// File: contracts/SecretNFTSociety.sol



// SPDX-License-Identifier: MIT
// https://secretnftsociety.com

// It was all a meme.
//
// Secret NFT Society NFTs are authentic pieces of
// on-chain artwork with unique combinations of color,
// style, and fun collectible "Cool S" cool points.
//
// Stats and other utility are intentionally omitted for others to interpret.
// Cool S points have no inherent utility or value, they're just cool.

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC721/extensions/ERC721Enumerable.sol";
import "@openzeppelin/contracts/token/ERC721/IERC721.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/utils/Counters.sol";
import "@openzeppelin/contracts/utils/Strings.sol";
import './Base64.sol';
import './CoolS.sol';

string constant DESCRIPTION = "The Secret NFT Society has a fixed total supply of 42,069 collectibles associated with varying levels of Cool S points. Stats and other utility are intentionally omitted for others to interpret. Cool S points have no inherent utility or value, they're just cool.";

contract SecretNFTSociety is ERC721Enumerable, Ownable {
  /**
   * Token IDs counter.
   *
   * Provides an auto-incremented ID for each token minted.
   */
  using Counters for Counters.Counter;
  Counters.Counter private _tokenIDs;

  address private _S;
  uint private _generation;
  uint private _freq;
  uint private constant _totalSupply = 42069;

  mapping(uint => uint) private _generations;
  mapping(uint => bool) private _leaders;
  mapping(address => uint) private _claimable;
  string[] private _tags = [
    "Dope",
    "Chill",
    "Noice",
    "Fire",
    "Swag",
    "Yeet",
    "Hype",
    "Lit",
    "Fam",
    "Vibes",
    "Based",
    "Whale",
    "Ape"
  ];

  /**
   * Base fee
   *
   * Defines the base fee for the artwork.
   */
  uint private _baseFee;

  /**
   * Contract URI
   *
   * Defines the contract metadata URI.
   */
  string private _contractURI;

  /**
   * Constructor to deploy the contract.
   *
   * Sets the initial settings for the contract.
   */
  constructor(
    string memory _name,
    string memory _symbol,
    string memory __contractURI,
    uint __freq,
    uint __baseFee
  ) ERC721(_name, _symbol) {
    _contractURI = __contractURI;
    _freq = __freq;
    _baseFee = __baseFee;
  }

  /**
   * Contract metadata URI
   *
   * Provides the URI for the contract metadata.
   */
  function contractURI() public view returns (string memory) {
    return string(abi.encodePacked('ipfs://', _contractURI));
  }

  /**
   * Get the mint fee.
   *
   * Fee to mint.
   */
  function mintFee() public view returns (uint) {
    return _baseFee;
  }

  /**
   * Get image
   *
   * Returns the image for a tokenID.
   */
  function getImage(uint _tokenID) public view returns (string memory) {
    uint r1 = uint256(keccak256(abi.encode(_tokenID))) % 360;
    uint r2 = (r1 + 180) % 360;
    uint r3 = uint256(keccak256(abi.encode(_tokenID, 2))) % 360;
    uint r4 = (r3 + 180) % 360;

