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 v5.4.0) (interfaces/IERC1363.sol)

pragma solidity >=0.6.2;

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 v5.4.0) (interfaces/IERC165.sol)

pragma solidity >=0.4.16;

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

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.4.0) (interfaces/IERC20.sol)

pragma solidity >=0.4.16;

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

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.4.0) (token/ERC20/IERC20.sol)

pragma solidity >=0.4.16;

/**
 * @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 v5.4.0) (utils/introspection/IERC165.sol)

pragma solidity >=0.4.16;

/**
 * @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 v5.3.0) (utils/Pausable.sol)

pragma solidity ^0.8.20;

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

/**
 * @dev Contract module which allows children to implement an emergency stop
 * mechanism that can be triggered by an authorized account.
 *
 * This module is used through inheritance. It will make available the
 * modifiers `whenNotPaused` and `whenPaused`, which can be applied to
 * the functions of your contract. Note that they will not be pausable by
 * simply including this module, only once the modifiers are put in place.
 */
abstract contract Pausable is Context {
    bool private _paused;

    /**
     * @dev Emitted when the pause is triggered by `account`.
     */
    event Paused(address account);

    /**
     * @dev Emitted when the pause is lifted by `account`.
     */
    event Unpaused(address account);

    /**
     * @dev The operation failed because the contract is paused.
     */
    error EnforcedPause();

    /**
     * @dev The operation failed because the contract is not paused.
     */
    error ExpectedPause();

    /**
     * @dev Modifier to make a function callable only when the contract is not paused.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    modifier whenNotPaused() {
        _requireNotPaused();
        _;
    }

    /**
     * @dev Modifier to make a function callable only when the contract is paused.
     *
     * Requirements:
     *
     * - The contract must be paused.
     */
    modifier whenPaused() {
        _requirePaused();
        _;
    }

    /**
     * @dev Returns true if the contract is paused, and false otherwise.
     */
    function paused() public view virtual returns (bool) {
        return _paused;
    }

    /**
     * @dev Throws if the contract is paused.
     */
    function _requireNotPaused() internal view virtual {
        if (paused()) {
            revert EnforcedPause();
        }
    }

    /**
     * @dev Throws if the contract is not paused.
     */
    function _requirePaused() internal view virtual {
        if (!paused()) {
            revert ExpectedPause();
        }
    }

    /**
     * @dev Triggers stopped state.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    function _pause() internal virtual whenNotPaused {
        _paused = true;
        emit Paused(_msgSender());
    }

    /**
     * @dev Returns to normal state.
     *
     * Requirements:
     *
     * - The contract must be paused.
     */
    function _unpause() internal virtual whenPaused {
        _paused = false;
        emit Unpaused(_msgSender());
    }
}

// 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: MIT
pragma solidity ^0.8.28;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/utils/ReentrancyGuard.sol";
import "@openzeppelin/contracts/utils/Pausable.sol";

/**
 * @notice Interface for Membership contract
 */
interface IMembership {
    function getUserTier(address user) external view returns (uint8);
}

/**
 * @notice Custom errors for gas optimization
 */
error InvalidTokenAddress();
error TransferFeeNotSupported();
error CannotStakeZero();
error CannotWithdrawZero();
error InsufficientStake();
error RewardMustBePositive();
error RewardRateTooLow();
error InsufficientBalanceForRewards();
error PeriodNotFinished();
error DurationMustBePositive();
error DurationTooLong();
error InvalidTier();
error InvalidMultiplierRange();
error InvalidRecipient();
error AmountMustBePositive();
error CannotSweepLockedTokens();

/**
 * @title MAIVStaking
 * @notice Flexible staking with tier-based reward multipliers
 * @dev Synthetix-style reward distribution with automatic membership tier integration
 *
 * Key Features:
 * - No lock periods - stake and withdraw anytime
 * - Linear reward distribution over admin-configured duration
 * - Tier multipliers: 1x (none), 1.25x (T1), 1.5x (T2), 2x (T3)
 * - Automatic tier sync when membership changes
 * - Fair expiration handling - no boosted rewards after membership expires
 */
contract MAIVStaking is Ownable, ReentrancyGuard, Pausable {
    using SafeERC20 for IERC20;

