Unstoppable Domains

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

pragma solidity ^0.5.0;

/**
 * @dev Interface of the ERC165 standard, as defined in the
 * [EIP](https://eips.ethereum.org/EIPS/eip-165).
 *
 * 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
     * [EIP section](https://eips.ethereum.org/EIPS/eip-165#how-interfaces-are-identified)
     * 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: @openzeppelin/contracts/token/ERC721/IERC721.sol

pragma solidity ^0.5.0;


/**
 * @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 `setApproveForAll`.
     */
    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 `setApproveForAll`.
     */
    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;
}

// File: @openzeppelin/contracts/token/ERC721/IERC721Metadata.sol

pragma solidity ^0.5.0;


/**
 * @title ERC-721 Non-Fungible Token Standard, optional metadata extension
 * @dev See https://eips.ethereum.org/EIPS/eip-721
 */
contract IERC721Metadata is IERC721 {
    function name() external view returns (string memory);
    function symbol() external view returns (string memory);
    function tokenURI(uint256 tokenId) external view returns (string memory);
}

// File: contracts/IRegistry.sol

pragma solidity 0.5.12;


contract IRegistry is IERC721Metadata {

    event NewURI(uint256 indexed tokenId, string uri);

    event NewURIPrefix(string prefix);

    event Resolve(uint256 indexed tokenId, address indexed to);

    event Sync(address indexed resolver, uint256 indexed updateId, uint256 indexed tokenId);

    /**
     * @dev Controlled function to set the token URI Prefix for all tokens.
     * @param prefix string URI to assign
     */
    function controlledSetTokenURIPrefix(string calldata prefix) external;

    /**
     * @dev Returns whether the given spender can transfer a given token ID.
     * @param spender address of the spender to query
     * @param tokenId uint256 ID of the token to be transferred
     * @return bool whether the msg.sender is approved for the given token ID,
     * is an operator of the owner, or is the owner of the token
     */
    function isApprovedOrOwner(address spender, uint256 tokenId) external view returns (bool);

    /**
     * @dev Mints a new a child token.
     * Calculates child token ID using a namehash function.
     * Requires the msg.sender to be the owner, approved, or operator of tokenId.
     * Requires the token not exist.
     * @param to address to receive the ownership of the given token ID
     * @param tokenId uint256 ID of the parent token
     * @param label subdomain label of the child token ID
     */
    function mintChild(address to, uint256 tokenId, string calldata label) external;

    /**
     * @dev Controlled function to mint a given token ID.
     * Requires the msg.sender to be controller.
     * Requires the token ID to not exist.
     * @param to address the given token ID will be minted to
     * @param label string that is a subdomain
     * @param tokenId uint256 ID of the parent token
     */
    function controlledMintChild(address to, uint256 tokenId, string calldata label) external;

    /**
     * @dev Transfers the ownership of a child token ID to another address.
     * Calculates child token ID using a namehash function.
     * Requires the msg.sender to be the owner, approved, or operator of tokenId.
     * Requires the token already exist.
     * @param from current owner of the token
     * @param to address to receive the ownership of the given token ID
     * @param tokenId uint256 ID of the token to be transferred
     * @param label subdomain label of the child token ID
     */
    function transferFromChild(address from, address to, uint256 tokenId, string calldata label) external;

    /**
     * @dev Controlled function to transfers the ownership of a token ID to
     * another address.
     * Requires the msg.sender to be controller.
     * Requires the token already exist.
     * @param from current owner of the token
     * @param to address to receive the ownership of the given token ID
     * @param tokenId uint256 ID of the token to be transferred
     */
    function controlledTransferFrom(address from, address to, uint256 tokenId) external;

    /**
     * @dev Safely transfers the ownership of a child token ID to another address.
     * Calculates child token ID using a namehash function.
     * Implements a ERC721Reciever check unlike transferFromChild.
     * Requires the msg.sender to be the owner, approved, or operator of tokenId.
     * Requires the token already exist.
     * @param from current owner of the token
     * @param to address to receive the ownership of the given token ID
     * @param tokenId uint256 parent ID of the token to be transferred
     * @param label subdomain label of the child token ID
     * @param _data bytes data to send along with a safe transfer check
     */
    function safeTransferFromChild(address from, address to, uint256 tokenId, string calldata label, bytes calldata _data) external;

