// File: contracts/EggMarket.sol



// SPDX-License-Identifier: GPL-3.0-only
pragma solidity ^0.8.0;

import "@openzeppelin/contracts/utils/Address.sol";
import "./access/BaseAccessControl.sol";
import "./structs/DragonInfo.sol";
import "./EggToken.sol";

contract EggMarket is BaseAccessControl {
    
    using Address for address payable;
    
    address private _tokenAddress;
    bool private _publicSaleStarted = false;

    mapping(DragonInfo.Types => uint) private _currentPresaleCounts;
    mapping(DragonInfo.Types => uint) private _presaleRemainingCounts;
    mapping(DragonInfo.Types => uint) private _maxBuyCounts;
    mapping(DragonInfo.Types => uint) private _presaleMaxBuyCounts;
    mapping(DragonInfo.Types => uint) private _totalAllowedPresaleCounts;
    mapping(DragonInfo.Types => uint) private _presalePrices;
    mapping(DragonInfo.Types => uint) private _publicPrices;
    mapping(DragonInfo.Types => mapping(address => uint)) private _presales;

    event TokenPresold(address indexed buyer, address indexed to, uint count, DragonInfo.Types dragonType);
    event TokenBought(address indexed buyer, address indexed to, uint tokenId, DragonInfo.Types dragonType);
    event TokenClaimed(address indexed claimer, address indexed to, uint tokenId);
    event PresaleAllowed(address operator, uint totalAllowedPresaleCount, uint presalePrice, DragonInfo.Types dragonType);
    event PublicSaleStarted(address operator, uint legendaryPrice, uint epicPrice, uint randomPrice);
    event EthersWithdrawn(address operator, address indexed to, uint amount);

    constructor(address accessControl, address eggToken) 
    BaseAccessControl(accessControl) {
        _tokenAddress = eggToken;
        
        _presaleMaxBuyCounts[DragonInfo.Types.Unknown] = 5;
        _presaleMaxBuyCounts[DragonInfo.Types.Epic20] = 1;
        _presaleMaxBuyCounts[DragonInfo.Types.Legendary] = 1;

        _maxBuyCounts[DragonInfo.Types.Unknown] = 5;
        _maxBuyCounts[DragonInfo.Types.Epic20] = 1;
        _maxBuyCounts[DragonInfo.Types.Legendary] = 1;
    }

    function tokenAddress() public view returns (address) {
        return _tokenAddress;
    }

    function setTokenAddress(address newAddress) external onlyRole(CEO_ROLE) {
        address previousAddress = _tokenAddress;
        _tokenAddress = newAddress;
        emit AddressChanged("token", previousAddress, newAddress);
    }

    function presalePrice(DragonInfo.Types drgType) public view returns(uint) {
        return _presalePrices[drgType];
    }

    function setPresalePrice(DragonInfo.Types drgType, uint newValue) external onlyRole(CFO_ROLE) {
        uint previousValue = _presalePrices[drgType];
        _presalePrices[drgType] = newValue;
        emit ValueChanged(string(abi.encodePacked("presalePrices.", drgType)), previousValue, newValue);
    }

    function presaleMaxBuyCount(DragonInfo.Types drgType) public view returns(uint) {
        return _presaleMaxBuyCounts[drgType];
    }

    function setPresaleMaxBuyCount(DragonInfo.Types drgType, uint newValue) external onlyRole(CFO_ROLE) {
        uint previousValue = _presaleMaxBuyCounts[drgType];
        _presaleMaxBuyCounts[drgType] = newValue;
        emit ValueChanged(string(abi.encodePacked("presaleMaxBuyCounts.", drgType)), previousValue, newValue);
    }

    function totalAllowedPresaleCount(DragonInfo.Types drgType) public view returns(uint) {
        return _totalAllowedPresaleCounts[drgType];
    }

    function currentPresaleCount(DragonInfo.Types drgType) public view returns(uint) {
        return _currentPresaleCounts[drgType];
    }

    function presaleRemainingCount(DragonInfo.Types drgType) public view returns(uint) {
        return _presaleRemainingCounts[drgType];
    }

    function allowPresale(DragonInfo.Types drgType, uint totalAllowedPresaleCnt, uint psPrice) external onlyRole(CFO_ROLE) {
        require(!publicSaleStarted(), "EggMarket: unable to allow presale");
        uint totalEggSupply = EggToken(tokenAddress()).totalEggSupply(drgType);
        require(presaleRemainingCount(drgType) + totalAllowedPresaleCnt <= totalEggSupply, 
            "EggMarket: unable to allow presale with the given count");
        _totalAllowedPresaleCounts[drgType] = totalAllowedPresaleCnt;
        _presalePrices[drgType] = psPrice;
        _currentPresaleCounts[drgType] = 0;
        emit PresaleAllowed(_msgSender(), totalAllowedPresaleCnt, psPrice, drgType);
    }

    function publicPrice(DragonInfo.Types drgType) public view returns(uint) {
        return _publicPrices[drgType];
    }

    function setPublicPrice(DragonInfo.Types drgType, uint newValue) external onlyRole(CFO_ROLE) {
        uint previousValue = _publicPrices[drgType];
        _publicPrices[drgType] = newValue;
        emit ValueChanged(string(abi.encodePacked("publicPrices.", drgType)), previousValue, newValue);
    }

    function maxBuyCount(DragonInfo.Types drgType) public view returns(uint) {
        return _maxBuyCounts[drgType];
    }

    function setMaxBuyCount(DragonInfo.Types drgType, uint newValue) external onlyRole(CFO_ROLE) {
        uint previousValue = _maxBuyCounts[drgType];
        _maxBuyCounts[drgType] = newValue;
        emit ValueChanged(string(abi.encodePacked("maxBuyCount.", drgType)), previousValue, newValue);
    }

    function publicSaleStarted() public view returns(bool) {
        return _publicSaleStarted;
    }

    function togglePublicSaleStarted(
        uint legendaryPrice, 
        uint epicPrice, 
        uint randomPrice) external onlyRole(CFO_ROLE) {
        _publicSaleStarted = true;
        
