creation_sourcecode: // SPDX-License-Identifier: AGPL-3.0-only
  pragma solidity 0.8.16;
  
  // File @openzeppelin/contracts/token/ERC20/IERC20.sol@v4.4.2
  
  
  
  // OpenZeppelin Contracts v4.4.1 (token/ERC20/IERC20.sol)
  
  
  /**
   * @dev Interface of the ERC20 standard as defined in the EIP.
   */
  interface IERC20 {
      /**
       * @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 `recipient`.
       *
       * Returns a boolean value indicating whether the operation succeeded.
       *
       * Emits a {Transfer} event.
       */
      function transfer(address recipient, 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 `sender` to `recipient` 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 sender,
          address recipient,
          uint256 amount
      ) external returns (bool);
  
      /**
       * @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);
  }
  
  
  // File @openzeppelin/contracts/token/ERC20/extensions/IERC20Metadata.sol@v4.4.2
  
  
  // OpenZeppelin Contracts v4.4.1 (token/ERC20/extensions/IERC20Metadata.sol)
  
  
  
  /**
   * @dev Interface for the optional metadata functions from the ERC20 standard.
   *
   * _Available since v4.1._
   */
  interface IERC20Metadata is IERC20 {
      /**
       * @dev Returns the name of the token.
       */
      function name() external view returns (string memory);
  
      /**
       * @dev Returns the symbol of the token.
       */
      function symbol() external view returns (string memory);
  
      /**
       * @dev Returns the decimals places of the token.
       */
      function decimals() external view returns (uint8);
  }
  
  
  // File @openzeppelin/contracts/utils/Context.sol@v4.4.2
  
  
  // OpenZeppelin Contracts v4.4.1 (utils/Context.sol)
  
  
  
  /**
   * @dev Provides information about the current execution context, including the
   * sender of the transaction and its data. While these are generally available
   * via msg.sender and msg.data, they should not be accessed in such a direct
   * manner, since when dealing with meta-transactions the account sending and
   * paying for execution may not be the actual sender (as far as an application
   * is concerned).
   *
   * This contract is only required for intermediate, library-like contracts.
   */
  abstract contract Context {
      function _msgSender() internal view virtual returns (address) {
          return msg.sender;
      }
  
      function _msgData() internal view virtual returns (bytes calldata) {
          return msg.data;
      }
  }
  
  
  // File @openzeppelin/contracts/token/ERC20/ERC20.sol@v4.4.2
  
  
  // OpenZeppelin Contracts v4.4.1 (token/ERC20/ERC20.sol)
  
  
  
  
  
  /**
   * @dev Implementation of the {IERC20} interface.
   *
   * This implementation is agnostic to the way tokens are created. This means
   * that a supply mechanism has to be added in a derived contract using {_mint}.
   * For a generic mechanism see {ERC20PresetMinterPauser}.
   *
   * TIP: For a detailed writeup see our guide
   * https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How
   * to implement supply mechanisms].
   *
   * We have followed general OpenZeppelin Contracts guidelines: functions revert
   * instead returning `false` on failure. This behavior is nonetheless
   * conventional and does not conflict with the expectations of ERC20
   * applications.
   *
   * Additionally, an {Approval} event is emitted on calls to {transferFrom}.
   * This allows applications to reconstruct the allowance for all accounts just
   * by listening to said events. Other implementations of the EIP may not emit
   * these events, as it isn't required by the specification.
   *
   * Finally, the non-standard {decreaseAllowance} and {increaseAllowance}
   * functions have been added to mitigate the well-known issues around setting
   * allowances. See {IERC20-approve}.
   */
  contract ERC20 is Context, IERC20, IERC20Metadata {
      mapping(address => uint256) private _balances;
  
      mapping(address => mapping(address => uint256)) private _allowances;
  
      uint256 private _totalSupply;
  
      string private _name;
      string private _symbol;
  
      /**
       * @dev Sets the values for {name} and {symbol}.
       *
       * The default value of {decimals} is 18. To select a different value for
       * {decimals} you should overload it.
       *
       * All two of these values are immutable: they can only be set once during
       * construction.
       */
      constructor(string memory name_, string memory symbol_) {
          _name = name_;
          _symbol = symbol_;
      }
  
      /**
       * @dev Returns the name of the token.
       */
      function name() public view virtual override returns (string memory) {
          return _name;
      }
  
      /**
       * @dev Returns the symbol of the token, usually a shorter version of the
       * name.
       */
      function symbol() public view virtual override returns (string memory) {
          return _symbol;
      }
  
      /**
       * @dev Returns the number of decimals used to get its user representation.
       * For example, if `decimals` equals `2`, a balance of `505` tokens should
       * be displayed to a user as `5.05` (`505 / 10 ** 2`).
       *
       * Tokens usually opt for a value of 18, imitating the relationship between
       * Ether and Wei. This is the value {ERC20} uses, unless this function is
       * overridden;
       *
       * NOTE: This information is only used for _display_ purposes: it in
       * no way affects any of the arithmetic of the contract, including
       * {IERC20-balanceOf} and {IERC20-transfer}.
       */
      function decimals() public view virtual override returns (uint8) {
          return 18;
      }
  
      /**
       * @dev See {IERC20-totalSupply}.
       */
      function totalSupply() public view virtual override returns (uint256) {
          return _totalSupply;
      }
  
      /**
       * @dev See {IERC20-balanceOf}.
       */
      function balanceOf(address account) public view virtual override returns (uint256) {
          return _balances[account];
      }
  
      /**
       * @dev See {IERC20-transfer}.
       *
       * Requirements:
       *
       * - `recipient` cannot be the zero address.
       * - the caller must have a balance of at least `amount`.
       */
      function transfer(address recipient, uint256 amount) public virtual override returns (bool) {
          _transfer(_msgSender(), recipient, amount);
          return true;
      }
  
      /**
       * @dev See {IERC20-allowance}.
       */
      function allowance(address owner, address spender) public view virtual override returns (uint256) {
          return _allowances[owner][spender];
      }
  
      /**
       * @dev See {IERC20-approve}.
       *
       * Requirements:
       *
       * - `spender` cannot be the zero address.
       */
      function approve(address spender, uint256 amount) public virtual override returns (bool) {
          _approve(_msgSender(), spender, amount);
          return true;
      }
  
