// File: contracts/Staking.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import '@openzeppelin/contracts/utils/structs/EnumerableSet.sol';
import "@openzeppelin/contracts/utils/math/SafeMath.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import '@openzeppelin/contracts/token/ERC721/IERC721Receiver.sol';
import '@openzeppelin/contracts/token/ERC721/IERC721.sol';
import '@openzeppelin/contracts/token/ERC20/IERC20.sol';
import "@openzeppelin/contracts/utils/Strings.sol";
import "@openzeppelin/contracts/security/ReentrancyGuard.sol";

interface IERC20Mintable is IERC20 {
    function mint(address to, uint256 amount) external;
}

interface IBlocBurgers {
    function reservePrivate(uint256 reserveAmount, address reserveAddress) external;
    function transferOwnership(address newOwner) external;
    function ticketCounter() external view returns (uint256);
    function maxTotalSupply() external view returns (uint256);
}

contract Staking is IERC721Receiver, Ownable, ReentrancyGuard  {
    using EnumerableSet for EnumerableSet.UintSet;
    using SafeMath for uint256;

    event NftsRewarded(address indexed receiver, uint256 indexed amount);

    uint256 public rewardRate;
    uint256 public rewardRateBonusMultiplier;
    uint256 public nftMintPriceStage1;
    uint256 public nftMintPriceStage2;
    uint256 public nftMintPriceStage3;
    uint256 public nftMintPriceStage4;

    uint256 public lossEventMod; // set 10 for 10%
    uint256 public mintEventMod; // set 20 for 5%

    address public acceptedNftAddress;
    address public rewardTokenAddress;
    address public vaultAddress;

    mapping(address => mapping(uint256 => uint256)) public level1Timestamps;
    mapping(address => EnumerableSet.UintSet) private level1TokenIds;

    mapping(address => mapping(uint256 => uint256)) public level2Timestamps;
    mapping(address => EnumerableSet.UintSet) private level2TokenIds;

    uint256 public lastRandomSeed;

    constructor(
        address _acceptedNftAddress,
        address _rewardTokenAddress,
        address _vaultAddress,
        uint256 _rewardRate,
        uint256 _rewardRateBonusMultiplier,
        uint256 _nftMintPriceStage1,
        uint256 _nftMintPriceStage2,
        uint256 _nftMintPriceStage3,
        uint256 _nftMintPriceStage4,
        uint256 _mintEventMod,
        uint256 _lossEventMod
    ) {
        rewardRate = _rewardRate;
        rewardRateBonusMultiplier = _rewardRateBonusMultiplier;
        acceptedNftAddress = _acceptedNftAddress;
        rewardTokenAddress = _rewardTokenAddress;
        vaultAddress = _vaultAddress;
        nftMintPriceStage1 = _nftMintPriceStage1;
        nftMintPriceStage2 = _nftMintPriceStage2;
        nftMintPriceStage3 = _nftMintPriceStage3;
        nftMintPriceStage4 = _nftMintPriceStage4;
        mintEventMod = _mintEventMod;
        lossEventMod = _lossEventMod;
    }

    function stakeToLevel1(uint256[] calldata tokenIds) external {
        for (uint256 i; i < tokenIds.length; i++) {
            IERC721(acceptedNftAddress).safeTransferFrom(_msgSender(), address(this), tokenIds[i], '');
            level1TokenIds[_msgSender()].add(tokenIds[i]);
            level1Timestamps[_msgSender()][tokenIds[i]] = block.timestamp;
        }
    }

    function unstakeFromLevel1(uint256[] calldata tokenIds) public nonReentrant {
        uint256 totalRewards = 0;

        for (uint256 i; i < tokenIds.length; i++) {
            uint256 tokenId = tokenIds[i];

            require(level1TokenIds[_msgSender()].contains(tokenId), 'Data contains not staked token ID');

