Cryo Explorer Ethereum Mainnet

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (access/Ownable.sol)

pragma solidity ^0.8.0;

import "../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.
 *
 * By default, the owner account will be the one that deploys the contract. 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;

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

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor() {
        _transferOwnership(_msgSender());
    }

    /**
     * @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 {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
    }

    /**
     * @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 {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        _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 v4.7.0) (security/Pausable.sol)

pragma solidity ^0.8.0;

import "../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 {
    /**
     * @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);

    bool private _paused;

    /**
     * @dev Initializes the contract in unpaused state.
     */
    constructor() {
        _paused = false;
    }

    /**
     * @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 {
        require(!paused(), "Pausable: paused");
    }

    /**
     * @dev Throws if the contract is not paused.
     */
    function _requirePaused() internal view virtual {
        require(paused(), "Pausable: not paused");
    }

    /**
     * @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 v4.9.0) (security/ReentrancyGuard.sol)

pragma solidity ^0.8.0;

/**
 * @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 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;

    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
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

        // 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
// OpenZeppelin Contracts (last updated v4.9.0) (token/ERC20/ERC20.sol)

pragma solidity ^0.8.0;

import "./IERC20.sol";
import "./extensions/IERC20Metadata.sol";
import "../../utils/Context.sol";

/**
 * @dev Implementation of the {IERC20} interface.
 *
 * This implementation is agnostic to the way tokens are created. This means
 * that a supply mechanism has to be added in a derived contract using {_mint}.
 * For a generic mechanism see {ERC20PresetMinterPauser}.
 *
 * TIP: For a detailed writeup see our guide
 * https://forum.openzeppelin.com/t/how-to-implement-erc20-supply-mechanisms/226[How
 * to implement supply mechanisms].
 *
 * The default value of {decimals} is 18. To change this, you should override
 * this function so it returns a different value.
 *
 * We have followed general OpenZeppelin Contracts guidelines: functions revert
 * instead returning `false` on failure. This behavior is nonetheless
 * conventional and does not conflict with the expectations of ERC20
 * applications.
 *
 * Additionally, an {Approval} event is emitted on calls to {transferFrom}.
 * This allows applications to reconstruct the allowance for all accounts just
 * by listening to said events. Other implementations of the EIP may not emit
 * these events, as it isn't required by the specification.
 *
 * Finally, the non-standard {decreaseAllowance} and {increaseAllowance}
 * functions have been added to mitigate the well-known issues around setting
 * allowances. See {IERC20-approve}.
 */
contract ERC20 is Context, IERC20, IERC20Metadata {
    mapping(address => uint256) private _balances;

    mapping(address => mapping(address => uint256)) private _allowances;

    uint256 private _totalSupply;

    string private _name;
    string private _symbol;

    /**
     * @dev Sets the values for {name} and {symbol}.
     *
     * All two of these values are immutable: they can only be set once during
     * construction.
     */
    constructor(string memory name_, string memory symbol_) {
        _name = name_;
        _symbol = symbol_;
    }

    /**
     * @dev Returns the name of the token.
     */
    function name() public view virtual override returns (string memory) {
        return _name;
    }

    /**
     * @dev Returns the symbol of the token, usually a shorter version of the
     * name.
     */
    function symbol() public view virtual override returns (string memory) {
        return _symbol;
    }

    /**
     * @dev Returns the number of decimals used to get its user representation.
     * For example, if `decimals` equals `2`, a balance of `505` tokens should
     * be displayed to a user as `5.05` (`505 / 10 ** 2`).
     *
     * Tokens usually opt for a value of 18, imitating the relationship between
     * Ether and Wei. This is the default value returned by this function, unless
     * it's overridden.
     *
     * NOTE: This information is only used for _display_ purposes: it in
     * no way affects any of the arithmetic of the contract, including
     * {IERC20-balanceOf} and {IERC20-transfer}.
     */
    function decimals() public view virtual override returns (uint8) {
        return 18;
    }

    /**
     * @dev See {IERC20-totalSupply}.
     */
    function totalSupply() public view virtual override returns (uint256) {
        return _totalSupply;
    }