        _publicPrices[DragonInfo.Types.Legendary] = legendaryPrice;
        _publicPrices[DragonInfo.Types.Epic20] = epicPrice;
        _publicPrices[DragonInfo.Types.Unknown] = randomPrice;

        emit PublicSaleStarted(_msgSender(), legendaryPrice, epicPrice, randomPrice);
    }

    function buy(DragonInfo.Types drgType, address to, uint count) external payable {
        require(!Address.isContract(to), "EggMarket: address cannot be contract");
        if (publicSaleStarted()) {
            _buy(drgType, to, count);
        }
        else {
            _presaleBuy(drgType, to, count);
        }
    }

    function claim(DragonInfo.Types drgType, address to, uint count) external {
        require(publicSaleStarted(), "EggMarket: unable to claim");
        require(!Address.isContract(to), "EggMarket: address cannot be contract");
        require(_presales[drgType][_msgSender()] >= count, "EggMarket: bad count");
        EggToken eggt = EggToken(tokenAddress());
        for (uint i = 0; i < count; i++) {
            uint tokenId = eggt.mint(to, drgType);
            emit TokenClaimed(_msgSender(), to, tokenId);
        }
        _presales[drgType][_msgSender()] -= count;
        _presaleRemainingCounts[drgType] -= count;
    }

    function withdrawEthers(uint amount, address payable to) external virtual onlyRole(CFO_ROLE) {
        to.sendValue(amount);
        emit EthersWithdrawn(_msgSender(), to, amount);
    }

    function _buy(DragonInfo.Types drgType, address to, uint count) internal {
        require(count <= maxBuyCount(drgType), "EggMarket: bad count");
        EggToken et = EggToken(tokenAddress());
        uint totalEggSupply = et.totalEggSupply(drgType);
        uint currentEggCount = et.currentEggCount(drgType);
        require(presaleRemainingCount(drgType) + currentEggCount + count <= totalEggSupply, 
            "EggMarket: unable to buy such amount of eggs");
        require(msg.value >= count * publicPrice(drgType), 
            "EggMarket: incorrect amount sent to the contract");
        EggToken eggt = EggToken(tokenAddress());
        for (uint i = 0; i < count; i++) {
            uint tokenId = eggt.mint(to, drgType);
            emit TokenBought(_msgSender(), to, tokenId, drgType);
        }
    }

    function _presaleBuy(DragonInfo.Types drgType, address to, uint count) internal {
        require(currentPresaleCount(drgType) + count <= totalAllowedPresaleCount(drgType), "EggMarket: exceed total allowed presale count");
        require(_presales[drgType][to] + count <= presaleMaxBuyCount(drgType), "EggMarket: exceed max presale count per user");
        require(msg.value >= count * presalePrice(drgType), "EggMarket: incorrect amount sent to the contract");
        _presales[drgType][to] += count;
        _currentPresaleCounts[drgType] += count;
        _presaleRemainingCounts[drgType] += count;
        emit TokenPresold(_msgSender(), to, count, drgType);
    }
}

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



// SPDX-License-Identifier: MIT

pragma solidity ^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;
        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");

        (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");

        (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");

        (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");

        (bool success, bytes memory returndata) = target.delegatecall(data);
        return verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Tool to verifies that a low level call was successful, and revert if it wasn't, either by bubbling the
     * revert reason using the provided one.
     *
     * _Available since v4.3._
     */
    function verifyCallResult(
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal 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

                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

// File: contracts/access/BaseAccessControl.sol



// SPDX-License-Identifier: GPL-3.0-only
pragma solidity ^0.8.0;

import "@openzeppelin/contracts/access/IAccessControl.sol";
import "@openzeppelin/contracts/utils/Context.sol";
import "@openzeppelin/contracts/utils/Strings.sol";
import "../interfaces/IChangeableVariables.sol";

abstract contract BaseAccessControl is Context, IChangeableVariables {

    bytes32 public constant CEO_ROLE = keccak256("CEO");
    bytes32 public constant CFO_ROLE = keccak256("CFO");
    bytes32 public constant COO_ROLE = keccak256("COO");

    address private _accessControl;

    modifier onlyRole(bytes32 role) {
        _checkRole(role, _msgSender());
        _;
    }

    constructor (address accessControl) Context() {
        _accessControl = accessControl;
    }

    function accessControlAddress() public view returns (address) {
        return _accessControl;
    }

    function setAccessControlAddress(address newAddress) external onlyRole(CEO_ROLE) {
        address previousAddress = _accessControl;
        _accessControl = newAddress;
        emit AddressChanged("accessControl", previousAddress, newAddress);
    }

    function hasRole(bytes32 role, address account) public view returns (bool) {
        return IAccessControl(accessControlAddress()).hasRole(role, account);
    }

    function _checkRole(bytes32 role, address account) internal view {
        if (!hasRole(role, account)) {
            revert(
                string(
                    abi.encodePacked(
                        "AccessControl: account ",
                        Strings.toHexString(uint160(account), 20),
                        " is missing role ",
                        Strings.toHexString(uint256(role), 32)
                    )
                )
            );
        }
    }
}

// File: contracts/structs/DragonInfo.sol



// SPDX-License-Identifier: GPL-3.0-only
pragma solidity ^0.8.0;

library DragonInfo {
    
    uint constant MASK = 0xF000000000000000000000000;

    enum Types { 
        Unknown,
        Common, 
        Rare16, 
        Rare17, 
        Rare18, 
        Rare19,
        Epic20, 
        Epic21,
        Epic22,
        Epic23,
        Epic24, 
        Legendary
    }

    struct Details { 
        uint genes;
        uint eggId;
        uint parent1Id;
        uint parent2Id;
        uint generation;
        uint strength;
        Types dragonType;
    }

    function getDetails(uint value) internal pure returns (Details memory) {
        return Details (
            {
                genes: uint256(uint104(value)),
                parent1Id: uint256(uint32(value >> 104)),
                parent2Id: uint256(uint32(value >> 136)),
                generation: uint256(uint16(value >> 168)),
                strength: uint256(uint16(value >> 184)),
                dragonType: Types(uint16(value >> 200)),
                eggId: uint256(uint32(value >> 216))
            }
        );
    }

    function getValue(Details memory details) internal pure returns (uint) {
        uint result = uint(details.genes);
        result |= details.parent1Id << 104;
        result |= details.parent2Id << 136;
        result |= details.generation << 168;
        result |= details.strength << 184;
        result |= uint(details.dragonType) << 200;
        result |= details.eggId << 216;
        return result;
    }

