env.rs

use crate::{
    alloc::vec::Vec, calc_blob_gasprice, Account, InvalidHeader, InvalidTransaction, Spec, SpecId,
    B160, B256, GAS_PER_BLOB, KECCAK_EMPTY, MAX_BLOB_NUMBER_PER_BLOCK, MAX_INITCODE_SIZE, U256,
    VERSIONED_HASH_VERSION_KZG,
};
use bytes::Bytes;
use core::cmp::{min, Ordering};

#[derive(Clone, Debug, Default, PartialEq, Eq, Hash)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct Env {
    pub cfg: CfgEnv,
    pub block: BlockEnv,
    pub tx: TxEnv,
}

/// The block environment.
#[derive(Clone, Debug, PartialEq, Eq, Hash)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct BlockEnv {
    /// The number of ancestor blocks of this block (block height).
    pub number: U256,
    /// Coinbase or miner or address that created and signed the block.
    ///
    /// This is the receiver address of all the gas spent in the block.
    pub coinbase: B160,
    /// The timestamp of the block in seconds since the UNIX epoch.
    pub timestamp: U256,
    /// The gas limit of the block.
    pub gas_limit: U256,
    /// The base fee per gas, added in the London upgrade with [EIP-1559].
    ///
    /// [EIP-1559]: https://eips.ethereum.org/EIPS/eip-1559
    pub basefee: U256,
    /// The difficulty of the block.
    ///
    /// Unused after the Paris (AKA the merge) upgrade, and replaced by `prevrandao`.
    pub difficulty: U256,
    /// The output of the randomness beacon provided by the beacon chain.
    ///
    /// Replaces `difficulty` after the Paris (AKA the merge) upgrade with [EIP-4399].
    ///
    /// NOTE: `prevrandao` can be found in a block in place of `mix_hash`.
    ///
    /// [EIP-4399]: https://eips.ethereum.org/EIPS/eip-4399
    pub prevrandao: Option<B256>,
    /// Excess blob gas and blob gasprice.
    /// See also [`calc_excess_blob_gas`](crate::calc_excess_blob_gas)
    /// and [`calc_blob_gasprice`](crate::calc_blob_gasprice).
    ///
    /// Incorporated as part of the Cancun upgrade via [EIP-4844].
    ///
    /// [EIP-4844]: https://eips.ethereum.org/EIPS/eip-4844
    pub blob_excess_gas_and_price: Option<BlobExcessGasAndPrice>,
}

/// Structure holding block blob excess gas and it calculates blob fee.
///
/// Incorporated as part of the Cancun upgrade via [EIP-4844].
///
/// [EIP-4844]: https://eips.ethereum.org/EIPS/eip-4844
#[derive(Clone, Debug, PartialEq, Eq, Hash)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct BlobExcessGasAndPrice {
    pub excess_blob_gas: u64,
    pub blob_gasprice: u64,
}

impl BlobExcessGasAndPrice {
    /// Takes excess blob gas and calculated blob fee with [`calc_blob_fee`]
    pub fn new(excess_blob_gas: u64) -> Self {
        let blob_gasprice = calc_blob_gasprice(excess_blob_gas);
        Self {
            excess_blob_gas,
            blob_gasprice,
        }
    }
}

#[cfg(feature = "optimism")]
#[derive(Clone, Debug, Default, PartialEq, Eq, Hash)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct OptimismFields {
    pub source_hash: Option<B256>,
    pub mint: Option<u128>,
    pub is_system_transaction: Option<bool>,
    /// An enveloped EIP-2718 typed transaction. This is used
    /// to compute the L1 tx cost using the L1 block info, as
    /// opposed to requiring downstream apps to compute the cost
    /// externally.
    /// This field is optional to allow the [TxEnv] to be constructed
    /// for non-optimism chains when the `optimism` feature is enabled,
    /// but the [CfgEnv] `optimism` field is set to false.
    pub enveloped_tx: Option<Bytes>,
}

