Cryo Explorer Ethereum Mainnet

// SPDX-License-Identifier: GPL-3.0

pragma solidity 0.8.17;

import { ERC20 } from "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import { Ownable } from "@openzeppelin/contracts/access/Ownable.sol";
import { LibCommon } from "./lib/LibCommon.sol";

/// @title A Defi Token implementation with extended functionalities
/// @notice Implements ERC20 standards with additional features like tax and deflation
contract DefiToken is ERC20, Ownable {
  // Constants
  uint256 private constant MAX_BPS_AMOUNT = 10_000;
  uint256 private constant MAX_ALLOWED_BPS = 5_000;
  string public constant VERSION = "defi_v_1";

  // State Variables
  string public initialDocumentUri;
  string public documentUri;
  uint256 public immutable initialSupply;
  uint256 public immutable initialMaxTokenAmountPerAddress;
  uint256 public maxTokenAmountPerAddress;

  /// @notice Configuration properties for the ERC20 token
  struct ERC20ConfigProps {
    bool _isMintable;
    bool _isBurnable;
    bool _isDocumentAllowed;
    bool _isMaxAmountOfTokensSet;
    bool _isTaxable;
    bool _isDeflationary;
  }
  ERC20ConfigProps private configProps;

  address public immutable initialTokenOwner;
  uint8 private immutable _decimals;
  address public taxAddress;
  uint256 public taxBPS;
  uint256 public deflationBPS;

  // Events
  event DocumentUriSet(string newDocUri);
  event MaxTokenAmountPerSet(uint256 newMaxTokenAmount);
  event TaxConfigSet(address indexed _taxAddress, uint256 indexed _taxBPS);
  event DeflationConfigSet(uint256 indexed _deflationBPS);

  // Custom Errors
  error InvalidMaxTokenAmount(uint256 maxTokenAmount);
  error InvalidDecimals(uint8 decimals);
  error MaxTokenAmountPerAddrLtPrevious();
  error DestBalanceExceedsMaxAllowed(address addr);
  error MintingNotEnabled();
  error BurningNotEnabled();
  error DocumentUriNotAllowed();
  error MaxTokenAmountNotAllowed();
  error TokenIsNotTaxable();
  error TokenIsNotDeflationary();
  error InvalidTaxBPS(uint256 bps);
  error InvalidDeflationBPS(uint256 bps);

  /// @notice Constructor to initialize the DeFi token
  /// @param name_ Name of the token
  /// @param symbol_ Symbol of the token
  /// @param initialSupplyToSet Initial supply of tokens
  /// @param decimalsToSet Number of decimals for the token
  /// @param tokenOwner Address of the initial token owner
  /// @param customConfigProps Configuration properties for the token
  /// @param maxTokenAmount Maximum token amount per address
  /// @param newDocumentUri URI for the document associated with the token
  /// @param _taxAddress Address where tax will be sent
  /// @param _taxBPS Basis points for tax calculation
  /// @param _deflationBPS Basis points for deflation calculation
  constructor(
    string memory name_,
    string memory symbol_,
    uint256 initialSupplyToSet,
    uint8 decimalsToSet,
    address tokenOwner,
    ERC20ConfigProps memory customConfigProps,
    uint256 maxTokenAmount,
    string memory newDocumentUri,
    address _taxAddress,
    uint256 _taxBPS,
    uint256 _deflationBPS
  ) ERC20(name_, symbol_) {
    if (customConfigProps._isMaxAmountOfTokensSet) {
      if (maxTokenAmount == 0) {
        revert InvalidMaxTokenAmount(maxTokenAmount);
      }
    }
    if (decimalsToSet > 18) {
      revert InvalidDecimals(decimalsToSet);
    }
    if (customConfigProps._isTaxable) {
      if (_taxBPS > MAX_ALLOWED_BPS) {
        revert InvalidTaxBPS(_taxBPS);
      }
      LibCommon.validateAddress(_taxAddress);
      taxAddress = _taxAddress;
      taxBPS = _taxBPS;
    }
    if (customConfigProps._isDeflationary) {
      if (_deflationBPS > MAX_ALLOWED_BPS) {
        revert InvalidDeflationBPS(_deflationBPS);
      }
      deflationBPS = _deflationBPS;
    }
    LibCommon.validateAddress(tokenOwner);