      /**
       * @dev See {IERC20-transferFrom}.
       *
       * Emits an {Approval} event indicating the updated allowance. This is not
       * required by the EIP. See the note at the beginning of {ERC20}.
       *
       * Requirements:
       *
       * - `sender` and `recipient` cannot be the zero address.
       * - `sender` must have a balance of at least `amount`.
       * - the caller must have allowance for ``sender``'s tokens of at least
       * `amount`.
       */
      function transferFrom(
          address sender,
          address recipient,
          uint256 amount
      ) public virtual override returns (bool) {
          _transfer(sender, recipient, amount);
  
          uint256 currentAllowance = _allowances[sender][_msgSender()];
          require(currentAllowance >= amount, "ERC20: transfer amount exceeds allowance");
          unchecked {
              _approve(sender, _msgSender(), currentAllowance - amount);
          }
  
          return true;
      }
  
      /**
       * @dev Atomically increases the allowance granted to `spender` by the caller.
       *
       * This is an alternative to {approve} that can be used as a mitigation for
       * problems described in {IERC20-approve}.
       *
       * Emits an {Approval} event indicating the updated allowance.
       *
       * Requirements:
       *
       * - `spender` cannot be the zero address.
       */
      function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {
          _approve(_msgSender(), spender, _allowances[_msgSender()][spender] + addedValue);
          return true;
      }
  
      /**
       * @dev Atomically decreases the allowance granted to `spender` by the caller.
       *
       * This is an alternative to {approve} that can be used as a mitigation for
       * problems described in {IERC20-approve}.
       *
       * Emits an {Approval} event indicating the updated allowance.
       *
       * Requirements:
       *
       * - `spender` cannot be the zero address.
       * - `spender` must have allowance for the caller of at least
       * `subtractedValue`.
       */
      function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {
          uint256 currentAllowance = _allowances[_msgSender()][spender];
          require(currentAllowance >= subtractedValue, "ERC20: decreased allowance below zero");
          unchecked {
              _approve(_msgSender(), spender, currentAllowance - subtractedValue);
          }
  
          return true;
      }
  
      /**
       * @dev Moves `amount` of tokens from `sender` to `recipient`.
       *
       * This internal function is equivalent to {transfer}, and can be used to
       * e.g. implement automatic token fees, slashing mechanisms, etc.
       *
       * Emits a {Transfer} event.
       *
       * Requirements:
       *
       * - `sender` cannot be the zero address.
       * - `recipient` cannot be the zero address.
       * - `sender` must have a balance of at least `amount`.
       */
      function _transfer(
          address sender,
          address recipient,
          uint256 amount
      ) internal virtual {
          require(sender != address(0), "ERC20: transfer from the zero address");
          require(recipient != address(0), "ERC20: transfer to the zero address");
  
          _beforeTokenTransfer(sender, recipient, amount);
  
          uint256 senderBalance = _balances[sender];
          require(senderBalance >= amount, "ERC20: transfer amount exceeds balance");
          unchecked {
              _balances[sender] = senderBalance - amount;
          }
          _balances[recipient] += amount;
  
          emit Transfer(sender, recipient, amount);
  
          _afterTokenTransfer(sender, recipient, amount);
      }
  
      /** @dev Creates `amount` tokens and assigns them to `account`, increasing
       * the total supply.
       *
       * Emits a {Transfer} event with `from` set to the zero address.
       *
       * Requirements:
       *
       * - `account` cannot be the zero address.
       */
      function _mint(address account, uint256 amount) internal virtual {
          require(account != address(0), "ERC20: mint to the zero address");
  
          _beforeTokenTransfer(address(0), account, amount);
  
          _totalSupply += amount;
          _balances[account] += amount;
          emit Transfer(address(0), account, amount);
  
          _afterTokenTransfer(address(0), account, amount);
      }
  
      /**
       * @dev Destroys `amount` tokens from `account`, reducing the
       * total supply.
       *
       * Emits a {Transfer} event with `to` set to the zero address.
       *
       * Requirements:
       *
       * - `account` cannot be the zero address.
       * - `account` must have at least `amount` tokens.
       */
      function _burn(address account, uint256 amount) internal virtual {
          require(account != address(0), "ERC20: burn from the zero address");
  
          _beforeTokenTransfer(account, address(0), amount);
  
          uint256 accountBalance = _balances[account];
          require(accountBalance >= amount, "ERC20: burn amount exceeds balance");
          unchecked {
              _balances[account] = accountBalance - amount;
          }
          _totalSupply -= amount;
  
          emit Transfer(account, address(0), amount);
  
          _afterTokenTransfer(account, address(0), amount);
      }
  
      /**
       * @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens.
       *
       * This internal function is equivalent to `approve`, and can be used to
       * e.g. set automatic allowances for certain subsystems, etc.
       *
       * Emits an {Approval} event.
       *
       * Requirements:
       *
       * - `owner` cannot be the zero address.
       * - `spender` cannot be the zero address.
       */
      function _approve(
          address owner,
          address spender,
          uint256 amount
      ) internal virtual {
          require(owner != address(0), "ERC20: approve from the zero address");
          require(spender != address(0), "ERC20: approve to the zero address");
  
          _allowances[owner][spender] = amount;
          emit Approval(owner, spender, amount);
      }
  
      /**
       * @dev Hook that is called before any transfer of tokens. This includes
       * minting and burning.
       *
       * Calling conditions:
       *
       * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
       * will be transferred to `to`.
       * - when `from` is zero, `amount` tokens will be minted for `to`.
       * - when `to` is zero, `amount` of ``from``'s tokens will be burned.
       * - `from` and `to` are never both zero.
       *
       * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
       */
      function _beforeTokenTransfer(
          address from,
          address to,
          uint256 amount
      ) internal virtual {}
  
      /**
       * @dev Hook that is called after any transfer of tokens. This includes
       * minting and burning.
       *
       * Calling conditions:
       *
       * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
       * has been transferred to `to`.
       * - when `from` is zero, `amount` tokens have been minted for `to`.
       * - when `to` is zero, `amount` of ``from``'s tokens have been burned.
       * - `from` and `to` are never both zero.
       *
       * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
       */
      function _afterTokenTransfer(
          address from,
          address to,
          uint256 amount
      ) internal virtual {}
  }
  
  
  // File @openzeppelin/contracts/utils/math/Math.sol@v4.4.2
  
  
  // OpenZeppelin Contracts v4.4.1 (utils/math/Math.sol)
  
  
  
  /**
   * @dev Standard math utilities missing in the Solidity language.
   */
  library Math {
      /**
       * @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 / b + (a % b == 0 ? 0 : 1);
      }
  }
  