    /**
     * @dev See {IERC20-balanceOf}.
     */
    function balanceOf(address account) public view virtual override returns (uint256) {
        return _balances[account];
    }

    /**
     * @dev See {IERC20-transfer}.
     *
     * Requirements:
     *
     * - `to` cannot be the zero address.
     * - the caller must have a balance of at least `amount`.
     */
    function transfer(address to, uint256 amount) public virtual override returns (bool) {
        address owner = _msgSender();
        _transfer(owner, to, amount);
        return true;
    }

    /**
     * @dev See {IERC20-allowance}.
     */
    function allowance(address owner, address spender) public view virtual override returns (uint256) {
        return _allowances[owner][spender];
    }

    /**
     * @dev See {IERC20-approve}.
     *
     * NOTE: If `amount` is the maximum `uint256`, the allowance is not updated on
     * `transferFrom`. This is semantically equivalent to an infinite approval.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 amount) public virtual override returns (bool) {
        address owner = _msgSender();
        _approve(owner, spender, amount);
        return true;
    }

    /**
     * @dev See {IERC20-transferFrom}.
     *
     * Emits an {Approval} event indicating the updated allowance. This is not
     * required by the EIP. See the note at the beginning of {ERC20}.
     *
     * NOTE: Does not update the allowance if the current allowance
     * is the maximum `uint256`.
     *
     * Requirements:
     *
     * - `from` and `to` cannot be the zero address.
     * - `from` must have a balance of at least `amount`.
     * - the caller must have allowance for ``from``'s tokens of at least
     * `amount`.
     */
    function transferFrom(address from, address to, uint256 amount) public virtual override returns (bool) {
        address spender = _msgSender();
        _spendAllowance(from, spender, amount);
        _transfer(from, to, amount);
        return true;
    }

    /**
     * @dev Atomically increases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {
        address owner = _msgSender();
        _approve(owner, spender, allowance(owner, spender) + addedValue);
        return true;
    }

    /**
     * @dev Atomically decreases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `spender` must have allowance for the caller of at least
     * `subtractedValue`.
     */
    function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {
        address owner = _msgSender();
        uint256 currentAllowance = allowance(owner, spender);
        require(currentAllowance >= subtractedValue, "ERC20: decreased allowance below zero");
        unchecked {
            _approve(owner, spender, currentAllowance - subtractedValue);
        }

        return true;
    }

    /**
     * @dev Moves `amount` of tokens from `from` to `to`.
     *
     * This internal function is equivalent to {transfer}, and can be used to
     * e.g. implement automatic token fees, slashing mechanisms, etc.
     *
     * Emits a {Transfer} event.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `from` must have a balance of at least `amount`.
     */
    function _transfer(address from, address to, uint256 amount) internal virtual {
        require(from != address(0), "ERC20: transfer from the zero address");
        require(to != address(0), "ERC20: transfer to the zero address");

        _beforeTokenTransfer(from, to, amount);

        uint256 fromBalance = _balances[from];
        require(fromBalance >= amount, "ERC20: transfer amount exceeds balance");
        unchecked {
            _balances[from] = fromBalance - amount;
            // Overflow not possible: the sum of all balances is capped by totalSupply, and the sum is preserved by
            // decrementing then incrementing.
            _balances[to] += amount;
        }

        emit Transfer(from, to, amount);

        _afterTokenTransfer(from, to, amount);
    }

    /** @dev Creates `amount` tokens and assigns them to `account`, increasing
     * the total supply.
     *
     * Emits a {Transfer} event with `from` set to the zero address.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     */
    function _mint(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: mint to the zero address");

        _beforeTokenTransfer(address(0), account, amount);

        _totalSupply += amount;
        unchecked {
            // Overflow not possible: balance + amount is at most totalSupply + amount, which is checked above.
            _balances[account] += amount;
        }
        emit Transfer(address(0), account, amount);

