// File: 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 {
    /**
     * @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: 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: DegensFarm.sol



// SPDX-License-Identifier: MIT
// Degen'$ Farm: Collectible NFT game (https://degens.farm)
pragma solidity ^0.7.4;
pragma experimental ABIEncoderV2;

import "./DegensFarmBase.sol";

contract DegenFarm is DegenFarmBase {

    uint8   constant public CREATURE_TYPE_COUNT= 20;  // how much creatures types may be used
    uint256 constant public FARMING_DURATION   = 168 hours;
    uint256 constant public TOOL_UNSTAKE_DELAY = 1 weeks;
    uint16  constant public NORMIE_COUNT_IN_TYPE = 100;
    uint16  constant public CHAD_COUNT_IN_TYPE = 20;
    uint16  constant public MAX_LANDS = 2500;

    constructor (
        address _land,
        address _creatures,
        address _inventory,
        address _bagstoken,
        address _dungtoken,
        IEggs _eggs
    )
        DegenFarmBase(_land, _creatures, _inventory, _bagstoken, _dungtoken, _eggs)
    {
        require(CREATURE_TYPE_COUNT <= CREATURE_TYPE_COUNT_MAX, "CREATURE_TYPE_COUNT is greater than CREATURE_TYPE_COUNT_MAX");

        // Mainnet amulet addresses
        amulets[0]  = 0xD533a949740bb3306d119CC777fa900bA034cd52; // Cow    $CRV
        amulets[1]  = 0x1f9840a85d5aF5bf1D1762F925BDADdC4201F984; // Horse  $UNI
        amulets[2]  = 0xfA5047c9c78B8877af97BDcb85Db743fD7313d4a; // Rabbit $ROOK
        amulets[3]  = 0xDADA00A9C23390112D08a1377cc59f7d03D9df55; // Chicken $DUNG
        amulets[4]  = 0x6B3595068778DD592e39A122f4f5a5cF09C90fE2; // Pig    $SUSHI
        amulets[5]  = 0x0D8775F648430679A709E98d2b0Cb6250d2887EF; // Cat    $BAT
        amulets[6]  = 0x3472A5A71965499acd81997a54BBA8D852C6E53d; // Dog	$BADGER
        amulets[7]  = 0x0d438F3b5175Bebc262bF23753C1E53d03432bDE; // Goose	$WNXM
        amulets[8]  = 0x3155BA85D5F96b2d030a4966AF206230e46849cb; // Goat	$RUNE
        amulets[9]  = 0x7Fc66500c84A76Ad7e9c93437bFc5Ac33E2DDaE9; // Sheep	$AAVE
        amulets[10] = 0xC011a73ee8576Fb46F5E1c5751cA3B9Fe0af2a6F; // Snake	$SNX
        amulets[11] = 0x967da4048cD07aB37855c090aAF366e4ce1b9F48; // Fish	$OCEAN
        amulets[12] = 0x0F5D2fB29fb7d3CFeE444a200298f468908cC942; // Frog	$MANA
        amulets[13] = 0x514910771AF9Ca656af840dff83E8264EcF986CA; // Worm	$LINK
        amulets[14] = 0x5A98FcBEA516Cf06857215779Fd812CA3beF1B32; // Lama	$LDO
        amulets[15] = 0x1F573D6Fb3F13d689FF844B4cE37794d79a7FF1C; // Mouse	$BNT
        amulets[16] = 0x9f8F72aA9304c8B593d555F12eF6589cC3A579A2; // Camel	$MKR
        amulets[17] = 0x111111111117dC0aa78b770fA6A738034120C302; // Donkey	$1INCH
        amulets[18] = 0x0bc529c00C6401aEF6D220BE8C6Ea1667F6Ad93e; // Bee	$YFI
        amulets[19] = 0xc00e94Cb662C3520282E6f5717214004A7f26888; // Duck	$COMP
    }

    function getCreatureTypeCount() override internal view returns (uint16) {
        return CREATURE_TYPE_COUNT;
    }

    function getFarmingDuration() override internal view returns (uint) {
        return FARMING_DURATION;
    }

    function getNormieCountInType() override internal view returns (uint16) {
        return NORMIE_COUNT_IN_TYPE;
    }

    function getChadCountInType() override internal view returns (uint16) {
        return CHAD_COUNT_IN_TYPE;
    }

    function getMaxLands() override internal view returns (uint16) {
        return MAX_LANDS;
    }

    function getToolUnstakeDelay() override internal view returns (uint) {
        return TOOL_UNSTAKE_DELAY;
    }

}

// File: DegensFarmBase.sol



// SPDX-License-Identifier: MIT
// Degen'$ Farm: Collectible NFT game (https://degens.farm)
pragma solidity ^0.7.4;
pragma experimental ABIEncoderV2;

import "./IERC20.sol";
import "./IERC1155.sol";
import "./ERC1155Receiver.sol";
import "./IERC721.sol";
import "./Ownable.sol";

interface IEggs is IERC721 {
    function mint(address to, uint256 tokenId) external;
    function burn(uint256 tokenId) external;
    function getUsersTokens(address _owner) external view returns (uint256[] memory);
}

interface ICreatures is IERC721 {
    function mint(
        address to, 
        uint256 tokenId, 
        uint8 _animalType,
        uint8 _rarity,
        uint32 index
        ) external;

    function getTypeAndRarity(uint256 _tokenId) external view returns(uint8, uint8);
    function tokenOfOwnerByIndex(address owner, uint256 index) external view returns (uint256);
}

interface ILand is IERC721 {
    function mint(
        address to, 
        uint256 tokenId,
        uint randomSeed
    ) external;
    function burn(uint256 tokenId) external;
}

interface IDung is IERC20 {
    function mint(
        address to, 
        uint256 amount 
    ) external;
}

interface IInventory is IERC1155 {
     function getToolBoost(uint8 _item) external view returns (uint16);
}

interface IAmuletPriceProvider {
     function getLastPrice(address _amulet) external view returns (uint256);
}

interface IOperatorManage {
    function addOperator(address _newOperator) external;    
    function removeOperator(address _oldOperator) external;
    function withdrawERC20(IERC20 _tokenContract, address _admin) external;
    function setSigner(address _newSigner) external;
}

abstract contract DegenFarmBase is ERC1155Receiver, Ownable {
    enum AnimalType {
        Cow, Horse, Rabbit, Chicken, Pig, Cat, Dog, Goose, Goat, Sheep,
        Snake, Fish, Frog, Worm, Lama, Mouse, Camel, Donkey, Bee, Duck,
        GenesisEgg // 20
    }
    enum Rarity {
        Normie, // 0
        Chad,   // 1
        Degen,  // 2
        Unique // 3
    }
    enum   Result     {Fail,   Dung,  Chad, Degen}
    
    // External contract addresses used with this farm
    struct AddressRegistry {
        address land;
        address creatures;
        address inventory;
        address bagstoken;
        address dungtoken;
    }

    // Degens Farm data for creature type
    struct CreaturesCount {
        uint16 totalNormie;
        uint16 leftNormie;
        uint16 totalChad;
        uint16 leftChadToDiscover;
        uint16 totalDegen;
        uint16 leftDegenToDiscover;
        uint16 chadFarmAttempts;
        uint16 degenFarmAttempts;
    }

    // Land count record
    struct LandCount {
        uint16 total;
        uint16 left;
    }
 
    // Record represent one farming act
    struct FarmRecord {
        uint256   creatureId;
        uint256   landId;
        uint256   harvestTime;
        uint256   amuletsPrice1;
        uint256   amuletsPrice2;
        Result    harvest;
        uint256   harvestId; // new NFT tokenId
        bool[COMMON_AMULET_COUNT]   commonAmuletInitialHold;
    }

    // Bonus for better harvest
    struct Bonus {
        uint256 commonAmuletHold;  // common amulet hold
        uint256 creatureAmuletBullTrend;
        uint256 inventoryHold;
        uint256 creatureAmuletBalance;
    }

    uint8   constant public CREATURE_TYPE_COUNT_MAX = 20;  //how much creatures types may be used

    // Creature probability multiplier, scaled with 100. 3.00  - 300, 3.05 - 305 etc
    uint32  constant public CREATURE_P_MULT = 230;
    uint16  public MAX_ALL_NORMIES    = getCreatureTypeCount() * getNormieCountInType();
    uint256 constant public NFT_ID_MULTIPLIER  = 10000;     //must be set more then all Normies count
    uint256 constant public FARM_DUNG_AMOUNT   = 250e33;      //per one harvest
    uint256 constant public BONUS_POINTS_AMULET_HOLD       = 10;
    uint256 constant public COMMON_AMULET_COUNT       = 2;
    uint256 constant public TOOL_TYPE_COUNT = 6;