    IERC20 public immutable maivToken;
    IMembership public membershipContract;

    uint256 public periodFinish;
    uint256 public rewardRate;
    uint256 public rewardDuration = 30 days;
    uint256 public lastUpdateTime;
    uint256 public rewardPerTokenStored;

    uint256 public totalFlexStaked;
    uint256 public totalEffectiveStaked;  // Adjusted for multipliers

    mapping(address => uint256) public flexStakes;
    mapping(address => uint256) public userEffectiveStake;  // Snapshot: prevents retroactive multiplier exploit
    mapping(address => uint256) public userRewardPerTokenPaid;
    mapping(address => uint256) public rewards;

    // Tier multiplier settings (in basis points: 100 = 1x, 150 = 1.5x, 200 = 2x)
    bool public tierMultipliersEnabled;
    mapping(uint8 => uint256) public tierMultipliers;  // tier => multiplier in basis points

    event FlexStaked(address indexed user, uint256 amount, uint256 effectiveAmount);
    event FlexWithdrawn(address indexed user, uint256 amount, uint256 effectiveAmount);
    event RewardPaid(address indexed user, uint256 reward);
    event RewardAdded(uint256 reward, uint256 duration);
    event RewardDurationUpdated(uint256 newDuration);
    event MembershipContractUpdated(address indexed newMembership);
    event TierMultipliersToggled(bool enabled);
    event TierMultiplierUpdated(uint8 indexed tier, uint256 multiplier);

    constructor(address _maivToken, address _membershipContract) Ownable(msg.sender) {
        if (_maivToken == address(0)) revert InvalidTokenAddress();
        maivToken = IERC20(_maivToken);
        membershipContract = IMembership(_membershipContract);

        // Default multipliers (in basis points)
        tierMultipliers[0] = 100;   // No tier: 1x
        tierMultipliers[1] = 125;   // Tier 1: 1.25x
        tierMultipliers[2] = 150;   // Tier 2: 1.5x
        tierMultipliers[3] = 200;   // Tier 3: 2x

        tierMultipliersEnabled = true;  // Enabled by default
    }

    /**
     * @dev Prevents fee-on-transfer token exploits by verifying exact amount received
     * @param token The ERC20 token to transfer
     * @param from Address to transfer from
     * @param amount Expected amount to receive
     */
    function _pullExact(IERC20 token, address from, uint256 amount) internal {
        uint256 balanceBefore = token.balanceOf(address(this));
        token.safeTransferFrom(from, address(this), amount);
        uint256 received = token.balanceOf(address(this)) - balanceBefore;
        if (received != amount) revert TransferFeeNotSupported();
    }

    /**
     * @dev Updates global and user reward state, then auto-syncs tier if changed
     * @param account User address to update (address(0) for global only)
     */
    modifier updateReward(address account) {
        rewardPerTokenStored = rewardPerToken();
        lastUpdateTime = lastTimeRewardApplicable();

        if (account != address(0)) {
            rewards[account] = earned(account);
            userRewardPerTokenPaid[account] = rewardPerTokenStored;
            _autoSyncTierIfChanged(account);
        }
        _;
    }

    /**
     * @dev Auto-syncs tier multiplier if it changed (e.g. membership expired)
     * @param account User address to check and sync
     *
     * This function ensures fair rewards by:
     * - Checking if user's current tier differs from snapshotted tier
     * - Updating effective stake if tier changed
     * - Handling membership expiration automatically
     */
    function _autoSyncTierIfChanged(address account) internal {
        uint256 stakeAmount = flexStakes[account];
        if (stakeAmount == 0) return;

        uint256 currentEffectiveStake = getEffectiveStake(account, stakeAmount);
        uint256 snapshotEffectiveStake = userEffectiveStake[account];

        if (currentEffectiveStake != snapshotEffectiveStake) {
            totalEffectiveStaked = totalEffectiveStaked - snapshotEffectiveStake + currentEffectiveStake;
            userEffectiveStake[account] = currentEffectiveStake;

            if (currentEffectiveStake > snapshotEffectiveStake) {
                emit FlexStaked(account, 0, currentEffectiveStake - snapshotEffectiveStake);
            } else {
                emit FlexWithdrawn(account, 0, snapshotEffectiveStake - currentEffectiveStake);
            }
        }
    }

    /**
     * @notice Query user's current membership tier
     * @param user Address to check
     * @return tier 0 (none), 1, 2, or 3
     */
    function getUserTier(address user) public view returns (uint8) {
        if (address(membershipContract) == address(0) || !tierMultipliersEnabled) {
            return 0;
        }

        try membershipContract.getUserTier(user) returns (uint8 tier) {
            return tier;
        } catch {
            return 0;
        }
    }