        _afterTokenTransfer(address(0), account, amount);
    }

    /**
     * @dev Destroys `amount` tokens from `account`, reducing the
     * total supply.
     *
     * Emits a {Transfer} event with `to` set to the zero address.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     * - `account` must have at least `amount` tokens.
     */
    function _burn(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: burn from the zero address");

        _beforeTokenTransfer(account, address(0), amount);

        uint256 accountBalance = _balances[account];
        require(accountBalance >= amount, "ERC20: burn amount exceeds balance");
        unchecked {
            _balances[account] = accountBalance - amount;
            // Overflow not possible: amount <= accountBalance <= totalSupply.
            _totalSupply -= amount;
        }

        emit Transfer(account, address(0), amount);

        _afterTokenTransfer(account, address(0), amount);
    }

    /**
     * @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens.
     *
     * This internal function is equivalent to `approve`, and can be used to
     * e.g. set automatic allowances for certain subsystems, etc.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `owner` cannot be the zero address.
     * - `spender` cannot be the zero address.
     */
    function _approve(address owner, address spender, uint256 amount) internal virtual {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");

        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }

    /**
     * @dev Updates `owner` s allowance for `spender` based on spent `amount`.
     *
     * Does not update the allowance amount in case of infinite allowance.
     * Revert if not enough allowance is available.
     *
     * Might emit an {Approval} event.
     */
    function _spendAllowance(address owner, address spender, uint256 amount) internal virtual {
        uint256 currentAllowance = allowance(owner, spender);
        if (currentAllowance != type(uint256).max) {
            require(currentAllowance >= amount, "ERC20: insufficient allowance");
            unchecked {
                _approve(owner, spender, currentAllowance - amount);
            }
        }
    }

    /**
     * @dev Hook that is called before any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * will be transferred to `to`.
     * - when `from` is zero, `amount` tokens will be minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens will be burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _beforeTokenTransfer(address from, address to, uint256 amount) internal virtual {}

    /**
     * @dev Hook that is called after any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * has been transferred to `to`.
     * - when `from` is zero, `amount` tokens have been minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens have been burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _afterTokenTransfer(address from, address to, uint256 amount) internal virtual {}
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (token/ERC20/IERC20.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
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 amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

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

    /**
     * @dev Moves `amount` 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 amount) 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 `amount` 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 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `from` to `to` using the
     * allowance mechanism. `amount` 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 amount) external returns (bool);
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (token/ERC20/extensions/ERC20Burnable.sol)

pragma solidity ^0.8.0;

import "../ERC20.sol";
import "../../../utils/Context.sol";

/**
 * @dev Extension of {ERC20} that allows token holders to destroy both their own
 * tokens and those that they have an allowance for, in a way that can be
 * recognized off-chain (via event analysis).
 */
abstract contract ERC20Burnable is Context, ERC20 {
    /**
     * @dev Destroys `amount` tokens from the caller.
     *
     * See {ERC20-_burn}.
     */
    function burn(uint256 amount) public virtual {
        _burn(_msgSender(), amount);
    }

    /**
     * @dev Destroys `amount` tokens from `account`, deducting from the caller's
     * allowance.
     *
     * See {ERC20-_burn} and {ERC20-allowance}.
     *
     * Requirements:
     *
     * - the caller must have allowance for ``accounts``'s tokens of at least
     * `amount`.
     */
    function burnFrom(address account, uint256 amount) public virtual {
        _spendAllowance(account, _msgSender(), amount);
        _burn(account, amount);
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/extensions/IERC20Metadata.sol)

pragma solidity ^0.8.0;

import "../IERC20.sol";

/**
 * @dev Interface for the optional metadata functions from the ERC20 standard.
 *
 * _Available since v4.1._
 */
interface IERC20Metadata is IERC20 {
    /**
     * @dev Returns the name of the token.
     */
    function name() external view returns (string memory);

    /**
     * @dev Returns the symbol of the token.
     */
    function symbol() external view returns (string memory);

    /**
     * @dev Returns the decimals places of the token.
     */
    function decimals() external view returns (uint8);
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.4) (utils/Context.sol)

pragma solidity ^0.8.0;

/**
 * @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 v4.9.0) (utils/math/SafeMath.sol)

pragma solidity ^0.8.0;

// CAUTION
// This version of SafeMath should only be used with Solidity 0.8 or later,
// because it relies on the compiler's built in overflow checks.

