// File: contracts/VoucherSets.sol



// SPDX-License-Identifier: LGPL-3.0-or-later

pragma solidity 0.7.6;

import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/token/ERC1155/ERC1155.sol";
import "@openzeppelin/contracts/token/ERC1155/IERC1155Receiver.sol";
import "@openzeppelin/contracts/utils/Pausable.sol";
import "./interfaces/IVoucherKernel.sol";
import "./interfaces/IVoucherSets.sol";
import "./interfaces/ICashier.sol";

/**
 * @title Voucher sets implemented as ERC-1155
 */
contract VoucherSets is IVoucherSets, ERC1155, Ownable, Pausable {
 
    address private voucherKernelAddress; //address of the VoucherKernel contract
    address private cashierAddress; //address of the Cashier contract
    string private contractUri;

    event LogVoucherKernelSet(address _newVoucherKernel, address _triggeredBy);
    event LogCashierSet(address _newCashier, address _triggeredBy);
    event LogContractUriSet(string _contractUri, address _triggeredBy);

    modifier onlyFromVoucherKernel() {
        require(msg.sender == voucherKernelAddress, "UNAUTHORIZED_VK");
        _;
    }

    modifier notZeroAddress(address _address) {
        require(_address != address(0), "ZERO_ADDRESS");
        _;
    }

    /**
     * @notice Construct and initialze the contract. 
     * @param _uri metadata uri
     * @param _cashierAddress address of the associated Cashier contract
     * @param _voucherKernelAddress address of the associated Voucher Kernel contract
     */
    constructor(string memory _uri, address _cashierAddress, address _voucherKernelAddress) ERC1155(_uri) notZeroAddress(_cashierAddress) notZeroAddress(_voucherKernelAddress)  {
        cashierAddress = _cashierAddress;
        voucherKernelAddress = _voucherKernelAddress;
        emit LogCashierSet(_cashierAddress, msg.sender);
        emit LogVoucherKernelSet(_voucherKernelAddress, msg.sender);
    }

    /**
     * @notice Pause the process of interaction with voucherID's (ERC-721), in case of emergency.
     * Only BR contract is in control of this function.
     */
    function pause() external override onlyOwner {
        _pause();
    }

    /**
     * @notice Unpause the process of interaction with voucherID's (ERC-721).
     * Only BR contract is in control of this function.
     */
    function unpause() external override onlyOwner {
        _unpause();
    }

    /**
     * @notice Transfers amount of _tokenId from-to addresses with safety call.
     * If _to is a smart contract, will call onERC1155Received
     * @dev ERC-1155
     * @param _from    Source address
     * @param _to      Destination address
     * @param _tokenId ID of the token
     * @param _value   Transfer amount
     * @param _data    Additional data forwarded to onERC1155Received if _to is a contract
     */
    function safeTransferFrom(
        address _from,
        address _to,
        uint256 _tokenId,
        uint256 _value,
        bytes calldata _data
    )
    public
    override (ERC1155, IERC1155)
    {
        require(balanceOf(_from, _tokenId) == _value, "IQ"); //invalid qty
        super.safeTransferFrom(_from, _to, _tokenId, _value, _data);
        ICashier(cashierAddress).onVoucherSetTransfer(
            _from,
            _to,
            _tokenId,
            _value
        );
    }

    /**
        @notice Transfers amount of _tokenId from-to addresses with safety call.
        If _to is a smart contract, will call onERC1155BatchReceived
        @dev ERC-1155
        @param _from    Source address
        @param _to      Destination address
        @param _tokenIds array of token IDs
        @param _values   array of transfer amounts
        @param _data    Additional data forwarded to onERC1155BatchReceived if _to is a contract
    */
    function safeBatchTransferFrom(
        address _from,
        address _to,
        uint256[] calldata _tokenIds,
        uint256[] calldata _values,
        bytes calldata _data
    )  
        public
        override (ERC1155, IERC1155)
    {

        //Thes checks need to be called first. Code is duplicated, but super.safeBatchTransferFrom
        //must be called at the end because otherwise the balance check in the loop will always fail
        require(_tokenIds.length == _values.length, "ERC1155: ids and amounts length mismatch");
        require(_to != address(0), "ERC1155: transfer to the zero address");
        require(
            _from == _msgSender() || isApprovedForAll(_from, _msgSender()),
            "ERC1155: transfer caller is not owner nor approved"
        );
   
       

        //This is inefficient because it repeats the loop in ERC1155.safeBatchTransferFrom. However,
        //there is no other good way to call the Boson Protocol cashier contract inside the loop.
        //Doing a full override by copying the ERC1155 code doesn't work because the _balances mapping
        //is private instead of internal and can't be accesssed from this child contract

        for (uint256 i = 0; i < _tokenIds.length; ++i) {
            uint256 tokenId = _tokenIds[i];
            uint256 value = _values[i];

            //A voucher set's quantity cannot be partionally transferred. It's all or nothing
            require(balanceOf(_from, tokenId) == value, "IQ"); //invalid qty

            ICashier(cashierAddress).onVoucherSetTransfer(
                _from,
                _to,
                tokenId,
                value
            );
        }

        super.safeBatchTransferFrom(_from, _to, _tokenIds, _values, _data);
    }

    // // // // // // // //
    // STANDARD - UTILS
    // // // // // // // //
    /**
     * @notice Mint an amount of a desired token
     * Currently no restrictions as to who is allowed to mint - so, it is public.
     * @dev ERC-1155
     * @param _to       owner of the minted token
     * @param _tokenId  ID of the token to be minted
     * @param _value    Amount of the token to be minted
     * @param _data     Additional data forwarded to onERC1155BatchReceived if _to is a contract
     */
    function mint(
        address _to,
        uint256 _tokenId,
        uint256 _value,
        bytes memory _data
    ) external override onlyFromVoucherKernel {
        _mint(_to, _tokenId, _value, _data);
    }

    /**
     * @notice Batch minting of tokens
     * Currently no restrictions as to who is allowed to mint - so, it is public.
     * @dev ERC-1155
     * @param _to The address that will own the minted token
     * @param _tokenIds IDs of the tokens to be minted
     * @param _values Amounts of the tokens to be minted
     * @param _data Additional data forwarded to onERC1155BatchReceived if _to is a contract
     */
    function mintBatch(
        address _to,
        uint256[] calldata _tokenIds,
        uint256[] calldata _values,
        bytes calldata _data
    ) external onlyFromVoucherKernel {
        //require approved minter

        _mintBatch(_to, _tokenIds, _values, _data);
    }

    /**
     * @notice Burn an amount of tokens with the given ID
     * @dev ERC-1155
     * @param _account  Account which owns the token
     * @param _tokenId  ID of the token
     * @param _value    Amount of the token
     */
    function burn(
        address _account,
        uint256 _tokenId,
        uint256 _value
    ) external override onlyFromVoucherKernel {
        _burn(_account, _tokenId, _value);
    }


    /**
     * @notice Batch burn an amounts of tokens
     * @dev ERC-1155
     * @param _account Account which owns the token
     * @param _tokenIds IDs of the tokens
     * @param _values Amounts of the tokens
     */
    function burnBatch(
        address _account,
        uint256[] calldata _tokenIds,
        uint256[] calldata _values
    ) external onlyFromVoucherKernel {
        _burnBatch(_account, _tokenIds, _values);
    }