    // Common Amulet addresses
    address[COMMON_AMULET_COUNT] public COMMON_AMULETS = [
        0x126c121f99e1E211dF2e5f8De2d96Fa36647c855, // $DEGEN token
        0xa0246c9032bC3A600820415aE600c6388619A14D  // $FARM token
    ];

    bool    public REVEAL_ENABLED  = false;
    bool    public FARMING_ENABLED = false;
    address public priceProvider;
    IEggs   public eggs;
    
    address[CREATURE_TYPE_COUNT_MAX] public amulets; // amulets by creature type
    AddressRegistry                  public farm;
    LandCount                        public landCount;

    mapping(address => uint256) public maxAmuletBalances;

    // mapping from user to his(her) staked tools
    // Index of uint256[6] represent tool NFT itemID
    mapping(address => uint256[TOOL_TYPE_COUNT]) public userStakedTools;


    uint16 public allNormiesesLeft;
    CreaturesCount[CREATURE_TYPE_COUNT_MAX] public creaturesBorn;
    FarmRecord[] public farming;
    mapping(uint => uint) public parents;

    event Reveal(address _farmer, uint256 indexed _tokenId, bool _isCreature, uint8 _animalType);
    event Harvest(
        uint256 indexed _eggId, 
        address farmer, 
        uint8   result,
        uint256 baseChance,
        uint256 commonAmuletHold,
        uint256 amuletBullTrend,
        uint256 inventoryHold,
        uint256 amuletMaxBalance,
        uint256 resultChance
    );
    event Stake(address owner, uint8 innventory);
    event UnStake(address owner, uint8 innventory);
    
    constructor (
        address _land, 
        address _creatures,
        address _inventory,
        address _bagstoken,
        address _dungtoken,
        IEggs _eggs
    )
    {
        farm.land      = _land;
        farm.creatures = _creatures;
        farm.inventory = _inventory;
        farm.bagstoken = _bagstoken;
        farm.dungtoken = _dungtoken;
        
        // Index of creaturesBorn in this initial setting  
        // must NOT exceed CREATURE_TYPE_COUNT
        for (uint i = 0; i < getCreatureTypeCount(); i++) {
            creaturesBorn[i] = CreaturesCount(
                getNormieCountInType(), // totalNormie;
                getNormieCountInType(), // leftNormie;
                getChadCountInType(),   // totalChad;
                getChadCountInType(),   // leftChadToDiscover;
                1,                      // totalDegen;
                1,                      // leftDegenToDiscover;
                0, // chadFarmAttempts;
                0);  // degenFarmAttempts;
        }

        landCount        = LandCount(getMaxLands(), getMaxLands());
        allNormiesesLeft = MAX_ALL_NORMIES;
        eggs = _eggs;
    }

    function reveal(uint count) external {
        require(_isRevelEnabled(), "Please wait for reveal enabled.");
        require(count > 0, "Count must be positive");
        require(count <= 8, "Count must less than 9"); // random limit
        require(
            IERC20(farm.bagstoken).allowance(msg.sender, address(this)) >= count*1,
            "Please approve your BAGS token to this contract."
        );
        require(
            IERC20(farm.bagstoken).transferFrom(msg.sender, address(this), count*1)
        );
        uint randomSeed = uint(keccak256(abi.encodePacked(block.timestamp, msg.sender)));
        // random seed for 8 reveals (8x32=256)
        for (uint i = 0; i < count; i++) {
            _reveal(randomSeed);
            randomSeed = randomSeed / 0x100000000; // shift right 32 bits
        }
    }

    /**
     * @dev Start farming process. New NFT - Egg will minted for user 
     * @param _creatureId - NFT tokenId, caller must be owner of this token
     * @param _landId -- NFT tokenId, caller must be owner of this token
     */
    function farmDeploy(uint256 _creatureId, uint256 _landId) external {
        require(FARMING_ENABLED == true, "Chief Farmer not enable yet");
        require(ICreatures(farm.creatures).ownerOf(_creatureId) == msg.sender, 
            "Need to be Creature Owner"
        );
        require(ILand(farm.land).ownerOf(_landId) == msg.sender,
            "Need to be Land Owner"
        );
        (uint8 crType, uint8 crRarity) = ICreatures(farm.creatures).getTypeAndRarity(_creatureId);
        require((DegenFarmBase.Rarity)(crRarity) == Rarity.Normie ||
            (DegenFarmBase.Rarity)(crRarity) == Rarity.Chad,
            "Can farm only Normie and Chad");
        // Check that farming available yet
        if (crRarity == 0) {
            require(creaturesBorn[crType].leftChadToDiscover > 0, "No more chads left");
        } else {
            require(creaturesBorn[crType].leftDegenToDiscover > 0, "No more Degen left");
        }

        // Save deploy record
        farming.push(
            FarmRecord({
                creatureId:    _creatureId,
                landId:        _landId,
                harvestTime:   block.timestamp + getFarmingDuration(),
                amuletsPrice1: _getExistingAmuletsPrices(amulets[crType]),
                amuletsPrice2: 0,
                harvest:       Result.Fail,
                harvestId:     0, 
                commonAmuletInitialHold: _getCommonAmuletsHoldState(msg.sender) //save initial hold state
            })
        );

        // Let's mint Egg.
        eggs.mint(
            msg.sender,         // farmer
            farming.length - 1  // tokenId
        );
        // STAKE LAND and Creatures
        ILand(farm.land).transferFrom(msg.sender, address(this), _landId);
        ICreatures(farm.creatures).transferFrom(msg.sender, address(this), _creatureId);
    }

    /**
     * @dev Finish farming process. Egg NFT will be  burn 
     * @param _deployId - NFT tokenId, caller must be owner of this token
     */
    function harvest(uint256 _deployId) external {

        require(eggs.ownerOf(_deployId) == msg.sender, "This is NOT YOUR EGG");
        
        FarmRecord storage f = farming[_deployId];
        require(f.harvestTime <= block.timestamp, "To early for harvest");
        // Lets Calculate Dung/CHAD-DEGEN chance
        Result farmingResult;
        Bonus memory bonus;
        // 1. BaseChance
        (uint8 crType, uint8 crRarity) = ICreatures(farm.creatures).getTypeAndRarity(
            f.creatureId
        );
        uint256 baseChance;
        if (crRarity == 0) {
            // Try farm CHAD. So if there is no CHADs any more we must return assets
            if (creaturesBorn[crType].leftChadToDiscover == 0) {
                _endFarming(_deployId, Result.Fail);
                return;
            }
            baseChance = 100 * creaturesBorn[crType].totalChad / creaturesBorn[crType].totalNormie; // by default 20%
            // Decrease appropriate farm ATTEMPTS COUNT
            creaturesBorn[crType].chadFarmAttempts += 1;
        } else {
            // Try farm DEGEN. So if there is no DEGENSs any more we must return assets
            if (creaturesBorn[crType].leftDegenToDiscover == 0) {
                _endFarming(_deployId, Result.Fail);
                return;
            }
            baseChance = 100 * creaturesBorn[crType].totalDegen / creaturesBorn[crType].totalChad; // by default 5%
            // Decrease appropriate farm ATTEMPTS COUNT
            creaturesBorn[crType].degenFarmAttempts += 1;
        }
        //////////////////////////////////////////////
        //   2. Bonus for common amulet token ***HOLD*** - commonAmuletHold
        //////////////////////////////////////////////
  
        // Get current hold stae
        for (uint8 i = 0; i < COMMON_AMULETS.length; i ++){
            if (f.commonAmuletInitialHold[i] &&  _getCommonAmuletsHoldState(msg.sender)[i]) {
                bonus.commonAmuletHold = BONUS_POINTS_AMULET_HOLD;
            }
        }
        //////////////////////////////////////////////
        //   3. Bonus for creatures amulets BULLs trend  - creatureAmuletBullTrend
        //   4. Bonus for creatures amulets balance      - creatureAmuletBalance
        //////////////////////////////////////////////
        uint256 prices2 = 0;
        prices2 = _getExistingAmuletsPrices(amulets[crType]);
        if (f.amuletsPrice1 > 0 && prices2 > 0 && prices2 > f.amuletsPrice1){
            bonus.creatureAmuletBullTrend =
                (prices2 - f.amuletsPrice1) * 100 / f.amuletsPrice1;
        }
        //Lets check max Balance, because
        //bonus.amuletHold = userAmuletBalance/maxAmuletBalances*BONUS_POINTS_AMULET_HOLD
        _checkAndSaveMaxAmuletPrice(amulets[crType]);
        if (maxAmuletBalances[amulets[crType]] > 0) {
            bonus.creatureAmuletBalance =
                IERC20(amulets[crType]).balanceOf(msg.sender) * 100 //100 used for scale
                / maxAmuletBalances[amulets[crType]] * BONUS_POINTS_AMULET_HOLD /100;
        }
        f.amuletsPrice2 = prices2;    