/**
 * @dev Wrappers over Solidity's arithmetic operations.
 *
 * NOTE: `SafeMath` is generally not needed starting with Solidity 0.8, since the compiler
 * now has built in overflow checking.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            uint256 c = a + b;
            if (c < a) return (false, 0);
            return (true, c);
        }
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            if (b > a) return (false, 0);
            return (true, a - b);
        }
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
            // benefit is lost if 'b' is also tested.
            // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
            if (a == 0) return (true, 0);
            uint256 c = a * b;
            if (c / a != b) return (false, 0);
            return (true, c);
        }
    }

    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            if (b == 0) return (false, 0);
            return (true, a / b);
        }
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            if (b == 0) return (false, 0);
            return (true, a % b);
        }
    }

    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        return a + b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return a - b;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        return a * b;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator.
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return a % b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        unchecked {
            require(b <= a, errorMessage);
            return a - b;
        }
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        unchecked {
            require(b > 0, errorMessage);
            return a / b;
        }
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        unchecked {
            require(b > 0, errorMessage);
            return a % b;
        }
    }
}

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.19;

import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import "@openzeppelin/contracts/token/ERC20/extensions/ERC20Burnable.sol";
import "@openzeppelin/contracts/security/ReentrancyGuard.sol";
import "@openzeppelin/contracts/security/Pausable.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/utils/math/SafeMath.sol";

/**
 * @title AuraL Token
 * @dev An ERC20 token with advanced features including:
 * - Buy-only mechanism (tokens can only be purchased, not transferred between users)
 * - Anti-bot measures
 * - Rate limiting
 * - Whitelist functionality
 * - Emergency pause
 * - Owner controls
 */
contract AuralToken is ERC20, ERC20Burnable, ReentrancyGuard, Pausable, Ownable {
    using SafeMath for uint256;
    
    // Token price in wei per token (1 token = 0.0001 ETH by default)
    uint256 public tokenPrice;
    
    // Maximum tokens that can be purchased in a single transaction
    uint256 public maxPurchaseAmount;
    
    // Minimum tokens that can be purchased in a single transaction
    uint256 public minPurchaseAmount;
    
    // Rate limiting: maximum purchases per address per day
    uint256 public maxDailyPurchases;
    
    // Mapping to track purchases per address per day
    mapping(address => mapping(uint256 => uint256)) private dailyPurchases;
    
    // Whitelist for addresses allowed to purchase during restricted periods
    mapping(address => bool) public whitelist;
    
    // Mapping to track last purchase time per address (anti-bot)
    mapping(address => uint256) private lastPurchaseTime;
    
    // Minimum time between purchases (anti-bot)
    uint256 public purchaseCooldown;
    
    // Treasury address for collecting fees
    address public treasury;
    
    // Purchase fee percentage (in basis points, e.g., 100 = 1%)
    uint256 public purchaseFee;
    
    // Maximum supply cap
    uint256 public maxSupply;
    
    // Current circulating supply
    uint256 private _circulatingSupply;
    
    // Events
    event TokensPurchased(address indexed buyer, uint256 ethAmount, uint256 tokenAmount, uint256 feeAmount);
    event TokenPriceUpdated(uint256 oldPrice, uint256 newPrice);
    event PurchaseLimitsUpdated(uint256 minAmount, uint256 maxAmount, uint256 dailyLimit);
    event AddressWhitelisted(address indexed account, bool status);
    event TreasuryUpdated(address indexed oldTreasury, address indexed newTreasury);
    event PurchaseFeeUpdated(uint256 oldFee, uint256 newFee);
    event PurchaseCooldownUpdated(uint256 oldCooldown, uint256 newCooldown);
    event MaxSupplyUpdated(uint256 oldMaxSupply, uint256 newMaxSupply);
    event TokensBurned(address indexed burner, uint256 amount);
    event TokensMinted(address indexed to, uint256 amount);
    event EthWithdrawn(address indexed to, uint256 amount);
    
