pragma solidity ^0.5.0;
pragma experimental ABIEncoderV2;


/**
 * @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) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     * - Subtraction cannot overflow.
     *
     * _Available since v2.4.0._
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        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) {
        return div(a, b, "SafeMath: division by zero");
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     *
     * _Available since v2.4.0._
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0, errorMessage);
        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) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts with custom message 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.
     *
     * _Available since v2.4.0._
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}

/**
 * @dev Interface of the ERC165 standard, as defined in the
 * https://eips.ethereum.org/EIPS/eip-165[EIP].
 *
 * Implementers can declare support of contract interfaces, which can then be
 * queried by others ({ERC165Checker}).
 *
 * For an implementation, see {ERC165}.
 */
interface IERC165 {
    /**
     * @dev Returns true if this contract implements the interface defined by
     * `interfaceId`. See the corresponding
     * https://eips.ethereum.org/EIPS/eip-165#how-interfaces-are-identified[EIP section]
     * to learn more about how these ids are created.
     *
     * This function call must use less than 30 000 gas.
     */
    function supportsInterface(bytes4 interfaceId) external view returns (bool);
}

/**
 * @dev Required interface of an ERC721 compliant contract.
 */
contract IERC721 is IERC165 {
    event Transfer(address indexed from, address indexed to, uint256 indexed tokenId);
    event Approval(address indexed owner, address indexed approved, uint256 indexed tokenId);
    event ApprovalForAll(address indexed owner, address indexed operator, bool approved);

    /**
     * @dev Returns the number of NFTs in `owner`'s account.
     */
    function balanceOf(address owner) public view returns (uint256 balance);

    /**
     * @dev Returns the owner of the NFT specified by `tokenId`.
     */
    function ownerOf(uint256 tokenId) public view returns (address owner);

    /**
     * @dev Transfers a specific NFT (`tokenId`) from one account (`from`) to
     * another (`to`).
     *
     *
     *
     * Requirements:
     * - `from`, `to` cannot be zero.
     * - `tokenId` must be owned by `from`.
     * - If the caller is not `from`, it must be have been allowed to move this
     * NFT by either {approve} or {setApprovalForAll}.
     */
    function safeTransferFrom(address from, address to, uint256 tokenId) public;
    /**
     * @dev Transfers a specific NFT (`tokenId`) from one account (`from`) to
     * another (`to`).
     *
     * Requirements:
     * - If the caller is not `from`, it must be approved to move this NFT by
     * either {approve} or {setApprovalForAll}.
     */
    function transferFrom(address from, address to, uint256 tokenId) public;
    function approve(address to, uint256 tokenId) public;
    function getApproved(uint256 tokenId) public view returns (address operator);

    function setApprovalForAll(address operator, bool _approved) public;
    function isApprovedForAll(address owner, address operator) public view returns (bool);


    function safeTransferFrom(address from, address to, uint256 tokenId, bytes memory data) public;
}

/*
 * @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.
 */
contract Context {
    // Empty internal constructor, to prevent people from mistakenly deploying
    // an instance of this contract, which should be used via inheritance.
    constructor () internal { }
    // solhint-disable-previous-line no-empty-blocks

    function _msgSender() internal view returns (address payable) {
        return msg.sender;
    }

    function _msgData() internal view returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}

/**
 * @title Roles
 * @dev Library for managing addresses assigned to a Role.
 */
library Roles {
    struct Role {
        mapping (address => bool) bearer;
    }

    /**
     * @dev Give an account access to this role.
     */
    function add(Role storage role, address account) internal {
        require(!has(role, account), "Roles: account already has role");
        role.bearer[account] = true;
    }

    /**
     * @dev Remove an account's access to this role.
     */
    function remove(Role storage role, address account) internal {
        require(has(role, account), "Roles: account does not have role");
        role.bearer[account] = false;
    }