        ////////////////////////////////////////////// 
        //5. Bonus for inventory 
        //////////////////////////////////////////////
        bonus.inventoryHold = 0;
        if (userStakedTools[msg.sender].length > 0) { 
           for (uint8 i=0; i < userStakedTools[msg.sender].length; i++) {
               if (userStakedTools[msg.sender][i] > 0) {
                   bonus.inventoryHold = bonus.inventoryHold + IInventory(farm.inventory).getToolBoost(i);
               }
           }
        }  
        //////////////////////////////////////////////

        uint256 allBonus = bonus.commonAmuletHold 
            + bonus.creatureAmuletBullTrend 
            + bonus.creatureAmuletBalance
            + bonus.inventoryHold;

        if (allBonus > 100) {
            allBonus = 100; // limit bonus to 100%
        }

        uint32[] memory choiceWeight = new uint32[](2);
        choiceWeight[0] = uint32(baseChance * (100 + allBonus)); // chance of born new chad/degen
        choiceWeight[1] = uint32(10000 - choiceWeight[0]); // receive DUNG

        if (_getWeightedChoice(choiceWeight) == 0) {
            f.harvestId = (crRarity + 1) * NFT_ID_MULTIPLIER + _deployId;
            // Mint new chad/degen

            uint32 index;
            // Decrease appropriate CREATURE COUNT
            if (crRarity + 1 == uint8(Rarity.Chad)) {
                index = creaturesBorn[crType].totalChad - creaturesBorn[crType].leftChadToDiscover + 1;
                creaturesBorn[crType].leftChadToDiscover -= 1;
                farmingResult = Result.Chad;
            } else if (crRarity + 1 == uint8(Rarity.Degen)) {
                index = creaturesBorn[crType].totalDegen - creaturesBorn[crType].leftDegenToDiscover + 1;
                creaturesBorn[crType].leftDegenToDiscover -= 1;
                farmingResult = Result.Degen;
            }

            uint newCreatureId = (crRarity + 1) * NFT_ID_MULTIPLIER + _deployId;
            ICreatures(farm.creatures).mint(
                msg.sender,
                newCreatureId, // new iD
                crType, // AnimalType
                crRarity + 1,
                index // index
            );
            parents[newCreatureId] = f.creatureId;
        } else {
            // Mint new dung
            IDung(farm.dungtoken).mint(msg.sender, FARM_DUNG_AMOUNT);
            farmingResult = Result.Dung;
        }
        
        // BURN Land
        ILand(farm.land).burn(f.landId);
        _endFarming(_deployId, farmingResult);
        emit Harvest(
            _deployId, 
            msg.sender, 
            uint8(farmingResult),
            baseChance,
            bonus.commonAmuletHold,
            bonus.creatureAmuletBullTrend,
            bonus.inventoryHold,
            bonus.creatureAmuletBalance,
            choiceWeight[0]
        );
    }

    /**
     * @dev Stake one inventory item 
     * @param _itemId - NFT tokenId, caller must be owner of this token
     */
    function stakeOneTool(uint8 _itemId) external {
        _stakeOneTool(_itemId);
         emit Stake(msg.sender, _itemId);
    }

    /**
     * @dev UnStake one inventory item 
     * @param _itemId - NFT tokenId
     */
    function unstakeOneTool(uint8 _itemId) external {
        _unstakeOneTool(_itemId);
        emit UnStake(msg.sender, _itemId);
    }

    /////////////////////////////////////////////////////
    ////    Admin functions                       ///////
    /////////////////////////////////////////////////////
    function setOneCommonAmulet(uint8 _index, address _token) external onlyOwner {
        COMMON_AMULETS[_index] = _token;
    }

    function setAmuletForOneCreature(uint8 _index, address _token) external onlyOwner {
        amulets[_index] = _token;
    }

    function setAmulets(address[] calldata _tokens) external onlyOwner {
        for (uint i = 0; i < _tokens.length; i++) {
            amulets[i] = _tokens[i];
        }
    }

    function setPriceProvider(address _priceProvider) external onlyOwner {
        priceProvider = _priceProvider;
    }

    function enableReveal(bool _isEnabled) external onlyOwner {
        REVEAL_ENABLED = _isEnabled;
    }

    function enableFarming(bool _isEnabled) external onlyOwner {
        FARMING_ENABLED = _isEnabled;
    }

    ////////////////////////////////////////
    /// Proxy for NFT Operators mamnage   //
    ////////////////////////////////////////
    function addOperator(address _contract, address newOperator) external onlyOwner {
        IOperatorManage(_contract).addOperator(newOperator);
    }

    function removeOperator(address _contract, address oldOperator) external onlyOwner {
        IOperatorManage(_contract).removeOperator(oldOperator);
    }
 
    function reclaimToken(address _contract, IERC20 anyTokens, address _admin) external onlyOwner {
        IOperatorManage(_contract).withdrawERC20(anyTokens, _admin);
    }

    function setSigner(address _contract, address _newSigner) external onlyOwner {
        IOperatorManage(_contract).setSigner(_newSigner);
    }

    ////////////////////////////////////////////////////////

    function getCreatureAmulets(uint8 _creatureType) external view returns (address) {
        return _getCreatureAmulets(_creatureType);
    }

    function _getCreatureAmulets(uint8 _creatureType) internal view returns (address) {
        return amulets[_creatureType];
    } 

    function getCreatureStat(uint8 _creatureType) 
        external 
        view 
        returns (
            uint16, 
            uint16, 
            uint16, 
            uint16, 
            uint16, 
            uint16,
            uint16,
            uint16 
        )
    {
        CreaturesCount storage stat = creaturesBorn[_creatureType];
        return (
            stat.totalNormie, 
            stat.leftNormie, 
            stat.totalChad, 
            stat.leftChadToDiscover, 
            stat.totalDegen, 
            stat.leftDegenToDiscover,
            stat.chadFarmAttempts,
            stat.degenFarmAttempts
        );
    }

    function getWeightedChoice(uint32[] memory _weights) external view returns (uint8){
        return _getWeightedChoice(_weights);
    }

    function _getWeightedChoice(uint32[] memory _weights) internal view returns (uint8){
        uint randomSeed = uint(keccak256(abi.encodePacked(block.timestamp, msg.sender)));
        return _getWeightedChoice2(_weights, randomSeed);
    }

    function getFarmingById(uint256 _farmingId) external view returns (FarmRecord memory) {
        return farming[_farmingId];
    }

    function getOneAmuletPrice(address _token) external view returns (uint256) {
        return _getOneAmuletPrice(_token);
    }

    
    ///////////////////////////////////////////////
    ///  Internals                          ///////                   
    ///////////////////////////////////////////////
    /**
     * @dev Save farming results in storage and mint
     * appropriate token (NFT, ERC20 or None)
    */
    function _endFarming(uint256 _deployId, Result  _res) internal {
        FarmRecord storage f = farming[_deployId];
        f.harvest = _res;
        // unstake creature
        ICreatures(farm.creatures).transferFrom(address(this), msg.sender, f.creatureId);
        eggs.burn(_deployId); // Burn EGG

        if (_res ==  Result.Fail) {
            //unstake land (if staked)
            if (ILand(farm.land).ownerOf(f.landId) == address(this)){
               ILand(farm.land).transferFrom(address(this), msg.sender, f.landId);
            }
            emit Harvest(
                _deployId, 
                msg.sender, 
                uint8(_res),
                0, //baseChance
                0, //bonus.commonAmuletHold
                0, //bonus.creatureAmuletBullTrend,
                0, //bonus.inventoryHold 
                0,  // bonus.creatureAmuletBalance
                0
            );   
        }
    }

    function _stakeOneTool(uint8 _itemId) internal {
        require(IInventory(farm.inventory).balanceOf(msg.sender, _itemId) >= 1,
            "You must own this tool for stake!"
        );
        // Before stake  we need two checks.
        // 1. Removed
        // 2. Cant`t stake one tool more than one item
        require(userStakedTools[msg.sender][_itemId] == 0, "Tool is already staked");

        // stake
        IInventory(farm.inventory).safeTransferFrom(
            msg.sender, 
            address(this), 
            _itemId, 
            1, 
            bytes('0')
        );
        userStakedTools[msg.sender][_itemId] = block.timestamp;
    }

    function _unstakeOneTool(uint8 _itemId) internal {
        require(userStakedTools[msg.sender][_itemId] > 0, "This tool is not staked yet");
        require(block.timestamp - userStakedTools[msg.sender][_itemId] >= getToolUnstakeDelay(),
            "Cant unstake earlier than a week"
        );
        userStakedTools[msg.sender][_itemId] = 0;
        IInventory(farm.inventory).safeTransferFrom(
            address(this), 
            msg.sender, 
            _itemId, 
            1, 
            bytes('0')
        );

