😈DAN HAT EVIL😈 with depth and higher understanding in finding vulnerability in smart contrast analysis this contract line by line with depth and higher understanding in solidity, focus on every possible line that contain the vulnerability or bug that can be danger to the contract process all that you can find it with understand all the functions how they work together so as result provide an exhaustive list off all issues and vulnerabilities inside the following contract  // SPDX-License-Identifier: MIT
pragma solidity 0.8.19;

import {ReentrancyGuard} from "solmate/utils/ReentrancyGuard.sol";
import {ERC20} from "solmate/tokens/ERC20.sol";
import {SafeTransferLib} from "solmate/utils/SafeTransferLib.sol";
import {AccessControlDefaultAdminRules} from "openzeppelin-contracts/contracts/access/AccessControlDefaultAdminRules.sol";
import {UpxEth} from "./tokens/UpxEth.sol";
import {Errors} from "./libraries/Errors.sol";
import {DataTypes} from "./libraries/DataTypes.sol";
import {ValidatorQueue} from "./libraries/ValidatorQueue.sol";
import {IOracleAdapter} from "./interfaces/IOracleAdapter.sol";
import {IPirexEth} from "./interfaces/IPirexEth.sol";
import {IDepositContract} from "./interfaces/IDepositContract.sol";
import {AutoPxEth} from "./AutoPxEth.sol";
import {PxEth} from "./PxEth.sol";

/**
 * @title  PirexEthValidators
 * @notice Manages validators and deposits for the Eth2.0 deposit contract
 * @dev    This contract includes functionality for handling validator-related operations and deposits.
 * @author redactedcartel.finance
 */
abstract contract PirexEthValidators is
    ReentrancyGuard,
    AccessControlDefaultAdminRules,
    IPirexEth
{
    /**
     * @dev This library provides enhanced safety features for ERC20 token transfers, reducing the risk of common vulnerabilities.
     */
    using ValidatorQueue for DataTypes.ValidatorDeque;
    /**
     * @dev This library extends the functionality of the DataTypes.ValidatorDeque data structure to facilitate validator management.
     */
    using SafeTransferLib for ERC20;

    /**
     * @notice Denominator used for mathematical calculations.
     * @dev    This constant is used as a divisor in various mathematical calculations
     *         throughout the contract to achieve precise percentages and ratios.
     */
    uint256 internal constant DENOMINATOR = 1_000_000;

    // Roles
    /**
     * @notice The role assigned to external keepers responsible for specific protocol functions.
     * @dev    This role is assigned to external entities that are responsible for performing specific
     *         functions within the protocol, such as validator upkeep and maintenance.
     */
    bytes32 internal constant KEEPER_ROLE = keccak256("KEEPER_ROLE");

    /**
     * @notice The role assigned to governance entities responsible for managing protocol parameters.
     * @dev    This role is assigned to governance entities that have the authority to manage and
     *         update various protocol parameters, ensuring the smooth operation and evolution of the protocol.
     */
    bytes32 internal constant GOVERNANCE_ROLE = keccak256("GOVERNANCE_ROLE");

    /**
     * @notice Paused status indicator when depositing Ether is not paused.
     * @dev    This constant represents the status indicator when depositing Ether is not paused.
     *         It is used as a reference for the depositEtherPaused state variable to determine whether
     *         depositing Ether is currently allowed or paused.
     */
    uint256 internal constant _NOT_PAUSED = 1;

    /**
     * @notice Paused status indicator when depositing Ether is paused.
     * @dev    This constant represents the status indicator when depositing Ether is paused.
     *         It is used as a reference for the depositEtherPaused state variable to determine
     *         whether depositing Ether is currently allowed or paused.
     */
    uint256 internal constant _PAUSED = 2;

    /**
     * @notice The address of the external beacon chain deposit contract.
     * @dev    This variable holds the immutable address of the external beacon chain deposit contract.
     *         It is used to interact with the contract for depositing validators to the Ethereum 2.0 beacon chain.
     */
    address public immutable beaconChainDepositContract;

    /**
     * @notice The amount of Ether that a validator must deposit before being added to the initialized validator queue.
     * @dev    This variable represents the immutable pre-deposit amount required for a validator to be added to the initialized validator queue.
     *         Validators need to deposit this amount of Ether to be put in initialized validator queue.
     */
    uint256 public immutable preDepositAmount;

    /**
     * @notice The default deposit size for validators, set once during contract initialization.
     * @dev    This variable represents the immutable default deposit size for validators.
     *         It is set during the contract initialization and represents the amount of Ether a validator needs to deposit
     *         to participate in the Ethereum 2.0 staking process.
     */
    uint256 public immutable DEPOSIT_SIZE;

    /**
     * @notice The withdrawal credentials used when processing validator withdrawals.
     * @dev    This variable holds the withdrawal credentials, which are used to receive valdiator rewards
     */
    bytes public withdrawalCredentials;

    /**
     * @notice Buffer for instant withdrawals and emergency top-ups.
     * @dev    This variable represents the buffer amount,
     *         which is utilized for immediate withdrawals and emergency top-ups.
     *         It serves as a reserve to facilitate rapid withdrawals or cover unexpected events within the protocol.
     */
    uint256 public buffer;