    /**
     * @dev Check if an account has this role.
     * @return bool
     */
    function has(Role storage role, address account) internal view returns (bool) {
        require(account != address(0), "Roles: account is the zero address");
        return role.bearer[account];
    }
}

contract OperatorRole is Context {
    using Roles for Roles.Role;

    event OperatorAdded(address indexed account);
    event OperatorRemoved(address indexed account);

    Roles.Role private _operators;

    constructor () internal {

    }

    modifier onlyOperator() {
        require(isOperator(_msgSender()), "OperatorRole: caller does not have the Operator role");
        _;
    }

    function isOperator(address account) public view returns (bool) {
        return _operators.has(account);
    }

    function _addOperator(address account) internal {
        _operators.add(account);
        emit OperatorAdded(account);
    }

    function _removeOperator(address account) internal {
        _operators.remove(account);
        emit OperatorRemoved(account);
    }
}

/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor () internal {
        address msgSender = _msgSender();
        _owner = msgSender;
        emit OwnershipTransferred(address(0), msgSender);
    }

    /**
     * @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(isOwner(), "Ownable: caller is not the owner");
        _;
    }

    /**
     * @dev Returns true if the caller is the current owner.
     */
    function isOwner() public view returns (bool) {
        return _msgSender() == _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 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 onlyOwner {
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     */
    function _transferOwnership(address newOwner) internal {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}

contract OwnableOperatorRole is Ownable, OperatorRole {
    function addOperator(address account) external onlyOwner {
        _addOperator(account);
    }

    function removeOperator(address account) external onlyOwner {
        _removeOperator(account);
    }
}

/**
    @title ERC-1155 Multi Token Standard
    @dev See https://github.com/ethereum/EIPs/blob/master/EIPS/eip-1155.md
    Note: The ERC-165 identifier for this interface is 0xd9b67a26.
 */
contract IERC1155 is IERC165 {
    /**
        @dev Either `TransferSingle` or `TransferBatch` MUST emit when tokens are transferred, including zero value transfers as well as minting or burning (see "Safe Transfer Rules" section of the standard).
        The `_operator` argument MUST be msg.sender.
        The `_from` argument MUST be the address of the holder whose balance is decreased.
        The `_to` argument MUST be the address of the recipient whose balance is increased.
        The `_id` argument MUST be the token type being transferred.
        The `_value` argument MUST be the number of tokens the holder balance is decreased by and match what the recipient balance is increased by.
        When minting/creating tokens, the `_from` argument MUST be set to `0x0` (i.e. zero address).
        When burning/destroying tokens, the `_to` argument MUST be set to `0x0` (i.e. zero address).
    */
    event TransferSingle(address indexed _operator, address indexed _from, address indexed _to, uint256 _id, uint256 _value);

    /**
        @dev Either `TransferSingle` or `TransferBatch` MUST emit when tokens are transferred, including zero value transfers as well as minting or burning (see "Safe Transfer Rules" section of the standard).
        The `_operator` argument MUST be msg.sender.
        The `_from` argument MUST be the address of the holder whose balance is decreased.
        The `_to` argument MUST be the address of the recipient whose balance is increased.
        The `_ids` argument MUST be the list of tokens being transferred.
        The `_values` argument MUST be the list of number of tokens (matching the list and order of tokens specified in _ids) the holder balance is decreased by and match what the recipient balance is increased by.
        When minting/creating tokens, the `_from` argument MUST be set to `0x0` (i.e. zero address).
        When burning/destroying tokens, the `_to` argument MUST be set to `0x0` (i.e. zero address).
    */
    event TransferBatch(address indexed _operator, address indexed _from, address indexed _to, uint256[] _ids, uint256[] _values);

    /**
        @dev MUST emit when approval for a second party/operator address to manage all tokens for an owner address is enabled or disabled (absense of an event assumes disabled).
    */
    event ApprovalForAll(address indexed _owner, address indexed _operator, bool _approved);