            uint256 lastTimestampForTokenId = level1Timestamps[_msgSender()][tokenId];
            if (lastTimestampForTokenId > 0) {
                level1TokenIds[_msgSender()].remove(tokenId);
                IERC721(acceptedNftAddress).safeTransferFrom(address(this), _msgSender(), tokenId, '');

                uint256 rewardForTokenId = block.timestamp.sub(lastTimestampForTokenId).mul(rewardRate);
                totalRewards = totalRewards.add(rewardForTokenId);
                level1Timestamps[_msgSender()][tokenId] = block.timestamp;
            }
        }

        if (totalRewards > 0) IERC20Mintable(rewardTokenAddress).mint(_msgSender(), totalRewards);
    }

    function level1TokenIdsForAddress(address ownerAddress) external view returns (uint256[] memory) {
        EnumerableSet.UintSet storage addressLevel1TokenIds = level1TokenIds[ownerAddress];
        uint256[] memory tokenIds = new uint256[](addressLevel1TokenIds.length());

        for (uint256 i; i < addressLevel1TokenIds.length(); i++) {
            tokenIds[i] = addressLevel1TokenIds.at(i);
        }

        return tokenIds;
    }

    function stakeToLevel2(uint256[] calldata tokenIds) external {
        for (uint256 i; i < tokenIds.length; i++) {
            IERC721(acceptedNftAddress).safeTransferFrom(_msgSender(), address(this), tokenIds[i], '');
            level2TokenIds[_msgSender()].add(tokenIds[i]);
            level2Timestamps[_msgSender()][tokenIds[i]] = block.timestamp;
        }
    }

    function unstakeFromLevel2(uint256[] calldata tokenIds) public nonReentrant {
        uint256 totalRewards = 0;
        uint256 totalReservations = 0;

        uint256 nftsReserved = IBlocBurgers(acceptedNftAddress).ticketCounter();
        uint256 maxTotalSupply = IBlocBurgers(acceptedNftAddress).maxTotalSupply();

        for (uint256 i; i < tokenIds.length; i++) {
            uint256 tokenId = tokenIds[i];

            require(level2TokenIds[_msgSender()].contains(tokenId), 'Data contains not staked token ID');

            uint256 lastTimestampForTokenId = level2Timestamps[_msgSender()][tokenId];
            if (lastTimestampForTokenId > 0) {
                level2TokenIds[_msgSender()].remove(tokenId);

                address nftReceiverAddress = _msgSender();

                uint256 randomNumber = getRandomNumber(tokenId);
                if (randomNumber % lossEventMod == 0) {
                    // 10% chance for nft lost
                    nftReceiverAddress = vaultAddress;
                } else if (randomNumber % mintEventMod == 0) {
                    // 5% chance for new burger, but check supply
                    if (nftsReserved.add(totalReservations.add(1)) <= maxTotalSupply) {
                        totalReservations = totalReservations.add(1);
                    }
                }

                lastRandomSeed = randomNumber;

                IERC721(acceptedNftAddress).safeTransferFrom(address(this), nftReceiverAddress, tokenId, '');

                uint256 rewardForTokenId = block.timestamp.sub(lastTimestampForTokenId).mul(rewardRate);
                uint256 increasedRewardForTokenId = rewardForTokenId.mul(rewardRateBonusMultiplier);
                totalRewards = totalRewards.add(increasedRewardForTokenId);
                level2Timestamps[_msgSender()][tokenId] = block.timestamp;
            }
        }

        if (totalReservations > 0) {
            IBlocBurgers(acceptedNftAddress).reservePrivate(totalReservations, _msgSender());
            emit NftsRewarded(_msgSender(), totalReservations);
        }

        if (totalRewards > 0) IERC20Mintable(rewardTokenAddress).mint(_msgSender(), totalRewards);
    }

    function level2TokenIdsForAddress(address ownerAddress) external view returns (uint256[] memory) {
        EnumerableSet.UintSet storage addressLevel2TokenIds = level2TokenIds[ownerAddress];
        uint256[] memory tokenIds = new uint256[](addressLevel2TokenIds.length());