    /**
     * @dev Constructor that initializes the token with name, symbol, and initial supply
     * @param initialSupply The initial token supply to mint to the contract creator
     * @param treasuryAddress The address to collect fees
     */
    constructor(
        uint256 initialSupply,
        address treasuryAddress
    ) ERC20("AuraL", "AURA") {
        require(treasuryAddress != address(0), "Treasury cannot be zero address");
        
        // Mint initial supply to the contract creator
        _mint(msg.sender, initialSupply);
        _circulatingSupply = initialSupply;
        
        // Set default token price (0.0001 ETH per token)
        tokenPrice = 100000000000000; // 0.0001 ETH in wei
        
        // Set default purchase limits
        minPurchaseAmount = 10 * 10**decimals(); // 10 tokens minimum
        maxPurchaseAmount = 200000 * 10**decimals(); // 200,000 tokens maximum
        maxDailyPurchases = 500000 * 10**decimals(); // 500,000 tokens per day
        
        // Set default anti-bot measures
        purchaseCooldown = 1 minutes; // 1 minute between purchases
        
        // Set default fee
        purchaseFee = 200; // 2% fee (200 basis points)
        
        // Set treasury
        treasury = treasuryAddress;
        
        // Set max supply (100 million tokens)
        maxSupply = 100000000 * 10**decimals();
        
        // Add contract creator to whitelist
        whitelist[msg.sender] = true;
    }
    
    /**
     * @dev Allows users to buy tokens by sending ETH to the contract
     * Implements security measures including reentrancy protection and rate limiting
     */
    function buy() public payable nonReentrant whenNotPaused {
        require(msg.value > 0, "Must send ETH to buy tokens");
        require(block.timestamp > lastPurchaseTime[msg.sender].add(purchaseCooldown) || whitelist[msg.sender], "Purchase too soon after last one");
        
        // Calculate token amount based on ETH sent
        uint256 tokenAmount = (msg.value.mul(10**decimals())).div(tokenPrice);
        
        // Enforce purchase limits
        require(tokenAmount >= minPurchaseAmount, "Purchase below minimum amount");
        require(tokenAmount <= maxPurchaseAmount, "Purchase exceeds maximum amount");
        
        // Enforce daily purchase limits
        uint256 today = block.timestamp / 1 days;
        uint256 userDailyTotal = dailyPurchases[msg.sender][today].add(tokenAmount);
        require(userDailyTotal <= maxDailyPurchases || whitelist[msg.sender], "Daily purchase limit exceeded");
        
        // Enforce max supply
        require(_circulatingSupply.add(tokenAmount) <= maxSupply, "Would exceed maximum supply");
        
        // Update tracking
        dailyPurchases[msg.sender][today] = userDailyTotal;
        lastPurchaseTime[msg.sender] = block.timestamp;
        
        // Calculate fee
        uint256 feeAmount = tokenAmount.mul(purchaseFee).div(10000);
        uint256 userAmount = tokenAmount.sub(feeAmount);
        
        // Mint tokens
        _mint(msg.sender, userAmount);
        if (feeAmount > 0) {
            _mint(treasury, feeAmount);
        }
        
        // Update circulating supply
        _circulatingSupply = _circulatingSupply.add(tokenAmount);
        
        // Emit event
        emit TokensPurchased(msg.sender, msg.value, userAmount, feeAmount);
    }
    
    /**
     * @dev Fallback function to allow buying tokens by sending ETH directly to the contract
     */
    receive() external payable {
        buy();
    }
    
    /**
     * @dev Overrides the transfer function to prevent transfers between users
     * Only the contract owner can transfer tokens (for administrative purposes)
     */
    function transfer(address to, uint256 amount) public override returns (bool) {
        require(msg.sender == owner() || whitelist[msg.sender], "Only owner or whitelisted addresses can transfer tokens");
        return super.transfer(to, amount);
    }
    
