID, lnwire.MilliSatoshi(5000))
+	require.NoError(t, err)
+
 	// Update the in-memory account so that we can compare it with the
 	// account we get from the store.
 	acct1.CurrentBalance = -500
@@ -85,11 +94,30 @@ func TestAccountStore(t *testing.T) {
 	}
 	acct1.Invoices[lntypes.Hash{12, 34, 56, 78}] = struct{}{}
 	acct1.Invoices[lntypes.Hash{34, 56, 78, 90}] = struct{}{}
+	acct1.CurrentBalance += 10000
+	acct1.CurrentBalance -= 5000
 
 	dbAccount, err = store.Account(ctx, acct1.ID)
 	require.NoError(t, err)
 	assertEqualAccounts(t, acct1, dbAccount)
 
+	// Test that adjusting the balance to exactly 0 should work, while
+	// adjusting the balance to below 0 should fail.
+	err = store.DebitAccount(
+		ctx, acct1.ID, lnwire.MilliSatoshi(acct1.CurrentBalance),
+	)
+	require.NoError(t, err)
+
+	acct1.CurrentBalance = 0
+
+	dbAccount, err = store.Account(ctx, acct1.ID)
+	require.NoError(t, err)
+	assertEqualAccounts(t, acct1, dbAccount)
+
+	// Adjusting the value to below 0 should fail.
+	err = store.DebitAccount(ctx, acct1.ID, lnwire.MilliSatoshi(1))
+	require.ErrorContains(t, err, "balance would be below 0")
+
 	// Sleep just a tiny bit to make sure we are never too quick to measure
 	// the expiry, even though the time is nanosecond scale and writing to
 	// the store and reading again should take at least a couple of
@@ -262,12 +290,12 @@ func TestAccountUpdateMethods(t *testing.T) {
 		assertInvoices(hash1, hash2)
 	})
 
-	t.Run("IncreaseAccountBalance", func(t *testing.T) {
+	t.Run("CreditAccount", func(t *testing.T) {
 		store := NewTestDB(t, clock.NewTestClock(time.Now()))
 
 		// Increasing the balance of an account that doesn't exist
 		// should error out.
-		err := store.IncreaseAccountBalance(ctx, AccountID{}, 100)
+		err := store.CreditAccount(ctx, AccountID{}, 100)
 		require.ErrorIs(t, err, ErrAccNotFound)
 
 		acct, err := store.NewAccount(ctx, 123, time.Time{}, "foo")
@@ -284,7 +312,7 @@ func TestAccountUpdateMethods(t *testing.T) {
 
 		// Increase the balance by 100 and assert that the new balance
 		// is 223.
-		err = store.IncreaseAccountBalance(ctx, acct.ID, 100)
+		err = store.CreditAccount(ctx, acct.ID, 100)
 		require.NoError(t, err)
 
 		assertBalance(223)