// File: contracts/assets/erc20/Token.sol



// SPDX-License-Identifier: GPL-3.0
pragma solidity ^0.8.7;

import "@openzeppelin/contracts/token/ERC20/extensions/ERC20Capped.sol";
import "@openzeppelin/contracts/access/Ownable.sol";

/**
  @title A basic ERC-20 token with voting functionality.
  @author Tim Clancy

  This contract is used when deploying SuperFarm ERC-20 tokens.
  This token is created with a fixed, immutable cap and includes voting rights.
  Voting functionality is copied and modified from Sushi, and in turn from YAM:
  https://github.com/yam-finance/yam-protocol/blob/master/contracts/token/YAMGovernanceStorage.sol
  https://github.com/yam-finance/yam-protocol/blob/master/contracts/token/YAMGovernance.sol
  Which is in turn copied and modified from COMPOUND:
  https://github.com/compound-finance/compound-protocol/blob/master/contracts/Governance/Comp.sol
*/
contract Token is ERC20Capped, Ownable {

  /// A version number for this Token contract's interface.
  uint256 public version = 1;

  /**
    Construct a new Token by providing it a name, ticker, and supply cap.

    @param _name The name of the new Token.
    @param _ticker The ticker symbol of the new Token.
    @param _cap The supply cap of the new Token.
  */
  constructor (string memory _name, string memory _ticker, uint256 _cap) ERC20(_name, _ticker) ERC20Capped(_cap) { }

  /**
   * @dev Destroys `amount` tokens from the caller.
   *
   * See {ERC20-_burn}.
   */
  function burn(uint256 amount) public virtual {
      _burn(_msgSender(), amount);
  }

  /**
   * @dev Destroys `amount` tokens from `account`, deducting from the caller's
   * allowance.
   *
   * See {ERC20-_burn} and {ERC20-allowance}.
   *
   * Requirements:
   *
   * - the caller must have allowance for ``accounts``'s tokens of at least
   * `amount`.
   */
  function burnFrom(address account, uint256 amount) public virtual {
      require(amount >= allowance(account, _msgSender()),
        "ERC20: burn amount exceeds allowance");
      uint256 decreasedAllowance = allowance(account, _msgSender()) - amount;

      _approve(account, _msgSender(), decreasedAllowance);
      _burn(account, amount);
  }

  /**
    Allows Token creator to mint `_amount` of this Token to the address `_to`.
    New tokens of this Token cannot be minted if it would exceed the supply cap.
    Users are delegated votes when they are minted Token.

    @param _to the address to mint Tokens to.
    @param _amount the amount of new Token to mint.
  */
  function mint(address _to, uint256 _amount) external onlyOwner {
    _mint(_to, _amount);
    _moveDelegates(address(0), _delegates[_to], _amount);
  }

  /**
    Allows users to transfer tokens to a recipient, moving delegated votes with
    the transfer.

    @param recipient The address to transfer tokens to.
    @param amount The amount of tokens to send to `recipient`.
  */
  function transfer(address recipient, uint256 amount) public override returns (bool) {
    _transfer(_msgSender(), recipient, amount);
    _moveDelegates(_delegates[msg.sender], _delegates[recipient], amount);
    return true;
  }

  /// @dev A mapping to record delegates for each address.
  mapping (address => address) internal _delegates;

  /// A checkpoint structure to mark some number of votes from a given block.
  struct Checkpoint {
    uint32 fromBlock;
    uint256 votes;
  }

  /// A mapping to record indexed Checkpoint votes for each address.
  mapping (address => mapping (uint32 => Checkpoint)) public checkpoints;

  /// A mapping to record the number of Checkpoints for each address.
  mapping (address => uint32) public numCheckpoints;

  /// The EIP-712 typehash for the contract's domain.
  bytes32 public constant DOMAIN_TYPEHASH = keccak256("EIP712Domain(string name,uint256 chainId,address verifyingContract)");

  /// The EIP-712 typehash for the delegation struct used by the contract.
  bytes32 public constant DELEGATION_TYPEHASH = keccak256("Delegation(address delegatee,uint256 nonce,uint256 expiry)");

  /// A mapping to record per-address states for signing / validating signatures.
  mapping (address => uint) public nonces;

  /// An event emitted when an address changes its delegate.
  event DelegateChanged(address indexed delegator, address indexed fromDelegate, address indexed toDelegate);

  /// An event emitted when the vote balance of a delegated address changes.
  event DelegateVotesChanged(address indexed delegate, uint previousBalance, uint newBalance);

  /**
    Return the address delegated to by `delegator`.

    @return The address delegated to by `delegator`.
  */
  function delegates(address delegator) external view returns (address) {
    return _delegates[delegator];
  }

  /**
    Delegate votes from `msg.sender` to `delegatee`.

    @param delegatee The address to delegate votes to.
  */
  function delegate(address delegatee) external {
    return _delegate(msg.sender, delegatee);
  }

  /**
    Delegate votes from signatory to `delegatee`.

