// File: /Users/ivannikov/work/snake-jungle/cosmomasks-for-musk/contracts/CosmoMasksERC721.sol



// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;

import "./libraries/SafeMath.sol";
import "./libraries/Address.sol";
import "./libraries/EnumerableSet.sol";
import "./libraries/EnumerableMap.sol";
import "./libraries/Strings.sol";
import "./utils/Context.sol";

interface ICosmoMasksERC721 {
    // IERC165
    function supportsInterface(bytes4 interfaceId) external view returns (bool);
    // IERC721Enumerable
    function totalSupply() external view returns (uint256);
    function tokenOfOwnerByIndex(address owner, uint256 index) external view returns (uint256 tokenId);
    function tokenByIndex(uint256 index) external view returns (uint256);
    // IERC721Metadata
    function name() external view returns (string memory _name);
    function symbol() external view returns (string memory _symbol);
    function tokenURI(uint256 _tokenId) external view returns (string memory);
    // ERC721
    function balanceOf(address owner) external view returns (uint256 balance);
    function ownerOf(uint256 tokenId) external view returns (address owner);
    function safeTransferFrom(address from, address to, uint256 tokenId) external;
    function transferFrom(address from, address to, uint256 tokenId) external;
    function approve(address to, uint256 tokenId) external;
    function getApproved(uint256 tokenId) external view returns (address operator);
    function setApprovalForAll(address operator, bool _approved) external;
    function isApprovedForAll(address owner, address operator) external view returns (bool);
    function safeTransferFrom(address from, address to, uint256 tokenId, bytes calldata data) external;
    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);
}

interface IERC721Receiver {
    function onERC721Received(address operator, address from, uint256 tokenId, bytes calldata data) external returns (bytes4);
}


/**
 * @title ERC721 Non-Fungible Token Standard basic implementation
 * @dev see https://eips.ethereum.org/EIPS/eip-721
 */
abstract contract CosmoMasksERC721 is Context, ICosmoMasksERC721 {
    using SafeMath for uint256;
    using Address for address;
    using EnumerableSet for EnumerableSet.UintSet;
    using EnumerableMap for EnumerableMap.UintToAddressMap;
    using Strings for uint256;

    // ERC165
    bytes4 private constant _INTERFACE_ID_ERC165 = 0x01ffc9a7;
    mapping(bytes4 => bool) private _supportedInterfaces;

    bytes4 private constant _ERC721_RECEIVED = 0x150b7a02;
    bytes4 private constant _INTERFACE_ID_ERC721 = 0x80ac58cd;
    bytes4 private constant _INTERFACE_ID_ERC721_METADATA = 0x5b5e139f;
    bytes4 private constant _INTERFACE_ID_ERC721_METADATA_SHORT = 0x93254542;
    bytes4 private constant _INTERFACE_ID_ERC721_ENUMERABLE = 0x780e9d63;

    mapping(address => EnumerableSet.UintSet) private _holderTokens;
    EnumerableMap.UintToAddressMap private _tokenOwners;
    mapping(uint256 => address) private _tokenApprovals;
    mapping(address => mapping(address => bool)) private _operatorApprovals;

    string private _name;
    string private _symbol;
    string private _baseURI;
    string private _url;


    constructor(string memory name_, string memory symbol_) internal {
        _name = name_;
        _symbol = symbol_;

        _registerInterface(_INTERFACE_ID_ERC165);
        _registerInterface(_INTERFACE_ID_ERC721);
        _registerInterface(_INTERFACE_ID_ERC721_METADATA);
        _registerInterface(_INTERFACE_ID_ERC721_METADATA_SHORT);
        _registerInterface(_INTERFACE_ID_ERC721_ENUMERABLE);
    }

    function balanceOf(address owner) public view override returns (uint256) {
        require(owner != address(0), "CosmoMasks: balance query for the zero address");
        return _holderTokens[owner].length();
    }

    function ownerOf(uint256 tokenId) public view override returns (address) {
        return _tokenOwners.get(tokenId, "CosmoMasks: owner query for nonexistent token");
    }

    function name() public view override returns (string memory) {
        return _name;
    }

    function symbol() public view override returns (string memory) {
        return _symbol;
    }

