// Copyright 2017 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package vm

import (
	"errors"

	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/common/math"
	"github.com/ethereum/go-ethereum/core/tracing"
	"github.com/ethereum/go-ethereum/params"
)

// memoryGasCost calculates the quadratic gas for memory expansion. It does so
// only for the memory region that is expanded, not the total memory.
func memoryGasCost(mem *Memory, newMemSize uint64) (uint64, error) {
	if newMemSize == 0 {
		return 0, nil
	}
	// The maximum that will fit in a uint64 is max_word_count - 1. Anything above
	// that will result in an overflow. Additionally, a newMemSize which results in
	// a newMemSizeWords larger than 0xFFFFFFFF will cause the square operation to
	// overflow. The constant 0x1FFFFFFFE0 is the highest number that can be used
	// without overflowing the gas calculation.
	if newMemSize > 0x1FFFFFFFE0 {
		return 0, ErrGasUintOverflow
	}
	newMemSizeWords := toWordSize(newMemSize)
	newMemSize = newMemSizeWords * 32

	if newMemSize > uint64(mem.Len()) {
		square := newMemSizeWords * newMemSizeWords
		linCoef := newMemSizeWords * params.MemoryGas
		quadCoef := square / params.QuadCoeffDiv
		newTotalFee := linCoef + quadCoef

		fee := newTotalFee - mem.lastGasCost
		mem.lastGasCost = newTotalFee

		return fee, nil
	}
	return 0, nil
}

// memoryCopierGas creates the gas functions for the following opcodes, and takes
// the stack position of the operand which determines the size of the data to copy
// as argument:
// CALLDATACOPY (stack position 2)
// CODECOPY (stack position 2)
// MCOPY (stack position 2)
// EXTCODECOPY (stack position 3)
// RETURNDATACOPY (stack position 2)
func memoryCopierGas(stackpos int) gasFunc {
	return func(evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (GasCosts, error) {
		// Gas for expanding the memory
		gas, err := memoryGasCost(mem, memorySize)
		if err != nil {
			return GasCosts{}, err
		}
		// And gas for copying data, charged per word at param.CopyGas
		words, overflow := stack.back(stackpos).Uint64WithOverflow()
		if overflow {
			return GasCosts{}, ErrGasUintOverflow
		}

		if words, overflow = math.SafeMul(toWordSize(words), params.CopyGas); overflow {
			return GasCosts{}, ErrGasUintOverflow
		}

		if gas, overflow = math.SafeAdd(gas, words); overflow {
			return GasCosts{}, ErrGasUintOverflow
		}
		return GasCosts{RegularGas: gas}, nil
	}
}

var (
	gasCallDataCopy   = memoryCopierGas(2)
	gasCodeCopy       = memoryCopierGas(2)
	gasMcopy          = memoryCopierGas(2)
	gasExtCodeCopy    = memoryCopierGas(3)
	gasReturnDataCopy = memoryCopierGas(2)
)

func gasSStore(evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (GasCosts, error) {
	if evm.readOnly {
		return GasCosts{}, ErrWriteProtection
	}
	var (
		y, x              = stack.back(1), stack.back(0)
		current, original = evm.StateDB.GetStateAndCommittedState(contract.Address(), x.Bytes32())
	)
	// The legacy gas metering only takes into consideration the current state
	// Legacy rules should be applied if we are in Petersburg (removal of EIP-1283)
	// OR Constantinople is not active
	if evm.chainRules.IsPetersburg || !evm.chainRules.IsConstantinople {
		// This checks for 3 scenarios and calculates gas accordingly:
		//
		// 1. From a zero-value address to a non-zero value         (NEW VALUE)
		// 2. From a non-zero value address to a zero-value address (DELETE)
		// 3. From a non-zero to a non-zero                         (CHANGE)
		switch {
		case current == (common.Hash{}) && y.Sign() != 0: // 0 => non 0
			return GasCosts{RegularGas: params.SstoreSetGas}, nil
		case current != (common.Hash{}) && y.Sign() == 0: // non 0 => 0
			evm.StateDB.AddRefund(params.SstoreRefundGas)
			return GasCosts{RegularGas: params.SstoreClearGas}, nil
		default: // non 0 => non 0 (or 0 => 0)
			return GasCosts{RegularGas: params.SstoreResetGas}, nil
		}
	}