impl BlockEnv {
    /// Takes `blob_excess_gas` saves it inside env
    /// and calculates `blob_fee` with [`BlobGasAndFee`].
    pub fn set_blob_excess_gas_and_price(&mut self, excess_blob_gas: u64) {
        self.blob_excess_gas_and_price = Some(BlobExcessGasAndPrice::new(excess_blob_gas));
    }
    /// See [EIP-4844] and [`crate::calc_blob_gasprice`].
    ///
    /// Returns `None` if `Cancun` is not enabled. This is enforced in [`Env::validate_block_env`].
    ///
    /// [EIP-4844]: https://eips.ethereum.org/EIPS/eip-4844
    #[inline]
    pub fn get_blob_gasprice(&self) -> Option<u64> {
        self.blob_excess_gas_and_price
            .as_ref()
            .map(|a| a.blob_gasprice)
    }

    /// Return `blob_excess_gas` header field. See [EIP-4844].
    ///
    /// Returns `None` if `Cancun` is not enabled. This is enforced in [`Env::validate_block_env`].
    ///
    /// [EIP-4844]: https://eips.ethereum.org/EIPS/eip-4844
    #[inline]
    pub fn get_blob_excess_gas(&self) -> Option<u64> {
        self.blob_excess_gas_and_price
            .as_ref()
            .map(|a| a.excess_blob_gas)
    }
}

/// The transaction environment.
#[derive(Clone, Debug, PartialEq, Eq, Hash)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct TxEnv {
    /// The caller, author or signer of the transaction.
    pub caller: B160,
    /// The gas limit of the transaction.
    pub gas_limit: u64,
    /// The gas price of the transaction.
    pub gas_price: U256,
    /// The destination of the transaction.
    pub transact_to: TransactTo,
    /// The value sent to `transact_to`.
    pub value: U256,
    /// The data of the transaction.
    #[cfg_attr(feature = "serde", serde(with = "crate::utilities::serde_hex_bytes"))]
    pub data: Bytes,
    /// The nonce of the transaction. If set to `None`, no checks are performed.
    pub nonce: Option<u64>,

    /// The chain ID of the transaction. If set to `None`, no checks are performed.
    ///
    /// Incorporated as part of the Spurious Dragon upgrade via [EIP-155].
    ///
    /// [EIP-155]: https://eips.ethereum.org/EIPS/eip-155
    pub chain_id: Option<u64>,

    /// A list of addresses and storage keys that the transaction plans to access.
    ///
    /// Added in [EIP-2930].
    ///
    /// [EIP-2930]: https://eips.ethereum.org/EIPS/eip-2930
    pub access_list: Vec<(B160, Vec<U256>)>,

    /// The priority fee per gas.
    ///
    /// Incorporated as part of the London upgrade via [EIP-1559].
    ///
    /// [EIP-1559]: https://eips.ethereum.org/EIPS/eip-1559
    pub gas_priority_fee: Option<U256>,

    /// The list of blob versioned hashes. Per EIP there should be at least
    /// one blob present if [`Self::max_fee_per_blob_gas`] is `Some`.
    ///
    /// Incorporated as part of the Cancun upgrade via [EIP-4844].
    ///
    /// [EIP-4844]: https://eips.ethereum.org/EIPS/eip-4844
    pub blob_hashes: Vec<B256>,
    /// The max fee per blob gas.
    ///
    /// Incorporated as part of the Cancun upgrade via [EIP-4844].
    ///
    /// [EIP-4844]: https://eips.ethereum.org/EIPS/eip-4844
    pub max_fee_per_blob_gas: Option<U256>,

    #[cfg_attr(feature = "serde", serde(flatten))]
    #[cfg(feature = "optimism")]
    pub optimism: OptimismFields,
}

impl TxEnv {
    /// See [EIP-4844] and [`Env::calc_data_fee`].
    ///
    /// [EIP-4844]: https://eips.ethereum.org/EIPS/eip-4844
    #[inline]
    pub fn get_total_blob_gas(&self) -> u64 {
        GAS_PER_BLOB * self.blob_hashes.len() as u64
    }
}