    /**
        @dev MUST emit when the URI is updated for a token ID.
        URIs are defined in RFC 3986.
        The URI MUST point a JSON file that conforms to the "ERC-1155 Metadata URI JSON Schema".
    */
    event URI(string _value, uint256 indexed _id);

    /**
        @notice Transfers `_value` amount of an `_id` from the `_from` address to the `_to` address specified (with safety call).
        @dev Caller must be approved to manage the tokens being transferred out of the `_from` account (see "Approval" section of the standard).
        MUST revert if `_to` is the zero address.
        MUST revert if balance of holder for token `_id` is lower than the `_value` sent.
        MUST revert on any other error.
        MUST emit the `TransferSingle` event to reflect the balance change (see "Safe Transfer Rules" section of the standard).
        After the above conditions are met, this function MUST check if `_to` is a smart contract (e.g. code size > 0). If so, it MUST call `onERC1155Received` on `_to` and act appropriately (see "Safe Transfer Rules" section of the standard).
        @param _from    Source address
        @param _to      Target address
        @param _id      ID of the token type
        @param _value   Transfer amount
        @param _data    Additional data with no specified format, MUST be sent unaltered in call to `onERC1155Received` on `_to`
    */
    function safeTransferFrom(address _from, address _to, uint256 _id, uint256 _value, bytes calldata _data) external;

    /**
        @notice Transfers `_values` amount(s) of `_ids` from the `_from` address to the `_to` address specified (with safety call).
        @dev Caller must be approved to manage the tokens being transferred out of the `_from` account (see "Approval" section of the standard).
        MUST revert if `_to` is the zero address.
        MUST revert if length of `_ids` is not the same as length of `_values`.
        MUST revert if any of the balance(s) of the holder(s) for token(s) in `_ids` is lower than the respective amount(s) in `_values` sent to the recipient.
        MUST revert on any other error.
        MUST emit `TransferSingle` or `TransferBatch` event(s) such that all the balance changes are reflected (see "Safe Transfer Rules" section of the standard).
        Balance changes and events MUST follow the ordering of the arrays (_ids[0]/_values[0] before _ids[1]/_values[1], etc).
        After the above conditions for the transfer(s) in the batch are met, this function MUST check if `_to` is a smart contract (e.g. code size > 0). If so, it MUST call the relevant `ERC1155TokenReceiver` hook(s) on `_to` and act appropriately (see "Safe Transfer Rules" section of the standard).
        @param _from    Source address
        @param _to      Target address
        @param _ids     IDs of each token type (order and length must match _values array)
        @param _values  Transfer amounts per token type (order and length must match _ids array)
        @param _data    Additional data with no specified format, MUST be sent unaltered in call to the `ERC1155TokenReceiver` hook(s) on `_to`
    */
    function safeBatchTransferFrom(address _from, address _to, uint256[] calldata _ids, uint256[] calldata _values, bytes calldata _data) external;

    /**
        @notice Get the balance of an account's Tokens.
        @param _owner  The address of the token holder
        @param _id     ID of the Token
        @return        The _owner's balance of the Token type requested
     */
    function balanceOf(address _owner, uint256 _id) external view returns (uint256);

    /**
        @notice Get the balance of multiple account/token pairs
        @param _owners The addresses of the token holders
        @param _ids    ID of the Tokens
        @return        The _owner's balance of the Token types requested (i.e. balance for each (owner, id) pair)
     */
    function balanceOfBatch(address[] calldata _owners, uint256[] calldata _ids) external view returns (uint256[] memory);

    /**
        @notice Enable or disable approval for a third party ("operator") to manage all of the caller's tokens.
        @dev MUST emit the ApprovalForAll event on success.
        @param _operator  Address to add to the set of authorized operators
        @param _approved  True if the operator is approved, false to revoke approval
    */
    function setApprovalForAll(address _operator, bool _approved) external;

