// Vulnerability label: DC1
// SPDX-License-Identifier: MIT
pragma solidity >=0.7.2;
pragma experimental ABIEncoderV2;

enum PurchaseMethod {Invalid, Contract, ZeroEx}


/**
 * @title Types: Library of Swap Protocol Types and Hashes
 */
library Types {
    struct Order {
        uint256 nonce; // Unique per order and should be sequential
        uint256 expiry; // Expiry in seconds since 1 January 1970
        Party signer; // Party to the trade that sets terms
        Party sender; // Party to the trade that accepts terms
        Party affiliate; // Party compensated for facilitating (optional)
        Signature signature; // Signature of the order
    }

    struct Party {
        bytes4 kind; // Interface ID of the token
        address wallet; // Wallet address of the party
        address token; // Contract address of the token
        uint256 amount; // Amount for ERC-20 or ERC-1155
        uint256 id; // ID for ERC-721 or ERC-1155
    }

    struct Signature {
        address signatory; // Address of the wallet used to sign
        address validator; // Address of the intended swap contract
        bytes1 version; // EIP-191 signature version
        uint8 v; // `v` value of an ECDSA signature
        bytes32 r; // `r` value of an ECDSA signature
        bytes32 s; // `s` value of an ECDSA signature
    }
}



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);
}

// 
/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */

// 
/**
 * @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, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        uint256 c = a + b;
        if (c < a) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the substraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b > a) return (false, 0);
        return (true, a - b);
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) return (true, 0);
        uint256 c = a * b;
        if (c / a != b) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a / b);
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a % b);
    }

    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        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");
        return a - b;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        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, reverting 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) {
        require(b > 0, "SafeMath: division by zero");
        return a / b;
    }

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

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        return a - b;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryDiv}.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a % b;
    }
}

// 
/**
 * @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;
        // solhint-disable-next-line no-inline-assembly
        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");

        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (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");

        // solhint-disable-next-line avoid-low-level-calls
        (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");

        // solhint-disable-next-line avoid-low-level-calls
        (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");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    function _verifyCallResult(bool success, bytes memory returndata, string memory errorMessage) private 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

                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

library SafeERC20 {
    using SafeMath for uint256;
    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'
        // solhint-disable-next-line max-line-length
        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).add(value);
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).sub(value, "SafeERC20: decreased allowance below zero");
        _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
            // solhint-disable-next-line max-line-length
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}

// 
/*
 * @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 GSN 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 payable) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}

contract ERC20 is Context, IERC20 {
    using SafeMath for uint256;

    mapping (address => uint256) private _balances;

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

    uint256 private _totalSupply;

    string private _name;
    string private _symbol;
    uint8 private _decimals;

    /**
     * @dev Sets the values for {name} and {symbol}, initializes {decimals} with
     * a default value of 18.
     *
     * To select a different value for {decimals}, use {_setupDecimals}.
     *
     * All three of these values are immutable: they can only be set once during
     * construction.
     */
    constructor (string memory name_, string memory symbol_) public {
        _name = name_;
        _symbol = symbol_;
        _decimals = 18;
    }

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

    /**
     * @dev Returns the symbol of the token, usually a shorter version of the
     * name.
     */
    function symbol() public view virtual 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 {_setupDecimals} is
     * called.
     *
     * 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 returns (uint8) {
        return _decimals;
    }

    /**
     * @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);
        _approve(sender, _msgSender(), _allowances[sender][_msgSender()].sub(amount, "ERC20: transfer amount exceeds allowance"));
        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].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 virtual returns (bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender].sub(subtractedValue, "ERC20: decreased allowance below zero"));
        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 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);

        _balances[sender] = _balances[sender].sub(amount, "ERC20: transfer amount exceeds balance");
        _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 virtual {
        require(account != address(0), "ERC20: mint to the zero address");

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

        _totalSupply = _totalSupply.add(amount);
        _balances[account] = _balances[account].add(amount);
        emit Transfer(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);