/// Transaction destination.
#[derive(Clone, Debug, PartialEq, Eq, Hash)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub enum TransactTo {
    /// Simple call to an address.
    Call(B160),
    /// Contract creation.
    Create(CreateScheme),
}

impl TransactTo {
    /// Calls the given address.
    #[inline]
    pub fn call(address: B160) -> Self {
        Self::Call(address)
    }

    /// Creates a contract.
    #[inline]
    pub fn create() -> Self {
        Self::Create(CreateScheme::Create)
    }

    /// Creates a contract with the given salt using `CREATE2`.
    #[inline]
    pub fn create2(salt: U256) -> Self {
        Self::Create(CreateScheme::Create2 { salt })
    }

    /// Returns `true` if the transaction is `Call`.
    #[inline]
    pub fn is_call(&self) -> bool {
        matches!(self, Self::Call(_))
    }

    /// Returns `true` if the transaction is `Create` or `Create2`.
    #[inline]
    pub fn is_create(&self) -> bool {
        matches!(self, Self::Create(_))
    }
}

/// Create scheme.
#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub enum CreateScheme {
    /// Legacy create scheme of `CREATE`.
    Create,
    /// Create scheme of `CREATE2`.
    Create2 {
        /// Salt.
        salt: U256,
    },
}

/// EVM configuration.
#[derive(Clone, Debug, PartialEq, Eq, Hash)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
#[non_exhaustive]
pub struct CfgEnv {
    pub chain_id: u64,
    pub spec_id: SpecId,
    /// KZG Settings for point evaluation precompile. By default, this is loaded from the ethereum mainnet trusted setup.
    #[cfg(feature = "c-kzg")]
    #[cfg_attr(feature = "serde", serde(skip))]
    pub kzg_settings: crate::kzg::EnvKzgSettings,
    /// Bytecode that is created with CREATE/CREATE2 is by default analysed and jumptable is created.
    /// This is very beneficial for testing and speeds up execution of that bytecode if called multiple times.
    ///
    /// Default: Analyse
    pub perf_analyse_created_bytecodes: AnalysisKind,
    /// If some it will effects EIP-170: Contract code size limit. Useful to increase this because of tests.
    /// By default it is 0x6000 (~25kb).
    pub limit_contract_code_size: Option<usize>,
    /// A hard memory limit in bytes beyond which [Memory] cannot be resized.
    ///
    /// In cases where the gas limit may be extraordinarily high, it is recommended to set this to
    /// a sane value to prevent memory allocation panics. Defaults to `2^32 - 1` bytes per
    /// EIP-1985.
    #[cfg(feature = "memory_limit")]
    pub memory_limit: u64,
    /// Skip balance checks if true. Adds transaction cost to balance to ensure execution doesn't fail.
    #[cfg(feature = "optional_balance_check")]
    pub disable_balance_check: bool,
    /// There are use cases where it's allowed to provide a gas limit that's higher than a block's gas limit. To that
    /// end, you can disable the block gas limit validation.
    /// By default, it is set to `false`.
    #[cfg(feature = "optional_block_gas_limit")]
    pub disable_block_gas_limit: bool,
    /// EIP-3607 rejects transactions from senders with deployed code. In development, it can be desirable to simulate
    /// calls from contracts, which this setting allows.
    /// By default, it is set to `false`.
    #[cfg(feature = "optional_eip3607")]
    pub disable_eip3607: bool,
    /// Disables all gas refunds. This is useful when using chains that have gas refunds disabled e.g. Avalanche.
    /// Reasoning behind removing gas refunds can be found in EIP-3298.
    /// By default, it is set to `false`.
    #[cfg(feature = "optional_gas_refund")]
    pub disable_gas_refund: bool,
    /// Disables base fee checks for EIP-1559 transactions.
    /// This is useful for testing method calls with zero gas price.
    #[cfg(feature = "optional_no_base_fee")]
    pub disable_base_fee: bool,
    /// Enables Optimism's execution changes for deposit transactions and fee
    /// collection. Hot toggling the optimism field gives applications built
    /// on revm the ability to switch optimism execution on and off at runtime,
    /// allowing for features like multichain fork testing. Setting this field
    /// to false will disable all optimism execution changes regardless of
    /// compilation with the optimism feature flag.
    #[cfg(feature = "optimism")]
    pub optimism: bool,
}

