creation_sourcecode: // Sources flattened with hardhat v2.12.6 https://hardhat.org
  
  // File @openzeppelin/contracts/access/IAccessControl.sol@v4.8.1
  
  // SPDX-License-Identifier: MIT
  // OpenZeppelin Contracts v4.4.1 (access/IAccessControl.sol)
  
  pragma solidity ^0.8.0;
  
  /**
   * @dev External interface of AccessControl declared to support ERC165 detection.
   */
  interface IAccessControl {
      /**
       * @dev Emitted when `newAdminRole` is set as ``role``'s admin role, replacing `previousAdminRole`
       *
       * `DEFAULT_ADMIN_ROLE` is the starting admin for all roles, despite
       * {RoleAdminChanged} not being emitted signaling this.
       *
       * _Available since v3.1._
       */
      event RoleAdminChanged(bytes32 indexed role, bytes32 indexed previousAdminRole, bytes32 indexed newAdminRole);
  
      /**
       * @dev Emitted when `account` is granted `role`.
       *
       * `sender` is the account that originated the contract call, an admin role
       * bearer except when using {AccessControl-_setupRole}.
       */
      event RoleGranted(bytes32 indexed role, address indexed account, address indexed sender);
  
      /**
       * @dev Emitted when `account` is revoked `role`.
       *
       * `sender` is the account that originated the contract call:
       *   - if using `revokeRole`, it is the admin role bearer
       *   - if using `renounceRole`, it is the role bearer (i.e. `account`)
       */
      event RoleRevoked(bytes32 indexed role, address indexed account, address indexed sender);
  
      /**
       * @dev Returns `true` if `account` has been granted `role`.
       */
      function hasRole(bytes32 role, address account) external view returns (bool);
  
      /**
       * @dev Returns the admin role that controls `role`. See {grantRole} and
       * {revokeRole}.
       *
       * To change a role's admin, use {AccessControl-_setRoleAdmin}.
       */
      function getRoleAdmin(bytes32 role) external view returns (bytes32);
  
      /**
       * @dev Grants `role` to `account`.
       *
       * If `account` had not been already granted `role`, emits a {RoleGranted}
       * event.
       *
       * Requirements:
       *
       * - the caller must have ``role``'s admin role.
       */
      function grantRole(bytes32 role, address account) external;
  
      /**
       * @dev Revokes `role` from `account`.
       *
       * If `account` had been granted `role`, emits a {RoleRevoked} event.
       *
       * Requirements:
       *
       * - the caller must have ``role``'s admin role.
       */
      function revokeRole(bytes32 role, address account) external;
  
      /**
       * @dev Revokes `role` from the calling account.
       *
       * Roles are often managed via {grantRole} and {revokeRole}: this function's
       * purpose is to provide a mechanism for accounts to lose their privileges
       * if they are compromised (such as when a trusted device is misplaced).
       *
       * If the calling account had been granted `role`, emits a {RoleRevoked}
       * event.
       *
       * Requirements:
       *
       * - the caller must be `account`.
       */
      function renounceRole(bytes32 role, address account) external;
  }
  
  
  // File @openzeppelin/contracts/utils/Context.sol@v4.8.1
  
  
  // 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/utils/introspection/IERC165.sol@v4.8.1
  
  
  // OpenZeppelin Contracts v4.4.1 (utils/introspection/IERC165.sol)
  
  pragma solidity ^0.8.0;
  
  /**
   * @dev Interface of the ERC165 standard, as defined in the
   * https://eips.ethereum.org/EIPS/eip-165[EIP].
   *
   * Implementers can declare support of contract interfaces, which can then be
   * queried by others ({ERC165Checker}).
   *
   * For an implementation, see {ERC165}.
   */
  interface IERC165 {
      /**
       * @dev Returns true if this contract implements the interface defined by
       * `interfaceId`. See the corresponding
       * https://eips.ethereum.org/EIPS/eip-165#how-interfaces-are-identified[EIP section]
       * to learn more about how these ids are created.
       *
       * This function call must use less than 30 000 gas.
       */
      function supportsInterface(bytes4 interfaceId) external view returns (bool);
  }
  
  
  // File @openzeppelin/contracts/utils/introspection/ERC165.sol@v4.8.1
  
  
  // OpenZeppelin Contracts v4.4.1 (utils/introspection/ERC165.sol)
  
  pragma solidity ^0.8.0;
  
  /**
   * @dev Implementation of the {IERC165} interface.
   *
   * Contracts that want to implement ERC165 should inherit from this contract and override {supportsInterface} to check
   * for the additional interface id that will be supported. For example:
   *
   * ```solidity
   * function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
   *     return interfaceId == type(MyInterface).interfaceId || super.supportsInterface(interfaceId);
   * }
   * ```
   *
   * Alternatively, {ERC165Storage} provides an easier to use but more expensive implementation.
   */
  abstract contract ERC165 is IERC165 {
      /**
       * @dev See {IERC165-supportsInterface}.
       */
      function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
          return interfaceId == type(IERC165).interfaceId;
      }
  }
  
  
  // File @openzeppelin/contracts/utils/math/Math.sol@v4.8.1
  
  
  // OpenZeppelin Contracts (last updated v4.8.0) (utils/math/Math.sol)
  
  pragma solidity ^0.8.0;
  
  /**
   * @dev Standard math utilities missing in the Solidity language.
   */
  library Math {
      enum Rounding {
          Down, // Toward negative infinity
          Up, // Toward infinity
          Zero // Toward zero
      }
  
      /**
       * @dev Returns the largest of two numbers.
       */
      function max(uint256 a, uint256 b) internal pure returns (uint256) {
          return a > b ? a : b;
      }
  
      /**
       * @dev Returns the smallest of two numbers.
       */
      function min(uint256 a, uint256 b) internal pure returns (uint256) {
          return a < b ? a : b;
      }
  
      /**
       * @dev Returns the average of two numbers. The result is rounded towards
       * zero.
       */
      function average(uint256 a, uint256 b) internal pure returns (uint256) {
          // (a + b) / 2 can overflow.
          return (a & b) + (a ^ b) / 2;
      }
  
      /**
       * @dev Returns the ceiling of the division of two numbers.
       *
       * This differs from standard division with `/` in that it rounds up instead
       * of rounding down.
       */
      function ceilDiv(uint256 a, uint256 b) internal pure returns (uint256) {
          // (a + b - 1) / b can overflow on addition, so we distribute.
          return a == 0 ? 0 : (a - 1) / b + 1;
      }
  
      /**
       * @notice Calculates floor(x * y / denominator) with full precision. Throws if result overflows a uint256 or denominator == 0
       * @dev Original credit to Remco Bloemen under MIT license (https://xn--2-umb.com/21/muldiv)
       * with further edits by Uniswap Labs also under MIT license.
       */
      function mulDiv(
          uint256 x,
          uint256 y,
          uint256 denominator
      ) internal pure returns (uint256 result) {
          unchecked {
              // 512-bit multiply [prod1 prod0] = x * y. Compute the product mod 2^256 and mod 2^256 - 1, then use
              // use the Chinese Remainder Theorem to reconstruct the 512 bit result. The result is stored in two 256
              // variables such that product = prod1 * 2^256 + prod0.
              uint256 prod0; // Least significant 256 bits of the product
              uint256 prod1; // Most significant 256 bits of the product
              assembly {
                  let mm := mulmod(x, y, not(0))
                  prod0 := mul(x, y)
                  prod1 := sub(sub(mm, prod0), lt(mm, prod0))
              }
  
              // Handle non-overflow cases, 256 by 256 division.
              if (prod1 == 0) {
                  return prod0 / denominator;
              }
  
              // Make sure the result is less than 2^256. Also prevents denominator == 0.
              require(denominator > prod1);
  
              ///////////////////////////////////////////////
              // 512 by 256 division.
              ///////////////////////////////////////////////
  
              // Make division exact by subtracting the remainder from [prod1 prod0].
              uint256 remainder;
              assembly {
                  // Compute remainder using mulmod.
                  remainder := mulmod(x, y, denominator)
  
                  // Subtract 256 bit number from 512 bit number.
                  prod1 := sub(prod1, gt(remainder, prod0))
                  prod0 := sub(prod0, remainder)
              }
  
              // Factor powers of two out of denominator and compute largest power of two divisor of denominator. Always >= 1.
              // See https://cs.stackexchange.com/q/138556/92363.
  