    bytes memory out = abi.encodePacked(
      '<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100"><style>.',
      _leaders[_tokenID] ? 'g1' : 'f2',
      '{fill:url(#g1)}.g2{fill:url(#g2)}.f1{fill:#000}.f2{fill:#fff}</style><linearGradient id="g1" gradientTransform="rotate(45)"><stop offset="50%" stop-color="hsl(',
      Strings.toString(r1),
      ', 100%, 50%)"/><stop offset="100%" stop-color="hsl(',
      Strings.toString(r2),
      ', 100%, 50%)"/></linearGradient><linearGradient id="g2" gradientTransform="rotate(45)"><stop offset="50%" stop-color="hsl(',
      Strings.toString(r3),
      ', 100%, 50%)"/><stop offset="100%" stop-color="hsl(',
      Strings.toString(r4),
      ', 100%, 50%)"/></linearGradient>');
    out = abi.encodePacked(
      out,
      '<rect width="100" height="100" fill="url(#',
      _leaders[_tokenID] ? 'g1' : 'f2',
      ')"/><polygon clasas="f1" points="31.2,50 50,12.5 68.8,50 "/><path class="',
      _leaders[_tokenID] ? 'g2' : 'f2',
      '" d="M50,48.4l-5.1-5v-6.1l2-2.4l-2-2.4v-6.1l5.1-5l5,5v6.1l-0.2,0.2l-1.7,2.2l1.9,2.4l0,6.1L50,48.4z M46.4,42.9 l3.6,3.6l3.6-3.6l0-5l-4.3-5.3v-5.8h1.4V32l1.5,1.8l1.4-1.8v-5L50,23.5L46.4,27v5l4.3,5.3v5.8h-1.4v-5.3l-1.5-1.8l-1.5,1.8V42.9z"/><polygon class="f1" points="12.5,87.5 31.2,50 50,87.5 "/><path class="',
      _leaders[_tokenID] ? 'g2' : 'f2',
      '" d="M31.3,85.9l-5.1-5v-6.1l2-2.4l-2-2.4v-6.1l5.1-5l5,5v6.1l-0.2,0.2l-1.7,2.2l1.9,2.4l0,6.1L31.3,85.9z M27.6,80.4l3.6,3.6l3.6-3.6l0-5L30.5,70v-5.8H32v5.3l1.5,1.8l1.4-1.8v-5L31.3,61l-3.6,3.6v5l4.3,5.3v5.8h-1.4v-5.3l-1.5-1.8 l-1.5,1.8V80.4z"/><polygon class="f1" points="50,87.5 68.8,50 87.5,87.5 "/><path class="',
      _leaders[_tokenID] ? 'g2' : 'f2',
      '" d="M68.8,85.9l-5.1-5v-6.1l2-2.4l-2-2.4v-6.1l5.1-5l5,5v6.1l-0.2,0.2l-1.7,2.2l1.9,2.4l0,6.1L68.8,85.9z M65.1,80.4l3.6,3.6l3.6-3.6l0-5L68,70v-5.8h1.4v5.3l1.5,1.8l1.4-1.8v-5L68.8,61l-3.6,3.6v5l4.3,5.3v5.8H68v-5.3l-1.5-1.8l-1.5,1.8 V80.4z"/><text x="50%" y="61%" dominant-baseline="middle" text-anchor="middle" style="font-weight:700;font-size:4.5px">MEMBER</text><text x="50%" y="68%" dominant-baseline="middle" text-anchor="middle" style="font-weight:700;font-size:4px">',
      Strings.toString(_tokenID),
      '</text></svg>'
    );
    return string(abi.encodePacked("data:image/svg+xml;base64,",Base64.encode(bytes(out))));
  }

  /**
   * Token URI
   * Returns a base-64 encoded SVG.
   */
  function tokenURI(uint256 _tokenID) override public view returns (string memory) {
    require(_tokenID <= _tokenIDs.current(), "Token doesn't exist.");

    string memory json = Base64.encode(bytes(string(abi.encodePacked(
      '{"name":"Secret NFT Society #',
      Strings.toString(_tokenID),
      '","description":"',
      DESCRIPTION,
      '","image":"',
      getImage(_tokenID),
      '","attributes":[{"trait_type":"Generation","value":"',
      Strings.toString(_generations[_tokenID]),
      '"}',
      _leaders[_tokenID]
        ? string(abi.encodePacked(',{"value":"',_tags[_generations[_tokenID] % _tags.length],'"}'))
        : '',
      ']}'
    ))));

    return string(abi.encodePacked('data:application/json;base64,', json));
  }

  /**
   * Mint To
   *
   * Requires payment of _mintFee.
   */
  function mintTo(address _to) public payable returns (uint) {
    require(_tokenIDs.current() < _totalSupply, "Max supply reached.");

    uint fee = mintFee();
    if (fee > 0) {
      require(msg.value >= fee, "Requires minimum fee.");