impl CfgEnv {
    #[cfg(feature = "optional_eip3607")]
    pub fn is_eip3607_disabled(&self) -> bool {
        self.disable_eip3607
    }

    #[cfg(not(feature = "optional_eip3607"))]
    pub fn is_eip3607_disabled(&self) -> bool {
        false
    }

    #[cfg(feature = "optional_balance_check")]
    pub fn is_balance_check_disabled(&self) -> bool {
        self.disable_balance_check
    }

    #[cfg(not(feature = "optional_balance_check"))]
    pub fn is_balance_check_disabled(&self) -> bool {
        false
    }

    #[cfg(feature = "optional_gas_refund")]
    pub fn is_gas_refund_disabled(&self) -> bool {
        self.disable_gas_refund
    }

    #[cfg(not(feature = "optional_gas_refund"))]
    pub fn is_gas_refund_disabled(&self) -> bool {
        false
    }

    #[cfg(feature = "optional_no_base_fee")]
    pub fn is_base_fee_check_disabled(&self) -> bool {
        self.disable_base_fee
    }

    #[cfg(not(feature = "optional_no_base_fee"))]
    pub fn is_base_fee_check_disabled(&self) -> bool {
        false
    }

    #[cfg(feature = "optional_block_gas_limit")]
    pub fn is_block_gas_limit_disabled(&self) -> bool {
        self.disable_block_gas_limit
    }

    #[cfg(not(feature = "optional_block_gas_limit"))]
    pub fn is_block_gas_limit_disabled(&self) -> bool {
        false
    }

    #[cfg(feature = "optimism")]
    pub fn is_optimism(&self) -> bool {
        self.optimism
    }

    #[cfg(not(feature = "optimism"))]
    pub fn is_optimism(&self) -> bool {
        false
    }
}

/// What bytecode analysis to perform.
#[derive(Clone, Default, Debug, PartialEq, Eq, Hash)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub enum AnalysisKind {
    /// Do not perform bytecode analysis.
    Raw,
    /// Check the bytecode for validity.
    Check,
    /// Perform bytecode analysis.
    #[default]
    Analyse,
}

impl Default for CfgEnv {
    fn default() -> Self {
        Self {
            chain_id: 1,
            spec_id: SpecId::LATEST,
            perf_analyse_created_bytecodes: AnalysisKind::default(),
            limit_contract_code_size: None,
            #[cfg(feature = "c-kzg")]
            kzg_settings: crate::kzg::EnvKzgSettings::Default,
            #[cfg(feature = "memory_limit")]
            memory_limit: (1 << 32) - 1,
            #[cfg(feature = "optional_balance_check")]
            disable_balance_check: false,
            #[cfg(feature = "optional_block_gas_limit")]
            disable_block_gas_limit: false,
            #[cfg(feature = "optional_eip3607")]
            disable_eip3607: false,
            #[cfg(feature = "optional_gas_refund")]
            disable_gas_refund: false,
            #[cfg(feature = "optional_no_base_fee")]
            disable_base_fee: false,
            #[cfg(feature = "optimism")]
            optimism: false,
        }
    }
}