	// The new gas metering is based on net gas costs (EIP-1283):
	//
	// (1.) If current value equals new value (this is a no-op), 200 gas is deducted.
	// (2.) If current value does not equal new value
	//	(2.1.) If original value equals current value (this storage slot has not been changed by the current execution context)
	//		(2.1.1.) If original value is 0, 20000 gas is deducted.
	//		(2.1.2.) Otherwise, 5000 gas is deducted. If new value is 0, add 15000 gas to refund counter.
	//	(2.2.) If original value does not equal current value (this storage slot is dirty), 200 gas is deducted. Apply both of the following clauses.
	//		(2.2.1.) If original value is not 0
	//			(2.2.1.1.) If current value is 0 (also means that new value is not 0), remove 15000 gas from refund counter. We can prove that refund counter will never go below 0.
	//			(2.2.1.2.) If new value is 0 (also means that current value is not 0), add 15000 gas to refund counter.
	//		(2.2.2.) If original value equals new value (this storage slot is reset)
	//			(2.2.2.1.) If original value is 0, add 19800 gas to refund counter.
	//			(2.2.2.2.) Otherwise, add 4800 gas to refund counter.
	value := common.Hash(y.Bytes32())
	if current == value { // noop (1)
		return GasCosts{RegularGas: params.NetSstoreNoopGas}, nil
	}
	if original == current {
		if original == (common.Hash{}) { // create slot (2.1.1)
			return GasCosts{RegularGas: params.NetSstoreInitGas}, nil
		}
		if value == (common.Hash{}) { // delete slot (2.1.2b)
			evm.StateDB.AddRefund(params.NetSstoreClearRefund)
		}
		return GasCosts{RegularGas: params.NetSstoreCleanGas}, nil // write existing slot (2.1.2)
	}
	if original != (common.Hash{}) {
		if current == (common.Hash{}) { // recreate slot (2.2.1.1)
			evm.StateDB.SubRefund(params.NetSstoreClearRefund)
		} else if value == (common.Hash{}) { // delete slot (2.2.1.2)
			evm.StateDB.AddRefund(params.NetSstoreClearRefund)
		}
	}
	if original == value {
		if original == (common.Hash{}) { // reset to original inexistent slot (2.2.2.1)
			evm.StateDB.AddRefund(params.NetSstoreResetClearRefund)
		} else { // reset to original existing slot (2.2.2.2)
			evm.StateDB.AddRefund(params.NetSstoreResetRefund)
		}
	}
	return GasCosts{RegularGas: params.NetSstoreDirtyGas}, nil
}

// Here come the EIP2200 rules:
//
//	(0.) If *gasleft* is less than or equal to 2300, fail the current call.
//	(1.) If current value equals new value (this is a no-op), SLOAD_GAS is deducted.
//	(2.) If current value does not equal new value:
//		(2.1.) If original value equals current value (this storage slot has not been changed by the current execution context):
//			(2.1.1.) If original value is 0, SSTORE_SET_GAS (20K) gas is deducted.
//			(2.1.2.) Otherwise, SSTORE_RESET_GAS gas is deducted. If new value is 0, add SSTORE_CLEARS_SCHEDULE to refund counter.
//		(2.2.) If original value does not equal current value (this storage slot is dirty), SLOAD_GAS gas is deducted. Apply both of the following clauses:
//			(2.2.1.) If original value is not 0:
//				(2.2.1.1.) If current value is 0 (also means that new value is not 0), subtract SSTORE_CLEARS_SCHEDULE gas from refund counter.
//				(2.2.1.2.) If new value is 0 (also means that current value is not 0), add SSTORE_CLEARS_SCHEDULE gas to refund counter.
//			(2.2.2.) If original value equals new value (this storage slot is reset):
//				(2.2.2.1.) If original value is 0, add SSTORE_SET_GAS - SLOAD_GAS to refund counter.
//				(2.2.2.2.) Otherwise, add SSTORE_RESET_GAS - SLOAD_GAS gas to refund counter.
func gasSStoreEIP2200(evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (GasCosts, error) {
	if evm.readOnly {
		return GasCosts{}, ErrWriteProtection
	}
	// If we fail the minimum gas availability invariant, fail (0)
	if contract.Gas.RegularGas <= params.SstoreSentryGasEIP2200 {
		return GasCosts{}, errors.New("not enough gas for reentrancy sentry")
	}
	// Gas sentry honoured, do the actual gas calculation based on the stored value
	var (
		y, x              = stack.back(1), stack.back(0)
		current, original = evm.StateDB.GetStateAndCommittedState(contract.Address(), x.Bytes32())
	)
	value := common.Hash(y.Bytes32())