              // Does not overflow because the denominator cannot be zero at this stage in the function.
              uint256 twos = denominator & (~denominator + 1);
              assembly {
                  // Divide denominator by twos.
                  denominator := div(denominator, twos)
  
                  // Divide [prod1 prod0] by twos.
                  prod0 := div(prod0, twos)
  
                  // Flip twos such that it is 2^256 / twos. If twos is zero, then it becomes one.
                  twos := add(div(sub(0, twos), twos), 1)
              }
  
              // Shift in bits from prod1 into prod0.
              prod0 |= prod1 * twos;
  
              // Invert denominator mod 2^256. Now that denominator is an odd number, it has an inverse modulo 2^256 such
              // that denominator * inv = 1 mod 2^256. Compute the inverse by starting with a seed that is correct for
              // four bits. That is, denominator * inv = 1 mod 2^4.
              uint256 inverse = (3 * denominator) ^ 2;
  
              // Use the Newton-Raphson iteration to improve the precision. Thanks to Hensel's lifting lemma, this also works
              // in modular arithmetic, doubling the correct bits in each step.
              inverse *= 2 - denominator * inverse; // inverse mod 2^8
              inverse *= 2 - denominator * inverse; // inverse mod 2^16
              inverse *= 2 - denominator * inverse; // inverse mod 2^32
              inverse *= 2 - denominator * inverse; // inverse mod 2^64
              inverse *= 2 - denominator * inverse; // inverse mod 2^128
              inverse *= 2 - denominator * inverse; // inverse mod 2^256
  
              // Because the division is now exact we can divide by multiplying with the modular inverse of denominator.
              // This will give us the correct result modulo 2^256. Since the preconditions guarantee that the outcome is
              // less than 2^256, this is the final result. We don't need to compute the high bits of the result and prod1
              // is no longer required.
              result = prod0 * inverse;
              return result;
          }
      }
  
      /**
       * @notice Calculates x * y / denominator with full precision, following the selected rounding direction.
       */
      function mulDiv(
          uint256 x,
          uint256 y,
          uint256 denominator,
          Rounding rounding
      ) internal pure returns (uint256) {
          uint256 result = mulDiv(x, y, denominator);
          if (rounding == Rounding.Up && mulmod(x, y, denominator) > 0) {
              result += 1;
          }
          return result;
      }
  
      /**
       * @dev Returns the square root of a number. If the number is not a perfect square, the value is rounded down.
       *
       * Inspired by Henry S. Warren, Jr.'s "Hacker's Delight" (Chapter 11).
       */
      function sqrt(uint256 a) internal pure returns (uint256) {
          if (a == 0) {
              return 0;
          }
  
          // For our first guess, we get the biggest power of 2 which is smaller than the square root of the target.
          //
          // We know that the "msb" (most significant bit) of our target number `a` is a power of 2 such that we have
          // `msb(a) <= a < 2*msb(a)`. This value can be written `msb(a)=2**k` with `k=log2(a)`.
          //
          // This can be rewritten `2**log2(a) <= a < 2**(log2(a) + 1)`
          // → `sqrt(2**k) <= sqrt(a) < sqrt(2**(k+1))`
          // → `2**(k/2) <= sqrt(a) < 2**((k+1)/2) <= 2**(k/2 + 1)`
          //
          // Consequently, `2**(log2(a) / 2)` is a good first approximation of `sqrt(a)` with at least 1 correct bit.
          uint256 result = 1 << (log2(a) >> 1);
  
          // At this point `result` is an estimation with one bit of precision. We know the true value is a uint128,
          // since it is the square root of a uint256. Newton's method converges quadratically (precision doubles at
          // every iteration). We thus need at most 7 iteration to turn our partial result with one bit of precision
          // into the expected uint128 result.
          unchecked {
              result = (result + a / result) >> 1;
              result = (result + a / result) >> 1;
              result = (result + a / result) >> 1;
              result = (result + a / result) >> 1;
              result = (result + a / result) >> 1;
              result = (result + a / result) >> 1;
              result = (result + a / result) >> 1;
              return min(result, a / result);
          }
      }
  
      /**
       * @notice Calculates sqrt(a), following the selected rounding direction.
       */
      function sqrt(uint256 a, Rounding rounding) internal pure returns (uint256) {
          unchecked {
              uint256 result = sqrt(a);
              return result + (rounding == Rounding.Up && result * result < a ? 1 : 0);
          }
      }
  
      /**
       * @dev Return the log in base 2, rounded down, of a positive value.
       * Returns 0 if given 0.
       */
      function log2(uint256 value) internal pure returns (uint256) {
          uint256 result = 0;
          unchecked {
              if (value >> 128 > 0) {
                  value >>= 128;
                  result += 128;
              }
              if (value >> 64 > 0) {
                  value >>= 64;
                  result += 64;
              }
              if (value >> 32 > 0) {
                  value >>= 32;
                  result += 32;
              }
              if (value >> 16 > 0) {
                  value >>= 16;
                  result += 16;
              }
              if (value >> 8 > 0) {
                  value >>= 8;
                  result += 8;
              }
              if (value >> 4 > 0) {
                  value >>= 4;
                  result += 4;
              }
              if (value >> 2 > 0) {
                  value >>= 2;
                  result += 2;
              }
              if (value >> 1 > 0) {
                  result += 1;
              }
          }
          return result;
      }
  
      /**
       * @dev Return the log in base 2, following the selected rounding direction, of a positive value.
       * Returns 0 if given 0.
       */
      function log2(uint256 value, Rounding rounding) internal pure returns (uint256) {
          unchecked {
              uint256 result = log2(value);
              return result + (rounding == Rounding.Up && 1 << result < value ? 1 : 0);
          }
      }
  
      /**
       * @dev Return the log in base 10, rounded down, of a positive value.
       * Returns 0 if given 0.
       */
      function log10(uint256 value) internal pure returns (uint256) {
          uint256 result = 0;
          unchecked {
              if (value >= 10**64) {
                  value /= 10**64;
                  result += 64;
              }
              if (value >= 10**32) {
                  value /= 10**32;
                  result += 32;
              }
              if (value >= 10**16) {
                  value /= 10**16;
                  result += 16;
              }
              if (value >= 10**8) {
                  value /= 10**8;
                  result += 8;
              }
              if (value >= 10**4) {
                  value /= 10**4;
                  result += 4;
              }
              if (value >= 10**2) {
                  value /= 10**2;
                  result += 2;
              }
              if (value >= 10**1) {
                  result += 1;
              }
          }
          return result;
      }
  
      /**
       * @dev Return the log in base 10, following the selected rounding direction, of a positive value.
       * Returns 0 if given 0.
       */
      function log10(uint256 value, Rounding rounding) internal pure returns (uint256) {
          unchecked {
              uint256 result = log10(value);
              return result + (rounding == Rounding.Up && 10**result < value ? 1 : 0);
          }
      }
  
      /**
       * @dev Return the log in base 256, rounded down, of a positive value.
       * Returns 0 if given 0.
       *
       * Adding one to the result gives the number of pairs of hex symbols needed to represent `value` as a hex string.
       */
      function log256(uint256 value) internal pure returns (uint256) {
          uint256 result = 0;
          unchecked {
              if (value >> 128 > 0) {
                  value >>= 128;
                  result += 16;
              }
              if (value >> 64 > 0) {
                  value >>= 64;
                  result += 8;
              }
              if (value >> 32 > 0) {
                  value >>= 32;
                  result += 4;
              }
              if (value >> 16 > 0) {
                  value >>= 16;
                  result += 2;
              }
              if (value >> 8 > 0) {
                  result += 1;
              }
          }
          return result;
      }
  
      /**
       * @dev Return the log in base 10, following the selected rounding direction, of a positive value.
       * Returns 0 if given 0.
       */
      function log256(uint256 value, Rounding rounding) internal pure returns (uint256) {
          unchecked {
              uint256 result = log256(value);
              return result + (rounding == Rounding.Up && 1 << (result * 8) < value ? 1 : 0);
          }
      }
  }
  
  
  // File @openzeppelin/contracts/utils/Strings.sol@v4.8.1
  
  
  // OpenZeppelin Contracts (last updated v4.8.0) (utils/Strings.sol)
  
  pragma solidity ^0.8.0;
  
  /**
   * @dev String operations.
   */
  library Strings {
      bytes16 private constant _SYMBOLS = "0123456789abcdef";
      uint8 private constant _ADDRESS_LENGTH = 20;
  
      /**
       * @dev Converts a `uint256` to its ASCII `string` decimal representation.
       */
      function toString(uint256 value) internal pure returns (string memory) {
          unchecked {
              uint256 length = Math.log10(value) + 1;
              string memory buffer = new string(length);
              uint256 ptr;
              /// @solidity memory-safe-assembly
              assembly {
                  ptr := add(buffer, add(32, length))
              }
              while (true) {
                  ptr--;
                  /// @solidity memory-safe-assembly
                  assembly {
                      mstore8(ptr, byte(mod(value, 10), _SYMBOLS))
                  }
                  value /= 10;
                  if (value == 0) break;
              }
              return buffer;
          }
      }
  
