// Vulnerability label: DC1
pragma solidity 0.5.16;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP. Does not include
 * the optional functions; to access them see `ERC20Detailed`.
 */
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.
     *
     * > 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);
}

/**
 * @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 `ERC20Mintable`.
 *
 * *For a detailed writeup see our guide [How to implement supply
 * mechanisms](https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226).*
 *
 * We have followed general OpenZeppelin guidelines: functions revert instead
 * of 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 IERC20 {
    using SafeMath for uint256;

    mapping (address => uint256) private _balances;

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

    uint256 private _totalSupply;

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

    /**
     * @dev See `IERC20.balanceOf`.
     */
    function balanceOf(address account) public view 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 returns (bool) {
        _transfer(msg.sender, recipient, amount);
        return true;
    }

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

    /**
     * @dev See `IERC20.approve`.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 value) public returns (bool) {
        _approve(msg.sender, spender, value);
        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 `value`.
     * - the caller must have allowance for `sender`'s tokens of at least
     * `amount`.
     */
    function transferFrom(address sender, address recipient, uint256 amount) public returns (bool) {
        _transfer(sender, recipient, amount);
        _approve(sender, msg.sender, _allowances[sender][msg.sender].sub(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 returns (bool) {
        _approve(msg.sender, spender, _allowances[msg.sender][spender].add(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 returns (bool) {
        _approve(msg.sender, spender, _allowances[msg.sender][spender].sub(subtractedValue));
        return true;
    }

    /**
     * @dev Moves tokens `amount` from `sender` to `recipient`.
     *
     * This is 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 {
        require(sender != address(0), "ERC20: transfer from the zero address");
        require(recipient != address(0), "ERC20: transfer to the zero address");

        _balances[sender] = _balances[sender].sub(amount);
        _balances[recipient] = _balances[recipient].add(amount);
        emit Transfer(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
     *
     * - `to` cannot be the zero address.
     */
    function _mint(address account, uint256 amount) internal {
        require(account != address(0), "ERC20: mint to the zero address");

        _totalSupply = _totalSupply.add(amount);
        _balances[account] = _balances[account].add(amount);
        emit Transfer(address(0), account, amount);
    }

     /**
     * @dev Destoys `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 value) internal {
        require(account != address(0), "ERC20: burn from the zero address");

        _totalSupply = _totalSupply.sub(value);
        _balances[account] = _balances[account].sub(value);
        emit Transfer(account, address(0), value);
    }

    /**
     * @dev Sets `amount` as the allowance of `spender` over the `owner`s tokens.
     *
     * This is 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 value) internal {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");

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

    /**
     * @dev Destoys `amount` tokens from `account`.`amount` is then deducted
     * from the caller's allowance.
     *
     * See `_burn` and `_approve`.
     */
    function _burnFrom(address account, uint256 amount) internal {
        _burn(account, amount);
        _approve(account, msg.sender, _allowances[account][msg.sender].sub(amount));
    }
}

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a, "SafeMath: subtraction overflow");
        uint256 c = a - b;

        return c;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0, "SafeMath: division by zero");
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b != 0, "SafeMath: modulo by zero");
        return a % b;
    }
}

interface IBorrower {
    function executeOnFlashMint(uint256 amount) external;
}

/// @title FlashToken
/// @author Stephane Gosselin (@thegostep), Austin Williams (@Austin-Williams)
/// @notice Anyone can be rich... for an instant.
contract FlashToken is ERC20 {
    using SafeMath for uint256;

    ERC20 internal _baseToken;
    address private _factory;

    /////////////////////////////
    // Template Initialization //
    /////////////////////////////

    /// @notice Modifier which only allows to be `DELEGATECALL`ed from within a constructor on initialization of the contract.
    modifier initializeTemplate() {
        // set factory
        _factory = msg.sender;

        // only allow function to be `DELEGATECALL`ed from within a constructor.
        uint32 codeSize;
        assembly {
            codeSize := extcodesize(address)
        }
        require(codeSize == 0, "must be called within contract constructor");
        _;
    }