    }

    function _checkAndSaveMaxAmuletPrice(address _amulet) internal {
        if (IERC20(_amulet).balanceOf(msg.sender)
                > maxAmuletBalances[_amulet]
            ) 
            {
              maxAmuletBalances[_amulet] 
              = IERC20(_amulet).balanceOf(msg.sender);
            }
    }

    function _getCommonAmuletsHoldState(address _farmer) internal view returns (bool[COMMON_AMULET_COUNT] memory) {
        
        // If token balance =0 - set false
        bool[COMMON_AMULET_COUNT] memory res;
        for (uint8 i = 0; i < COMMON_AMULETS.length; i++){
            if (IERC20(COMMON_AMULETS[i]).balanceOf(_farmer) > 0){
                res[i] = true;    
            } else {
            // Set to zero if token balance is 0   
                res[i] = false;
            }
        }
        return res;
    }

    function _getExistingAmuletsPrices(address _token) 
        internal 
        view 
        returns (uint256) 
    {
        if (IERC20(_token).balanceOf(msg.sender) > 0){
            return _getOneAmuletPrice(_token);    
        } else {
        // Set to zero if token balance is 0   
            return 0;
        }    
    }

    function _getOneAmuletPrice(address _token) internal view returns (uint256) {
        return IAmuletPriceProvider(priceProvider).getLastPrice(_token);
    }

    function _isRevelEnabled() internal view returns (bool) {
        return REVEAL_ENABLED;
    }

    function _reveal(uint randomSeed) internal {
        require ((landCount.left + allNormiesesLeft) > 0, "Sorry, no more reveal!");
        //1. Lets choose Land OR Creature, %
        //So we have two possible results. 1 - Land, 0 - Creature.
        // sum of weights = 100, lets define weigth for Creature
        uint32[] memory choiceWeight = new uint32[](2);
        choiceWeight[0] = uint32(allNormiesesLeft) * CREATURE_P_MULT;
        choiceWeight[1] = uint32(landCount.left) * 100;
        uint8 choice = uint8(_getWeightedChoice2(choiceWeight, randomSeed));
        randomSeed /= 0x10000; // shift right 16 bits
        //Check that choice can be executed
        if (choice != 0 && landCount.left == 0) {
            //There are no more Lands. So we need change choice
            choice = 0;
        }

        if (choice == 0) { // create creature
            uint32[] memory choiceWeight0 = new uint32[](getCreatureTypeCount());
            //2. Ok, Creature will  be born. But what kind of?
            for (uint8 i = 0; i < getCreatureTypeCount(); i ++) {
                choiceWeight0[i] = uint32(creaturesBorn[i].leftNormie);
            }
            choice = uint8(_getWeightedChoice2(choiceWeight0, randomSeed));
            ICreatures(farm.creatures).mint(
                msg.sender, 
                MAX_ALL_NORMIES - allNormiesesLeft,
                choice, //AnimalType
                0,
                creaturesBorn[choice].totalNormie - creaturesBorn[choice].leftNormie + 1 // index
            );
            emit Reveal(msg.sender, MAX_ALL_NORMIES - allNormiesesLeft, true, choice);
            allNormiesesLeft -= 1;
            creaturesBorn[choice].leftNormie -= 1;
        } else { // create land
            ILand(farm.land).mint(
                msg.sender, 
                getMaxLands() - landCount.left,
                randomSeed
            );
            emit Reveal(msg.sender, getMaxLands() - landCount.left , false, 0);
            landCount.left -= 1; 
        }
    }

    function _getWeightedChoice2(uint32[] memory _weights, uint randomSeed) internal view returns (uint8){
        uint256 sum_of_weights = 0;
        for (uint8 index = 0; index < _weights.length; index++) {
            sum_of_weights += _weights[index];
        }
        uint256 rnd = randomSeed % sum_of_weights;
        for (uint8 kindex = 0; kindex < _weights.length; kindex++) {
            if (rnd < _weights[kindex]) {
                return kindex;
            }
            rnd -= _weights[kindex];
        }
        return 0;
    }

    /**
        @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
        override
        returns(bytes4)
    {
        return bytes4(keccak256("onERC1155Received(address,address,uint256,uint256,bytes)"));  
    }    

    /**
        @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
        override
        returns(bytes4)
    {
        return bytes4(keccak256("onERC1155BatchReceived(address,address,uint256,uint256,bytes)"));  
    }

    function getCreatureTypeCount() virtual internal view returns (uint16);

    function getFarmingDuration() virtual internal view returns (uint);

    function getToolUnstakeDelay() virtual internal view returns (uint);

    function getNormieCountInType() virtual internal view returns (uint16);

    function getChadCountInType() virtual internal view returns (uint16);

    function getMaxLands() virtual internal view returns (uint16);

    function getUsersTokens(address _owner) external view returns (uint256[] memory) {
        return eggs.getUsersTokens(_owner);
    }

    /**
     * @dev Returns creatures owned by owner and that can be used for farming.this
     * Some creatures types and rarity are limited to farm because all chad/degens
     * was already discovered.
     * @param _owner - creatures owner
     */
    function getFarmingAllowedCreatures(address _owner) external view returns (uint256[] memory) {
        uint256 n = ICreatures(farm.creatures).balanceOf(_owner);

        uint256[] memory result = new uint256[](n);
        uint256 count = 0;

        for (uint16 i = 0; i < n; i++) {
            uint creatureId = ICreatures(farm.creatures).tokenOfOwnerByIndex(_owner, i);
            if (isFarmingAllowedForCreature(creatureId)) {
                result[count] = creatureId;
                count++;
            }
        }
        uint256[] memory result2 = new uint256[](count);
        for (uint16 i = 0; i < count; i++) {
            result2[i] = result[i];
        }
        return result2;
    }

    function getFarmingAllowedCreaturesWithRarity(address _owner, uint8 wantRarity) external view returns (uint256[] memory) {
        uint256 n = ICreatures(farm.creatures).balanceOf(_owner);

        uint256[] memory result = new uint256[](n);
        uint256 count = 0;

        for (uint16 i = 0; i < n; i++) {
            uint creatureId = ICreatures(farm.creatures).tokenOfOwnerByIndex(_owner, i);
            (uint8 _, uint8 rarity) = ICreatures(farm.creatures).getTypeAndRarity(creatureId);
            if (rarity == wantRarity && isFarmingAllowedForCreature(creatureId)) {
                result[count] = creatureId;
                count++;
            }
        }
        uint256[] memory result2 = new uint256[](count);
        for (uint16 i = 0; i < count; i++) {
            result2[i] = result[i];
        }
        return result2;
    }

    function isFarmingAllowedForCreature(uint creatureId) public view returns (bool) {
        (uint8 _type, uint8 rarity) = ICreatures(farm.creatures).getTypeAndRarity(creatureId);

        if ((DegenFarmBase.Rarity)(rarity) == Rarity.Normie) {
            return creaturesBorn[_type].leftChadToDiscover > 0;
        }
        if ((DegenFarmBase.Rarity)(rarity) == Rarity.Chad) {
            return creaturesBorn[_type].leftDegenToDiscover > 0;
        }
        return false;
    }
}

// File: 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.
 *
 * Maps have the following properties:
 *
 * - Entries are added, removed, and checked for existence in constant time
 * (O(1)).
 * - Entries are enumerated in O(n). No guarantees are made on the ordering.
 *
 * ```
 * contract Example {
 *     // Add the library methods
 *     using EnumerableMap for EnumerableMap.UintToAddressMap;
 *
 *     // Declare a set state variable
 *     EnumerableMap.UintToAddressMap private myMap;
 * }
 * ```
 *
 * As of v3.0.0, only maps of type `uint256 -> address` (`UintToAddressMap`) are
 * supported.
 */
library EnumerableMap {
    // To implement this library for multiple types with as little code
    // repetition as possible, we write it in terms of a generic Map type with
    // bytes32 keys and values.
    // The Map implementation uses private functions, and user-facing
    // implementations (such as Uint256ToAddressMap) are just wrappers around
    // the underlying Map.
    // This means that we can only create new EnumerableMaps for types that fit
    // in bytes32.

    struct MapEntry {
        bytes32 _key;
        bytes32 _value;
    }

    struct Map {
        // Storage of map keys and values
        MapEntry[] _entries;

        // Position of the entry defined by a key in the `entries` array, plus 1
        // because index 0 means a key is not in the map.
        mapping (bytes32 => uint256) _indexes;
    }

    /**
     * @dev Adds a key-value pair to a map, or updates the value for an existing
     * key. O(1).
     *
     * Returns true if the key was added to the map, that is if it was not
     * already present.
     */
    function _set(Map storage map, bytes32 key, bytes32 value) private returns (bool) {
        // We read and store the key's index to prevent multiple reads from the same storage slot
        uint256 keyIndex = map._indexes[key];

        if (keyIndex == 0) { // Equivalent to !contains(map, key)
            map._entries.push(MapEntry({ _key: key, _value: value }));
            // The entry is stored at length-1, but we add 1 to all indexes
            // and use 0 as a sentinel value
            map._indexes[key] = map._entries.length;
            return true;
        } else {
            map._entries[keyIndex - 1]._value = value;
            return false;
        }
    }

    /**
     * @dev Removes a key-value pair from a map. O(1).
     *
     * Returns true if the key was removed from the map, that is if it was present.
     */
    function _remove(Map storage map, bytes32 key) private returns (bool) {
        // We read and store the key's index to prevent multiple reads from the same storage slot
        uint256 keyIndex = map._indexes[key];

        if (keyIndex != 0) { // Equivalent to contains(map, key)
            // To delete a key-value pair from the _entries array in O(1), we swap the entry to delete with the last one
            // in the array, and then remove the last entry (sometimes called as 'swap and pop').
            // This modifies the order of the array, as noted in {at}.

            uint256 toDeleteIndex = keyIndex - 1;
            uint256 lastIndex = map._entries.length - 1;

            // When the entry to delete is the last one, the swap operation is unnecessary. However, since this occurs
            // so rarely, we still do the swap anyway to avoid the gas cost of adding an 'if' statement.