      payable(owner()).transfer(fee);

      uint change = msg.value - fee;
      if (change > 0) payable(msg.sender).transfer(change);
    }

    if (_leaders[_tokenIDs.current()]) {
      _generation++;
    }

    _tokenIDs.increment();
    uint tokenID = _tokenIDs.current();
    _generations[tokenID] = _generation;
    _mint(_to, tokenID);
    if (tokenID % _freq == 0) _increaseCollectibleGeneration();
    _claimable[ownerOf(_tokenIDs.current())] += 42069 ether * 10 * (_generation+1);

    return tokenID;
  }

  /**
   * Claimable
   *
   * Returns the amount claimable of cool points.
   */
  function claimable(address _claimer) public view returns (uint) {
    return _claimable[_claimer];
  }

  /**
   * Claim
   *
   * Mints S tokens.
   */
  function claim() public {
    uint amt = _claimable[msg.sender];
    if (amt == 0) return;

    CoolSV2 s = CoolSV2(_S);
    s.mint(msg.sender, amt);
    s.mint(owner(), amt);

    _claimable[msg.sender] = 0;
  }

  /**
   * Mint
   *
   * Requires payment of _mintFee.
   */
  function mint() public payable returns (uint) {
    return mintTo(msg.sender);
  }

  /**
   * Increment generation.
   *
   * Increases collectibles generation number.
   */
  function _increaseCollectibleGeneration() private {
    uint256 levelUp = uint256(keccak256(abi.encode(_tokenIDs.current(), block.timestamp, block.difficulty, blockhash(block.number))));
    _leaders[_tokenIDs.current()] = (levelUp % _freq) == 0;
  }

  /**
   * Admin function: Update base fee.
   *
   * Updates the base fee scalar.
   */
  function adminUpdateBaseFee(uint _newBaseFee) public onlyOwner {
    _baseFee = _newBaseFee;
  }

  /**
   * Admin function: Update frequency
   *
   * Updates the generation frequency.
   */
  function adminUpdateFreq(uint _newFreq) public onlyOwner {
    _freq = _newFreq;
  }

  /**
   * Admin function: Update S token address.
   *
   * Sets the Cool S token address a single time only.
   */
  function adminUpdateSAddress(address _newS) public onlyOwner {
    if (_S == address(0)) _S = _newS;
  }
}

// File: @openzeppelin/contracts/token/ERC721/extensions/ERC721Enumerable.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "../ERC721.sol";
import "./IERC721Enumerable.sol";

/**
 * @dev This implements an optional extension of {ERC721} defined in the EIP that adds
 * enumerability of all the token ids in the contract as well as all token ids owned by each
 * account.
 */
abstract contract ERC721Enumerable is ERC721, IERC721Enumerable {
    // Mapping from owner to list of owned token IDs
    mapping(address => mapping(uint256 => uint256)) private _ownedTokens;

    // Mapping from token ID to index of the owner tokens list
    mapping(uint256 => uint256) private _ownedTokensIndex;

    // Array with all token ids, used for enumeration
    uint256[] private _allTokens;

    // Mapping from token id to position in the allTokens array
    mapping(uint256 => uint256) private _allTokensIndex;

    /**
     * @dev See {IERC165-supportsInterface}.
     */
    function supportsInterface(bytes4 interfaceId) public view virtual override(IERC165, ERC721) returns (bool) {
        return interfaceId == type(IERC721Enumerable).interfaceId || super.supportsInterface(interfaceId);
    }

    /**
     * @dev See {IERC721Enumerable-tokenOfOwnerByIndex}.
     */
    function tokenOfOwnerByIndex(address owner, uint256 index) public view virtual override returns (uint256) {
        require(index < ERC721.balanceOf(owner), "ERC721Enumerable: owner index out of bounds");
        return _ownedTokens[owner][index];
    }

    /**
     * @dev See {IERC721Enumerable-totalSupply}.
     */
    function totalSupply() public view virtual override returns (uint256) {
        return _allTokens.length;
    }