    function tokenURI(uint256 tokenId) public view override returns (string memory) {
        require(_exists(tokenId), "CosmoMasks: URI query for nonexistent token");
        string memory base = baseURI();
        return string(abi.encodePacked(base, tokenId.toString(), ".json"));
    }

    function baseURI() public view returns (string memory) {
        return _baseURI;
    }

    function tokenOfOwnerByIndex(address owner, uint256 index) public view override returns (uint256) {
        return _holderTokens[owner].at(index);
    }

    function totalSupply() public view override returns (uint256) {
        return _tokenOwners.length();
    }

    function tokenByIndex(uint256 index) public view override returns (uint256) {
        (uint256 tokenId, ) = _tokenOwners.at(index);
        return tokenId;
    }

    function approve(address to, uint256 tokenId) public override {
        address owner = ownerOf(tokenId);
        require(to != owner, "CosmoMasks: approval to current owner");
        require(_msgSender() == owner || isApprovedForAll(owner, _msgSender()),
            "CosmoMasks: approve caller is not owner nor approved for all"
        );
        _approve(to, tokenId);
    }

    function getApproved(uint256 tokenId) public view override returns (address) {
        require(_exists(tokenId), "CosmoMasks: approved query for nonexistent token");
        return _tokenApprovals[tokenId];
    }

    function setApprovalForAll(address operator, bool approved) public override {
        require(operator != _msgSender(), "CosmoMasks: approve to caller");
        _operatorApprovals[_msgSender()][operator] = approved;
        emit ApprovalForAll(_msgSender(), operator, approved);
    }

    function isApprovedForAll(address owner, address operator) public view virtual override returns (bool) {
        return _operatorApprovals[owner][operator];
    }

    function transferFrom(address from, address to, uint256 tokenId) public override {
        require(_isApprovedOrOwner(_msgSender(), tokenId), "CosmoMasks: transfer caller is not owner nor approved");
        _transfer(from, to, tokenId);
    }

    function safeTransferFrom(address from, address to, uint256 tokenId) public override {
        safeTransferFrom(from, to, tokenId, "");
    }

    function safeTransferFrom(address from, address to, uint256 tokenId, bytes memory _data) public override {
        require(_isApprovedOrOwner(_msgSender(), tokenId), "CosmoMasks: transfer caller is not owner nor approved");
        _safeTransfer(from, to, tokenId, _data);
    }

    function _safeTransfer(address from, address to, uint256 tokenId, bytes memory _data) internal {
        _transfer(from, to, tokenId);
        require(_checkOnERC721Received(from, to, tokenId, _data), "CosmoMasks: transfer to non ERC721Receiver implementer");
    }

    function _exists(uint256 tokenId) internal view returns (bool) {
        return _tokenOwners.contains(tokenId);
    }

    function _isApprovedOrOwner(address spender, uint256 tokenId) internal view returns (bool) {
        require(_exists(tokenId), "CosmoMasks: operator query for nonexistent token");
        address owner = ownerOf(tokenId);
        return (spender == owner || getApproved(tokenId) == spender || isApprovedForAll(owner, spender));
    }

    function _safeMint(address to, uint256 tokenId) internal {
        _safeMint(to, tokenId, "");
    }

    function _safeMint(address to, uint256 tokenId, bytes memory _data) internal {
        _mint(to, tokenId);
        require(_checkOnERC721Received(address(0), to, tokenId, _data), "CosmoMasks: transfer to non ERC721Receiver implementer");
    }

    function _mint(address to, uint256 tokenId) internal {
        require(to != address(0), "CosmoMasks: mint to the zero address");
        require(!_exists(tokenId), "CosmoMasks: token already minted");
        _holderTokens[to].add(tokenId);
        _tokenOwners.set(tokenId, to);
        emit Transfer(address(0), to, tokenId);
    }

    function _burn(uint256 tokenId) internal {
        address owner = ownerOf(tokenId);
        _approve(address(0), tokenId);
        _holderTokens[owner].remove(tokenId);
        _tokenOwners.remove(tokenId);
        emit Transfer(owner, address(0), tokenId);
    }

    function _transfer(address from, address to, uint256 tokenId) internal {
        require(ownerOf(tokenId) == from, "CosmoMasks: transfer of token that is not own");
        require(to != address(0), "CosmoMasks: transfer to the zero address");
        _approve(address(0), tokenId);
        _holderTokens[from].remove(tokenId);
        _holderTokens[to].add(tokenId);
        _tokenOwners.set(tokenId, to);
        emit Transfer(from, to, tokenId);
    }