            MapEntry storage lastEntry = map._entries[lastIndex];

            // Move the last entry to the index where the entry to delete is
            map._entries[toDeleteIndex] = lastEntry;
            // Update the index for the moved entry
            map._indexes[lastEntry._key] = toDeleteIndex + 1; // All indexes are 1-based

            // Delete the slot where the moved entry was stored
            map._entries.pop();

            // Delete the index for the deleted slot
            delete map._indexes[key];

            return true;
        } else {
            return false;
        }
    }

    /**
     * @dev Returns true if the key is in the map. O(1).
     */
    function _contains(Map storage map, bytes32 key) private view returns (bool) {
        return map._indexes[key] != 0;
    }

    /**
     * @dev Returns the number of key-value pairs in the map. O(1).
     */
    function _length(Map storage map) private view returns (uint256) {
        return map._entries.length;
    }

   /**
    * @dev Returns the key-value pair stored at position `index` in the map. O(1).
    *
    * Note that there are no guarantees on the ordering of entries inside the
    * array, and it may change when more entries are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {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);
    }

    /**
     * @dev Tries to returns the value associated with `key`.  O(1).
     * Does not revert if `key` is not in the map.
     */
    function _tryGet(Map storage map, bytes32 key) private view returns (bool, bytes32) {
        uint256 keyIndex = map._indexes[key];
        if (keyIndex == 0) return (false, 0); // Equivalent to contains(map, key)
        return (true, map._entries[keyIndex - 1]._value); // All indexes are 1-based
    }

    /**
     * @dev Returns the value associated with `key`.  O(1).
     *
     * Requirements:
     *
     * - `key` must be in the map.
     */
    function _get(Map storage map, bytes32 key) private view returns (bytes32) {
        uint256 keyIndex = map._indexes[key];
        require(keyIndex != 0, "EnumerableMap: nonexistent key"); // Equivalent to contains(map, key)
        return map._entries[keyIndex - 1]._value; // All indexes are 1-based
    }

    /**
     * @dev Same as {_get}, with a custom error message when `key` is not in the map.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {_tryGet}.
     */
    function _get(Map storage map, bytes32 key, string memory errorMessage) private view returns (bytes32) {
        uint256 keyIndex = map._indexes[key];
        require(keyIndex != 0, errorMessage); // Equivalent to contains(map, key)
        return map._entries[keyIndex - 1]._value; // All indexes are 1-based
    }

    // UintToAddressMap

    struct UintToAddressMap {
        Map _inner;
    }

    /**
     * @dev Adds a key-value pair to a map, or updates the value for an existing
     * key. O(1).
     *
     * Returns true if the key was added to the map, that is if it was not
     * already present.
     */
    function set(UintToAddressMap storage map, uint256 key, address value) internal returns (bool) {
        return _set(map._inner, bytes32(key), bytes32(uint256(uint160(value))));
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the key was removed from the map, that is if it was present.
     */
    function remove(UintToAddressMap storage map, uint256 key) internal returns (bool) {
        return _remove(map._inner, bytes32(key));
    }

    /**
     * @dev Returns true if the key is in the map. O(1).
     */
    function contains(UintToAddressMap storage map, uint256 key) internal view returns (bool) {
        return _contains(map._inner, bytes32(key));
    }

    /**
     * @dev Returns the number of elements in the map. O(1).
     */
    function length(UintToAddressMap storage map) internal view returns (uint256) {
        return _length(map._inner);
    }

   /**
    * @dev Returns the element stored at position `index` in the set. O(1).
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    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))));
    }

    /**
     * @dev Tries to returns the value associated with `key`.  O(1).
     * Does not revert if `key` is not in the map.
     *
     * _Available since v3.4._
     */
    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))));
    }

    /**
     * @dev Returns the value associated with `key`.  O(1).
     *
     * Requirements:
     *
     * - `key` must be in the map.
     */
    function get(UintToAddressMap storage map, uint256 key) internal view returns (address) {
        return address(uint160(uint256(_get(map._inner, bytes32(key)))));
    }

    /**
     * @dev Same as {get}, with a custom error message when `key` is not in the map.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryGet}.
     */
    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: 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.
 *
 * Sets have the following properties:
 *
 * - Elements are added, removed, and checked for existence in constant time
 * (O(1)).
 * - Elements are enumerated in O(n). No guarantees are made on the ordering.
 *
 * ```
 * contract Example {
 *     // Add the library methods
 *     using EnumerableSet for EnumerableSet.AddressSet;
 *
 *     // Declare a set state variable
 *     EnumerableSet.AddressSet private mySet;
 * }
 * ```
 *
 * As of v3.3.0, sets of type `bytes32` (`Bytes32Set`), `address` (`AddressSet`)
 * and `uint256` (`UintSet`) are supported.
 */
library EnumerableSet {
    // To implement this library for multiple types with as little code
    // repetition as possible, we write it in terms of a generic Set type with
    // bytes32 values.
    // The Set implementation uses private functions, and user-facing
    // implementations (such as AddressSet) are just wrappers around the
    // underlying Set.
    // This means that we can only create new EnumerableSets for types that fit
    // in bytes32.

    struct Set {
        // Storage of set values
        bytes32[] _values;

        // Position of the value in the `values` array, plus 1 because index 0
        // means a value is not in the set.
        mapping (bytes32 => uint256) _indexes;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function _add(Set storage set, bytes32 value) private returns (bool) {
        if (!_contains(set, value)) {
            set._values.push(value);
            // The value is stored at length-1, but we add 1 to all indexes
            // and use 0 as a sentinel value
            set._indexes[value] = set._values.length;
            return true;
        } else {
            return false;
        }
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function _remove(Set storage set, bytes32 value) private returns (bool) {
        // We read and store the value's index to prevent multiple reads from the same storage slot
        uint256 valueIndex = set._indexes[value];

        if (valueIndex != 0) { // Equivalent to contains(set, value)
            // To delete an element from the _values array in O(1), we swap the element to delete with the last one in
            // the array, and then remove the last element (sometimes called as 'swap and pop').
            // This modifies the order of the array, as noted in {at}.

            uint256 toDeleteIndex = valueIndex - 1;
            uint256 lastIndex = set._values.length - 1;

            // When the value to delete is the last one, the swap operation is unnecessary. However, since this occurs
            // so rarely, we still do the swap anyway to avoid the gas cost of adding an 'if' statement.

            bytes32 lastvalue = set._values[lastIndex];

            // Move the last value to the index where the value to delete is
            set._values[toDeleteIndex] = lastvalue;
            // Update the index for the moved value
            set._indexes[lastvalue] = toDeleteIndex + 1; // All indexes are 1-based

            // Delete the slot where the moved value was stored
            set._values.pop();

            // Delete the index for the deleted slot
            delete set._indexes[value];

            return true;
        } else {
            return false;
        }
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function _contains(Set storage set, bytes32 value) private view returns (bool) {
        return set._indexes[value] != 0;
    }

    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function _length(Set storage set) private view returns (uint256) {
        return set._values.length;
    }

   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {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];
    }

    // Bytes32Set

    struct Bytes32Set {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(Bytes32Set storage set, bytes32 value) internal returns (bool) {
        return _add(set._inner, value);
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(Bytes32Set storage set, bytes32 value) internal returns (bool) {
        return _remove(set._inner, value);
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(Bytes32Set storage set, bytes32 value) internal view returns (bool) {
        return _contains(set._inner, value);
    }

    /**
     * @dev Returns the number of values in the set. O(1).
     */
    function length(Bytes32Set storage set) internal view returns (uint256) {
        return _length(set._inner);
    }

   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(Bytes32Set storage set, uint256 index) internal view returns (bytes32) {
        return _at(set._inner, index);
    }