	if current == value { // noop (1)
		return GasCosts{RegularGas: params.SloadGasEIP2200}, nil
	}
	if original == current {
		if original == (common.Hash{}) { // create slot (2.1.1)
			return GasCosts{RegularGas: params.SstoreSetGasEIP2200}, nil
		}
		if value == (common.Hash{}) { // delete slot (2.1.2b)
			evm.StateDB.AddRefund(params.SstoreClearsScheduleRefundEIP2200)
		}
		return GasCosts{RegularGas: params.SstoreResetGasEIP2200}, nil // write existing slot (2.1.2)
	}
	if original != (common.Hash{}) {
		if current == (common.Hash{}) { // recreate slot (2.2.1.1)
			evm.StateDB.SubRefund(params.SstoreClearsScheduleRefundEIP2200)
		} else if value == (common.Hash{}) { // delete slot (2.2.1.2)
			evm.StateDB.AddRefund(params.SstoreClearsScheduleRefundEIP2200)
		}
	}
	if original == value {
		if original == (common.Hash{}) { // reset to original inexistent slot (2.2.2.1)
			evm.StateDB.AddRefund(params.SstoreSetGasEIP2200 - params.SloadGasEIP2200)
		} else { // reset to original existing slot (2.2.2.2)
			evm.StateDB.AddRefund(params.SstoreResetGasEIP2200 - params.SloadGasEIP2200)
		}
	}
	return GasCosts{RegularGas: params.SloadGasEIP2200}, nil // dirty update (2.2)
}

func makeGasLog(n uint64) gasFunc {
	return func(evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (GasCosts, error) {
		requestedSize, overflow := stack.back(1).Uint64WithOverflow()
		if overflow {
			return GasCosts{}, ErrGasUintOverflow
		}

		gas, err := memoryGasCost(mem, memorySize)
		if err != nil {
			return GasCosts{}, err
		}

		if gas, overflow = math.SafeAdd(gas, params.LogGas); overflow {
			return GasCosts{}, ErrGasUintOverflow
		}
		if gas, overflow = math.SafeAdd(gas, n*params.LogTopicGas); overflow {
			return GasCosts{}, ErrGasUintOverflow
		}

		var memorySizeGas uint64
		if memorySizeGas, overflow = math.SafeMul(requestedSize, params.LogDataGas); overflow {
			return GasCosts{}, ErrGasUintOverflow
		}
		if gas, overflow = math.SafeAdd(gas, memorySizeGas); overflow {
			return GasCosts{}, ErrGasUintOverflow
		}
		return GasCosts{RegularGas: gas}, nil
	}
}

func gasKeccak256(evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (GasCosts, error) {
	gas, err := memoryGasCost(mem, memorySize)
	if err != nil {
		return GasCosts{}, err
	}
	wordGas, overflow := stack.back(1).Uint64WithOverflow()
	if overflow {
		return GasCosts{}, ErrGasUintOverflow
	}
	if wordGas, overflow = math.SafeMul(toWordSize(wordGas), params.Keccak256WordGas); overflow {
		return GasCosts{}, ErrGasUintOverflow
	}
	if gas, overflow = math.SafeAdd(gas, wordGas); overflow {
		return GasCosts{}, ErrGasUintOverflow
	}
	return GasCosts{RegularGas: gas}, nil
}