    function _setBaseURI(string memory baseURI_) internal {
        _baseURI = baseURI_;
    }

    function _checkOnERC721Received(address from, address to, uint256 tokenId, bytes memory _data) private returns (bool) {
        if (!to.isContract()) {
            return true;
        }
        bytes memory returndata = to.functionCall(abi.encodeWithSelector(
            IERC721Receiver(to).onERC721Received.selector,
            _msgSender(),
            from,
            tokenId,
            _data
        ), "CosmoMasks: transfer to non ERC721Receiver implementer");
        bytes4 retval = abi.decode(returndata, (bytes4));
        return (retval == _ERC721_RECEIVED);
    }

    function _approve(address to, uint256 tokenId) private {
        _tokenApprovals[tokenId] = to;
        emit Approval(ownerOf(tokenId), to, tokenId);
    }

    function _setURL(string memory newUrl) internal {
        _url = newUrl;
    }

    // ERC165
    function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
        return _supportedInterfaces[interfaceId];
    }

    function _registerInterface(bytes4 interfaceId) internal virtual {
        require(interfaceId != 0xffffffff, "CosmoMasks: invalid interface id");
        _supportedInterfaces[interfaceId] = true;
    }
}

// File: /Users/ivannikov/work/snake-jungle/cosmomasks-for-musk/contracts/MaskForMusk.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.7.6;

import "./utils/Ownable.sol";
import "./CosmoMasksERC721.sol";

interface IERC20BurnTransfer {
    function burn(uint256 amount) external returns (bool);
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);
}

interface ICosmoTokenMint {
    function mintToFund(uint256 amount) external returns (bool);
}


contract OwnableDelegateProxy {}
contract ProxyRegistry {
    mapping(address => OwnableDelegateProxy) public proxies;
}


// https://eips.ethereum.org/EIPS/eip-721 tokenURI
/**
 * @title MaskForMusk contract
 * @dev Extends ERC721 Non-Fungible Token Standard basic implementation
 */
contract MaskForMusk is Ownable, CosmoMasksERC721 {
    using SafeMath for uint256;

    // This is the provenance record of all MaskForMusk artwork in existence
    uint256 public constant NAME_CHANGE_PRICE = 1830e18;
    uint256 public constant MAX_SUPPLY = 7;
    string  public constant PROVENANCE = "4bda02a6364e150b73c88618f7e2e96a4f31531735bfbf29a8218a4ac8aa1756";

    // Mapping from token ID to name
    mapping(uint256 => string) private _tokenName;
    // Mapping if certain name string has already been reserved
    mapping(string => bool) private _nameReserved;

    address private _cosmoToken = 0x27cd7375478F189bdcF55616b088BE03d9c4339c;
    address private _cmpAddress = 0xB9FDc13F7f747bAEdCc356e9Da13Ab883fFa719B;
    address proxyRegistryAddress = 0xa5409ec958C83C3f309868babACA7c86DCB077c1;
    string private _contractURI;

    event NameChange(uint256 indexed tokenId, string newName);

    constructor() public CosmoMasksERC721("MaskForMusk", "MUSK") {
        _setBaseURI("https://TheCosmoMasks.com/mask-for-musk-metadata/");
        _setURL("https://TheCosmoMasks.com/");
        _contractURI = "https://TheCosmoMasks.com/mask-for-musk-contract-metadata.json";
    }

    function getCosmoToken() public view returns (address) {
        return _cosmoToken;
    }

    function contractURI() public view returns (string memory) {
        return _contractURI;
    }

    /**
     * @dev Returns name of the CosmoMask at index.
     */
    function tokenNameByIndex(uint256 index) public view returns (string memory) {
        return _tokenName[index];
    }

    /**
     * @dev Returns if the name has been reserved.
     */
    function isNameReserved(string memory nameString) public view returns (bool) {
        return _nameReserved[toLower(nameString)];
    }