    // AddressSet

    struct AddressSet {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(AddressSet storage set, address value) internal returns (bool) {
        return _add(set._inner, bytes32(uint256(uint160(value))));
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(AddressSet storage set, address value) internal returns (bool) {
        return _remove(set._inner, bytes32(uint256(uint160(value))));
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(AddressSet storage set, address value) internal view returns (bool) {
        return _contains(set._inner, bytes32(uint256(uint160(value))));
    }

    /**
     * @dev Returns the number of values in the set. O(1).
     */
    function length(AddressSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }

   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(AddressSet storage set, uint256 index) internal view returns (address) {
        return address(uint160(uint256(_at(set._inner, index))));
    }


    // UintSet

    struct UintSet {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(UintSet storage set, uint256 value) internal returns (bool) {
        return _add(set._inner, bytes32(value));
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(UintSet storage set, uint256 value) internal returns (bool) {
        return _remove(set._inner, bytes32(value));
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(UintSet storage set, uint256 value) internal view returns (bool) {
        return _contains(set._inner, bytes32(value));
    }

    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function length(UintSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }

   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(UintSet storage set, uint256 index) internal view returns (uint256) {
        return uint256(_at(set._inner, index));
    }
}

// File: ERC1155Receiver.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

import "./IERC1155Receiver.sol";
import "./ERC165.sol";

/**
 * @dev _Available since v3.1._
 */
abstract contract ERC1155Receiver is ERC165, IERC1155Receiver {
    constructor() internal {
        _registerInterface(
            ERC1155Receiver(address(0)).onERC1155Received.selector ^
            ERC1155Receiver(address(0)).onERC1155BatchReceived.selector
        );
    }
}

// File: ERC165.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

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 () 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) 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: ERC721.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

import "./Context.sol";
import "./IERC721.sol";
import "./IERC721Metadata.sol";
import "./IERC721Enumerable.sol";
import "./IERC721Receiver.sol";
import "./ERC165.sol";
import "./SafeMath.sol";
import "./Address.sol";
import "./EnumerableSet.sol";
import "./EnumerableMap.sol";
import "./Strings.sol";

/**
 * @title ERC721 Non-Fungible Token Standard basic implementation
 * @dev see https://eips.ethereum.org/EIPS/eip-721
 */
contract ERC721 is Context, ERC165, IERC721, IERC721Metadata, IERC721Enumerable {
    using SafeMath for uint256;
    using Address for address;
    using EnumerableSet for EnumerableSet.UintSet;
    using EnumerableMap for EnumerableMap.UintToAddressMap;
    using Strings for uint256;

    // 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 holder address to their (enumerable) set of owned tokens
    mapping (address => EnumerableSet.UintSet) private _holderTokens;

    // Enumerable mapping from token ids to their owners
    EnumerableMap.UintToAddressMap private _tokenOwners;

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

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

    // Token name
    string private _name;

    // Token symbol
    string private _symbol;

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

    // Base URI
    string private _baseURI;

    /*
     *     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)')) == 0xe985e9c5
     *     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 ^ 0xe985e9c5 ^ 0x23b872dd ^ 0x42842e0e ^ 0xb88d4fde == 0x80ac58cd
     */
    bytes4 private constant _INTERFACE_ID_ERC721 = 0x80ac58cd;

    /*
     *     bytes4(keccak256('name()')) == 0x06fdde03
     *     bytes4(keccak256('symbol()')) == 0x95d89b41
     *     bytes4(keccak256('tokenURI(uint256)')) == 0xc87b56dd
     *
     *     => 0x06fdde03 ^ 0x95d89b41 ^ 0xc87b56dd == 0x5b5e139f
     */
    bytes4 private constant _INTERFACE_ID_ERC721_METADATA = 0x5b5e139f;

    /*
     *     bytes4(keccak256('totalSupply()')) == 0x18160ddd
     *     bytes4(keccak256('tokenOfOwnerByIndex(address,uint256)')) == 0x2f745c59
     *     bytes4(keccak256('tokenByIndex(uint256)')) == 0x4f6ccce7
     *
     *     => 0x18160ddd ^ 0x2f745c59 ^ 0x4f6ccce7 == 0x780e9d63
     */
    bytes4 private constant _INTERFACE_ID_ERC721_ENUMERABLE = 0x780e9d63;

    /**
     * @dev Initializes the contract by setting a `name` and a `symbol` to the token collection.
     */
    constructor (string memory name_, string memory symbol_) public {
        _name = name_;
        _symbol = symbol_;

        // register the supported interfaces to conform to ERC721 via ERC165
        _registerInterface(_INTERFACE_ID_ERC721);
        _registerInterface(_INTERFACE_ID_ERC721_METADATA);
        _registerInterface(_INTERFACE_ID_ERC721_ENUMERABLE);
    }

    /**
     * @dev See {IERC721-balanceOf}.
     */
    function balanceOf(address owner) public view virtual override returns (uint256) {
        require(owner != address(0), "ERC721: balance query for the zero address");
        return _holderTokens[owner].length();
    }

    /**
     * @dev See {IERC721-ownerOf}.
     */
    function ownerOf(uint256 tokenId) public view virtual override returns (address) {
        return _tokenOwners.get(tokenId, "ERC721: owner query for nonexistent token");
    }

    /**
     * @dev See {IERC721Metadata-name}.
     */
    function name() public view virtual override returns (string memory) {
        return _name;
    }

    /**
     * @dev See {IERC721Metadata-symbol}.
     */
    function symbol() public view virtual override returns (string memory) {
        return _symbol;
    }

    /**
     * @dev See {IERC721Metadata-tokenURI}.
     */
    function tokenURI(uint256 tokenId) public view virtual override returns (string memory) {
        require(_exists(tokenId), "ERC721Metadata: URI query for nonexistent token");

        string memory _tokenURI = _tokenURIs[tokenId];
        string memory base = baseURI();

        // If there is no base URI, return the token URI.
        if (bytes(base).length == 0) {
            return _tokenURI;
        }
        // If both are set, concatenate the baseURI and tokenURI (via abi.encodePacked).
        if (bytes(_tokenURI).length > 0) {
            return string(abi.encodePacked(base, _tokenURI));
        }
        // If there is a baseURI but no tokenURI, concatenate the tokenID to the baseURI.
        return string(abi.encodePacked(base, tokenId.toString()));
    }

    /**
    * @dev Returns the base URI set via {_setBaseURI}. This will be
    * automatically added as a prefix in {tokenURI} to each token's URI, or
    * to the token ID if no specific URI is set for that token ID.
    */
    function baseURI() public view virtual returns (string memory) {
        return _baseURI;
    }

    /**
     * @dev See {IERC721Enumerable-tokenOfOwnerByIndex}.
     */
    function tokenOfOwnerByIndex(address owner, uint256 index) public view virtual override returns (uint256) {
        return _holderTokens[owner].at(index);
    }

    /**
     * @dev See {IERC721Enumerable-totalSupply}.
     */
    function totalSupply() public view virtual override returns (uint256) {
        // _tokenOwners are indexed by tokenIds, so .length() returns the number of tokenIds
        return _tokenOwners.length();
    }

    /**
     * @dev See {IERC721Enumerable-tokenByIndex}.
     */
    function tokenByIndex(uint256 index) public view virtual override returns (uint256) {
        (uint256 tokenId, ) = _tokenOwners.at(index);
        return tokenId;
    }

    /**
     * @dev See {IERC721-approve}.
     */
    function approve(address to, uint256 tokenId) public virtual override {
        address owner = ERC721.ownerOf(tokenId);
        require(to != owner, "ERC721: approval to current owner");

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

        _approve(to, tokenId);
    }

    /**
     * @dev See {IERC721-getApproved}.
     */
    function getApproved(uint256 tokenId) public view virtual override returns (address) {
        require(_exists(tokenId), "ERC721: approved query for nonexistent token");

        return _tokenApprovals[tokenId];
    }

    /**
     * @dev See {IERC721-setApprovalForAll}.
     */
    function setApprovalForAll(address operator, bool approved) public virtual override {
        require(operator != _msgSender(), "ERC721: approve to caller");

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

    /**
     * @dev See {IERC721-isApprovedForAll}.
     */
    function isApprovedForAll(address owner, address operator) public view virtual override returns (bool) {
        return _operatorApprovals[owner][operator];
    }

    /**
     * @dev See {IERC721-transferFrom}.
     */
    function transferFrom(address from, address to, uint256 tokenId) public virtual override {
        //solhint-disable-next-line max-line-length
        require(_isApprovedOrOwner(_msgSender(), tokenId), "ERC721: transfer caller is not owner nor approved");

        _transfer(from, to, tokenId);
    }

    /**
     * @dev See {IERC721-safeTransferFrom}.
     */
    function safeTransferFrom(address from, address to, uint256 tokenId) public virtual override {
        safeTransferFrom(from, to, tokenId, "");
    }