  
  // File @openzeppelin/contracts/utils/Arrays.sol@v4.4.2
  
  
  // OpenZeppelin Contracts v4.4.1 (utils/Arrays.sol)
  
  
  
  /**
   * @dev Collection of functions related to array types.
   */
  library Arrays {
      /**
       * @dev Searches a sorted `array` and returns the first index that contains
       * a value greater or equal to `element`. If no such index exists (i.e. all
       * values in the array are strictly less than `element`), the array length is
       * returned. Time complexity O(log n).
       *
       * `array` is expected to be sorted in ascending order, and to contain no
       * repeated elements.
       */
      function findUpperBound(uint256[] storage array, uint256 element) internal view returns (uint256) {
          if (array.length == 0) {
              return 0;
          }
  
          uint256 low = 0;
          uint256 high = array.length;
  
          while (low < high) {
              uint256 mid = Math.average(low, high);
  
              // Note that mid will always be strictly less than high (i.e. it will be a valid array index)
              // because Math.average rounds down (it does integer division with truncation).
              if (array[mid] > element) {
                  high = mid;
              } else {
                  low = mid + 1;
              }
          }
  
          // At this point `low` is the exclusive upper bound. We will return the inclusive upper bound.
          if (low > 0 && array[low - 1] == element) {
              return low - 1;
          } else {
              return low;
          }
      }
  }
  
  
  // File @openzeppelin/contracts/utils/Counters.sol@v4.4.2
  
  
  // OpenZeppelin Contracts v4.4.1 (utils/Counters.sol)
  
  
  
  /**
   * @title Counters
   * @author Matt Condon (@shrugs)
   * @dev Provides counters that can only be incremented, decremented or reset. This can be used e.g. to track the number
   * of elements in a mapping, issuing ERC721 ids, or counting request ids.
   *
   * Include with `using Counters for Counters.Counter;`
   */
  library Counters {
      struct Counter {
          // This variable should never be directly accessed by users of the library: interactions must be restricted to
          // the library's function. As of Solidity v0.5.2, this cannot be enforced, though there is a proposal to add
          // this feature: see https://github.com/ethereum/solidity/issues/4637
          uint256 _value; // default: 0
      }
  
      function current(Counter storage counter) internal view returns (uint256) {
          return counter._value;
      }
  
      function increment(Counter storage counter) internal {
          unchecked {
              counter._value += 1;
          }
      }
  
      function decrement(Counter storage counter) internal {
          uint256 value = counter._value;
          require(value > 0, "Counter: decrement overflow");
          unchecked {
              counter._value = value - 1;
          }
      }
  
      function reset(Counter storage counter) internal {
          counter._value = 0;
      }
  }
  
  
  // File @openzeppelin/contracts/token/ERC20/extensions/ERC20Snapshot.sol@v4.4.2
  
  
  // OpenZeppelin Contracts v4.4.1 (token/ERC20/extensions/ERC20Snapshot.sol)
  
  
  
  
  
  /**
   * @dev This contract extends an ERC20 token with a snapshot mechanism. When a snapshot is created, the balances and
   * total supply at the time are recorded for later access.
   *
   * This can be used to safely create mechanisms based on token balances such as trustless dividends or weighted voting.
   * In naive implementations it's possible to perform a "double spend" attack by reusing the same balance from different
   * accounts. By using snapshots to calculate dividends or voting power, those attacks no longer apply. It can also be
   * used to create an efficient ERC20 forking mechanism.
   *
   * Snapshots are created by the internal {_snapshot} function, which will emit the {Snapshot} event and return a
   * snapshot id. To get the total supply at the time of a snapshot, call the function {totalSupplyAt} with the snapshot
   * id. To get the balance of an account at the time of a snapshot, call the {balanceOfAt} function with the snapshot id
   * and the account address.
   *
   * NOTE: Snapshot policy can be customized by overriding the {_getCurrentSnapshotId} method. For example, having it
   * return `block.number` will trigger the creation of snapshot at the begining of each new block. When overridding this
   * function, be careful about the monotonicity of its result. Non-monotonic snapshot ids will break the contract.
   *
   * Implementing snapshots for every block using this method will incur significant gas costs. For a gas-efficient
   * alternative consider {ERC20Votes}.
   *
   * ==== Gas Costs
   *
   * Snapshots are efficient. Snapshot creation is _O(1)_. Retrieval of balances or total supply from a snapshot is _O(log
   * n)_ in the number of snapshots that have been created, although _n_ for a specific account will generally be much
   * smaller since identical balances in subsequent snapshots are stored as a single entry.
   *
   * There is a constant overhead for normal ERC20 transfers due to the additional snapshot bookkeeping. This overhead is
   * only significant for the first transfer that immediately follows a snapshot for a particular account. Subsequent
   * transfers will have normal cost until the next snapshot, and so on.
   */
  
  abstract contract ERC20Snapshot is ERC20 {
      // Inspired by Jordi Baylina's MiniMeToken to record historical balances:
      // https://github.com/Giveth/minimd/blob/ea04d950eea153a04c51fa510b068b9dded390cb/contracts/MiniMeToken.sol
  
      using Arrays for uint256[];
      using Counters for Counters.Counter;
  
      // Snapshotted values have arrays of ids and the value corresponding to that id. These could be an array of a
      // Snapshot struct, but that would impede usage of functions that work on an array.
      struct Snapshots {
          uint256[] ids;
          uint256[] values;
      }
  
      mapping(address => Snapshots) private _accountBalanceSnapshots;
      Snapshots private _totalSupplySnapshots;
  
      // Snapshot ids increase monotonically, with the first value being 1. An id of 0 is invalid.
      Counters.Counter private _currentSnapshotId;
  
      /**
       * @dev Emitted by {_snapshot} when a snapshot identified by `id` is created.
       */
      event Snapshot(uint256 id);
  
      /**
       * @dev Creates a new snapshot and returns its snapshot id.
       *
       * Emits a {Snapshot} event that contains the same id.
       *
       * {_snapshot} is `internal` and you have to decide how to expose it externally. Its usage may be restricted to a
       * set of accounts, for example using {AccessControl}, or it may be open to the public.
       *
       * [WARNING]
       * ====
       * While an open way of calling {_snapshot} is required for certain trust minimization mechanisms such as forking,
       * you must consider that it can potentially be used by attackers in two ways.
       *
       * First, it can be used to increase the cost of retrieval of values from snapshots, although it will grow
       * logarithmically thus rendering this attack ineffective in the long term. Second, it can be used to target
       * specific accounts and increase the cost of ERC20 transfers for them, in the ways specified in the Gas Costs
       * section above.
       *
       * We haven't measured the actual numbers; if this is something you're interested in please reach out to us.
       * ====
       */
      function _snapshot() internal virtual returns (uint256) {
          _currentSnapshotId.increment();
  
          uint256 currentId = _getCurrentSnapshotId();
          emit Snapshot(currentId);
          return currentId;
      }
  