    /// Shorthand for calling the above ^^^ safeTransferFromChild function with an empty _data parameter. Similar to ERC721.safeTransferFrom.
    function safeTransferFromChild(address from, address to, uint256 tokenId, string calldata label) external;

    /**
     * @dev Controlled frunction to safely transfers the ownership of a token ID
     * to another address.
     * Implements a ERC721Reciever check unlike controlledSafeTransferFrom.
     * Requires the msg.sender to be controller.
     * Requires the token already exist.
     * @param from current owner of the token
     * @param to address to receive the ownership of the given token ID
     * @param tokenId uint256 parent ID of the token to be transferred
     * @param _data bytes data to send along with a safe transfer check
     */
    function controlledSafeTransferFrom(address from, address to, uint256 tokenId, bytes calldata _data) external;

    /**
     * @dev Burns a child token ID.
     * Calculates child token ID using a namehash function.
     * Requires the msg.sender to be the owner, approved, or operator of tokenId.
     * Requires the token already exist.
     * @param tokenId uint256 ID of the token to be transferred
     * @param label subdomain label of the child token ID
     */
    function burnChild(uint256 tokenId, string calldata label) external;

    /**
     * @dev Controlled function to burn a given token ID.
     * Requires the msg.sender to be controller.
     * Requires the token already exist.
     * @param tokenId uint256 ID of the token to be burned
     */
    function controlledBurn(uint256 tokenId) external;

    /**
     * @dev Sets the resolver of a given token ID to another address.
     * Requires the msg.sender to be the owner, approved, or operator.
     * @param to address the given token ID will resolve to
     * @param tokenId uint256 ID of the token to be transferred
     */
    function resolveTo(address to, uint256 tokenId) external;

    /**
     * @dev Gets the resolver of the specified token ID.
     * @param tokenId uint256 ID of the token to query the resolver of
     * @return address currently marked as the resolver of the given token ID
     */
    function resolverOf(uint256 tokenId) external view returns (address);

    /**
     * @dev Controlled function to sets the resolver of a given token ID.
     * Requires the msg.sender to be controller.
     * @param to address the given token ID will resolve to
     * @param tokenId uint256 ID of the token to be transferred
     */
    function controlledResolveTo(address to, uint256 tokenId) external;

}

// File: @openzeppelin/contracts/token/ERC721/IERC721Receiver.sol

pragma solidity ^0.5.0;

/**
 * @title ERC721 token receiver interface
 * @dev Interface for any contract that wants to support safeTransfers
 * from ERC721 asset contracts.
 */
contract IERC721Receiver {
    /**
     * @notice Handle the receipt of an NFT
     * @dev The ERC721 smart contract calls this function on the recipient
     * after a `safeTransfer`. This function MUST return the function selector,
     * otherwise the caller will revert the transaction. The selector to be
     * returned can be obtained as `this.onERC721Received.selector`. This
     * function MAY throw to revert and reject the transfer.
     * Note: the ERC721 contract address is always the message sender.
     * @param operator The address which called `safeTransferFrom` function
     * @param from The address which previously owned the token
     * @param tokenId The NFT identifier which is being transferred
     * @param data Additional data with no specified format
     * @return bytes4 `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`
     */
    function onERC721Received(address operator, address from, uint256 tokenId, bytes memory data)
    public returns (bytes4);
}

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

pragma solidity ^0.5.0;

/**
 * @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, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

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

        return c;
    }

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

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

        return c;
    }

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

        return c;
    }

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

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

pragma solidity ^0.5.0;

/**
 * @dev Collection of functions related to the address type,
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * This test is non-exhaustive, and there may be false-negatives: during the
     * execution of a contract's constructor, its address will be reported as
     * not containing a contract.
     *
     * > It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies in 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;
    }
}

// File: @openzeppelin/contracts/drafts/Counters.sol

pragma solidity ^0.5.0;


