Cryo Explorer Ethereum Mainnet

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.0.0) (access/Ownable.sol)

pragma solidity ^0.8.20;

import {Context} from "../utils/Context.sol";

/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * The initial owner is set to the address provided by the deployer. This can
 * later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
    address private _owner;

    /**
     * @dev The caller account is not authorized to perform an operation.
     */
    error OwnableUnauthorizedAccount(address account);

    /**
     * @dev The owner is not a valid owner account. (eg. `address(0)`)
     */
    error OwnableInvalidOwner(address owner);

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the address provided by the deployer as the initial owner.
     */
    constructor(address initialOwner) {
        if (initialOwner == address(0)) {
            revert OwnableInvalidOwner(address(0));
        }
        _transferOwnership(initialOwner);
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        _checkOwner();
        _;
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if the sender is not the owner.
     */
    function _checkOwner() internal view virtual {
        if (owner() != _msgSender()) {
            revert OwnableUnauthorizedAccount(_msgSender());
        }
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby disabling any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        _transferOwnership(address(0));
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        if (newOwner == address(0)) {
            revert OwnableInvalidOwner(address(0));
        }
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.1.0) (access/Ownable2Step.sol)

pragma solidity ^0.8.20;

import {Ownable} from "./Ownable.sol";

/**
 * @dev Contract module which provides access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * This extension of the {Ownable} contract includes a two-step mechanism to transfer
 * ownership, where the new owner must call {acceptOwnership} in order to replace the
 * old one. This can help prevent common mistakes, such as transfers of ownership to
 * incorrect accounts, or to contracts that are unable to interact with the
 * permission system.
 *
 * The initial owner is specified at deployment time in the constructor for `Ownable`. This
 * can later be changed with {transferOwnership} and {acceptOwnership}.
 *
 * This module is used through inheritance. It will make available all functions
 * from parent (Ownable).
 */
abstract contract Ownable2Step is Ownable {
    address private _pendingOwner;

    event OwnershipTransferStarted(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Returns the address of the pending owner.
     */
    function pendingOwner() public view virtual returns (address) {
        return _pendingOwner;
    }

    /**
     * @dev Starts the ownership transfer of the contract to a new account. Replaces the pending transfer if there is one.
     * Can only be called by the current owner.
     *
     * Setting `newOwner` to the zero address is allowed; this can be used to cancel an initiated ownership transfer.
     */
    function transferOwnership(address newOwner) public virtual override onlyOwner {
        _pendingOwner = newOwner;
        emit OwnershipTransferStarted(owner(), newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`) and deletes any pending owner.
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual override {
        delete _pendingOwner;
        super._transferOwnership(newOwner);
    }

    /**
     * @dev The new owner accepts the ownership transfer.
     */
    function acceptOwnership() public virtual {
        address sender = _msgSender();
        if (pendingOwner() != sender) {
            revert OwnableUnauthorizedAccount(sender);
        }
        _transferOwnership(sender);
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.1.0) (interfaces/IERC1363.sol)

pragma solidity ^0.8.20;

import {IERC20} from "./IERC20.sol";
import {IERC165} from "./IERC165.sol";

/**
 * @title IERC1363
 * @dev Interface of the ERC-1363 standard as defined in the https://eips.ethereum.org/EIPS/eip-1363[ERC-1363].
 *
 * Defines an extension interface for ERC-20 tokens that supports executing code on a recipient contract
 * after `transfer` or `transferFrom`, or code on a spender contract after `approve`, in a single transaction.
 */
interface IERC1363 is IERC20, IERC165 {
    /*
     * Note: the ERC-165 identifier for this interface is 0xb0202a11.
     * 0xb0202a11 ===
     *   bytes4(keccak256('transferAndCall(address,uint256)')) ^
     *   bytes4(keccak256('transferAndCall(address,uint256,bytes)')) ^
     *   bytes4(keccak256('transferFromAndCall(address,address,uint256)')) ^
     *   bytes4(keccak256('transferFromAndCall(address,address,uint256,bytes)')) ^
     *   bytes4(keccak256('approveAndCall(address,uint256)')) ^
     *   bytes4(keccak256('approveAndCall(address,uint256,bytes)'))
     */

    /**
     * @dev Moves a `value` amount of tokens from the caller's account to `to`
     * and then calls {IERC1363Receiver-onTransferReceived} on `to`.
     * @param to The address which you want to transfer to.
     * @param value The amount of tokens to be transferred.
     * @return A boolean value indicating whether the operation succeeded unless throwing.
     */
    function transferAndCall(address to, uint256 value) external returns (bool);

    /**
     * @dev Moves a `value` amount of tokens from the caller's account to `to`
     * and then calls {IERC1363Receiver-onTransferReceived} on `to`.
     * @param to The address which you want to transfer to.
     * @param value The amount of tokens to be transferred.
     * @param data Additional data with no specified format, sent in call to `to`.
     * @return A boolean value indicating whether the operation succeeded unless throwing.
     */
    function transferAndCall(address to, uint256 value, bytes calldata data) external returns (bool);

    /**
     * @dev Moves a `value` amount of tokens from `from` to `to` using the allowance mechanism
     * and then calls {IERC1363Receiver-onTransferReceived} on `to`.
     * @param from The address which you want to send tokens from.
     * @param to The address which you want to transfer to.
     * @param value The amount of tokens to be transferred.
     * @return A boolean value indicating whether the operation succeeded unless throwing.
     */
    function transferFromAndCall(address from, address to, uint256 value) external returns (bool);

    /**
     * @dev Moves a `value` amount of tokens from `from` to `to` using the allowance mechanism
     * and then calls {IERC1363Receiver-onTransferReceived} on `to`.
     * @param from The address which you want to send tokens from.
     * @param to The address which you want to transfer to.
     * @param value The amount of tokens to be transferred.
     * @param data Additional data with no specified format, sent in call to `to`.
     * @return A boolean value indicating whether the operation succeeded unless throwing.
     */
    function transferFromAndCall(address from, address to, uint256 value, bytes calldata data) external returns (bool);

    /**
     * @dev Sets a `value` amount of tokens as the allowance of `spender` over the
     * caller's tokens and then calls {IERC1363Spender-onApprovalReceived} on `spender`.
     * @param spender The address which will spend the funds.
     * @param value The amount of tokens to be spent.
     * @return A boolean value indicating whether the operation succeeded unless throwing.
     */
    function approveAndCall(address spender, uint256 value) external returns (bool);