    // // // // // // // //
    // METADATA EXTENSIONS
    // // // // // // // //

    /**
     * @dev Sets a new URI for all token types, by relying on the token type ID
     * substitution mechanism
     * https://eips.ethereum.org/EIPS/eip-1155#metadata[defined in the EIP].
     *
     * By this mechanism, any occurrence of the `\{id\}` substring in either the
     * URI or any of the amounts in the JSON file at said URI will be replaced by
     * clients with the token type ID.
     *
     * For example, the `https://token-cdn-domain/\{id\}.json` URI would be
     * interpreted by clients as
     * `https://token-cdn-domain/000000000000000000000000000000000000000000000000000000000004cce0.json`
     * for token type ID 0x4cce0.
     *
     * See {uri}.
     *
     * Because these URIs cannot be meaningfully represented by the {URI} event,
     * this function emits no events.
     * @param _newUri   New uri to be used
     */
    function setUri(string memory _newUri) external onlyOwner {
        _setURI(_newUri);
    }

    /**
     * @notice Setting a contractURI for OpenSea collections integration.
     * @param _contractUri   The contract URI to be used
     */
    function setContractUri(string memory _contractUri) external onlyOwner {
        require(bytes(_contractUri).length != 0, "INVALID_VALUE");
        contractUri = _contractUri;
        emit LogContractUriSet(_contractUri, msg.sender);
    }

    // // // // // // // //
    // UTILS
    // // // // // // // //

    /**
     * @notice Set the address of the VoucherKernel contract
     * @param _voucherKernelAddress   The address of the Voucher Kernel contract
     */
    function setVoucherKernelAddress(address _voucherKernelAddress)
        external
        override
        onlyOwner
        notZeroAddress(_voucherKernelAddress)
        whenPaused
    {
        voucherKernelAddress = _voucherKernelAddress;

        emit LogVoucherKernelSet(_voucherKernelAddress, msg.sender);
    }

    /**
     * @notice Set the address of the cashier contract
     * @param _cashierAddress   The Cashier contract
     */
    function setCashierAddress(address _cashierAddress)
        external
        override
        onlyOwner
        notZeroAddress(_cashierAddress)
        whenPaused
    {
        cashierAddress = _cashierAddress;
        emit LogCashierSet(_cashierAddress, msg.sender);
    }

    /**
     * @notice Get the address of Voucher Kernel contract
     * @return Address of Voucher Kernel contract
     */
    function getVoucherKernelAddress()
        external
        view
        override
        returns (address)
    {
        return voucherKernelAddress;
    }

    /**
     * @notice Get the address of Cashier contract
     * @return Address of Cashier address
     */
    function getCashierAddress()
        external
        view
        override
        returns (address)
    {
        return cashierAddress;
    }

    /**
     * @notice Get the contractURI for Opensea collections integration
     * @return Contract URI
     */
    function contractURI() public view returns (string memory) {
        return contractUri;
    }
}

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



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

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

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

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor () {
        address msgSender = _msgSender();
        _owner = msgSender;
        emit OwnershipTransferred(address(0), msgSender);
    }

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

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

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

// File: @openzeppelin/contracts/token/ERC1155/ERC1155.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

import "./IERC1155.sol";
import "./IERC1155MetadataURI.sol";
import "./IERC1155Receiver.sol";
import "../../utils/Context.sol";
import "../../introspection/ERC165.sol";
import "../../math/SafeMath.sol";
import "../../utils/Address.sol";

/**
 *
 * @dev Implementation of the basic standard multi-token.
 * See https://eips.ethereum.org/EIPS/eip-1155
 * Originally based on code by Enjin: https://github.com/enjin/erc-1155
 *
 * _Available since v3.1._
 */
contract ERC1155 is Context, ERC165, IERC1155, IERC1155MetadataURI {
    using SafeMath for uint256;
    using Address for address;

    // Mapping from token ID to account balances
    mapping (uint256 => mapping(address => uint256)) private _balances;

    // Mapping from account to operator approvals
    mapping (address => mapping(address => bool)) private _operatorApprovals;

    // Used as the URI for all token types by relying on ID substitution, e.g. https://token-cdn-domain/{id}.json
    string private _uri;

    /*
     *     bytes4(keccak256('balanceOf(address,uint256)')) == 0x00fdd58e
     *     bytes4(keccak256('balanceOfBatch(address[],uint256[])')) == 0x4e1273f4
     *     bytes4(keccak256('setApprovalForAll(address,bool)')) == 0xa22cb465
     *     bytes4(keccak256('isApprovedForAll(address,address)')) == 0xe985e9c5
     *     bytes4(keccak256('safeTransferFrom(address,address,uint256,uint256,bytes)')) == 0xf242432a
     *     bytes4(keccak256('safeBatchTransferFrom(address,address,uint256[],uint256[],bytes)')) == 0x2eb2c2d6
     *
     *     => 0x00fdd58e ^ 0x4e1273f4 ^ 0xa22cb465 ^
     *        0xe985e9c5 ^ 0xf242432a ^ 0x2eb2c2d6 == 0xd9b67a26
     */
    bytes4 private constant _INTERFACE_ID_ERC1155 = 0xd9b67a26;

    /*
     *     bytes4(keccak256('uri(uint256)')) == 0x0e89341c
     */
    bytes4 private constant _INTERFACE_ID_ERC1155_METADATA_URI = 0x0e89341c;

    /**
     * @dev See {_setURI}.
     */
    constructor (string memory uri_) {
        _setURI(uri_);

        // register the supported interfaces to conform to ERC1155 via ERC165
        _registerInterface(_INTERFACE_ID_ERC1155);

        // register the supported interfaces to conform to ERC1155MetadataURI via ERC165
        _registerInterface(_INTERFACE_ID_ERC1155_METADATA_URI);
    }

    /**
     * @dev See {IERC1155MetadataURI-uri}.
     *
     * This implementation returns the same URI for *all* token types. It relies
     * on the token type ID substitution mechanism
     * https://eips.ethereum.org/EIPS/eip-1155#metadata[defined in the EIP].
     *
     * Clients calling this function must replace the `\{id\}` substring with the
     * actual token type ID.
     */
    function uri(uint256) external view virtual override returns (string memory) {
        return _uri;
    }

    /**
     * @dev See {IERC1155-balanceOf}.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     */
    function balanceOf(address account, uint256 id) public view virtual override returns (uint256) {
        require(account != address(0), "ERC1155: balance query for the zero address");
        return _balances[id][account];
    }

    /**
     * @dev See {IERC1155-balanceOfBatch}.
     *
     * Requirements:
     *
     * - `accounts` and `ids` must have the same length.
     */
    function balanceOfBatch(
        address[] memory accounts,
        uint256[] memory ids
    )
        public
        view
        virtual
        override
        returns (uint256[] memory)
    {
        require(accounts.length == ids.length, "ERC1155: accounts and ids length mismatch");

        uint256[] memory batchBalances = new uint256[](accounts.length);

        for (uint256 i = 0; i < accounts.length; ++i) {
            batchBalances[i] = balanceOf(accounts[i], ids[i]);
        }

        return batchBalances;
    }

    /**
     * @dev See {IERC1155-setApprovalForAll}.
     */
    function setApprovalForAll(address operator, bool approved) public virtual override {
        require(_msgSender() != operator, "ERC1155: setting approval status for self");