/**
 * @title Counters
 * @author Matt Condon (@shrugs)
 * @dev Provides counters that can only be incremented or decremented by one. This can be used e.g. to track the number
 * of elements in a mapping, issuing ERC721 ids, or counting request ids.
 *
 * Include with `using Counters for Counters.Counter;`
 * Since it is not possible to overflow a 256 bit integer with increments of one, `increment` can skip the SafeMath
 * overflow check, thereby saving gas. This does assume however correct usage, in that the underlying `_value` is never
 * directly accessed.
 */
library Counters {
    using SafeMath for uint256;

    struct Counter {
        // This variable should never be directly accessed by users of the library: interactions must be restricted to
        // the library's function. As of Solidity v0.5.2, this cannot be enforced, though there is a proposal to add
        // this feature: see https://github.com/ethereum/solidity/issues/4637
        uint256 _value; // default: 0
    }

    function current(Counter storage counter) internal view returns (uint256) {
        return counter._value;
    }

    function increment(Counter storage counter) internal {
        counter._value += 1;
    }

    function decrement(Counter storage counter) internal {
        counter._value = counter._value.sub(1);
    }
}

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

pragma solidity ^0.5.0;


/**
 * @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;
    }
}

// File: @openzeppelin/contracts/token/ERC721/ERC721.sol

pragma solidity ^0.5.0;







/**
 * @title ERC721 Non-Fungible Token Standard basic implementation
 * @dev see https://eips.ethereum.org/EIPS/eip-721
 */
contract ERC721 is ERC165, IERC721 {
    using SafeMath for uint256;
    using Address for address;
    using Counters for Counters.Counter;

    // Equals to `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`
    // which can be also obtained as `IERC721Receiver(0).onERC721Received.selector`
    bytes4 private constant _ERC721_RECEIVED = 0x150b7a02;

    // Mapping from token ID to owner
    mapping (uint256 => address) private _tokenOwner;

    // Mapping from token ID to approved address
    mapping (uint256 => address) private _tokenApprovals;

    // Mapping from owner to number of owned token
    mapping (address => Counters.Counter) private _ownedTokensCount;

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

    /*
     *     bytes4(keccak256('balanceOf(address)')) == 0x70a08231
     *     bytes4(keccak256('ownerOf(uint256)')) == 0x6352211e
     *     bytes4(keccak256('approve(address,uint256)')) == 0x095ea7b3
     *     bytes4(keccak256('getApproved(uint256)')) == 0x081812fc
     *     bytes4(keccak256('setApprovalForAll(address,bool)')) == 0xa22cb465
     *     bytes4(keccak256('isApprovedForAll(address,address)')) == 0xe985e9c
     *     bytes4(keccak256('transferFrom(address,address,uint256)')) == 0x23b872dd
     *     bytes4(keccak256('safeTransferFrom(address,address,uint256)')) == 0x42842e0e
     *     bytes4(keccak256('safeTransferFrom(address,address,uint256,bytes)')) == 0xb88d4fde
     *
     *     => 0x70a08231 ^ 0x6352211e ^ 0x095ea7b3 ^ 0x081812fc ^
     *        0xa22cb465 ^ 0xe985e9c ^ 0x23b872dd ^ 0x42842e0e ^ 0xb88d4fde == 0x80ac58cd
     */
    bytes4 private constant _INTERFACE_ID_ERC721 = 0x80ac58cd;

    constructor () public {
        // register the supported interfaces to conform to ERC721 via ERC165
        _registerInterface(_INTERFACE_ID_ERC721);
    }

    /**
     * @dev Gets the balance of the specified address.
     * @param owner address to query the balance of
     * @return uint256 representing the amount owned by the passed address
     */
    function balanceOf(address owner) public view returns (uint256) {
        require(owner != address(0), "ERC721: balance query for the zero address");

        return _ownedTokensCount[owner].current();
    }

    /**
     * @dev Gets the owner of the specified token ID.
     * @param tokenId uint256 ID of the token to query the owner of
     * @return address currently marked as the owner of the given token ID
     */
    function ownerOf(uint256 tokenId) public view returns (address) {
        address owner = _tokenOwner[tokenId];
        require(owner != address(0), "ERC721: owner query for nonexistent token");

        return owner;
    }

    /**
     * @dev Approves another address to transfer the given token ID
     * The zero address indicates there is no approved address.
     * There can only be one approved address per token at a given time.
     * Can only be called by the token owner or an approved operator.
     * @param to address to be approved for the given token ID
     * @param tokenId uint256 ID of the token to be approved
     */
    function approve(address to, uint256 tokenId) public {
        address owner = ownerOf(tokenId);
        require(to != owner, "ERC721: approval to current owner");

        require(msg.sender == owner || isApprovedForAll(owner, msg.sender),
            "ERC721: approve caller is not owner nor approved for all"
        );

