From 545133f9dad92afa409aa67ea39b40af8d3695ac Mon Sep 17 00:00:00 2001
From: Xiaoyu Chen <codchen03@gmail.com>
Date: Wed, 15 Jun 2022 16:29:43 -0700
Subject: [PATCH] Gasless transaction fixes

---
 app/ante.go   |  5 +++-
 x/dex/ante.go | 77 +++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 81 insertions(+), 1 deletion(-)
 create mode 100644 x/dex/ante.go

diff --git a/app/ante.go b/app/ante.go
index ffe6ec4807..974665b12e 100644
--- a/app/ante.go
+++ b/app/ante.go
@@ -8,6 +8,7 @@ import (
 	"github.com/cosmos/cosmos-sdk/x/auth/ante"
 	ibcante "github.com/cosmos/ibc-go/v3/modules/core/ante"
 	ibckeeper "github.com/cosmos/ibc-go/v3/modules/core/keeper"
+	"github.com/sei-protocol/sei-chain/x/dex"
 	"github.com/sei-protocol/sei-chain/x/oracle"
 	oraclekeeper "github.com/sei-protocol/sei-chain/x/oracle/keeper"
 )
@@ -48,13 +49,15 @@ func NewAnteHandler(options HandlerOptions) (sdk.AnteHandler, error) {
 		sigGasConsumer = ante.DefaultSigVerificationGasConsumer
 	}
 
+	memPoolDecorator := ante.NewMempoolFeeDecorator()
 	anteDecorators := []sdk.AnteDecorator{
 		ante.NewSetUpContextDecorator(), // outermost AnteDecorator. SetUpContext must be called first
+		dex.NewGaslessDecorator(),
 		wasmkeeper.NewLimitSimulationGasDecorator(options.WasmConfig.SimulationGasLimit), // after setup context to enforce limits early
 		wasmkeeper.NewCountTXDecorator(options.TXCounterStoreKey),
 		ante.NewRejectExtensionOptionsDecorator(),
 		oracle.NewSpammingPreventionDecorator(*options.OracleKeeper),
-		ante.NewMempoolFeeDecorator(),
+		dex.NewGaslessDecoratorWrapper(&memPoolDecorator),
 		ante.NewValidateBasicDecorator(),
 		ante.NewTxTimeoutHeightDecorator(),
 		ante.NewValidateMemoDecorator(options.AccountKeeper),
diff --git a/x/dex/ante.go b/x/dex/ante.go
new file mode 100644
index 0000000000..17c2ade8e0
--- /dev/null
+++ b/x/dex/ante.go
@@ -0,0 +1,77 @@
+package dex
+
+import (
+	"bytes"
+
+	sdk "github.com/cosmos/cosmos-sdk/types"
+	"github.com/sei-protocol/sei-chain/x/dex/types"
+)
+
+// TODO: migrate this into params state
+var WHITELISTED_GASLESS_CANCELLATION_ADDRS = []sdk.AccAddress{}
+
+type GaslessDecoratorWrapper struct {
+	wrapped sdk.AnteDecorator
+}
+
+func NewGaslessDecoratorWrapper(wrapped sdk.AnteDecorator) GaslessDecoratorWrapper {
+	return GaslessDecoratorWrapper{wrapped: wrapped}
+}
+
+func (gd GaslessDecoratorWrapper) AnteHandle(ctx sdk.Context, tx sdk.Tx, simulate bool, next sdk.AnteHandler) (newCtx sdk.Context, err error) {
+	if !isTxGasless(tx) {
+		return gd.wrapped.AnteHandle(ctx, tx, simulate, next)
+	}
+
+	// skip the wrapped if gasless
+	return next(ctx, tx, simulate)
+}
+
+type GaslessDecorator struct{}
+
+func NewGaslessDecorator() GaslessDecorator {
+	return GaslessDecorator{}
+}
+
+func (gd GaslessDecorator) AnteHandle(ctx sdk.Context, tx sdk.Tx, simulate bool, next sdk.AnteHandler) (newCtx sdk.Context, err error) {
+	if !isTxGasless(tx) {
+		return next(ctx, tx, simulate)
+	}
+	gaslessMeter := sdk.NewInfiniteGasMeter()
+
+	return next(ctx.WithGasMeter(gaslessMeter), tx, simulate)
+}
+
+func isTxGasless(tx sdk.Tx) bool {
+	for _, msg := range tx.GetMsgs() {
+		switch msg.(type) {
+		case *types.MsgPlaceOrders:
+			continue
+		case *types.MsgCancelOrders:
+			if allSignersWhitelisted(msg) {
+				continue
+			} else {
+				return false
+			}
+		default:
+			return false
+		}
+	}
+	return true
+}
+
+func allSignersWhitelisted(msg sdk.Msg) bool {
+	for _, signer := range msg.GetSigners() {
+		isWhitelisted := false
+		for _, whitelisted := range WHITELISTED_GASLESS_CANCELLATION_ADDRS {
+			if bytes.Compare(signer, whitelisted) == 0 {
+				isWhitelisted = true
+				break
+			}
+		}
+		if !isWhitelisted {
+			return false
+		}
+	}
+	return true
+}