      /**
       * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation.
       */
      function toHexString(uint256 value) internal pure returns (string memory) {
          unchecked {
              return toHexString(value, Math.log256(value) + 1);
          }
      }
  
      /**
       * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation with fixed length.
       */
      function toHexString(uint256 value, uint256 length) internal pure returns (string memory) {
          bytes memory buffer = new bytes(2 * length + 2);
          buffer[0] = "0";
          buffer[1] = "x";
          for (uint256 i = 2 * length + 1; i > 1; --i) {
              buffer[i] = _SYMBOLS[value & 0xf];
              value >>= 4;
          }
          require(value == 0, "Strings: hex length insufficient");
          return string(buffer);
      }
  
      /**
       * @dev Converts an `address` with fixed length of 20 bytes to its not checksummed ASCII `string` hexadecimal representation.
       */
      function toHexString(address addr) internal pure returns (string memory) {
          return toHexString(uint256(uint160(addr)), _ADDRESS_LENGTH);
      }
  }
  
  
  // File @openzeppelin/contracts/access/AccessControl.sol@v4.8.1
  
  
  // OpenZeppelin Contracts (last updated v4.8.0) (access/AccessControl.sol)
  
  pragma solidity ^0.8.0;
  
  
  
  
  /**
   * @dev Contract module that allows children to implement role-based access
   * control mechanisms. This is a lightweight version that doesn't allow enumerating role
   * members except through off-chain means by accessing the contract event logs. Some
   * applications may benefit from on-chain enumerability, for those cases see
   * {AccessControlEnumerable}.
   *
   * Roles are referred to by their `bytes32` identifier. These should be exposed
   * in the external API and be unique. The best way to achieve this is by
   * using `public constant` hash digests:
   *
   * ```
   * bytes32 public constant MY_ROLE = keccak256("MY_ROLE");
   * ```
   *
   * Roles can be used to represent a set of permissions. To restrict access to a
   * function call, use {hasRole}:
   *
   * ```
   * function foo() public {
   *     require(hasRole(MY_ROLE, msg.sender));
   *     ...
   * }
   * ```
   *
   * Roles can be granted and revoked dynamically via the {grantRole} and
   * {revokeRole} functions. Each role has an associated admin role, and only
   * accounts that have a role's admin role can call {grantRole} and {revokeRole}.
   *
   * By default, the admin role for all roles is `DEFAULT_ADMIN_ROLE`, which means
   * that only accounts with this role will be able to grant or revoke other
   * roles. More complex role relationships can be created by using
   * {_setRoleAdmin}.
   *
   * WARNING: The `DEFAULT_ADMIN_ROLE` is also its own admin: it has permission to
   * grant and revoke this role. Extra precautions should be taken to secure
   * accounts that have been granted it.
   */
  abstract contract AccessControl is Context, IAccessControl, ERC165 {
      struct RoleData {
          mapping(address => bool) members;
          bytes32 adminRole;
      }
  
      mapping(bytes32 => RoleData) private _roles;
  
      bytes32 public constant DEFAULT_ADMIN_ROLE = 0x00;
  
      /**
       * @dev Modifier that checks that an account has a specific role. Reverts
       * with a standardized message including the required role.
       *
       * The format of the revert reason is given by the following regular expression:
       *
       *  /^AccessControl: account (0x[0-9a-f]{40}) is missing role (0x[0-9a-f]{64})$/
       *
       * _Available since v4.1._
       */
      modifier onlyRole(bytes32 role) {
          _checkRole(role);
          _;
      }
  
      /**
       * @dev See {IERC165-supportsInterface}.
       */
      function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
          return interfaceId == type(IAccessControl).interfaceId || super.supportsInterface(interfaceId);
      }
  
      /**
       * @dev Returns `true` if `account` has been granted `role`.
       */
      function hasRole(bytes32 role, address account) public view virtual override returns (bool) {
          return _roles[role].members[account];
      }
  
      /**
       * @dev Revert with a standard message if `_msgSender()` is missing `role`.
       * Overriding this function changes the behavior of the {onlyRole} modifier.
       *
       * Format of the revert message is described in {_checkRole}.
       *
       * _Available since v4.6._
       */
      function _checkRole(bytes32 role) internal view virtual {
          _checkRole(role, _msgSender());
      }
  
      /**
       * @dev Revert with a standard message if `account` is missing `role`.
       *
       * The format of the revert reason is given by the following regular expression:
       *
       *  /^AccessControl: account (0x[0-9a-f]{40}) is missing role (0x[0-9a-f]{64})$/
       */
      function _checkRole(bytes32 role, address account) internal view virtual {
          if (!hasRole(role, account)) {
              revert(
                  string(
                      abi.encodePacked(
                          "AccessControl: account ",
                          Strings.toHexString(account),
                          " is missing role ",
                          Strings.toHexString(uint256(role), 32)
                      )
                  )
              );
          }
      }
  
      /**
       * @dev Returns the admin role that controls `role`. See {grantRole} and
       * {revokeRole}.
       *
       * To change a role's admin, use {_setRoleAdmin}.
       */
      function getRoleAdmin(bytes32 role) public view virtual override returns (bytes32) {
          return _roles[role].adminRole;
      }
  
      /**
       * @dev Grants `role` to `account`.
       *
       * If `account` had not been already granted `role`, emits a {RoleGranted}
       * event.
       *
       * Requirements:
       *
       * - the caller must have ``role``'s admin role.
       *
       * May emit a {RoleGranted} event.
       */
      function grantRole(bytes32 role, address account) public virtual override onlyRole(getRoleAdmin(role)) {
          _grantRole(role, account);
      }
  
      /**
       * @dev Revokes `role` from `account`.
       *
       * If `account` had been granted `role`, emits a {RoleRevoked} event.
       *
       * Requirements:
       *
       * - the caller must have ``role``'s admin role.
       *
       * May emit a {RoleRevoked} event.
       */
      function revokeRole(bytes32 role, address account) public virtual override onlyRole(getRoleAdmin(role)) {
          _revokeRole(role, account);
      }
  
      /**
       * @dev Revokes `role` from the calling account.
       *
       * Roles are often managed via {grantRole} and {revokeRole}: this function's
       * purpose is to provide a mechanism for accounts to lose their privileges
       * if they are compromised (such as when a trusted device is misplaced).
       *
       * If the calling account had been revoked `role`, emits a {RoleRevoked}
       * event.
       *
       * Requirements:
       *
       * - the caller must be `account`.
       *
       * May emit a {RoleRevoked} event.
       */
      function renounceRole(bytes32 role, address account) public virtual override {
          require(account == _msgSender(), "AccessControl: can only renounce roles for self");
  
          _revokeRole(role, account);
      }
  
      /**
       * @dev Grants `role` to `account`.
       *
       * If `account` had not been already granted `role`, emits a {RoleGranted}
       * event. Note that unlike {grantRole}, this function doesn't perform any
       * checks on the calling account.
       *
       * May emit a {RoleGranted} event.
       *
       * [WARNING]
       * ====
       * This function should only be called from the constructor when setting
       * up the initial roles for the system.
       *
       * Using this function in any other way is effectively circumventing the admin
       * system imposed by {AccessControl}.
       * ====
       *
       * NOTE: This function is deprecated in favor of {_grantRole}.
       */
      function _setupRole(bytes32 role, address account) internal virtual {
          _grantRole(role, account);
      }
  
      /**
       * @dev Sets `adminRole` as ``role``'s admin role.
       *
       * Emits a {RoleAdminChanged} event.
       */
      function _setRoleAdmin(bytes32 role, bytes32 adminRole) internal virtual {
          bytes32 previousAdminRole = getRoleAdmin(role);
          _roles[role].adminRole = adminRole;
          emit RoleAdminChanged(role, previousAdminRole, adminRole);
      }
  
      /**
       * @dev Grants `role` to `account`.
       *
       * Internal function without access restriction.
       *
       * May emit a {RoleGranted} event.
       */
      function _grantRole(bytes32 role, address account) internal virtual {
          if (!hasRole(role, account)) {
              _roles[role].members[account] = true;
              emit RoleGranted(role, account, _msgSender());
          }
      }
  
      /**
       * @dev Revokes `role` from `account`.
       *
       * Internal function without access restriction.
       *
       * May emit a {RoleRevoked} event.
       */
      function _revokeRole(bytes32 role, address account) internal virtual {
          if (hasRole(role, account)) {
              _roles[role].members[account] = false;
              emit RoleRevoked(role, account, _msgSender());
          }
      }
  }
  
  
  // File @openzeppelin/contracts/access/IAccessControlEnumerable.sol@v4.8.1
  
  
  // OpenZeppelin Contracts v4.4.1 (access/IAccessControlEnumerable.sol)
  
  pragma solidity ^0.8.0;
  