        _operatorApprovals[_msgSender()][operator] = approved;
        emit ApprovalForAll(_msgSender(), operator, approved);
    }

    /**
     * @dev See {IERC1155-isApprovedForAll}.
     */
    function isApprovedForAll(address account, address operator) public view virtual override returns (bool) {
        return _operatorApprovals[account][operator];
    }

    /**
     * @dev See {IERC1155-safeTransferFrom}.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 id,
        uint256 amount,
        bytes memory data
    )
        public
        virtual
        override
    {
        require(to != address(0), "ERC1155: transfer to the zero address");
        require(
            from == _msgSender() || isApprovedForAll(from, _msgSender()),
            "ERC1155: caller is not owner nor approved"
        );

        address operator = _msgSender();

        _beforeTokenTransfer(operator, from, to, _asSingletonArray(id), _asSingletonArray(amount), data);

        _balances[id][from] = _balances[id][from].sub(amount, "ERC1155: insufficient balance for transfer");
        _balances[id][to] = _balances[id][to].add(amount);

        emit TransferSingle(operator, from, to, id, amount);

        _doSafeTransferAcceptanceCheck(operator, from, to, id, amount, data);
    }

    /**
     * @dev See {IERC1155-safeBatchTransferFrom}.
     */
    function safeBatchTransferFrom(
        address from,
        address to,
        uint256[] memory ids,
        uint256[] memory amounts,
        bytes memory data
    )
        public
        virtual
        override
    {
        require(ids.length == amounts.length, "ERC1155: ids and amounts length mismatch");
        require(to != address(0), "ERC1155: transfer to the zero address");
        require(
            from == _msgSender() || isApprovedForAll(from, _msgSender()),
            "ERC1155: transfer caller is not owner nor approved"
        );

        address operator = _msgSender();

        _beforeTokenTransfer(operator, from, to, ids, amounts, data);

        for (uint256 i = 0; i < ids.length; ++i) {
            uint256 id = ids[i];
            uint256 amount = amounts[i];

            _balances[id][from] = _balances[id][from].sub(
                amount,
                "ERC1155: insufficient balance for transfer"
            );
            _balances[id][to] = _balances[id][to].add(amount);
        }

        emit TransferBatch(operator, from, to, ids, amounts);

        _doSafeBatchTransferAcceptanceCheck(operator, from, to, ids, amounts, data);
    }

    /**
     * @dev Sets a new URI for all token types, by relying on the token type ID
     * substitution mechanism
     * https://eips.ethereum.org/EIPS/eip-1155#metadata[defined in the EIP].
     *
     * By this mechanism, any occurrence of the `\{id\}` substring in either the
     * URI or any of the amounts in the JSON file at said URI will be replaced by
     * clients with the token type ID.
     *
     * For example, the `https://token-cdn-domain/\{id\}.json` URI would be
     * interpreted by clients as
     * `https://token-cdn-domain/000000000000000000000000000000000000000000000000000000000004cce0.json`
     * for token type ID 0x4cce0.
     *
     * See {uri}.
     *
     * Because these URIs cannot be meaningfully represented by the {URI} event,
     * this function emits no events.
     */
    function _setURI(string memory newuri) internal virtual {
        _uri = newuri;
    }

    /**
     * @dev Creates `amount` tokens of token type `id`, and assigns them to `account`.
     *
     * Emits a {TransferSingle} event.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     * - If `account` refers to a smart contract, it must implement {IERC1155Receiver-onERC1155Received} and return the
     * acceptance magic value.
     */
    function _mint(address account, uint256 id, uint256 amount, bytes memory data) internal virtual {
        require(account != address(0), "ERC1155: mint to the zero address");

        address operator = _msgSender();

        _beforeTokenTransfer(operator, address(0), account, _asSingletonArray(id), _asSingletonArray(amount), data);

        _balances[id][account] = _balances[id][account].add(amount);
        emit TransferSingle(operator, address(0), account, id, amount);

        _doSafeTransferAcceptanceCheck(operator, address(0), account, id, amount, data);
    }

    /**
     * @dev xref:ROOT:erc1155.adoc#batch-operations[Batched] version of {_mint}.
     *
     * Requirements:
     *
     * - `ids` and `amounts` must have the same length.
     * - If `to` refers to a smart contract, it must implement {IERC1155Receiver-onERC1155BatchReceived} and return the
     * acceptance magic value.
     */
    function _mintBatch(address to, uint256[] memory ids, uint256[] memory amounts, bytes memory data) internal virtual {
        require(to != address(0), "ERC1155: mint to the zero address");
        require(ids.length == amounts.length, "ERC1155: ids and amounts length mismatch");

        address operator = _msgSender();

        _beforeTokenTransfer(operator, address(0), to, ids, amounts, data);

        for (uint i = 0; i < ids.length; i++) {
            _balances[ids[i]][to] = amounts[i].add(_balances[ids[i]][to]);
        }

        emit TransferBatch(operator, address(0), to, ids, amounts);

        _doSafeBatchTransferAcceptanceCheck(operator, address(0), to, ids, amounts, data);
    }

    /**
     * @dev Destroys `amount` tokens of token type `id` from `account`
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     * - `account` must have at least `amount` tokens of token type `id`.
     */
    function _burn(address account, uint256 id, uint256 amount) internal virtual {
        require(account != address(0), "ERC1155: burn from the zero address");

        address operator = _msgSender();

        _beforeTokenTransfer(operator, account, address(0), _asSingletonArray(id), _asSingletonArray(amount), "");

        _balances[id][account] = _balances[id][account].sub(
            amount,
            "ERC1155: burn amount exceeds balance"
        );

        emit TransferSingle(operator, account, address(0), id, amount);
    }

    /**
     * @dev xref:ROOT:erc1155.adoc#batch-operations[Batched] version of {_burn}.
     *
     * Requirements:
     *
     * - `ids` and `amounts` must have the same length.
     */
    function _burnBatch(address account, uint256[] memory ids, uint256[] memory amounts) internal virtual {
        require(account != address(0), "ERC1155: burn from the zero address");
        require(ids.length == amounts.length, "ERC1155: ids and amounts length mismatch");

        address operator = _msgSender();