        for (uint256 i; i < addressLevel2TokenIds.length(); i++) {
            tokenIds[i] = addressLevel2TokenIds.at(i);
        }

        return tokenIds;
    }

    function claimRewards() public nonReentrant {
        uint256 level1TokenIdsSetSize = level1TokenIds[_msgSender()].length();
        uint256 level2TokenIdsSetSize = level2TokenIds[_msgSender()].length();

        require(level1TokenIdsSetSize.add(level2TokenIdsSetSize) > 0, "Nothing staked");

        uint256 totalRewards = 0;

        for (uint256 i; i < level1TokenIdsSetSize; i++) {
            uint256 tokenId = level1TokenIds[_msgSender()].at(i);
            uint256 lastTimestampForTokenId = level1Timestamps[_msgSender()][tokenId];
            if (lastTimestampForTokenId > 0) {
                uint256 rewardForTokenId = block.timestamp.sub(lastTimestampForTokenId).mul(rewardRate);
                totalRewards = totalRewards.add(rewardForTokenId);
                level1Timestamps[_msgSender()][tokenId] = block.timestamp;
            }
        }

        for (uint256 i; i < level2TokenIdsSetSize; i++) {
            uint256 tokenId = level2TokenIds[_msgSender()].at(i);
            uint256 lastTimestampForTokenId = level2Timestamps[_msgSender()][tokenId];
            if (lastTimestampForTokenId > 0) {
                uint256 rewardForTokenId = block.timestamp.sub(lastTimestampForTokenId).mul(rewardRate);
                uint256 increasedRewardForTokenId = rewardForTokenId.mul(rewardRateBonusMultiplier);
                totalRewards = totalRewards.add(increasedRewardForTokenId);
                level2Timestamps[_msgSender()][tokenId] = block.timestamp;
            }
        }

        require(totalRewards > 0, "Nothing to claim");

        IERC20Mintable(rewardTokenAddress).mint(_msgSender(), totalRewards);
    }

    function calculateLevel1Rewards(address ownerAddress) public view returns (uint256) {
        uint256 totalRewards = 0;

        for (uint256 i; i < level1TokenIds[ownerAddress].length(); i++) {
            uint256 tokenId = level1TokenIds[ownerAddress].at(i);
            uint256 lastTimestampForTokenId = level1Timestamps[ownerAddress][tokenId];
            if (lastTimestampForTokenId > 0) {
                uint256 rewardForTokenId = block.timestamp.sub(lastTimestampForTokenId).mul(rewardRate);
                totalRewards = totalRewards.add(rewardForTokenId);
            }
        }

        return totalRewards;
    }

    function calculateLevel2Rewards(address ownerAddress) public view returns (uint256) {
        uint256 totalRewards = 0;

        for (uint256 i; i < level2TokenIds[ownerAddress].length(); i++) {
            uint256 tokenId = level2TokenIds[ownerAddress].at(i);
            uint256 lastTimestampForTokenId = level2Timestamps[ownerAddress][tokenId];
            if (lastTimestampForTokenId > 0) {
                uint256 rewardForTokenId = block.timestamp.sub(lastTimestampForTokenId).mul(rewardRate);
                uint256 increasedRewardForTokenId = rewardForTokenId.mul(rewardRateBonusMultiplier);
                totalRewards = totalRewards.add(increasedRewardForTokenId);
            }
        }

        return totalRewards;
    }

    function calculateTotalRewards(address ownerAddress) public view returns (uint256) {
        return calculateLevel1Rewards(ownerAddress).add(calculateLevel2Rewards(ownerAddress));
    }

    function mintNftWithRewardTokens(uint256 amount) public nonReentrant {
        require(amount > 0, "Wrong amount");

        uint256 nftsReserved = IBlocBurgers(acceptedNftAddress).ticketCounter();
        uint256 maxTotalSupply = IBlocBurgers(acceptedNftAddress).maxTotalSupply();
        require(nftsReserved.add(amount) <= maxTotalSupply, "Exceeds max supply");