    /**
    * @dev Mints Masks
    */
    function mint(address owner, uint256 numberOfMasks) public onlyOwner {
        require(totalSupply() < MAX_SUPPLY, "MaskForMusk: sale has already ended");
        require(totalSupply().add(numberOfMasks) <= MAX_SUPPLY, "MaskForMusk: Exceeds MAX_SUPPLY");

        for (uint256 i = 0; i < numberOfMasks; i++) {
            uint256 mintIndex = totalSupply();
            _safeMint(owner, mintIndex);
            ICosmoTokenMint(_cosmoToken).mintToFund(1e24);
        }
    }

    function isApprovedForAll(address owner, address operator) public view override returns (bool) {
        // Whitelist OpenSea proxy contract for easy trading.
        ProxyRegistry proxyRegistry = ProxyRegistry(proxyRegistryAddress);
        if (address(proxyRegistry.proxies(owner)) == operator) {
            return true;
        }
        return super.isApprovedForAll(owner, operator);
    }

    /**
     * @dev Changes the name for CosmoMask tokenId
     */
    function changeName(uint256 tokenId, string memory newName) public {
        address owner = ownerOf(tokenId);
        require(_msgSender() == owner, "MaskForMusk: caller is not the token owner");
        require(validateName(newName) == true, "MaskForMusk: not a valid new name");
        require(sha256(bytes(newName)) != sha256(bytes(_tokenName[tokenId])), "MaskForMusk: new name is same as the current one");
        require(isNameReserved(newName) == false, "MaskForMusk: name already reserved");

        IERC20BurnTransfer(_cmpAddress).transferFrom(msg.sender, address(this), NAME_CHANGE_PRICE);

        // If already named, dereserve old name
        if (bytes(_tokenName[tokenId]).length > 0) {
            toggleReserveName(_tokenName[tokenId], false);
        }
        toggleReserveName(newName, true);
        _tokenName[tokenId] = newName;
        IERC20BurnTransfer(_cmpAddress).burn(NAME_CHANGE_PRICE);
        emit NameChange(tokenId, newName);
    }

    /**
     * @dev Reserves the name if isReserve is set to true, de-reserves if set to false
     */
    function toggleReserveName(string memory str, bool isReserve) internal {
        _nameReserved[toLower(str)] = isReserve;
    }

    /**
     * @dev Check if the name string is valid (Alphanumeric and spaces without leading or trailing space)
     */
    function validateName(string memory str) public pure returns (bool) {
        bytes memory b = bytes(str);
        if (b.length < 1)
            return false;
        // Cannot be longer than 25 characters
        if (b.length > 25)
            return false;
        // Leading space
        if (b[0] == 0x20)
            return false;
        // Trailing space
        if (b[b.length - 1] == 0x20)
            return false;

        bytes1 lastChar = b[0];

        for (uint256 i; i < b.length; i++) {
            bytes1 char = b[i];
            // Cannot contain continous spaces
            if (char == 0x20 && lastChar == 0x20)
                return false;
            if (
                !(char >= 0x30 && char <= 0x39) && //9-0
                !(char >= 0x41 && char <= 0x5A) && //A-Z
                !(char >= 0x61 && char <= 0x7A) && //a-z
                !(char == 0x20) //space
            )
                return false;
            lastChar = char;
        }
        return true;
    }

    /**
     * @dev Converts the string to lowercase
     */
    function toLower(string memory str) public pure returns (string memory) {
        bytes memory bStr = bytes(str);
        bytes memory bLower = new bytes(bStr.length);
        for (uint256 i = 0; i < bStr.length; i++) {
            // Uppercase character
            if ((uint8(bStr[i]) >= 65) && (uint8(bStr[i]) <= 90))
                bLower[i] = bytes1(uint8(bStr[i]) + 32);
            else
                bLower[i] = bStr[i];
        }
        return string(bLower);
    }

    function setCosmoToken(address token) public onlyOwner {
        require(_cosmoToken == address(0), "MaskForMusk: CosmosToken has already setted");
        require(token != address(0), "MaskForMusk: CosmoToken is the zero address");
        _cosmoToken = token;
    }

    function setBaseURI(string memory baseURI_) public onlyOwner {
        _setBaseURI(baseURI_);
    }

    function setContractURI(string memory contractURI_) public onlyOwner {
        _contractURI = contractURI_;
    }

    function setURL(string memory newUrl) public onlyOwner {
        _setURL(newUrl);
    }
}

// File: /Users/ivannikov/work/snake-jungle/cosmomasks-for-musk/contracts/libraries/Address.sol