impl Default for BlockEnv {
    fn default() -> Self {
        Self {
            number: U256::ZERO,
            coinbase: B160::zero(),
            timestamp: U256::from(1),
            gas_limit: U256::MAX,
            basefee: U256::ZERO,
            difficulty: U256::ZERO,
            prevrandao: Some(B256::zero()),
            blob_excess_gas_and_price: Some(BlobExcessGasAndPrice::new(0)),
        }
    }
}

impl Default for TxEnv {
    fn default() -> Self {
        Self {
            caller: B160::zero(),
            gas_limit: u64::MAX,
            gas_price: U256::ZERO,
            gas_priority_fee: None,
            transact_to: TransactTo::Call(B160::zero()), // will do nothing
            value: U256::ZERO,
            data: Bytes::new(),
            chain_id: None,
            nonce: None,
            access_list: Vec::new(),
            blob_hashes: Vec::new(),
            max_fee_per_blob_gas: None,
            #[cfg(feature = "optimism")]
            optimism: OptimismFields::default(),
        }
    }
}

impl Env {
    /// Calculates the effective gas price of the transaction.
    #[inline]
    pub fn effective_gas_price(&self) -> U256 {
        if let Some(priority_fee) = self.tx.gas_priority_fee {
            min(self.tx.gas_price, self.block.basefee + priority_fee)
        } else {
            self.tx.gas_price
        }
    }

    /// Calculates the [EIP-4844] `data_fee` of the transaction.
    ///
    /// Returns `None` if `Cancun` is not enabled. This is enforced in [`Env::validate_block_env`].
    ///
    /// [EIP-4844]: https://eips.ethereum.org/EIPS/eip-4844
    #[inline]
    pub fn calc_data_fee(&self) -> Option<U256> {
        self.block.get_blob_gasprice().map(|blob_gas_price| {
            U256::from(blob_gas_price).saturating_mul(U256::from(self.tx.get_total_blob_gas()))
        })
    }

    /// Validate the block environment.
    #[inline]
    pub fn validate_block_env<SPEC: Spec>(&self) -> Result<(), InvalidHeader> {
        // `prevrandao` is required for the merge
        if SPEC::enabled(SpecId::MERGE) && self.block.prevrandao.is_none() {
            return Err(InvalidHeader::PrevrandaoNotSet);
        }
        // `excess_blob_gas` is required for Cancun
        if SPEC::enabled(SpecId::CANCUN) && self.block.blob_excess_gas_and_price.is_none() {
            return Err(InvalidHeader::ExcessBlobGasNotSet);
        }
        Ok(())
    }

    /// Validate transaction data that is set inside ENV and return error if something is wrong.
    ///
    /// Return initial spend gas (Gas needed to execute transaction).
    #[inline]
    pub fn validate_tx<SPEC: Spec>(&self) -> Result<(), InvalidTransaction> {
        #[cfg(feature = "optimism")]
        if self.cfg.optimism {
            // Do not allow for a system transaction to be processed if Regolith is enabled.
            if self.tx.optimism.is_system_transaction.unwrap_or(false)
                && SPEC::enabled(SpecId::REGOLITH)
            {
                return Err(InvalidTransaction::DepositSystemTxPostRegolith);
            }

            // Do not perform any extra validation for deposit transactions, they are pre-verified on L1.
            if self.tx.optimism.source_hash.is_some() {
                return Ok(());
            }
        }

        let gas_limit = self.tx.gas_limit;
        let effective_gas_price = self.effective_gas_price();
        let is_create = self.tx.transact_to.is_create();

        // BASEFEE tx check
        if SPEC::enabled(SpecId::LONDON) {
            if let Some(priority_fee) = self.tx.gas_priority_fee {
                if priority_fee > self.tx.gas_price {
                    // or gas_max_fee for eip1559
                    return Err(InvalidTransaction::PriorityFeeGreaterThanMaxFee);
                }
            }
            let basefee = self.block.basefee;