      /**
       * @dev Get the current snapshotId
       */
      function _getCurrentSnapshotId() internal view virtual returns (uint256) {
          return _currentSnapshotId.current();
      }
  
      /**
       * @dev Retrieves the balance of `account` at the time `snapshotId` was created.
       */
      function balanceOfAt(address account, uint256 snapshotId) public view virtual returns (uint256) {
          (bool snapshotted, uint256 value) = _valueAt(snapshotId, _accountBalanceSnapshots[account]);
  
          return snapshotted ? value : balanceOf(account);
      }
  
      /**
       * @dev Retrieves the total supply at the time `snapshotId` was created.
       */
      function totalSupplyAt(uint256 snapshotId) public view virtual returns (uint256) {
          (bool snapshotted, uint256 value) = _valueAt(snapshotId, _totalSupplySnapshots);
  
          return snapshotted ? value : totalSupply();
      }
  
      // Update balance and/or total supply snapshots before the values are modified. This is implemented
      // in the _beforeTokenTransfer hook, which is executed for _mint, _burn, and _transfer operations.
      function _beforeTokenTransfer(
          address from,
          address to,
          uint256 amount
      ) internal virtual override {
          super._beforeTokenTransfer(from, to, amount);
  
          if (from == address(0)) {
              // mint
              _updateAccountSnapshot(to);
              _updateTotalSupplySnapshot();
          } else if (to == address(0)) {
              // burn
              _updateAccountSnapshot(from);
              _updateTotalSupplySnapshot();
          } else {
              // transfer
              _updateAccountSnapshot(from);
              _updateAccountSnapshot(to);
          }
      }
  
      function _valueAt(uint256 snapshotId, Snapshots storage snapshots) private view returns (bool, uint256) {
          require(snapshotId > 0, "ERC20Snapshot: id is 0");
          require(snapshotId <= _getCurrentSnapshotId(), "ERC20Snapshot: nonexistent id");
  
          // When a valid snapshot is queried, there are three possibilities:
          //  a) The queried value was not modified after the snapshot was taken. Therefore, a snapshot entry was never
          //  created for this id, and all stored snapshot ids are smaller than the requested one. The value that corresponds
          //  to this id is the current one.
          //  b) The queried value was modified after the snapshot was taken. Therefore, there will be an entry with the
          //  requested id, and its value is the one to return.
          //  c) More snapshots were created after the requested one, and the queried value was later modified. There will be
          //  no entry for the requested id: the value that corresponds to it is that of the smallest snapshot id that is
          //  larger than the requested one.
          //
          // In summary, we need to find an element in an array, returning the index of the smallest value that is larger if
          // it is not found, unless said value doesn't exist (e.g. when all values are smaller). Arrays.findUpperBound does
          // exactly this.
  
          uint256 index = snapshots.ids.findUpperBound(snapshotId);
  
          if (index == snapshots.ids.length) {
              return (false, 0);
          } else {
              return (true, snapshots.values[index]);
          }
      }
  
      function _updateAccountSnapshot(address account) private {
          _updateSnapshot(_accountBalanceSnapshots[account], balanceOf(account));
      }
  
      function _updateTotalSupplySnapshot() private {
          _updateSnapshot(_totalSupplySnapshots, totalSupply());
      }
  
      function _updateSnapshot(Snapshots storage snapshots, uint256 currentValue) private {
          uint256 currentId = _getCurrentSnapshotId();
          if (_lastSnapshotId(snapshots.ids) < currentId) {
              snapshots.ids.push(currentId);
              snapshots.values.push(currentValue);
          }
      }
  
      function _lastSnapshotId(uint256[] storage ids) private view returns (uint256) {
          if (ids.length == 0) {
              return 0;
          } else {
              return ids[ids.length - 1];
          }
      }
  }
  
  
  // File @openzeppelin/contracts/utils/Address.sol@v4.4.2
  
  
  // OpenZeppelin Contracts v4.4.1 (utils/Address.sol)
  
  
  
  /**
   * @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
       * ====
       */
      function isContract(address account) internal view returns (bool) {
          // This method relies on extcodesize, which returns 0 for contracts in
          // construction, since the code is only stored at the end of the
          // constructor execution.
  
          uint256 size;
          assembly {
              size := extcodesize(account)
          }
          return size > 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 functionCall(target, data, "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");
          require(isContract(target), "Address: call to non-contract");
  
          (bool success, bytes memory returndata) = target.call{value: value}(data);
          return verifyCallResult(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) {
          require(isContract(target), "Address: static call to non-contract");
  
          (bool success, bytes memory returndata) = target.staticcall(data);
          return verifyCallResult(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) {
          require(isContract(target), "Address: delegate call to non-contract");
  
          (bool success, bytes memory returndata) = target.delegatecall(data);
          return verifyCallResult(success, returndata, errorMessage);
      }
  
      /**
       * @dev Tool to verifies that a low level call was successful, and revert if it wasn't, either by bubbling the
       * revert reason 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 {
              // 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
  
                  assembly {
                      let returndata_size := mload(returndata)
                      revert(add(32, returndata), returndata_size)
                  }
              } else {
                  revert(errorMessage);
              }
          }
      }
  }
  
  
  // File @openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol@v4.4.2
  
  
  // OpenZeppelin Contracts v4.4.1 (token/ERC20/utils/SafeERC20.sol)
  
  
  
  
  /**
   * @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));
          }
      }
  
      /**
       * @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 contracts/common/implementation/MultiRole.sol
  