    /**
     * @dev See {IERC721Enumerable-tokenByIndex}.
     */
    function tokenByIndex(uint256 index) public view virtual override returns (uint256) {
        require(index < ERC721Enumerable.totalSupply(), "ERC721Enumerable: global index out of bounds");
        return _allTokens[index];
    }

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

        if (from == address(0)) {
            _addTokenToAllTokensEnumeration(tokenId);
        } else if (from != to) {
            _removeTokenFromOwnerEnumeration(from, tokenId);
        }
        if (to == address(0)) {
            _removeTokenFromAllTokensEnumeration(tokenId);
        } else if (to != from) {
            _addTokenToOwnerEnumeration(to, tokenId);
        }
    }

    /**
     * @dev Private function to add a token to this extension's ownership-tracking data structures.
     * @param to address representing the new owner of the given token ID
     * @param tokenId uint256 ID of the token to be added to the tokens list of the given address
     */
    function _addTokenToOwnerEnumeration(address to, uint256 tokenId) private {
        uint256 length = ERC721.balanceOf(to);
        _ownedTokens[to][length] = tokenId;
        _ownedTokensIndex[tokenId] = length;
    }

    /**
     * @dev Private function to add a token to this extension's token tracking data structures.
     * @param tokenId uint256 ID of the token to be added to the tokens list
     */
    function _addTokenToAllTokensEnumeration(uint256 tokenId) private {
        _allTokensIndex[tokenId] = _allTokens.length;
        _allTokens.push(tokenId);
    }

    /**
     * @dev Private function to remove a token from this extension's ownership-tracking data structures. Note that
     * while the token is not assigned a new owner, the `_ownedTokensIndex` mapping is _not_ updated: this allows for
     * gas optimizations e.g. when performing a transfer operation (avoiding double writes).
     * This has O(1) time complexity, but alters the order of the _ownedTokens array.
     * @param from address representing the previous owner of the given token ID
     * @param tokenId uint256 ID of the token to be removed from the tokens list of the given address
     */
    function _removeTokenFromOwnerEnumeration(address from, uint256 tokenId) private {
        // To prevent a gap in from's tokens array, we store the last token in the index of the token to delete, and
        // then delete the last slot (swap and pop).

        uint256 lastTokenIndex = ERC721.balanceOf(from) - 1;
        uint256 tokenIndex = _ownedTokensIndex[tokenId];

        // When the token to delete is the last token, the swap operation is unnecessary
        if (tokenIndex != lastTokenIndex) {
            uint256 lastTokenId = _ownedTokens[from][lastTokenIndex];

            _ownedTokens[from][tokenIndex] = lastTokenId; // Move the last token to the slot of the to-delete token
            _ownedTokensIndex[lastTokenId] = tokenIndex; // Update the moved token's index
        }

        // This also deletes the contents at the last position of the array
        delete _ownedTokensIndex[tokenId];
        delete _ownedTokens[from][lastTokenIndex];
    }

    /**
     * @dev Private function to remove a token from this extension's token tracking data structures.
     * This has O(1) time complexity, but alters the order of the _allTokens array.
     * @param tokenId uint256 ID of the token to be removed from the tokens list
     */
    function _removeTokenFromAllTokensEnumeration(uint256 tokenId) private {
        // To prevent a gap in the tokens array, we store the last token in the index of the token to delete, and
        // then delete the last slot (swap and pop).

        uint256 lastTokenIndex = _allTokens.length - 1;
        uint256 tokenIndex = _allTokensIndex[tokenId];

        // When the token to delete is the last token, the swap operation is unnecessary. However, since this occurs so
        // rarely (when the last minted token is burnt) that we still do the swap here to avoid the gas cost of adding
        // an 'if' statement (like in _removeTokenFromOwnerEnumeration)
        uint256 lastTokenId = _allTokens[lastTokenIndex];

        _allTokens[tokenIndex] = lastTokenId; // Move the last token to the slot of the to-delete token
        _allTokensIndex[lastTokenId] = tokenIndex; // Update the moved token's index