    function calcType(uint genes) internal pure returns (Types) {
        uint mask = MASK;
        uint numRare = 0;
        uint numEpic = 0;
        for (uint i = 0; i < 10; i++) { //just Rare and Epic genes are important to check
            if (genes & mask > 0) {
                if (i < 5) { //Epic-range
                    numEpic++;
                }
                else { //Rare-range
                    numRare++;
                }
            }
            mask = mask >> 4;
        }
        Types result = Types.Unknown;
        if (numEpic == 5 && numRare == 5) {
            result = Types.Legendary;
        }
        else if (numEpic < 5 && numRare == 5) {
            result = Types(6 + numEpic);
        }
        else if (numEpic == 0 && numRare < 5) {
            result = Types(1 + numRare);
        }
        else if (numEpic == 0 && numRare == 0) {
            result = Types.Common;
        }

        return result;
    }

    function calcStrength(uint genes) internal pure returns (uint) {
        uint mask = MASK;
        uint strength = 0;
        for (uint i = 0; i < 25; i++) { 
            uint gLevel = (genes & mask) >> ((24 - i) * 4);
            if (i < 6) { //Epic
                strength += 3 * (25 - i) * gLevel;
            } 
            else if (i < 10) { //Rare 
                strength += 2 * (25 - i) * gLevel;
            }
            else { //Common-range
                if (gLevel > 0) {
                    strength += (25 - i) * gLevel;
                }
                else {
                    strength += (25 - i);
                }
            }
            mask = mask >> 4;
        }
        return strength;
    }

    function calcGeneration(uint g1, uint g2) internal pure returns (uint) {
        return (g1 >= g2 ? g1 : g2) + 1;
    }
}

// File: contracts/EggToken.sol



// SPDX-License-Identifier: GPL-3.0-only
pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
import "@openzeppelin/contracts/utils/math/SafeMath.sol";
import "@openzeppelin/contracts/utils/Counters.sol";
import "@openzeppelin/contracts/utils/Address.sol";
import "./structs/DragonInfo.sol";
import "./structs/EggInfo.sol";
import "./utils/GenesLib.sol";
import "./utils/Random.sol";
import "./access/BaseAccessControl.sol";
import "./DragonCreator.sol";

contract EggToken is ERC721, BaseAccessControl {

    using SafeMath for uint;
    using Address for address;
    using Counters for Counters.Counter;

    uint constant THRESHOLD_DENOMINATOR = 100*1e8;

    Counters.Counter private _tokenIds;

    mapping(uint => uint) private _info;
    mapping(uint => string) private _cids;
    mapping(uint => string) private _hatchCids;

    mapping(DragonInfo.Types => uint) private _randomDragonSupply;
    mapping(DragonInfo.Types => uint) private _totalEggSupply;
    mapping(DragonInfo.Types => uint) private _eggCounts;

    uint internal _totalSupply;
    
    uint internal _hatchTime;
    address internal _dragonCreatorAddress;
    address internal _eggMarketAddress;

    string private _defaultMetadataCid;
    
    GenesLib.GenesRange private COMMON_RANGE;
    GenesLib.GenesRange private RARE_RANGE;
    GenesLib.GenesRange private EPIC_RANGE;

    event EggHatched(address indexed operator, uint eggId, uint dragonId);
    
    constructor(
        uint totalEggSply,
        uint totalEpic20EggSply,
        uint totalLegendaryEggSply,
        uint randomLegendaryDragonSply, 
        uint randomEpic20DragonSply, 
        uint randomCommonDragonSply, 
        uint htchTime,
        string memory defaultCid,
        address accessControl,
        address dragonCreator) ERC721("CryptoDragons Eggs", "CDE") BaseAccessControl(accessControl) {
        
        uint totalRandomEggSupply = randomLegendaryDragonSply + randomEpic20DragonSply + randomCommonDragonSply;
        require(totalEggSply == totalEpic20EggSply + totalLegendaryEggSply + totalRandomEggSupply, 
            "EggToken: inconsistent constructor arguments");
        
        _totalSupply = totalEggSply;

        _totalEggSupply[DragonInfo.Types.Unknown] = totalRandomEggSupply;
        _totalEggSupply[DragonInfo.Types.Epic20] = totalEpic20EggSply;
        _totalEggSupply[DragonInfo.Types.Legendary] = totalLegendaryEggSply;
        
        _randomDragonSupply[DragonInfo.Types.Legendary] = randomLegendaryDragonSply;
        _randomDragonSupply[DragonInfo.Types.Epic20] = randomEpic20DragonSply;
        _randomDragonSupply[DragonInfo.Types.Common] = randomCommonDragonSply;
        
        _hatchTime = htchTime; 
        _defaultMetadataCid = defaultCid;

        _dragonCreatorAddress = dragonCreator;

        COMMON_RANGE = GenesLib.GenesRange({from: 0, to: 15});
        RARE_RANGE = GenesLib.GenesRange({from: 15, to: 20});
        EPIC_RANGE = GenesLib.GenesRange({from: 20, to: 25});
    }

    function totalSupply() public view returns(uint) {
        return _totalSupply;
    }

    function totalEggSupply(DragonInfo.Types drgType) public view returns(uint) {
        return _totalEggSupply[drgType];
    }

    function currentEggCount(DragonInfo.Types drgType) public view returns(uint) {
        return _eggCounts[drgType];
    }

    function defaultMetadataCid() public view returns (string memory){
        return _defaultMetadataCid;
    }

    function setDefaultMetadataCid(string calldata newDefaultCid) external onlyRole(COO_ROLE) {
        _defaultMetadataCid = newDefaultCid;
    }

    function setMetadataCids(uint tokenId, string calldata cid, string calldata hatchCid) external onlyRole(COO_ROLE) {
        require(bytes(cid).length >= 46 && bytes(hatchCid).length >= 46, "EggToken: bad CID");
        require(!hasMetadataCids(tokenId), "EggToken: CIDs are already set");
        _cids[tokenId] = cid;
        _hatchCids[tokenId] = hatchCid;
    }

    function hasMetadataCids(uint tokenId) public view returns(bool) {
        return bytes(_hatchCids[tokenId]).length > 0;
    }

    function hatchTime() public view returns(uint) {
        return _hatchTime;
    }

    function setHatchTime(uint newValue) external onlyRole(COO_ROLE) {
        uint previousValue = _hatchTime;
        _hatchTime = newValue;
        emit ValueChanged("hatchTime", previousValue, newValue);
    }

    function dragonCreatorAddress() public view returns(address) {
        return _dragonCreatorAddress;
    }

