// File: contracts/ERC20_Game_Currency.sol



// SPDX-License-Identifier: Commons-Clause-1.0
//  __  __     _        ___     _
// |  \/  |___| |_ __ _| __|_ _| |__
// | |\/| / -_)  _/ _` | _/ _` | '_ \
// |_|  |_\___|\__\__,_|_|\__,_|_.__/
//
// Launch your crypto game or gamefi project's blockchain
// infrastructure & game APIs fast with https://trymetafab.com

pragma solidity ^0.8.16;

import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import "./common/ERC2771Context_Upgradeable.sol";

contract ERC20_Game_Currency is ERC20, ERC2771Context_Upgradeable, Ownable {
  uint public feeBps;
  uint public feeFixed;
  uint public feeCap;
  address public feeRecipient;
  address public childChainManagerProxy;
  uint256 public immutable supplyCap;

  event TransferRef(address indexed sender, address indexed recipient, uint256 amount, uint256 ref);
  event BatchTransferRef(address indexed sender, address[] recipients, uint256[] amounts, uint256[] refs);

  constructor(string memory _name, string memory _symbol, uint256 _supplyCap, address _forwarder)
  ERC20(_name, _symbol)
  ERC2771Context_Upgradeable(_forwarder) {
    feeRecipient = _msgSender();
    supplyCap = _supplyCap;
  }

  function mint(address _to, uint256 _amount) external onlyOwner {
    require(childChainManagerProxy == address(0), "Minting disabled when Polygon bridge is enabled.");

    _mint(_to, _amount);
  }

  function burn(uint256 _amount) external {
    _burn(_msgSender(), _amount);
  }

  function transferWithRef(address recipient, uint256 amount, uint256 ref) external returns (bool) {
    _transfer(_msgSender(), recipient, amount);
    emit TransferRef(_msgSender(), recipient, amount, ref);
    return true;
  }

  /**
   * @dev Support for transfer batching
   */

  function batchTransfer(address[] calldata recipients, uint256[] calldata amounts) external returns (bool) {
    return _batchTransfer(recipients, amounts, false);
  }

  function batchTransferWithRefs(address[] calldata recipients, uint256[] calldata amounts, uint256[] calldata refs) external returns (bool) {
    return _batchTransferWithRefs(recipients, amounts, refs, false);
  }

  function batchTransferWithFees(address[] calldata recipients, uint256[] calldata amounts) external returns (bool) {
    return _batchTransfer(recipients, amounts, true);
  }

  function batchTransferWithFeesRefs(address[] calldata recipients, uint256[] calldata amounts, uint256[] calldata refs) external returns (bool) {
    return _batchTransferWithRefs(recipients, amounts, refs, true);
  }

  function _batchTransfer(address[] calldata recipients, uint256[] calldata amounts, bool withFee) private returns (bool) {
    require(recipients.length > 0, "No recipients");
    require(recipients.length == amounts.length, "amounts argument size mismatched");

    for (uint256 i = 0; i < recipients.length; i++) {
      if (withFee) {
        transferWithFee(recipients[i], amounts[i]);
      } else {
        transfer(recipients[i], amounts[i]);
      }
    }

    return true;
  }

  function _batchTransferWithRefs(address[] calldata recipients, uint256[] calldata amounts, uint256[] calldata refs, bool withFee) private returns (bool) {
    require(recipients.length > 0, "No recipients");
    require(recipients.length == amounts.length, "amounts argument size mismatched");
    require(recipients.length == refs.length, "refs argument size mismatched");

    for (uint256 i = 0; i < recipients.length; i++) {
      if (withFee) {
        transferWithFee(recipients[i], amounts[i]);
      } else {
        transfer(recipients[i], amounts[i]);
      }

      if (refs[i] > 0) {
        emit TransferRef(_msgSender(), recipients[i], amounts[i], refs[i]);
      }
    }

    emit BatchTransferRef(_msgSender(), recipients, amounts, refs);

    return true;
  }

  /**
   * @dev Support for Polygon bridge
   */

  function deposit(address user, bytes calldata depositData) external {
    require(_msgSender() == childChainManagerProxy, "Address not allowed to deposit.");

    uint256 amount = abi.decode(depositData, (uint256));