        _balances[account] = _balances[account].sub(amount, "ERC20: burn amount exceeds balance");
        _totalSupply = _totalSupply.sub(amount);
        emit Transfer(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 Sets {decimals} to a value other than the default one of 18.
     *
     * WARNING: This function should only be called from the constructor. Most
     * applications that interact with token contracts will not expect
     * {decimals} to ever change, and may work incorrectly if it does.
     */
    function _setupDecimals(uint8 decimals_) internal virtual {
        _decimals = decimals_;
    }

    /**
     * @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 to 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 { }
}

contract DSMath {
    function add(uint x, uint y) internal pure returns (uint z) {
        require((z = x + y) >= x, "ds-math-add-overflow");
    }
    function sub(uint x, uint y) internal pure returns (uint z) {
        require((z = x - y) <= x, "ds-math-sub-underflow");
    }
    function mul(uint x, uint y) internal pure returns (uint z) {
        require(y == 0 || (z = x * y) / y == x, "ds-math-mul-overflow");
    }

    function min(uint x, uint y) internal pure returns (uint z) {
        return x <= y ? x : y;
    }
    function max(uint x, uint y) internal pure returns (uint z) {
        return x >= y ? x : y;
    }
    function imin(int x, int y) internal pure returns (int z) {
        return x <= y ? x : y;
    }
    function imax(int x, int y) internal pure returns (int z) {
        return x >= y ? x : y;
    }

    uint constant WAD = 10 ** 18;
    uint constant RAY = 10 ** 27;

    //rounds to zero if x*y < WAD / 2
    function wmul(uint x, uint y) internal pure returns (uint z) {
        z = add(mul(x, y), WAD / 2) / WAD;
    }
    //rounds to zero if x*y < WAD / 2
    function rmul(uint x, uint y) internal pure returns (uint z) {
        z = add(mul(x, y), RAY / 2) / RAY;
    }
    //rounds to zero if x*y < WAD / 2
    function wdiv(uint x, uint y) internal pure returns (uint z) {
        z = add(mul(x, WAD), y / 2) / y;
    }
    //rounds to zero if x*y < RAY / 2
    function rdiv(uint x, uint y) internal pure returns (uint z) {
        z = add(mul(x, RAY), y / 2) / y;
    }

    // This famous algorithm is called "exponentiation by squaring"
    // and calculates x^n with x as fixed-point and n as regular unsigned.
    //
    // It's O(log n), instead of O(n) for naive repeated multiplication.
    //
    // These facts are why it works:
    //
    //  If n is even, then x^n = (x^2)^(n/2).
    //  If n is odd,  then x^n = x * x^(n-1),
    //   and applying the equation for even x gives
    //    x^n = x * (x^2)^((n-1) / 2).
    //
    //  Also, EVM division is flooring and
    //    floor[(n-1) / 2] = floor[n / 2].
    //
    function rpow(uint x, uint n) internal pure returns (uint z) {
        z = n % 2 != 0 ? x : RAY;

        for (n /= 2; n != 0; n /= 2) {
            x = rmul(x, x);

            if (n % 2 != 0) {
                z = rmul(z, x);
            }
        }
    }
}

struct OptionTerms {
    address underlying;
    address strikeAsset;
    address collateralAsset;
    uint256 expiry;
    uint256 strikePrice;
    OptionType optionType;
    address paymentToken;
}

interface IProtocolAdapter {
    /**
     * @notice Emitted when a new option contract is purchased
     */
    event Purchased(
        address indexed caller,
        string indexed protocolName,
        address indexed underlying,
        address strikeAsset,
        uint256 expiry,
        uint256 strikePrice,
        OptionType optionType,
        uint256 amount,
        uint256 premium,
        uint256 optionID
    );

    /**
     * @notice Emitted when an option contract is exercised
     */
    event Exercised(
        address indexed caller,
        address indexed options,
        uint256 indexed optionID,
        uint256 amount,
        uint256 exerciseProfit
    );

    /**
     * @notice Name of the adapter. E.g. "HEGIC", "OPYN_V1". Used as index key for adapter addresses
     */
    function protocolName() external pure returns (string memory);

    /**
     * @notice Boolean flag to indicate whether to use option IDs or not.
     * Fungible protocols normally use tokens to represent option contracts.
     */
    function nonFungible() external pure returns (bool);