        _tokenApprovals[tokenId] = to;
        emit Approval(owner, to, tokenId);
    }

    /**
     * @dev Gets the approved address for a token ID, or zero if no address set
     * Reverts if the token ID does not exist.
     * @param tokenId uint256 ID of the token to query the approval of
     * @return address currently approved for the given token ID
     */
    function getApproved(uint256 tokenId) public view returns (address) {
        require(_exists(tokenId), "ERC721: approved query for nonexistent token");

        return _tokenApprovals[tokenId];
    }

    /**
     * @dev Sets or unsets the approval of a given operator
     * An operator is allowed to transfer all tokens of the sender on their behalf.
     * @param to operator address to set the approval
     * @param approved representing the status of the approval to be set
     */
    function setApprovalForAll(address to, bool approved) public {
        require(to != msg.sender, "ERC721: approve to caller");

        _operatorApprovals[msg.sender][to] = approved;
        emit ApprovalForAll(msg.sender, to, approved);
    }

    /**
     * @dev Tells whether an operator is approved by a given owner.
     * @param owner owner address which you want to query the approval of
     * @param operator operator address which you want to query the approval of
     * @return bool whether the given operator is approved by the given owner
     */
    function isApprovedForAll(address owner, address operator) public view returns (bool) {
        return _operatorApprovals[owner][operator];
    }

    /**
     * @dev Transfers the ownership of a given token ID to another address.
     * Usage of this method is discouraged, use `safeTransferFrom` whenever possible.
     * Requires the msg.sender to be the owner, approved, or operator.
     * @param from current owner of the token
     * @param to address to receive the ownership of the given token ID
     * @param tokenId uint256 ID of the token to be transferred
     */
    function transferFrom(address from, address to, uint256 tokenId) public {
        //solhint-disable-next-line max-line-length
        require(_isApprovedOrOwner(msg.sender, tokenId), "ERC721: transfer caller is not owner nor approved");

        _transferFrom(from, to, tokenId);
    }

    /**
     * @dev Safely transfers the ownership of a given token ID to another address
     * If the target address is a contract, it must implement `onERC721Received`,
     * which is called upon a safe transfer, and return the magic value
     * `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`; otherwise,
     * the transfer is reverted.
     * Requires the msg.sender to be the owner, approved, or operator
     * @param from current owner of the token
     * @param to address to receive the ownership of the given token ID
     * @param tokenId uint256 ID of the token to be transferred
     */
    function safeTransferFrom(address from, address to, uint256 tokenId) public {
        safeTransferFrom(from, to, tokenId, "");
    }

    /**
     * @dev Safely transfers the ownership of a given token ID to another address
     * If the target address is a contract, it must implement `onERC721Received`,
     * which is called upon a safe transfer, and return the magic value
     * `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`; otherwise,
     * the transfer is reverted.
     * Requires the msg.sender to be the owner, approved, or operator
     * @param from current owner of the token
     * @param to address to receive the ownership of the given token ID
     * @param tokenId uint256 ID of the token to be transferred
     * @param _data bytes data to send along with a safe transfer check
     */
    function safeTransferFrom(address from, address to, uint256 tokenId, bytes memory _data) public {
        transferFrom(from, to, tokenId);
        require(_checkOnERC721Received(from, to, tokenId, _data), "ERC721: transfer to non ERC721Receiver implementer");
    }

    /**
     * @dev Returns whether the specified token exists.
     * @param tokenId uint256 ID of the token to query the existence of
     * @return bool whether the token exists
     */
    function _exists(uint256 tokenId) internal view returns (bool) {
        address owner = _tokenOwner[tokenId];
        return owner != address(0);
    }

    /**
     * @dev Returns whether the given spender can transfer a given token ID.
     * @param spender address of the spender to query
     * @param tokenId uint256 ID of the token to be transferred
     * @return bool whether the msg.sender is approved for the given token ID,
     * is an operator of the owner, or is the owner of the token
     */
    function _isApprovedOrOwner(address spender, uint256 tokenId) internal view returns (bool) {
        require(_exists(tokenId), "ERC721: operator query for nonexistent token");
        address owner = ownerOf(tokenId);
        return (spender == owner || getApproved(tokenId) == spender || isApprovedForAll(owner, spender));
    }