// pureMemoryGascost is used by several operations, which aside from their
// static cost have a dynamic cost which is solely based on the memory
// expansion
func pureMemoryGascost(evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (GasCosts, error) {
	gas, err := memoryGasCost(mem, memorySize)
	if err != nil {
		return GasCosts{}, err
	}
	return GasCosts{RegularGas: gas}, nil
}

var (
	gasReturn  = pureMemoryGascost
	gasRevert  = pureMemoryGascost
	gasMLoad   = pureMemoryGascost
	gasMStore8 = pureMemoryGascost
	gasMStore  = pureMemoryGascost
)

func gasCreate(evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (GasCosts, error) {
	if evm.readOnly {
		return GasCosts{}, ErrWriteProtection
	}
	return pureMemoryGascost(evm, contract, stack, mem, memorySize)
}

func gasCreate2(evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (GasCosts, error) {
	if evm.readOnly {
		return GasCosts{}, ErrWriteProtection
	}
	gas, err := memoryGasCost(mem, memorySize)
	if err != nil {
		return GasCosts{}, err
	}
	wordGas, overflow := stack.back(2).Uint64WithOverflow()
	if overflow {
		return GasCosts{}, ErrGasUintOverflow
	}
	if wordGas, overflow = math.SafeMul(toWordSize(wordGas), params.Keccak256WordGas); overflow {
		return GasCosts{}, ErrGasUintOverflow
	}
	if gas, overflow = math.SafeAdd(gas, wordGas); overflow {
		return GasCosts{}, ErrGasUintOverflow
	}
	return GasCosts{RegularGas: gas}, nil
}

func gasCreateEip3860(evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (GasCosts, error) {
	if evm.readOnly {
		return GasCosts{}, ErrWriteProtection
	}
	gas, err := memoryGasCost(mem, memorySize)
	if err != nil {
		return GasCosts{}, err
	}
	size, overflow := stack.back(2).Uint64WithOverflow()
	if overflow {
		return GasCosts{}, ErrGasUintOverflow
	}
	if err := CheckMaxInitCodeSize(&evm.chainRules, size); err != nil {
		return GasCosts{}, err
	}
	// Since size <= the protocol-defined maximum initcode size limit, these multiplication cannot overflow
	moreGas := params.InitCodeWordGas * ((size + 31) / 32)
	if gas, overflow = math.SafeAdd(gas, moreGas); overflow {
		return GasCosts{}, ErrGasUintOverflow
	}
	return GasCosts{RegularGas: gas}, nil
}

func gasCreate2Eip3860(evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (GasCosts, error) {
	if evm.readOnly {
		return GasCosts{}, ErrWriteProtection
	}
	gas, err := memoryGasCost(mem, memorySize)
	if err != nil {
		return GasCosts{}, err
	}
	size, overflow := stack.back(2).Uint64WithOverflow()
	if overflow {
		return GasCosts{}, ErrGasUintOverflow
	}
	if err := CheckMaxInitCodeSize(&evm.chainRules, size); err != nil {
		return GasCosts{}, err
	}
	// Since size <= the protocol-defined maximum initcode size limit, these multiplication cannot overflow
	moreGas := (params.InitCodeWordGas + params.Keccak256WordGas) * ((size + 31) / 32)
	if gas, overflow = math.SafeAdd(gas, moreGas); overflow {
		return GasCosts{}, ErrGasUintOverflow
	}
	return GasCosts{RegularGas: gas}, nil
}

// gasCreateEip8037 is the CREATE gas calculator for Amsterdam. It charges the
// account-creation cost as state gas (EIP-8037) here, before the opcode runs,
// so the 63/64 gas-forwarding split sees the post-charge regular gas. The
// charge is refunded to the reservoir in opCreate on any failure path that
// does not create an account.
func gasCreateEip8037(evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (GasCosts, error) {
	if evm.readOnly {
		return GasCosts{}, ErrWriteProtection
	}
	gas, err := memoryGasCost(mem, memorySize)
	if err != nil {
		return GasCosts{}, err
	}
	size, overflow := stack.back(2).Uint64WithOverflow()
	if overflow {
		return GasCosts{}, ErrGasUintOverflow
	}
	if err := CheckMaxInitCodeSize(&evm.chainRules, size); err != nil {
		return GasCosts{}, err
	}
	// Since size <= MaxInitCodeSizeAmsterdam, these multiplications cannot overflow.
	wordGas := params.InitCodeWordGas * ((size + 31) / 32)
	stateGas := params.AccountCreationSize * evm.Context.CostPerStateByte
	return GasCosts{
		RegularGas: gas + wordGas,
		StateGas:   stateGas,
	}, nil
}