    @param delegatee The address to delegate votes to.
    @param nonce The contract state required for signature matching.
    @param expiry The time at which to expire the signature.
    @param v The recovery byte of the signature.
    @param r Half of the ECDSA signature pair.
    @param s Half of the ECDSA signature pair.
  */
  function delegateBySig(address delegatee, uint nonce, uint expiry, uint8 v, bytes32 r, bytes32 s) external {
    bytes32 domainSeparator = keccak256(
      abi.encode(
        DOMAIN_TYPEHASH,
        keccak256(bytes(name())),
        getChainId(),
        address(this)));

    bytes32 structHash = keccak256(
      abi.encode(
          DELEGATION_TYPEHASH,
          delegatee,
          nonce,
          expiry));

    bytes32 digest = keccak256(
      abi.encodePacked(
        "\x19\x01",
        domainSeparator,
        structHash));

    address signatory = ecrecover(digest, v, r, s);
    require(signatory != address(0), "Invalid signature.");
    require(nonce == nonces[signatory]++, "Invalid nonce.");
    require(block.timestamp <= expiry, "Signature expired.");
    return _delegate(signatory, delegatee);
  }

  /**
    Get the current votes balance for the address `account`.

    @param account The address to get the votes balance of.
    @return The number of current votes for `account`.
  */
  function getCurrentVotes(address account) external view returns (uint256) {
    uint32 nCheckpoints = numCheckpoints[account];
    return nCheckpoints > 0 ? checkpoints[account][nCheckpoints - 1].votes : 0;
  }

  /**
    Determine the prior number of votes for an address as of a block number.

    @dev The block number must be a finalized block or else this function will revert to prevent misinformation.
    @param account The address to check.
    @param blockNumber The block number to get the vote balance at.
    @return The number of votes the account had as of the given block.
  */
  function getPriorVotes(address account, uint blockNumber) external view returns (uint256) {
    require(blockNumber < block.number, "The specified block is not yet finalized.");

    uint32 nCheckpoints = numCheckpoints[account];
    if (nCheckpoints == 0) {
      return 0;
    }

    // First check the most recent balance.
    if (checkpoints[account][nCheckpoints - 1].fromBlock <= blockNumber) {
      return checkpoints[account][nCheckpoints - 1].votes;
    }

    // Then check the implicit zero balance.
    if (checkpoints[account][0].fromBlock > blockNumber) {
      return 0;
    }

    uint32 lower = 0;
    uint32 upper = nCheckpoints - 1;
    while (upper > lower) {
      uint32 center = upper - (upper - lower) / 2; // ceil, avoiding overflow
      Checkpoint memory cp = checkpoints[account][center];
      if (cp.fromBlock == blockNumber) {
        return cp.votes;
      } else if (cp.fromBlock < blockNumber) {
        lower = center;
      } else {
        upper = center - 1;
      }
    }
    return checkpoints[account][lower].votes;
  }

  /**
    An internal function to actually perform the delegation of votes.

    @param delegator The address delegating to `delegatee`.
    @param delegatee The address receiving delegated votes.
  */
  function _delegate(address delegator, address delegatee) internal {
    address currentDelegate = _delegates[delegator];
    uint256 delegatorBalance = balanceOf(delegator);
    _delegates[delegator] = delegatee;
    /* console.log('a-', currentDelegate, delegator, delegatee); */
    emit DelegateChanged(delegator, currentDelegate, delegatee);

    _moveDelegates(currentDelegate, delegatee, delegatorBalance);
  }

  /**
    An internal function to move delegated vote amounts between addresses.

    @param srcRep the previous representative who received delegated votes.
    @param dstRep the new representative to receive these delegated votes.
    @param amount the amount of delegated votes to move between representatives.
  */
  function _moveDelegates(address srcRep, address dstRep, uint256 amount) internal {
    if (srcRep != dstRep && amount > 0) {

      // Decrease the number of votes delegated to the previous representative.
      if (srcRep != address(0)) {
        uint32 srcRepNum = numCheckpoints[srcRep];
        uint256 srcRepOld = srcRepNum > 0 ? checkpoints[srcRep][srcRepNum - 1].votes : 0;
        uint256 srcRepNew = srcRepOld - amount;
        _writeCheckpoint(srcRep, srcRepNum, srcRepOld, srcRepNew);
      }

      // Increase the number of votes delegated to the new representative.
      if (dstRep != address(0)) {
        uint32 dstRepNum = numCheckpoints[dstRep];
        uint256 dstRepOld = dstRepNum > 0 ? checkpoints[dstRep][dstRepNum - 1].votes : 0;
        uint256 dstRepNew = dstRepOld + amount;
        _writeCheckpoint(dstRep, dstRepNum, dstRepOld, dstRepNew);
      }
    }
  }

  /**
    An internal function to write a checkpoint of modified vote amounts.
    This function is guaranteed to add at most one checkpoint per block.