    /// @notice Initialize the instance with the base token
    function initialize(address baseToken) public initializeTemplate() {
        _baseToken = ERC20(baseToken);
    }

    /// @notice Get the address of the factory for this clone.
    /// @return factory address of the factory.
    function getFactory() public view returns (address factory) {
        return _factory;
    }

    /// @notice Get the address of the base token for this clone.
    /// @return factory address of the base token.
    function getBaseToken() public view returns (address baseToken) {
        return address(_baseToken);
    }

    //////////////
    // flashing //
    //////////////

    /// @notice Modifier which allows anyone to mint flash tokens.
    /// @notice An arbitrary number of flash tokens are minted for a single transaction.
    /// @notice Reverts if insuficient tokens are returned.
    modifier flashMint(uint256 amount) {
        // mint tokens and give to borrower
        _mint(msg.sender, amount); // reverts if `amount` makes `_totalSupply` overflow

        // execute flash fuckening
        _;

        // burn tokens
        _burn(msg.sender, amount); // reverts if `msg.sender` does not have enough units of the FMT

        // sanity check (not strictly needed)
        require(
            _baseToken.balanceOf(address(this)) >= totalSupply(),
            "redeemability was broken"
        );
    }

    /// @notice Deposit baseToken
    function deposit(uint256 amount) public {
        require(
            _baseToken.transferFrom(msg.sender, address(this), amount),
            "transfer in failed"
        );
        _mint(msg.sender, amount);
    }

    /// @notice Withdraw baseToken
    function withdraw(uint256 amount) public {
        _burn(msg.sender, amount); // reverts if `msg.sender` does not have enough CT-baseToken
        require(_baseToken.transfer(msg.sender, amount), "transfer out failed");
    }

    /// @notice Executes flash mint and calls strandard interface for transaction execution
    function softFlashFuck(uint256 amount) public flashMint(amount) {
        // hand control to borrower
        IBorrower(msg.sender).executeOnFlashMint(amount);
    }

    /// @notice Executes flash mint and calls arbitrary interface for transaction execution
    function hardFlashFuck(
        address target,
        bytes memory targetCalldata,
        uint256 amount
    ) public flashMint(amount) {
        (bool success, ) = target.call(targetCalldata);
        require(success, "external call failed");
    }
}

/// @title Spawn
/// @author 0age (@0age) for Numerai Inc
/// @dev Security contact: security@numer.ai
/// @dev Version: 1.2.0
/// @notice This contract provides creation code that is used by Spawner in order
/// to initialize and deploy eip-1167 minimal proxies for a given logic contract.
contract Spawn {
  constructor(
    address logicContract,
    bytes memory initializationCalldata
  ) public payable {
    // delegatecall into the logic contract to perform initialization.
    (bool ok, ) = logicContract.delegatecall(initializationCalldata);
    if (!ok) {
      // pass along failure message from delegatecall and revert.
      assembly {
        returndatacopy(0, 0, returndatasize)
        revert(0, returndatasize)
      }
    }

    // place eip-1167 runtime code in memory.
    bytes memory runtimeCode = abi.encodePacked(
      bytes10(0x363d3d373d3d3d363d73),
      logicContract,
      bytes15(0x5af43d82803e903d91602b57fd5bf3)
    );

    // return eip-1167 code to write it to spawned contract runtime.
    assembly {
      return(add(0x20, runtimeCode), 45) // eip-1167 runtime code, length
    }
  }
}

/// @title Spawner
/// @author 0age (@0age) and Stephane Gosselin (@thegostep) for Numerai Inc
/// @dev Security contact: security@numer.ai
/// @dev Version: 1.2.0
/// @notice This contract spawns and initializes eip-1167 minimal proxies that
/// point to existing logic contracts. The logic contracts need to have an
/// initializer function that should only callable when no contract exists at
/// their current address (i.e. it is being `DELEGATECALL`ed from a constructor).
contract Spawner {
  