    /**
        @notice Queries the approval status of an operator for a given owner.
        @param _owner     The owner of the Tokens
        @param _operator  Address of authorized operator
        @return           True if the operator is approved, false if not
    */
    function isApprovedForAll(address _owner, address _operator) external view returns (bool);
}

contract TransferProxy is OwnableOperatorRole {

    function erc721safeTransferFrom(IERC721 token, address from, address to, uint256 tokenId) external onlyOperator {
        token.safeTransferFrom(from, to, tokenId);
    }

    function erc1155safeTransferFrom(IERC1155 token, address from, address to, uint256 id, uint256 value, bytes calldata data) external onlyOperator {
        token.safeTransferFrom(from, to, id, value, data);
    }
}

contract TransferProxyForDeprecated is OwnableOperatorRole {

    function erc721TransferFrom(IERC721 token, address from, address to, uint256 tokenId) external onlyOperator {
        token.transferFrom(from, to, tokenId);
    }
}

/**
 * @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.
     *
     * 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);
}

contract ERC20TransferProxy is OwnableOperatorRole {

    function erc20safeTransferFrom(IERC20 token, address from, address to, uint256 value) external onlyOperator {
        require(token.transferFrom(from, to, value), "failure while transferring");
    }
}

library UintLibrary {
    using SafeMath for uint;

    function toString(uint256 i) internal pure returns (string memory) {
        if (i == 0) {
            return "0";
        }
        uint j = i;
        uint len;
        while (j != 0) {
            len++;
            j /= 10;
        }
        bytes memory bstr = new bytes(len);
        uint k = len - 1;
        while (i != 0) {
            bstr[k--] = byte(uint8(48 + i % 10));
            i /= 10;
        }
        return string(bstr);
    }

    function bp(uint value, uint bpValue) internal pure returns (uint) {
        return value.mul(bpValue).div(10000);
    }
}

library StringLibrary {
    using UintLibrary for uint256;

    function append(string memory a, string memory b) internal pure returns (string memory) {
        bytes memory ba = bytes(a);
        bytes memory bb = bytes(b);
        bytes memory bab = new bytes(ba.length + bb.length);
        uint k = 0;
        for (uint i = 0; i < ba.length; i++) bab[k++] = ba[i];
        for (uint i = 0; i < bb.length; i++) bab[k++] = bb[i];
        return string(bab);
    }

    function append(string memory a, string memory b, string memory c) internal pure returns (string memory) {
        bytes memory ba = bytes(a);
        bytes memory bb = bytes(b);
        bytes memory bc = bytes(c);
        bytes memory bbb = new bytes(ba.length + bb.length + bc.length);
        uint k = 0;
        for (uint i = 0; i < ba.length; i++) bbb[k++] = ba[i];
        for (uint i = 0; i < bb.length; i++) bbb[k++] = bb[i];
        for (uint i = 0; i < bc.length; i++) bbb[k++] = bc[i];
        return string(bbb);
    }

    function recover(string memory message, uint8 v, bytes32 r, bytes32 s) internal pure returns (address) {
        bytes memory msgBytes = bytes(message);
        bytes memory fullMessage = concat(
            bytes("\x19Ethereum Signed Message:\n"),
            bytes(msgBytes.length.toString()),
            msgBytes,
            new bytes(0), new bytes(0), new bytes(0), new bytes(0)
        );
        return ecrecover(keccak256(fullMessage), v, r, s);
    }

    function concat(bytes memory ba, bytes memory bb, bytes memory bc, bytes memory bd, bytes memory be, bytes memory bf, bytes memory bg) internal pure returns (bytes memory) {
        bytes memory resultBytes = new bytes(ba.length + bb.length + bc.length + bd.length + be.length + bf.length + bg.length);
        uint k = 0;
        for (uint i = 0; i < ba.length; i++) resultBytes[k++] = ba[i];
        for (uint i = 0; i < bb.length; i++) resultBytes[k++] = bb[i];
        for (uint i = 0; i < bc.length; i++) resultBytes[k++] = bc[i];
        for (uint i = 0; i < bd.length; i++) resultBytes[k++] = bd[i];
        for (uint i = 0; i < be.length; i++) resultBytes[k++] = be[i];
        for (uint i = 0; i < bf.length; i++) resultBytes[k++] = bf[i];
        for (uint i = 0; i < bg.length; i++) resultBytes[k++] = bg[i];
        return resultBytes;
    }
}