    /**
     * @notice Calculate effective stake with current tier multiplier
     * @param user Address to calculate for
     * @param amount Actual staked amount
     * @return Effective amount after applying multiplier
     */
    function getEffectiveStake(address user, uint256 amount) public view returns (uint256) {
        if (!tierMultipliersEnabled || amount == 0) {
            return amount;
        }

        uint8 tier = getUserTier(user);
        uint256 multiplier = tierMultipliers[tier];

        return (amount * multiplier) / 100;
    }

    /**
     * @notice Get user's effective stake (convenience function)
     * @param user Address to query
     * @return User's current effective stake
     */
    function getEffectiveStakeForUser(address user) public view returns (uint256) {
        return getEffectiveStake(user, flexStakes[user]);
    }

    /**
     * @notice Get the last applicable reward time
     * @return Current time or period end, whichever is earlier
     */
    function lastTimeRewardApplicable() public view returns (uint256) {
        return block.timestamp < periodFinish ? block.timestamp : periodFinish;
    }

    /**
     * @notice Calculate accumulated reward per effective token
     * @return Reward per token (scaled by 1e18)
     */
    function rewardPerToken() public view returns (uint256) {
        if (totalEffectiveStaked == 0) {
            return rewardPerTokenStored;
        }

        return rewardPerTokenStored +
            ((lastTimeRewardApplicable() - lastUpdateTime) * rewardRate * 1e18) / totalEffectiveStaked;
    }

    /**
     * @notice Calculate user's earned rewards
     * @param account User address
     * @return Total earned rewards (claimable amount)
     *
     * @dev CRITICAL: Uses snapshot effective stake to ensure rewards are calculated
     * with the multiplier that was active during the earning period. This prevents:
     * - Gaming via tier upgrades (can't earn past rewards with new higher multiplier)
     * - Loss of earned rewards on membership expiry (preserves boosted rewards)
     * - The snapshot is updated via _autoSyncTierIfChanged() after rewards are calculated
     */
    function earned(address account) public view returns (uint256) {
        uint256 effectiveStake = userEffectiveStake[account];
        uint256 rewardDelta = rewardPerToken() - userRewardPerTokenPaid[account];
        return (effectiveStake * rewardDelta) / 1e18 + rewards[account];
    }

    /**
     * @notice Calculate current APR based on effective staking
     * @return APR in basis points (e.g., 5000 = 50% APR)
     *
     * @dev APR = (annualized rewards / total effective stake) * 10000
     * Returns 0 if no one is staking or reward period ended
     */
    function currentAPR() external view returns (uint256) {
        if (totalEffectiveStaked == 0 || block.timestamp >= periodFinish) {
            return 0;
        }

        uint256 remainingRewards = rewardRate * (periodFinish - block.timestamp);
        uint256 annualRewards = (remainingRewards * 365 days) / (periodFinish - block.timestamp);

        // APR relative to effective stake (accounts for multipliers)
        return (annualRewards * 10000) / totalEffectiveStaked;
    }

    /**
     * @notice Get remaining rewards for current period
     * @return Remaining reward tokens until periodFinish
     */
    function rewardForDuration() external view returns (uint256) {
        return rewardRate * (block.timestamp < periodFinish ? (periodFinish - block.timestamp) : 0);
    }

    /**
     * @notice Stake MAIV tokens to earn rewards
     * @param amount Amount of MAIV to stake
     *
     * @dev Applies current tier multiplier and updates effective stake.
     * No lock period - can withdraw anytime.
     */
    function stakeFlex(uint256 amount) external nonReentrant whenNotPaused updateReward(msg.sender) {
        if (amount == 0) revert CannotStakeZero();

        // Cache storage reads
        uint256 oldEffectiveStake = userEffectiveStake[msg.sender];
        uint256 currentStake = flexStakes[msg.sender];
        uint256 totalEffective = totalEffectiveStaked;
        uint256 totalFlex = totalFlexStaked;

        totalEffective -= oldEffectiveStake;

        uint256 newStake = currentStake + amount;
        flexStakes[msg.sender] = newStake;
        totalFlexStaked = totalFlex + amount;

        uint256 newEffectiveStake = getEffectiveStake(msg.sender, newStake);
        userEffectiveStake[msg.sender] = newEffectiveStake;
        totalEffectiveStaked = totalEffective + newEffectiveStake;