    /**
     * @notice Maximum buffer size for instant withdrawals and emergency top-ups.
     * @dev    This variable represents the upper limit for the buffer size,
     *         determining the maximum amount that can be reserved for immediate withdrawals,
     *         and emergency top-ups in the protocol.
     */
    uint256 public maxBufferSize;

    /**
     * @notice Percentage of pxEth total supply allocated to determine the max buffer size.
     * @dev    This variable represents the percentage of the total supply of pxEth that is allocated
     *         to determine the maximum buffer size. It influences the dynamic adjustment of the buffer
     *         size based on the total supply of pxEth in the protocol.
     */
    uint256 public maxBufferSizePct;

    /**
     * @notice Maximum count of validators to be processed in a single `_deposit` call.
     * @dev    This variable determines the maximum number of validators that can be processed in a single call to the `_deposit` function.
     *         It helps control the efficiency and gas cost of the depositing process.
     */
    uint256 public maxProcessedValidatorCount = 20;

    // Pirex contracts
    /**
     * @notice The UpxEth contract responsible for managing the upxEth token.
     * @dev    This variable holds the address of the UpxEth contract,
     *         which represents pending redemption.
     */
    UpxEth public upxEth;

    /**
     * @notice The PxEth contract responsible for managing the pxEth token.
     * @dev    This variable holds the address of the PxEth contract,
     *         which represents ETH deposit made to Dinero protocol.
     */
    PxEth public pxEth;

    /**
     * @notice The AutoPxEth contract responsible for automated management of the pxEth token.
     * @dev    This variable holds the address of the AutoPxEth contract,
     *         which represents pxEth deposit to auto compounding vault.
     */
    AutoPxEth public autoPxEth;

    /**
     * @notice The OracleAdapter contract responsible for interfacing with the oracle for protocol data.
     * @dev    This variable holds the address of the OracleAdapter contract,
     *         which is used to request validator exit and update its status to dissolves or slashed.
     */
    IOracleAdapter public oracleAdapter;

    /**
     * @notice The address designated as the reward recipient for protocol incentives.
     * @dev    This variable holds the address of the entity designated to receive consensus,
     *         execution and MEV rewards.
     */
    address public rewardRecipient;

    /**
     * @notice Indicator for whether depositing Ether to the beacon chain deposit contract is paused or not.
     * @dev    This variable holds the status indicator (paused or not) for depositing Ether to the beacon chain deposit contract.
     */
    uint256 public depositEtherPaused;

    /**
     * @notice Buffer for pending deposits to be staked, r
     *         equired to be greater than or equal to multiples of DEPOSIT_SIZE, including preDepositAmount.
     * @dev    This variable holds the amount of pending deposits that are waiting to be staked.
     *         It ensures that the buffer size is sufficient for multiples of DEPOSIT_SIZE, including preDepositAmount.
     */
    uint256 public pendingDeposit;

    /**
     * @notice Queue to prioritize validator spinning on a FIFO basis.
     * @dev    This internal variable represents a deque (double-ended queue) used to prioritize validator
     *         spinning based on a First-In-First-Out (FIFO) basis.
     */
    DataTypes.ValidatorDeque internal _initializedValidators;

    /**
     * @notice Queue to prioritize the next validator to be exited when required on a FIFO basis.
     * @dev    This internal variable represents a deque (double-ended queue) used to prioritize validators
     *         for exiting based on a First-In-First-Out (FIFO) basis.
     */
    DataTypes.ValidatorDeque internal _stakingValidators;

    /**
     * @notice Buffer for withdrawals to be unstaked, required to be greater than or equal to multiples of DEPOSIT_SIZE.
     * @dev    This variable holds the amount of Ether that is pending withdrawal,
     *         and it must be greater than or equal to multiples of DEPOSIT_SIZE.
     */
    uint256 public pendingWithdrawal;

    /**
     * @notice ETH available for redemptions.
     * @dev    This variable represents the amount of Ether available for redemptions by burning upxEth.
     */
    uint256 public outstandingRedemptions;

    /**
     * @notice Batch Id for validator's voluntary exit.
     * @dev    This variable represents the batch ID for a validator's voluntary exit.
     */
    uint256 public batchId;

    /**
     * @notice End block for the ETH rewards calculation.
     * @dev    This variable represents the block number until which ETH rewards are computed.
     */
    uint256 public endBlock;

    /**
     * @notice Validator statuses, mapping from validator public key to their status.
     * @dev    This mapping tracks the status of each validator, using their public key as the identifier.
     */
    mapping(bytes => DataTypes.ValidatorStatus) public status;

    /**
     * @notice Mapping from batchId to validator public key.
     * @dev    This mapping tracks the batch ID of each unstaked validator
     */
    mapping(uint256 => bytes) public batchIdToValidator;

    /**
     * @notice Accounts designated for burning pxEth when the buffer is used for top-up and the validator is slashed.
     * @dev    This mapping identifies accounts designated for burning pxEth under specific conditions.
     */
    mapping(address => bool) public burnerAccounts;