library BytesLibrary {
    function toString(bytes32 value) internal pure returns (string memory) {
        bytes memory alphabet = "0123456789abcdef";
        bytes memory str = new bytes(64);
        for (uint256 i = 0; i < 32; i++) {
            str[i*2] = alphabet[uint8(value[i] >> 4)];
            str[1+i*2] = alphabet[uint8(value[i] & 0x0f)];
        }
        return string(str);
    }
}

contract ExchangeDomainV1 {

    enum AssetType {ETH, ERC20, ERC1155, ERC721, ERC721Deprecated}

    struct Asset {
        address token;
        uint tokenId;
        AssetType assetType;
    }

    struct OrderKey {
        /* who signed the order */
        address owner;
        /* random number */
        uint salt;

        /* what has owner */
        Asset sellAsset;

        /* what wants owner */
        Asset buyAsset;
    }

    struct Order {
        OrderKey key;

        /* how much has owner (in wei, or UINT256_MAX if ERC-721) */
        uint selling;
        /* how much wants owner (in wei, or UINT256_MAX if ERC-721) */
        uint buying;

        /* fee for selling */
        uint sellerFee;
    }

    /* An ECDSA signature. */
    struct Sig {
        /* v parameter */
        uint8 v;
        /* r parameter */
        bytes32 r;
        /* s parameter */
        bytes32 s;
    }
}

contract ExchangeStateV1 is OwnableOperatorRole {

    // keccak256(OrderKey) => completed
    mapping(bytes32 => uint256) public completed;

    function getCompleted(ExchangeDomainV1.OrderKey calldata key) view external returns (uint256) {
        return completed[getCompletedKey(key)];
    }

    function setCompleted(ExchangeDomainV1.OrderKey calldata key, uint256 newCompleted) external onlyOperator {
        completed[getCompletedKey(key)] = newCompleted;
    }

    function getCompletedKey(ExchangeDomainV1.OrderKey memory key) pure public returns (bytes32) {
        return keccak256(abi.encodePacked(key.owner, key.sellAsset.token, key.sellAsset.tokenId, key.buyAsset.token, key.buyAsset.tokenId, key.salt));
    }
}

contract ExchangeOrdersHolderV1 {

    mapping(bytes32 => OrderParams) internal orders;

    struct OrderParams {
        /* how much has owner (in wei, or UINT256_MAX if ERC-721) */
        uint selling;
        /* how much wants owner (in wei, or UINT256_MAX if ERC-721) */
        uint buying;

        /* fee for selling */
        uint sellerFee;
    }

    function add(ExchangeDomainV1.Order calldata order) external {
        require(msg.sender == order.key.owner, "order could be added by owner only");
        bytes32 key = prepareKey(order);
        orders[key] = OrderParams(order.selling, order.buying, order.sellerFee);
    }

    function exists(ExchangeDomainV1.Order calldata order) external view returns (bool) {
        bytes32 key = prepareKey(order);
        OrderParams memory params = orders[key];
        return params.buying == order.buying && params.selling == order.selling && params.sellerFee == order.sellerFee;
    }

    function prepareKey(ExchangeDomainV1.Order memory order) internal pure returns (bytes32) {
        return keccak256(abi.encode(
                order.key.sellAsset.token,
                order.key.sellAsset.tokenId,
                order.key.owner,
                order.key.buyAsset.token,
                order.key.buyAsset.tokenId,
                order.key.salt
            ));
    }
}

/**
 * @dev Implementation of the {IERC165} interface.
 *
 * Contracts may inherit from this and call {_registerInterface} to declare
 * their support of an interface.
 */
contract ERC165 is IERC165 {
    /*
     * bytes4(keccak256('supportsInterface(bytes4)')) == 0x01ffc9a7
     */
    bytes4 private constant _INTERFACE_ID_ERC165 = 0x01ffc9a7;