    /**
     * @dev Internal function to mint a new token.
     * Reverts if the given token ID already exists.
     * @param to The address that will own the minted token
     * @param tokenId uint256 ID of the token to be minted
     */
    function _mint(address to, uint256 tokenId) internal {
        require(to != address(0), "ERC721: mint to the zero address");
        require(!_exists(tokenId), "ERC721: token already minted");

        _tokenOwner[tokenId] = to;
        _ownedTokensCount[to].increment();

        emit Transfer(address(0), to, tokenId);
    }

    /**
     * @dev Internal function to burn a specific token.
     * Reverts if the token does not exist.
     * Deprecated, use _burn(uint256) instead.
     * @param owner owner of the token to burn
     * @param tokenId uint256 ID of the token being burned
     */
    function _burn(address owner, uint256 tokenId) internal {
        require(ownerOf(tokenId) == owner, "ERC721: burn of token that is not own");

        _clearApproval(tokenId);

        _ownedTokensCount[owner].decrement();
        _tokenOwner[tokenId] = address(0);

        emit Transfer(owner, address(0), tokenId);
    }

    /**
     * @dev Internal function to burn a specific token.
     * Reverts if the token does not exist.
     * @param tokenId uint256 ID of the token being burned
     */
    function _burn(uint256 tokenId) internal {
        _burn(ownerOf(tokenId), tokenId);
    }

    /**
     * @dev Internal function to transfer ownership of a given token ID to another address.
     * As opposed to transferFrom, this imposes no restrictions on msg.sender.
     * @param from current owner of the token
     * @param to address to receive the ownership of the given token ID
     * @param tokenId uint256 ID of the token to be transferred
     */
    function _transferFrom(address from, address to, uint256 tokenId) internal {
        require(ownerOf(tokenId) == from, "ERC721: transfer of token that is not own");
        require(to != address(0), "ERC721: transfer to the zero address");

        _clearApproval(tokenId);

        _ownedTokensCount[from].decrement();
        _ownedTokensCount[to].increment();

        _tokenOwner[tokenId] = to;

        emit Transfer(from, to, tokenId);
    }

    /**
     * @dev Internal function to invoke `onERC721Received` on a target address.
     * The call is not executed if the target address is not a contract.
     *
     * This function is deprecated.
     * @param from address representing the previous owner of the given token ID
     * @param to target address that will receive the tokens
     * @param tokenId uint256 ID of the token to be transferred
     * @param _data bytes optional data to send along with the call
     * @return bool whether the call correctly returned the expected magic value
     */
    function _checkOnERC721Received(address from, address to, uint256 tokenId, bytes memory _data)
        internal returns (bool)
    {
        if (!to.isContract()) {
            return true;
        }

        bytes4 retval = IERC721Receiver(to).onERC721Received(msg.sender, from, tokenId, _data);
        return (retval == _ERC721_RECEIVED);
    }

    /**
     * @dev Private function to clear current approval of a given token ID.
     * @param tokenId uint256 ID of the token to be transferred
     */
    function _clearApproval(uint256 tokenId) private {
        if (_tokenApprovals[tokenId] != address(0)) {
            _tokenApprovals[tokenId] = address(0);
        }
    }
}

// File: @openzeppelin/contracts/token/ERC721/ERC721Burnable.sol

pragma solidity ^0.5.0;


/**
 * @title ERC721 Burnable Token
 * @dev ERC721 Token that can be irreversibly burned (destroyed).
 */
contract ERC721Burnable is ERC721 {
    /**
     * @dev Burns a specific ERC721 token.
     * @param tokenId uint256 id of the ERC721 token to be burned.
     */
    function burn(uint256 tokenId) public {
        //solhint-disable-next-line max-line-length
        require(_isApprovedOrOwner(msg.sender, tokenId), "ERC721Burnable: caller is not owner nor approved");
        _burn(tokenId);
    }
}

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

pragma solidity ^0.5.0;

/**
 * @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];
    }
}

// File: contracts/util/ControllerRole.sol

pragma solidity 0.5.12;