        uint256 tokenBalance = IERC20Mintable(rewardTokenAddress).balanceOf(_msgSender());

        uint256 nftMintPrice = nftMintPriceStage4;
        if (nftsReserved <= 1000) {
            nftMintPrice = nftMintPriceStage1;
        } else if (nftsReserved <= 2000) {
            nftMintPrice = nftMintPriceStage2;
        } else if (nftsReserved <= 3000) {
            nftMintPrice = nftMintPriceStage3;
        }

        uint256 payableTokenAmount = nftMintPrice.mul(amount);
        require(payableTokenAmount <= tokenBalance, "Not enough token balance");

        uint256 allowance = IERC20Mintable(rewardTokenAddress).allowance(_msgSender(), address(this));
        require(payableTokenAmount <= allowance, "Not enough token allowance");

        IERC20Mintable(rewardTokenAddress).transferFrom(_msgSender(), vaultAddress, payableTokenAmount);
        IBlocBurgers(acceptedNftAddress).reservePrivate(amount, _msgSender());
    }

    function setAcceptedNftAddress(address _acceptedNftAddress) external onlyOwner {
        acceptedNftAddress = _acceptedNftAddress;
    }

    function setRewardTokenAddress(address _rewardTokenAddress) external onlyOwner {
        rewardTokenAddress = _rewardTokenAddress;
    }

    function setVaultAddress(address _vaultAddress) external onlyOwner {
        vaultAddress = _vaultAddress;
    }

    function setRewardRate(uint256 _rewardRate) external onlyOwner {
        rewardRate = _rewardRate;
    }

    function setRewardRateBonusMultiplier(uint256 _bonusMultiplier) external onlyOwner {
        rewardRateBonusMultiplier = _bonusMultiplier;
    }

    function setMintEventMod(uint256 _mintEventMod) external onlyOwner {
        mintEventMod = _mintEventMod;
    }

    function setLossEventMod(uint256 _lossEventMod) external onlyOwner {
        lossEventMod = _lossEventMod;
    }

    function setNftMintPriceStage1(uint256 _nftMintPrice) external onlyOwner {
        nftMintPriceStage1 = _nftMintPrice;
    }

    function setNftMintPriceStage2(uint256 _nftMintPrice) external onlyOwner {
        nftMintPriceStage2 = _nftMintPrice;
    }

    function setNftMintPriceStage3(uint256 _nftMintPrice) external onlyOwner {
        nftMintPriceStage3 = _nftMintPrice;
    }

    function setNftMintPriceStage4(uint256 _nftMintPrice) external onlyOwner {
        nftMintPriceStage4 = _nftMintPrice;
    }

    function setAcceptedNftContractOwnership(address _newOwner) external onlyOwner {
        IBlocBurgers(acceptedNftAddress).transferOwnership(_newOwner);
    }

    function getRandomNumber(uint256 seed) internal view returns (uint256) {
        return uint256(keccak256(abi.encodePacked(
            tx.origin,
            blockhash(block.number - 1),
            block.timestamp,
            seed,
            lastRandomSeed
        ))) & 0xFFFF;
    }

    function onERC721Received(address, address, uint256, bytes calldata) external pure override returns (bytes4) {
        return IERC721Receiver.onERC721Received.selector;
    }
}

// File: @openzeppelin/contracts/utils/structs/EnumerableSet.sol



// SPDX-License-Identifier: MIT

pragma solidity ^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;

            if (lastIndex != toDeleteIndex) {
                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] = valueIndex; // Replace lastvalue's index to valueIndex
            }

            // 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) {
        return set._values[index];
    }

    /**
     * @dev Return the entire set in an array
     *
     * WARNING: This operation will copy the entire storage to memory, which can be quite expensive. This is designed
     * to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that
     * this function has an unbounded cost, and using it as part of a state-changing function may render the function
     * uncallable if the set grows to a point where copying to memory consumes too much gas to fit in a block.
     */
    function _values(Set storage set) private view returns (bytes32[] memory) {
        return set._values;
    }