    /**
     * @dev Sets a `value` amount of tokens as the allowance of `spender` over the
     * caller's tokens and then calls {IERC1363Spender-onApprovalReceived} on `spender`.
     * @param spender The address which will spend the funds.
     * @param value The amount of tokens to be spent.
     * @param data Additional data with no specified format, sent in call to `spender`.
     * @return A boolean value indicating whether the operation succeeded unless throwing.
     */
    function approveAndCall(address spender, uint256 value, bytes calldata data) external returns (bool);
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.0.0) (interfaces/IERC165.sol)

pragma solidity ^0.8.20;

import {IERC165} from "../utils/introspection/IERC165.sol";

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.0.0) (interfaces/IERC20.sol)

pragma solidity ^0.8.20;

import {IERC20} from "../token/ERC20/IERC20.sol";

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.1.0) (token/ERC20/IERC20.sol)

pragma solidity ^0.8.20;

/**
 * @dev Interface of the ERC-20 standard as defined in the ERC.
 */
interface IERC20 {
    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);

    /**
     * @dev Returns the value of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the value of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves a `value` amount of tokens from the caller's account to `to`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address to, uint256 value) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets a `value` amount of tokens as the allowance of `spender` over the
     * caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 value) external returns (bool);

    /**
     * @dev Moves a `value` amount of tokens from `from` to `to` using the
     * allowance mechanism. `value` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address from, address to, uint256 value) external returns (bool);
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.3.0) (token/ERC20/utils/SafeERC20.sol)

pragma solidity ^0.8.20;

import {IERC20} from "../IERC20.sol";
import {IERC1363} from "../../../interfaces/IERC1363.sol";

/**
 * @title SafeERC20
 * @dev Wrappers around ERC-20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
    /**
     * @dev An operation with an ERC-20 token failed.
     */
    error SafeERC20FailedOperation(address token);

    /**
     * @dev Indicates a failed `decreaseAllowance` request.
     */
    error SafeERC20FailedDecreaseAllowance(address spender, uint256 currentAllowance, uint256 requestedDecrease);

    /**
     * @dev Transfer `value` amount of `token` from the calling contract to `to`. If `token` returns no value,
     * non-reverting calls are assumed to be successful.
     */
    function safeTransfer(IERC20 token, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeCall(token.transfer, (to, value)));
    }

    /**
     * @dev Transfer `value` amount of `token` from `from` to `to`, spending the approval given by `from` to the
     * calling contract. If `token` returns no value, non-reverting calls are assumed to be successful.
     */
    function safeTransferFrom(IERC20 token, address from, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeCall(token.transferFrom, (from, to, value)));
    }

    /**
     * @dev Variant of {safeTransfer} that returns a bool instead of reverting if the operation is not successful.
     */
    function trySafeTransfer(IERC20 token, address to, uint256 value) internal returns (bool) {
        return _callOptionalReturnBool(token, abi.encodeCall(token.transfer, (to, value)));
    }

    /**
     * @dev Variant of {safeTransferFrom} that returns a bool instead of reverting if the operation is not successful.
     */
    function trySafeTransferFrom(IERC20 token, address from, address to, uint256 value) internal returns (bool) {
        return _callOptionalReturnBool(token, abi.encodeCall(token.transferFrom, (from, to, value)));
    }

    /**
     * @dev Increase the calling contract's allowance toward `spender` by `value`. If `token` returns no value,
     * non-reverting calls are assumed to be successful.
     *
     * IMPORTANT: If the token implements ERC-7674 (ERC-20 with temporary allowance), and if the "client"
     * smart contract uses ERC-7674 to set temporary allowances, then the "client" smart contract should avoid using
     * this function. Performing a {safeIncreaseAllowance} or {safeDecreaseAllowance} operation on a token contract
     * that has a non-zero temporary allowance (for that particular owner-spender) will result in unexpected behavior.
     */
    function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 oldAllowance = token.allowance(address(this), spender);
        forceApprove(token, spender, oldAllowance + value);
    }

    /**
     * @dev Decrease the calling contract's allowance toward `spender` by `requestedDecrease`. If `token` returns no
     * value, non-reverting calls are assumed to be successful.
     *
     * IMPORTANT: If the token implements ERC-7674 (ERC-20 with temporary allowance), and if the "client"
     * smart contract uses ERC-7674 to set temporary allowances, then the "client" smart contract should avoid using
     * this function. Performing a {safeIncreaseAllowance} or {safeDecreaseAllowance} operation on a token contract
     * that has a non-zero temporary allowance (for that particular owner-spender) will result in unexpected behavior.
     */
    function safeDecreaseAllowance(IERC20 token, address spender, uint256 requestedDecrease) internal {
        unchecked {
            uint256 currentAllowance = token.allowance(address(this), spender);
            if (currentAllowance < requestedDecrease) {
                revert SafeERC20FailedDecreaseAllowance(spender, currentAllowance, requestedDecrease);
            }
            forceApprove(token, spender, currentAllowance - requestedDecrease);
        }
    }

    /**
     * @dev Set the calling contract's allowance toward `spender` to `value`. If `token` returns no value,
     * non-reverting calls are assumed to be successful. Meant to be used with tokens that require the approval
     * to be set to zero before setting it to a non-zero value, such as USDT.
     *
     * NOTE: If the token implements ERC-7674, this function will not modify any temporary allowance. This function
     * only sets the "standard" allowance. Any temporary allowance will remain active, in addition to the value being
     * set here.
     */
    function forceApprove(IERC20 token, address spender, uint256 value) internal {
        bytes memory approvalCall = abi.encodeCall(token.approve, (spender, value));

        if (!_callOptionalReturnBool(token, approvalCall)) {
            _callOptionalReturn(token, abi.encodeCall(token.approve, (spender, 0)));
            _callOptionalReturn(token, approvalCall);
        }
    }

    /**
     * @dev Performs an {ERC1363} transferAndCall, with a fallback to the simple {ERC20} transfer if the target has no
     * code. This can be used to implement an {ERC721}-like safe transfer that rely on {ERC1363} checks when
     * targeting contracts.
     *
     * Reverts if the returned value is other than `true`.
     */
    function transferAndCallRelaxed(IERC1363 token, address to, uint256 value, bytes memory data) internal {
        if (to.code.length == 0) {
            safeTransfer(token, to, value);
        } else if (!token.transferAndCall(to, value, data)) {
            revert SafeERC20FailedOperation(address(token));
        }
    }