    initialSupply = initialSupplyToSet;
    initialMaxTokenAmountPerAddress = maxTokenAmount;
    initialDocumentUri = newDocumentUri;
    initialTokenOwner = tokenOwner;
    _decimals = decimalsToSet;
    configProps = customConfigProps;
    documentUri = newDocumentUri;
    maxTokenAmountPerAddress = maxTokenAmount;

    if (initialSupplyToSet != 0) {
      _mint(tokenOwner, initialSupplyToSet * 10 ** decimalsToSet);
    }

    if (tokenOwner != msg.sender) {
      transferOwnership(tokenOwner);
    }
  }

  // Public and External Functions

  /// @notice Checks if the token is mintable
  /// @return True if the token can be minted
  function isMintable() public view returns (bool) {
    return configProps._isMintable;
  }

  /// @notice Checks if the token is burnable
  /// @return True if the token can be burned
  function isBurnable() public view returns (bool) {
    return configProps._isBurnable;
  }

  /// @notice Checks if the maximum amount of tokens per address is set
  /// @return True if there is a maximum limit for token amount per address
  function isMaxAmountOfTokensSet() public view returns (bool) {
    return configProps._isMaxAmountOfTokensSet;
  }

  /// @notice Checks if setting a document URI is allowed
  /// @return True if setting a document URI is allowed
  function isDocumentUriAllowed() public view returns (bool) {
    return configProps._isDocumentAllowed;
  }

  /// @notice Returns the number of decimals used for the token
  /// @return The number of decimals
  function decimals() public view virtual override returns (uint8) {
    return _decimals;
  }

  /// @notice Checks if the token is taxable
  /// @return True if the token has tax applied on transfers
  function isTaxable() public view returns (bool) {
    return configProps._isTaxable;
  }

  /// @notice Checks if the token is deflationary
  /// @return True if the token has deflation applied on transfers
  function isDeflationary() public view returns (bool) {
    return configProps._isDeflationary;
  }

  /// @notice Sets a new document URI
  /// @dev Can only be called by the contract owner
  /// @param newDocumentUri The new URI to be set
  function setDocumentUri(string memory newDocumentUri) external onlyOwner {
    if (!isDocumentUriAllowed()) {
      revert DocumentUriNotAllowed();
    }
    documentUri = newDocumentUri;
    emit DocumentUriSet(newDocumentUri);
  }

  /// @notice Sets a new maximum token amount per address
  /// @dev Can only be called by the contract owner
  /// @param newMaxTokenAmount The new maximum token amount per address
  function setMaxTokenAmountPerAddress(
    uint256 newMaxTokenAmount
  ) external onlyOwner {
    if (!isMaxAmountOfTokensSet()) {
      revert MaxTokenAmountNotAllowed();
    }
    if (newMaxTokenAmount <= maxTokenAmountPerAddress) {
      revert MaxTokenAmountPerAddrLtPrevious();
    }

    maxTokenAmountPerAddress = newMaxTokenAmount;
    emit MaxTokenAmountPerSet(newMaxTokenAmount);
  }

  /// @notice Sets a new tax configuration
  /// @dev Can only be called by the contract owner
  /// @param _taxAddress The address where tax will be sent
  /// @param _taxBPS The tax rate in basis points
  function setTaxConfig(
    address _taxAddress,
    uint256 _taxBPS
  ) external onlyOwner {
    if (!isTaxable()) {
      revert TokenIsNotTaxable();
    }
    if (_taxBPS > MAX_ALLOWED_BPS) {
      revert InvalidTaxBPS(_taxBPS);
    }
    LibCommon.validateAddress(_taxAddress);
    taxAddress = _taxAddress;
    taxBPS = _taxBPS;
    emit TaxConfigSet(_taxAddress, _taxBPS);
  }

  /// @notice Sets a new deflation configuration
  /// @dev Can only be called by the contract owner
  /// @param _deflationBPS The deflation rate in basis points
  function setDeflationConfig(uint256 _deflationBPS) external onlyOwner {
    if (!isDeflationary()) {
      revert TokenIsNotDeflationary();
    }
    if (_deflationBPS > MAX_ALLOWED_BPS) {
      revert InvalidDeflationBPS(_deflationBPS);
    }
    deflationBPS = _deflationBPS;
    emit DeflationConfigSet(_deflationBPS);
  }