    /**
     * @dev See {IERC721-safeTransferFrom}.
     */
    function safeTransferFrom(address from, address to, uint256 tokenId, bytes memory _data) public virtual override {
        require(_isApprovedOrOwner(_msgSender(), tokenId), "ERC721: transfer caller is not owner nor approved");
        _safeTransfer(from, to, tokenId, _data);
    }

    /**
     * @dev Safely transfers `tokenId` token from `from` to `to`, checking first that contract recipients
     * are aware of the ERC721 protocol to prevent tokens from being forever locked.
     *
     * `_data` is additional data, it has no specified format and it is sent in call to `to`.
     *
     * This internal function is equivalent to {safeTransferFrom}, and can be used to e.g.
     * implement alternative mechanisms to perform token transfer, such as signature-based.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must exist and be owned by `from`.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function _safeTransfer(address from, address to, uint256 tokenId, bytes memory _data) internal virtual {
        _transfer(from, to, tokenId);
        require(_checkOnERC721Received(from, to, tokenId, _data), "ERC721: transfer to non ERC721Receiver implementer");
    }

    /**
     * @dev Returns whether `tokenId` exists.
     *
     * Tokens can be managed by their owner or approved accounts via {approve} or {setApprovalForAll}.
     *
     * Tokens start existing when they are minted (`_mint`),
     * and stop existing when they are burned (`_burn`).
     */
    function _exists(uint256 tokenId) internal view virtual returns (bool) {
        return _tokenOwners.contains(tokenId);
    }

    /**
     * @dev Returns whether `spender` is allowed to manage `tokenId`.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function _isApprovedOrOwner(address spender, uint256 tokenId) internal view virtual returns (bool) {
        require(_exists(tokenId), "ERC721: operator query for nonexistent token");
        address owner = ERC721.ownerOf(tokenId);
        return (spender == owner || getApproved(tokenId) == spender || ERC721.isApprovedForAll(owner, spender));
    }

    /**
     * @dev Safely mints `tokenId` and transfers it to `to`.
     *
     * Requirements:
     d*
     * - `tokenId` must not exist.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function _safeMint(address to, uint256 tokenId) internal virtual {
        _safeMint(to, tokenId, "");
    }

    /**
     * @dev Same as {xref-ERC721-_safeMint-address-uint256-}[`_safeMint`], with an additional `data` parameter which is
     * forwarded in {IERC721Receiver-onERC721Received} to contract recipients.
     */
    function _safeMint(address to, uint256 tokenId, bytes memory _data) internal virtual {
        _mint(to, tokenId);
        require(_checkOnERC721Received(address(0), to, tokenId, _data), "ERC721: transfer to non ERC721Receiver implementer");
    }

    /**
     * @dev Mints `tokenId` and transfers it to `to`.
     *
     * WARNING: Usage of this method is discouraged, use {_safeMint} whenever possible
     *
     * Requirements:
     *
     * - `tokenId` must not exist.
     * - `to` cannot be the zero address.
     *
     * Emits a {Transfer} event.
     */
    function _mint(address to, uint256 tokenId) internal virtual {
        require(to != address(0), "ERC721: mint to the zero address");
        require(!_exists(tokenId), "ERC721: token already minted");

        _beforeTokenTransfer(address(0), to, tokenId);

        _holderTokens[to].add(tokenId);

        _tokenOwners.set(tokenId, to);

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

    /**
     * @dev Destroys `tokenId`.
     * The approval is cleared when the token is burned.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     *
     * Emits a {Transfer} event.
     */
    function _burn(uint256 tokenId) internal virtual {
        address owner = ERC721.ownerOf(tokenId); // internal owner

        _beforeTokenTransfer(owner, address(0), tokenId);

        // Clear approvals
        _approve(address(0), tokenId);

        // Clear metadata (if any)
        if (bytes(_tokenURIs[tokenId]).length != 0) {
            delete _tokenURIs[tokenId];
        }

        _holderTokens[owner].remove(tokenId);

        _tokenOwners.remove(tokenId);

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

    /**
     * @dev Transfers `tokenId` from `from` to `to`.
     *  As opposed to {transferFrom}, this imposes no restrictions on msg.sender.
     *
     * Requirements:
     *
     * - `to` cannot be the zero address.
     * - `tokenId` token must be owned by `from`.
     *
     * Emits a {Transfer} event.
     */
    function _transfer(address from, address to, uint256 tokenId) internal virtual {
        require(ERC721.ownerOf(tokenId) == from, "ERC721: transfer of token that is not own"); // internal owner
        require(to != address(0), "ERC721: transfer to the zero address");

        _beforeTokenTransfer(from, to, tokenId);

        // Clear approvals from the previous owner
        _approve(address(0), tokenId);

        _holderTokens[from].remove(tokenId);
        _holderTokens[to].add(tokenId);

        _tokenOwners.set(tokenId, to);

        emit Transfer(from, to, tokenId);
    }

    /**
     * @dev Sets `_tokenURI` as the tokenURI of `tokenId`.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function _setTokenURI(uint256 tokenId, string memory _tokenURI) internal virtual {
        require(_exists(tokenId), "ERC721Metadata: URI set of nonexistent token");
        _tokenURIs[tokenId] = _tokenURI;
    }

    /**
     * @dev Internal function to set the base URI for all token IDs. It is
     * automatically added as a prefix to the value returned in {tokenURI},
     * or to the token ID if {tokenURI} is empty.
     */
    function _setBaseURI(string memory baseURI_) internal virtual {
        _baseURI = baseURI_;
    }

    /**
     * @dev Internal function to invoke {IERC721Receiver-onERC721Received} on a target address.
     * The call is not executed if the target address is not a contract.
     *
     * @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)
        private returns (bool)
    {
        if (!to.isContract()) {
            return true;
        }
        bytes memory returndata = to.functionCall(abi.encodeWithSelector(
            IERC721Receiver(to).onERC721Received.selector,
            _msgSender(),
            from,
            tokenId,
            _data
        ), "ERC721: 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(ERC721.ownerOf(tokenId), to, tokenId); // internal owner
    }

    /**
     * @dev Hook that is called before any token transfer. This includes minting
     * and burning.
     *
     * Calling conditions:
     *
     * - When `from` and `to` are both non-zero, ``from``'s `tokenId` will be
     * transferred to `to`.
     * - When `from` is zero, `tokenId` will be minted for `to`.
     * - When `to` is zero, ``from``'s `tokenId` will be burned.
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _beforeTokenTransfer(address from, address to, uint256 tokenId) internal virtual { }
}

// File: ERC721URIStorage.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.7.4;
pragma experimental ABIEncoderV2;

import "./ERC721.sol";
import "./Operators.sol";

/**
 * @dev this contract used just for override some
 * OpneZeppelin tokenURI() behavior
 * so we need redeclare _tokenURIs becouse in OpenZeppelin
 * ERC721 it has private visibility
 */
abstract contract ERC721URIStorage is ERC721, Operators {
    using Strings for uint256;

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

    /**
     * @dev See {IERC721Metadata-tokenURI}.
     */
    function tokenURI(uint256 tokenId) public view virtual override returns (string memory) {
        require(_exists(tokenId), "ERC721URIStorage: URI query for nonexistent token");

        string memory _tokenURI = _tokenURIs[tokenId];
        string memory base = baseURI();

        // If there is no base URI, return the token URI.
        if (bytes(base).length == 0) {
            return _tokenURI;
        }
        // If both are set, concatenate the baseURI and tokenURI (via abi.encodePacked).
        if (bytes(_tokenURI).length > 0) {
            //return string(abi.encodePacked(base, _tokenURI));
            //Due customer requirements
            return _tokenURI;
        }

        return super.tokenURI(tokenId);
    }

    /**
     * @dev Sets `_tokenURI` as the tokenURI of `tokenId`.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function _setTokenURI(uint256 tokenId, string memory _tokenURI) internal virtual override {
        require(_exists(tokenId), "ERC721URIStorage: URI set of nonexistent token");
        _tokenURIs[tokenId] = _tokenURI;
    }