        _beforeTokenTransfer(operator, account, address(0), ids, amounts, "");

        for (uint i = 0; i < ids.length; i++) {
            _balances[ids[i]][account] = _balances[ids[i]][account].sub(
                amounts[i],
                "ERC1155: burn amount exceeds balance"
            );
        }

        emit TransferBatch(operator, account, address(0), ids, amounts);
    }

    /**
     * @dev Hook that is called before any token transfer. This includes minting
     * and burning, as well as batched variants.
     *
     * The same hook is called on both single and batched variants. For single
     * transfers, the length of the `id` and `amount` arrays will be 1.
     *
     * Calling conditions (for each `id` and `amount` pair):
     *
     * - When `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * of token type `id` will be  transferred to `to`.
     * - When `from` is zero, `amount` tokens of token type `id` will be minted
     * for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens of token type `id`
     * will be burned.
     * - `from` and `to` are never both zero.
     * - `ids` and `amounts` have the same, non-zero length.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _beforeTokenTransfer(
        address operator,
        address from,
        address to,
        uint256[] memory ids,
        uint256[] memory amounts,
        bytes memory data
    )
        internal
        virtual
    { }

    function _doSafeTransferAcceptanceCheck(
        address operator,
        address from,
        address to,
        uint256 id,
        uint256 amount,
        bytes memory data
    )
        private
    {
        if (to.isContract()) {
            try IERC1155Receiver(to).onERC1155Received(operator, from, id, amount, data) returns (bytes4 response) {
                if (response != IERC1155Receiver(to).onERC1155Received.selector) {
                    revert("ERC1155: ERC1155Receiver rejected tokens");
                }
            } catch Error(string memory reason) {
                revert(reason);
            } catch {
                revert("ERC1155: transfer to non ERC1155Receiver implementer");
            }
        }
    }

    function _doSafeBatchTransferAcceptanceCheck(
        address operator,
        address from,
        address to,
        uint256[] memory ids,
        uint256[] memory amounts,
        bytes memory data
    )
        private
    {
        if (to.isContract()) {
            try IERC1155Receiver(to).onERC1155BatchReceived(operator, from, ids, amounts, data) returns (bytes4 response) {
                if (response != IERC1155Receiver(to).onERC1155BatchReceived.selector) {
                    revert("ERC1155: ERC1155Receiver rejected tokens");
                }
            } catch Error(string memory reason) {
                revert(reason);
            } catch {
                revert("ERC1155: transfer to non ERC1155Receiver implementer");
            }
        }
    }

    function _asSingletonArray(uint256 element) private pure returns (uint256[] memory) {
        uint256[] memory array = new uint256[](1);
        array[0] = element;

        return array;
    }
}

// File: @openzeppelin/contracts/token/ERC1155/IERC1155Receiver.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

import "../../introspection/IERC165.sol";

/**
 * _Available since v3.1._
 */
interface IERC1155Receiver is IERC165 {

    /**
        @dev Handles the receipt of a single ERC1155 token type. This function is
        called at the end of a `safeTransferFrom` after the balance has been updated.
        To accept the transfer, this must return
        `bytes4(keccak256("onERC1155Received(address,address,uint256,uint256,bytes)"))`
        (i.e. 0xf23a6e61, or its own function selector).
        @param operator The address which initiated the transfer (i.e. msg.sender)
        @param from The address which previously owned the token
        @param id The ID of the token being transferred
        @param value The amount of tokens being transferred
        @param data Additional data with no specified format
        @return `bytes4(keccak256("onERC1155Received(address,address,uint256,uint256,bytes)"))` if transfer is allowed
    */
    function onERC1155Received(
        address operator,
        address from,
        uint256 id,
        uint256 value,
        bytes calldata data
    )
        external
        returns(bytes4);

    /**
        @dev Handles the receipt of a multiple ERC1155 token types. This function
        is called at the end of a `safeBatchTransferFrom` after the balances have
        been updated. To accept the transfer(s), this must return
        `bytes4(keccak256("onERC1155BatchReceived(address,address,uint256[],uint256[],bytes)"))`
        (i.e. 0xbc197c81, or its own function selector).
        @param operator The address which initiated the batch transfer (i.e. msg.sender)
        @param from The address which previously owned the token
        @param ids An array containing ids of each token being transferred (order and length must match values array)
        @param values An array containing amounts of each token being transferred (order and length must match ids array)
        @param data Additional data with no specified format
        @return `bytes4(keccak256("onERC1155BatchReceived(address,address,uint256[],uint256[],bytes)"))` if transfer is allowed
    */
    function onERC1155BatchReceived(
        address operator,
        address from,
        uint256[] calldata ids,
        uint256[] calldata values,
        bytes calldata data
    )
        external
        returns(bytes4);
}

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



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

import "./Context.sol";

/**
 * @dev Contract module which allows children to implement an emergency stop
 * mechanism that can be triggered by an authorized account.
 *
 * This module is used through inheritance. It will make available the
 * modifiers `whenNotPaused` and `whenPaused`, which can be applied to
 * the functions of your contract. Note that they will not be pausable by
 * simply including this module, only once the modifiers are put in place.
 */
abstract contract Pausable is Context {
    /**
     * @dev Emitted when the pause is triggered by `account`.
     */
    event Paused(address account);

    /**
     * @dev Emitted when the pause is lifted by `account`.
     */
    event Unpaused(address account);

    bool private _paused;

    /**
     * @dev Initializes the contract in unpaused state.
     */
    constructor () {
        _paused = false;
    }

    /**
     * @dev Returns true if the contract is paused, and false otherwise.
     */
    function paused() public view virtual returns (bool) {
        return _paused;
    }

    /**
     * @dev Modifier to make a function callable only when the contract is not paused.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    modifier whenNotPaused() {
        require(!paused(), "Pausable: paused");
        _;
    }

    /**
     * @dev Modifier to make a function callable only when the contract is paused.
     *
     * Requirements:
     *
     * - The contract must be paused.
     */
    modifier whenPaused() {
        require(paused(), "Pausable: not paused");
        _;
    }

    /**
     * @dev Triggers stopped state.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    function _pause() internal virtual whenNotPaused {
        _paused = true;
        emit Paused(_msgSender());
    }

    /**
     * @dev Returns to normal state.
     *
     * Requirements:
     *
     * - The contract must be paused.
     */
    function _unpause() internal virtual whenPaused {
        _paused = false;
        emit Unpaused(_msgSender());
    }
}

// File: contracts/interfaces/IVoucherKernel.sol



// SPDX-License-Identifier: LGPL-3.0-or-later
pragma solidity 0.7.6;

import "./../UsingHelpers.sol";

interface IVoucherKernel {
    /**
     * @notice Pause the process of interaction with voucherID's (ERC-721), in case of emergency.
     * Only Cashier contract is in control of this function.
     */
    function pause() external;

    /**
     * @notice Unpause the process of interaction with voucherID's (ERC-721).
     * Only Cashier contract is in control of this function.
     */
    function unpause() external;

    /**
     * @notice Creating a new promise for goods or services.
     * Can be reused, e.g. for making different batches of these (but not in prototype).
     * @param _seller      seller of the promise
     * @param _validFrom   Start of valid period
     * @param _validTo     End of valid period
     * @param _price       Price (payment amount)
     * @param _depositSe   Seller's deposit
     * @param _depositBu   Buyer's deposit
     */
    function createTokenSupplyId(
        address _seller,
        uint256 _validFrom,
        uint256 _validTo,
        uint256 _price,
        uint256 _depositSe,
        uint256 _depositBu,
        uint256 _quantity
    ) external returns (uint256);