        // This also deletes the contents at the last position of the array
        delete _allTokensIndex[tokenId];
        _allTokens.pop();
    }
}

// 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/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/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: @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/Base64.sol



pragma solidity ^0.8.0;

/// [MIT License]
/// @title Base64
/// @notice Provides a function for encoding some bytes in base64
/// @author Brecht Devos <brecht@loopring.org>
library Base64 {
    bytes internal constant TABLE = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

    /// @notice Encodes some bytes to the base64 representation
    function encode(bytes memory data) internal pure returns (string memory) {
        uint256 len = data.length;
        if (len == 0) return "";

        // multiply by 4/3 rounded up
        uint256 encodedLen = 4 * ((len + 2) / 3);

        // Add some extra buffer at the end
        bytes memory result = new bytes(encodedLen + 32);

        bytes memory table = TABLE;

        assembly {
            let tablePtr := add(table, 1)
            let resultPtr := add(result, 32)

            for {
                let i := 0
            } lt(i, len) {

            } {
                i := add(i, 3)
                let input := and(mload(add(data, i)), 0xffffff)

                let out := mload(add(tablePtr, and(shr(18, input), 0x3F)))
                out := shl(8, out)
                out := add(out, and(mload(add(tablePtr, and(shr(12, input), 0x3F))), 0xFF))
                out := shl(8, out)
                out := add(out, and(mload(add(tablePtr, and(shr(6, input), 0x3F))), 0xFF))
                out := shl(8, out)
                out := add(out, and(mload(add(tablePtr, and(input, 0x3F))), 0xFF))
                out := shl(224, out)

                mstore(resultPtr, out)

                resultPtr := add(resultPtr, 4)
            }

            switch mod(len, 3)
            case 1 {
                mstore(sub(resultPtr, 2), shl(240, 0x3d3d))
            }
            case 2 {
                mstore(sub(resultPtr, 1), shl(248, 0x3d))
            }

            mstore(result, encodedLen)
        }

        return string(result);
    }
}
// File: contracts/CoolS.sol



// SPDX-License-Identifier: MIT
// https://secretnftsociety.com

// It was all a meme.
//
// Cool S points have no inherent utility
// or value. They can be exchanged / renamed
// for other types of meaningless "cool points."
//
// V2 adds token verification + exchange burn.

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import "./BokkyPooBahsRedBlackTreeLibrary.sol";

contract CoolSToken is ERC20 {
  address private _minter;
  event NewToken(address indexed _address, string indexed _name, string indexed _symbol);

  constructor(
    string memory _name,
    string memory _symbol,
    address __minter
  ) ERC20(_name, _symbol) {
    _minter = __minter;
  }

  /* Increment tokens. */
  function mint(address _to, uint256 _amount) public virtual {
    require(msg.sender == _minter, "Unauthorized.");
    require(_amount > 0, "Amount required.");
    _mint(_to, _amount);
  }

  /* Decrement tokens. */
  function burn(address _to, uint256 _amount) public {
    require(msg.sender == _minter, "Unauthorized.");
    require(_amount > 0, "Amount required.");
    _burn(_to, _amount);
  }
}

contract CoolSV2 is CoolSToken {
  using BokkyPooBahsRedBlackTreeLibrary for BokkyPooBahsRedBlackTreeLibrary.Tree;
  BokkyPooBahsRedBlackTreeLibrary.Tree tree;

  address private _minter;
  address[] _tokens;
  mapping(uint => uint[]) _values;
  mapping(address => uint) _keys;
  mapping(uint => uint) _keyIndices;

  constructor(
    string memory _name,
    string memory _symbol,
    address __minter
  ) CoolSToken(_name, _symbol, __minter) {
    _tokens.push(address(this));
    uint key = _tokens.length;
    _keys[address(this)] = key;
    _minter = __minter;
  }

  /* Get total tokens created. */
  function totalTokens() public view returns (uint) {
    return _tokens.length;
  }

  /* Get token address at index. */
  function getToken(uint _idx) public view returns (address) {
    return _tokens[_idx];
  }