// solium-disable error-reason

/**
 * @title ControllerRole
 * @dev An Controller role defined using the Open Zeppelin Role system.
 */
contract ControllerRole {

    using Roles for Roles.Role;

    // NOTE: Commented out standard Role events to save gas.
    // event ControllerAdded(address indexed account);
    // event ControllerRemoved(address indexed account);

    Roles.Role private _controllers;

    constructor () public {
        _addController(msg.sender);
    }

    modifier onlyController() {
        require(isController(msg.sender));
        _;
    }

    function isController(address account) public view returns (bool) {
        return _controllers.has(account);
    }

    function addController(address account) public onlyController {
        _addController(account);
    }

    function renounceController() public {
        _removeController(msg.sender);
    }

    function _addController(address account) internal {
        _controllers.add(account);
        // emit ControllerAdded(account);
    }

    function _removeController(address account) internal {
        _controllers.remove(account);
        // emit ControllerRemoved(account);
    }

}

// File: contracts/Registry.sol

pragma solidity 0.5.12;




// solium-disable no-empty-blocks,error-reason

/**
 * @title Registry
 * @dev An ERC721 Token see https://eips.ethereum.org/EIPS/eip-721. With
 * additional functions so other trusted contracts to interact with the tokens.
 */
contract Registry is IRegistry, ControllerRole, ERC721Burnable {

    // Optional mapping for token URIs
    mapping(uint256 => string) internal _tokenURIs;

    string internal _prefix;

    // Mapping from token ID to resolver address
    mapping (uint256 => address) internal _tokenResolvers;

    // uint256(keccak256(abi.encodePacked(uint256(0x0), keccak256(abi.encodePacked("crypto")))))
    uint256 private constant _CRYPTO_HASH =
        0x0f4a10a4f46c288cea365fcf45cccf0e9d901b945b9829ccdb54c10dc3cb7a6f;

    modifier onlyApprovedOrOwner(uint256 tokenId) {
        require(_isApprovedOrOwner(msg.sender, tokenId));
        _;
    }

    constructor () public {
        _mint(address(0xdead), _CRYPTO_HASH);
        // register the supported interfaces to conform to ERC721 via ERC165
        _registerInterface(0x5b5e139f); // ERC721 Metadata Interface
        _tokenURIs[root()] = "crypto";
        emit NewURI(root(), "crypto");
    }

    /// ERC721 Metadata extension

    function name() external view returns (string memory) {
        return ".crypto";
    }

    function symbol() external view returns (string memory) {
        return "UD";
    }

    function tokenURI(uint256 tokenId) external view returns (string memory) {
        require(_exists(tokenId));
        return string(abi.encodePacked(_prefix, _tokenURIs[tokenId]));
    }

    function controlledSetTokenURIPrefix(string calldata prefix) external onlyController {
        _prefix = prefix;
        emit NewURIPrefix(prefix);
    }

    /// Ownership

    function isApprovedOrOwner(address spender, uint256 tokenId) external view returns (bool) {
        return _isApprovedOrOwner(spender, tokenId);
    }

    /// Registry Constants

    function root() public pure returns (uint256) {
        return _CRYPTO_HASH;
    }

    function childIdOf(uint256 tokenId, string calldata label) external pure returns (uint256) {
        return _childId(tokenId, label);
    }

    /// Minting

    function mintChild(address to, uint256 tokenId, string calldata label) external onlyApprovedOrOwner(tokenId) {
        _mintChild(to, tokenId, label);
    }

    function controlledMintChild(address to, uint256 tokenId, string calldata label) external onlyController {
        _mintChild(to, tokenId, label);
    }

    function safeMintChild(address to, uint256 tokenId, string calldata label) external onlyApprovedOrOwner(tokenId) {
        _safeMintChild(to, tokenId, label, "");
    }

    function safeMintChild(address to, uint256 tokenId, string calldata label, bytes calldata _data)
        external
        onlyApprovedOrOwner(tokenId)
    {
        _safeMintChild(to, tokenId, label, _data);
    }

    function controlledSafeMintChild(address to, uint256 tokenId, string calldata label, bytes calldata _data)
        external
        onlyController
    {
        _safeMintChild(to, tokenId, label, _data);
    }