// SPDX-License-Identifier: MIT
pragma solidity >=0.6.2 <0.8.0;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    function isContract(address account) internal view returns (bool) {
        uint256 size;
        assembly {
            size := extcodesize(account)
        }
        return size > 0;
    }

    function functionCall(address target, bytes memory data, string memory errorMessage ) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }

    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");
        (bool success, bytes memory returndata) = target.call{value: value}(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 {
            if (returndata.length > 0) {
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

// File: /Users/ivannikov/work/snake-jungle/cosmomasks-for-musk/contracts/libraries/EnumerableMap.sol



// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Library for managing an enumerable variant of Solidity's
 * https://solidity.readthedocs.io/en/latest/types.html#mapping-types[`mapping`]
 * type.
 */
library EnumerableMap {
    struct MapEntry {
        bytes32 _key;
        bytes32 _value;
    }

    struct Map {
        MapEntry[] _entries;
        mapping(bytes32 => uint256) _indexes;
    }

    function _set(Map storage map, bytes32 key, bytes32 value) private returns (bool) {
        uint256 keyIndex = map._indexes[key];
        if (keyIndex == 0) {
            map._entries.push(MapEntry({_key: key, _value: value}));
            map._indexes[key] = map._entries.length;
            return true;
        } else {
            map._entries[keyIndex - 1]._value = value;
            return false;
        }
    }

    function _remove(Map storage map, bytes32 key) private returns (bool) {
        uint256 keyIndex = map._indexes[key];
        if (keyIndex != 0) {
            uint256 toDeleteIndex = keyIndex - 1;
            uint256 lastIndex = map._entries.length - 1;
            MapEntry storage lastEntry = map._entries[lastIndex];
            map._entries[toDeleteIndex] = lastEntry;
            map._indexes[lastEntry._key] = toDeleteIndex + 1;
            map._entries.pop();
            delete map._indexes[key];
            return true;
        } else {
            return false;
        }
    }

    function _contains(Map storage map, bytes32 key) private view returns (bool) {
        return map._indexes[key] != 0;
    }

    function _length(Map storage map) private view returns (uint256) {
        return map._entries.length;
    }

    function _at(Map storage map, uint256 index) private view returns (bytes32, bytes32) {
        require(map._entries.length > index, "EnumerableMap: index out of bounds");
        MapEntry storage entry = map._entries[index];
        return (entry._key, entry._value);
    }

    function _tryGet(Map storage map, bytes32 key) private view returns (bool, bytes32) {
        uint256 keyIndex = map._indexes[key];
        if (keyIndex == 0) return (false, 0);
        return (true, map._entries[keyIndex - 1]._value);
    }

    function _get(Map storage map, bytes32 key) private view returns (bytes32) {
        uint256 keyIndex = map._indexes[key];
        require(keyIndex != 0, "EnumerableMap: nonexistent key");
        return map._entries[keyIndex - 1]._value;
    }

    function _get(Map storage map, bytes32 key, string memory errorMessage) private view returns (bytes32) {
        uint256 keyIndex = map._indexes[key];
        require(keyIndex != 0, errorMessage);
        return map._entries[keyIndex - 1]._value;
    }

    // UintToAddressMap
    struct UintToAddressMap {
        Map _inner;
    }

    function set(UintToAddressMap storage map, uint256 key, address value) internal returns (bool) {
        return _set(map._inner, bytes32(key), bytes32(uint256(uint160(value))));
    }

    function remove(UintToAddressMap storage map, uint256 key) internal returns (bool) {
        return _remove(map._inner, bytes32(key));
    }

    function contains(UintToAddressMap storage map, uint256 key) internal view returns (bool) {
        return _contains(map._inner, bytes32(key));
    }

    function length(UintToAddressMap storage map) internal view returns (uint256) {
        return _length(map._inner);
    }

    function at(UintToAddressMap storage map, uint256 index) internal view returns (uint256, address) {
        (bytes32 key, bytes32 value) = _at(map._inner, index);
        return (uint256(key), address(uint160(uint256(value))));
    }

    function tryGet(UintToAddressMap storage map, uint256 key) internal view returns (bool, address) {
        (bool success, bytes32 value) = _tryGet(map._inner, bytes32(key));
        return (success, address(uint160(uint256(value))));
    }

    function get(UintToAddressMap storage map, uint256 key) internal view returns (address) {
        return address(uint160(uint256(_get(map._inner, bytes32(key)))));
    }

    function get(UintToAddressMap storage map, uint256 key, string memory errorMessage) internal view returns (address) {
        return address(uint160(uint256(_get(map._inner, bytes32(key), errorMessage))));
    }
}