  
  
  
  library Exclusive {
      struct RoleMembership {
          address member;
      }
  
      function isMember(RoleMembership storage roleMembership, address memberToCheck) internal view returns (bool) {
          return roleMembership.member == memberToCheck;
      }
  
      function resetMember(RoleMembership storage roleMembership, address newMember) internal {
          require(newMember != address(0x0), "Cannot set an exclusive role to 0x0");
          roleMembership.member = newMember;
      }
  
      function getMember(RoleMembership storage roleMembership) internal view returns (address) {
          return roleMembership.member;
      }
  
      function init(RoleMembership storage roleMembership, address initialMember) internal {
          resetMember(roleMembership, initialMember);
      }
  }
  
  library Shared {
      struct RoleMembership {
          mapping(address => bool) members;
      }
  
      function isMember(RoleMembership storage roleMembership, address memberToCheck) internal view returns (bool) {
          return roleMembership.members[memberToCheck];
      }
  
      function addMember(RoleMembership storage roleMembership, address memberToAdd) internal {
          require(memberToAdd != address(0x0), "Cannot add 0x0 to a shared role");
          roleMembership.members[memberToAdd] = true;
      }
  
      function removeMember(RoleMembership storage roleMembership, address memberToRemove) internal {
          roleMembership.members[memberToRemove] = false;
      }
  
      function init(RoleMembership storage roleMembership, address[] memory initialMembers) internal {
          for (uint256 i = 0; i < initialMembers.length; i++) {
              addMember(roleMembership, initialMembers[i]);
          }
      }
  }
  
  /**
   * @title Base class to manage permissions for the derived class.
   */
  abstract contract MultiRole {
      using Exclusive for Exclusive.RoleMembership;
      using Shared for Shared.RoleMembership;
  
      enum RoleType { Invalid, Exclusive, Shared }
  
      struct Role {
          uint256 managingRole;
          RoleType roleType;
          Exclusive.RoleMembership exclusiveRoleMembership;
          Shared.RoleMembership sharedRoleMembership;
      }
  
      mapping(uint256 => Role) private roles;
  
      event ResetExclusiveMember(uint256 indexed roleId, address indexed newMember, address indexed manager);
      event AddedSharedMember(uint256 indexed roleId, address indexed newMember, address indexed manager);
      event RemovedSharedMember(uint256 indexed roleId, address indexed oldMember, address indexed manager);
  
      /**
       * @notice Reverts unless the caller is a member of the specified roleId.
       */
      modifier onlyRoleHolder(uint256 roleId) {
          require(holdsRole(roleId, msg.sender), "Sender does not hold required role");
          _;
      }
  
      /**
       * @notice Reverts unless the caller is a member of the manager role for the specified roleId.
       */
      modifier onlyRoleManager(uint256 roleId) {
          require(holdsRole(roles[roleId].managingRole, msg.sender), "Can only be called by a role manager");
          _;
      }
  
      /**
       * @notice Reverts unless the roleId represents an initialized, exclusive roleId.
       */
      modifier onlyExclusive(uint256 roleId) {
          require(roles[roleId].roleType == RoleType.Exclusive, "Must be called on an initialized Exclusive role");
          _;
      }
  
      /**
       * @notice Reverts unless the roleId represents an initialized, shared roleId.
       */
      modifier onlyShared(uint256 roleId) {
          require(roles[roleId].roleType == RoleType.Shared, "Must be called on an initialized Shared role");
          _;
      }
  
      /**
       * @notice Whether `memberToCheck` is a member of roleId.
       * @dev Reverts if roleId does not correspond to an initialized role.
       * @param roleId the Role to check.
       * @param memberToCheck the address to check.
       * @return True if `memberToCheck` is a member of `roleId`.
       */
      function holdsRole(uint256 roleId, address memberToCheck) public view returns (bool) {
          Role storage role = roles[roleId];
          if (role.roleType == RoleType.Exclusive) {
              return role.exclusiveRoleMembership.isMember(memberToCheck);
          } else if (role.roleType == RoleType.Shared) {
              return role.sharedRoleMembership.isMember(memberToCheck);
          }
          revert("Invalid roleId");
      }
  
      /**
       * @notice Changes the exclusive role holder of `roleId` to `newMember`.
       * @dev Reverts if the caller is not a member of the managing role for `roleId` or if `roleId` is not an
       * initialized, ExclusiveRole.
       * @param roleId the ExclusiveRole membership to modify.
       * @param newMember the new ExclusiveRole member.
       */
      function resetMember(uint256 roleId, address newMember) public onlyExclusive(roleId) onlyRoleManager(roleId) {
          roles[roleId].exclusiveRoleMembership.resetMember(newMember);
          emit ResetExclusiveMember(roleId, newMember, msg.sender);
      }
  
      /**
       * @notice Gets the current holder of the exclusive role, `roleId`.
       * @dev Reverts if `roleId` does not represent an initialized, exclusive role.
       * @param roleId the ExclusiveRole membership to check.
       * @return the address of the current ExclusiveRole member.
       */
      function getMember(uint256 roleId) public view onlyExclusive(roleId) returns (address) {
          return roles[roleId].exclusiveRoleMembership.getMember();
      }
  
      /**
       * @notice Adds `newMember` to the shared role, `roleId`.
       * @dev Reverts if `roleId` does not represent an initialized, SharedRole or if the caller is not a member of the
       * managing role for `roleId`.
       * @param roleId the SharedRole membership to modify.
       * @param newMember the new SharedRole member.
       */
      function addMember(uint256 roleId, address newMember) public onlyShared(roleId) onlyRoleManager(roleId) {
          roles[roleId].sharedRoleMembership.addMember(newMember);
          emit AddedSharedMember(roleId, newMember, msg.sender);
      }
  
      /**
       * @notice Removes `memberToRemove` from the shared role, `roleId`.
       * @dev Reverts if `roleId` does not represent an initialized, SharedRole or if the caller is not a member of the
       * managing role for `roleId`.
       * @param roleId the SharedRole membership to modify.
       * @param memberToRemove the current SharedRole member to remove.
       */
      function removeMember(uint256 roleId, address memberToRemove) public onlyShared(roleId) onlyRoleManager(roleId) {
          roles[roleId].sharedRoleMembership.removeMember(memberToRemove);
          emit RemovedSharedMember(roleId, memberToRemove, msg.sender);
      }
  
      /**
       * @notice Removes caller from the role, `roleId`.
       * @dev Reverts if the caller is not a member of the role for `roleId` or if `roleId` is not an
       * initialized, SharedRole.
       * @param roleId the SharedRole membership to modify.
       */
      function renounceMembership(uint256 roleId) public onlyShared(roleId) onlyRoleHolder(roleId) {
          roles[roleId].sharedRoleMembership.removeMember(msg.sender);
          emit RemovedSharedMember(roleId, msg.sender, msg.sender);
      }
  