// gasCreate2Eip8037 is the CREATE2 gas calculator for Amsterdam. See
// gasCreateEip8037; CREATE2 additionally charges Keccak256WordGas for hashing
// the init code.
func gasCreate2Eip8037(evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (GasCosts, error) {
	if evm.readOnly {
		return GasCosts{}, ErrWriteProtection
	}
	gas, err := memoryGasCost(mem, memorySize)
	if err != nil {
		return GasCosts{}, err
	}
	size, overflow := stack.back(2).Uint64WithOverflow()
	if overflow {
		return GasCosts{}, ErrGasUintOverflow
	}
	if err := CheckMaxInitCodeSize(&evm.chainRules, size); err != nil {
		return GasCosts{}, err
	}
	// Since size <= MaxInitCodeSizeAmsterdam, these multiplications cannot overflow.
	wordGas := (params.InitCodeWordGas + params.Keccak256WordGas) * ((size + 31) / 32)
	stateGas := params.AccountCreationSize * evm.Context.CostPerStateByte
	return GasCosts{
		RegularGas: gas + wordGas,
		StateGas:   stateGas,
	}, nil
}

func gasExpFrontier(evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (GasCosts, error) {
	expByteLen := uint64((stack.back(1).BitLen() + 7) / 8)

	var (
		gas      = expByteLen * params.ExpByteFrontier // no overflow check required. Max is 256 * ExpByte gas
		overflow bool
	)
	if gas, overflow = math.SafeAdd(gas, params.ExpGas); overflow {
		return GasCosts{}, ErrGasUintOverflow
	}
	return GasCosts{RegularGas: gas}, nil
}

func gasExpEIP158(evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (GasCosts, error) {
	expByteLen := uint64((stack.back(1).BitLen() + 7) / 8)

	var (
		gas      = expByteLen * params.ExpByteEIP158 // no overflow check required. Max is 256 * ExpByte gas
		overflow bool
	)
	if gas, overflow = math.SafeAdd(gas, params.ExpGas); overflow {
		return GasCosts{}, ErrGasUintOverflow
	}
	return GasCosts{RegularGas: gas}, nil
}

var (
	gasCall         = makeCallVariantGasCost(gasCallIntrinsic)
	gasCallCode     = makeCallVariantGasCost(gasCallCodeIntrinsic)
	gasDelegateCall = makeCallVariantGasCost(gasDelegateCallIntrinsic)
	gasStaticCall   = makeCallVariantGasCost(gasStaticCallIntrinsic)
)

func makeCallVariantGasCost(intrinsicFunc intrinsicGasFunc) gasFunc {
	return func(evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (GasCosts, error) {
		intrinsic, err := intrinsicFunc(evm, contract, stack, mem, memorySize)
		if err != nil {
			return GasCosts{}, err
		}
		evm.callGasTemp, err = callGas(evm.chainRules.IsEIP150, contract.Gas.RegularGas, intrinsic, stack.back(0))
		if err != nil {
			return GasCosts{}, err
		}
		gas, overflow := math.SafeAdd(intrinsic, evm.callGasTemp)
		if overflow {
			return GasCosts{}, ErrGasUintOverflow
		}
		return GasCosts{RegularGas: gas}, nil
	}
}

