StatefulSwap now validates positive sell fee (#168)

Author: jeffyanta

ocp/rpc/transaction/server.go

@@ -13,6 +13,7 @@ import (
 	"github.com/code-payments/ocp-server/ocp/antispam"
 	auth_util "github.com/code-payments/ocp-server/ocp/auth"
 	"github.com/code-payments/ocp-server/ocp/common"
+	currency_util "github.com/code-payments/ocp-server/ocp/currency"
 	ocp_data "github.com/code-payments/ocp-server/ocp/data"
 	"github.com/code-payments/ocp-server/ocp/data/nonce"
 	"github.com/code-payments/ocp-server/ocp/transaction"
@@ -23,7 +24,8 @@ type transactionServer struct {
 
 	log *zap.Logger
 
-	data ocp_data.Provider
+	data             ocp_data.Provider
+	mintDataProvider *currency_util.MintDataProvider
 
 	auth *auth_util.RPCSignatureVerifier
 
@@ -46,6 +48,7 @@ type transactionServer struct {
 func NewTransactionServer(
 	log *zap.Logger,
 	data ocp_data.Provider,
+	mintDataProvider *currency_util.MintDataProvider,
 	submitIntentIntegration SubmitIntentIntegration,
 	antispamGuard *antispam.Guard,
 	amlGuard *aml.Guard,
@@ -86,7 +89,8 @@ func NewTransactionServer(
 
 		log: log,
 
-		data: data,
+		data:             data,
+		mintDataProvider: mintDataProvider,
 
 		auth: auth_util.NewRPCSignatureVerifier(log, data),
 

ocp/rpc/transaction/swap.go

@@ -28,6 +28,7 @@ import (
 	"github.com/code-payments/ocp-server/ocp/vm"
 	"github.com/code-payments/ocp-server/protoutil"
 	"github.com/code-payments/ocp-server/solana"
+	"github.com/code-payments/ocp-server/solana/currencycreator"
 )
 
 func (s *transactionServer) StatefulSwap(streamer transactionpb.Transaction_StatefulSwapServer) error {
@@ -233,6 +234,24 @@ func (s *transactionServer) StatefulSwap(streamer transactionpb.Transaction_Stat
 		return handleStatefulSwapError(streamer, NewSwapDeniedError("mint is being initialized"))
 	}
 
+	if !initializesMint && !common.IsCoreMint(fromMint) {
+		liveReserveState, err := s.mintDataProvider.GetLiveReserveState(ctx, fromMint)
+		if err != nil {
+			log.With(zap.Error(err)).Warn("failure getting live reserve state")
+			return handleStatefulSwapError(streamer, err)
+		}
+
+		_, estimatedFees := currencycreator.EstimateSell(&currencycreator.EstimateSellArgs{
+			CurrentSupplyInQuarks: liveReserveState.SupplyFromBonding,
+			SellAmountInQuarks:    initiateReserveSwapReq.Amount,
+			ValueMintDecimals:     uint8(common.CoreMintDecimals),
+			SellFeeBps:            currencyMetadataRecord.SellFeeBps,
+		})
+		if estimatedFees == 0 {
+			return handleStatefulSwapError(streamer, NewSwapDeniedError("swap would not generate a sell fee"))
+		}
+	}
+
 	var destinationVmAuthority *common.Account
 	if !initializesMint {
 		if owner.PublicKey().ToBase58() == swapAuthority.PublicKey().ToBase58() {