    /**
     * @notice Returns the purchase method used to purchase options
     */
    function purchaseMethod() external pure returns (PurchaseMethod);

    /**
     * @notice Check if an options contract exist based on the passed parameters.
     * @param optionTerms is the terms of the option contract
     */
    function optionsExist(OptionTerms calldata optionTerms)
        external
        view
        returns (bool);

    /**
     * @notice Get the options contract's address based on the passed parameters
     * @param optionTerms is the terms of the option contract
     */
    function getOptionsAddress(OptionTerms calldata optionTerms)
        external
        view
        returns (address);

    /**
     * @notice Gets the premium to buy `purchaseAmount` of the option contract in ETH terms.
     * @param optionTerms is the terms of the option contract
     * @param purchaseAmount is the number of options purchased
     */
    function premium(OptionTerms calldata optionTerms, uint256 purchaseAmount)
        external
        view
        returns (uint256 cost);

    /**
     * @notice Amount of profit made from exercising an option contract (current price - strike price). 0 if exercising out-the-money.
     * @param options is the address of the options contract
     * @param optionID is the ID of the option position in non fungible protocols like Hegic.
     * @param amount is the amount of tokens or options contract to exercise. Only relevant for fungle protocols like Opyn
     */
    function exerciseProfit(
        address options,
        uint256 optionID,
        uint256 amount
    ) external view returns (uint256 profit);

    function canExercise(
        address options,
        uint256 optionID,
        uint256 amount
    ) external view returns (bool);

    /**
     * @notice Purchases the options contract.
     * @param optionTerms is the terms of the option contract
     * @param amount is the purchase amount in Wad units (10**18)
     */
    function purchase(
        OptionTerms calldata optionTerms,
        uint256 amount,
        uint256 maxCost
    ) external payable returns (uint256 optionID);

    /**
     * @notice Exercises the options contract.
     * @param options is the address of the options contract
     * @param optionID is the ID of the option position in non fungible protocols like Hegic.
     * @param amount is the amount of tokens or options contract to exercise. Only relevant for fungle protocols like Opyn
     * @param recipient is the account that receives the exercised profits. This is needed since the adapter holds all the positions and the msg.sender is an instrument contract.
     */
    function exercise(
        address options,
        uint256 optionID,
        uint256 amount,
        address recipient
    ) external payable;

    function createShort(OptionTerms calldata optionTerms, uint256 amount)
        external
        returns (uint256);

    function closeShort() external returns (uint256);
}

enum OptionType {Invalid, Put, Call}

struct ZeroExOrder {
    address exchangeAddress;
    address buyTokenAddress;
    address sellTokenAddress;
    address allowanceTarget;
    uint256 protocolFee;
    uint256 makerAssetAmount;
    uint256 takerAssetAmount;
    bytes swapData;
}

library ProtocolAdapter {
    function delegateOptionsExist(
        IProtocolAdapter adapter,
        OptionTerms calldata optionTerms
    ) external view returns (bool) {
        (bool success, bytes memory result) =
            address(adapter).staticcall(
                abi.encodeWithSignature(
                    "optionsExist((address,address,address,uint256,uint256,uint8,address))",
                    optionTerms
                )
            );
        require(success, getRevertMsg(result));
        return abi.decode(result, (bool));
    }

    function delegateGetOptionsAddress(
        IProtocolAdapter adapter,
        OptionTerms calldata optionTerms
    ) external view returns (address) {
        (bool success, bytes memory result) =
            address(adapter).staticcall(
                abi.encodeWithSignature(
                    "getOptionsAddress((address,address,address,uint256,uint256,uint8,address))",
                    optionTerms
                )
            );
        require(success, getRevertMsg(result));
        return abi.decode(result, (address));
    }

    function delegatePremium(
        IProtocolAdapter adapter,
        OptionTerms calldata optionTerms,
        uint256 purchaseAmount
    ) external view returns (uint256) {
        (bool success, bytes memory result) =
            address(adapter).staticcall(
                abi.encodeWithSignature(
                    "premium((address,address,address,uint256,uint256,uint8,address),uint256)",
                    optionTerms,
                    purchaseAmount
                )
            );
        require(success, "premium staticcall failed");
        return abi.decode(result, (uint256));
    }