  /// @notice Internal function for spawning an eip-1167 minimal proxy using `CREATE2`.
  /// @param creator address The address of the account creating the proxy.
  /// @param logicContract address The address of the logic contract.
  /// @param initializationCalldata bytes The calldata that will be supplied to
  /// the `DELEGATECALL` from the spawned contract to the logic contract during
  /// contract creation.
  /// @return The address of the newly-spawned contract.
  function _spawn(
    address creator,
    address logicContract,
    bytes memory initializationCalldata
  ) internal returns (address spawnedContract) {

    // get instance code and hash

    bytes memory initCode;
    bytes32 initCodeHash;
    (initCode, initCodeHash) = _getInitCodeAndHash(logicContract, initializationCalldata);

    // get valid create2 target

    (address target, bytes32 safeSalt) = _getNextNonceTargetWithInitCodeHash(creator, initCodeHash);

    // spawn create2 instance and validate

    return _executeSpawnCreate2(initCode, safeSalt, target);
  }

  /// @notice Internal function for spawning an eip-1167 minimal proxy using `CREATE2`.
  /// @param creator address The address of the account creating the proxy.
  /// @param logicContract address The address of the logic contract.
  /// @param initializationCalldata bytes The calldata that will be supplied to
  /// the `DELEGATECALL` from the spawned contract to the logic contract during
  /// contract creation.
  /// @param salt bytes32 A user defined salt.
  /// @return The address of the newly-spawned contract.
  function _spawnSalty(
    address creator,
    address logicContract,
    bytes memory initializationCalldata,
    bytes32 salt
  ) internal returns (address spawnedContract) {

    // get instance code and hash

    bytes memory initCode;
    bytes32 initCodeHash;
    (initCode, initCodeHash) = _getInitCodeAndHash(logicContract, initializationCalldata);

    // get valid create2 target

    (address target, bytes32 safeSalt, bool validity) = _getSaltyTargetWithInitCodeHash(creator, initCodeHash, salt);
    require(validity, "contract already deployed with supplied salt");

    // spawn create2 instance and validate

    return _executeSpawnCreate2(initCode, safeSalt, target);
  }

  /// @notice Private function for spawning an eip-1167 minimal proxy using `CREATE2`.
  /// Reverts with appropriate error string if deployment is unsuccessful.
  /// @param initCode bytes The spawner code and initialization calldata.
  /// @param safeSalt bytes32 A valid salt hashed with creator address.
  /// @param target address The expected address of the proxy.
  /// @return The address of the newly-spawned contract.
  function _executeSpawnCreate2(bytes memory initCode, bytes32 safeSalt, address target) private returns (address spawnedContract) {
    assembly {
      let encoded_data := add(0x20, initCode) // load initialization code.
      let encoded_size := mload(initCode)     // load the init code's length.
      spawnedContract := create2(             // call `CREATE2` w/ 4 arguments.
        callvalue,                            // forward any supplied endowment.
        encoded_data,                         // pass in initialization code.
        encoded_size,                         // pass in init code's length.
        safeSalt                              // pass in the salt value.
      )

      // pass along failure message from failed contract deployment and revert.
      if iszero(spawnedContract) {
        returndatacopy(0, 0, returndatasize)
        revert(0, returndatasize)
      }
    }

    // validate spawned instance matches target
    require(spawnedContract == target, "attempted deployment to unexpected address");

    // explicit return
    return spawnedContract;
  }

  /// @notice Internal view function for finding the expected address of the standard
  /// eip-1167 minimal proxy created using `CREATE2` with a given logic contract,
  /// salt, and initialization calldata payload.
  /// @param creator address The address of the account creating the proxy.
  /// @param logicContract address The address of the logic contract.
  /// @param initializationCalldata bytes The calldata that will be supplied to
  /// the `DELEGATECALL` from the spawned contract to the logic contract during
  /// contract creation.
  /// @param salt bytes32 A user defined salt.
  /// @return target address The address of the newly-spawned contract.
  /// @return validity bool True if the `target` is available.
  function _getSaltyTarget(
    address creator,
    address logicContract,
    bytes memory initializationCalldata,
    bytes32 salt
  ) internal view returns (address target, bool validity) {

    // get initialization code

    bytes32 initCodeHash;
    ( , initCodeHash) = _getInitCodeAndHash(logicContract, initializationCalldata);