  /// @notice Transfers tokens to a specified address
  /// @dev Overrides the ERC20 transfer function with added tax and deflation logic
  /// @param to The address to transfer tokens to
  /// @param amount The amount of tokens to be transferred
  /// @return True if the transfer was successful
  function transfer(
    address to,
    uint256 amount
  ) public virtual override returns (bool) {
    uint256 taxAmount = _taxAmount(msg.sender, amount);
    uint256 deflationAmount = _deflationAmount(amount);
    uint256 amountToTransfer = amount - taxAmount - deflationAmount;

    if (isMaxAmountOfTokensSet()) {
      if (balanceOf(to) + amountToTransfer > maxTokenAmountPerAddress) {
        revert DestBalanceExceedsMaxAllowed(to);
      }
    }

    if (taxAmount != 0) {
      _transfer(msg.sender, taxAddress, taxAmount);
    }
    if (deflationAmount != 0) {
      _burn(msg.sender, deflationAmount);
    }
    return super.transfer(to, amountToTransfer);
  }

  /// @notice Transfers tokens from one address to another
  /// @dev Overrides the ERC20 transferFrom function with added tax and deflation logic
  /// @param from The address which you want to send tokens from
  /// @param to The address which you want to transfer to
  /// @param amount The amount of tokens to be transferred
  /// @return True if the transfer was successful
  function transferFrom(
    address from,
    address to,
    uint256 amount
  ) public virtual override returns (bool) {
    uint256 taxAmount = _taxAmount(from, amount);
    uint256 deflationAmount = _deflationAmount(amount);
    uint256 amountToTransfer = amount - taxAmount - deflationAmount;

    if (isMaxAmountOfTokensSet()) {
      if (balanceOf(to) + amountToTransfer > maxTokenAmountPerAddress) {
        revert DestBalanceExceedsMaxAllowed(to);
      }
    }

    if (taxAmount != 0) {
      _transfer(from, taxAddress, taxAmount);
    }
    if (deflationAmount != 0) {
      _burn(from, deflationAmount);
    }

    return super.transferFrom(from, to, amountToTransfer);
  }

  /// @notice Mints new tokens to a specified address
  /// @dev Can only be called by the contract owner and if minting is enabled
  /// @param to The address to mint tokens to
  /// @param amount The amount of tokens to mint
  function mint(address to, uint256 amount) external onlyOwner {
    if (!isMintable()) {
      revert MintingNotEnabled();
    }
    if (isMaxAmountOfTokensSet()) {
      if (balanceOf(to) + amount > maxTokenAmountPerAddress) {
        revert DestBalanceExceedsMaxAllowed(to);
      }
    }

    super._mint(to, amount);
  }

  /// @notice Burns a specific amount of tokens
  /// @dev Can only be called by the contract owner and if burning is enabled
  /// @param amount The amount of tokens to be burned
  function burn(uint256 amount) external onlyOwner {
    if (!isBurnable()) {
      revert BurningNotEnabled();
    }
    _burn(msg.sender, amount);
  }

  /// @notice Renounces ownership of the contract
  /// @dev Leaves the contract without an owner, disabling any functions that require the owner's authorization
  function renounceOwnership() public override onlyOwner {
    super.renounceOwnership();
  }

  /// @notice Transfers ownership of the contract to a new account
  /// @dev Can only be called by the current owner
  /// @param newOwner The address of the new owner
  function transferOwnership(address newOwner) public override onlyOwner {
    super.transferOwnership(newOwner);
  }

  // Internal Functions

  /// @notice Calculates the tax amount for a transfer
  /// @param sender The address initiating the transfer
  /// @param amount The amount of tokens being transferred
  /// @return taxAmount The calculated tax amount
  function _taxAmount(
    address sender,
    uint256 amount
  ) internal view returns (uint256 taxAmount) {
    taxAmount = 0;
    if (taxBPS != 0 && sender != taxAddress) {
      taxAmount = (amount * taxBPS) / MAX_BPS_AMOUNT;
    }
  }

  /// @notice Calculates the deflation amount for a transfer
  /// @param amount The amount of tokens being transferred
  /// @return deflationAmount The calculated deflation amount
  function _deflationAmount(
    uint256 amount
  ) internal view returns (uint256 deflationAmount) {
    deflationAmount = 0;
    if (deflationBPS != 0) {
      deflationAmount = (amount * deflationBPS) / MAX_BPS_AMOUNT;
    }
  }
}