    /**
     * @dev Performs an {ERC1363} transferFromAndCall, with a fallback to the simple {ERC20} transferFrom if the target
     * has no code. This can be used to implement an {ERC721}-like safe transfer that rely on {ERC1363} checks when
     * targeting contracts.
     *
     * Reverts if the returned value is other than `true`.
     */
    function transferFromAndCallRelaxed(
        IERC1363 token,
        address from,
        address to,
        uint256 value,
        bytes memory data
    ) internal {
        if (to.code.length == 0) {
            safeTransferFrom(token, from, to, value);
        } else if (!token.transferFromAndCall(from, to, value, data)) {
            revert SafeERC20FailedOperation(address(token));
        }
    }

    /**
     * @dev Performs an {ERC1363} approveAndCall, with a fallback to the simple {ERC20} approve if the target has no
     * code. This can be used to implement an {ERC721}-like safe transfer that rely on {ERC1363} checks when
     * targeting contracts.
     *
     * NOTE: When the recipient address (`to`) has no code (i.e. is an EOA), this function behaves as {forceApprove}.
     * Opposedly, when the recipient address (`to`) has code, this function only attempts to call {ERC1363-approveAndCall}
     * once without retrying, and relies on the returned value to be true.
     *
     * Reverts if the returned value is other than `true`.
     */
    function approveAndCallRelaxed(IERC1363 token, address to, uint256 value, bytes memory data) internal {
        if (to.code.length == 0) {
            forceApprove(token, to, value);
        } else if (!token.approveAndCall(to, value, data)) {
            revert SafeERC20FailedOperation(address(token));
        }
    }

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     *
     * This is a variant of {_callOptionalReturnBool} that reverts if call fails to meet the requirements.
     */
    function _callOptionalReturn(IERC20 token, bytes memory data) private {
        uint256 returnSize;
        uint256 returnValue;
        assembly ("memory-safe") {
            let success := call(gas(), token, 0, add(data, 0x20), mload(data), 0, 0x20)
            // bubble errors
            if iszero(success) {
                let ptr := mload(0x40)
                returndatacopy(ptr, 0, returndatasize())
                revert(ptr, returndatasize())
            }
            returnSize := returndatasize()
            returnValue := mload(0)
        }

        if (returnSize == 0 ? address(token).code.length == 0 : returnValue != 1) {
            revert SafeERC20FailedOperation(address(token));
        }
    }

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     *
     * This is a variant of {_callOptionalReturn} that silently catches all reverts and returns a bool instead.
     */
    function _callOptionalReturnBool(IERC20 token, bytes memory data) private returns (bool) {
        bool success;
        uint256 returnSize;
        uint256 returnValue;
        assembly ("memory-safe") {
            success := call(gas(), token, 0, add(data, 0x20), mload(data), 0, 0x20)
            returnSize := returndatasize()
            returnValue := mload(0)
        }
        return success && (returnSize == 0 ? address(token).code.length > 0 : returnValue == 1);
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.0.1) (utils/Context.sol)

pragma solidity ^0.8.20;

/**
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }

    function _contextSuffixLength() internal view virtual returns (uint256) {
        return 0;
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.1.0) (utils/introspection/IERC165.sol)

pragma solidity ^0.8.20;

/**
 * @dev Interface of the ERC-165 standard, as defined in the
 * https://eips.ethereum.org/EIPS/eip-165[ERC].
 *
 * Implementers can declare support of contract interfaces, which can then be
 * queried by others ({ERC165Checker}).
 *
 * For an implementation, see {ERC165}.
 */
interface IERC165 {
    /**
     * @dev Returns true if this contract implements the interface defined by
     * `interfaceId`. See the corresponding
     * https://eips.ethereum.org/EIPS/eip-165#how-interfaces-are-identified[ERC section]
     * to learn more about how these ids are created.
     *
     * This function call must use less than 30 000 gas.
     */
    function supportsInterface(bytes4 interfaceId) external view returns (bool);
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.1.0) (utils/ReentrancyGuard.sol)

pragma solidity ^0.8.20;

/**
 * @dev Contract module that helps prevent reentrant calls to a function.
 *
 * Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
 * available, which can be applied to functions to make sure there are no nested
 * (reentrant) calls to them.
 *
 * Note that because there is a single `nonReentrant` guard, functions marked as
 * `nonReentrant` may not call one another. This can be worked around by making
 * those functions `private`, and then adding `external` `nonReentrant` entry
 * points to them.
 *
 * TIP: If EIP-1153 (transient storage) is available on the chain you're deploying at,
 * consider using {ReentrancyGuardTransient} instead.
 *
 * TIP: If you would like to learn more about reentrancy and alternative ways
 * to protect against it, check out our blog post
 * https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
 */
abstract contract ReentrancyGuard {
    // Booleans are more expensive than uint256 or any type that takes up a full
    // word because each write operation emits an extra SLOAD to first read the
    // slot's contents, replace the bits taken up by the boolean, and then write
    // back. This is the compiler's defense against contract upgrades and
    // pointer aliasing, and it cannot be disabled.

    // The values being non-zero value makes deployment a bit more expensive,
    // but in exchange the refund on every call to nonReentrant will be lower in
    // amount. Since refunds are capped to a percentage of the total
    // transaction's gas, it is best to keep them low in cases like this one, to
    // increase the likelihood of the full refund coming into effect.
    uint256 private constant NOT_ENTERED = 1;
    uint256 private constant ENTERED = 2;

    uint256 private _status;

    /**
     * @dev Unauthorized reentrant call.
     */
    error ReentrancyGuardReentrantCall();

    constructor() {
        _status = NOT_ENTERED;
    }

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * Calling a `nonReentrant` function from another `nonReentrant`
     * function is not supported. It is possible to prevent this from happening
     * by making the `nonReentrant` function external, and making it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        _nonReentrantBefore();
        _;
        _nonReentrantAfter();
    }

    function _nonReentrantBefore() private {
        // On the first call to nonReentrant, _status will be NOT_ENTERED
        if (_status == ENTERED) {
            revert ReentrancyGuardReentrantCall();
        }

        // Any calls to nonReentrant after this point will fail
        _status = ENTERED;
    }

    function _nonReentrantAfter() private {
        // By storing the original value once again, a refund is triggered (see
        // https://eips.ethereum.org/EIPS/eip-2200)
        _status = NOT_ENTERED;
    }