    /**
     * @notice Creates a Payment method struct recording the details on how the seller requires to receive Price and Deposits for a certain Voucher Set.
     * @param _tokenIdSupply     _tokenIdSupply of the voucher set this is related to
     * @param _paymentMethod  might be ETHETH, ETHTKN, TKNETH or TKNTKN
     * @param _tokenPrice   token address which will hold the funds for the price of the voucher
     * @param _tokenDeposits   token address which will hold the funds for the deposits of the voucher
     */
    function createPaymentMethod(
        uint256 _tokenIdSupply,
        PaymentMethod _paymentMethod,
        address _tokenPrice,
        address _tokenDeposits
    ) external;

    /**
     * @notice Mark voucher token that the payment was released
     * @param _tokenIdVoucher   ID of the voucher token
     */
    function setPaymentReleased(uint256 _tokenIdVoucher) external;

    /**
     * @notice Mark voucher token that the deposits were released
     * @param _tokenIdVoucher   ID of the voucher token
     * @param _to               recipient, one of {ISSUER, HOLDER, POOL}
     * @param _amount           amount that was released in the transaction
     */
    function setDepositsReleased(
        uint256 _tokenIdVoucher,
        Entity _to,
        uint256 _amount
    ) external;

    /**
     * @notice Tells if part of the deposit, belonging to entity, was released already
     * @param _tokenIdVoucher   ID of the voucher token
     * @param _to               recipient, one of {ISSUER, HOLDER, POOL}
     */
    function isDepositReleased(uint256 _tokenIdVoucher, Entity _to)
        external
        returns (bool);

    /**
     * @notice Redemption of the vouchers promise
     * @param _tokenIdVoucher   ID of the voucher
     * @param _messageSender owner of the voucher
     */
    function redeem(uint256 _tokenIdVoucher, address _messageSender) external;

    /**
     * @notice Refunding a voucher
     * @param _tokenIdVoucher   ID of the voucher
     * @param _messageSender owner of the voucher
     */
    function refund(uint256 _tokenIdVoucher, address _messageSender) external;

    /**
     * @notice Issue a complain for a voucher
     * @param _tokenIdVoucher   ID of the voucher
     * @param _messageSender owner of the voucher
     */
    function complain(uint256 _tokenIdVoucher, address _messageSender) external;

    /**
     * @notice Cancel/Fault transaction by the Seller, admitting to a fault or backing out of the deal
     * @param _tokenIdVoucher   ID of the voucher
     * @param _messageSender owner of the voucher set (seller)
     */
    function cancelOrFault(uint256 _tokenIdVoucher, address _messageSender)
        external;

    /**
     * @notice Cancel/Fault transaction by the Seller, cancelling the remaining uncommitted voucher set so that seller prevents buyers from committing to vouchers for items no longer in exchange.
     * @param _tokenIdSupply   ID of the voucher
     * @param _issuer   owner of the voucher
     */
    function cancelOrFaultVoucherSet(uint256 _tokenIdSupply, address _issuer)
        external
        returns (uint256);

    /**
     * @notice Fill Voucher Order, iff funds paid, then extract & mint NFT to the voucher holder
     * @param _tokenIdSupply   ID of the supply token (ERC-1155)
     * @param _issuer          Address of the token's issuer
     * @param _holder          Address of the recipient of the voucher (ERC-721)
     * @param _paymentMethod   method being used for that particular order that needs to be fulfilled
     */
    function fillOrder(
        uint256 _tokenIdSupply,
        address _issuer,
        address _holder,
        PaymentMethod _paymentMethod
    ) external;

    /**
     * @notice Mark voucher token as expired
     * @param _tokenIdVoucher   ID of the voucher token
     */
    function triggerExpiration(uint256 _tokenIdVoucher) external;

    /**
     * @notice Mark voucher token to the final status
     * @param _tokenIdVoucher   ID of the voucher token
     */
    function triggerFinalizeVoucher(uint256 _tokenIdVoucher) external;

    /**
     * @notice Set the address of the new holder of a _tokenIdSupply on transfer
     * @param _tokenIdSupply   _tokenIdSupply which will be transferred
     * @param _newSeller   new holder of the supply
     */
    function setSupplyHolderOnTransfer(
        uint256 _tokenIdSupply,
        address _newSeller
    ) external;

    /**
     * @notice Set the general cancelOrFault period, should be used sparingly as it has significant consequences. Here done simply for demo purposes.
     * @param _cancelFaultPeriod   the new value for cancelOrFault period (in number of seconds)
     */
    function setCancelFaultPeriod(uint256 _cancelFaultPeriod) external;

    /**
     * @notice Set the address of the Boson Router contract
     * @param _bosonRouterAddress   The address of the BR contract
     */
    function setBosonRouterAddress(address _bosonRouterAddress) external;

    /**
     * @notice Set the address of the Cashier contract
     * @param _cashierAddress   The address of the Cashier contract
     */
    function setCashierAddress(address _cashierAddress) external;

    /**
     * @notice Set the address of the Vouchers token contract, an ERC721 contract
     * @param _voucherTokenAddress   The address of the Vouchers token contract
     */
    function setVoucherTokenAddress(address _voucherTokenAddress) external;

    /**
     * @notice Set the address of the Voucher Sets token contract, an ERC1155 contract
     * @param _voucherSetTokenAddress   The address of the Voucher Sets token contract
     */
    function setVoucherSetTokenAddress(address _voucherSetTokenAddress)
        external;

    /**
     * @notice Set the general complain period, should be used sparingly as it has significant consequences. Here done simply for demo purposes.
     * @param _complainPeriod   the new value for complain period (in number of seconds)
     */
    function setComplainPeriod(uint256 _complainPeriod) external;

    /**
     * @notice Get the promise ID at specific index
     * @param _idx  Index in the array of promise keys
     * @return      Promise ID
     */
    function getPromiseKey(uint256 _idx) external view returns (bytes32);

    /**
     * @notice Get the address of the token where the price for the supply is held
     * @param _tokenIdSupply   ID of the voucher token
     * @return                  Address of the token
     */
    function getVoucherPriceToken(uint256 _tokenIdSupply)
        external
        view
        returns (address);

    /**
     * @notice Get the address of the token where the deposits for the supply are held
     * @param _tokenIdSupply   ID of the voucher token
     * @return                  Address of the token
     */
    function getVoucherDepositToken(uint256 _tokenIdSupply)
        external
        view
        returns (address);

    /**
     * @notice Get Buyer costs required to make an order for a supply token
     * @param _tokenIdSupply   ID of the supply token
     * @return                  returns a tuple (Payment amount, Buyer's deposit)
     */
    function getBuyerOrderCosts(uint256 _tokenIdSupply)
        external
        view
        returns (uint256, uint256);

    /**
     * @notice Get Seller deposit
     * @param _tokenIdSupply   ID of the supply token
     * @return                  returns sellers deposit
     */
    function getSellerDeposit(uint256 _tokenIdSupply)
        external
        view
        returns (uint256);

    /**
     * @notice Get the promise ID from a voucher token
     * @param _tokenIdVoucher   ID of the voucher token
     * @return                  ID of the promise
     */
    function getIdSupplyFromVoucher(uint256 _tokenIdVoucher)
        external
        pure
        returns (uint256);