        _pullExact(maivToken, msg.sender, amount);

        emit FlexStaked(msg.sender, amount, newEffectiveStake - oldEffectiveStake);
    }

    /**
     * @dev Internal withdraw logic - called by withdrawFlex() and exit()
     * @param amount Amount to withdraw
     */
    function _withdrawFlex(uint256 amount) internal updateReward(msg.sender) {
        if (amount == 0) revert CannotWithdrawZero();

        // Cache storage reads
        uint256 currentStake = flexStakes[msg.sender];
        if (currentStake < amount) revert InsufficientStake();

        uint256 oldEffectiveStake = userEffectiveStake[msg.sender];
        uint256 totalEffective = totalEffectiveStaked;
        uint256 totalFlex = totalFlexStaked;

        totalEffective -= oldEffectiveStake;

        // Update stake amount
        uint256 newStake = currentStake - amount;
        flexStakes[msg.sender] = newStake;
        totalFlexStaked = totalFlex - amount;

        // Calculate and store new effective stake
        uint256 newEffectiveStake = getEffectiveStake(msg.sender, newStake);
        userEffectiveStake[msg.sender] = newEffectiveStake;
        totalEffectiveStaked = totalEffective + newEffectiveStake;

        maivToken.safeTransfer(msg.sender, amount);

        emit FlexWithdrawn(msg.sender, amount, oldEffectiveStake - newEffectiveStake);
    }

    /**
     * @notice Withdraw staked MAIV tokens
     * @param amount Amount to withdraw (must be <= staked balance)
     */
    function withdrawFlex(uint256 amount) public nonReentrant {
        _withdrawFlex(amount);
    }

    /**
     * @dev Internal claim logic - called by claimRewards() and exit()
     */
    function _claimRewards() internal updateReward(msg.sender) {
        uint256 reward = rewards[msg.sender];
        if (reward > 0) {
            rewards[msg.sender] = 0;
            maivToken.safeTransfer(msg.sender, reward);
            emit RewardPaid(msg.sender, reward);
        }
    }

    /**
     * @notice Claim earned rewards
     */
    function claimRewards() public nonReentrant {
        _claimRewards();
    }

    /**
     * @notice Withdraw all stake and claim rewards
     */
    function exit() external nonReentrant {
        _withdrawFlex(flexStakes[msg.sender]);
        _claimRewards();
    }

    /**
     * @notice Manually sync user's tier multiplier
     * @param user Address to sync
     *
     * @dev Called automatically by Membership contract when tier changes.
     * Can also be called manually if needed (permissionless).
     * Returns silently if user has no stake.
     */
    function syncTierMultiplierFor(address user) external nonReentrant updateReward(user) {
        // Cache storage reads
        uint256 stakeAmount = flexStakes[user];
        if (stakeAmount == 0) return;

        uint256 oldEffectiveStake = userEffectiveStake[user];
        uint256 totalEffective = totalEffectiveStaked;

        totalEffective -= oldEffectiveStake;

        uint256 newEffectiveStake = getEffectiveStake(user, stakeAmount);
        userEffectiveStake[user] = newEffectiveStake;
        totalEffectiveStaked = totalEffective + newEffectiveStake;

        if (newEffectiveStake > oldEffectiveStake) {
            emit FlexStaked(user, 0, newEffectiveStake - oldEffectiveStake);
        } else if (newEffectiveStake < oldEffectiveStake) {
            emit FlexWithdrawn(user, 0, oldEffectiveStake - newEffectiveStake);
        }
    }

    /**
     * @notice Fund reward pool for distribution
     * @param reward Amount of MAIV tokens to add to reward pool
     *
     * @dev Distributes linearly over rewardDuration (default 30 days).
     * If adding during active period, combines with remaining rewards.
     * Requires sufficient contract balance to cover distribution.
     */
    function topUpRewards(uint256 reward) external onlyOwner updateReward(address(0)) {
        if (reward == 0) revert RewardMustBePositive();