  /**
   * @dev External interface of AccessControlEnumerable declared to support ERC165 detection.
   */
  interface IAccessControlEnumerable is IAccessControl {
      /**
       * @dev Returns one of the accounts that have `role`. `index` must be a
       * value between 0 and {getRoleMemberCount}, non-inclusive.
       *
       * Role bearers are not sorted in any particular way, and their ordering may
       * change at any point.
       *
       * WARNING: When using {getRoleMember} and {getRoleMemberCount}, make sure
       * you perform all queries on the same block. See the following
       * https://forum.openzeppelin.com/t/iterating-over-elements-on-enumerableset-in-openzeppelin-contracts/2296[forum post]
       * for more information.
       */
      function getRoleMember(bytes32 role, uint256 index) external view returns (address);
  
      /**
       * @dev Returns the number of accounts that have `role`. Can be used
       * together with {getRoleMember} to enumerate all bearers of a role.
       */
      function getRoleMemberCount(bytes32 role) external view returns (uint256);
  }
  
  
  // File @openzeppelin/contracts/utils/structs/EnumerableSet.sol@v4.8.1
  
  
  // OpenZeppelin Contracts (last updated v4.8.0) (utils/structs/EnumerableSet.sol)
  // This file was procedurally generated from scripts/generate/templates/EnumerableSet.js.
  
  pragma solidity ^0.8.0;
  
  /**
   * @dev Library for managing
   * https://en.wikipedia.org/wiki/Set_(abstract_data_type)[sets] of primitive
   * types.
   *
   * Sets have the following properties:
   *
   * - Elements are added, removed, and checked for existence in constant time
   * (O(1)).
   * - Elements are enumerated in O(n). No guarantees are made on the ordering.
   *
   * ```
   * contract Example {
   *     // Add the library methods
   *     using EnumerableSet for EnumerableSet.AddressSet;
   *
   *     // Declare a set state variable
   *     EnumerableSet.AddressSet private mySet;
   * }
   * ```
   *
   * As of v3.3.0, sets of type `bytes32` (`Bytes32Set`), `address` (`AddressSet`)
   * and `uint256` (`UintSet`) are supported.
   *
   * [WARNING]
   * ====
   * Trying to delete such a structure from storage will likely result in data corruption, rendering the structure
   * unusable.
   * See https://github.com/ethereum/solidity/pull/11843[ethereum/solidity#11843] for more info.
   *
   * In order to clean an EnumerableSet, you can either remove all elements one by one or create a fresh instance using an
   * array of EnumerableSet.
   * ====
   */
  library EnumerableSet {
      // To implement this library for multiple types with as little code
      // repetition as possible, we write it in terms of a generic Set type with
      // bytes32 values.
      // The Set implementation uses private functions, and user-facing
      // implementations (such as AddressSet) are just wrappers around the
      // underlying Set.
      // This means that we can only create new EnumerableSets for types that fit
      // in bytes32.
  
      struct Set {
          // Storage of set values
          bytes32[] _values;
          // Position of the value in the `values` array, plus 1 because index 0
          // means a value is not in the set.
          mapping(bytes32 => uint256) _indexes;
      }
  
      /**
       * @dev Add a value to a set. O(1).
       *
       * Returns true if the value was added to the set, that is if it was not
       * already present.
       */
      function _add(Set storage set, bytes32 value) private returns (bool) {
          if (!_contains(set, value)) {
              set._values.push(value);
              // The value is stored at length-1, but we add 1 to all indexes
              // and use 0 as a sentinel value
              set._indexes[value] = set._values.length;
              return true;
          } else {
              return false;
          }
      }
  
      /**
       * @dev Removes a value from a set. O(1).
       *
       * Returns true if the value was removed from the set, that is if it was
       * present.
       */
      function _remove(Set storage set, bytes32 value) private returns (bool) {
          // We read and store the value's index to prevent multiple reads from the same storage slot
          uint256 valueIndex = set._indexes[value];
  
          if (valueIndex != 0) {
              // Equivalent to contains(set, value)
              // To delete an element from the _values array in O(1), we swap the element to delete with the last one in
              // the array, and then remove the last element (sometimes called as 'swap and pop').
              // This modifies the order of the array, as noted in {at}.
  
              uint256 toDeleteIndex = valueIndex - 1;
              uint256 lastIndex = set._values.length - 1;
  
              if (lastIndex != toDeleteIndex) {
                  bytes32 lastValue = set._values[lastIndex];
  
                  // Move the last value to the index where the value to delete is
                  set._values[toDeleteIndex] = lastValue;
                  // Update the index for the moved value
                  set._indexes[lastValue] = valueIndex; // Replace lastValue's index to valueIndex
              }
  
              // Delete the slot where the moved value was stored
              set._values.pop();
  
              // Delete the index for the deleted slot
              delete set._indexes[value];
  
              return true;
          } else {
              return false;
          }
      }
  
      /**
       * @dev Returns true if the value is in the set. O(1).
       */
      function _contains(Set storage set, bytes32 value) private view returns (bool) {
          return set._indexes[value] != 0;
      }
  
      /**
       * @dev Returns the number of values on the set. O(1).
       */
      function _length(Set storage set) private view returns (uint256) {
          return set._values.length;
      }
  
      /**
       * @dev Returns the value stored at position `index` in the set. O(1).
       *
       * Note that there are no guarantees on the ordering of values inside the
       * array, and it may change when more values are added or removed.
       *
       * Requirements:
       *
       * - `index` must be strictly less than {length}.
       */
      function _at(Set storage set, uint256 index) private view returns (bytes32) {
          return set._values[index];
      }
  
      /**
       * @dev Return the entire set in an array
       *
       * WARNING: This operation will copy the entire storage to memory, which can be quite expensive. This is designed
       * to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that
       * this function has an unbounded cost, and using it as part of a state-changing function may render the function
       * uncallable if the set grows to a point where copying to memory consumes too much gas to fit in a block.
       */
      function _values(Set storage set) private view returns (bytes32[] memory) {
          return set._values;
      }
  
      // Bytes32Set
  
      struct Bytes32Set {
          Set _inner;
      }
  
      /**
       * @dev Add a value to a set. O(1).
       *
       * Returns true if the value was added to the set, that is if it was not
       * already present.
       */
      function add(Bytes32Set storage set, bytes32 value) internal returns (bool) {
          return _add(set._inner, value);
      }
  
      /**
       * @dev Removes a value from a set. O(1).
       *
       * Returns true if the value was removed from the set, that is if it was
       * present.
       */
      function remove(Bytes32Set storage set, bytes32 value) internal returns (bool) {
          return _remove(set._inner, value);
      }
  
      /**
       * @dev Returns true if the value is in the set. O(1).
       */
      function contains(Bytes32Set storage set, bytes32 value) internal view returns (bool) {
          return _contains(set._inner, value);
      }
  
      /**
       * @dev Returns the number of values in the set. O(1).
       */
      function length(Bytes32Set storage set) internal view returns (uint256) {
          return _length(set._inner);
      }
  
      /**
       * @dev Returns the value stored at position `index` in the set. O(1).
       *
       * Note that there are no guarantees on the ordering of values inside the
       * array, and it may change when more values are added or removed.
       *
       * Requirements:
       *
       * - `index` must be strictly less than {length}.
       */
      function at(Bytes32Set storage set, uint256 index) internal view returns (bytes32) {
          return _at(set._inner, index);
      }
  
      /**
       * @dev Return the entire set in an array
       *
       * WARNING: This operation will copy the entire storage to memory, which can be quite expensive. This is designed
       * to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that
       * this function has an unbounded cost, and using it as part of a state-changing function may render the function
       * uncallable if the set grows to a point where copying to memory consumes too much gas to fit in a block.
       */
      function values(Bytes32Set storage set) internal view returns (bytes32[] memory) {
          bytes32[] memory store = _values(set._inner);
          bytes32[] memory result;
  
          /// @solidity memory-safe-assembly
          assembly {
              result := store
          }
  
          return result;
      }
  
      // AddressSet
  
      struct AddressSet {
          Set _inner;
      }
  
      /**
       * @dev Add a value to a set. O(1).
       *
       * Returns true if the value was added to the set, that is if it was not
       * already present.
       */
      function add(AddressSet storage set, address value) internal returns (bool) {
          return _add(set._inner, bytes32(uint256(uint160(value))));
      }
  
      /**
       * @dev Removes a value from a set. O(1).
       *
       * Returns true if the value was removed from the set, that is if it was
       * present.
       */
      function remove(AddressSet storage set, address value) internal returns (bool) {
          return _remove(set._inner, bytes32(uint256(uint160(value))));
      }
  