    function setDragonCreatorAddress(address newAddress) external onlyRole(CEO_ROLE) {
        address previousAddress = _dragonCreatorAddress;
        _dragonCreatorAddress = newAddress;
        emit AddressChanged("dragonCreator", previousAddress, newAddress);
    }

    function eggMarketAddress() public view returns(address) {
        return _eggMarketAddress;
    }

    function setEggMarketAddress(address newAddress) external onlyRole(CEO_ROLE) {
        address previousAddress = _eggMarketAddress;
        _eggMarketAddress = newAddress;
        emit AddressChanged("eggMarket", previousAddress, newAddress);
    }

    function canHatch(uint tokenId) external view returns(bool) {
        EggInfo.Details memory info = eggInfo(tokenId);
        return _canHatch(info);
    }

    function isHatched(uint tokenId) external view returns(bool) {
        EggInfo.Details memory info = eggInfo(tokenId);
        return info.hatchedAt > 0;
    }

    function eggInfo(uint tokenId) public view returns(EggInfo.Details memory) {
        require(_exists(tokenId), "EggToken: nonexistent token");
        return EggInfo.getDetails(_info[tokenId]);
    }

    function _canHatch(EggInfo.Details memory info) internal view returns(bool) {
        return info.hatchedAt == 0 && block.timestamp >= hatchTime();
    }

    function tokenURI(uint tokenId) public view virtual override returns (string memory) {
        EggInfo.Details memory info = eggInfo(tokenId);
        return string(abi.encodePacked("ipfs://", (info.hatchedAt > 0) ? _hatchCids[tokenId] : _cids[tokenId]));
    }

    function mint(address to, DragonInfo.Types _dragonType) external returns (uint) {
        require(_tokenIds.current() < totalSupply(), "EggToken: supply is exceeded");
        require(hasRole(CEO_ROLE, _msgSender()) || _msgSender() == eggMarketAddress(), 
            "EggToken: not enough privileges to call the method");
        require(to != address(0), "EggToken: wrong address");

        require(_dragonType == DragonInfo.Types.Epic20 
            || _dragonType == DragonInfo.Types.Legendary 
            || _dragonType == DragonInfo.Types.Unknown, "EggToken: wrong dragon type");
        
        require(currentEggCount(_dragonType) < totalEggSupply(_dragonType), 
            "EggToken: total supply for the given dragon type is exceeded");
        
        _eggCounts[_dragonType]++;
        _tokenIds.increment();
        
        uint newTokenId = _tokenIds.current();
        _mint(to, newTokenId);
        
        _info[newTokenId] = EggInfo.getValue(EggInfo.Details({
            mintedAt: block.timestamp,
            dragonType: _dragonType,
            hatchedAt: 0,
            dragonId: 0
        }));
        _cids[newTokenId] = defaultMetadataCid();

        return newTokenId;
    }

    function hatch(uint tokenId) external {
        EggInfo.Details memory info = eggInfo(tokenId);
        require(ownerOf(tokenId) == _msgSender(), "EggToken: hatch caller is not owner");
        require(_canHatch(info), "EggToken: cannot be hatched");

        (DragonInfo.Types dragonType, uint genes) = _randomGenes(info);
        _randomDragonSupply[dragonType]--;

        uint newDragonId = DragonCreator(dragonCreatorAddress()).giveBirth(tokenId, genes, _msgSender());

        info.hatchedAt = block.timestamp;
        info.dragonId = newDragonId;
        _info[tokenId] = EggInfo.getValue(info);

        emit EggHatched(_msgSender(), tokenId, newDragonId);
    }

    function _randomGenes(EggInfo.Details memory info) internal view returns (DragonInfo.Types, uint) {
        DragonInfo.Types t = (info.dragonType == DragonInfo.Types.Unknown) 
            ? _randomDragonType(info.mintedAt ^ block.difficulty ^ block.timestamp) : info.dragonType;
        
        uint genes = GenesLib.randomSetGenesToPositions(
            0, GenesLib.createOrderedRangeArray(COMMON_RANGE.from, COMMON_RANGE.to), 
            Random.rand(info.mintedAt ^ block.number ^ block.difficulty), true);
        
        if (t == DragonInfo.Types.Epic20) {
            genes = GenesLib.randomSetGenesToPositions(
                genes, GenesLib.createOrderedRangeArray(RARE_RANGE.from, RARE_RANGE.to), 
                Random.rand(block.difficulty ^ info.mintedAt ^ block.timestamp), false);
        }
        else if (t == DragonInfo.Types.Legendary) {
            genes = GenesLib.randomSetGenesToPositions(
                genes, GenesLib.createOrderedRangeArray(RARE_RANGE.from, EPIC_RANGE.to), 
                Random.rand(info.mintedAt ^ block.number ^ block.timestamp ^ block.difficulty), false);
        }

        return (t, genes);
    } 
 

    function _randomDragonType(uint salt) internal view returns (DragonInfo.Types) {
        uint remainingLegendarySupply = _randomDragonSupply[DragonInfo.Types.Legendary];
        uint remainingEpic20Supply = _randomDragonSupply[DragonInfo.Types.Epic20];
        uint remainingCommonSupply = _randomDragonSupply[DragonInfo.Types.Common];

        uint remainingTotalSupply = remainingLegendarySupply.add(remainingEpic20Supply).add(remainingCommonSupply);
        
        uint r = Random.rand(salt).mod(THRESHOLD_DENOMINATOR);
        if (r <= _calcDragonThreshold(remainingLegendarySupply, remainingTotalSupply)) {
            return DragonInfo.Types.Legendary;
        }
        else if (r <= _calcDragonThreshold(remainingEpic20Supply, remainingTotalSupply)) {
            return DragonInfo.Types.Epic20;
        }
        else {
            return DragonInfo.Types.Common;
        }
    }

    function _calcDragonThreshold(uint remainingDragonSupply, uint remainingTotalSupply) pure internal returns (uint) {
        return remainingDragonSupply.mul(1e8).div(remainingTotalSupply);
    }
}
// File: @openzeppelin/contracts/access/IAccessControl.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

/**
 * @dev External interface of AccessControl declared to support ERC165 detection.
 */
interface IAccessControl {
    /**
     * @dev Emitted when `newAdminRole` is set as ``role``'s admin role, replacing `previousAdminRole`
     *
     * `DEFAULT_ADMIN_ROLE` is the starting admin for all roles, despite
     * {RoleAdminChanged} not being emitted signaling this.
     *
     * _Available since v3.1._
     */
    event RoleAdminChanged(bytes32 indexed role, bytes32 indexed previousAdminRole, bytes32 indexed newAdminRole);