        // Cache storage reads
        uint256 currentTime = block.timestamp;
        uint256 periodEnd = periodFinish;
        uint256 duration = rewardDuration;
        uint256 rate = rewardRate;

        if (currentTime >= periodEnd) {
            // Starting new period
            rate = reward / duration;
        } else {
            // Adding to existing period
            uint256 remaining = periodEnd - currentTime;
            uint256 leftover = remaining * rate;
            rate = (reward + leftover) / duration;
        }

        if (rate == 0) revert RewardRateTooLow();

        rewardRate = rate;
        lastUpdateTime = currentTime;
        periodFinish = currentTime + duration;

        _pullExact(maivToken, msg.sender, reward);

        // Verify sufficient balance after transfer
        if (rate * duration > maivToken.balanceOf(address(this)) - totalFlexStaked) {
            revert InsufficientBalanceForRewards();
        }

        emit RewardAdded(reward, duration);
    }

    /**
     * @notice Set reward distribution duration
     * @param newDuration Duration in seconds (max 365 days)
     *
     * @dev Can only be changed when no active reward period.
     * Affects next topUpRewards() call.
     */
    function setRewardDuration(uint256 newDuration) external onlyOwner {
        if (block.timestamp < periodFinish) revert PeriodNotFinished();
        if (newDuration == 0) revert DurationMustBePositive();
        if (newDuration > 365 days) revert DurationTooLong();

        rewardDuration = newDuration;
        emit RewardDurationUpdated(newDuration);
    }

    /**
     * @notice Update Membership contract address
     * @param newMembershipContract Address of new Membership contract
     */
    function setMembershipContract(address newMembershipContract) external onlyOwner {
        membershipContract = IMembership(newMembershipContract);
        emit MembershipContractUpdated(newMembershipContract);
    }

    /**
     * @notice Enable or disable tier multiplier system
     * @param enabled True to enable multipliers, false for all 1x
     */
    function setTierMultipliersEnabled(bool enabled) external onlyOwner {
        tierMultipliersEnabled = enabled;
        emit TierMultipliersToggled(enabled);
    }

    /**
     * @notice Configure tier multiplier
     * @param tier Tier level (0=none, 1-3=tiers)
     * @param multiplier Basis points (100=1x, 125=1.25x, 150=1.5x, 200=2x)
     *
     * @dev Multiplier must be between 100 (1x) and 1000 (10x)
     */
    function setTierMultiplier(uint8 tier, uint256 multiplier) external onlyOwner {
        if (tier > 3) revert InvalidTier();
        if (multiplier < 100 || multiplier > 1000) revert InvalidMultiplierRange();

        tierMultipliers[tier] = multiplier;
        emit TierMultiplierUpdated(tier, multiplier);
    }

    /**
     * @notice Recover accidentally sent tokens
     * @param token Token address to recover
     * @param to Recipient address
     * @param amount Amount to recover
     *
     * @dev MAIV safety: Cannot sweep staked tokens or active reward pool
     */
    function sweepERC20(address token, address to, uint256 amount) external onlyOwner {
        if (to == address(0)) revert InvalidRecipient();
        if (amount == 0) revert AmountMustBePositive();

        if (token == address(maivToken)) {
            uint256 contractBalance = maivToken.balanceOf(address(this));
            uint256 remainingRewards = block.timestamp < periodFinish
                ? rewardRate * (periodFinish - block.timestamp)
                : 0;
            uint256 lockedAmount = totalFlexStaked + remainingRewards;
            uint256 sweepableAmount = contractBalance > lockedAmount ? contractBalance - lockedAmount : 0;

            if (amount > sweepableAmount) revert CannotSweepLockedTokens();
        }

        IERC20(token).safeTransfer(to, amount);
    }

    /**
     * @notice Get complete user staking info
     * @param user Address to query
     * @return staked Actual staked amount
     * @return effectiveStake Snapshot effective stake (with multiplier)
     * @return earnedRewards Current claimable rewards
     * @return membershipTier Current tier (0-3)
     * @return appliedMultiplier Current multiplier in basis points
     */
    function getUserInfo(address user) external view returns (
        uint256 staked,
        uint256 effectiveStake,
        uint256 earnedRewards,
        uint8 membershipTier,
        uint256 appliedMultiplier
    ) {
        staked = flexStakes[user];
        effectiveStake = userEffectiveStake[user];  // Use snapshot
        earnedRewards = earned(user);
        membershipTier = getUserTier(user);
        appliedMultiplier = tierMultipliersEnabled ? tierMultipliers[membershipTier] : 100;
    }

    function pause() external onlyOwner {
        _pause();
    }

    function unpause() external onlyOwner {
        _unpause();
    }
}