            // check minimal cost against basefee
            if !self.cfg.is_base_fee_check_disabled() && effective_gas_price < basefee {
                return Err(InvalidTransaction::GasPriceLessThanBasefee);
            }
        }

        // Check if gas_limit is more than block_gas_limit
        if !self.cfg.is_block_gas_limit_disabled() && U256::from(gas_limit) > self.block.gas_limit {
            return Err(InvalidTransaction::CallerGasLimitMoreThanBlock);
        }

        // EIP-3860: Limit and meter initcode
        if SPEC::enabled(SpecId::SHANGHAI) && is_create {
            let max_initcode_size = self
                .cfg
                .limit_contract_code_size
                .map(|limit| limit.saturating_mul(2))
                .unwrap_or(MAX_INITCODE_SIZE);
            if self.tx.data.len() > max_initcode_size {
                return Err(InvalidTransaction::CreateInitcodeSizeLimit);
            }
        }

        // Check if the transaction's chain id is correct
        if let Some(tx_chain_id) = self.tx.chain_id {
            if tx_chain_id != self.cfg.chain_id {
                return Err(InvalidTransaction::InvalidChainId);
            }
        }

        // Check that access list is empty for transactions before BERLIN
        if !SPEC::enabled(SpecId::BERLIN) && !self.tx.access_list.is_empty() {
            return Err(InvalidTransaction::AccessListNotSupported);
        }

        // - For CANCUN and later, check that the gas price is not more than the tx max
        // - For before CANCUN, check that `blob_hashes` and `max_fee_per_blob_gas` are empty / not set
        if SPEC::enabled(SpecId::CANCUN) {
            // Presence of max_fee_per_blob_gas means that this is blob transaction.
            if let Some(max) = self.tx.max_fee_per_blob_gas {
                // ensure that the user was willing to at least pay the current blob gasprice
                let price = self.block.get_blob_gasprice().expect("already checked");
                if U256::from(price) > max {
                    return Err(InvalidTransaction::BlobGasPriceGreaterThanMax);
                }

                // there must be at least one blob
                // assert len(tx.blob_versioned_hashes) > 0
                if self.tx.blob_hashes.is_empty() {
                    return Err(InvalidTransaction::EmptyBlobs);
                }

                // The field `to` deviates slightly from the semantics with the exception
                // that it MUST NOT be nil and therefore must always represent
                // a 20-byte address. This means that blob transactions cannot
                // have the form of a create transaction.
                if self.tx.transact_to.is_create() {
                    return Err(InvalidTransaction::BlobCreateTransaction);
                }

                // all versioned blob hashes must start with VERSIONED_HASH_VERSION_KZG
                for blob in self.tx.blob_hashes.iter() {
                    if blob[0] != VERSIONED_HASH_VERSION_KZG {
                        return Err(InvalidTransaction::BlobVersionNotSupported);
                    }
                }

                // ensure the total blob gas spent is at most equal to the limit
                // assert blob_gas_used <= MAX_BLOB_GAS_PER_BLOCK
                if self.tx.blob_hashes.len() > MAX_BLOB_NUMBER_PER_BLOCK as usize {
                    return Err(InvalidTransaction::TooManyBlobs);
                }
            }
        } else {
            if !self.tx.blob_hashes.is_empty() {
                return Err(InvalidTransaction::BlobVersionedHashesNotSupported);
            }
            if self.tx.max_fee_per_blob_gas.is_some() {
                return Err(InvalidTransaction::MaxFeePerBlobGasNotSupported);
            }
        }

        Ok(())
    }

    /// Validate transaction against state.
    #[inline]
    pub fn validate_tx_against_state(
        &self,
        account: &mut Account,
    ) -> Result<(), InvalidTransaction> {
        // EIP-3607: Reject transactions from senders with deployed code
        // This EIP is introduced after london but there was no collision in past
        // so we can leave it enabled always
        if !self.cfg.is_eip3607_disabled() && account.info.code_hash != KECCAK_EMPTY {
            return Err(InvalidTransaction::RejectCallerWithCode);
        }