      /**
       * @dev Returns true if the value is in the set. O(1).
       */
      function contains(AddressSet storage set, address value) internal view returns (bool) {
          return _contains(set._inner, bytes32(uint256(uint160(value))));
      }
  
      /**
       * @dev Returns the number of values in the set. O(1).
       */
      function length(AddressSet storage set) internal view returns (uint256) {
          return _length(set._inner);
      }
  
      /**
       * @dev Returns the value stored at position `index` in the set. O(1).
       *
       * Note that there are no guarantees on the ordering of values inside the
       * array, and it may change when more values are added or removed.
       *
       * Requirements:
       *
       * - `index` must be strictly less than {length}.
       */
      function at(AddressSet storage set, uint256 index) internal view returns (address) {
          return address(uint160(uint256(_at(set._inner, index))));
      }
  
      /**
       * @dev Return the entire set in an array
       *
       * WARNING: This operation will copy the entire storage to memory, which can be quite expensive. This is designed
       * to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that
       * this function has an unbounded cost, and using it as part of a state-changing function may render the function
       * uncallable if the set grows to a point where copying to memory consumes too much gas to fit in a block.
       */
      function values(AddressSet storage set) internal view returns (address[] memory) {
          bytes32[] memory store = _values(set._inner);
          address[] memory result;
  
          /// @solidity memory-safe-assembly
          assembly {
              result := store
          }
  
          return result;
      }
  
      // UintSet
  
      struct UintSet {
          Set _inner;
      }
  
      /**
       * @dev Add a value to a set. O(1).
       *
       * Returns true if the value was added to the set, that is if it was not
       * already present.
       */
      function add(UintSet storage set, uint256 value) internal returns (bool) {
          return _add(set._inner, bytes32(value));
      }
  
      /**
       * @dev Removes a value from a set. O(1).
       *
       * Returns true if the value was removed from the set, that is if it was
       * present.
       */
      function remove(UintSet storage set, uint256 value) internal returns (bool) {
          return _remove(set._inner, bytes32(value));
      }
  
      /**
       * @dev Returns true if the value is in the set. O(1).
       */
      function contains(UintSet storage set, uint256 value) internal view returns (bool) {
          return _contains(set._inner, bytes32(value));
      }
  
      /**
       * @dev Returns the number of values in the set. O(1).
       */
      function length(UintSet storage set) internal view returns (uint256) {
          return _length(set._inner);
      }
  
      /**
       * @dev Returns the value stored at position `index` in the set. O(1).
       *
       * Note that there are no guarantees on the ordering of values inside the
       * array, and it may change when more values are added or removed.
       *
       * Requirements:
       *
       * - `index` must be strictly less than {length}.
       */
      function at(UintSet storage set, uint256 index) internal view returns (uint256) {
          return uint256(_at(set._inner, index));
      }
  
      /**
       * @dev Return the entire set in an array
       *
       * WARNING: This operation will copy the entire storage to memory, which can be quite expensive. This is designed
       * to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that
       * this function has an unbounded cost, and using it as part of a state-changing function may render the function
       * uncallable if the set grows to a point where copying to memory consumes too much gas to fit in a block.
       */
      function values(UintSet storage set) internal view returns (uint256[] memory) {
          bytes32[] memory store = _values(set._inner);
          uint256[] memory result;
  
          /// @solidity memory-safe-assembly
          assembly {
              result := store
          }
  
          return result;
      }
  }
  
  
  // File @openzeppelin/contracts/access/AccessControlEnumerable.sol@v4.8.1
  
  
  // OpenZeppelin Contracts (last updated v4.5.0) (access/AccessControlEnumerable.sol)
  
  pragma solidity ^0.8.0;
  
  
  
  /**
   * @dev Extension of {AccessControl} that allows enumerating the members of each role.
   */
  abstract contract AccessControlEnumerable is IAccessControlEnumerable, AccessControl {
      using EnumerableSet for EnumerableSet.AddressSet;
  
      mapping(bytes32 => EnumerableSet.AddressSet) private _roleMembers;
  
      /**
       * @dev See {IERC165-supportsInterface}.
       */
      function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
          return interfaceId == type(IAccessControlEnumerable).interfaceId || super.supportsInterface(interfaceId);
      }
  
      /**
       * @dev Returns one of the accounts that have `role`. `index` must be a
       * value between 0 and {getRoleMemberCount}, non-inclusive.
       *
       * Role bearers are not sorted in any particular way, and their ordering may
       * change at any point.
       *
       * WARNING: When using {getRoleMember} and {getRoleMemberCount}, make sure
       * you perform all queries on the same block. See the following
       * https://forum.openzeppelin.com/t/iterating-over-elements-on-enumerableset-in-openzeppelin-contracts/2296[forum post]
       * for more information.
       */
      function getRoleMember(bytes32 role, uint256 index) public view virtual override returns (address) {
          return _roleMembers[role].at(index);
      }
  
      /**
       * @dev Returns the number of accounts that have `role`. Can be used
       * together with {getRoleMember} to enumerate all bearers of a role.
       */
      function getRoleMemberCount(bytes32 role) public view virtual override returns (uint256) {
          return _roleMembers[role].length();
      }
  
      /**
       * @dev Overload {_grantRole} to track enumerable memberships
       */
      function _grantRole(bytes32 role, address account) internal virtual override {
          super._grantRole(role, account);
          _roleMembers[role].add(account);
      }
  
      /**
       * @dev Overload {_revokeRole} to track enumerable memberships
       */
      function _revokeRole(bytes32 role, address account) internal virtual override {
          super._revokeRole(role, account);
          _roleMembers[role].remove(account);
      }
  }
  
  
  // File @openzeppelin/contracts/security/Pausable.sol@v4.8.1
  
  
  // OpenZeppelin Contracts (last updated v4.7.0) (security/Pausable.sol)
  
  pragma solidity ^0.8.0;
  
  /**
   * @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());
      }
  }
  
  
  // File @openzeppelin/contracts/token/ERC20/extensions/draft-IERC20Permit.sol@v4.8.1
  
  
  // OpenZeppelin Contracts v4.4.1 (token/ERC20/extensions/draft-IERC20Permit.sol)
  
  pragma solidity ^0.8.0;
  
  /**
   * @dev Interface of the ERC20 Permit extension allowing approvals to be made via signatures, as defined in
   * https://eips.ethereum.org/EIPS/eip-2612[EIP-2612].
   *
   * Adds the {permit} method, which can be used to change an account's ERC20 allowance (see {IERC20-allowance}) by
   * presenting a message signed by the account. By not relying on {IERC20-approve}, the token holder account doesn't
   * need to send a transaction, and thus is not required to hold Ether at all.
   */
  interface IERC20Permit {
      /**
       * @dev Sets `value` as the allowance of `spender` over ``owner``'s tokens,
       * given ``owner``'s signed approval.
       *
       * IMPORTANT: The same issues {IERC20-approve} has related to transaction
       * ordering also apply here.
       *
       * Emits an {Approval} event.
       *
       * Requirements:
       *
       * - `spender` cannot be the zero address.
       * - `deadline` must be a timestamp in the future.
       * - `v`, `r` and `s` must be a valid `secp256k1` signature from `owner`
       * over the EIP712-formatted function arguments.
       * - the signature must use ``owner``'s current nonce (see {nonces}).
       *
       * For more information on the signature format, see the
       * https://eips.ethereum.org/EIPS/eip-2612#specification[relevant EIP
       * section].
       */
      function permit(
          address owner,
          address spender,
          uint256 value,
          uint256 deadline,
          uint8 v,
          bytes32 r,
          bytes32 s
      ) external;
  
      /**
       * @dev Returns the current nonce for `owner`. This value must be
       * included whenever a signature is generated for {permit}.
       *
       * Every successful call to {permit} increases ``owner``'s nonce by one. This
       * prevents a signature from being used multiple times.
       */
      function nonces(address owner) external view returns (uint256);
  
      /**
       * @dev Returns the domain separator used in the encoding of the signature for {permit}, as defined by {EIP712}.
       */
      // solhint-disable-next-line func-name-mixedcase
      function DOMAIN_SEPARATOR() external view returns (bytes32);
  }
  
  
  // File @openzeppelin/contracts/token/ERC20/IERC20.sol@v4.8.1
  
  
  // 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/utils/Address.sol@v4.8.1
  
  
  // OpenZeppelin Contracts (last updated v4.8.0) (utils/Address.sol)
  
  pragma solidity ^0.8.1;
  