    /**
     * @dev Returns true if the reentrancy guard is currently set to "entered", which indicates there is a
     * `nonReentrant` function in the call stack.
     */
    function _reentrancyGuardEntered() internal view returns (bool) {
        return _status == ENTERED;
    }
}

// SPDX-License-Identifier: None
pragma solidity 0.8.30;

import "@openzeppelin/contracts/access/Ownable2Step.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
import "@openzeppelin/contracts/utils/ReentrancyGuard.sol";
/**
 * @title FXIStaking
 * @notice A staking contract that allows users to stake FXI tokens and earn ETH rewards based on tiered staking durations.
 * @dev Implements a reward distribution mechanism using accumulated rewards per share for different time tiers.
 * Key mechanisms:
 * - Users stake FXI tokens to earn ETH rewards.
 * - Rewards are distributed proportionally based on staked amounts and time tiers (14, 35 or 70 days).
 * - Users also earn FXI rewards based on APY for their tier and stake duration.
 * - Rewards are calculated using an accumulated rewards per share mechanism specific to each tier for ETH.
 * - FXI rewards are calculated based on time-staked and an APY per tier.
 * - ETH rewards can be deposited by anyone and are distributed to stakers according to their tier's allocation.
 * - FXI rewards are transferred from a designated tokenVault.
 */
contract FXIStaking is Ownable2Step, ReentrancyGuard {
    using SafeERC20 for IERC20;

    // Enum to define staking tiers
    enum StakingTier {
        NONE,
        TIER_14_DAYS,
        TIER_35_DAYS,
        TIER_70_DAYS
    }

    struct UserInfo {
        uint256 stakedAmount;
        uint256 rewardDebt; // Reward debt specific to the user's current tier (for ETH rewards)
        uint256 claimableRewards; // Accumulated ETH rewards ready to be claimed
        uint256 claimedAmount; // Total ETH rewards claimed by the user (for analytics)
        uint256 claimableFxiRewards; // Accumulated FXI rewards ready to be claimed
        uint256 claimedFxiAmount; // Total FXI rewards claimed by the user
        uint256 lastFxiRewardUpdateTime; // Timestamp of the last FXI reward calculation update
        uint256 pendingUnstakeAmount; // Amount of tokens pending withdrawal
        uint256 lastUnstakeTime; // Timestamp of the last unstake action
        StakingTier currentTier; // Current staking tier of the user
        uint256 stakeUnlockTime; // Timestamp when the user's current stake can be withdrawn
    }

    mapping(address => UserInfo) public userInfo;

    // Per-tier state variables for ETH rewards
    mapping(StakingTier => uint256) public accRewardsPerShareTier;
    mapping(StakingTier => uint256) public totalStakedAmountTier;

    uint256 public totalStakedAmount; // Total FXI staked across all tiers
    uint256 public unallocatedETH; // ETH received when no stakers or specific tier has no stakers
    uint256 public ethDebt; // ETH owed back to the contract after emergency withdrawal
    uint256 public globalETHCollected; // Total ETH ever deposited for rewards

    IERC20 public immutable stakingToken;
    IERC20 public rewardToken; // The ERC20 token used for APY-based rewards (e.g., FXI or FXONE)
    address public tokenVault; // Address holding the rewardTokens, from which this contract can transferFrom

    // Tier configuration constants
    uint256 public constant TIER_14_DURATION_SECONDS = 14 days;
    uint256 public constant TIER_35_DURATION_SECONDS = 35 days;
    uint256 public constant TIER_70_DURATION_SECONDS = 70 days;

    // ETH Reward Tier Allocations
    uint256 public constant TIER_14_ALLOCATION_BPS = 500; // 5%
    uint256 public constant TIER_35_ALLOCATION_BPS = 1500; // 15%
    uint256 public constant TIER_70_ALLOCATION_BPS = 8000; // 80%
    uint256 public constant TOTAL_ALLOCATION_BPS = 10000; // 100%

    // FXI (or rewardToken) APY per Tier (Basis Points)
    uint256 public constant TIER_14_APY_BPS = 200; // 2.00%
    uint256 public constant TIER_35_APY_BPS = 1000; // 10.00%
    uint256 public constant TIER_70_APY_BPS = 1500; // 15.00%

    uint256 private constant SECONDS_IN_YEAR = 365 days;
    uint256 private constant REWARD_PRECISION = 1e24;

    event Stake(address indexed user, uint256 amount, StakingTier tier);
    event Unstake(address indexed user, uint256 amount);
    event Withdraw(address indexed user, uint256 amount);
    event Claim(address indexed user, uint256 amount); // For ETH rewards
    event ClaimFxiRewards(address indexed user, uint256 amount);
    event RewardTokenChanged(
        address indexed oldToken,
        address indexed newToken
    );
    event TokenVaultChanged(address indexed oldVault, address indexed newVault);
    event RestakeAtPeriodEnd(
        address indexed user,
        uint256 principalAmount,
        StakingTier newTier
    );
    event EmergencyWithdrawal(uint256 amount, uint256 ethDebt);
    event PoolRefreshed(uint256 amountDistributed);

    constructor(
        address _stakingToken,
        address _rewardToken,
        address _tokenVaultAddr
    ) Ownable(msg.sender) {
        if (_stakingToken == address(0))
            revert("Staking token cannot be zero address");
        if (_rewardToken == address(0))
            revert("Reward token cannot be zero address");
        if (_tokenVaultAddr == address(0))
            revert("Token vault cannot be zero address");

        stakingToken = IERC20(_stakingToken);
        rewardToken = IERC20(_rewardToken);
        tokenVault = _tokenVaultAddr;
    }

    /**
     * @notice Converts a day count (14, 35, 70) to its corresponding StakingTier enum.
     * @dev Reverts if the number of days is invalid.
     * @param _days The number of days for the staking tier.
     * @return The StakingTier enum value.
     */
    function _getStakingTierFromDays(
        uint8 _days
    ) internal pure returns (StakingTier) {
        if (_days == 14) {
            return StakingTier.TIER_14_DAYS;
        } else if (_days == 35) {
            return StakingTier.TIER_35_DAYS;
        } else if (_days == 70) {
            return StakingTier.TIER_70_DAYS;
        } else {
            revert("Invalid staking duration");
        }
    }