    /**
     * @dev Emitted when `account` is granted `role`.
     *
     * `sender` is the account that originated the contract call, an admin role
     * bearer except when using {AccessControl-_setupRole}.
     */
    event RoleGranted(bytes32 indexed role, address indexed account, address indexed sender);

    /**
     * @dev Emitted when `account` is revoked `role`.
     *
     * `sender` is the account that originated the contract call:
     *   - if using `revokeRole`, it is the admin role bearer
     *   - if using `renounceRole`, it is the role bearer (i.e. `account`)
     */
    event RoleRevoked(bytes32 indexed role, address indexed account, address indexed sender);

    /**
     * @dev Returns `true` if `account` has been granted `role`.
     */
    function hasRole(bytes32 role, address account) external view returns (bool);

    /**
     * @dev Returns the admin role that controls `role`. See {grantRole} and
     * {revokeRole}.
     *
     * To change a role's admin, use {AccessControl-_setRoleAdmin}.
     */
    function getRoleAdmin(bytes32 role) external view returns (bytes32);

    /**
     * @dev Grants `role` to `account`.
     *
     * If `account` had not been already granted `role`, emits a {RoleGranted}
     * event.
     *
     * Requirements:
     *
     * - the caller must have ``role``'s admin role.
     */
    function grantRole(bytes32 role, address account) external;

    /**
     * @dev Revokes `role` from `account`.
     *
     * If `account` had been granted `role`, emits a {RoleRevoked} event.
     *
     * Requirements:
     *
     * - the caller must have ``role``'s admin role.
     */
    function revokeRole(bytes32 role, address account) external;

    /**
     * @dev Revokes `role` from the calling account.
     *
     * Roles are often managed via {grantRole} and {revokeRole}: this function's
     * purpose is to provide a mechanism for accounts to lose their privileges
     * if they are compromised (such as when a trusted device is misplaced).
     *
     * If the calling account had been granted `role`, emits a {RoleRevoked}
     * event.
     *
     * Requirements:
     *
     * - the caller must be `account`.
     */
    function renounceRole(bytes32 role, address account) external;
}

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



// SPDX-License-Identifier: MIT

pragma solidity ^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 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) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }
}

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



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

/**
 * @dev String operations.
 */
library Strings {
    bytes16 private constant _HEX_SYMBOLS = "0123456789abcdef";

    /**
     * @dev Converts a `uint256` to its ASCII `string` decimal 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);
        while (value != 0) {
            digits -= 1;
            buffer[digits] = bytes1(uint8(48 + uint256(value % 10)));
            value /= 10;
        }
        return string(buffer);
    }

    /**
     * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation.
     */
    function toHexString(uint256 value) internal pure returns (string memory) {
        if (value == 0) {
            return "0x00";
        }
        uint256 temp = value;
        uint256 length = 0;
        while (temp != 0) {
            length++;
            temp >>= 8;
        }
        return toHexString(value, length);
    }

    /**
     * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation with fixed length.
     */
    function toHexString(uint256 value, uint256 length) internal pure returns (string memory) {
        bytes memory buffer = new bytes(2 * length + 2);
        buffer[0] = "0";
        buffer[1] = "x";
        for (uint256 i = 2 * length + 1; i > 1; --i) {
            buffer[i] = _HEX_SYMBOLS[value & 0xf];
            value >>= 4;
        }
        require(value == 0, "Strings: hex length insufficient");
        return string(buffer);
    }
}

// File: contracts/interfaces/IChangeableVariables.sol



// SPDX-License-Identifier: GPL-3.0-only
pragma solidity ^0.8.0;

interface IChangeableVariables {
    event AddressChanged(string indexed fieldName, address previousAddress, address newAddress);
    event ValueChanged(string indexed fieldName, uint previousValue, uint newValue);
    event BoolValueChanged(string indexed fieldName, bool previousValue, bool newValue);
}
// File: @openzeppelin/contracts/token/ERC721/ERC721.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "./IERC721.sol";
import "./IERC721Receiver.sol";
import "./extensions/IERC721Metadata.sol";
import "../../utils/Address.sol";
import "../../utils/Context.sol";
import "../../utils/Strings.sol";
import "../../utils/introspection/ERC165.sol";

/**
 * @dev Implementation of https://eips.ethereum.org/EIPS/eip-721[ERC721] Non-Fungible Token Standard, including
 * the Metadata extension, but not including the Enumerable extension, which is available separately as
 * {ERC721Enumerable}.
 */
contract ERC721 is Context, ERC165, IERC721, IERC721Metadata {
    using Address for address;
    using Strings for uint256;

    // Token name
    string private _name;

    // Token symbol
    string private _symbol;

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

    // Mapping owner address to token count
    mapping(address => uint256) private _balances;

    // 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;

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

    /**
     * @dev See {IERC165-supportsInterface}.
     */
    function supportsInterface(bytes4 interfaceId) public view virtual override(ERC165, IERC165) returns (bool) {
        return
            interfaceId == type(IERC721).interfaceId ||
            interfaceId == type(IERC721Metadata).interfaceId ||
            super.supportsInterface(interfaceId);
    }

    /**
     * @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 _balances[owner];
    }

    /**
     * @dev See {IERC721-ownerOf}.
     */
    function ownerOf(uint256 tokenId) public view virtual override returns (address) {
        address owner = _owners[tokenId];
        require(owner != address(0), "ERC721: owner query for nonexistent token");
        return owner;
    }

    /**
     * @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 baseURI = _baseURI();
        return bytes(baseURI).length > 0 ? string(abi.encodePacked(baseURI, tokenId.toString())) : "";
    }

    /**
     * @dev Base URI for computing {tokenURI}. If set, the resulting URI for each
     * token will be the concatenation of the `baseURI` and the `tokenId`. Empty
     * by default, can be overriden in child contracts.
     */
    function _baseURI() internal view virtual returns (string memory) {
        return "";
    }

    /**
     * @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 || 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 _owners[tokenId] != address(0);
    }

    /**
     * @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 || isApprovedForAll(owner, spender));
    }

    /**
     * @dev Safely mints `tokenId` and transfers it to `to`.
     *
     * Requirements:
     *
     * - `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);

        _balances[to] += 1;
        _owners[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);