    function delegateExerciseProfit(
        IProtocolAdapter adapter,
        address options,
        uint256 optionID,
        uint256 amount
    ) external view returns (uint256) {
        (bool success, bytes memory result) =
            address(adapter).staticcall(
                abi.encodeWithSignature(
                    "exerciseProfit(address,uint256,uint256)",
                    options,
                    optionID,
                    amount
                )
            );
        require(success, getRevertMsg(result));
        return abi.decode(result, (uint256));
    }

    function delegatePurchase(
        IProtocolAdapter adapter,
        OptionTerms calldata optionTerms,
        uint256 purchaseAmount,
        uint256 maxCost
    ) external returns (uint256) {
        (bool success, bytes memory result) =
            address(adapter).delegatecall(
                abi.encodeWithSignature(
                    "purchase((address,address,address,uint256,uint256,uint8,address),uint256,uint256)",
                    optionTerms,
                    purchaseAmount,
                    maxCost
                )
            );
        require(success, getRevertMsg(result));
        return abi.decode(result, (uint256));
    }

    function delegatePurchaseWithZeroEx(
        IProtocolAdapter adapter,
        OptionTerms calldata optionTerms,
        ZeroExOrder calldata zeroExOrder
    ) external {
        (bool success, bytes memory result) =
            address(adapter).delegatecall(
                abi.encodeWithSignature(
                    "purchaseWithZeroEx((address,address,address,uint256,uint256,uint8,address),(address,address,address,address,uint256,uint256,uint256,bytes))",
                    optionTerms,
                    zeroExOrder
                )
            );
        require(success, getRevertMsg(result));
    }

    function delegateExercise(
        IProtocolAdapter adapter,
        address options,
        uint256 optionID,
        uint256 amount,
        address recipient
    ) external {
        (bool success, bytes memory res) =
            address(adapter).delegatecall(
                abi.encodeWithSignature(
                    "exercise(address,uint256,uint256,address)",
                    options,
                    optionID,
                    amount,
                    recipient
                )
            );
        require(success, getRevertMsg(res));
    }

    function delegateClaimRewards(
        IProtocolAdapter adapter,
        address rewardsAddress,
        uint256[] calldata optionIDs
    ) external returns (uint256) {
        (bool success, bytes memory result) =
            address(adapter).delegatecall(
                abi.encodeWithSignature(
                    "claimRewards(address,uint256[])",
                    rewardsAddress,
                    optionIDs
                )
            );
        require(success, getRevertMsg(result));
        return abi.decode(result, (uint256));
    }

    function delegateRewardsClaimable(
        IProtocolAdapter adapter,
        address rewardsAddress,
        uint256[] calldata optionIDs
    ) external view returns (uint256) {
        (bool success, bytes memory result) =
            address(adapter).staticcall(
                abi.encodeWithSignature(
                    "rewardsClaimable(address,uint256[])",
                    rewardsAddress,
                    optionIDs
                )
            );
        require(success, getRevertMsg(result));
        return abi.decode(result, (uint256));
    }

    function delegateCreateShort(
        IProtocolAdapter adapter,
        OptionTerms calldata optionTerms,
        uint256 amount
    ) external returns (uint256) {
        (bool success, bytes memory res) =
            address(adapter).delegatecall(
                abi.encodeWithSignature(
                    "createShort((address,address,address,uint256,uint256,uint8,address),uint256)",
                    optionTerms,
                    amount
                )
            );
        require(success, getRevertMsg(res));
        return abi.decode(res, (uint256));
    }

    function delegateCloseShort(IProtocolAdapter adapter)
        external
        returns (uint256)
    {
        (bool success, bytes memory res) =
            address(adapter).delegatecall(
                abi.encodeWithSignature("closeShort()")
            );
        require(success, getRevertMsg(res));
        return abi.decode(res, (uint256));
    }