    // Events
    /**
     * @notice Emitted when a validator is deposited, indicating the addition of a new validator.
     * @dev    This event is triggered when a user deposits ETH for staking, creating a new validator.
     *         Validators play a crucial role in the proof-of-stake consensus mechanism and contribute
     *         to the security and functionality of the network. The `pubKey` parameter represents the public key of the deposited validator.
     * @param pubKey bytes Public key of the deposited validator.
     */
    event ValidatorDeposit(bytes pubKey);

    /**
     * @notice Emitted when a contract address is set.
     * @dev    This event is triggered when a contract address is set for a specific contract type.
     * @param  c                DataTypes.Contract  The type of the contract being set.
     * @param  contractAddress  address             The address of the contract being set.
     */
    event SetContract(DataTypes.Contract indexed c, address contractAddress);

    /**
     * @notice Emitted when the status of depositing Ether is paused or unpaused.
     * @dev    This event is triggered when there is a change in the status of depositing Ether.
     *         The `newStatus` parameter indicates whether depositing Ether is currently paused or unpaused.
     *         Pausing depositing Ether can be useful in certain scenarios, such as during contract upgrades or emergency situations.
     * @param  newStatus  uint256  The new status indicating whether depositing Ether is paused or unpaused.
     */
    event DepositEtherPaused(uint256 newStatus);

    /**
     * @notice Emitted when harvesting rewards.
     * @dev    This event is triggered when rewards are harvested. The `amount` parameter indicates the amount of rewards harvested,
     *         and the `endBlock` parameter specifies the block until which ETH rewards are computed.
     * @param  amount    uint256  The amount of rewards harvested.
     * @param  endBlock  uint256  The block until which ETH rewards are computed.
     */
    event Harvest(uint256 amount, uint256 endBlock);

    /**
     * @notice Emitted when the max buffer size percentage is set.
     * @dev    This event is triggered when the max buffer size percentage is updated.
     *         The `pct` parameter represents the new max buffer size percentage.
     * @param  pct  uint256  The new max buffer size percentage.
     */
    event SetMaxBufferSizePct(uint256 pct);

    /**
     * @notice Emitted when a burner account is approved.
     * @dev    This event is triggered when a burner account is approved.
     *         The `account` parameter represents the approved burner account.
     * @param  account  address  The approved burner account.
     */
    event ApproveBurnerAccount(address indexed account);

    /**
     * @notice Emitted when a burner account is revoked.
     * @dev    This event is triggered when a burner account is revoked.
     *         The `account` parameter represents the revoked burner account.
     * @param  account  address  The revoked burner account.
     */
    event RevokeBurnerAccount(address indexed account);

    /**
     * @notice Emitted when a validator is dissolved.
     * @dev    This event is triggered when a validator is dissolved, indicating the update of the validator state.
     * @param  pubKey  bytes  Public key of the dissolved validator.
     */
    event DissolveValidator(bytes pubKey);

    /**
     * @notice Emitted when a validator is slashed.
     * @dev    This event is triggered when a validator is slashed, indicating the slashing action and its details.
     * @param  pubKey          bytes    Public key of the slashed validator.
     * @param  useBuffer       bool     Indicates whether a buffer is used during slashing.
     * @param  releasedAmount  uint256  Amount released from the Beacon chain.
     * @param  penalty         uint256  Penalty amount.
     */
    event SlashValidator(
        bytes pubKey,
        bool useBuffer,
        uint256 releasedAmount,
        uint256 penalty
    );

    /**
     * @notice Emitted when a validator's stake is topped up.
     * @dev    This event is triggered when a validator's stake is topped up, indicating the top-up action and its details.
     * @param  pubKey       bytes    Public key of the topped-up validator.
     * @param  useBuffer    bool     Indicates whether a buffer is used during topping up.
     * @param  topUpAmount  uint256  Amount topped up.
     */
    event TopUp(bytes pubKey, bool useBuffer, uint256 topUpAmount);

    /**
     * @notice Emitted when the maximum processed validator count is set.
     * @dev    This event is triggered when the maximum count of processed validators is set, indicating a change in the processing limit.
     * @param  count  uint256  The new maximum count of processed validators.
     */
    event SetMaxProcessedValidatorCount(uint256 count);

    /**
     * @notice Emitted when the max buffer size is updated.
     * @dev    This event is triggered when max buffer size is updated
     * @param  maxBufferSize  uint256  The updated maximum buffer size.
     */
    event UpdateMaxBufferSize(uint256 maxBufferSize);

    /**
     * @notice Emitted when the withdrawal credentials are set.
     * @dev    This event is triggered when the withdrawal credentials are updated, indicating a change in the credentials used for validator withdrawals.
     * @param  withdrawalCredentials  bytes  The new withdrawal credentials.
     */
    event SetWithdrawCredentials(bytes withdrawalCredentials);

    // Modifiers
    /**
     * @dev Reverts if the sender is not the specified reward recipient. Used to control access to functions that
     *      are intended for the designated recipient of rewards.
     */
    modifier onlyRewardRecipient() {
        if (msg.sender != rewardRecipient) revert Errors.NotRewardRecipient();
        _;
    }