    /**
     * @dev Mapping of interface ids to whether or not it's supported.
     */
    mapping(bytes4 => bool) private _supportedInterfaces;

    constructor () internal {
        // Derived contracts need only register support for their own interfaces,
        // we register support for ERC165 itself here
        _registerInterface(_INTERFACE_ID_ERC165);
    }

    /**
     * @dev See {IERC165-supportsInterface}.
     *
     * Time complexity O(1), guaranteed to always use less than 30 000 gas.
     */
    function supportsInterface(bytes4 interfaceId) external view returns (bool) {
        return _supportedInterfaces[interfaceId];
    }

    /**
     * @dev Registers the contract as an implementer of the interface defined by
     * `interfaceId`. Support of the actual ERC165 interface is automatic and
     * registering its interface id is not required.
     *
     * See {IERC165-supportsInterface}.
     *
     * Requirements:
     *
     * - `interfaceId` cannot be the ERC165 invalid interface (`0xffffffff`).
     */
    function _registerInterface(bytes4 interfaceId) internal {
        require(interfaceId != 0xffffffff, "ERC165: invalid interface id");
        _supportedInterfaces[interfaceId] = true;
    }
}

contract HasSecondarySaleFees is ERC165 {

    event SecondarySaleFees(uint256 tokenId, address[] recipients, uint[] bps);

    /*
     * bytes4(keccak256('getFeeBps(uint256)')) == 0x0ebd4c7f
     * bytes4(keccak256('getFeeRecipients(uint256)')) == 0xb9c4d9fb
     *
     * => 0x0ebd4c7f ^ 0xb9c4d9fb == 0xb7799584
     */
    bytes4 private constant _INTERFACE_ID_FEES = 0xb7799584;

    constructor() public {
        _registerInterface(_INTERFACE_ID_FEES);
    }

    function getFeeRecipients(uint256 id) external view returns (address payable[] memory);
    function getFeeBps(uint256 id) external view returns (uint[] memory);
}

contract ExchangeV1 is Ownable, ExchangeDomainV1 {
    using SafeMath for uint;
    using UintLibrary for uint;
    using StringLibrary for string;
    using BytesLibrary for bytes32;

    enum FeeSide {NONE, SELL, BUY}

    event Buy(
        address indexed sellToken, uint256 indexed sellTokenId, uint256 sellValue,
        address owner,
        address buyToken, uint256 buyTokenId, uint256 buyValue,
        address buyer,
        uint256 amount,
        uint256 salt
    );

    event Cancel(
        address indexed sellToken, uint256 indexed sellTokenId,
        address owner,
        address buyToken, uint256 buyTokenId,
        uint256 salt
    );

    bytes4 private constant _INTERFACE_ID_FEES = 0xb7799584;
    uint256 private constant UINT256_MAX = 2 ** 256 - 1;

    address payable public beneficiary;
    address public buyerFeeSigner;

    TransferProxy public transferProxy;
    TransferProxyForDeprecated public transferProxyForDeprecated;
    ERC20TransferProxy public erc20TransferProxy;
    ExchangeStateV1 public state;
    ExchangeOrdersHolderV1 public ordersHolder;

    constructor(
        TransferProxy _transferProxy, TransferProxyForDeprecated _transferProxyForDeprecated, ERC20TransferProxy _erc20TransferProxy, ExchangeStateV1 _state,
        ExchangeOrdersHolderV1 _ordersHolder, address payable _beneficiary, address _buyerFeeSigner
    ) public {
        transferProxy = _transferProxy;
        transferProxyForDeprecated = _transferProxyForDeprecated;
        erc20TransferProxy = _erc20TransferProxy;
        state = _state;
        ordersHolder = _ordersHolder;
        beneficiary = _beneficiary;
        buyerFeeSigner = _buyerFeeSigner;
    }