    @param delegatee The address whose vote count is changed.
    @param nCheckpoints The number of checkpoints by address `delegatee`.
    @param oldVotes The prior vote count of address `delegatee`.
    @param newVotes The new vote count of address `delegatee`.
  */
  function _writeCheckpoint(address delegatee, uint32 nCheckpoints, uint256 oldVotes, uint256 newVotes) internal {
    uint32 blockNumber = safe32(block.number, "Block number exceeds 32 bits.");

    if (nCheckpoints > 0 && checkpoints[delegatee][nCheckpoints - 1].fromBlock == blockNumber) {
      checkpoints[delegatee][nCheckpoints - 1].votes = newVotes;
    } else {
      checkpoints[delegatee][nCheckpoints] = Checkpoint(blockNumber, newVotes);
      numCheckpoints[delegatee] = nCheckpoints + 1;
    }

    emit DelegateVotesChanged(delegatee, oldVotes, newVotes);
  }

  /**
    A function to safely limit a number to less than 2^32.

    @param n the number to limit.
    @param errorMessage the error message to revert with should `n` be too large.
    @return The number `n` limited to 32 bits.
  */
  function safe32(uint n, string memory errorMessage) internal pure returns (uint32) {
    require(n < 2**32, errorMessage);
    return uint32(n);
  }

  /**
    A function to return the ID of the contract's particular network or chain.

    @return The ID of the contract's network or chain.
  */
  function getChainId() internal view returns (uint) {
    uint256 chainId;
    assembly { chainId := chainid() }
    return chainId;
  }
}
// File: @openzeppelin/contracts/token/ERC20/extensions/ERC20Capped.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/extensions/ERC20Capped.sol)

pragma solidity ^0.8.0;

import "../ERC20.sol";

/**
 * @dev Extension of {ERC20} that adds a cap to the supply of tokens.
 */
abstract contract ERC20Capped is ERC20 {
    uint256 private immutable _cap;

    /**
     * @dev Sets the value of the `cap`. This value is immutable, it can only be
     * set once during construction.
     */
    constructor(uint256 cap_) {
        require(cap_ > 0, "ERC20Capped: cap is 0");
        _cap = cap_;
    }

    /**
     * @dev Returns the cap on the token's total supply.
     */
    function cap() public view virtual returns (uint256) {
        return _cap;
    }

    /**
     * @dev See {ERC20-_mint}.
     */
    function _mint(address account, uint256 amount) internal virtual override {
        require(ERC20.totalSupply() + amount <= cap(), "ERC20Capped: cap exceeded");
        super._mint(account, amount);
    }
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (access/Ownable.sol)

pragma solidity ^0.8.0;

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

/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
    address private _owner;

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

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

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
        _;
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        _transferOwnership(address(0));
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.6.0) (token/ERC20/ERC20.sol)

pragma solidity ^0.8.0;

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

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

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

    uint256 private _totalSupply;

    string private _name;
    string private _symbol;

    /**
     * @dev Sets the values for {name} and {symbol}.
     *
     * The default value of {decimals} is 18. To select a different value for
     * {decimals} you should overload it.
     *
     * All two of these values are immutable: they can only be set once during
     * construction.
     */
    constructor(string memory name_, string memory symbol_) {
        _name = name_;
        _symbol = symbol_;
    }

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

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

    /**
     * @dev Returns the number of decimals used to get its user representation.
     * For example, if `decimals` equals `2`, a balance of `505` tokens should
     * be displayed to a user as `5.05` (`505 / 10 ** 2`).
     *
     * Tokens usually opt for a value of 18, imitating the relationship between
     * Ether and Wei. This is the value {ERC20} uses, unless this function is
     * overridden;
     *
     * NOTE: This information is only used for _display_ purposes: it in
     * no way affects any of the arithmetic of the contract, including
     * {IERC20-balanceOf} and {IERC20-transfer}.
     */
    function decimals() public view virtual override returns (uint8) {
        return 18;
    }

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

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

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

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

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

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

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

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

        return true;
    }

    /**
     * @dev Moves `amount` of tokens from `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:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `from` must have a balance of at least `amount`.
     */
    function _transfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {
        require(from != address(0), "ERC20: transfer from the zero address");
        require(to != address(0), "ERC20: transfer to the zero address");

        _beforeTokenTransfer(from, to, amount);

        uint256 fromBalance = _balances[from];
        require(fromBalance >= amount, "ERC20: transfer amount exceeds balance");
        unchecked {
            _balances[from] = fromBalance - amount;
        }
        _balances[to] += amount;

        emit Transfer(from, to, amount);

        _afterTokenTransfer(from, to, amount);
    }

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

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

        _totalSupply += amount;
        _balances[account] += amount;
        emit Transfer(address(0), account, amount);

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

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

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

        uint256 accountBalance = _balances[account];
        require(accountBalance >= amount, "ERC20: burn amount exceeds balance");
        unchecked {
            _balances[account] = accountBalance - amount;
        }
        _totalSupply -= amount;

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

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

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

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

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

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

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

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.6.0) (token/ERC20/IERC20.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);

    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

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

    /**
     * @dev Moves `amount` tokens from the caller's account to `to`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address to, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `from` to `to` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(
        address from,
        address to,
        uint256 amount
    ) external returns (bool);
}

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



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

pragma solidity ^0.8.0;

import "../IERC20.sol";

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

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

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

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/Context.sol)

pragma solidity ^0.8.0;

/**
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }
}