    function getRevertMsg(bytes memory _returnData)
        internal
        pure
        returns (string memory)
    {
        // If the _res length is less than 68, then the transaction failed silently (without a revert message)
        if (_returnData.length < 68) return "Transaction reverted silently";

        assembly {
            // Slice the sighash.
            _returnData := add(_returnData, 0x04)
        }
        return abi.decode(_returnData, (string)); // All that remains is the revert string
    }
}

interface IRibbonFactory {
    function isInstrument(address instrument) external returns (bool);

    function getAdapter(string calldata protocolName)
        external
        view
        returns (address);

    function getAdapters()
        external
        view
        returns (address[] memory adaptersArray);

    function burnGasTokens() external;
}

interface IWETH {
    function deposit() external payable;

    function withdraw(uint256) external;

    function balanceOf(address account) external view returns (uint256);

    function transfer(address recipient, uint256 amount)
        external
        returns (bool);

    function allowance(address owner, address spender)
        external
        view
        returns (uint256);

    function approve(address spender, uint256 amount) external returns (bool);

    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) external returns (bool);
}

interface ISwap {
    event Swap(
        uint256 indexed nonce,
        uint256 timestamp,
        address indexed signerWallet,
        uint256 signerAmount,
        uint256 signerId,
        address signerToken,
        address indexed senderWallet,
        uint256 senderAmount,
        uint256 senderId,
        address senderToken,
        address affiliateWallet,
        uint256 affiliateAmount,
        uint256 affiliateId,
        address affiliateToken
    );

    event Cancel(uint256 indexed nonce, address indexed signerWallet);

    event CancelUpTo(uint256 indexed nonce, address indexed signerWallet);

    event AuthorizeSender(
        address indexed authorizerAddress,
        address indexed authorizedSender
    );

    event AuthorizeSigner(
        address indexed authorizerAddress,
        address indexed authorizedSigner
    );

    event RevokeSender(
        address indexed authorizerAddress,
        address indexed revokedSender
    );

    event RevokeSigner(
        address indexed authorizerAddress,
        address indexed revokedSigner
    );

    /**
     * @notice Atomic Token Swap
     * @param order Types.Order
     */
    function swap(Types.Order calldata order) external;

    /**
     * @notice Cancel one or more open orders by nonce
     * @param nonces uint256[]
     */
    function cancel(uint256[] calldata nonces) external;

    /**
     * @notice Cancels all orders below a nonce value
     * @dev These orders can be made active by reducing the minimum nonce
     * @param minimumNonce uint256
     */
    function cancelUpTo(uint256 minimumNonce) external;

    /**
     * @notice Authorize a delegated sender
     * @param authorizedSender address
     */
    function authorizeSender(address authorizedSender) external;

    /**
     * @notice Authorize a delegated signer
     * @param authorizedSigner address
     */
    function authorizeSigner(address authorizedSigner) external;

    /**
     * @notice Revoke an authorization
     * @param authorizedSender address
     */
    function revokeSender(address authorizedSender) external;

    /**
     * @notice Revoke an authorization
     * @param authorizedSigner address
     */
    function revokeSigner(address authorizedSigner) external;

    function senderAuthorizations(address, address)
        external
        view
        returns (bool);

    function signerAuthorizations(address, address)
        external
        view
        returns (bool);

    function signerNonceStatus(address, uint256) external view returns (bytes1);

    function signerMinimumNonce(address) external view returns (uint256);

    function registry() external view returns (address);
}

interface OtokenInterface {
    function addressBook() external view returns (address);

    function underlyingAsset() external view returns (address);

    function strikeAsset() external view returns (address);

    function collateralAsset() external view returns (address);

    function strikePrice() external view returns (uint256);

    function expiryTimestamp() external view returns (uint256);

    function isPut() external view returns (bool);

    function init(
        address _addressBook,
        address _underlyingAsset,
        address _strikeAsset,
        address _collateralAsset,
        uint256 _strikePrice,
        uint256 _expiry,
        bool _isPut
    ) external;

    function mintOtoken(address account, uint256 amount) external;

    function burnOtoken(address account, uint256 amount) external;
}

abstract contract Ownable {
    address private _owner;