    /**
     * @notice Gets the duration in seconds for a given staking tier.
     * @param _tier The StakingTier enum value.
     * @return The duration in seconds.
     */
    function _getTierDurationInSeconds(
        StakingTier _tier
    ) internal pure returns (uint256) {
        if (_tier == StakingTier.TIER_14_DAYS) {
            return TIER_14_DURATION_SECONDS;
        } else if (_tier == StakingTier.TIER_35_DAYS) {
            return TIER_35_DURATION_SECONDS;
        } else if (_tier == StakingTier.TIER_70_DAYS) {
            return TIER_70_DURATION_SECONDS;
        } else {
            revert("Invalid tier for duration");
        }
    }

    /**
     * @notice Gets the APY in Basis Points (BPS) for a given staking tier for FXI rewards.
     * @param _tier The StakingTier enum value.
     * @return The APY in BPS.
     */
    function _getTierApyBps(StakingTier _tier) internal pure returns (uint256) {
        if (_tier == StakingTier.TIER_14_DAYS) {
            return TIER_14_APY_BPS;
        } else if (_tier == StakingTier.TIER_35_DAYS) {
            return TIER_35_APY_BPS;
        } else if (_tier == StakingTier.TIER_70_DAYS) {
            return TIER_70_APY_BPS;
        } else {
            revert("Invalid tier for APY");
        }
    }

    /**
     * @notice Internal function to calculate and update pending FXI rewards for a user.
     * @dev This should be called before any action that might change stake amount or tier, or before claiming.
     *      It updates user.claimableFxiRewards and user.lastFxiRewardUpdateTime.
     * @param _userAddr The address of the user.
     */
    function _updateFxiRewards(address _userAddr) internal {
        UserInfo storage user = userInfo[_userAddr];

        if (
            user.stakedAmount == 0 ||
            user.currentTier == StakingTier.NONE ||
            user.lastFxiRewardUpdateTime == 0
        ) {
            // No stake, no valid tier, or it's the very first moment of staking (timer not started)
            // If lastFxiRewardUpdateTime is already block.timestamp due to a previous call in the same tx, timeElapsed would be 0.
            if (user.stakedAmount > 0 && user.lastFxiRewardUpdateTime == 0) {
                // This handles the case where a user stakes for the first time.
                // The timer effectively starts "now" for future calculations.
                user.lastFxiRewardUpdateTime = block.timestamp;
            }
            return;
        }

        uint256 timeElapsed = block.timestamp - user.lastFxiRewardUpdateTime;
        if (timeElapsed == 0) {
            return; // No time passed, no new rewards
        }

        uint256 tierApyBps = _getTierApyBps(user.currentTier);
        // FXI Reward = (Staked Amount * APY_BPS * Time Elapsed) / (BPS_DENOMINATOR * SECONDS_IN_YEAR)
        uint256 fxiReward = (user.stakedAmount * tierApyBps * timeElapsed) /
            (10000 * SECONDS_IN_YEAR);

        if (fxiReward > 0) {
            user.claimableFxiRewards += fxiReward;
        }
        user.lastFxiRewardUpdateTime = block.timestamp; // Always update to current time after calculation
    }

    /**
     * @notice Internal function to calculate and update pending ETH rewards for a user.
     * @dev This should be called before any action that might change stake amount or tier.
     *      It updates user.claimableRewards.
     * @param _userAddr The address of the user.
     */
    function _crystallizeEthRewards(address _userAddr) internal {
        UserInfo storage user = userInfo[_userAddr];
        if (user.stakedAmount > 0) {
            uint256 pending = ((user.stakedAmount *
                accRewardsPerShareTier[user.currentTier]) / REWARD_PRECISION) -
                user.rewardDebt;
            if (pending > 0) {
                user.claimableRewards += pending;
            }
            // Reward debt is updated after this call in the calling function context
            // as it depends on whether the stake amount/tier changes.
        }
    }

    /**
     * @notice Allows users to stake FXI tokens into a specified tier.
     * @dev Handles new stakes, adding to existing stakes, and tier changes.
     *      If changing tiers or adding to a stake, pending ETH rewards from the old tier are crystallized.
     *      Pending FXI rewards up to this point are also calculated and banked.
     *      The entire stake (existing + new) is then moved to the new tier, and the lock-in period is reset.
     * @param _amount The amount of FXI tokens to add to the stake.
     * @param _days The staking duration tier chosen by the user (14, 35, or 70 days).
     */
    function stake(uint256 _amount, uint8 _days) external nonReentrant {
        UserInfo storage user = userInfo[msg.sender];
        if (_amount == 0) {
            revert("Cannot stake 0 tokens");
        }
        StakingTier newTier = _getStakingTierFromDays(_days);

        _updateFxiRewards(msg.sender); // Calculate and bank pending FXI rewards before state changes

        // 1. Crystallize ETH rewards and update totals if user is already staked
        if (user.stakedAmount > 0) {
            _crystallizeEthRewards(msg.sender);
            totalStakedAmountTier[user.currentTier] -= user.stakedAmount;
            totalStakedAmount -= user.stakedAmount;
        }

        // 3. Update user's total staked amount (state change before external call)
        user.stakedAmount += _amount;

        // 4. Update user's tier and lock time for the *entire* stake
        user.currentTier = newTier;
        user.stakeUnlockTime =
            block.timestamp +
            _getTierDurationInSeconds(newTier);

        // 5. Add the user's *total current* staked amount to the new tier's accounting
        totalStakedAmountTier[newTier] += user.stakedAmount;
        totalStakedAmount += user.stakedAmount;

        // 6. Update ETH reward debt for the new tier and total new stake
        user.rewardDebt =
            (user.stakedAmount * accRewardsPerShareTier[newTier]) /
            REWARD_PRECISION;

        // 7. Reset FXI reward timer for the new/updated stake
        user.lastFxiRewardUpdateTime = block.timestamp;

        // Perform the token transfer (interaction) last
        stakingToken.safeTransferFrom(msg.sender, address(this), _amount);

        emit Stake(msg.sender, _amount, newTier);
    }

    /**
     * @notice Initiates the unstaking process for FXI tokens.
     * @dev Moves a specified amount of tokens from active stake to pending unstake.
     *      Pending ETH rewards for the user's current tier are calculated and added to their claimable balance.
     *      Pending FXI rewards are also calculated and banked.
     * @param _amount The amount of FXI tokens to unstake.
     */
    function unstake(uint256 _amount) external nonReentrant {
        UserInfo storage user = userInfo[msg.sender];
        if (_amount == 0) {
            revert("Cannot unstake 0 tokens");
        }
        if (user.stakedAmount < _amount) {
            revert("Insufficient staked amount");
        }
        if (user.currentTier == StakingTier.NONE) {
            revert("User not in a valid staking tier");
        }