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

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

        _balances[owner] -= 1;
        delete _owners[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");
        require(to != address(0), "ERC721: transfer to the zero address");

        _beforeTokenTransfer(from, to, tokenId);

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

        _balances[from] -= 1;
        _balances[to] += 1;
        _owners[tokenId] = to;

        emit Transfer(from, to, tokenId);
    }

    /**
     * @dev Approve `to` to operate on `tokenId`
     *
     * Emits a {Approval} event.
     */
    function _approve(address to, uint256 tokenId) internal virtual {
        _tokenApprovals[tokenId] = to;
        emit Approval(ERC721.ownerOf(tokenId), to, tokenId);
    }

    /**
     * @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()) {
            try IERC721Receiver(to).onERC721Received(_msgSender(), from, tokenId, _data) returns (bytes4 retval) {
                return retval == IERC721Receiver.onERC721Received.selector;
            } catch (bytes memory reason) {
                if (reason.length == 0) {
                    revert("ERC721: transfer to non ERC721Receiver implementer");
                } else {
                    assembly {
                        revert(add(32, reason), mload(reason))
                    }
                }
            }
        } else {
            return true;
        }
    }

    /**
     * @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` and `to` are never both zero.
     *
     * 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: @openzeppelin/contracts/utils/math/SafeMath.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

// CAUTION
// This version of SafeMath should only be used with Solidity 0.8 or later,
// because it relies on the compiler's built in overflow checks.

/**
 * @dev Wrappers over Solidity's arithmetic operations.
 *
 * NOTE: `SafeMath` is no longer needed starting with Solidity 0.8. The compiler
 * now has built in overflow checking.
 */
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) {
        unchecked {
            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) {
        unchecked {
            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) {
        unchecked {
            // 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) {
        unchecked {
            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) {
        unchecked {
            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) {
        return a + b;
    }

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

    /**
     * @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.
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        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) {
        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) {
        unchecked {
            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.
     *
     * 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) {
        unchecked {
            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) {
        unchecked {
            require(b > 0, errorMessage);
            return a % b;
        }
    }
}

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



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

/**
 * @title Counters
 * @author Matt Condon (@shrugs)
 * @dev Provides counters that can only be incremented, decremented or reset. This can be used e.g. to track the number
 * of elements in a mapping, issuing ERC721 ids, or counting request ids.
 *
 * Include with `using Counters for Counters.Counter;`
 */
library Counters {
    struct Counter {
        // This variable should never be directly accessed by users of the library: interactions must be restricted to
        // the library's function. As of Solidity v0.5.2, this cannot be enforced, though there is a proposal to add
        // this feature: see https://github.com/ethereum/solidity/issues/4637
        uint256 _value; // default: 0
    }

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

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

    function decrement(Counter storage counter) internal {
        uint256 value = counter._value;
        require(value > 0, "Counter: decrement overflow");
        unchecked {
            counter._value = value - 1;
        }
    }

    function reset(Counter storage counter) internal {
        counter._value = 0;
    }
}

// File: contracts/structs/EggInfo.sol



// SPDX-License-Identifier: GPL-3.0-only
pragma solidity ^0.8.0;
import "./DragonInfo.sol";

library EggInfo {

    struct Details { 
        uint mintedAt;
        DragonInfo.Types dragonType;
        uint hatchedAt;
        uint dragonId;
    }

    function getDetails(uint value) internal pure returns (Details memory) {
        return Details (
            {
                mintedAt: uint256(uint64(value)),
                dragonType: DragonInfo.Types(uint16(value >> 64)),
                hatchedAt: uint256(uint64(value >> 80)),
                dragonId: uint256(uint32(value >> 144))
            }
        );
    }

    function getValue(Details memory details) internal pure returns (uint) {
        uint result = uint(details.mintedAt);
        result |= uint(details.dragonType) << 64;
        result |= uint(details.hatchedAt) << 80;
        result |= uint(details.dragonId) << 144;
        return result;
    }
}
// File: contracts/utils/GenesLib.sol



// SPDX-License-Identifier: GPL-3.0-only
pragma solidity ^0.8.0;

import "@openzeppelin/contracts/utils/math/SafeMath.sol";
import "./Random.sol";

library GenesLib {
    using SafeMath for uint;
    uint private constant MAGIC_NUM = 0x123456789ABCDEF;

    struct GenesRange {
        uint from;
        uint to;
    }

    function setGeneLevelTo(uint genes, uint level, uint position) internal pure returns (uint) {
        return genes | uint(level << (position * 4));
    }

    function geneLevelAt(uint genes, uint position) internal pure returns (uint) {
        return (genes >> (position * 4)) & 0xF;
    }

    function zeroGenePositionsInRange(uint genes, GenesRange memory range) 
    internal pure returns (uint, uint[] memory) {
        uint[] memory zeroPositions = new uint[](range.to - range.from);
        uint count = 0;
        for (uint pos = range.from; pos < range.to; pos++) {
            uint level = geneLevelAt(genes, pos);
            if (level == 0) {
                zeroPositions[count] = pos;
                count++;
            }
        }
        return (count, zeroPositions);
    }

    function randomGeneLevel(uint randomValue, bool includeZero) internal pure returns (uint) {
        if (includeZero) {
            return randomValue.mod(16);
        }
        else {
            return 1 + randomValue.mod(15);
        }
    }

    function randomInheritGenesInRange(uint genes, uint parent1Genes, uint parent2Genes,
        GenesRange memory range, uint randomValue, bool includeZero) internal pure returns (uint) {
        
        for (uint pos = range.from; pos < range.to; pos++) {
            uint geneLevel1 = geneLevelAt(parent1Genes, pos);
            uint geneLevel2 = geneLevelAt(parent2Genes, pos);

            if (includeZero || (geneLevel1 > 0 && geneLevel2 > 0)) {
                uint d = (pos % 2 == 0) ? ((randomValue >> pos) + (MAGIC_NUM >> pos)) : ~(randomValue >> pos);
                uint r = d.mod(100);
                
                if (r < 45) { //45%
                    genes = setGeneLevelTo(genes, geneLevel1, pos);
                }
                else if (r >= 45 && r < 90) { //45%
                    genes = setGeneLevelTo(genes, geneLevel2, pos);
                }
                else { //10%
                    uint level = d.mod(0xF);
                    genes = setGeneLevelTo(genes, level, pos);
                }
            }
        }
        return genes;
    }