    // get valid target

    (target, , validity) = _getSaltyTargetWithInitCodeHash(creator, initCodeHash, salt);

    // explicit return
    return (target, validity);
  }

  /// @notice Internal view function for finding the expected address of the standard
  /// eip-1167 minimal proxy created using `CREATE2` with a given initCodeHash, and salt.
  /// @param creator address The address of the account creating the proxy.
  /// @param initCodeHash bytes32 The hash of initCode.
  /// @param salt bytes32 A user defined salt.
  /// @return target address The address of the newly-spawned contract.
  /// @return safeSalt bytes32 A safe salt. Must include the msg.sender address for front-running protection.
  /// @return validity bool True if the `target` is available.
  function _getSaltyTargetWithInitCodeHash(
    address creator,
    bytes32 initCodeHash,
    bytes32 salt
  ) private view returns (address target, bytes32 safeSalt, bool validity) {
    // get safeSalt from input
    safeSalt = keccak256(abi.encodePacked(creator, salt));

    // get expected target
    target = _computeTargetWithCodeHash(initCodeHash, safeSalt);

    // get target validity
    validity = _getTargetValidity(target);

    // explicit return
    return (target, safeSalt, validity);
  }

  /// @notice Internal view function for finding the expected address of the standard
  /// eip-1167 minimal proxy created using `CREATE2` with a given logic contract,
  /// nonce, and initialization calldata payload.
  /// @param creator address The address of the account creating the proxy.
  /// @param logicContract address The address of the logic contract.
  /// @param initializationCalldata bytes The calldata that will be supplied to
  /// the `DELEGATECALL` from the spawned contract to the logic contract during
  /// contract creation.
  /// @return target address The address of the newly-spawned contract.
  function _getNextNonceTarget(
    address creator,
    address logicContract,
    bytes memory initializationCalldata
  ) internal view returns (address target) {

    // get initialization code

    bytes32 initCodeHash;
    ( , initCodeHash) = _getInitCodeAndHash(logicContract, initializationCalldata);

    // get valid target

    (target, ) = _getNextNonceTargetWithInitCodeHash(creator, initCodeHash);

    // explicit return
    return target;
  }

  /// @notice Internal view function for finding the expected address of the standard
  /// eip-1167 minimal proxy created using `CREATE2` with a given initCodeHash, and nonce.
  /// @param creator address The address of the account creating the proxy.
  /// @param initCodeHash bytes32 The hash of initCode.
  /// @return target address The address of the newly-spawned contract.
  /// @return safeSalt bytes32 A safe salt. Must include the msg.sender address for front-running protection.
  function _getNextNonceTargetWithInitCodeHash(
    address creator,
    bytes32 initCodeHash
  ) private view returns (address target, bytes32 safeSalt) {
    // set the initial nonce to be provided when constructing the salt.
    uint256 nonce = 0;

    while (true) {
      // get safeSalt from nonce
      safeSalt = keccak256(abi.encodePacked(creator, nonce));

      // get expected target
      target = _computeTargetWithCodeHash(initCodeHash, safeSalt);

      // validate no contract already deployed to the target address.
      // exit the loop if no contract is deployed to the target address.
      // otherwise, increment the nonce and derive a new salt.
      if (_getTargetValidity(target))
        break;
      else
        nonce++;
    }
    
    // explicit return
    return (target, safeSalt);
  }

  /// @notice Private pure function for obtaining the initCode and the initCodeHash of `logicContract` and `initializationCalldata`.
  /// @param logicContract address The address of the logic contract.
  /// @param initializationCalldata bytes The calldata that will be supplied to
  /// the `DELEGATECALL` from the spawned contract to the logic contract during
  /// contract creation.
  /// @return initCode bytes The spawner code and initialization calldata.
  /// @return initCodeHash bytes32 The hash of initCode.
  function _getInitCodeAndHash(
    address logicContract,
    bytes memory initializationCalldata
  ) private pure returns (bytes memory initCode, bytes32 initCodeHash) {
    // place creation code and constructor args of contract to spawn in memory.
    initCode = abi.encodePacked(
      type(Spawn).creationCode,
      abi.encode(logicContract, initializationCalldata)
    );