        _updateFxiRewards(msg.sender); // Calculate and bank pending FXI rewards
        _crystallizeEthRewards(msg.sender);

        user.stakedAmount -= _amount;
        user.lastUnstakeTime = block.timestamp;
        user.pendingUnstakeAmount += _amount;

        totalStakedAmountTier[user.currentTier] -= _amount;
        totalStakedAmount -= _amount;

        user.rewardDebt =
            (user.stakedAmount * accRewardsPerShareTier[user.currentTier]) /
            REWARD_PRECISION;

        // If user.stakedAmount becomes 0, future calls to _updateFxiRewards will correctly do nothing
        // until/unless they stake again. lastFxiRewardUpdateTime remains, but timeElapsed calculations
        // will be based on 0 stakedAmount if called directly, or _updateFxiRewards will return early.
        // Explicitly setting user.lastFxiRewardUpdateTime = 0 if stakedAmount is 0 might be an option,
        // but current _updateFxiRewards logic handles it.

        emit Unstake(msg.sender, _amount);
    }

    /**
     * @notice Allows users to cancel their unstake and restake their pending tokens.
     * @dev Moves tokens from pending unstake back to the user's current active staking tier.
     *      The lock-in period for the restaked amount is reset according to the tier's duration.
     *      Pending FXI rewards are calculated and banked before restaking.
     */
    function restakeTokens() external nonReentrant {
        UserInfo storage user = userInfo[msg.sender];
        uint256 amountToRestake = user.pendingUnstakeAmount;
        if (amountToRestake == 0) {
            revert("No pending unstake amount to restake");
        }

        _updateFxiRewards(msg.sender); // Calculate and bank pending FXI rewards
        _crystallizeEthRewards(msg.sender);

        user.pendingUnstakeAmount = 0;
        user.stakedAmount += amountToRestake;
        // By restaking, user recommits, so stakeUnlockTime is updated for the entire stake.
        user.stakeUnlockTime =
            block.timestamp +
            _getTierDurationInSeconds(user.currentTier);

        totalStakedAmountTier[user.currentTier] += amountToRestake;
        totalStakedAmount += amountToRestake;

        user.rewardDebt =
            (user.stakedAmount * accRewardsPerShareTier[user.currentTier]) /
            REWARD_PRECISION;
        user.lastFxiRewardUpdateTime = block.timestamp; // Reset FXI reward timer

        emit RestakeAtPeriodEnd(msg.sender, amountToRestake, user.currentTier);
    }

    /**
     * @notice Withdraws unstaked tokens after the stake unlock period.
     * @dev Transfers tokens from pendingUnstakeAmount to the user if stakeUnlockTime has passed.
     */
    function claimUnstakedToken() external nonReentrant {
        UserInfo storage user = userInfo[msg.sender];
        uint256 toWithdraw = user.pendingUnstakeAmount;
        if (toWithdraw == 0) {
            revert("No pending unstake amount to claim");
        }
        // Check against stakeUnlockTime, which was set when the stake (that these tokens originated from) was made/updated.
        if (block.timestamp < user.stakeUnlockTime) {
            revert("Stake lock-in period not yet passed");
        }
        user.pendingUnstakeAmount = 0;
        stakingToken.safeTransfer(msg.sender, toWithdraw);
        emit Withdraw(msg.sender, toWithdraw);
    }

    /**
     * @notice Claims accumulated ETH rewards.
     * @dev Calculates and transfers available ETH rewards to the user based on their current tier and stake.
     *      Also ensures FXI rewards are up-to-date before ETH claim.
     */
    function claimEthRewards() external nonReentrant {
        UserInfo storage user = userInfo[msg.sender];

        if (user.stakedAmount == 0 && user.claimableRewards == 0) {
            revert(
                "No ETH rewards to claim or no active stake for pending calculation"
            );
        }
        if (user.currentTier == StakingTier.NONE && user.stakedAmount > 0) {
            revert("User in invalid tier with active stake");
        }

        _crystallizeEthRewards(msg.sender); // This will add pending from active stake to user.claimableRewards
        uint256 totalClaimable = user.claimableRewards;

        if (totalClaimable == 0) {
            revert("No ETH rewards to claim");
        }

        if (user.stakedAmount > 0) {
            user.rewardDebt =
                (user.stakedAmount * accRewardsPerShareTier[user.currentTier]) /
                REWARD_PRECISION;
        }

        uint256 amountToDistribute = address(this).balance >= totalClaimable
            ? totalClaimable
            : address(this).balance;

        if (amountToDistribute == 0) {
            revert("No ETH available to claim");
        }

        (bool sent, ) = msg.sender.call{value: amountToDistribute}("");
        if (!sent) {
            revert("ETH transfer failed");
        }
        user.claimableRewards -= amountToDistribute;
        user.claimedAmount += amountToDistribute;
        emit Claim(msg.sender, amountToDistribute);
    }

    /**
     * @notice Claims accumulated FXI (or current rewardToken) rewards.
     * @dev Transfers available rewardToken rewards from the tokenVault to the user.
     */
    function claimFxiRewards() external nonReentrant {
        if (address(rewardToken) == address(0)) {
            revert("Reward token not set");
        }
        if (tokenVault == address(0)) {
            revert("Token vault not set");
        }

        _updateFxiRewards(msg.sender); // Calculate and bank all pending FXI rewards

        UserInfo storage user = userInfo[msg.sender];
        uint256 amountToClaim = user.claimableFxiRewards;

        if (amountToClaim == 0) {
            revert("No FXI rewards to claim");
        }

        user.claimableFxiRewards = 0;
        user.claimedFxiAmount += amountToClaim;