// SPDX-License-Identifier: MIT
pragma solidity 0.8.17;

library LibCommon {
  /*´:°•.°+.*•´.*:˚.°*.˚•´.°:°•.°•.*•´.*:˚.°*.˚•´.°:°•.°+.*•´.*:*/
  /*                       CUSTOM ERRORS                        */
  /*.•°:°.´+˚.*°.˚:*.´•*.+°.•°:´*.´•*.•°.•°:°.´:•˚°.*°.˚:*.´+°.•*/

  /// @dev The ETH transfer has failed.
  error ETHTransferFailed();

  /// @dev The address is the zero address.
  error ZeroAddress();

  /// @notice raised when an ERC20 transfer fails
  error TransferFailed();

  /*´:°•.°+.*•´.*:˚.°*.˚•´.°:°•.°•.*•´.*:˚.°*.˚•´.°:°•.°+.*•´.*:*/
  /*                       ETH OPERATIONS                       */
  /*.•°:°.´+˚.*°.˚:*.´•*.+°.•°:´*.´•*.•°.•°:°.´:•˚°.*°.˚:*.´+°.•*/

  /// @notice Taken from Solady (https://github.com/vectorized/solady/blob/main/src/utils/SafeTransferLib.sol)
  /// @dev Sends `amount` (in wei) ETH to `to`.
  /// Reverts upon failure.
  function safeTransferETH(address to, uint256 amount) internal {
    // solhint-disable-next-line no-inline-assembly
    assembly {
      // Transfer the ETH and check if it succeeded or not.
      if iszero(call(gas(), to, amount, 0, 0, 0, 0)) {
        // Store the function selector of `ETHTransferFailed()`.
        // bytes4(keccak256(bytes("ETHTransferFailed()"))) = 0xb12d13eb
        mstore(0x00, 0xb12d13eb)
        // Revert with (offset, size).
        revert(0x1c, 0x04)
      }
    }
  }

  /// @notice Validates that the address is not the zero address using assembly.
  /// @dev Reverts if the address is the zero address.
  function validateAddress(address addr) internal pure {
    // solhint-disable-next-line no-inline-assembly
    assembly {
      if iszero(shl(96, addr)) {
        // Store the function selector of `ZeroAddress()`.
        // bytes4(keccak256(bytes("ZeroAddress()"))) = 0xd92e233d
        mstore(0x00, 0xd92e233d)
        // Revert with (offset, size).
        revert(0x1c, 0x04)
      }
    }
  }

  /// @notice Helper function to transfer ERC20 tokens without the need for SafeERC20.
  /// @dev Reverts if the ERC20 transfer fails.
  /// @param tokenAddress The address of the ERC20 token.
  /// @param from The address to transfer the tokens from.
  /// @param to The address to transfer the tokens to.
  /// @param amount The amount of tokens to transfer.
  function safeTransferFrom(
    address tokenAddress,
    address from,
    address to,
    uint256 amount
  ) internal returns (bool) {
    // solhint-disable-next-line avoid-low-level-calls
    (bool success, bytes memory data) = tokenAddress.call(
      abi.encodeWithSignature(
        "transferFrom(address,address,uint256)",
        from,
        to,
        amount
      )
    );
    if (!success) {
      if (data.length != 0) {
        // bubble up error
        // solhint-disable-next-line no-inline-assembly
        assembly {
          let returndata_size := mload(data)
          revert(add(32, data), returndata_size)
        }
      } else {
        revert TransferFailed();
      }
    }
    return true;
  }

  /// @notice Helper function to transfer ERC20 tokens without the need for SafeERC20.
  /// @dev Reverts if the ERC20 transfer fails.
  /// @param tokenAddress The address of the ERC20 token.
  /// @param to The address to transfer the tokens to.
  /// @param amount The amount of tokens to transfer.
  function safeTransfer(
    address tokenAddress,
    address to,
    uint256 amount
  ) internal returns (bool) {
    // solhint-disable-next-line avoid-low-level-calls
    (bool success, bytes memory data) = tokenAddress.call(
      abi.encodeWithSignature("transfer(address,uint256)", to, amount)
    );
    if (!success) {
      if (data.length != 0) {
        // bubble up error
        // solhint-disable-next-line no-inline-assembly
        assembly {
          let returndata_size := mload(data)
          revert(add(32, data), returndata_size)
        }
      } else {
        revert TransferFailed();
      }
    }
    return true;
  }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (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;
    }
}

// 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 v4.9.0) (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 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);
}