    function setBeneficiary(address payable newBeneficiary) external onlyOwner {
        beneficiary = newBeneficiary;
    }

    function setBuyerFeeSigner(address newBuyerFeeSigner) external onlyOwner {
        buyerFeeSigner = newBuyerFeeSigner;
    }

    function exchange(
        Order calldata order,
        Sig calldata sig,
        uint buyerFee,
        Sig calldata buyerFeeSig,
        uint amount,
        address buyer
    ) payable external {
        validateOrderSig(order, sig);
        validateBuyerFeeSig(order, buyerFee, buyerFeeSig);
        uint paying = order.buying.mul(amount).div(order.selling);
        verifyOpenAndModifyOrderState(order.key, order.selling, amount);
        require(order.key.sellAsset.assetType != AssetType.ETH, "ETH is not supported on sell side");
        if (order.key.buyAsset.assetType == AssetType.ETH) {
            validateEthTransfer(paying, buyerFee);
        }
        FeeSide feeSide = getFeeSide(order.key.sellAsset.assetType, order.key.buyAsset.assetType);
        if (buyer == address(0x0)) {
            buyer = msg.sender;
        }
        transferWithFeesPossibility(order.key.sellAsset, amount, order.key.owner, buyer, feeSide == FeeSide.SELL, buyerFee, order.sellerFee, order.key.buyAsset);
        transferWithFeesPossibility(order.key.buyAsset, paying, msg.sender, order.key.owner, feeSide == FeeSide.BUY, order.sellerFee, buyerFee, order.key.sellAsset);
        emitBuy(order, amount, buyer);
    }

    function validateEthTransfer(uint value, uint buyerFee) internal view {
        uint256 buyerFeeValue = value.bp(buyerFee);
        require(msg.value == value + buyerFeeValue, "msg.value is incorrect");
    }

    function cancel(OrderKey calldata key) external {
        require(key.owner == msg.sender, "not an owner");
        state.setCompleted(key, UINT256_MAX);
        emit Cancel(key.sellAsset.token, key.sellAsset.tokenId, msg.sender, key.buyAsset.token, key.buyAsset.tokenId, key.salt);
    }

    function validateOrderSig(
        Order memory order,
        Sig memory sig
    ) internal view {
        if (sig.v == 0 && sig.r == bytes32(0x0) && sig.s == bytes32(0x0)) {
            require(ordersHolder.exists(order), "incorrect signature");
        } else {
            require(prepareMessage(order).recover(sig.v, sig.r, sig.s) == order.key.owner, "incorrect signature");
        }
    }

    function validateBuyerFeeSig(
        Order memory order,
        uint buyerFee,
        Sig memory sig
    ) internal view {
        require(prepareBuyerFeeMessage(order, buyerFee).recover(sig.v, sig.r, sig.s) == buyerFeeSigner, "incorrect buyer fee signature");
    }

    function prepareBuyerFeeMessage(Order memory order, uint fee) public pure returns (string memory) {
        return keccak256(abi.encode(order, fee)).toString();
    }

    function prepareMessage(Order memory order) public pure returns (string memory) {
        return keccak256(abi.encode(order)).toString();
    }

    function transferWithFeesPossibility(Asset memory firstType, uint value, address from, address to, bool hasFee, uint256 sellerFee, uint256 buyerFee, Asset memory secondType) internal {
        if (!hasFee) {
            transfer(firstType, value, from, to);
        } else {
            transferWithFees(firstType, value, from, to, sellerFee, buyerFee, secondType);
        }
    }