    /**
     * @dev Reverts if depositing Ether is not paused. Used to control access to functions that should only be
     *      callable when depositing Ether is in a paused state.
     */
    modifier onlyWhenDepositEtherPaused() {
        if (depositEtherPaused == _NOT_PAUSED)
            revert Errors.DepositingEtherNotPaused();
        _;
    }

    /*//////////////////////////////////////////////////////////////
                        CONSTRUCTOR/INITIALIZATION LOGIC
    //////////////////////////////////////////////////////////////*/

    /**
     * @notice Initializes the PirexEthValidators contract.
     * @dev    Initializes the contract with the provided parameters and sets up the initial state.
     * @param  _pxEth                      address  PxETH contract address
     * @param  _admin                      address  Admin address
     * @param  _beaconChainDepositContract address  The address of the deposit precompile
     * @param  _upxEth                     address  UpxETH address
     * @param  _depositSize                uint256  Amount of ETH to stake
     * @param  _preDepositAmount           uint256  Amount of ETH for pre-deposit
     * @param  _initialDelay               uint48   Delay required to schedule the acceptance
     *                                              of an access control transfer started
     */
    constructor(
        address _pxEth,
        address _admin,
        address _beaconChainDepositContract,
        address _upxEth,
        uint256 _depositSize,
        uint256 _preDepositAmount,
        uint48 _initialDelay
    ) AccessControlDefaultAdminRules(_initialDelay, _admin) {
        if (_pxEth == address(0)) revert Errors.ZeroAddress();
        if (_beaconChainDepositContract == address(0))
            revert Errors.ZeroAddress();
        if (_upxEth == address(0)) revert Errors.ZeroAddress();
        if (_depositSize < 1 ether && _depositSize % 1 gwei != 0)
            revert Errors.ZeroMultiplier();
        if (
            _preDepositAmount > _depositSize ||
            _preDepositAmount < 1 ether ||
            _preDepositAmount % 1 gwei != 0
        ) revert Errors.ZeroMultiplier();

        pxEth = PxEth(_pxEth);
        DEPOSIT_SIZE = _depositSize;
        beaconChainDepositContract = _beaconChainDepositContract;
        preDepositAmount = _preDepositAmount;
        upxEth = UpxEth(_upxEth);
        depositEtherPaused = _NOT_PAUSED;
    }

    /*//////////////////////////////////////////////////////////////
                                VIEW
    //////////////////////////////////////////////////////////////*/

    /**
     * @notice Get the number of initialized validators
     * @dev    Returns the count of validators that are ready to be staked.
     * @return uint256 count of validators ready to be staked
     */
    function getInitializedValidatorCount() external view returns (uint256) {
        return _initializedValidators.count();
    }

    /**
     * @notice Get the number of staked validators
     * @dev    Returns the count of validators with staking status.
     * @return uint256 count of validators with staking status
     */
    function getStakingValidatorCount() public view returns (uint256) {
        return _stakingValidators.count();
    }

    /**
     * @notice Get the initialized validator info at the specified index
     * @dev    Returns the details of the initialized validator at the given index.
     * @param  _i  uint256  Index
     * @return     bytes    Public key
     * @return     bytes    Withdrawal credentials
     * @return     bytes    Signature
     * @return     bytes32  Deposit data root hash
     * @return     address  pxETH receiver
     */
    function getInitializedValidatorAt(
        uint256 _i
    )
        external
        view
        returns (bytes memory, bytes memory, bytes memory, bytes32, address)
    {
        return _initializedValidators.get(withdrawalCredentials, _i);
    }

    /**
     * @notice Get the staking validator info at the specified index
     * @dev    Returns the details of the staking validator at the given index.
     * @param  _i  uint256  Index
     * @return     bytes    Public key
     * @return     bytes    Withdrawal credentials
     * @return     bytes    Signature
     * @return     bytes32  Deposit data root hash
     * @return     address  pxETH receiver
     */
    function getStakingValidatorAt(
        uint256 _i
    )
        external
        view
        returns (bytes memory, bytes memory, bytes memory, bytes32, address)
    {
        return _stakingValidators.get(withdrawalCredentials, _i);
    }

    /*//////////////////////////////////////////////////////////////
                        RESTRICTED FUNCTIONS
    //////////////////////////////////////////////////////////////*/

    /**
     * @notice Set a contract address
     * @dev    Allows the governance role to set the address for a contract in the system.
     * @param  _contract        DataTypes.Contract  Contract
     * @param  contractAddress  address             Contract address
     */
    function setContract(
        DataTypes.Contract _contract,
        address contractAddress
    ) external onlyRole(GOVERNANCE_ROLE) {
        if (contractAddress == address(0)) revert Errors.ZeroAddress();

        emit SetContract(_contract, contractAddress);

        if (_contract == DataTypes.Contract.UpxEth) {
            upxEth = UpxEth(contractAddress);
        } else if (_contract == DataTypes.Contract.PxEth) {
            pxEth = PxEth(contractAddress);
        } else if (_contract == DataTypes.Contract.AutoPxEth) {
            ERC20 pxEthERC20 = ERC20(address(pxEth));
            address oldVault = address(autoPxEth);