  /**
   * @dev Collection of functions related to the address type
   */
  library Address {
      /**
       * @dev Returns true if `account` is a contract.
       *
       * [IMPORTANT]
       * ====
       * It is unsafe to assume that an address for which this function returns
       * false is an externally-owned account (EOA) and not a contract.
       *
       * Among others, `isContract` will return false for the following
       * types of addresses:
       *
       *  - an externally-owned account
       *  - a contract in construction
       *  - an address where a contract will be created
       *  - an address where a contract lived, but was destroyed
       * ====
       *
       * [IMPORTANT]
       * ====
       * You shouldn't rely on `isContract` to protect against flash loan attacks!
       *
       * Preventing calls from contracts is highly discouraged. It breaks composability, breaks support for smart wallets
       * like Gnosis Safe, and does not provide security since it can be circumvented by calling from a contract
       * constructor.
       * ====
       */
      function isContract(address account) internal view returns (bool) {
          // This method relies on extcodesize/address.code.length, which returns 0
          // for contracts in construction, since the code is only stored at the end
          // of the constructor execution.
  
          return account.code.length > 0;
      }
  
      /**
       * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
       * `recipient`, forwarding all available gas and reverting on errors.
       *
       * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
       * of certain opcodes, possibly making contracts go over the 2300 gas limit
       * imposed by `transfer`, making them unable to receive funds via
       * `transfer`. {sendValue} removes this limitation.
       *
       * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
       *
       * IMPORTANT: because control is transferred to `recipient`, care must be
       * taken to not create reentrancy vulnerabilities. Consider using
       * {ReentrancyGuard} or the
       * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
       */
      function sendValue(address payable recipient, uint256 amount) internal {
          require(address(this).balance >= amount, "Address: insufficient balance");
  
          (bool success, ) = recipient.call{value: amount}("");
          require(success, "Address: unable to send value, recipient may have reverted");
      }
  
      /**
       * @dev Performs a Solidity function call using a low level `call`. A
       * plain `call` is an unsafe replacement for a function call: use this
       * function instead.
       *
       * If `target` reverts with a revert reason, it is bubbled up by this
       * function (like regular Solidity function calls).
       *
       * Returns the raw returned data. To convert to the expected return value,
       * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
       *
       * Requirements:
       *
       * - `target` must be a contract.
       * - calling `target` with `data` must not revert.
       *
       * _Available since v3.1._
       */
      function functionCall(address target, bytes memory data) internal returns (bytes memory) {
          return functionCallWithValue(target, data, 0, "Address: low-level call failed");
      }
  
      /**
       * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
       * `errorMessage` as a fallback revert reason when `target` reverts.
       *
       * _Available since v3.1._
       */
      function functionCall(
          address target,
          bytes memory data,
          string memory errorMessage
      ) internal returns (bytes memory) {
          return functionCallWithValue(target, data, 0, errorMessage);
      }
  
      /**
       * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
       * but also transferring `value` wei to `target`.
       *
       * Requirements:
       *
       * - the calling contract must have an ETH balance of at least `value`.
       * - the called Solidity function must be `payable`.
       *
       * _Available since v3.1._
       */
      function functionCallWithValue(
          address target,
          bytes memory data,
          uint256 value
      ) internal returns (bytes memory) {
          return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
      }
  
      /**
       * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
       * with `errorMessage` as a fallback revert reason when `target` reverts.
       *
       * _Available since v3.1._
       */
      function functionCallWithValue(
          address target,
          bytes memory data,
          uint256 value,
          string memory errorMessage
      ) internal returns (bytes memory) {
          require(address(this).balance >= value, "Address: insufficient balance for call");
          (bool success, bytes memory returndata) = target.call{value: value}(data);
          return verifyCallResultFromTarget(target, success, returndata, errorMessage);
      }
  
      /**
       * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
       * but performing a static call.
       *
       * _Available since v3.3._
       */
      function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
          return functionStaticCall(target, data, "Address: low-level static call failed");
      }
  
      /**
       * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
       * but performing a static call.
       *
       * _Available since v3.3._
       */
      function functionStaticCall(
          address target,
          bytes memory data,
          string memory errorMessage
      ) internal view returns (bytes memory) {
          (bool success, bytes memory returndata) = target.staticcall(data);
          return verifyCallResultFromTarget(target, success, returndata, errorMessage);
      }
  
      /**
       * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
       * but performing a delegate call.
       *
       * _Available since v3.4._
       */
      function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
          return functionDelegateCall(target, data, "Address: low-level delegate call failed");
      }
  
      /**
       * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
       * but performing a delegate call.
       *
       * _Available since v3.4._
       */
      function functionDelegateCall(
          address target,
          bytes memory data,
          string memory errorMessage
      ) internal returns (bytes memory) {
          (bool success, bytes memory returndata) = target.delegatecall(data);
          return verifyCallResultFromTarget(target, success, returndata, errorMessage);
      }
  
      /**
       * @dev Tool to verify that a low level call to smart-contract was successful, and revert (either by bubbling
       * the revert reason or using the provided one) in case of unsuccessful call or if target was not a contract.
       *
       * _Available since v4.8._
       */
      function verifyCallResultFromTarget(
          address target,
          bool success,
          bytes memory returndata,
          string memory errorMessage
      ) internal view returns (bytes memory) {
          if (success) {
              if (returndata.length == 0) {
                  // only check isContract if the call was successful and the return data is empty
                  // otherwise we already know that it was a contract
                  require(isContract(target), "Address: call to non-contract");
              }
              return returndata;
          } else {
              _revert(returndata, errorMessage);
          }
      }
  
      /**
       * @dev Tool to verify that a low level call was successful, and revert if it wasn't, either by bubbling the
       * revert reason or using the provided one.
       *
       * _Available since v4.3._
       */
      function verifyCallResult(
          bool success,
          bytes memory returndata,
          string memory errorMessage
      ) internal pure returns (bytes memory) {
          if (success) {
              return returndata;
          } else {
              _revert(returndata, errorMessage);
          }
      }
  
      function _revert(bytes memory returndata, string memory errorMessage) private pure {
          // Look for revert reason and bubble it up if present
          if (returndata.length > 0) {
              // The easiest way to bubble the revert reason is using memory via assembly
              /// @solidity memory-safe-assembly
              assembly {
                  let returndata_size := mload(returndata)
                  revert(add(32, returndata), returndata_size)
              }
          } else {
              revert(errorMessage);
          }
      }
  }
  
  
  // File @openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol@v4.8.1
  
  
  // OpenZeppelin Contracts (last updated v4.8.0) (token/ERC20/utils/SafeERC20.sol)
  
  pragma solidity ^0.8.0;
  
  
  
  /**
   * @title SafeERC20
   * @dev Wrappers around ERC20 operations that throw on failure (when the token
   * contract returns false). Tokens that return no value (and instead revert or
   * throw on failure) are also supported, non-reverting calls are assumed to be
   * successful.
   * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
   * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
   */
  library SafeERC20 {
      using Address for address;
  
      function safeTransfer(
          IERC20 token,
          address to,
          uint256 value
      ) internal {
          _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
      }
  
      function safeTransferFrom(
          IERC20 token,
          address from,
          address to,
          uint256 value
      ) internal {
          _callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
      }
  
      /**
       * @dev Deprecated. This function has issues similar to the ones found in
       * {IERC20-approve}, and its usage is discouraged.
       *
       * Whenever possible, use {safeIncreaseAllowance} and
       * {safeDecreaseAllowance} instead.
       */
      function safeApprove(
          IERC20 token,
          address spender,
          uint256 value
      ) internal {
          // safeApprove should only be called when setting an initial allowance,
          // or when resetting it to zero. To increase and decrease it, use
          // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
          require(
              (value == 0) || (token.allowance(address(this), spender) == 0),
              "SafeERC20: approve from non-zero to non-zero allowance"
          );
          _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
      }
  
      function safeIncreaseAllowance(
          IERC20 token,
          address spender,
          uint256 value
      ) internal {
          uint256 newAllowance = token.allowance(address(this), spender) + value;
          _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
      }
  
      function safeDecreaseAllowance(
          IERC20 token,
          address spender,
          uint256 value
      ) internal {
          unchecked {
              uint256 oldAllowance = token.allowance(address(this), spender);
              require(oldAllowance >= value, "SafeERC20: decreased allowance below zero");
              uint256 newAllowance = oldAllowance - value;
              _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
          }
      }
  
      function safePermit(
          IERC20Permit token,
          address owner,
          address spender,
          uint256 value,
          uint256 deadline,
          uint8 v,
          bytes32 r,
          bytes32 s
      ) internal {
          uint256 nonceBefore = token.nonces(owner);
          token.permit(owner, spender, value, deadline, v, r, s);
          uint256 nonceAfter = token.nonces(owner);
          require(nonceAfter == nonceBefore + 1, "SafeERC20: permit did not succeed");
      }
  