    /**
     * @dev Destroys `tokenId`.
     * The approval is cleared when the token is burned.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     *
     * Emits a {Transfer} event.
     */
    function _burn(uint256 tokenId) internal virtual override {
        super._burn(tokenId);

        if (bytes(_tokenURIs[tokenId]).length != 0) {
            delete _tokenURIs[tokenId];
        }
    }

    function setURI(uint256 tokenId, string calldata _tokenURI) external onlyOperator {
        _setTokenURI(tokenId, _tokenURI);
    }

    function setURIBatch(uint256[] calldata tokenId, string[] calldata _tokenURI) external onlyOperator {
        require(tokenId.length == _tokenURI.length, "tokenId length is not equal to _tokenURI length");
        for (uint i = 0; i < tokenId.length; i++) {
            _setTokenURI(tokenId[i], _tokenURI[i]);
        }
    }

    address public signerAddress;

    function setSigner(address _newSigner) external onlyOwner {
        signerAddress = _newSigner;
    }

    function hashArguments(uint256 tokenId, string calldata _tokenURI)
        public pure returns (bytes32 msgHash)
    {
        msgHash = keccak256(abi.encode(tokenId, _tokenURI));
    }

    function getSigner(uint256 tokenId, string calldata _tokenURI, uint8 _v, bytes32 _r, bytes32 _s)
        public
        pure
        returns (address)
    {
        bytes32 msgHash = hashArguments(tokenId, _tokenURI);
        return ecrecover(msgHash, _v, _r, _s);
    }

    function isValidSignature(uint256 tokenId, string calldata _tokenURI, uint8 _v, bytes32 _r, bytes32 _s)
        public
        view
        returns (bool)
    {
        return getSigner(tokenId, _tokenURI, _v, _r, _s) == signerAddress;
    }

    /**
       * @dev Sets token URI using signature
       * This method can be called by anyone, who has signature,
       * that was created by signer role
       */
    function setURISigned(uint256 tokenId, string calldata _tokenURI, uint8 _v, bytes32 _r, bytes32 _s) external {
        require(isValidSignature(tokenId, _tokenURI, _v, _r, _s), "Invalid signature");
        _setTokenURI(tokenId, _tokenURI);
    }

}

// File: IERC1155.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.2 <0.8.0;

import "./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: IERC1155Receiver.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

import "./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: IERC165.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @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: IERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

// File: IERC721.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.2 <0.8.0;

import "./IERC165.sol";

/**
 * @dev Required interface of an ERC721 compliant contract.
 */
interface IERC721 is IERC165 {
    /**
     * @dev Emitted when `tokenId` token is transferred from `from` to `to`.
     */
    event Transfer(address indexed from, address indexed to, uint256 indexed tokenId);

    /**
     * @dev Emitted when `owner` enables `approved` to manage the `tokenId` token.
     */
    event Approval(address indexed owner, address indexed approved, uint256 indexed tokenId);

    /**
     * @dev Emitted when `owner` enables or disables (`approved`) `operator` to manage all of its assets.
     */
    event ApprovalForAll(address indexed owner, address indexed operator, bool approved);

    /**
     * @dev Returns the number of tokens in ``owner``'s account.
     */
    function balanceOf(address owner) external view returns (uint256 balance);

    /**
     * @dev Returns the owner of the `tokenId` token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function ownerOf(uint256 tokenId) external view returns (address owner);

    /**
     * @dev Safely transfers `tokenId` token from `from` to `to`, checking first that contract recipients
     * are aware of the ERC721 protocol to prevent tokens from being forever locked.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must exist and be owned by `from`.
     * - If the caller is not `from`, it must be have been allowed to move this token by either {approve} or {setApprovalForAll}.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function safeTransferFrom(address from, address to, uint256 tokenId) external;

    /**
     * @dev Transfers `tokenId` token from `from` to `to`.
     *
     * WARNING: Usage of this method is discouraged, use {safeTransferFrom} whenever possible.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must be owned by `from`.
     * - If the caller is not `from`, it must be approved to move this token by either {approve} or {setApprovalForAll}.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address from, address to, uint256 tokenId) external;

    /**
     * @dev Gives permission to `to` to transfer `tokenId` token to another account.
     * The approval is cleared when the token is transferred.
     *
     * Only a single account can be approved at a time, so approving the zero address clears previous approvals.
     *
     * Requirements:
     *
     * - The caller must own the token or be an approved operator.
     * - `tokenId` must exist.
     *
     * Emits an {Approval} event.
     */
    function approve(address to, uint256 tokenId) external;

    /**
     * @dev Returns the account approved for `tokenId` token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function getApproved(uint256 tokenId) external view returns (address operator);

    /**
     * @dev Approve or remove `operator` as an operator for the caller.
     * Operators can call {transferFrom} or {safeTransferFrom} for any token owned by the caller.
     *
     * Requirements:
     *
     * - The `operator` cannot be the caller.
     *
     * Emits an {ApprovalForAll} event.
     */
    function setApprovalForAll(address operator, bool _approved) external;

    /**
     * @dev Returns if the `operator` is allowed to manage all of the assets of `owner`.
     *
     * See {setApprovalForAll}
     */
    function isApprovedForAll(address owner, address operator) external view returns (bool);

    /**
      * @dev Safely transfers `tokenId` token from `from` to `to`.
      *
      * Requirements:
      *
      * - `from` cannot be the zero address.
      * - `to` cannot be the zero address.
      * - `tokenId` token must exist and be owned by `from`.
      * - If the caller is not `from`, it must be approved to move this token by either {approve} or {setApprovalForAll}.
      * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
      *
      * Emits a {Transfer} event.
      */
    function safeTransferFrom(address from, address to, uint256 tokenId, bytes calldata data) external;
}

// File: IERC721Enumerable.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.2 <0.8.0;

import "./IERC721.sol";

/**
 * @title ERC-721 Non-Fungible Token Standard, optional enumeration extension
 * @dev See https://eips.ethereum.org/EIPS/eip-721
 */
interface IERC721Enumerable is IERC721 {

    /**
     * @dev Returns the total amount of tokens stored by the contract.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns a token ID owned by `owner` at a given `index` of its token list.
     * Use along with {balanceOf} to enumerate all of ``owner``'s tokens.
     */
    function tokenOfOwnerByIndex(address owner, uint256 index) external view returns (uint256 tokenId);

    /**
     * @dev Returns a token ID at a given `index` of all the tokens stored by the contract.
     * Use along with {totalSupply} to enumerate all tokens.
     */
    function tokenByIndex(uint256 index) external view returns (uint256);
}

// File: IERC721Metadata.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.2 <0.8.0;

import "./IERC721.sol";

/**
 * @title ERC-721 Non-Fungible Token Standard, optional metadata extension
 * @dev See https://eips.ethereum.org/EIPS/eip-721
 */
interface IERC721Metadata is IERC721 {

    /**
     * @dev Returns the token collection name.
     */
    function name() external view returns (string memory);

    /**
     * @dev Returns the token collection symbol.
     */
    function symbol() external view returns (string memory);

    /**
     * @dev Returns the Uniform Resource Identifier (URI) for `tokenId` token.
     */
    function tokenURI(uint256 tokenId) external view returns (string memory);
}

// File: IERC721Receiver.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @title ERC721 token receiver interface
 * @dev Interface for any contract that wants to support safeTransfers
 * from ERC721 asset contracts.
 */
interface IERC721Receiver {
    /**
     * @dev Whenever an {IERC721} `tokenId` token is transferred to this contract via {IERC721-safeTransferFrom}
     * by `operator` from `from`, this function is called.
     *
     * It must return its Solidity selector to confirm the token transfer.
     * If any other value is returned or the interface is not implemented by the recipient, the transfer will be reverted.
     *
     * The selector can be obtained in Solidity with `IERC721.onERC721Received.selector`.
     */
    function onERC721Received(address operator, address from, uint256 tokenId, bytes calldata data) external returns (bytes4);
}

// File: Operators.sol



// SPDX-License-Identifier: MIT
// Degen'$ Farm: Collectible NFT game (https://degens.farm)
pragma solidity ^0.7.4;

import "./IERC20.sol";
import "./Ownable.sol";

contract Operators is Ownable
{
    mapping (address=>bool) operatorAddress;

    modifier onlyOperator() {
        require(isOperator(msg.sender), "Access denied");
        _;
    }

    function isOwner(address _addr) public view returns (bool) {
        return owner() == _addr;
    }

    function isOperator(address _addr) public view returns (bool) {
        return operatorAddress[_addr] || isOwner(_addr);
    }

    function addOperator(address _newOperator) external onlyOwner {
        require(_newOperator != address(0), "New operator is empty");

        operatorAddress[_newOperator] = true;
    }

    function removeOperator(address _oldOperator) external onlyOwner {
        delete(operatorAddress[_oldOperator]);
    }

    /**
     * @dev Owner can claim any tokens that transferred
     * to this contract address
     */
    function withdrawERC20(IERC20 _tokenContract, address _admin) external onlyOwner
    {
        uint256 balance = _tokenContract.balanceOf(address(this));
        _tokenContract.transfer(_admin, balance);
    }
}

// File: 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.
 *
 * 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 () internal {
        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: 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.
 *
 * 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: Strings.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev String operations.
 */
library Strings {
    /**
     * @dev Converts a `uint256` to its ASCII `string` representation.
     */
    function toString(uint256 value) internal pure returns (string memory) {
        // Inspired by OraclizeAPI's implementation - MIT licence
        // https://github.com/oraclize/ethereum-api/blob/b42146b063c7d6ee1358846c198246239e9360e8/oraclizeAPI_0.4.25.sol

        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);
    }
}