    /// Transfering

    function setOwner(address to, uint256 tokenId) external onlyApprovedOrOwner(tokenId)  {
        super._transferFrom(ownerOf(tokenId), to, tokenId);
    }

    function transferFromChild(address from, address to, uint256 tokenId, string calldata label)
        external
        onlyApprovedOrOwner(tokenId)
    {
        _transferFrom(from, to, _childId(tokenId, label));
    }

    function controlledTransferFrom(address from, address to, uint256 tokenId) external onlyController {
        _transferFrom(from, to, tokenId);
    }

    function safeTransferFromChild(
        address from,
        address to,
        uint256 tokenId,
        string memory label,
        bytes memory _data
    ) public onlyApprovedOrOwner(tokenId) {
        uint256 childId = _childId(tokenId, label);
        _transferFrom(from, to, childId);
        require(_checkOnERC721Received(from, to, childId, _data));
    }

    function safeTransferFromChild(address from, address to, uint256 tokenId, string calldata label) external {
        safeTransferFromChild(from, to, tokenId, label, "");
    }

    function controlledSafeTransferFrom(address from, address to, uint256 tokenId, bytes calldata _data)
        external
        onlyController
    {
        _transferFrom(from, to, tokenId);
        require(_checkOnERC721Received(from, to, tokenId, _data));
    }

    /// Burning

    function burnChild(uint256 tokenId, string calldata label) external onlyApprovedOrOwner(tokenId) {
        _burn(_childId(tokenId, label));
    }

    function controlledBurn(uint256 tokenId) external onlyController {
        _burn(tokenId);
    }

    /// Resolution

    function resolverOf(uint256 tokenId) external view returns (address) {
        address resolver = _tokenResolvers[tokenId];
        require(resolver != address(0));
        return resolver;
    }

    function resolveTo(address to, uint256 tokenId) external onlyApprovedOrOwner(tokenId) {
        _resolveTo(to, tokenId);
    }

    function controlledResolveTo(address to, uint256 tokenId) external onlyController {
        _resolveTo(to, tokenId);
    }

    function sync(uint256 tokenId, uint256 updateId) external {
        require(_tokenResolvers[tokenId] == msg.sender);
        emit Sync(msg.sender, updateId, tokenId);
    }

    /// Internal

    function _childId(uint256 tokenId, string memory label) internal pure returns (uint256) {
        require(bytes(label).length != 0);
        return uint256(keccak256(abi.encodePacked(tokenId, keccak256(abi.encodePacked(label)))));
    }

    function _mintChild(address to, uint256 tokenId, string memory label) internal {
        uint256 childId = _childId(tokenId, label);
        _mint(to, childId);

        require(bytes(label).length != 0);
        require(_exists(childId));

        bytes memory domain = abi.encodePacked(label, ".", _tokenURIs[tokenId]);

        _tokenURIs[childId] = string(domain);
        emit NewURI(childId, string(domain));
    }

    function _safeMintChild(address to, uint256 tokenId, string memory label, bytes memory _data) internal {
        _mintChild(to, tokenId, label);
        require(_checkOnERC721Received(address(0), to, _childId(tokenId, label), _data));
    }

    function _transferFrom(address from, address to, uint256 tokenId) internal {
        super._transferFrom(from, to, tokenId);
        // Clear resolver (if any)
        if (_tokenResolvers[tokenId] != address(0x0)) {
            delete _tokenResolvers[tokenId];
        }
    }

    function _burn(uint256 tokenId) internal {
        super._burn(tokenId);
        // Clear resolver (if any)
        if (_tokenResolvers[tokenId] != address(0x0)) {
            delete _tokenResolvers[tokenId];
        }
        // Clear metadata (if any)
        if (bytes(_tokenURIs[tokenId]).length != 0) {
            delete _tokenURIs[tokenId];
        }
    }

    function _resolveTo(address to, uint256 tokenId) internal {
        require(_exists(tokenId));
        emit Resolve(tokenId, to);
        _tokenResolvers[tokenId] = to;
    }

}

{
  "compilationTarget": {
    "Registry.sol": "Registry"
  },
  "evmVersion": "petersburg",
  "libraries": {},
  "optimizer": {
    "enabled": true,
    "runs": 200
  },
  "remappings": []
}