      /**
       * @notice Reverts if `roleId` is not initialized.
       */
      modifier onlyValidRole(uint256 roleId) {
          require(roles[roleId].roleType != RoleType.Invalid, "Attempted to use an invalid roleId");
          _;
      }
  
      /**
       * @notice Reverts if `roleId` is initialized.
       */
      modifier onlyInvalidRole(uint256 roleId) {
          require(roles[roleId].roleType == RoleType.Invalid, "Cannot use a pre-existing role");
          _;
      }
  
      /**
       * @notice Internal method to initialize a shared role, `roleId`, which will be managed by `managingRoleId`.
       * `initialMembers` will be immediately added to the role.
       * @dev Should be called by derived contracts, usually at construction time. Will revert if the role is already
       * initialized.
       */
      function _createSharedRole(
          uint256 roleId,
          uint256 managingRoleId,
          address[] memory initialMembers
      ) internal onlyInvalidRole(roleId) {
          Role storage role = roles[roleId];
          role.roleType = RoleType.Shared;
          role.managingRole = managingRoleId;
          role.sharedRoleMembership.init(initialMembers);
          require(
              roles[managingRoleId].roleType != RoleType.Invalid,
              "Attempted to use an invalid role to manage a shared role"
          );
      }
  
      /**
       * @notice Internal method to initialize an exclusive role, `roleId`, which will be managed by `managingRoleId`.
       * `initialMember` will be immediately added to the role.
       * @dev Should be called by derived contracts, usually at construction time. Will revert if the role is already
       * initialized.
       */
      function _createExclusiveRole(
          uint256 roleId,
          uint256 managingRoleId,
          address initialMember
      ) internal onlyInvalidRole(roleId) {
          Role storage role = roles[roleId];
          role.roleType = RoleType.Exclusive;
          role.managingRole = managingRoleId;
          role.exclusiveRoleMembership.init(initialMember);
          require(
              roles[managingRoleId].roleType != RoleType.Invalid,
              "Attempted to use an invalid role to manage an exclusive role"
          );
      }
  }
  
  
  // File contracts/common/interfaces/ExpandedIERC20.sol
  
  
  
  
  /**
   * @title ERC20 interface that includes burn and mint methods.
   */
  abstract contract ExpandedIERC20 is IERC20 {
      /**
       * @notice Burns a specific amount of the caller's tokens.
       * @dev Only burns the caller's tokens, so it is safe to leave this method permissionless.
       */
      function burn(uint256 value) external virtual;
  
      /**
       * @dev Burns `value` tokens owned by `recipient`.
       * @param recipient address to burn tokens from.
       * @param value amount of tokens to burn.
       */
      function burnFrom(address recipient, uint256 value) external virtual returns (bool);
  
      /**
       * @notice Mints tokens and adds them to the balance of the `to` address.
       * @dev This method should be permissioned to only allow designated parties to mint tokens.
       */
      function mint(address to, uint256 value) external virtual returns (bool);
  
      function addMinter(address account) external virtual;
  
      function addBurner(address account) external virtual;
  
      function resetOwner(address account) external virtual;
  }
  
  
  // File contracts/common/implementation/ExpandedERC20.sol
  
  
  
  
  
  
  /**
   * @title An ERC20 with permissioned burning and minting. The contract deployer will initially
   * be the owner who is capable of adding new roles.
   */
  contract ExpandedERC20 is ExpandedIERC20, ERC20, MultiRole {
      enum Roles {
          // Can set the minter and burner.
          Owner,
          // Addresses that can mint new tokens.
          Minter,
          // Addresses that can burn tokens that address owns.
          Burner
      }
  
      uint8 _decimals;
  
      /**
       * @notice Constructs the ExpandedERC20.
       * @param _tokenName The name which describes the new token.
       * @param _tokenSymbol The ticker abbreviation of the name. Ideally < 5 chars.
       * @param _tokenDecimals The number of decimals to define token precision.
       */
      constructor(
          string memory _tokenName,
          string memory _tokenSymbol,
          uint8 _tokenDecimals
      ) ERC20(_tokenName, _tokenSymbol) {
          _decimals = _tokenDecimals;
          _createExclusiveRole(uint256(Roles.Owner), uint256(Roles.Owner), msg.sender);
          _createSharedRole(uint256(Roles.Minter), uint256(Roles.Owner), new address[](0));
          _createSharedRole(uint256(Roles.Burner), uint256(Roles.Owner), new address[](0));
      }
  
      function decimals() public view virtual override(ERC20) returns (uint8) {
          return _decimals;
      }
  
      /**
       * @dev Mints `value` tokens to `recipient`, returning true on success.
       * @param recipient address to mint to.
       * @param value amount of tokens to mint.
       * @return True if the mint succeeded, or False.
       */
      function mint(address recipient, uint256 value)
          external
          override
          onlyRoleHolder(uint256(Roles.Minter))
          returns (bool)
      {
          _mint(recipient, value);
          return true;
      }
  
      /**
       * @dev Burns `value` tokens owned by `msg.sender`.
       * @param value amount of tokens to burn.
       */
      function burn(uint256 value) external override onlyRoleHolder(uint256(Roles.Burner)) {
          _burn(msg.sender, value);
      }
  
      /**
       * @dev Burns `value` tokens owned by `recipient`.
       * @param recipient address to burn tokens from.
       * @param value amount of tokens to burn.
       * @return True if the burn succeeded, or False.
       */
      function burnFrom(address recipient, uint256 value)
          external
          override
          onlyRoleHolder(uint256(Roles.Burner))
          returns (bool)
      {
          _burn(recipient, value);
          return true;
      }
  
      /**
       * @notice Add Minter role to account.
       * @dev The caller must have the Owner role.
       * @param account The address to which the Minter role is added.
       */
      function addMinter(address account) external virtual override {
          addMember(uint256(Roles.Minter), account);
      }
  
      /**
       * @notice Add Burner role to account.
       * @dev The caller must have the Owner role.
       * @param account The address to which the Burner role is added.
       */
      function addBurner(address account) external virtual override {
          addMember(uint256(Roles.Burner), account);
      }
  
      /**
       * @notice Reset Owner role to account.
       * @dev The caller must have the Owner role.
       * @param account The new holder of the Owner role.
       */
      function resetOwner(address account) external virtual override {
          resetMember(uint256(Roles.Owner), account);
      }
  }
  
  
  // File contracts/common/implementation/Withdrawable.sol
  
  /**
   * Withdrawable contract.
   */
  
  
  
  
  