    /**
     * @dev Overrides the transferFrom function to prevent transfers between users
     * Only the contract owner can transfer tokens (for administrative purposes)
     */
    function transferFrom(address from, address to, uint256 amount) public override returns (bool) {
        require(msg.sender == owner() || whitelist[msg.sender], "Only owner or whitelisted addresses can transfer tokens");
        return super.transferFrom(from, to, amount);
    }
    
    /**
     * @dev Override the burn function to update circulating supply
     */
    function burn(uint256 amount) public override {
        super.burn(amount);
        _circulatingSupply = _circulatingSupply.sub(amount);
        emit TokensBurned(msg.sender, amount);
    }
    
    /**
     * @dev Override the burnFrom function to update circulating supply
     */
    function burnFrom(address account, uint256 amount) public override {
        super.burnFrom(account, amount);
        _circulatingSupply = _circulatingSupply.sub(amount);
        emit TokensBurned(account, amount);
    }
    
    /**
     * @dev Allows the owner to mint additional tokens
     * @param to The address to receive the tokens
     * @param amount The amount of tokens to mint
     */
    function mintTokens(address to, uint256 amount) external onlyOwner {
        require(to != address(0), "Cannot mint to zero address");
        require(_circulatingSupply.add(amount) <= maxSupply, "Would exceed maximum supply");
        
        _mint(to, amount);
        _circulatingSupply = _circulatingSupply.add(amount);
        
        emit TokensMinted(to, amount);
    }
    
    /**
     * @dev Allows the owner to update the token price
     * @param newPrice The new price in wei per token
     */
    function setTokenPrice(uint256 newPrice) external onlyOwner {
        require(newPrice > 0, "Price must be greater than zero");
        uint256 oldPrice = tokenPrice;
        tokenPrice = newPrice;
        emit TokenPriceUpdated(oldPrice, newPrice);
    }
    
    /**
     * @dev Allows the owner to update purchase limits
     * @param newMinAmount The new minimum purchase amount
     * @param newMaxAmount The new maximum purchase amount
     * @param newDailyLimit The new daily purchase limit
     */
    function setPurchaseLimits(
        uint256 newMinAmount,
        uint256 newMaxAmount,
        uint256 newDailyLimit
    ) external onlyOwner {
        require(newMinAmount > 0, "Minimum amount must be greater than zero");
        require(newMaxAmount >= newMinAmount, "Maximum amount must be greater than minimum");
        require(newDailyLimit >= newMaxAmount, "Daily limit must be greater than maximum amount");
        
        minPurchaseAmount = newMinAmount;
        maxPurchaseAmount = newMaxAmount;
        maxDailyPurchases = newDailyLimit;
        
        emit PurchaseLimitsUpdated(newMinAmount, newMaxAmount, newDailyLimit);
    }
    
    /**
     * @dev Allows the owner to update the purchase cooldown (anti-bot)
     * @param newCooldown The new cooldown period in seconds
     */
    function setPurchaseCooldown(uint256 newCooldown) external onlyOwner {
        uint256 oldCooldown = purchaseCooldown;
        purchaseCooldown = newCooldown;
        emit PurchaseCooldownUpdated(oldCooldown, newCooldown);
    }
    
    /**
     * @dev Allows the owner to update the purchase fee
     * @param newFee The new fee in basis points (e.g., 100 = 1%)
     */
    function setPurchaseFee(uint256 newFee) external onlyOwner {
        require(newFee <= 1000, "Fee cannot exceed 10%");
        uint256 oldFee = purchaseFee;
        purchaseFee = newFee;
        emit PurchaseFeeUpdated(oldFee, newFee);
    }
    
    /**
     * @dev Allows the owner to update the treasury address
     * @param newTreasury The new treasury address
     */
    function setTreasury(address newTreasury) external onlyOwner {
        require(newTreasury != address(0), "Treasury cannot be zero address");
        address oldTreasury = treasury;
        treasury = newTreasury;
        emit TreasuryUpdated(oldTreasury, newTreasury);
    }
    