// File: /Users/ivannikov/work/snake-jungle/cosmomasks-for-musk/contracts/libraries/EnumerableSet.sol



// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Library for managing
 * https://en.wikipedia.org/wiki/Set_(abstract_data_type)[sets] of primitive
 * types.
 */
library EnumerableSet {
    struct Set {
        bytes32[] _values;
        mapping(bytes32 => uint256) _indexes;
    }

    function _add(Set storage set, bytes32 value) private returns (bool) {
        if (!_contains(set, value)) {
            set._values.push(value);
            set._indexes[value] = set._values.length;
            return true;
        } else {
            return false;
        }
    }

    function _remove(Set storage set, bytes32 value) private returns (bool) {
        uint256 valueIndex = set._indexes[value];
        if (valueIndex != 0) {
            uint256 toDeleteIndex = valueIndex - 1;
            uint256 lastIndex = set._values.length - 1;
            bytes32 lastvalue = set._values[lastIndex];
            set._values[toDeleteIndex] = lastvalue;
            set._indexes[lastvalue] = toDeleteIndex + 1;
            set._values.pop();
            delete set._indexes[value];
            return true;
        } else {
            return false;
        }
    }

    function _contains(Set storage set, bytes32 value) private view returns (bool) {
        return set._indexes[value] != 0;
    }

    function _length(Set storage set) private view returns (uint256) {
        return set._values.length;
    }

    function _at(Set storage set, uint256 index) private view returns (bytes32) {
        require(set._values.length > index, "EnumerableSet: index out of bounds");
        return set._values[index];
    }

    // UintSet
    struct UintSet {
        Set _inner;
    }

    function add(UintSet storage set, uint256 value) internal returns (bool) {
        return _add(set._inner, bytes32(value));
    }

    function remove(UintSet storage set, uint256 value) internal returns (bool) {
        return _remove(set._inner, bytes32(value));
    }

    function contains(UintSet storage set, uint256 value) internal view returns (bool) {
        return _contains(set._inner, bytes32(value));
    }

    function length(UintSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }

    function at(UintSet storage set, uint256 index) internal view returns (uint256) {
        return uint256(_at(set._inner, index));
    }
}

// File: /Users/ivannikov/work/snake-jungle/cosmomasks-for-musk/contracts/libraries/SafeMath.sol



// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 */
library SafeMath {
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");
        return c;
    }

    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a, "SafeMath: subtraction overflow");
        return a - b;
    }

    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;
    }

    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: division by zero");
        return a / b;
    }

    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        return a - b;
    }
}

// File: /Users/ivannikov/work/snake-jungle/cosmomasks-for-musk/contracts/libraries/Strings.sol



// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev String operations.
 */
library Strings {
    function toString(uint256 value) internal pure returns (string memory) {
        if (value == 0) {
            return "0";
        }
        uint256 temp = value;
        uint256 digits;
        while (temp != 0) {
            digits++;
            temp /= 10;
        }
        bytes memory buffer = new bytes(digits);
        uint256 index = digits - 1;
        temp = value;
        while (temp != 0) {
            buffer[index--] = bytes1(uint8(48 + (temp % 10)));
            temp /= 10;
        }
        return string(buffer);
    }
}

// File: /Users/ivannikov/work/snake-jungle/cosmomasks-for-musk/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.
 */
abstract contract Context {
    function _msgSender() internal view returns (address payable) {
        return msg.sender;
    }
}

// File: /Users/ivannikov/work/snake-jungle/cosmomasks-for-musk/contracts/utils/Ownable.sol



// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;

import "./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.
 */
abstract contract Ownable is Context {
    address private _owner;
    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    constructor() internal {
        address msgSender = _msgSender();
        _owner = msgSender;
        emit OwnershipTransferred(address(0), msgSender);
    }

    function owner() public view virtual returns (address) {
        return _owner;
    }

    modifier onlyOwner() {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
        _;
    }

    function renounceOwnership() public virtual onlyOwner {
        emit OwnershipTransferred(_owner, address(0));
        _owner = address(0);
    }

    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}