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

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    function initialize(address newOwner) public {
        _owner = newOwner;
        emit OwnershipTransferred(address(0), newOwner);
    }

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

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(_owner == msg.sender, "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 {
        emit OwnershipTransferred(_owner, address(0));
        _owner = 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"
        );
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}

abstract contract ReentrancyGuard {
    // Booleans are more expensive than uint256 or any type that takes up a full
    // word because each write operation emits an extra SLOAD to first read the
    // slot's contents, replace the bits taken up by the boolean, and then write
    // back. This is the compiler's defense against contract upgrades and
    // pointer aliasing, and it cannot be disabled.

    // The values being non-zero value makes deployment a bit more expensive,
    // but in exchange the refund on every call to nonReentrant will be lower in
    // amount. Since refunds are capped to a percentage of the total
    // transaction's gas, it is best to keep them low in cases like this one, to
    // increase the likelihood of the full refund coming into effect.
    uint256 private constant _NOT_ENTERED = 1;
    uint256 private constant _ENTERED = 2;

    uint256 private _status;

    constructor () internal {
        _status = _NOT_ENTERED;
    }

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * Calling a `nonReentrant` function from another `nonReentrant`
     * function is not supported. It is possible to prevent this from happening
     * by making the `nonReentrant` function external, and make it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        // On the first call to nonReentrant, _notEntered will be true
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

        // Any calls to nonReentrant after this point will fail
        _status = _ENTERED;

        _;

        // By storing the original value once again, a refund is triggered (see
        // https://eips.ethereum.org/EIPS/eip-2200)
        _status = _NOT_ENTERED;
    }
}

contract Initializable {
    /**
     * @dev Indicates that the contract has been initialized.
     */
    bool private initialized;

    /**
     * @dev Indicates that the contract is in the process of being initialized.
     */
    bool private initializing;

    /**
     * @dev Modifier to use in the initializer function of a contract.
     */
    modifier initializer() {
        require(
            initializing || isConstructor() || !initialized,
            "Contract instance has already been initialized"
        );

        bool isTopLevelCall = !initializing;
        if (isTopLevelCall) {
            initializing = true;
            initialized = true;
        }

        _;

        if (isTopLevelCall) {
            initializing = false;
        }
    }

    /// @dev Returns true if and only if the function is running in the constructor
    function isConstructor() private view returns (bool) {
        // extcodesize checks the size of the code stored in an address, and
        // address returns the current address. Since the code is still not
        // deployed when running a constructor, any checks on its code size will
        // yield zero, making it an effective way to detect if a contract is
        // under construction or not.
        address self = address(this);
        uint256 cs;
        assembly {
            cs := extcodesize(self)
        }
        return cs == 0;
    }

    // Reserved storage space to allow for layout changes in the future.
    uint256[50] private ______gap;
}

contract OptionsVaultStorageV1 is Initializable, Ownable, ReentrancyGuard {
    // Ribbon Factory used to access adapters
    IRibbonFactory public factory;

    // Privileged role that is able to select the option terms (strike price, expiry) to short
    address public manager;

    // Option that the vault is currently shorting
    address public currentOption;

    // Amount that is currently locked for selling options
    uint256 public lockedAmount;
}

// 
contract RibbonETHCoveredCall is DSMath, ERC20, OptionsVaultStorageV1 {
    using ProtocolAdapter for IProtocolAdapter;
    using SafeERC20 for IERC20;
    using SafeMath for uint256;

    enum ExchangeMechanism {Unknown, AirSwap}
    string private constant _tokenName = "Ribbon ETH Covered Call Vault";
    string private constant _tokenSymbol = "rETH-COVCALL";
    string private constant _adapterName = "OPYN_GAMMA";
    address private constant _WETH = 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2;

    // AirSwap Swap contract https://github.com/airswap/airswap-protocols/blob/master/source/swap/contracts/interfaces/ISwap.sol
    ISwap private constant _swapContract =
        ISwap(0x4572f2554421Bd64Bef1c22c8a81840E8D496BeA);

    address public constant asset = _WETH;
    ExchangeMechanism public constant exchangeMechanism =
        ExchangeMechanism.AirSwap;

