feat(werc20): precompile setup (evmos#1977)

* feat(werc20): precompile setup

* fixes

* comments

* Apply suggestions from code review

Co-authored-by: stepit <48993133+0xstepit@users.noreply.github.com>

---------

Co-authored-by: stepit <48993133+0xstepit@users.noreply.github.com>

Author: fedekunze

precompiles/common/types.go

@@ -14,6 +14,13 @@ import (
 	evmosutils "github.com/evmos/evmos/v15/utils"
 )
 
+const (
+	// FallbackMethod is the name of the fallback method.
+	FallbackMethod = "fallback"
+	// ReceiveMethod is the name of the receive method.
+	ReceiveMethod = "receive"
+)
+
 var (
 	// TrueValue is the byte array representing a true value in solidity.
 	TrueValue = []byte{0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x1}

precompiles/werc20/tx.go

@@ -0,0 +1,13 @@
+// Copyright Tharsis Labs Ltd.(Evmos)
+// SPDX-License-Identifier:ENCL-1.0(https://github.com/evmos/evmos/blob/main/LICENSE)
+
+package werc20
+
+const (
+	// DepositMethod defines the ABI method name for the IWERC20 deposit
+	// transaction.
+	DepositMethod = "deposit"
+	// WithdrawMethod defines the ABI method name for the IWERC20 withdraw
+	// transaction.
+	WithdrawMethod = "withdraw"
+)

precompiles/werc20/werc20.go

@@ -0,0 +1,134 @@
+// Copyright Tharsis Labs Ltd.(Evmos)
+// SPDX-License-Identifier:ENCL-1.0(https://github.com/evmos/evmos/blob/main/LICENSE)
+
+package werc20
+
+import (
+	"embed"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/vm"
+
+	authzkeeper "github.com/cosmos/cosmos-sdk/x/authz/keeper"
+	bankkeeper "github.com/cosmos/cosmos-sdk/x/bank/keeper"
+	cmn "github.com/evmos/evmos/v15/precompiles/common"
+	erc20 "github.com/evmos/evmos/v15/precompiles/erc20"
+	erc20types "github.com/evmos/evmos/v15/x/erc20/types"
+	transferkeeper "github.com/evmos/evmos/v15/x/ibc/transfer/keeper"
+)
+
+// abiPath defines the path to the WERC-20 precompile ABI JSON file.
+const abiPath = "./abi.json"
+
+// Embed abi json file to the executable binary. Needed when importing as dependency.
+//
+//go:embed abi.json
+var f embed.FS
+
+var _ vm.PrecompiledContract = &Precompile{}
+
+// Precompile defines the precompiled contract for WERC20.
+type Precompile struct {
+	*erc20.Precompile
+}
+
+// NewPrecompile creates a new WERC20 Precompile instance as a
+// PrecompiledContract interface.
+func NewPrecompile(
+	tokenPair erc20types.TokenPair,
+	bankKeeper bankkeeper.Keeper,
+	authzKeeper authzkeeper.Keeper,
+	transferKeeper transferkeeper.Keeper,
+) (*Precompile, error) {
+	newABI, err := cmn.LoadABI(f, abiPath)
+	if err != nil {
+		return nil, err
+	}
+
+	erc20Precompile, err := erc20.NewPrecompile(tokenPair, bankKeeper, authzKeeper, transferKeeper)
+	if err != nil {
+		return nil, err
+	}
+
+	// use the IWERC20 ABI
+	erc20Precompile.Precompile.ABI = newABI
+
+	return &Precompile{
+		Precompile: erc20Precompile,
+	}, nil
+}
+
+// Address defines the address of the ERC20 precompile contract.
+func (p Precompile) Address() common.Address {
+	return p.Precompile.Address()
+}
+
+// RequiredGas calculates the contract gas use.
+func (p Precompile) RequiredGas(input []byte) uint64 {
+	methodID := input[:4]
+	method, err := p.MethodById(methodID)
+	if err != nil {
+		return 0
+	}
+
+	// TODO: these values were obtained from Remix using the WEVMOS9.sol.
+	// We should execute the transactions from Evmos testnet
+	// to ensure parity in the values.
+	switch method.Name {
+	case cmn.FallbackMethod, cmn.ReceiveMethod, DepositMethod:
+		return 28_799
+	case WithdrawMethod:
+		return 3_000_000
+	}
+
+	return p.Precompile.RequiredGas(input)
+}
+
+// Run executes the precompiled contract WERC20 methods defined in the ABI.
+func (p Precompile) Run(evm *vm.EVM, contract *vm.Contract, readOnly bool) (bz []byte, err error) {
+	ctx, stateDB, method, initialGas, args, err := p.Precompile.RunSetup(evm, contract, readOnly, p.IsTransaction)
+	if err != nil {
+		return nil, err
+	}
+
+	// This handles any out of gas errors that may occur during the execution of a precompile tx or query.
+	// It avoids panics and returns the out of gas error so the EVM can continue gracefully.
+	defer cmn.HandleGasError(ctx, contract, initialGas, &err)()
+
+	switch method.Name {
+	// WERC20 transactions
+	case cmn.FallbackMethod, cmn.ReceiveMethod, DepositMethod:
+		// bz, err = p.Deposit(ctx, contract, stateDB, method, args)
+	case WithdrawMethod:
+		// bz, err = p.Withdraw(ctx, contract, stateDB, method, args)
+
+	default:
+		// ERC20 transactions and queries
+		bz, err = p.Precompile.HandleMethod(ctx, contract, stateDB, method, args)
+	}
+
+	if err != nil {
+		return nil, err
+	}
+
+	cost := ctx.GasMeter().GasConsumed() - initialGas
+
+	if !contract.UseGas(cost) {
+		return nil, vm.ErrOutOfGas
+	}
+
+	return bz, nil
+}
+
+// IsTransaction checks if the given methodID corresponds to a transaction or query.
+func (p Precompile) IsTransaction(methodID string) bool {
+	switch methodID {
+	case cmn.FallbackMethod,
+		cmn.ReceiveMethod,
+		DepositMethod,
+		WithdrawMethod:
+		return true
+	default:
+		return p.Precompile.IsTransaction(methodID)
+	}
+}