      /**
       * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
       * on the return value: the return value is optional (but if data is returned, it must not be false).
       * @param token The token targeted by the call.
       * @param data The call data (encoded using abi.encode or one of its variants).
       */
      function _callOptionalReturn(IERC20 token, bytes memory data) private {
          // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
          // we're implementing it ourselves. We use {Address-functionCall} to perform this call, which verifies that
          // the target address contains contract code and also asserts for success in the low-level call.
  
          bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
          if (returndata.length > 0) {
              // Return data is optional
              require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
          }
      }
  }
  
  
  // File @openzeppelin/contracts/utils/cryptography/ECDSA.sol@v4.8.1
  
  
  // OpenZeppelin Contracts (last updated v4.8.0) (utils/cryptography/ECDSA.sol)
  
  pragma solidity ^0.8.0;
  
  /**
   * @dev Elliptic Curve Digital Signature Algorithm (ECDSA) operations.
   *
   * These functions can be used to verify that a message was signed by the holder
   * of the private keys of a given address.
   */
  library ECDSA {
      enum RecoverError {
          NoError,
          InvalidSignature,
          InvalidSignatureLength,
          InvalidSignatureS,
          InvalidSignatureV // Deprecated in v4.8
      }
  
      function _throwError(RecoverError error) private pure {
          if (error == RecoverError.NoError) {
              return; // no error: do nothing
          } else if (error == RecoverError.InvalidSignature) {
              revert("ECDSA: invalid signature");
          } else if (error == RecoverError.InvalidSignatureLength) {
              revert("ECDSA: invalid signature length");
          } else if (error == RecoverError.InvalidSignatureS) {
              revert("ECDSA: invalid signature 's' value");
          }
      }
  
      /**
       * @dev Returns the address that signed a hashed message (`hash`) with
       * `signature` or error string. This address can then be used for verification purposes.
       *
       * The `ecrecover` EVM opcode allows for malleable (non-unique) signatures:
       * this function rejects them by requiring the `s` value to be in the lower
       * half order, and the `v` value to be either 27 or 28.
       *
       * IMPORTANT: `hash` _must_ be the result of a hash operation for the
       * verification to be secure: it is possible to craft signatures that
       * recover to arbitrary addresses for non-hashed data. A safe way to ensure
       * this is by receiving a hash of the original message (which may otherwise
       * be too long), and then calling {toEthSignedMessageHash} on it.
       *
       * Documentation for signature generation:
       * - with https://web3js.readthedocs.io/en/v1.3.4/web3-eth-accounts.html#sign[Web3.js]
       * - with https://docs.ethers.io/v5/api/signer/#Signer-signMessage[ethers]
       *
       * _Available since v4.3._
       */
      function tryRecover(bytes32 hash, bytes memory signature) internal pure returns (address, RecoverError) {
          if (signature.length == 65) {
              bytes32 r;
              bytes32 s;
              uint8 v;
              // ecrecover takes the signature parameters, and the only way to get them
              // currently is to use assembly.
              /// @solidity memory-safe-assembly
              assembly {
                  r := mload(add(signature, 0x20))
                  s := mload(add(signature, 0x40))
                  v := byte(0, mload(add(signature, 0x60)))
              }
              return tryRecover(hash, v, r, s);
          } else {
              return (address(0), RecoverError.InvalidSignatureLength);
          }
      }
  
      /**
       * @dev Returns the address that signed a hashed message (`hash`) with
       * `signature`. This address can then be used for verification purposes.
       *
       * The `ecrecover` EVM opcode allows for malleable (non-unique) signatures:
       * this function rejects them by requiring the `s` value to be in the lower
       * half order, and the `v` value to be either 27 or 28.
       *
       * IMPORTANT: `hash` _must_ be the result of a hash operation for the
       * verification to be secure: it is possible to craft signatures that
       * recover to arbitrary addresses for non-hashed data. A safe way to ensure
       * this is by receiving a hash of the original message (which may otherwise
       * be too long), and then calling {toEthSignedMessageHash} on it.
       */
      function recover(bytes32 hash, bytes memory signature) internal pure returns (address) {
          (address recovered, RecoverError error) = tryRecover(hash, signature);
          _throwError(error);
          return recovered;
      }
  
      /**
       * @dev Overload of {ECDSA-tryRecover} that receives the `r` and `vs` short-signature fields separately.
       *
       * See https://eips.ethereum.org/EIPS/eip-2098[EIP-2098 short signatures]
       *
       * _Available since v4.3._
       */
      function tryRecover(
          bytes32 hash,
          bytes32 r,
          bytes32 vs
      ) internal pure returns (address, RecoverError) {
          bytes32 s = vs & bytes32(0x7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff);
          uint8 v = uint8((uint256(vs) >> 255) + 27);
          return tryRecover(hash, v, r, s);
      }
  
      /**
       * @dev Overload of {ECDSA-recover} that receives the `r and `vs` short-signature fields separately.
       *
       * _Available since v4.2._
       */
      function recover(
          bytes32 hash,
          bytes32 r,
          bytes32 vs
      ) internal pure returns (address) {
          (address recovered, RecoverError error) = tryRecover(hash, r, vs);
          _throwError(error);
          return recovered;
      }
  
      /**
       * @dev Overload of {ECDSA-tryRecover} that receives the `v`,
       * `r` and `s` signature fields separately.
       *
       * _Available since v4.3._
       */
      function tryRecover(
          bytes32 hash,
          uint8 v,
          bytes32 r,
          bytes32 s
      ) internal pure returns (address, RecoverError) {
          // EIP-2 still allows signature malleability for ecrecover(). Remove this possibility and make the signature
          // unique. Appendix F in the Ethereum Yellow paper (https://ethereum.github.io/yellowpaper/paper.pdf), defines
          // the valid range for s in (301): 0 < s < secp256k1n ÷ 2 + 1, and for v in (302): v ∈ {27, 28}. Most
          // signatures from current libraries generate a unique signature with an s-value in the lower half order.
          //
          // If your library generates malleable signatures, such as s-values in the upper range, calculate a new s-value
          // with 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141 - s1 and flip v from 27 to 28 or
          // vice versa. If your library also generates signatures with 0/1 for v instead 27/28, add 27 to v to accept
          // these malleable signatures as well.
          if (uint256(s) > 0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5D576E7357A4501DDFE92F46681B20A0) {
              return (address(0), RecoverError.InvalidSignatureS);
          }
  
          // If the signature is valid (and not malleable), return the signer address
          address signer = ecrecover(hash, v, r, s);
          if (signer == address(0)) {
              return (address(0), RecoverError.InvalidSignature);
          }
  
          return (signer, RecoverError.NoError);
      }
  
      /**
       * @dev Overload of {ECDSA-recover} that receives the `v`,
       * `r` and `s` signature fields separately.
       */
      function recover(
          bytes32 hash,
          uint8 v,
          bytes32 r,
          bytes32 s
      ) internal pure returns (address) {
          (address recovered, RecoverError error) = tryRecover(hash, v, r, s);
          _throwError(error);
          return recovered;
      }
  
      /**
       * @dev Returns an Ethereum Signed Message, created from a `hash`. This
       * produces hash corresponding to the one signed with the
       * https://eth.wiki/json-rpc/API#eth_sign[`eth_sign`]
       * JSON-RPC method as part of EIP-191.
       *
       * See {recover}.
       */
      function toEthSignedMessageHash(bytes32 hash) internal pure returns (bytes32) {
          // 32 is the length in bytes of hash,
          // enforced by the type signature above
          return keccak256(abi.encodePacked("\x19Ethereum Signed Message:\n32", hash));
      }
  
      /**
       * @dev Returns an Ethereum Signed Message, created from `s`. This
       * produces hash corresponding to the one signed with the
       * https://eth.wiki/json-rpc/API#eth_sign[`eth_sign`]
       * JSON-RPC method as part of EIP-191.
       *
       * See {recover}.
       */
      function toEthSignedMessageHash(bytes memory s) internal pure returns (bytes32) {
          return keccak256(abi.encodePacked("\x19Ethereum Signed Message:\n", Strings.toString(s.length), s));
      }
  
      /**
       * @dev Returns an Ethereum Signed Typed Data, created from a
       * `domainSeparator` and a `structHash`. This produces hash corresponding
       * to the one signed with the
       * https://eips.ethereum.org/EIPS/eip-712[`eth_signTypedData`]
       * JSON-RPC method as part of EIP-712.
       *
       * See {recover}.
       */
      function toTypedDataHash(bytes32 domainSeparator, bytes32 structHash) internal pure returns (bytes32) {
          return keccak256(abi.encodePacked("\x19\x01", domainSeparator, structHash));
      }
  }
  
  
  // File @openzeppelin/contracts/utils/math/SafeMath.sol@v4.8.1
  
  
  // OpenZeppelin Contracts (last updated v4.6.0) (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;
          }
      }
  }
  