    // 1% for an instant withdrawal
    uint256 public constant instantWithdrawalFee = 0.01 ether;

    // 90% locked in options protocol, 10% of the pool reserved for withdrawals
    uint256 public constant lockedRatio = 0.9 ether;

    event ManagerChanged(address oldManager, address newManager);

    event Deposit(address indexed account, uint256 amount, uint256 share);

    event Withdraw(address indexed account, uint256 amount, uint256 share);

    event OpenShort(
        address indexed options,
        uint256 depositAmount,
        address manager
    );

    event CloseShort(
        address indexed options,
        uint256 withdrawAmount,
        address manager
    );

    constructor() ERC20(_tokenName, _tokenSymbol) {}

    /**
     * @notice Initializes the OptionVault contract with an owner and a factory.
     * @param _owner is the owner of the contract who can set the manager
     * @param _factory is the RibbonFactory instance
     */
    function initialize(address _owner, address _factory) public initializer {
        Ownable.initialize(_owner);
        factory = IRibbonFactory(_factory);
    }

    /**
     * @notice Sets the new manager of the vault. Revoke the airswap signer authorization from the old manager, and authorize the manager.
     * @param _manager is the new manager of the vault
     */
    function setManager(address _manager) public onlyOwner {
        require(_manager != address(0), "New manager cannot be 0x0");
        address oldManager = manager;
        if (oldManager != address(0)) {
            _swapContract.revokeSigner(oldManager);
        }
        manager = _manager;
        _swapContract.authorizeSigner(_manager);

        emit ManagerChanged(oldManager, _manager);
    }

    /**
     * @notice Deposits ETH into the contract and mint vault shares.
     */
    function depositETH() external payable nonReentrant {
        require(msg.value > 0, "No value passed");
        require(asset == _WETH, "Asset is not WETH");

        IWETH(_WETH).deposit{value: msg.value}();
        _deposit(msg.value);
    }

    /**
     * @notice Deposits the `asset` into the contract and mint vault shares.
     * @param amount is the amount of `asset` to deposit
     */
    function deposit(uint256 amount) external nonReentrant {
        IERC20(asset).safeTransferFrom(msg.sender, address(this), amount);
        _deposit(amount);
    }

    /**
     * @notice Mints the vault shares to the msg.sender
     * @param amount is the amount of `asset` deposited
     */
    function _deposit(uint256 amount) private {
        // amount needs to be subtracted from totalBalance because it has already been
        // added to it from either IWETH.deposit and IERC20.safeTransferFrom
        uint256 total = totalBalance().sub(amount);

        // Following the pool share calculation from Alpha Homora: https://github.com/AlphaFinanceLab/alphahomora/blob/340653c8ac1e9b4f23d5b81e61307bf7d02a26e8/contracts/5/Bank.sol#L104
        uint256 share =
            total == 0 ? amount : amount.mul(totalSupply()).div(total);
        _mint(msg.sender, share);
        emit Deposit(msg.sender, amount, share);
    }

    /**
     * @notice Withdraws ETH from vault using vault shares
     * @param share is the number of vault shares to be burned
     */
    function withdrawETH(uint256 share) external nonReentrant {
        uint256 withdrawAmount = _withdraw(share);

        IWETH(_WETH).withdraw(withdrawAmount);
        (bool success, ) = msg.sender.call{value: withdrawAmount}("");
        require(success, "ETH transfer failed");
    }

    /**
     * @notice Withdraws WETH from vault using vault shares
     * @param share is the number of vault shares to be burned
     */
    function withdraw(uint256 share) external nonReentrant {
        uint256 withdrawAmount = _withdraw(share);
        require(
            IERC20(asset).transfer(msg.sender, withdrawAmount),
            "ERC20 transfer failed"
        );
    }