  /* BST queries */
  function top() public view returns (uint) {
    // Token key with most points
    return tree.last();
  }

  function next(uint _idx) public view returns (uint) {
    // Next key with more points than provided index.
    return tree.prev(_idx);
  }

  function prev(uint _idx) public view returns (uint) {
    // Prev key with less points than provided index.
    return tree.next(_idx);
  }

  // Gets the number of tokens at a supply level.
  function totalTokensWithSupply(uint _totalSupply) public view returns (uint) {
    return _values[_totalSupply].length;
  }

  // Gets the token at the total supply index.
  function getTokenAtSupplyIndex(uint _totalSupply, uint _idx) public view returns (uint) {
    require(_values[_totalSupply].length > _idx && _values[_totalSupply][_idx] > 0, "Not found.");
    return _values[_totalSupply][_idx] - 1;
  }

  /* Create a new Cool S backed ERC20 token. */
  function newToken(string memory _name, string memory _symbol) public returns (address) {
    CoolSToken child = new CoolSToken(_name, _symbol, address(this));
    address childAddress = address(child);
    emit NewToken(childAddress, _name, _symbol);
    _tokens.push(childAddress);
    _keys[childAddress] = _tokens.length;

    return childAddress;
  }

  /* Sort top tokens in BST. */
  function _updateValues(uint _supplyBefore, uint _supplyAfter, uint _key) private {
    uint idx = _keyIndices[_key];
    if (idx > 0) {
      if (_values[_supplyBefore].length > 1) {
        _values[_supplyBefore][idx-1] = _values[_supplyBefore].length - 1;
      }
      if (_values[_supplyBefore].length > 0) {
        _values[_supplyBefore].pop();
      }
      if (_values[_supplyBefore].length == 0 && tree.exists(_supplyBefore)) tree.remove(_supplyBefore);
    }
    if (_supplyAfter > 0) {
      _values[_supplyAfter].push(_key);
      _keyIndices[_key] = _values[_supplyAfter].length;
      if (!tree.exists(_supplyAfter)) tree.insert(_supplyAfter);
    }
  }

  /* Mint Cool S for artwork's "cool points" score. */
  function mint(address _to, uint256 _amount) public override {
    require(msg.sender == _minter, "Unauthorized.");
    uint supplyCoolSBefore = totalSupply();
    uint supplyCoolSAfter = supplyCoolSBefore + _amount;
    uint keyCoolS = _keys[address(this)];
    _mint(_to, _amount);
    _updateValues(supplyCoolSBefore, supplyCoolSAfter, keyCoolS);
  }

  /* Exchange Cool S for another type of "cool points" (burns 0.5%.) */
  function mintToken(address _to, address _token, uint _amount) public {
    require(_keys[_token] > 0, "Unsupported token.");

    CoolSToken t = CoolSToken(_token);
    uint supplyCoolSBefore = totalSupply();
    uint supplyCoolSAfter = supplyCoolSBefore - _amount;
    uint keyCoolS = _keys[address(this)];
    _burn(msg.sender, _amount);
    _updateValues(supplyCoolSBefore, supplyCoolSAfter, keyCoolS);

    uint supplyTokenBefore = t.totalSupply();
    uint supplyTokenAfter = supplyTokenBefore + _amount;
    uint keyToken = _keys[_token];
    uint burnAmt = _amount / 2000;
    t.mint(_to, _amount - burnAmt);
    _updateValues(supplyTokenBefore, supplyTokenAfter, keyToken);
  }

  /* Return points back to standard Cool S points (burns 0.5%). */
  function returnToken(address _to, address _token, uint _amount) public {
    require(_keys[_token] > 0, "Unsupported token.");