    // get the keccak256 hash of the init code for address derivation.
    initCodeHash = keccak256(initCode);

    // explicit return
    return (initCode, initCodeHash);
  }
  
  /// @notice Private view function for finding the expected address of the standard
  /// eip-1167 minimal proxy created using `CREATE2` with a given logic contract,
  /// salt, and initialization calldata payload.
  /// @param initCodeHash bytes32 The hash of initCode.
  /// @param safeSalt bytes32 A safe salt. Must include the msg.sender address for front-running protection.
  /// @return The address of the proxy contract with the given parameters.
  function _computeTargetWithCodeHash(
    bytes32 initCodeHash,
    bytes32 safeSalt
  ) private view returns (address target) {
    return address(    // derive the target deployment address.
      uint160(                   // downcast to match the address type.
        uint256(                 // cast to uint to truncate upper digits.
          keccak256(             // compute CREATE2 hash using 4 inputs.
            abi.encodePacked(    // pack all inputs to the hash together.
              bytes1(0xff),      // pass in the control character.
              address(this),     // pass in the address of this contract.
              safeSalt,          // pass in the safeSalt from above.
              initCodeHash       // pass in hash of contract creation code.
            )
          )
        )
      )
    );
  }

  /// @notice Private view function to validate if the `target` address is an available deployment address.
  /// @param target address The address to validate.
  /// @return validity bool True if the `target` is available.
  function _getTargetValidity(address target) private view returns (bool validity) {
    // validate no contract already deployed to the target address.
    uint256 codeSize;
    assembly { codeSize := extcodesize(target) }
    return codeSize == 0;
  }
}

/// @title FlashTokenFactory
/// @author Stephane Gosselin (@thegostep)
/// @notice An Erasure style factory for Wrapping FlashTokens
contract FlashTokenFactory is Spawner {
    uint256 private _tokenCount;
    address private _templateContract;
    mapping(address => address) private _baseToFlash;
    mapping(address => address) private _flashToBase;
    mapping(uint256 => address) private _idToBase;

    event TemplateSet(address indexed templateContract);
    event FlashTokenCreated(
        address indexed token,
        address indexed flashToken,
        uint256 tokenID
    );

    /// @notice Initialize factory with template contract.
    constructor(address templateContract) public {
        _templateContract = templateContract;
        emit TemplateSet(templateContract);
    }

    /// @notice Create a FlashToken wrap for any ERC20 token
    function createFlashToken(address token)
        public
        returns (address flashToken)
    {
        require(token != address(0), "cannot wrap address 0");
        if (_baseToFlash[token] != address(0)) {
            return _baseToFlash[token];
        } else {
            require(_baseToFlash[token] == address(0), "token already wrapped");

            flashToken = _flashWrap(token);

            _baseToFlash[token] = flashToken;
            _flashToBase[flashToken] = token;
            _tokenCount += 1;
            _idToBase[_tokenCount] = token;

            emit FlashTokenCreated(token, flashToken, _tokenCount);
            return flashToken;
        }
    }

    /// @notice Initialize instance
    function _flashWrap(address token) private returns (address flashToken) {
        FlashToken template;
        bytes memory initCalldata = abi.encodeWithSelector(
            template.initialize.selector,
            token
        );
        return Spawner._spawn(address(this), _templateContract, initCalldata);
    }

    // Getters

    /// @notice Get FlashToken contract associated with given ERC20 token
    function getFlashToken(address token)
        public
        view
        returns (address flashToken)
    {
        return _baseToFlash[token];
    }

    /// @notice Get ERC20 token contract associated with given FlashToken
    function getBaseToken(address flashToken)
        public
        view
        returns (address token)
    {
        return _flashToBase[flashToken];
    }

    /// @notice Get ERC20 token contract associated with given FlashToken ID
    function getBaseFromID(uint256 tokenID)
        public
        view
        returns (address token)
    {
        return _idToBase[tokenID];
    }

    /// @notice Get count of FlashToken contracts created from this factory
    function getTokenCount() public view returns (uint256 tokenCount) {
        return _tokenCount;
    }

}