    /**
     * @notice Burns vault shares and checks if eligible for withdrawal
     * @param share is the number of vault shares to be burned
     */
    function _withdraw(uint256 share) private returns (uint256) {
        uint256 _lockedAmount = lockedAmount;
        uint256 currentAssetBalance = IERC20(asset).balanceOf(address(this));
        uint256 total = _lockedAmount.add(currentAssetBalance);
        uint256 availableForWithdrawal =
            _availableToWithdraw(_lockedAmount, currentAssetBalance);

        // Following the pool share calculation from Alpha Homora: https://github.com/AlphaFinanceLab/alphahomora/blob/340653c8ac1e9b4f23d5b81e61307bf7d02a26e8/contracts/5/Bank.sol#L111
        uint256 withdrawAmount = share.mul(total).div(totalSupply());
        require(
            withdrawAmount <= availableForWithdrawal,
            "Cannot withdraw more than available"
        );

        uint256 feeAmount = wmul(withdrawAmount, instantWithdrawalFee);
        uint256 amountAfterFee = withdrawAmount.sub(feeAmount);

        _burn(msg.sender, share);

        emit Withdraw(msg.sender, amountAfterFee, share);

        return amountAfterFee;
    }

    /**
     * @notice Rolls from one short option position to another. Closes the expired short position, withdraw from it, then open a new position.
     * @param optionTerms are the option contract terms the vault will be short
     */
    function rollToNextOption(OptionTerms calldata optionTerms)
        external
        onlyManager
        nonReentrant
    {
        // We can save gas by storing the factory address as a constant
        IProtocolAdapter adapter =
            IProtocolAdapter(factory.getAdapter(_adapterName));

        address oldOption = currentOption;
        if (oldOption != address(0)) {
            require(
                block.timestamp >= OtokenInterface(oldOption).expiryTimestamp(),
                "Otoken not expired"
            );
            uint256 withdrawAmount = adapter.delegateCloseShort();
            emit CloseShort(oldOption, withdrawAmount, msg.sender);
        }

        uint256 currentBalance = IERC20(asset).balanceOf(address(this));
        uint256 shortAmount = wmul(currentBalance, lockedRatio);
        uint256 shortBalance =
            adapter.delegateCreateShort(optionTerms, shortAmount);

        address newOption = adapter.getOptionsAddress(optionTerms);
        IERC20 optionToken = IERC20(newOption);
        optionToken.approve(address(_swapContract), shortBalance);

        currentOption = newOption;
        lockedAmount = shortAmount;

        emit OpenShort(newOption, shortAmount, msg.sender);
    }

    /**
     * @notice Returns the expiry of the current option the vault is shorting
     */
    function currentOptionExpiry() external view returns (uint256) {
        address _currentOption = currentOption;
        if (_currentOption == address(0)) {
            return 0;
        }

        OtokenInterface oToken = OtokenInterface(currentOption);
        return oToken.expiryTimestamp();
    }

    /**
     * @notice Returns the vault's total balance, including the amounts locked into a short position
     */
    function totalBalance() public view returns (uint256) {
        return lockedAmount.add(IERC20(asset).balanceOf(address(this)));
    }

    /**
     * @notice Returns the amount available for users to withdraw. MIN(10% * (locked + assetBalance), assetBalance)
     */
    function availableToWithdraw() external view returns (uint256) {
        return
            _availableToWithdraw(
                lockedAmount,
                IERC20(asset).balanceOf(address(this))
            );
    }

    /**
     * @notice Helper function that returns amount available to withdraw. Used to save gas.
     */
    function _availableToWithdraw(uint256 lockedBalance, uint256 freeBalance)
        private
        pure
        returns (uint256)
    {
        uint256 total = lockedBalance.add(freeBalance);
        uint256 reserveRatio = uint256(1 ether).sub(lockedRatio);
        uint256 reserve = wmul(total, reserveRatio);

        return min(reserve, freeBalance);
    }

    /**
     * @notice Returns the token name
     */
    function name() public pure override returns (string memory) {
        return _tokenName;
    }

    /**
     * @notice Returns the token symbol
     */
    function symbol() public pure override returns (string memory) {
        return _tokenSymbol;
    }

    /**
     * @notice Only allows manager to execute a function
     */
    modifier onlyManager {
        require(msg.sender == manager, "Only manager");
        _;
    }
}