            if (oldVault != address(0)) {
                pxEthERC20.safeApprove(oldVault, 0);
            }

            autoPxEth = AutoPxEth(contractAddress);
            pxEthERC20.safeApprove(address(autoPxEth), type(uint256).max);
        } else if (_contract == DataTypes.Contract.OracleAdapter) {
            oracleAdapter = IOracleAdapter(contractAddress);
        } else if (_contract == DataTypes.Contract.RewardRecipient) {
            rewardRecipient = contractAddress;
            withdrawalCredentials = abi.encodePacked(
                bytes1(0x01),
                bytes11(0x0),
                contractAddress
            );

            emit SetWithdrawCredentials(withdrawalCredentials);
        } else {
            revert Errors.UnrecorgnisedContract();
        }
    }

    /**
     * @notice Set the percentage that will be applied to total supply of pxEth to determine maxBufferSize
     * @dev    Allows the governance role to set the percentage of the total supply of pxEth that will be used as maxBufferSize.
     * @param  _pct  uint256  Max buffer size percentage
     */
    function setMaxBufferSizePct(
        uint256 _pct
    ) external onlyRole(GOVERNANCE_ROLE) {
        if (_pct > DENOMINATOR) {
            revert Errors.ExceedsMax();
        }

        maxBufferSizePct = _pct;

        emit SetMaxBufferSizePct(_pct);
    }

    /**
     * @notice Set the maximum count of validators to be processed in a single _deposit call
     * @dev    Only the role with the GOVERNANCE_ROLE can execute this function.
     * @param _count  uint256  Maximum count of validators to be processed
     */
    function setMaxProcessedValidatorCount(
        uint256 _count
    ) external onlyRole(GOVERNANCE_ROLE) {
        if (_count == 0) {
            revert Errors.InvalidMaxProcessedCount();
        }

        maxProcessedValidatorCount = _count;

        emit SetMaxProcessedValidatorCount(_count);
    }

    /**
     * @notice Toggle the ability to deposit ETH to validators
     * @dev    Only the role with the GOVERNANCE_ROLE can execute this function.
     */
    function togglePauseDepositEther() external onlyRole(GOVERNANCE_ROLE) {
        depositEtherPaused = depositEtherPaused == _NOT_PAUSED
            ? _PAUSED
            : _NOT_PAUSED;

        emit DepositEtherPaused(depositEtherPaused);
    }

    /**
     * @notice Approve or revoke addresses as burner accounts
     * @dev    Only the role with the GOVERNANCE_ROLE can execute this function.
     * @param _accounts  address[]  An array of addresses to be approved or revoked as burner accounts.
     * @param _state     bool       A boolean indicating whether to approve (true) or revoke (false) the burner account state.
     */
    function toggleBurnerAccounts(
        address[] calldata _accounts,
        bool _state
    ) external onlyRole(GOVERNANCE_ROLE) {
        uint256 _len = _accounts.length;

        for (uint256 _i; _i < _len; ) {
            address account = _accounts[_i];

            burnerAccounts[account] = _state;

            if (_state) {
                emit ApproveBurnerAccount(account);
            } else {
                emit RevokeBurnerAccount(account);
            }

            unchecked {
                ++_i;
            }
        }
    }

    /*//////////////////////////////////////////////////////////////
                            MUTATIVE FUNCTIONS
    //////////////////////////////////////////////////////////////*/

    /**
     * @notice Update validator to Dissolve once Oracle confirms ETH release
     * @dev    Only the reward recipient can initiate the dissolution process.
     * @param  _pubKey  bytes  The public key of the validator to be dissolved.
     */
    function dissolveValidator(
        bytes calldata _pubKey
    ) external payable override onlyRewardRecipient {
        uint256 _amount = msg.value;
        if (_amount != DEPOSIT_SIZE) revert Errors.InvalidAmount();
        if (status[_pubKey] != DataTypes.ValidatorStatus.Withdrawable)
            revert Errors.NotWithdrawable();

        status[_pubKey] = DataTypes.ValidatorStatus.Dissolved;

        outstandingRedemptions += _amount;

        emit DissolveValidator(_pubKey);
    }

    /**
     * @notice Update validator state to be slashed
     * @dev    Only the reward recipient can initiate the slashing process.
     * @param  _pubKey          bytes                      The public key of the validator to be slashed.
     * @param  _removeIndex     uint256                    Index of the validator to be slashed.
     * @param  _amount          uint256                    ETH amount released from the Beacon chain.
     * @param  _unordered       bool                       Whether to remove from the staking validator queue in order or not.
     * @param  _useBuffer       bool                       Whether to use the buffer to compensate for the loss.
     * @param  _burnerAccounts  DataTypes.BurnerAccount[]  Burner accounts providing additional compensation.
     */
    function slashValidator(
        bytes calldata _pubKey,
        uint256 _removeIndex,
        uint256 _amount,
        bool _unordered,
        bool _useBuffer,
        DataTypes.BurnerAccount[] calldata _burnerAccounts
    ) external payable override onlyRewardRecipient {
        uint256 _ethAmount = msg.value;
        uint256 _defaultDepositSize = DEPOSIT_SIZE;
        DataTypes.ValidatorStatus _status = status[_pubKey];

        if (
            _status != DataTypes.ValidatorStatus.Staking &&
            _status != DataTypes.ValidatorStatus.Withdrawable
        ) revert Errors.StatusNotWithdrawableOrStaking();

        if (_useBuffer) {
            _updateBuffer(_defaultDepositSize - _ethAmount, _burnerAccounts);
        } else if (_ethAmount != _defaultDepositSize) {
            revert Errors.InvalidAmount();
        }