    function randomSetGenesToPositions(uint genes, uint[] memory positions, uint randomValue, bool includeZero) 
    internal pure returns (uint) {
        for (uint i = 0; i < positions.length; i++) {
            genes = setGeneLevelTo(genes, randomGeneLevel(
                (i % 2 > 0) ? ((randomValue >> i) + (MAGIC_NUM >> i)) : ~(randomValue >> i), 
                includeZero), positions[i]);
        }
        return genes;
    }

    function randomGenePositions(GenesRange memory range, uint count, uint randomValue) 
    internal pure returns (uint[] memory) {
        if (count > 0) {
            uint[] memory shuffledRangeArray = 
                Random.shuffle(createOrderedRangeArray(range.from, range.to), randomValue);
            uint[] memory positions = new uint[](count);
            for (uint i = 0; i < count; i++) {
                positions[i] = shuffledRangeArray[i];
            }
            return positions;
        }
        return new uint[](0);
    }

    function createOrderedRangeArray(uint from, uint to) internal pure returns (uint[] memory) {
        uint[] memory rangeArray = new uint[](to - from) ;
        for (uint i = 0; i < rangeArray.length; i++) {
            rangeArray[i] = from + i;
        }
        return rangeArray;
    }

}
// File: contracts/utils/Random.sol



// SPDX-License-Identifier: GPL-3.0-only
pragma solidity ^0.8.0;

library Random {
    function rand(uint salt) internal view returns (uint) {
        return uint(keccak256(abi.encodePacked(block.difficulty, block.timestamp, salt)));
    }

    function randFrom(uint[] memory array, uint from, uint to, uint randomValue)
    internal pure returns (uint) {
        uint count = to - from;
        return array[from + randomValue % count];
    }

    function shuffle(uint[] memory array, uint randomValue) internal pure returns (uint[] memory) {
        for (uint i = 0; i < array.length; i++) {
            uint n = i + randomValue % (array.length - i);
            uint temp = array[n];
            array[n] = array[i];
            array[i] = temp;
        }
        return array;
    }
}
// File: contracts/DragonCreator.sol



// SPDX-License-Identifier: GPL-3.0-only
pragma solidity ^0.8.0;

import "@openzeppelin/contracts/utils/Address.sol";
import "./structs/DragonInfo.sol";
import "./access/BaseAccessControl.sol";
import "./DragonToken.sol";

contract DragonCreator is BaseAccessControl {
    
    using Address for address;

    address private _tokenContractAddress;

    mapping(DragonInfo.Types => uint) private _zeroDragonsIssueLimits;
    mapping(address => bool) private _giveBirthCallers;

    bool private _isChangeOfIssueLimitsAllowed;

    event DragonCreated(
        uint dragonId, 
        uint eggId,
        uint parent1Id,
        uint parent2Id,
        uint generation,
        DragonInfo.Types t,
        uint genes,
        address indexed creator,
        address indexed to);

    constructor(address accessControl, address tknContract) BaseAccessControl(accessControl) {
        _tokenContractAddress = tknContract;
        _isChangeOfIssueLimitsAllowed = true;
    }

    function tokenContract() public view returns (address) {
        return _tokenContractAddress;
    }

    function isChangeOfIssueLimitsAllowed() public view returns (bool) {
        return _isChangeOfIssueLimitsAllowed;
    }

    function currentIssueLimitFor(DragonInfo.Types _dragonType) external view returns (uint) {
        return _zeroDragonsIssueLimits[_dragonType];
    }

    function updateIssueLimitFor(DragonInfo.Types _dragonType, uint newValue) external onlyRole(CEO_ROLE) {
        require(isChangeOfIssueLimitsAllowed(), 
            "DragonCreator: updating the issue limits is not allowed anymore");
        _zeroDragonsIssueLimits[_dragonType] = newValue;
    }

    function blockUpdatingIssueLimitsForever() external onlyRole(CEO_ROLE) {
        _isChangeOfIssueLimitsAllowed = false;
    }
    
    function setGiveBirthCallers(address[] calldata callers, bool value) external onlyRole(CEO_ROLE) {
        for (uint i = 0; i < callers.length; i++) {
            bool previousValue = _giveBirthCallers[callers[i]];
            _giveBirthCallers[callers[i]] = value;
            emit BoolValueChanged(string(abi.encodePacked("giveBirthCallers.", callers[i])), previousValue, value);
        }
    }

    function issue(uint genes, address to) external onlyRole(CEO_ROLE) returns (uint) {
        DragonInfo.Types dragonType = DragonInfo.calcType(genes);
        uint currentLimit = _zeroDragonsIssueLimits[dragonType];
        require(dragonType != DragonInfo.Types.Unknown, "DragonCreator: unable to identify a type of the given dragon");
        require(currentLimit > 0, "DragonCreator: the issue limit has exceeded");
        _zeroDragonsIssueLimits[dragonType] = currentLimit - 1;

        return _createDragon(0, 0, 0, genes, dragonType, to);
    }

    function giveBirth(uint eggId, uint genes, address to) external returns (uint) {
        require(_giveBirthCallers[_msgSender()], "DragonCreator: not enough privileges to call the method");    
        return _createDragon(eggId, 0, 0, genes, DragonInfo.Types.Unknown, to);
    }

    function giveBirth(uint parent1Id, uint parent2Id, uint genes, address to) external returns (uint) {
        require(_giveBirthCallers[_msgSender()], "DragonCreator: not enough privileges to call the method");
        return _createDragon(0, parent1Id, parent2Id, genes, DragonInfo.Types.Unknown, to);
    }

    function _createDragon(uint _eggId, uint _parent1Id, uint _parent2Id, uint _genes, DragonInfo.Types _dragonType, address to)
    internal returns (uint) {
        DragonToken dragonToken = DragonToken(tokenContract());
        DragonInfo.Details memory parent1Details = dragonToken.dragonInfo(_parent1Id);
        DragonInfo.Details memory parent2Details = dragonToken.dragonInfo(_parent2Id);

        if (_parent1Id > 0 && _parent2Id > 0) { //if not 1st-generation dragons
            require(_parent1Id != _parent2Id, "DragonCreator: parent dragons must be different");
            require(
                parent1Details.dragonType != DragonInfo.Types.Legendary 
                && parent2Details.dragonType != DragonInfo.Types.Legendary, 
                "DragonCreator: neither of the parent dragons can be of Legendary-type"
            );
            require(!dragonToken.isSiblings(_parent1Id, _parent2Id), "DragonCreator: the parent dragons must not be siblings");
            require(
                !dragonToken.isParent(_parent1Id, _parent2Id) && !dragonToken.isParent(_parent2Id, _parent1Id), 
                "DragonCreator: neither of the parent dragons must be a parent or child of another"
            );
        }