    // 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);
    }

    /**
     * @dev Return the entire set in an array
     *
     * WARNING: This operation will copy the entire storage to memory, which can be quite expensive. This is designed
     * to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that
     * this function has an unbounded cost, and using it as part of a state-changing function may render the function
     * uncallable if the set grows to a point where copying to memory consumes too much gas to fit in a block.
     */
    function values(Bytes32Set storage set) internal view returns (bytes32[] memory) {
        return _values(set._inner);
    }

    // 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))));
    }

    /**
     * @dev Return the entire set in an array
     *
     * WARNING: This operation will copy the entire storage to memory, which can be quite expensive. This is designed
     * to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that
     * this function has an unbounded cost, and using it as part of a state-changing function may render the function
     * uncallable if the set grows to a point where copying to memory consumes too much gas to fit in a block.
     */
    function values(AddressSet storage set) internal view returns (address[] memory) {
        bytes32[] memory store = _values(set._inner);
        address[] memory result;

        assembly {
            result := store
        }

        return result;
    }

    // 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));
    }

    /**
     * @dev Return the entire set in an array
     *
     * WARNING: This operation will copy the entire storage to memory, which can be quite expensive. This is designed
     * to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that
     * this function has an unbounded cost, and using it as part of a state-changing function may render the function
     * uncallable if the set grows to a point where copying to memory consumes too much gas to fit in a block.
     */
    function values(UintSet storage set) internal view returns (uint256[] memory) {
        bytes32[] memory store = _values(set._inner);
        uint256[] memory result;

        assembly {
            result := store
        }

        return result;
    }
}

// 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/access/Ownable.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "../utils/Context.sol";

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

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

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor() {
        _setOwner(_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 {
        _setOwner(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");
        _setOwner(newOwner);
    }

    function _setOwner(address newOwner) private {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}

// 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/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/ERC20/IERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity ^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: @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: @openzeppelin/contracts/security/ReentrancyGuard.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

/**
 * @dev Contract module that helps prevent reentrant calls to a function.
 *
 * Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
 * available, which can be applied to functions to make sure there are no nested
 * (reentrant) calls to them.
 *
 * Note that because there is a single `nonReentrant` guard, functions marked as
 * `nonReentrant` may not call one another. This can be worked around by making
 * those functions `private`, and then adding `external` `nonReentrant` entry
 * points to them.
 *
 * TIP: If you would like to learn more about reentrancy and alternative ways
 * to protect against it, check out our blog post
 * https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
 */
abstract contract ReentrancyGuard {
    // Booleans are more expensive than uint256 or any type that takes up a full
    // word because each write operation emits an extra SLOAD to first read the
    // slot's contents, replace the bits taken up by the boolean, and then write
    // back. This is the compiler's defense against contract upgrades and
    // pointer aliasing, and it cannot be disabled.

    // The values being non-zero value makes deployment a bit more expensive,
    // but in exchange the refund on every call to nonReentrant will be lower in
    // amount. Since refunds are capped to a percentage of the total
    // transaction's gas, it is best to keep them low in cases like this one, to
    // increase the likelihood of the full refund coming into effect.
    uint256 private constant _NOT_ENTERED = 1;
    uint256 private constant _ENTERED = 2;

    uint256 private _status;

    constructor() {
        _status = _NOT_ENTERED;
    }

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * Calling a `nonReentrant` function from another `nonReentrant`
     * function is not supported. It is possible to prevent this from happening
     * by making the `nonReentrant` function external, and make it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        // On the first call to nonReentrant, _notEntered will be true
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

        // Any calls to nonReentrant after this point will fail
        _status = _ENTERED;

        _;

        // By storing the original value once again, a refund is triggered (see
        // https://eips.ethereum.org/EIPS/eip-2200)
        _status = _NOT_ENTERED;
    }
}

// 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/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);
}