    function transfer(Asset memory asset, uint value, address from, address to) internal {
        if (asset.assetType == AssetType.ETH) {
            address payable toPayable = address(uint160(to));
            toPayable.transfer(value);
        } else if (asset.assetType == AssetType.ERC20) {
            require(asset.tokenId == 0, "tokenId should be 0");
            erc20TransferProxy.erc20safeTransferFrom(IERC20(asset.token), from, to, value);
        } else if (asset.assetType == AssetType.ERC721) {
            require(value == 1, "value should be 1 for ERC-721");
            transferProxy.erc721safeTransferFrom(IERC721(asset.token), from, to, asset.tokenId);
        } else if (asset.assetType == AssetType.ERC721Deprecated) {
            require(value == 1, "value should be 1 for ERC-721");
            transferProxyForDeprecated.erc721TransferFrom(IERC721(asset.token), from, to, asset.tokenId);
        } else {
            transferProxy.erc1155safeTransferFrom(IERC1155(asset.token), from, to, asset.tokenId, value, "");
        }
    }

    function transferWithFees(Asset memory firstType, uint value, address from, address to, uint256 sellerFee, uint256 buyerFee, Asset memory secondType) internal {
        uint restValue = transferFeeToBeneficiary(firstType, from, value, sellerFee, buyerFee);
        if (
            secondType.assetType == AssetType.ERC1155 && IERC1155(secondType.token).supportsInterface(_INTERFACE_ID_FEES) ||
            (secondType.assetType == AssetType.ERC721 || secondType.assetType == AssetType.ERC721Deprecated) && IERC721(secondType.token).supportsInterface(_INTERFACE_ID_FEES)
        ) {
            HasSecondarySaleFees withFees = HasSecondarySaleFees(secondType.token);
            address payable[] memory recipients = withFees.getFeeRecipients(secondType.tokenId);
            uint[] memory fees = withFees.getFeeBps(secondType.tokenId);
            require(fees.length == recipients.length);
            for (uint256 i = 0; i < fees.length; i++) {
                (uint newRestValue, uint current) = subFeeInBp(restValue, value, fees[i]);
                restValue = newRestValue;
                transfer(firstType, current, from, recipients[i]);
            }
        }
        address payable toPayable = address(uint160(to));
        transfer(firstType, restValue, from, toPayable);
    }

    function transferFeeToBeneficiary(Asset memory asset, address from, uint total, uint sellerFee, uint buyerFee) internal returns (uint) {
        (uint restValue, uint sellerFeeValue) = subFeeInBp(total, total, sellerFee);
        uint buyerFeeValue = total.bp(buyerFee);
        uint beneficiaryFee = buyerFeeValue.add(sellerFeeValue);
        if (beneficiaryFee > 0) {
            transfer(asset, beneficiaryFee, from, beneficiary);
        }
        return restValue;
    }

    function emitBuy(Order memory order, uint amount, address buyer) internal {
        emit Buy(order.key.sellAsset.token, order.key.sellAsset.tokenId, order.selling,
            order.key.owner,
            order.key.buyAsset.token, order.key.buyAsset.tokenId, order.buying,
            buyer,
            amount,
            order.key.salt
        );
    }

    function subFeeInBp(uint value, uint total, uint feeInBp) internal pure returns (uint newValue, uint realFee) {
        return subFee(value, total.bp(feeInBp));
    }

    function subFee(uint value, uint fee) internal pure returns (uint newValue, uint realFee) {
        if (value > fee) {
            newValue = value - fee;
            realFee = fee;
        } else {
            newValue = 0;
            realFee = value;
        }
    }

    function verifyOpenAndModifyOrderState(OrderKey memory key, uint selling, uint amount) internal {
        uint completed = state.getCompleted(key);
        uint newCompleted = completed.add(amount);
        require(newCompleted <= selling, "not enough stock of order for buying");
        state.setCompleted(key, newCompleted);
    }

    function getFeeSide(AssetType sellType, AssetType buyType) internal pure returns (FeeSide) {
        if ((sellType == AssetType.ERC721 || sellType == AssetType.ERC721Deprecated) &&
            (buyType == AssetType.ERC721 || buyType == AssetType.ERC721Deprecated)) {
            return FeeSide.NONE;
        }
        if (uint(sellType) > uint(buyType)) {
            return FeeSide.BUY;
        }
        return FeeSide.SELL;
    }
}