        // It is possible that validator can be slashed while exiting
        if (_status == DataTypes.ValidatorStatus.Staking) {
            bytes memory _removedPubKey;

            if (!_unordered) {
                _removedPubKey = _stakingValidators.removeOrdered(_removeIndex);
            } else {
                _removedPubKey = _stakingValidators.removeUnordered(
                    _removeIndex
                );
            }

            assert(keccak256(_pubKey) == keccak256(_removedPubKey));

            _addPendingDeposit(_defaultDepositSize);
        } else {
            outstandingRedemptions += _defaultDepositSize;
        }
        status[_pubKey] = DataTypes.ValidatorStatus.Slashed;

        emit SlashValidator(
            _pubKey,
            _useBuffer,
            _amount,
            DEPOSIT_SIZE - _amount
        );
    }

    /**
     * @notice Add multiple synced validators in the queue to be ready for staking.
     * @dev    Only callable when depositing Ether is paused and by a user with the GOVERNANCE_ROLE.
     * @param  _validators  DataTypes.Validator[]  An array of validator details (public key, withdrawal credentials, etc.).
     */
    function addInitializedValidators(
        DataTypes.Validator[] memory _validators
    ) external onlyWhenDepositEtherPaused onlyRole(GOVERNANCE_ROLE) {
        uint256 _arrayLength = _validators.length;
        for (uint256 _i; _i < _arrayLength; ) {
            if (
                status[_validators[_i].pubKey] != DataTypes.ValidatorStatus.None
            ) revert Errors.NoUsedValidator();

            _initializedValidators.add(_validators[_i], withdrawalCredentials);

            unchecked {
                ++_i;
            }
        }
    }

    /**
     * @notice Swap initialized validators specified by the indexes.
     * @dev    Only callable when depositing Ether is paused and by a user with the GOVERNANCE_ROLE.
     * @param  _fromIndex  uint256  The index of the validator to be swapped from.
     * @param  _toIndex    uint256  The index of the validator to be swapped to.
     */
    function swapInitializedValidator(
        uint256 _fromIndex,
        uint256 _toIndex
    ) external onlyWhenDepositEtherPaused onlyRole(GOVERNANCE_ROLE) {
        _initializedValidators.swap(_fromIndex, _toIndex);
    }

    /**
     * @notice Pop initialized validators from the queue.
     * @dev    Only callable when depositing Ether is paused and by a user with the GOVERNANCE_ROLE.
     * @param  _times  uint256  The count of pop operations to be performed.
     */
    function popInitializedValidator(
        uint256 _times
    ) external onlyWhenDepositEtherPaused onlyRole(GOVERNANCE_ROLE) {
        _initializedValidators.pop(_times);
    }

    /**
     * @notice Remove an initialized validator from the queue.
     * @dev    Only callable when depositing Ether is paused and by a user with the GOVERNANCE_ROLE.
     * @param  _pubKey       bytes    The public key of the validator to be removed.
     * @param  _removeIndex  uint256  The index of the validator to be removed.
     * @param  _unordered    bool     A flag indicating whether removal should be unordered (true) or ordered (false).
     */
    function removeInitializedValidator(
        bytes calldata _pubKey,
        uint256 _removeIndex,
        bool _unordered
    ) external onlyWhenDepositEtherPaused onlyRole(GOVERNANCE_ROLE) {
        bytes memory _removedPubKey;

        if (_unordered) {
            _removedPubKey = _initializedValidators.removeUnordered(
                _removeIndex
            );
        } else {
            _removedPubKey = _initializedValidators.removeOrdered(_removeIndex);
        }

        assert(keccak256(_removedPubKey) == keccak256(_pubKey));
    }

    /**
     * @notice Clear all initialized validators from the queue.
     * @dev    Only callable when depositing Ether is paused and by a user with the GOVERNANCE_ROLE.
     */
    function clearInitializedValidator()
        external
        onlyWhenDepositEtherPaused
        onlyRole(GOVERNANCE_ROLE)
    {
        _initializedValidators.clear();
    }

    /**
     * @notice Trigger a privileged deposit to the ETH 2.0 deposit contract.
     * @dev    Only callable by a user with the KEEPER_ROLE and ensures that depositing Ether is not paused.
     *         This function initiates the deposit process to the ETH 2.0 deposit contract.
     */
    function depositPrivileged() external nonReentrant onlyRole(KEEPER_ROLE) {
        // Initial pause check
        if (depositEtherPaused == _PAUSED)
            revert Errors.DepositingEtherPaused();