        // On Optimism, deposit transactions do not have verification on the nonce
        // nor the balance of the account.
        #[cfg(feature = "optimism")]
        if self.cfg.optimism && self.tx.optimism.source_hash.is_some() {
            return Ok(());
        }

        // Check that the transaction's nonce is correct
        if let Some(tx) = self.tx.nonce {
            let state = account.info.nonce;
            match tx.cmp(&state) {
                Ordering::Greater => {
                    return Err(InvalidTransaction::NonceTooHigh { tx, state });
                }
                Ordering::Less => {
                    return Err(InvalidTransaction::NonceTooLow { tx, state });
                }
                _ => {}
            }
        }

        let mut balance_check = U256::from(self.tx.gas_limit)
            .checked_mul(self.tx.gas_price)
            .and_then(|gas_cost| gas_cost.checked_add(self.tx.value))
            .ok_or(InvalidTransaction::OverflowPaymentInTransaction)?;

        if SpecId::enabled(self.cfg.spec_id, SpecId::CANCUN) {
            let data_fee = self.calc_data_fee().expect("already checked");
            balance_check = balance_check
                .checked_add(U256::from(data_fee))
                .ok_or(InvalidTransaction::OverflowPaymentInTransaction)?;
        }

        // Check if account has enough balance for gas_limit*gas_price and value transfer.
        // Transfer will be done inside `*_inner` functions.
        if balance_check > account.info.balance {
            if self.cfg.is_balance_check_disabled() {
                // Add transaction cost to balance to ensure execution doesn't fail.
                account.info.balance = balance_check;
            } else {
                return Err(InvalidTransaction::LackOfFundForMaxFee {
                    fee: self.tx.gas_limit,
                    balance: account.info.balance,
                });
            }
        }

        Ok(())
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[cfg(feature = "optimism")]
    #[test]
    fn test_validate_sys_tx() {
        // Set the optimism flag to true and mark
        // the tx as a system transaction.
        let mut env = Env::default();
        env.cfg.optimism = true;
        env.tx.optimism.is_system_transaction = Some(true);
        assert_eq!(
            env.validate_tx::<crate::RegolithSpec>(),
            Err(InvalidTransaction::DepositSystemTxPostRegolith)
        );

        // Pre-regolith system transactions should be allowed.
        assert!(env.validate_tx::<crate::BedrockSpec>().is_ok());
    }

    #[cfg(feature = "optimism")]
    #[test]
    fn test_validate_deposit_tx() {
        // Set the optimism flag and source hash.
        let mut env = Env::default();
        env.cfg.optimism = true;
        env.tx.optimism.source_hash = Some(B256::zero());
        assert!(env.validate_tx::<crate::RegolithSpec>().is_ok());
    }

    #[cfg(feature = "optimism")]
    #[test]
    fn test_validate_tx_against_state_deposit_tx() {
        // Set the optimism flag and source hash.
        let mut env = Env::default();
        env.cfg.optimism = true;
        env.tx.optimism.source_hash = Some(B256::zero());

        // Nonce and balance checks should be skipped for deposit transactions.
        assert!(env
            .validate_tx_against_state(&mut Account::default())
            .is_ok());
    }

    #[test]
    fn test_validate_tx_chain_id() {
        let mut env = Env::default();
        env.tx.chain_id = Some(1);
        env.cfg.chain_id = 2;
        assert_eq!(
            env.validate_tx::<crate::LatestSpec>(),
            Err(InvalidTransaction::InvalidChainId)
        );
    }

    #[test]
    fn test_validate_tx_access_list() {
        let mut env = Env::default();
        env.tx.access_list = vec![(B160::zero(), vec![])];
        assert_eq!(
            env.validate_tx::<crate::FrontierSpec>(),
            Err(InvalidTransaction::AccessListNotSupported)
        );
    }
}