        // This contract needs approval from tokenVault to transfer 'amountToClaim' of rewardToken
        rewardToken.safeTransferFrom(tokenVault, msg.sender, amountToClaim);

        emit ClaimFxiRewards(msg.sender, amountToClaim);
    }

    /**
     * @notice Internal function to distribute ETH to tiers.
     * @dev Updates accRewardsPerShareTier for each tier with active stakers.
     *      Any amount that cannot be distributed to a tier (e.g., tier has no stakers)
     *      is added back to unallocatedETH.
     * @param _amountToDistribute The total ETH amount to be distributed among tiers.
     */
    function _distributeEth(uint256 _amountToDistribute) internal {
        if (_amountToDistribute == 0) {
            return;
        }
        if (totalStakedAmount == 0) {
            unallocatedETH += _amountToDistribute;
            return;
        }

        uint256 ethForTier14 = (_amountToDistribute * TIER_14_ALLOCATION_BPS) /
            TOTAL_ALLOCATION_BPS;
        uint256 ethForTier35 = (_amountToDistribute * TIER_35_ALLOCATION_BPS) /
            TOTAL_ALLOCATION_BPS;
        uint256 ethForTier70 = (_amountToDistribute * TIER_70_ALLOCATION_BPS) /
            TOTAL_ALLOCATION_BPS;

        uint256 distributedSum = 0;

        if (
            totalStakedAmountTier[StakingTier.TIER_14_DAYS] > 0 &&
            ethForTier14 > 0
        ) {
            accRewardsPerShareTier[StakingTier.TIER_14_DAYS] +=
                (ethForTier14 * REWARD_PRECISION) /
                totalStakedAmountTier[StakingTier.TIER_14_DAYS];
            distributedSum += ethForTier14;
        } else if (ethForTier14 > 0) {
            unallocatedETH += ethForTier14;
        }

        if (
            totalStakedAmountTier[StakingTier.TIER_35_DAYS] > 0 &&
            ethForTier35 > 0
        ) {
            accRewardsPerShareTier[StakingTier.TIER_35_DAYS] +=
                (ethForTier35 * REWARD_PRECISION) /
                totalStakedAmountTier[StakingTier.TIER_35_DAYS];
            distributedSum += ethForTier35;
        } else if (ethForTier35 > 0) {
            unallocatedETH += ethForTier35;
        }

        if (
            totalStakedAmountTier[StakingTier.TIER_70_DAYS] > 0 &&
            ethForTier70 > 0
        ) {
            accRewardsPerShareTier[StakingTier.TIER_70_DAYS] +=
                (ethForTier70 * REWARD_PRECISION) /
                totalStakedAmountTier[StakingTier.TIER_70_DAYS];
            distributedSum += ethForTier70;
        } else if (ethForTier70 > 0) {
            unallocatedETH += ethForTier70;
        }

        // Handle any dust from BPS calculations or if _amountToDistribute was not fully covered by tier allocations
        if (_amountToDistribute > distributedSum) {
            unallocatedETH += (_amountToDistribute - distributedSum);
        }
    }

    /**
     * @notice Distributes unallocated ETH rewards to stakers based on tier allocations.
     * @dev Only callable by contract owner.
     *      Updates accRewardsPerShareTier for each tier with active stakers.
     */
    function refreshPool() external onlyOwner {
        uint256 amountToDistribute = unallocatedETH;
        if (amountToDistribute == 0) {
            revert("No unallocated ETH to distribute");
        }
        if (totalStakedAmount == 0) {
            revert("No stakers in any tier to distribute rewards to");
        }

        unallocatedETH = 0; // Clear before distribution attempts
        _distributeEth(amountToDistribute);
        emit PoolRefreshed(amountToDistribute);
    }

    /**
     * @notice Receives ETH deposits for rewards and distributes them according to tier allocations.
     * @dev Handles ETH deposits, tracks depositors, and updates accRewardsPerShareTier.
     *      If a tier has no stakers, its allocated portion becomes unallocatedETH.
     *      Manages ethDebt for emergency withdrawals.
     */
    receive() external payable {
        uint256 amount = msg.value;
        if (amount == 0) {
            revert("Cannot deposit 0 ETH");
        }

        globalETHCollected += amount;

        uint256 effectiveAmount = amount;
        if (ethDebt > 0) {
            if (ethDebt >= effectiveAmount) {
                ethDebt -= effectiveAmount;
                effectiveAmount = 0;
            } else {
                effectiveAmount -= ethDebt;
                ethDebt = 0;
            }
        }

        if (effectiveAmount == 0) {
            // All deposited ETH went to repay ethDebt
            return;
        }
        _distributeEth(effectiveAmount);
    }

    /**
     * @notice Emergency function to withdraw all ETH from the contract balance.
     * @dev Only callable by contract owner. Tracks withdrawn amount as ethDebt.
     */
    function emergencyWithdrawUnclaimedRewards()
        external
        onlyOwner
        nonReentrant
    {
        uint256 amount = address(this).balance;
        if (amount == 0) {
            revert("No ETH in contract to withdraw");
        }
        (bool sent, ) = msg.sender.call{value: amount}("");
        if (!sent) {
            revert("ETH transfer failed during emergency withdrawal");
        }
        ethDebt += amount;
        emit EmergencyWithdrawal(amount, ethDebt);
    }

    /**
     * @notice Allows the owner to change the ERC20 token used for APY-based rewards.
     * @param _newRewardToken The address of the new reward token contract.
     */
    function setRewardToken(address _newRewardToken) external onlyOwner {
        if (_newRewardToken == address(0)) {
            revert("Cannot set reward token to zero address");
        }
        emit RewardTokenChanged(address(rewardToken), _newRewardToken);
        rewardToken = IERC20(_newRewardToken);
    }

    /**
     * @notice Allows the owner to change the address of the token vault.
     * @param _newTokenVault The address of the new token vault.
     */
    function setTokenVault(address _newTokenVault) external onlyOwner {
        if (_newTokenVault == address(0)) {
            revert("Cannot set token vault to zero address");
        }
        emit TokenVaultChanged(tokenVault, _newTokenVault);
        tokenVault = _newTokenVault;
    }

    /**
     * @notice Allows a user to restake their entire principal into a new (or same) tier after their current lock-in period has ended.
     * @dev This function will crystallize any pending ETH and FXI rewards before restaking the principal.
     *      The user's claimable ETH and FXI balances will be updated with these crystallized rewards.
     *      The principal amount is then moved to the specified new tier, and the lock-in period is reset.
     * @param _days The staking duration tier chosen by the user for the new staking period (14, 35, or 70 days).
     */
    function restakeAtPeriodEnd(uint8 _days) external {
        UserInfo storage user = userInfo[msg.sender];

        if (block.timestamp < user.stakeUnlockTime) {
            revert("Stake lock-in period not yet passed");
        }
        if (user.stakedAmount == 0) {
            revert("No amount currently staked to restake");
        }

        StakingTier newTier = _getStakingTierFromDays(_days);

        // 1. Crystallize FXI rewards
        _updateFxiRewards(msg.sender);