    _mint(user, amount);
  }

  function withdraw(uint256 amount) external {
    _burn(_msgSender(), amount);
  }

  function updateChildChainManager(address _childChainManagerProxy) external onlyOwner {
    require(_childChainManagerProxy != address(0), "Bad ChildChainManagerProxy address.");

    childChainManagerProxy = _childChainManagerProxy;
  }

  /**
   * @dev Support for fee based transfers, typically used with gasless transactions
   */

  function burnWithFee(uint256 amount) external returns (bool) { // TODO, can't use _transfer to 0 addr
    _transferWithFee(address(0), amount, true);

    return true;
  }

  function transferWithFee(address recipient, uint256 amount) public returns (bool) {
    _transferWithFee(recipient, amount, false);

    return true;
  }

  function transferWithFeeRef(address recipient, uint256 amount, uint256 ref) external returns (bool) {
    transferWithFee(recipient, amount);

    emit TransferRef(_msgSender(), recipient, amount, ref);

    return true;
  }

  function _transferWithFee(address recipient, uint256 amount, bool isBurn) private {
    uint senderBalance = balanceOf(_msgSender());
    require(feeRecipient != address(0), "Fee recipient not set, cannot use transferWithFee");
    require(senderBalance >= amount, "ERC20: transfer amount exceeds balance.");

    uint percentageFee = amount * feeBps / 10000 + feeFixed;
    uint fee = percentageFee <= feeCap ? percentageFee : feeCap;

    _transfer(_msgSender(), feeRecipient, fee);

    if (isBurn) {
      _burn(_msgSender(), amount - fee);
    } else {
      _transfer(_msgSender(), recipient, amount - fee);
    }
  }

  function setFees(address recipient, uint _feeBps, uint _feeFixed, uint _feeCap) external onlyOwner {
    require(recipient != address(0), "recipient is 0 addr");
    feeRecipient = recipient;
    feeBps = _feeBps;
    feeFixed = _feeFixed;
    feeCap = _feeCap;
  }

  /**
   * @dev Support for gasless transactions
   */

  function upgradeTrustedForwarder(address _newTrustedForwarder) external onlyOwner {
    _upgradeTrustedForwarder(_newTrustedForwarder);
  }

  function _msgSender() internal view override(Context, ERC2771Context_Upgradeable) returns (address) {
    return super._msgSender();
  }

  function _msgData() internal view override(Context, ERC2771Context_Upgradeable) returns (bytes calldata) {
    return super._msgData();
  }

  /**
   * @dev Support for optional supply cap
   */

  function _mint(address _account, uint256 _amount) internal virtual override {
    if (supplyCap > 0) {
      require(ERC20.totalSupply() + _amount <= supplyCap, "ERC20 supply cap exceeded");
    }

    super._mint(_account, _amount);
  }
}

// File: @openzeppelin/contracts/access/Ownable.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (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 anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing 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);
    }
}

// File: @openzeppelin/contracts/token/ERC20/ERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (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.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How
 * to implement supply mechanisms].
 *
 * 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}.
     *
     * The default value of {decimals} is 18. To select a different value for
     * {decimals} you should overload it.
     *
     * 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 value {ERC20} uses, unless this function is
     * 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;
        }
        _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;
        _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;
        }
        _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 {}
}

// File: contracts/common/ERC2771Context_Upgradeable.sol



// SPDX-License-Identifier: Commons-Clause-1.0
//  __  __     _        ___     _
// |  \/  |___| |_ __ _| __|_ _| |__
// | |\/| / -_)  _/ _` | _/ _` | '_ \
// |_|  |_\___|\__\__,_|_|\__,_|_.__/
//
// Launch your crypto game or gamefi project's blockchain
// infrastructure & game APIs fast with https://trymetafab.com

pragma solidity ^0.8.16;

import "@openzeppelin/contracts/utils/Context.sol";

/**
 * @dev Context variant with ERC2771 support and upgradeable trusted forwarder.
 */

abstract contract ERC2771Context_Upgradeable is Context {
  address private trustedForwarder;

  constructor(address _trustedForwarder) {
    trustedForwarder = _trustedForwarder;
  }

  function isTrustedForwarder(address forwarder) public view virtual returns (bool) {
    return forwarder == trustedForwarder;
  }

  function _upgradeTrustedForwarder(address _trustedForwarder) internal {
    trustedForwarder = _trustedForwarder;
  }

  function _msgSender() internal view virtual override returns (address sender) {
    if (isTrustedForwarder(msg.sender)) {
      // The assembly code is more direct than the Solidity version using `abi.decode`.
      /// @solidity memory-safe-assembly
      assembly {
        sender := shr(96, calldataload(sub(calldatasize(), 20)))
      }
    } else {
      return super._msgSender();
    }
  }

  function _msgData() internal view virtual override returns (bytes calldata) {
    if (isTrustedForwarder(msg.sender)) {
      return msg.data[:msg.data.length - 20];
    } else {
      return super._msgData();
    }
  }
}

// File: @openzeppelin/contracts/utils/Context.sol



// 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;
    }
}

// File: @openzeppelin/contracts/token/ERC20/IERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.6.0) (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);
}

// File: @openzeppelin/contracts/token/ERC20/extensions/IERC20Metadata.sol



// 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);
}