func gasCallIntrinsic(evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
	var (
		gas            uint64
		transfersValue = !stack.back(2).IsZero()
		address        = common.Address(stack.back(1).Bytes20())
	)
	if evm.readOnly && transfersValue {
		return 0, ErrWriteProtection
	}
	// Stateless check
	memoryGas, err := memoryGasCost(mem, memorySize)
	if err != nil {
		return 0, err
	}
	var transferGas uint64
	if transfersValue && !evm.chainRules.IsEIP4762 {
		transferGas = params.CallValueTransferGas
		if evm.chainRules.IsAmsterdam {
			// EIP-8038: CALL_VALUE = ACCOUNT_WRITE + CALL_STIPEND.
			transferGas = params.CallValueTransferAmsterdam
		}
	}
	var overflow bool
	if gas, overflow = math.SafeAdd(memoryGas, transferGas); overflow {
		return 0, ErrGasUintOverflow
	}
	// Terminate the gas measurement if the leftover gas is not sufficient,
	// it can effectively prevent accessing the states in the following steps.
	if contract.Gas.RegularGas < gas {
		return 0, ErrOutOfGas
	}
	// Stateful check
	if evm.chainRules.IsAmsterdam {
		// EIP-8037: the cost of creating a new account via a value-bearing
		// CALL is metered as state gas (NEW_ACCOUNT * CostPerStateByte),
		// not the legacy regular CallNewAccountGas. It drains the state
		// reservoir, spilling into regular gas only when the reservoir is
		// exhausted, mirroring the spec's inline charge_state_gas in
		// system.call.
		evm.callNewAccountChargedTemp = false
		if transfersValue && evm.StateDB.Empty(address) {
			stateGas := params.AccountCreationSize * evm.Context.CostPerStateByte
			regularAfterCall := contract.Gas.RegularGas - gas
			if stateGas > contract.Gas.StateGas && stateGas-contract.Gas.StateGas > regularAfterCall {
				return 0, ErrOutOfGas
			}
			if !contract.chargeState(stateGas, evm.Config.Tracer, tracing.GasChangeAccountCreation) {
				return 0, ErrOutOfGas
			}
			evm.callNewAccountChargedTemp = true
		}
		return gas, nil
	}
	var stateGas uint64
	if evm.chainRules.IsEIP158 {
		if transfersValue && evm.StateDB.Empty(address) {
			stateGas += params.CallNewAccountGas
		}
	} else if !evm.StateDB.Exist(address) {
		stateGas += params.CallNewAccountGas
	}
	if gas, overflow = math.SafeAdd(gas, stateGas); overflow {
		return 0, ErrGasUintOverflow
	}
	return gas, nil
}

func gasCallCodeIntrinsic(evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
	memoryGas, err := memoryGasCost(mem, memorySize)
	if err != nil {
		return 0, err
	}
	var (
		gas      uint64
		overflow bool
	)
	if stack.back(2).Sign() != 0 && !evm.chainRules.IsEIP4762 {
		transferGas := params.CallValueTransferGas
		if evm.chainRules.IsAmsterdam {
			// EIP-8038: CALL_VALUE = ACCOUNT_WRITE + CALL_STIPEND.
			transferGas = params.CallValueTransferAmsterdam
		}
		gas += transferGas
	}
	if gas, overflow = math.SafeAdd(gas, memoryGas); overflow {
		return 0, ErrGasUintOverflow
	}
	return gas, nil
}

func gasDelegateCallIntrinsic(evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
	gas, err := memoryGasCost(mem, memorySize)
	if err != nil {
		return 0, err
	}
	return gas, nil
}

func gasStaticCallIntrinsic(evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
	gas, err := memoryGasCost(mem, memorySize)
	if err != nil {
		return 0, err
	}
	return gas, nil
}

func gasSelfdestruct(evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (GasCosts, error) {
	if evm.readOnly {
		return GasCosts{}, ErrWriteProtection
	}
	var gas uint64
	// EIP150 homestead gas reprice fork:
	if evm.chainRules.IsEIP150 {
		gas = params.SelfdestructGasEIP150
		var address = common.Address(stack.back(0).Bytes20())
		if evm.chainRules.IsEIP158 {
			// if empty and transfers value
			if evm.StateDB.Empty(address) && evm.StateDB.GetBalance(contract.Address()).Sign() != 0 {
				gas += params.CreateBySelfdestructGas
			}
		} else if !evm.StateDB.Exist(address) {
			gas += params.CreateBySelfdestructGas
		}
	}

	if !evm.StateDB.HasSelfDestructed(contract.Address()) {
		evm.StateDB.AddRefund(params.SelfdestructRefundGas)
	}
	return GasCosts{RegularGas: gas}, nil
}