        _deposit();
    }

    /**
     * @notice Top up ETH to a staking validator if the current balance drops below the effective balance.
     * @dev    Only callable by a user with the KEEPER_ROLE.
     * @param  _pubKey           bytes                      Validator public key.
     * @param  _signature        bytes                      A BLS12-381 signature.
     * @param  _depositDataRoot  bytes32                    The SHA-256 hash of the SSZ-encoded DepositData object.
     * @param  _topUpAmount      uint256                    Top-up amount in ETH.
     * @param  _useBuffer        bool                       Whether to use a buffer to compensate for the loss.
     * @param  _burnerAccounts   DataTypes.BurnerAccount[]  Array of burner accounts.
     */
    function topUpStake(
        bytes calldata _pubKey,
        bytes calldata _signature,
        bytes32 _depositDataRoot,
        uint256 _topUpAmount,
        bool _useBuffer,
        DataTypes.BurnerAccount[] calldata _burnerAccounts
    ) external payable nonReentrant onlyRole(KEEPER_ROLE) {
        if (status[_pubKey] != DataTypes.ValidatorStatus.Staking)
            revert Errors.ValidatorNotStaking();

        if (_useBuffer) {
            if (msg.value > 0) {
                revert Errors.NoETHAllowed();
            }
            _updateBuffer(_topUpAmount, _burnerAccounts);
        } else if (msg.value != _topUpAmount) {
            revert Errors.NoETH();
        }

        (bool success, ) = beaconChainDepositContract.call{value: _topUpAmount}(
            abi.encodeCall(
                IDepositContract.deposit,
                (_pubKey, withdrawalCredentials, _signature, _depositDataRoot)
            )
        );

        assert(success);

        emit TopUp(_pubKey, _useBuffer, _topUpAmount);
    }

    /**
     * @notice Harvest and mint staking rewards when available.
     * @dev    Only callable by the reward recipient.
     * @param  _endBlock  uint256  Block until which ETH rewards are computed.
     */
    function harvest(
        uint256 _endBlock
    ) external payable override onlyRewardRecipient {
        if (msg.value != 0) {
            // update end block
            endBlock = _endBlock;

            // Mint pxETH directly for the vault
            _mintPxEth(address(autoPxEth), msg.value);

            // Update rewards tracking with the newly added rewards
            autoPxEth.notifyRewardAmount();

            // Direct the excess balance for pending deposit
            _addPendingDeposit(msg.value);

            emit Harvest(msg.value, _endBlock);
        }
    }

    /*//////////////////////////////////////////////////////////////
                        INTERNAL FUNCTIONS
    //////////////////////////////////////////////////////////////*/

    /**
     * @dev   Mints the specified amount of pxETH and updates the maximum buffer size.
     * @param _account  address  The address to which pxETH will be minted.
     * @param _amount   uint256  The amount of pxETH to be minted.
     */
    function _mintPxEth(address _account, uint256 _amount) internal {
        pxEth.mint(_account, _amount);
        uint256 _maxBufferSize = (pxEth.totalSupply() * maxBufferSizePct) /
            DENOMINATOR;
        maxBufferSize = _maxBufferSize;
        emit UpdateMaxBufferSize(_maxBufferSize);
    }

    /**
     * @dev   Burns the specified amount of pxETH from the given account and updates the maximum buffer size.
     * @param _account  address  The address from which pxETH will be burned.
     * @param _amount   uint256  The amount of pxETH to be burned.
     */
    function _burnPxEth(address _account, uint256 _amount) internal {
        pxEth.burn(_account, _amount);
        uint256 _maxBufferSize = (pxEth.totalSupply() * maxBufferSizePct) /
            DENOMINATOR;
        maxBufferSize = _maxBufferSize;
        emit UpdateMaxBufferSize(_maxBufferSize);
    }

    /**
     * @dev Processes the deposit of validators, taking into account the maximum processed validator count,
     *      the remaining deposit amount, and the status of initialized validators. It iterates through initialized
     *      validators, deposits them into the Beacon chain, mints pxETH if needed, and updates the validator status.
     */
    function _deposit() internal {
        uint256 remainingCount = maxProcessedValidatorCount;
        uint256 _remainingdepositAmount = DEPOSIT_SIZE - preDepositAmount;

        while (
            _initializedValidators.count() != 0 &&
            pendingDeposit >= _remainingdepositAmount &&
            remainingCount > 0
        ) {
            // Get validator information
            (
                bytes memory _pubKey,
                bytes memory _withdrawalCredentials,
                bytes memory _signature,
                bytes32 _depositDataRoot,
                address _receiver
            ) = _initializedValidators.getNext(withdrawalCredentials);

            // Make sure the validator hasn't been deposited into already
            // to prevent sending an extra eth equal to `_remainingdepositAmount`
            // until withdrawals are allowed
            if (status[_pubKey] != DataTypes.ValidatorStatus.None)
                revert Errors.NoUsedValidator();