    /**
     * @notice Get the promise ID from a voucher token
     * @param _tokenIdVoucher   ID of the voucher token
     * @return                  ID of the promise
     */
    function getPromiseIdFromVoucherId(uint256 _tokenIdVoucher)
        external
        view
        returns (bytes32);

    /**
     * @notice Get all necessary funds for a supply token
     * @param _tokenIdSupply   ID of the supply token
     * @return                  returns a tuple (Payment amount, Seller's deposit, Buyer's deposit)
     */
    function getOrderCosts(uint256 _tokenIdSupply)
        external
        view
        returns (
            uint256,
            uint256,
            uint256
        );

    /**
     * @notice Get the remaining quantity left in supply of tokens (e.g ERC-721 left in ERC-1155) of an account
     * @param _tokenSupplyId  Token supply ID
     * @param _owner    holder of the Token Supply
     * @return          remaining quantity
     */
    function getRemQtyForSupply(uint256 _tokenSupplyId, address _owner)
        external
        view
        returns (uint256);

    /**
     * @notice Get the payment method for a particular _tokenIdSupply
     * @param _tokenIdSupply   ID of the voucher supply token
     * @return                  payment method
     */
    function getVoucherPaymentMethod(uint256 _tokenIdSupply)
        external
        view
        returns (PaymentMethod);

    /**
     * @notice Get the current status of a voucher
     * @param _tokenIdVoucher   ID of the voucher token
     * @return                  Status of the voucher (via enum)
     */
    function getVoucherStatus(uint256 _tokenIdVoucher)
        external
        view
        returns (
            uint8,
            bool,
            bool,
            uint256,
            uint256
        );

    /**
     * @notice Get the holder of a supply
     * @param _tokenIdSupply    _tokenIdSupply ID of the order (aka VoucherSet) which is mapped to the corresponding Promise.
     * @return                  Address of the holder
     */
    function getSupplyHolder(uint256 _tokenIdSupply)
        external
        view
        returns (address);

    /**
     * @notice Get the issuer of a voucher
     * @param _voucherTokenId ID of the voucher token
     * @return                Address of the seller, when voucher was created
     */
    function getVoucherSeller(uint256 _voucherTokenId)
        external
        view
        returns (address);

    /**
     * @notice Get the holder of a voucher
     * @param _tokenIdVoucher   ID of the voucher token
     * @return                  Address of the holder
     */
    function getVoucherHolder(uint256 _tokenIdVoucher)
        external
        view
        returns (address);

    /**
     * @notice Checks whether a voucher is in valid period for redemption (between start date and end date)
     * @param _tokenIdVoucher ID of the voucher token
     */
    function isInValidityPeriod(uint256 _tokenIdVoucher)
        external
        view
        returns (bool);

    /**
     * @notice Checks whether a voucher is in valid state to be transferred. If either payments or deposits are released, voucher could not be transferred
     * @param _tokenIdVoucher ID of the voucher token
     */
    function isVoucherTransferable(uint256 _tokenIdVoucher)
        external
        view
        returns (bool);

    /**
     * @notice Get address of the Boson Router contract to which this contract points
     * @return Address of the Boson Router contract
     */
    function getBosonRouterAddress() external view returns (address);

    /**
     * @notice Get address of the Cashier contract to which this contract points
     * @return Address of the Cashier contract
     */
    function getCashierAddress() external view returns (address);

    /**
     * @notice Get the token nonce for a seller
     * @param _seller Address of the seller
     * @return The seller's
     */
    function getTokenNonce(address _seller) external view returns (uint256);

    /**
     * @notice Get the current type Id
     * @return type Id
     */
    function getTypeId() external view returns (uint256);

    /**
     * @notice Get the complain period
     * @return complain period
     */
    function getComplainPeriod() external view returns (uint256);

    /**
     * @notice Get the cancel or fault period
     * @return cancel or fault period
     */
    function getCancelFaultPeriod() external view returns (uint256);

    /**
     * @notice Get promise data not retrieved by other accessor functions
     * @param _promiseKey   ID of the promise
     * @return promise data not returned by other accessor methods
     */
    function getPromiseData(bytes32 _promiseKey)
        external
        view
        returns (
            bytes32,
            uint256,
            uint256,
            uint256,
            uint256
        );

    /**
     * @notice Get the promise ID from a voucher set
     * @param _tokenIdSupply   ID of the voucher token
     * @return                  ID of the promise
     */
    function getPromiseIdFromSupplyId(uint256 _tokenIdSupply)
        external
        view
        returns (bytes32);

    /**
     * @notice Get the address of the Vouchers token contract, an ERC721 contract
     * @return Address of Vouchers contract
     */
    function getVoucherTokenAddress() external view returns (address);

    /**
     * @notice Get the address of the VoucherSets token contract, an ERC155 contract
     * @return Address of VoucherSets contract
     */
    function getVoucherSetTokenAddress() external view returns (address);
}

// File: contracts/interfaces/IVoucherSets.sol



// SPDX-License-Identifier: LGPL-3.0-or-later
pragma solidity 0.7.6;

import "@openzeppelin/contracts/token/ERC1155/IERC1155.sol";
import "@openzeppelin/contracts/token/ERC1155/IERC1155MetadataURI.sol";

interface IVoucherSets is IERC1155, IERC1155MetadataURI {
    /**
     * @notice Pause the Cashier && the Voucher Kernel contracts in case of emergency.
     * All functions related to creating new batch, requestVoucher or withdraw will be paused, hence cannot be executed.
     * There is special function for withdrawing funds if contract is paused.
     */
    function pause() external;

    /**
     * @notice Unpause the Cashier && the Voucher Kernel contracts.
     * All functions related to creating new batch, requestVoucher or withdraw will be unpaused.
     */
    function unpause() external;

    /**
     * @notice Mint an amount of a desired token
     * Currently no restrictions as to who is allowed to mint - so, it is external.
     * @dev ERC-1155
     * @param _to       owner of the minted token
     * @param _tokenId  ID of the token to be minted
     * @param _value    Amount of the token to be minted
     * @param _data     Additional data forwarded to onERC1155BatchReceived if _to is a contract
     */
    function mint(
        address _to,
        uint256 _tokenId,
        uint256 _value,
        bytes calldata _data
    ) external;

    /**
     * @notice Burn an amount of tokens with the given ID
     * @dev ERC-1155
     * @param _account  Account which owns the token
     * @param _tokenId  ID of the token
     * @param _value    Amount of the token
     */
    function burn(
        address _account,
        uint256 _tokenId,
        uint256 _value
    ) external;

    /**
     * @notice Set the address of the VoucherKernel contract
     * @param _voucherKernelAddress The address of the Voucher Kernel contract
     */
    function setVoucherKernelAddress(address _voucherKernelAddress) external;

    /**
     * @notice Set the address of the Cashier contract
     * @param _cashierAddress   The address of the Cashier contract
     */
    function setCashierAddress(address _cashierAddress) external;

    /**
     * @notice Get the address of Voucher Kernel contract
     * @return Address of Voucher Kernel contract
     */
    function getVoucherKernelAddress() external view returns (address);

    /**
     * @notice Get the address of Cashier contract
     * @return Address of Cashier address
     */
    function getCashierAddress() external view returns (address);
}