    /**
     * @dev Allows the owner to update the maximum supply
     * @param newMaxSupply The new maximum supply
     */
    function setMaxSupply(uint256 newMaxSupply) external onlyOwner {
        require(newMaxSupply >= _circulatingSupply, "New max supply cannot be less than current circulating supply");
        uint256 oldMaxSupply = maxSupply;
        maxSupply = newMaxSupply;
        emit MaxSupplyUpdated(oldMaxSupply, newMaxSupply);
    }
    
    /**
     * @dev Allows the owner to add or remove addresses from the whitelist
     * @param account The address to update
     * @param status Whether the address should be whitelisted
     */
    function setWhitelistStatus(address account, bool status) external onlyOwner {
        whitelist[account] = status;
        emit AddressWhitelisted(account, status);
    }
    
    /**
     * @dev Allows the owner to pause token purchases
     */
    function pause() external onlyOwner {
        _pause();
    }
    
    /**
     * @dev Allows the owner to unpause token purchases
     */
    function unpause() external onlyOwner {
        _unpause();
    }
    
    /**
     * @dev Allows the owner to withdraw ETH from the contract
     * @param to The address to send ETH to
     * @param amount The amount of ETH to withdraw
     */
    function withdrawEth(address payable to, uint256 amount) external onlyOwner nonReentrant {
        require(to != address(0), "Cannot withdraw to zero address");
        require(amount <= address(this).balance, "Insufficient balance");
        
        (bool success, ) = to.call{value: amount}("");
        require(success, "ETH transfer failed");
        
        emit EthWithdrawn(to, amount);
    }
    
    /**
     * @dev Returns the token balance of an address
     * @param account The address to check
     * @return The token balance
     */
    function getBalance(address account) external view returns (uint256) {
        return balanceOf(account);
    }
    
    /**
     * @dev Returns the current ETH balance of the contract
     * @return The ETH balance
     */
    function getContractBalance() external view returns (uint256) {
        return address(this).balance;
    }
    
    /**
     * @dev Returns the current circulating supply
     * @return The circulating supply
     */
    function circulatingSupply() external view returns (uint256) {
        return _circulatingSupply;
    }
    
    /**
     * @dev Returns the number of tokens that can be purchased with a given amount of ETH
     * @param ethAmount The amount of ETH in wei
     * @return The number of tokens (before fees)
     */
    function getTokenAmount(uint256 ethAmount) external view returns (uint256) {
        return (ethAmount.mul(10**decimals())).div(tokenPrice);
    }
    
    /**
     * @dev Returns the amount of ETH needed to purchase a given number of tokens
     * @param tokenAmount The number of tokens
     * @return The amount of ETH in wei
     */
    function getEthAmount(uint256 tokenAmount) external view returns (uint256) {
        return (tokenAmount.mul(tokenPrice)).div(10**decimals());
    }
    
    /**
     * @dev Returns the remaining daily purchase limit for an address
     * @param account The address to check
     * @return The remaining daily purchase limit
     */
    function getRemainingDailyLimit(address account) external view returns (uint256) {
        if (whitelist[account]) {
            return type(uint256).max; // Whitelisted addresses have no limit
        }
        
        uint256 today = block.timestamp / 1 days;
        uint256 used = dailyPurchases[account][today];
        
        if (used >= maxDailyPurchases) {
            return 0;
        }
        
        return maxDailyPurchases.sub(used);
    }
    
    /**
     * @dev Returns the time remaining until the account can purchase again
     * @param account The address to check
     * @return The time remaining in seconds (0 if can purchase now)
     */
    function getCooldownRemaining(address account) external view returns (uint256) {
        if (whitelist[account]) {
            return 0; // Whitelisted addresses have no cooldown
        }
        
        uint256 lastPurchase = lastPurchaseTime[account];
        uint256 nextPurchaseTime = lastPurchase.add(purchaseCooldown);
        
        if (block.timestamp >= nextPurchaseTime) {
            return 0;
        }
        
        return nextPurchaseTime.sub(block.timestamp);
    }
}