  
  // File contracts/ERC20DistributionNative.sol
  
  
  pragma solidity =0.8.4;
  
  
  
  
  
  /**
   * @title ERC20DistributionNative
   * @dev A token distribution contract that sells an initial supply of tokens at a
     linearly decreasing exchange rate. After depletion of the initial supply, tokens
     can be recycled and resold at the end rate
   */
  contract ERC20DistributionNative is Pausable, AccessControlEnumerable {
      using SafeMath for uint256;
      using SafeERC20 for IERC20;
      using ECDSA for bytes32;
      
      bytes32 public constant KYCMANAGER_ROLE = keccak256("KYCMANAGER_ROLE");
   
      error InvalidBeneficiary();
      error InvalidRate();
      error InvalidDividerRate();
      error Unauthorized();
      error KYCNotSet();
      error InvalidKYCToken();
      error KYCTokenExpired();
      error DistributionOutOfRange();
      error PurchaseNotAllowed();
      error CurrentRateExceedsLimit();
      error CurrentRateExceedsLimitSlippage();
      error InsufficientTokensAvailable();
      error FiatTransferFailed();
  
      event TokensSold(address recipient, uint256 amountEth, uint256 amountToken, uint256 actualRate);
      event kycApproverChanged(address newKYCApprover);
      
      IERC20 public immutable _trusted_token; // Contract address for the distributed token
  
      address payable private immutable _beneficiary;
  
      address public _kyc_approver; // address that signs the KYC approval
  
      uint256 private immutable _startrate_distribution; // stored internally in high res
      uint256 private immutable _endrate_distribution;   // stored internally in high res
      uint256 private immutable _divider_rate;   // scaling factor for start and end rate
      
      uint256 private immutable _total_distribution_balance;  // total volume of initial distribution
      uint256 private _current_distributed_balance; // total volume sold upto now
  
      /**
       * @dev Creates a distribution contract that sells any ERC20 _trusted_token to the
       * beneficiary using Ether as fiat currency, based on an linear descending or flat exchange rate
       * @param distToken address of the token contract whose tokens are distributed
       * @param distBeneficiary address of the beneficiary to whom received Ether is sent
       * @param distStartRate exchange rate at start of distribution 
       * @param distEndRate exhange rate at the end of distribution
       * @param dividerRate scale factor that is to be applied to the start/end rate
       * @param distVolumeTokens total distribution volume
      */
      constructor(
          IERC20 distToken,
          address payable distBeneficiary,
          uint256 distStartRate,   // gain / eth
          uint256 distEndRate,     // gain / eth
          uint256 dividerRate,
          uint256 distVolumeTokens
      ) {
          if(distBeneficiary == address(0)) revert InvalidBeneficiary();
          
          if(distStartRate == 0 || distEndRate == 0) revert InvalidRate();
  
          if(distStartRate < distEndRate) revert InvalidRate();
  
          if(dividerRate == 0) revert InvalidDividerRate();
          
          _setupRole(DEFAULT_ADMIN_ROLE, msg.sender);
          _setupRole(KYCMANAGER_ROLE, msg.sender);
  
          _trusted_token = distToken;
          _beneficiary = distBeneficiary;
          
          _startrate_distribution  = distStartRate;
          _endrate_distribution  = distEndRate;
          _divider_rate = dividerRate;
          
          _total_distribution_balance = distVolumeTokens;
          _current_distributed_balance = 0;
          
          // when the contract is deployed, it starts as paused
          _pause();
      }
      
      /**
          * @dev standard getter for beneficiary (address)
          */
      function beneficiary() external view virtual returns (address) {
        return _beneficiary;
      }
  
      /**
          * @dev standard getter for startrate_distribution (tokens/ETH)
          */
      function startrate_distribution() external view virtual returns (uint256) {
        return _startrate_distribution;
      }
  
      /**
          * @dev standard getter for endrate_distribution (tokens/ETH)
          */
      function endrate_distribution() external view virtual returns (uint256) {
        return _endrate_distribution;
      }
  
      /**
          * @dev standard getter for divider_rate (no unit)
          */
      function dividerrate_distribution() external view virtual returns (uint256) {
        return _divider_rate;
      }
  
      /**
        * @dev standard getter for total_distribution_balance
        */
      function total_distribution_balance() external view virtual returns (uint256) {
        return _total_distribution_balance;
      }
      
      /**
          * @dev standard getter for current_distribution_balance (ETH)
          */
      function current_distributed_balance() external view virtual returns (uint256) {
        return _current_distributed_balance;
      }
  
      /**
          * @dev Function that starts distribution.
          */
      function startDistribution() whenPaused external  {
        if(hasRole(DEFAULT_ADMIN_ROLE, msg.sender)==false) revert Unauthorized();
  
        _unpause();
      }
      
      /**
          * @dev Getter for the distribution state.
          */
      function distributionStarted() external view virtual returns (bool) {
        return !paused();
      }
      
      /**
          * @dev KYC signature check
          */
      function purchaseAllowed(bytes calldata proof, address from, uint256 validto) whenNotPaused public view virtual returns (bool) {
        if(_kyc_approver == address(0)) revert KYCNotSet();
        
        bytes32 expectedHash =
          hashForKYC(from, validto)
            .toEthSignedMessageHash();
            
        if(validto <= block.number) revert KYCTokenExpired();
  
        if(expectedHash.recover(proof) != _kyc_approver) revert InvalidKYCToken();
        
        return true;
      }
      
      function hashForKYC(address sender, uint256 validTo) public view returns (bytes32) {
          return keccak256(abi.encode(sender, validTo, block.chainid, address(this)));
      }
      
      /**
          * @dev Function that sets a new KYC Approver address
          */
      function changeKYCApprover(address newKYCApprover) external {
        if(false == hasRole(KYCMANAGER_ROLE, msg.sender)) revert Unauthorized();
          
        _kyc_approver = newKYCApprover;
  
        emit kycApproverChanged(newKYCApprover);
      }
      
      /**
          * @dev Function that calculates the current distribution rate based
          * on the inital distribution volume, the remaining volume and the
          * amount of erc20 tokens to be bought
          */
      function currentRateUndivided(uint256 amountWei) public view returns (uint256) {
              if(_current_distributed_balance + amountWei > _total_distribution_balance) revert DistributionOutOfRange();
          
              // Distribution active: descending or flat fractional linear rate (distribution slope)
              uint256 rateDelta =  
                _startrate_distribution.sub(_endrate_distribution);
              uint256 offset_e18 = _total_distribution_balance.sub(_current_distributed_balance); //.add(amountWei.div(2));
  
              uint256 currentRate = rateDelta
                .mul(offset_e18)
                .div(_total_distribution_balance)
                .add(_endrate_distribution);
              return currentRate;
      }
      
      /**
          * @dev Function that allows the beneficiary to retrieve
                the current fiat balance from the distribution contract
          */
      function claimFiatToken() external {
        if(msg.sender != _beneficiary) revert Unauthorized();
        
        _beneficiary.transfer(address(this).balance);
      }
      
      /**
          * @dev Function that is used to purchase tokens at the given rate.
            Calculates total number of tokens that can be bought for the given Ether
            Ether to the benificiary address
          * @param trustedtoken_amount number of gain tokens to purchase (wei)
          * @param purchaserate purchase tokens only at this rate (wei)
          * @param proof proof data for kyc validation
          * @param validTo expiry block for kyc proof
          */
      function purchaseTokens(
        uint256 trustedtoken_amount,
        uint256 purchaserate,
        bytes calldata proof,
        uint256 validTo) external payable {
        
        // anyone but contract admins must pass kyc
        if(hasRole(DEFAULT_ADMIN_ROLE, msg.sender)==false) {
          if(false==purchaseAllowed(proof, msg.sender, validTo)) revert PurchaseNotAllowed();
        }
  
        uint256 actualrate = currentRateUndivided(trustedtoken_amount);
        if(purchaserate>actualrate) revert CurrentRateExceedsLimit();
        if(purchaserate<actualrate.mul(90).div(100)) revert CurrentRateExceedsLimitSlippage();
        
        uint256 fiattoken_amount = trustedtoken_amount.mul(_divider_rate).div(purchaserate);
  
        uint256 pool_balance = _trusted_token.balanceOf(address(this));
        if(trustedtoken_amount>pool_balance) revert InsufficientTokensAvailable();
        
        _current_distributed_balance = _current_distributed_balance.add(trustedtoken_amount);
   
        if(msg.value != fiattoken_amount) revert FiatTransferFailed();
  
        _trusted_token.safeTransfer(msg.sender, trustedtoken_amount);
  
        emit TokensSold(msg.sender, msg.value, trustedtoken_amount, purchaserate);
      }
    }