// File: contracts/interfaces/ICashier.sol



// SPDX-License-Identifier: LGPL-3.0-or-later

pragma solidity 0.7.6;

import "./../UsingHelpers.sol";

interface ICashier {
    /**
     * @notice Pause the Cashier && the Voucher Kernel contracts in case of emergency.
     * All functions related to creating new batch, requestVoucher or withdraw will be paused, hence cannot be executed.
     * There is special function for withdrawing funds if contract is paused.
     */
    function pause() external;

    /**
     * @notice Unpause the Cashier && the Voucher Kernel contracts.
     * All functions related to creating new batch, requestVoucher or withdraw will be unpaused.
     */
    function unpause() external;

    function canUnpause() external view returns (bool);

    /**
     * @notice Trigger withdrawals of what funds are releasable
     * The caller of this function triggers transfers to all involved entities (pool, issuer, token holder), also paying for gas.
     * @dev This function would be optimized a lot, here verbose for readability.
     * @param _tokenIdVoucher  ID of a voucher token (ERC-721) to try withdraw funds from
     */
    function withdraw(uint256 _tokenIdVoucher) external;

    function withdrawSingle(uint256 _tokenIdVoucher, Entity _to) external;

    /**
     * @notice External function for withdrawing deposits. Caller must be the seller of the goods, otherwise reverts.
     * @notice Seller triggers withdrawals of remaining deposits for a given supply, in case the voucher set is no longer in exchange.
     * @param _tokenIdSupply an ID of a supply token (ERC-1155) which will be burned and deposits will be returned for
     * @param _burnedQty burned quantity that the deposits should be withdrawn for
     * @param _messageSender owner of the voucher set
     */
    function withdrawDepositsSe(
        uint256 _tokenIdSupply,
        uint256 _burnedQty,
        address payable _messageSender
    ) external;

    /**
     * @notice Get the amount in escrow of an address
     * @param _account  The address of an account to query
     * @return          The balance in escrow
     */
    function getEscrowAmount(address _account) external view returns (uint256);

    /**
     * @notice Update the amount in escrow of an address with the new value, based on VoucherSet/Voucher interaction
     * @param _account  The address of an account to query
     */
    function addEscrowAmount(address _account) external payable;

    /**
     * @notice Update the amount in escrowTokens of an address with the new value, based on VoucherSet/Voucher interaction
     * @param _token  The address of a token to query
     * @param _account  The address of an account to query
     * @param _newAmount  New amount to be set
     */
    function addEscrowTokensAmount(
        address _token,
        address _account,
        uint256 _newAmount
    ) external;

    /**
     * @notice Hook which will be triggered when a _tokenIdVoucher will be transferred. Escrow funds should be allocated to the new owner.
     * @param _from prev owner of the _tokenIdVoucher
     * @param _to next owner of the _tokenIdVoucher
     * @param _tokenIdVoucher _tokenIdVoucher that has been transferred
     */
    function onVoucherTransfer(
        address _from,
        address _to,
        uint256 _tokenIdVoucher
    ) external;

    /**
     * @notice After the transfer happens the _tokenSupplyId should be updated in the promise. Escrow funds for the deposits (If in ETH) should be allocated to the new owner as well.
     * @param _from prev owner of the _tokenSupplyId
     * @param _to next owner of the _tokenSupplyId
     * @param _tokenSupplyId _tokenSupplyId for transfer
     * @param _value qty which has been transferred
     */
    function onVoucherSetTransfer(
        address _from,
        address _to,
        uint256 _tokenSupplyId,
        uint256 _value
    ) external;

    /**
     * @notice Get the address of Voucher Kernel contract
     * @return Address of Voucher Kernel contract
     */
    function getVoucherKernelAddress() external view returns (address);

    /**
     * @notice Get the address of Boson Router contract
     * @return Address of Boson Router contract
     */
    function getBosonRouterAddress() external view returns (address);

    /**
     * @notice Get the address of the Vouchers contract, an ERC721 contract
     * @return Address of Vouchers contract
     */
    function getVoucherTokenAddress() external view returns (address);

    /**
     * @notice Get the address of the VoucherSets token contract, an ERC155 contract
     * @return Address of VoucherSets contract
     */
    function getVoucherSetTokenAddress() external view returns (address);

    /**
     * @notice Ensure whether or not contract has been set to disaster state
     * @return disasterState
     */
    function isDisasterStateSet() external view returns (bool);

    /**
     * @notice Get the amount in escrow of an address
     * @param _token  The address of a token to query
     * @param _account  The address of an account to query
     * @return          The balance in escrow
     */
    function getEscrowTokensAmount(address _token, address _account)
        external
        view
        returns (uint256);

    /**
     * @notice Set the address of the BR contract
     * @param _bosonRouterAddress   The address of the Cashier contract
     */
    function setBosonRouterAddress(address _bosonRouterAddress) external;

    /**
     * @notice Set the address of the VoucherKernel contract
     * @param _voucherKernelAddress   The address of the VoucherKernel contract
     */
    function setVoucherKernelAddress(address _voucherKernelAddress) external;

    /**
     * @notice Set the address of the Vouchers token contract, an ERC721 contract
     * @param _voucherTokenAddress   The address of the Vouchers token contract
     */
    function setVoucherTokenAddress(address _voucherTokenAddress) external;

    /**
     * @notice Set the address of the Voucher Sets token contract, an ERC1155 contract
     * @param _voucherSetTokenAddress   The address of the Voucher Sets token contract
     */
    function setVoucherSetTokenAddress(address _voucherSetTokenAddress)
        external;
}

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



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/*
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with 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;
    }
}

// File: @openzeppelin/contracts/token/ERC1155/IERC1155.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

import "../../introspection/IERC165.sol";

/**
 * @dev Required interface of an ERC1155 compliant contract, as defined in the
 * https://eips.ethereum.org/EIPS/eip-1155[EIP].
 *
 * _Available since v3.1._
 */
interface IERC1155 is IERC165 {
    /**
     * @dev Emitted when `value` tokens of token type `id` are transferred from `from` to `to` by `operator`.
     */
    event TransferSingle(address indexed operator, address indexed from, address indexed to, uint256 id, uint256 value);

    /**
     * @dev Equivalent to multiple {TransferSingle} events, where `operator`, `from` and `to` are the same for all
     * transfers.
     */
    event TransferBatch(address indexed operator, address indexed from, address indexed to, uint256[] ids, uint256[] values);

    /**
     * @dev Emitted when `account` grants or revokes permission to `operator` to transfer their tokens, according to
     * `approved`.
     */
    event ApprovalForAll(address indexed account, address indexed operator, bool approved);

    /**
     * @dev Emitted when the URI for token type `id` changes to `value`, if it is a non-programmatic URI.
     *
     * If an {URI} event was emitted for `id`, the standard
     * https://eips.ethereum.org/EIPS/eip-1155#metadata-extensions[guarantees] that `value` will equal the value
     * returned by {IERC1155MetadataURI-uri}.
     */
    event URI(string value, uint256 indexed id);

    /**
     * @dev Returns the amount of tokens of token type `id` owned by `account`.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     */
    function balanceOf(address account, uint256 id) external view returns (uint256);