        DragonInfo.Details memory info = DragonInfo.Details({ 
            eggId: _eggId,
            parent1Id: _parent1Id,
            parent2Id: _parent2Id,
            generation: DragonInfo.calcGeneration(parent1Details.generation, parent2Details.generation),
            dragonType: (_dragonType == DragonInfo.Types.Unknown) ? DragonInfo.calcType(_genes) : _dragonType,
            strength: 0, //DragonInfo.calcStrength(_genes),
            genes: _genes
        });

        uint newDragonId = dragonToken.mint(to, info);
        
        emit DragonCreated(
            newDragonId, info.eggId,
            info.parent1Id, info.parent2Id, 
            info.generation, info.dragonType, 
            info.genes, _msgSender(), to);

        return newDragonId; 
    }
} 

// File: @openzeppelin/contracts/token/ERC721/IERC721.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "../../utils/introspection/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: @openzeppelin/contracts/token/ERC721/IERC721Receiver.sol



// SPDX-License-Identifier: MIT

pragma solidity ^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: @openzeppelin/contracts/token/ERC721/extensions/IERC721Metadata.sol



// SPDX-License-Identifier: MIT

pragma solidity ^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: @openzeppelin/contracts/utils/introspection/ERC165.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "./IERC165.sol";

/**
 * @dev Implementation of the {IERC165} interface.
 *
 * Contracts that want to implement ERC165 should inherit from this contract and override {supportsInterface} to check
 * for the additional interface id that will be supported. For example:
 *
 * ```solidity
 * function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
 *     return interfaceId == type(MyInterface).interfaceId || super.supportsInterface(interfaceId);
 * }
 * ```
 *
 * Alternatively, {ERC165Storage} provides an easier to use but more expensive implementation.
 */
abstract contract ERC165 is IERC165 {
    /**
     * @dev See {IERC165-supportsInterface}.
     */
    function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
        return interfaceId == type(IERC165).interfaceId;
    }
}

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



// SPDX-License-Identifier: MIT

pragma solidity ^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: contracts/DragonToken.sol



// SPDX-License-Identifier: GPL-3.0-only
pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
import "@openzeppelin/contracts/utils/Address.sol";
import "@openzeppelin/contracts/utils/Counters.sol";
import "./structs/DragonInfo.sol";
import "./access/BaseAccessControl.sol";

contract DragonToken is ERC721, BaseAccessControl {

    using Address for address;
    using Counters for Counters.Counter;
    
    Counters.Counter private _dragonIds;

    // Mapping token id to dragon details
    mapping(uint => uint) private _info;
    // Mapping token id to cid
    mapping(uint => string) private _cids;

    string private _defaultMetadataCid;
    address private _dragonCreator;

    constructor(string memory defaultCid, address accessControl) 
    ERC721("CryptoDragons", "CD")
    BaseAccessControl(accessControl) {        
        _defaultMetadataCid = defaultCid;
    }

    function tokenURI(uint tokenId) public view virtual override returns (string memory) {
        string memory cid = _cids[tokenId];
        return string(abi.encodePacked("ipfs://", (bytes(cid).length > 0) ? cid : defaultMetadataCid()));
    }

    function dragonCreatorAddress() public view returns(address) {
        return _dragonCreator;
    }

    function setDragonCreatorAddress(address newAddress) external onlyRole(CEO_ROLE) {
        address previousAddress = _dragonCreator;
        _dragonCreator = newAddress;
        emit AddressChanged("dragonCreator", previousAddress, newAddress);
    }

    function hasMetadataCid(uint tokenId) public view returns(bool) {
        return bytes(_cids[tokenId]).length > 0;
    }

    function setMetadataCid(uint tokenId, string calldata cid) external onlyRole(COO_ROLE) {
        require(bytes(cid).length >= 46, "DragonToken: bad CID");
        require(!hasMetadataCid(tokenId), "DragonToken: CID is already set");
        _cids[tokenId] = cid;
    }

    function defaultMetadataCid() public view returns (string memory){
        return _defaultMetadataCid;
    }

    function setDefaultMetadataCid(string calldata newDefaultCid) external onlyRole(COO_ROLE) {
        _defaultMetadataCid = newDefaultCid;
    }

    function dragonInfo(uint dragonId) public view returns (DragonInfo.Details memory) {
        return DragonInfo.getDetails(_info[dragonId]);
    }

    function strengthOf(uint dragonId) external view returns (uint) {
        DragonInfo.Details memory details = dragonInfo(dragonId);
        return details.strength > 0 ? details.strength : DragonInfo.calcStrength(details.genes);
    }

    function isSiblings(uint dragon1Id, uint dragon2Id) external view returns (bool) {
        DragonInfo.Details memory info1 = dragonInfo(dragon1Id);
        DragonInfo.Details memory info2 = dragonInfo(dragon2Id);
        return 
            (info1.generation > 1 && info2.generation > 1) && //the 1st generation of dragons doesn't have siblings
            (info1.parent1Id == info2.parent1Id || info1.parent1Id == info2.parent2Id || 
            info1.parent2Id == info2.parent1Id || info1.parent2Id == info2.parent2Id);
    }

    function isParent(uint dragon1Id, uint dragon2Id) external view returns (bool) {
        DragonInfo.Details memory info = dragonInfo(dragon1Id);
        return info.parent1Id == dragon2Id || info.parent2Id == dragon2Id;
    }

    function mint(address to, DragonInfo.Details calldata info) external returns (uint) {
        require(_msgSender() == dragonCreatorAddress(), "DragonToken: not enough privileges to call the method");
        
        _dragonIds.increment();
        uint newDragonId = uint(_dragonIds.current());
        
        _info[newDragonId] = DragonInfo.getValue(info);
        _mint(to, newDragonId);

        return newDragonId;
    }

    function setStrength(uint dragonId) external returns (uint) {
        DragonInfo.Details memory details = dragonInfo(dragonId);
        if (details.strength == 0) {
            details.strength = DragonInfo.calcStrength(details.genes);
            _info[dragonId] = DragonInfo.getValue(details);
        }
        return details.strength;
    }
}