grpc: add eth_call query command (#236)

* add eth_call query command

Implement EthCall grpc query api

Closes #229

add eth_call query command

fix codec issue

use query client

use grpc status error and codes

validate address length in grpc handler

* Update x/evm/types/callargs.go

Co-authored-by: Federico Kunze Küllmer <31522760+fedekunze@users.noreply.github.com>

x/evm/keeper/grpc_query.go

@@ -2,6 +2,7 @@ package keeper
 
 import (
 	"context"
+	"encoding/json"
 
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/status"
@@ -364,3 +365,34 @@ func (k Keeper) StaticCall(c context.Context, req *types.QueryStaticCallRequest)
 
 	return nil, nil
 }
+
+// EthCall implements eth_call rpc api.
+func (k Keeper) EthCall(c context.Context, req *types.EthCallRequest) (*types.MsgEthereumTxResponse, error) {
+	ctx := sdk.UnwrapSDKContext(c)
+	k.WithContext(ctx)
+
+	var args types.CallArgs
+	err := json.Unmarshal(req.Args, &args)
+	if err != nil {
+		return nil, status.Error(codes.InvalidArgument, err.Error())
+	}
+
+	msg := args.ToMessage(uint64(ethermint.DefaultRPCGasLimit))
+
+	cfg, found := k.GetChainConfig(ctx)
+	if !found {
+		return nil, status.Error(codes.Internal, types.ErrChainConfigNotFound.Error())
+	}
+	ethCfg := cfg.EthereumConfig(k.eip155ChainID)
+	evm := k.NewEVM(msg, ethCfg)
+	res, err := k.ApplyMessage(evm, msg, ethCfg)
+	if err != nil {
+		return nil, status.Error(codes.Internal, err.Error())
+	}
+
+	// ApplyMessage don't handle gas refund, let's do it here
+	refund := k.GasToRefund(res.GasUsed)
+	res.GasUsed -= refund
+
+	return res, nil
+}

x/evm/keeper/state_transition.go

@@ -258,6 +258,17 @@ func (k *Keeper) GetEthIntrinsicGas(msg core.Message, cfg *params.ChainConfig, i
 	return core.IntrinsicGas(msg.Data(), msg.AccessList(), isContractCreation, homestead, istanbul)
 }
 
+// GasToRefund calculate the amount of gas should refund to sender
+func (k *Keeper) GasToRefund(gasConsumed uint64) uint64 {
+	// Apply refund counter, capped to half of the used gas.
+	refund := gasConsumed / 2
+	availableRefund := k.GetRefund()
+	if refund > availableRefund {
+		return availableRefund
+	}
+	return refund
+}
+
 // RefundGas transfers the leftover gas to the sender of the message, caped to half of the total gas
 // consumed in the transaction. Additionally, the function sets the total gas consumed to the value
 // returned by the EVM execution, thus ignoring the previous intrinsic gas consumed during in the
@@ -271,13 +282,7 @@ func (k *Keeper) RefundGas(msg core.Message, leftoverGas uint64) (uint64, error)
 	}
 
 	gasConsumed := msg.Gas() - leftoverGas
-
-	// Apply refund counter, capped to half of the used gas.
-	refund := gasConsumed / 2
-	availableRefund := k.GetRefund()
-	if refund > availableRefund {
-		refund = availableRefund
-	}
+	refund := k.GasToRefund(gasConsumed)
 
 	leftoverGas += refund