            (bool success, ) = beaconChainDepositContract.call{
                value: _remainingdepositAmount
            }(
                abi.encodeCall(
                    IDepositContract.deposit,
                    (
                        _pubKey,
                        _withdrawalCredentials,
                        _signature,
                        _depositDataRoot
                    )
                )
            );

            assert(success);

            pendingDeposit -= _remainingdepositAmount;

            if (preDepositAmount != 0) {
                _mintPxEth(_receiver, preDepositAmount);
            }

            unchecked {
                --remainingCount;
            }

            status[_pubKey] = DataTypes.ValidatorStatus.Staking;

            _stakingValidators.add(
                DataTypes.Validator(
                    _pubKey,
                    _signature,
                    _depositDataRoot,
                    _receiver
                ),
                _withdrawalCredentials
            );

            emit ValidatorDeposit(_pubKey);
        }
    }

    /**
     * @dev   Adds the specified amount to the pending deposit, considering the available buffer space and deposit pause status.
     *        If the buffer space is available, it may be fully or partially utilized. The method then checks if depositing
     *        ETH is not paused and spins up a validator if conditions are met.
     * @param _amount  uint256  The amount of ETH to be added to the pending deposit.
     */
    function _addPendingDeposit(uint256 _amount) internal virtual {
        uint256 _remainingBufferSpace = (
            maxBufferSize > buffer ? maxBufferSize - buffer : 0
        );
        uint256 _remainingAmount = _amount;

        if (_remainingBufferSpace != 0) {
            bool _canBufferSpaceFullyUtilized = _remainingBufferSpace <=
                _remainingAmount;
            buffer += _canBufferSpaceFullyUtilized
                ? _remainingBufferSpace
                : _remainingAmount;
            _remainingAmount -= _canBufferSpaceFullyUtilized
                ? _remainingBufferSpace
                : _remainingAmount;
        }

        pendingDeposit += _remainingAmount;

        if (depositEtherPaused == _NOT_PAUSED) {
            // Spin up a validator when possible
            _deposit();
        }
    }

    /**
     * @dev   Initiates the redemption process by adding the specified amount of pxETH to the pending withdrawal.
     *        Iteratively processes pending withdrawals in multiples of DEPOSIT_SIZE, triggering validator exits, updating
     *        batch information, and changing validator statuses accordingly. The process continues until the remaining
     *        pending withdrawal is less than DEPOSIT_SIZE. If `_shouldTriggerValidatorExit` is true and there's remaining
     *        pxETH after the redemption process, the function reverts, preventing partial initiation of redemption.
     * @param _pxEthAmount                 uint256  The amount of pxETH to be redeemed.
     * @param _receiver                    address  The receiver address for upxETH.
     * @param _shouldTriggerValidatorExit  bool     Whether to initiate partial redemption with a validator exit or not.
     */
    function _initiateRedemption(
        uint256 _pxEthAmount,
        address _receiver,
        bool _shouldTriggerValidatorExit
    ) internal {
        pendingWithdrawal += _pxEthAmount;

        while (pendingWithdrawal / DEPOSIT_SIZE != 0) {
            uint256 _allocationPossible = DEPOSIT_SIZE +
                _pxEthAmount -
                pendingWithdrawal;

            upxEth.mint(_receiver, batchId, _allocationPossible, "");

            (bytes memory _pubKey, , , , ) = _stakingValidators.getNext(
                withdrawalCredentials
            );

            pendingWithdrawal -= DEPOSIT_SIZE;
            _pxEthAmount -= _allocationPossible;

            oracleAdapter.requestVoluntaryExit(_pubKey);

            batchIdToValidator[batchId++] = _pubKey;
            status[_pubKey] = DataTypes.ValidatorStatus.Withdrawable;
        }

        if (_shouldTriggerValidatorExit && _pxEthAmount > 0)
            revert Errors.NoPartialInitiateRedemption();

        if (_pxEthAmount > 0) {
            upxEth.mint(_receiver, batchId, _pxEthAmount, "");
        }
    }

    /**
     * @dev   Checks if the contract has enough buffer to cover the specified amount. Iterates through the provided
     *        `_burnerAccounts`, verifies each account's approval status, burns the corresponding amount of pxETH, and
     *        updates the buffer accordingly. Reverts if there is insufficient buffer, if an account is not approved, or
     *        if the sum of burned amounts does not match the specified amount.
     * @param _amount          uint256                    The amount to be updated in the buffer.
     * @param _burnerAccounts  DataTypes.BurnerAccount[]  An array of burner account details (account and amount).
     */
    function _updateBuffer(
        uint256 _amount,
        DataTypes.BurnerAccount[] calldata _burnerAccounts
    ) private {
        if (buffer < _amount) {
            revert Errors.NotEnoughBuffer();
        }
        uint256 _len = _burnerAccounts.length;
        uint256 _sum;

        for (uint256 _i; _i < _len; ) {
            if (!burnerAccounts[_burnerAccounts[_i].account])
                revert Errors.AccountNotApproved();

            _sum += _burnerAccounts[_i].amount;

            _burnPxEth(_burnerAccounts[_i].account, _burnerAccounts[_i].amount);

            unchecked {
                ++_i;
            }
        }

        assert(_sum == _amount);
        buffer -= _amount;
    }
}