func gasSelfdestruct8037(evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (GasCosts, error) {
	if evm.readOnly {
		return GasCosts{}, ErrWriteProtection
	}
	var (
		gas     GasCosts
		address = common.Address(stack.peek().Bytes20())
	)
	if !evm.StateDB.AddressInAccessList(address) {
		// If the caller cannot afford the cost, this change will be rolled back
		evm.StateDB.AddAddressToAccessList(address)
		gas.RegularGas = params.ColdAccountAccessAmsterdam
	}
	// Check we have enough regular gas before we add the address to the BAL
	if contract.Gas.RegularGas < gas.RegularGas {
		return gas, ErrOutOfGas
	}
	// Important: use StateDB.Empty instead of !StateDB.Exist. An account may exist
	// in the current state yet still be considered non-existent by EIP-161 if its
	// nonce, balance, and code are all zero. Such accounts can appear temporarily
	// during execution (e.g. via SELFDESTRUCT) and are removed at tx end.
	//
	// Funding such an account makes it permanent state growth and must be charged.
	if evm.StateDB.Empty(address) && evm.StateDB.GetBalance(contract.Address()).Sign() != 0 {
		gas.StateGas += params.AccountCreationSize * evm.Context.CostPerStateByte
		// EIP-8038: positive balance sent to an empty account also charges the
		// regular ACCOUNT_WRITE cost.
		gas.RegularGas += params.AccountWriteAmsterdam
	}
	return gas, nil
}

// gasSStore8037 is the SSTORE gas calculator for Amsterdam (EIP-8037 +
// EIP-8038). It mirrors amsterdam/vm/instructions/storage.py::sstore:
//
//   - a cold/warm access cost is always charged (regular);
//   - a STORAGE_WRITE cost is charged once, on the first change to the slot in
//     the transaction (regular);
//   - creating a slot from zero charges STORAGE_SET state gas, refunded to the
//     reservoir if the slot is later restored to zero in the same tx;
//   - clearing an originally non-zero slot credits/reverses REFUND_STORAGE_CLEAR
//     and restoring a changed slot refunds the STORAGE_WRITE, both via the
//     (gas_used/5-capped) refund counter.
func gasSStore8037(evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (GasCosts, error) {
	if evm.readOnly {
		return GasCosts{}, ErrWriteProtection
	}
	// Stipend sentry: require strictly more than the call stipend (spec
	// check_gas(CALL_STIPEND + 1)).
	if contract.Gas.RegularGas <= params.CallStipend {
		return GasCosts{}, errors.New("not enough gas for reentrancy sentry")
	}
	var (
		y, x              = stack.back(1), stack.peek()
		slot              = common.Hash(x.Bytes32())
		current, original = evm.StateDB.GetStateAndCommittedState(contract.Address(), slot)
		newValue          = common.Hash(y.Bytes32())
		stateSetGas       = params.StorageCreationSize * evm.Context.CostPerStateByte
		cost              GasCosts
	)
	// Access cost: cold or warm, always charged.
	if _, slotPresent := evm.StateDB.SlotInAccessList(contract.Address(), slot); !slotPresent {
		// If the caller cannot afford the cost, this change will be rolled back.
		evm.StateDB.AddSlotToAccessList(contract.Address(), slot)
		cost.RegularGas += params.ColdStorageAccessAmsterdam
	} else {
		cost.RegularGas += params.WarmStorageReadCostEIP2929
	}
	// Write cost: charged on the first change to the slot this transaction.
	if original == current && current != newValue {
		cost.RegularGas += params.StorageWriteAmsterdam
	}
	// Refund counter (regular).
	if current != newValue {
		if original != (common.Hash{}) && current != (common.Hash{}) && newValue == (common.Hash{}) {
			// Storage cleared for the first time in the transaction.
			evm.StateDB.AddRefund(params.SstoreClearsRefundAmsterdam)
		}
		if original != (common.Hash{}) && current == (common.Hash{}) {
			// A refund issued earlier this tx is reversed.
			evm.StateDB.SubRefund(params.SstoreClearsRefundAmsterdam)
		}
		if original == newValue {
			// Slot restored to its original value: refund the STORAGE_WRITE
			// charged on the first-time change earlier this transaction.
			evm.StateDB.AddRefund(params.StorageWriteAmsterdam)
		}
	}
	// State gas (reservoir).
	if original == current && current != newValue && original == (common.Hash{}) {
		// Slot created from zero: charge STORAGE_SET state gas.
		cost.StateGas = stateSetGas
	}
	if current != newValue && original == newValue && original == (common.Hash{}) {
		// Slot set then cleared in the same tx: refund the state gas in LIFO
		// order (regular gas up to the spilled amount, then the reservoir),
		// not the gas_used/5-capped refund counter.
		contract.Gas.CreditStateRefund(stateSetGas)
	}
	return cost, nil
}