        _crystallizeEthRewards(msg.sender);
        // Temporarily remove from old tier's accounting. Will be added back to global and new tier.
        totalStakedAmountTier[user.currentTier] -= user.stakedAmount;
        totalStakedAmount -= user.stakedAmount;

        uint256 principalToRestake = user.stakedAmount; // This is the full staked principal

        // 3. Update user's tier and lock time for the *entire* principal
        user.currentTier = newTier;
        user.stakeUnlockTime =
            block.timestamp +
            _getTierDurationInSeconds(newTier);

        // 4. Add the user's principal to the new tier's accounting and global total
        totalStakedAmountTier[newTier] += principalToRestake;
        totalStakedAmount += principalToRestake; // Add back to global total

        // 5. Update ETH reward debt for the new tier and principal
        user.rewardDebt =
            (principalToRestake * accRewardsPerShareTier[newTier]) /
            REWARD_PRECISION;

        // 6. Reset FXI reward timer for the new staking period
        user.lastFxiRewardUpdateTime = block.timestamp;
        emit RestakeAtPeriodEnd(msg.sender, principalToRestake, newTier);
    }

    /**
     * @notice Calculates total claimable ETH rewards for a staker.
     * @param _staker Address of the staker.
     * @return Total claimable ETH rewards (already banked + pending from active stake).
     */
    function getClaimableRewards(
        address _staker
    ) external view returns (uint256) {
        UserInfo storage user = userInfo[_staker];
        uint256 pendingFromActiveStake = 0;
        if (user.stakedAmount > 0 && user.currentTier != StakingTier.NONE) {
            pendingFromActiveStake =
                ((user.stakedAmount *
                    accRewardsPerShareTier[user.currentTier]) /
                    REWARD_PRECISION) -
                user.rewardDebt;
        }
        return user.claimableRewards + pendingFromActiveStake;
    }

    /**
     * @notice Calculates total claimable FXI (or current rewardToken) rewards for a staker.
     * @dev This includes already banked rewards plus pending rewards from the current active stake.
     * @param _staker Address of the staker.
     * @return Total claimable FXI rewards.
     */
    function getClaimableFxiRewards(
        address _staker
    ) external view returns (uint256) {
        // Note: For view functions, we can't modify state (like user.lastFxiRewardUpdateTime).
        // So, we calculate pending without altering the stored lastFxiRewardUpdateTime.
        UserInfo storage user = userInfo[_staker]; // Use storage for direct access

        if (user.stakedAmount == 0 || user.currentTier == StakingTier.NONE) {
            // If no stake or no tier, only return already banked (crystallized) FXI rewards.
            // lastFxiRewardUpdateTime might be 0 if never staked or if fully unstaked and rewards claimed.
            return user.claimableFxiRewards;
        }

        // If lastFxiRewardUpdateTime is 0 but they have a stake (e.g., mid-transaction before it's set, or an edge case),
        // we should not calculate pending rewards based on a zero timestamp as that would be incorrect.
        // The _updateFxiRewards handles setting it correctly on first stake.
        // Here, if it's 0, it means no rewards have started accruing for the current period yet.
        if (
            user.lastFxiRewardUpdateTime == 0 ||
            user.lastFxiRewardUpdateTime >= block.timestamp
        ) {
            return user.claimableFxiRewards; // No time elapsed or timer not started for current period
        }

        uint256 timeElapsed = block.timestamp - user.lastFxiRewardUpdateTime;

        uint256 tierApyBps = _getTierApyBps(user.currentTier);
        uint256 pendingFxiReward = (user.stakedAmount *
            tierApyBps *
            timeElapsed) / (10000 * SECONDS_IN_YEAR);

        return user.claimableFxiRewards + pendingFxiReward;
    }

    /**
     * @notice Checks if unstaked tokens are available for withdrawal based on stakeUnlockTime.
     * @param _staker Address of the staker.
     * @return Amount of tokens in pendingUnstakeAmount if stakeUnlockTime has passed, otherwise 0.
     */
    function getClaimableUnstakedToken(
        address _staker
    ) external view returns (uint256) {
        UserInfo storage user = userInfo[_staker];
        if (
            user.pendingUnstakeAmount > 0 &&
            block.timestamp >= user.stakeUnlockTime
        ) {
            return user.pendingUnstakeAmount;
        } else {
            return 0;
        }
    }

    /**
     * @notice Returns amount of tokens currently in the pending unstake state for a staker.
     * @param _staker Address of the staker.
     * @return Amount of tokens pending unstake.
     */
    function getPendingUnstakeAmount(
        address _staker
    ) external view returns (uint256) {
        return userInfo[_staker].pendingUnstakeAmount;
    }

    /**
     * @notice Returns the total amount staked in a specific tier.
     * @param _tier The staking tier.
     * @return Total amount staked in that tier.
     */
    function getTotalStakedInTier(
        StakingTier _tier
    ) external view returns (uint256) {
        // Ensure _tier is a valid, active tier before accessing mapping
        if (_tier == StakingTier.NONE) return 0; // Or revert, depending on desired behavior
        return totalStakedAmountTier[_tier];
    }

    /**
     * @notice Returns the accumulated ETH rewards per share for a specific tier.
     * @param _tier The staking tier.
     * @return Accumulated ETH rewards per share for that tier (scaled by 1e24).
     */
    function getAccRewardsPerShareForTier(
        StakingTier _tier
    ) external view returns (uint256) {
        if (_tier == StakingTier.NONE) return 0;
        return accRewardsPerShareTier[_tier];
    }

    /**
     * @notice Returns the current staking tier for a user.
     * @param _staker Address of the staker.
     * @return The StakingTier enum value.
     */
    function getUserTier(address _staker) external view returns (StakingTier) {
        return userInfo[_staker].currentTier;
    }

    /**
     * @notice Returns the stake unlock time for a user.
     * @param _staker Address of the staker.
     * @return Timestamp when the user's stake can be withdrawn.
     */
    function getUserStakeUnlockTime(
        address _staker
    ) external view returns (uint256) {
        return userInfo[_staker].stakeUnlockTime;
    }

    /**
     * @notice Disables the ability to renounce ownership of the contract.
     * @dev Overrides OpenZeppelin's Ownable2Step renounceOwnership function to prevent accidental loss of contract control.
     *      This ensures the contract always has an owner who can perform administrative functions.
     */
    function renounceOwnership() public override onlyOwner {
        revert("Renouncing ownership is disabled.");
    }
}