  
  /**
   * @title Base contract that allows a specific role to withdraw any ETH and/or ERC20 tokens that the contract holds.
   */
  abstract contract Withdrawable is MultiRole {
      using SafeERC20 for IERC20;
  
      uint256 private roleId;
  
      /**
       * @notice Withdraws ETH from the contract.
       */
      function withdraw(uint256 amount) external onlyRoleHolder(roleId) {
          Address.sendValue(payable(msg.sender), amount);
      }
  
      /**
       * @notice Withdraws ERC20 tokens from the contract.
       * @param erc20Address ERC20 token to withdraw.
       * @param amount amount of tokens to withdraw.
       */
      function withdrawErc20(address erc20Address, uint256 amount) external onlyRoleHolder(roleId) {
          IERC20 erc20 = IERC20(erc20Address);
          erc20.safeTransfer(msg.sender, amount);
      }
  
      /**
       * @notice Internal method that allows derived contracts to create a role for withdrawal.
       * @dev Either this method or `_setWithdrawRole` must be called by the derived class for this contract to function
       * properly.
       * @param newRoleId ID corresponding to role whose members can withdraw.
       * @param managingRoleId ID corresponding to managing role who can modify the withdrawable role's membership.
       * @param withdrawerAddress new manager of withdrawable role.
       */
      function _createWithdrawRole(
          uint256 newRoleId,
          uint256 managingRoleId,
          address withdrawerAddress
      ) internal {
          roleId = newRoleId;
          _createExclusiveRole(newRoleId, managingRoleId, withdrawerAddress);
      }
  
      /**
       * @notice Internal method that allows derived contracts to choose the role for withdrawal.
       * @dev The role `setRoleId` must exist. Either this method or `_createWithdrawRole` must be
       * called by the derived class for this contract to function properly.
       * @param setRoleId ID corresponding to role whose members can withdraw.
       */
      function _setWithdrawRole(uint256 setRoleId) internal onlyValidRole(setRoleId) {
          roleId = setRoleId;
      }
  }
  
  
  // File contracts/data-verification-mechanism/implementation/VotingToken.sol
  
  
  
  
  
  /**
   * @title Ownership of this token allows a voter to respond to price requests.
   * @dev Supports snapshotting and allows the Oracle to mint new tokens as rewards.
   */
  contract VotingToken is ExpandedERC20, ERC20Snapshot {
      /**
       * @notice Constructs the VotingToken.
       */
      constructor() ExpandedERC20("UMA Voting Token v1", "UMA", 18) ERC20Snapshot() {}
  
      function decimals() public view virtual override(ERC20, ExpandedERC20) returns (uint8) {
          return super.decimals();
      }
  
      /**
       * @notice Creates a new snapshot ID.
       * @return uint256 Thew new snapshot ID.
       */
      function snapshot() external returns (uint256) {
          return _snapshot();
      }
  
      // _transfer, _mint and _burn are ERC20 internal methods that are overridden by ERC20Snapshot,
      // therefore the compiler will complain that VotingToken must override these methods
      // because the two base classes (ERC20 and ERC20Snapshot) both define the same functions
  
      function _transfer(
          address from,
          address to,
          uint256 value
      ) internal override(ERC20) {
          super._transfer(from, to, value);
      }
  
      function _mint(address account, uint256 value) internal virtual override(ERC20) {
          super._mint(account, value);
      }
  
      function _burn(address account, uint256 value) internal virtual override(ERC20) {
          super._burn(account, value);
      }
  
      function _beforeTokenTransfer(
          address from,
          address to,
          uint256 amount
      ) internal virtual override(ERC20, ERC20Snapshot) {
          super._beforeTokenTransfer(from, to, amount);
      }
  }
  
  
  // File contracts/data-verification-mechanism/interfaces/StakerInterface.sol
  
  
  
  
  
  interface StakerInterface {
      function votingToken() external returns (ExpandedIERC20);
  
      function stake(uint128 amount) external;
  
      function requestUnstake(uint128 amount) external;
  
      function executeUnstake() external;
  
      function withdrawRewards() external returns (uint128);
  
      function withdrawAndRestake() external returns (uint128);
  
      function setEmissionRate(uint128 newEmissionRate) external;
  
      function setUnstakeCoolDown(uint64 newUnstakeCoolDown) external;
  
      /**
       * @notice Sets the delegate of a voter. This delegate can vote on behalf of the staker. The staker will still own
       * all staked balances, receive rewards and be slashed based on the actions of the delegate. Intended use is using a
       * low-security available wallet for voting while keeping access to staked amounts secure by a more secure wallet.
       * @param delegate the address of the delegate.
       */
      function setDelegate(address delegate) external virtual;
  
      /**
       * @notice Sets the delegator of a voter. Acts to accept a delegation. The delegate can only vote for the delegator
       * if the delegator also selected the delegate to do so (two-way relationship needed).
       * @param delegator the address of the delegator.
       */
      function setDelegator(address delegator) external virtual;
  }
  
  
  // File contracts/common/implementation/Stakeable.sol
  
  /**
   * Stakeable contract.
   */
  
  
  
  
  
  /**
   * @title Base contract that extends the Withdrawable contract enabling a specific role to stake ERC20 tokens against the
   * Voting contract. Voting contract is fed in as a param rather than fetched from the finder to enable upgradability.
   */
  abstract contract Stakeable is Withdrawable {
      using SafeERC20 for IERC20;
  
      uint256 private roleId;
  
      /**
       * @notice Stake ERC20 tokens from this contract to the votingContract.
       * @param amount amount of tokens to stake.
       * @param votingContract Address of the voting contract to stake into.
       */
      function stake(uint128 amount, address votingContract) external onlyRoleHolder(roleId) {
          StakerInterface voting = StakerInterface(votingContract);
          IERC20 votingToken = IERC20(voting.votingToken());
          votingToken.approve(votingContract, amount);
          voting.stake(amount);
      }
  
      /**
       * @notice Request unstaking of ERC20 tokens from this contract to the votingContract.
       * @param amount amount of tokens to unstake.
       * @param votingContract Address of the voting contract to unstake from.
       */
      function requestUnstake(uint128 amount, address votingContract) external onlyRoleHolder(roleId) {
          StakerInterface voting = StakerInterface(votingContract);
          voting.requestUnstake(amount);
      }
  