    /**
     * @dev xref:ROOT:erc1155.adoc#batch-operations[Batched] version of {balanceOf}.
     *
     * Requirements:
     *
     * - `accounts` and `ids` must have the same length.
     */
    function balanceOfBatch(address[] calldata accounts, uint256[] calldata ids) external view returns (uint256[] memory);

    /**
     * @dev Grants or revokes permission to `operator` to transfer the caller's tokens, according to `approved`,
     *
     * Emits an {ApprovalForAll} event.
     *
     * Requirements:
     *
     * - `operator` cannot be the caller.
     */
    function setApprovalForAll(address operator, bool approved) external;

    /**
     * @dev Returns true if `operator` is approved to transfer ``account``'s tokens.
     *
     * See {setApprovalForAll}.
     */
    function isApprovedForAll(address account, address operator) external view returns (bool);

    /**
     * @dev Transfers `amount` tokens of token type `id` from `from` to `to`.
     *
     * Emits a {TransferSingle} event.
     *
     * Requirements:
     *
     * - `to` cannot be the zero address.
     * - If the caller is not `from`, it must be have been approved to spend ``from``'s tokens via {setApprovalForAll}.
     * - `from` must have a balance of tokens of type `id` of at least `amount`.
     * - If `to` refers to a smart contract, it must implement {IERC1155Receiver-onERC1155Received} and return the
     * acceptance magic value.
     */
    function safeTransferFrom(address from, address to, uint256 id, uint256 amount, bytes calldata data) external;

    /**
     * @dev xref:ROOT:erc1155.adoc#batch-operations[Batched] version of {safeTransferFrom}.
     *
     * Emits a {TransferBatch} event.
     *
     * Requirements:
     *
     * - `ids` and `amounts` must have the same length.
     * - If `to` refers to a smart contract, it must implement {IERC1155Receiver-onERC1155BatchReceived} and return the
     * acceptance magic value.
     */
    function safeBatchTransferFrom(address from, address to, uint256[] calldata ids, uint256[] calldata amounts, bytes calldata data) external;
}

// File: @openzeppelin/contracts/token/ERC1155/IERC1155MetadataURI.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

import "./IERC1155.sol";

/**
 * @dev Interface of the optional ERC1155MetadataExtension interface, as defined
 * in the https://eips.ethereum.org/EIPS/eip-1155#metadata-extensions[EIP].
 *
 * _Available since v3.1._
 */
interface IERC1155MetadataURI is IERC1155 {
    /**
     * @dev Returns the URI for token type `id`.
     *
     * If the `\{id\}` substring is present in the URI, it must be replaced by
     * clients with the actual token type ID.
     */
    function uri(uint256 id) external view returns (string memory);
}

// File: @openzeppelin/contracts/introspection/ERC165.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

import "./IERC165.sol";

/**
 * @dev Implementation of the {IERC165} interface.
 *
 * Contracts may inherit from this and call {_registerInterface} to declare
 * their support of an interface.
 */
abstract 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 () {
        // 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) public view virtual override 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 virtual {
        require(interfaceId != 0xffffffff, "ERC165: invalid interface id");
        _supportedInterfaces[interfaceId] = true;
    }
}

// File: @openzeppelin/contracts/math/SafeMath.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

/**
 * @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;
    }
}

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



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

/**
 * @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);
            }
        }
    }
}

// File: @openzeppelin/contracts/introspection/IERC165.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

/**
 * @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);
}

// File: contracts/UsingHelpers.sol



// SPDX-License-Identifier: LGPL-3.0-or-later

pragma solidity 0.7.6;

// Those are the payment methods we are using throughout the system.
// Depending on how to user choose to interact with it's funds we store the method, so we could distribute its tokens afterwise
enum PaymentMethod {
    ETHETH,
    ETHTKN,
    TKNETH,
    TKNTKN
}

enum Entity {ISSUER, HOLDER, POOL}

enum VoucherState {FINAL, CANCEL_FAULT, COMPLAIN, EXPIRE, REFUND, REDEEM, COMMIT}
/*  Status of the voucher in 8 bits:
    [6:COMMITTED] [5:REDEEMED] [4:REFUNDED] [3:EXPIRED] [2:COMPLAINED] [1:CANCELORFAULT] [0:FINAL]
*/

enum Condition {NOT_SET, BALANCE, OWNERSHIP} //Describes what kind of condition must be met for a conditional commit

struct ConditionalCommitInfo {
    uint256 conditionalTokenId;
    uint256 threshold;
    Condition condition;
    address gateAddress;
    bool registerConditionalCommit;
}

uint8 constant ONE = 1;

struct VoucherDetails {
    uint256 tokenIdSupply;
    uint256 tokenIdVoucher;
    address issuer;
    address holder;
    uint256 price;
    uint256 depositSe;
    uint256 depositBu;
    PaymentMethod paymentMethod;
    VoucherStatus currStatus;
}

struct VoucherStatus {
    address seller;
    uint8 status;
    bool isPaymentReleased;
    bool isDepositsReleased;
    DepositsReleased depositReleased;
    uint256 complainPeriodStart;
    uint256 cancelFaultPeriodStart;
}

struct DepositsReleased {
    uint8 status;
    uint248 releasedAmount;
}

/**
    * @notice Based on its lifecycle, voucher can have many different statuses. Checks whether a voucher is in Committed state.
    * @param _status current status of a voucher.
    */
function isStateCommitted(uint8 _status) pure returns (bool) {
    return _status == determineStatus(0, VoucherState.COMMIT);
}

/**
    * @notice Based on its lifecycle, voucher can have many different statuses. Checks whether a voucher is in RedemptionSigned state.
    * @param _status current status of a voucher.
    */
function isStateRedemptionSigned(uint8 _status)
    pure
    returns (bool)
{
    return _status == determineStatus(determineStatus(0, VoucherState.COMMIT), VoucherState.REDEEM);
}

/**
    * @notice Based on its lifecycle, voucher can have many different statuses. Checks whether a voucher is in Refunded state.
    * @param _status current status of a voucher.
    */
function isStateRefunded(uint8 _status) pure returns (bool) {
    return _status == determineStatus(determineStatus(0, VoucherState.COMMIT), VoucherState.REFUND);
}

/**
    * @notice Based on its lifecycle, voucher can have many different statuses. Checks whether a voucher is in Expired state.
    * @param _status current status of a voucher.
    */
function isStateExpired(uint8 _status) pure returns (bool) {
    return _status == determineStatus(determineStatus(0, VoucherState.COMMIT), VoucherState.EXPIRE);
}

/**
    * @notice Based on its lifecycle, voucher can have many different statuses. Checks the current status a voucher is at.
    * @param _status current status of a voucher.
    * @param _idx status to compare.
    */
function isStatus(uint8 _status, VoucherState _idx) pure returns (bool) {
    return (_status >> uint8(_idx)) & ONE == 1;
}

/**
    * @notice Set voucher status.
    * @param _status previous status.
    * @param _changeIdx next status.
    */
function determineStatus(uint8 _status, VoucherState _changeIdx)
    pure
    returns (uint8)
{
    return _status | (ONE << uint8(_changeIdx));
}