      /**
       * @notice Execute an unstake request that has passed liveness on the voting contract.
       * @param votingContract Address of the voting contract to execute the unstake from.
       */
      function executeUnstake(address votingContract) external onlyRoleHolder(roleId) {
          StakerInterface voting = StakerInterface(votingContract);
          voting.executeUnstake();
      }
  
      /**
       * @notice Internal method that allows derived contracts to choose the role for stakeable.
       * @dev The role `setRoleId` must exist. Either this method or `_setStakeRole` must be
       * called by the derived class for this contract to function properly.
       * @param setRoleId ID corresponding to role whose members can stakeable.
       */
      function _setStakeRole(uint256 setRoleId) internal onlyValidRole(setRoleId) {
          roleId = setRoleId;
      }
  }
  
  
  // File contracts/common/implementation/MultiCaller.sol
  
  
  
  
  // This contract is taken from Uniswap's multi call implementation (https://github.com/Uniswap/uniswap-v3-periphery/blob/main/contracts/base/Multicall.sol)
  // and was modified to be solidity 0.8 compatible. Additionally, the method was restricted to only work with msg.value
  // set to 0 to avoid any nasty attack vectors on function calls that use value sent with deposits.
  
  /// @title MultiCaller
  /// @notice Enables calling multiple methods in a single call to the contract
  contract MultiCaller {
      function multicall(bytes[] calldata data) external returns (bytes[] memory results) {
          results = new bytes[](data.length);
          for (uint256 i = 0; i < data.length; i++) {
              (bool success, bytes memory result) = address(this).delegatecall(data[i]);
  
              if (!success) {
                  // Next 5 lines from https://ethereum.stackexchange.com/a/83577
                  if (result.length < 68) revert();
                  assembly {
                      result := add(result, 0x04)
                  }
                  revert(abi.decode(result, (string)));
              }
  
              results[i] = result;
          }
      }
  }
  
  
  // File contracts/data-verification-mechanism/implementation/Constants.sol
  
  
  
  
  /**
   * @title Stores common interface names used throughout the DVM by registration in the Finder.
   */
  library OracleInterfaces {
      bytes32 public constant Oracle = "Oracle";
      bytes32 public constant IdentifierWhitelist = "IdentifierWhitelist";
      bytes32 public constant Store = "Store";
      bytes32 public constant FinancialContractsAdmin = "FinancialContractsAdmin";
      bytes32 public constant Registry = "Registry";
      bytes32 public constant CollateralWhitelist = "CollateralWhitelist";
      bytes32 public constant OptimisticOracle = "OptimisticOracle";
      bytes32 public constant OptimisticOracleV2 = "OptimisticOracleV2";
      bytes32 public constant Bridge = "Bridge";
      bytes32 public constant GenericHandler = "GenericHandler";
      bytes32 public constant SkinnyOptimisticOracle = "SkinnyOptimisticOracle";
      bytes32 public constant ChildMessenger = "ChildMessenger";
      bytes32 public constant OracleHub = "OracleHub";
      bytes32 public constant OracleSpoke = "OracleSpoke";
      bytes32 public constant OptimisticOracleV3 = "OptimisticOracleV3";
  }
  
  /**
   * @title Commonly re-used values for contracts associated with the OptimisticOracle.
   */
  library OptimisticOracleConstraints {
      // Any price request submitted to the OptimisticOracle must contain ancillary data no larger than this value.
      // This value must be <= the Voting contract's `ancillaryBytesLimit` constant value otherwise it is possible
      // that a price can be requested to the OptimisticOracle successfully, but cannot be resolved by the DVM which
      // refuses to accept a price request made with ancillary data length over a certain size.
      uint256 public constant ancillaryBytesLimit = 8192;
  }
  
  
  // File contracts/data-verification-mechanism/interfaces/FinderInterface.sol
  
  
  
  
  /**
   * @title Provides addresses of the live contracts implementing certain interfaces.
   * @dev Examples are the Oracle or Store interfaces.
   */
  interface FinderInterface {
      /**
       * @notice Updates the address of the contract that implements `interfaceName`.
       * @param interfaceName bytes32 encoding of the interface name that is either changed or registered.
       * @param implementationAddress address of the deployed contract that implements the interface.
       */
      function changeImplementationAddress(bytes32 interfaceName, address implementationAddress) external;
  
      /**
       * @notice Gets the address of the contract that implements the given `interfaceName`.
       * @param interfaceName queried interface.
       * @return implementationAddress address of the deployed contract that implements the interface.
       */
      function getImplementationAddress(bytes32 interfaceName) external view returns (address);
  }
  
  
  // File contracts/data-verification-mechanism/implementation/DesignatedVotingV2.sol
  
  
  
  /**
   * @title Proxy to allow voting from another address.
   * @dev Allows a UMA token holder to designate another address to vote on their behalf.
   * Each voter must deploy their own instance of this contract.
   */
  contract DesignatedVotingV2 is Stakeable, MultiCaller {
      /****************************************
       *    INTERNAL VARIABLES AND STORAGE    *
       ****************************************/
  
      enum Roles {
          Owner, // Can set the Voter role.
          Voter // Can vote through this contract.
      }
  
      // Reference to UMA Finder contract, allowing Voting upgrades to be without requiring any calls to this contract.
      FinderInterface public immutable finder;
  
      /**
       * @notice Construct the DesignatedVotingV2 contract.
       * @param finderAddress keeps track of all contracts within the system based on their interfaceName.
       * @param ownerAddress address of the owner of the DesignatedVotingV2 contract.
       * @param voterAddress address to which the owner has delegated their voting power.
       */
      constructor(
          address finderAddress,
          address ownerAddress,
          address voterAddress
      ) {
          _createExclusiveRole(uint256(Roles.Owner), uint256(Roles.Owner), ownerAddress);
          _createExclusiveRole(uint256(Roles.Voter), uint256(Roles.Owner), voterAddress);
          _setWithdrawRole(uint256(Roles.Owner));
          _setStakeRole(uint256(Roles.Owner));
  
          finder = FinderInterface(finderAddress);
      }
  
      /**
       * @notice This method essentially syncs the voter role with the current voting delegate.
       * @dev Because this is essentially a state sync method, there is no reason to restrict its permissioning.
       */
      function delegateToVoter() public {
          address voter = getMember(uint256(Roles.Voter));
          _getVotingContract().setDelegate(voter);
      }
  
      // Returns the Voting contract address, named "Oracle" in the finder.
      function _getVotingContract() private view returns (StakerInterface) {
          return StakerInterface(finder.getImplementationAddress(OracleInterfaces.Oracle));
      }
  }