    CoolSToken t = CoolSToken(_token);
    uint supplyTokenBefore = t.totalSupply();
    uint supplyTokenAfter = supplyTokenBefore - _amount;
    uint keyToken = _keys[_token];
    t.burn(msg.sender, _amount);
    _updateValues(supplyTokenBefore, supplyTokenAfter, keyToken);

    uint supplyCoolSBefore = totalSupply();
    uint supplyCoolSAfter = supplyCoolSBefore + _amount;
    uint keyCoolS = _keys[address(this)];
    uint burnAmt = _amount / 2000;
    _mint(_to, _amount - burnAmt);
    _updateValues(supplyCoolSBefore, supplyCoolSAfter, keyCoolS);
  }
}

// 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/token/ERC721/extensions/IERC721Enumerable.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "../IERC721.sol";

/**
 * @title ERC-721 Non-Fungible Token Standard, optional enumeration extension
 * @dev See https://eips.ethereum.org/EIPS/eip-721
 */
interface IERC721Enumerable is IERC721 {
    /**
     * @dev Returns the total amount of tokens stored by the contract.
     */
    function totalSupply() external view returns (uint256);

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

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

// File: @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/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: @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/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: @openzeppelin/contracts/token/ERC20/ERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "./IERC20.sol";
import "./extensions/IERC20Metadata.sol";
import "../../utils/Context.sol";

/**
 * @dev Implementation of the {IERC20} interface.
 *
 * This implementation is agnostic to the way tokens are created. This means
 * that a supply mechanism has to be added in a derived contract using {_mint}.
 * For a generic mechanism see {ERC20PresetMinterPauser}.
 *
 * TIP: For a detailed writeup see our guide
 * https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How
 * to implement supply mechanisms].
 *
 * We have followed general OpenZeppelin Contracts guidelines: functions revert
 * instead returning `false` on failure. This behavior is nonetheless
 * conventional and does not conflict with the expectations of ERC20
 * applications.
 *
 * Additionally, an {Approval} event is emitted on calls to {transferFrom}.
 * This allows applications to reconstruct the allowance for all accounts just
 * by listening to said events. Other implementations of the EIP may not emit
 * these events, as it isn't required by the specification.
 *
 * Finally, the non-standard {decreaseAllowance} and {increaseAllowance}
 * functions have been added to mitigate the well-known issues around setting
 * allowances. See {IERC20-approve}.
 */
contract ERC20 is Context, IERC20, IERC20Metadata {
    mapping(address => uint256) private _balances;

    mapping(address => mapping(address => uint256)) private _allowances;

    uint256 private _totalSupply;

    string private _name;
    string private _symbol;

    /**
     * @dev Sets the values for {name} and {symbol}.
     *
     * The default value of {decimals} is 18. To select a different value for
     * {decimals} you should overload it.
     *
     * All two of these values are immutable: they can only be set once during
     * construction.
     */
    constructor(string memory name_, string memory symbol_) {
        _name = name_;
        _symbol = symbol_;
    }

    /**
     * @dev Returns the name of the token.
     */
    function name() public view virtual override returns (string memory) {
        return _name;
    }

    /**
     * @dev Returns the symbol of the token, usually a shorter version of the
     * name.
     */
    function symbol() public view virtual override returns (string memory) {
        return _symbol;
    }

    /**
     * @dev Returns the number of decimals used to get its user representation.
     * For example, if `decimals` equals `2`, a balance of `505` tokens should
     * be displayed to a user as `5.05` (`505 / 10 ** 2`).
     *
     * Tokens usually opt for a value of 18, imitating the relationship between
     * Ether and Wei. This is the value {ERC20} uses, unless this function is
     * overridden;
     *
     * NOTE: This information is only used for _display_ purposes: it in
     * no way affects any of the arithmetic of the contract, including
     * {IERC20-balanceOf} and {IERC20-transfer}.
     */
    function decimals() public view virtual override returns (uint8) {
        return 18;
    }

    /**
     * @dev See {IERC20-totalSupply}.
     */
    function totalSupply() public view virtual override returns (uint256) {
        return _totalSupply;
    }

    /**
     * @dev See {IERC20-balanceOf}.
     */
    function balanceOf(address account) public view virtual override returns (uint256) {
        return _balances[account];
    }

    /**
     * @dev See {IERC20-transfer}.
     *
     * Requirements:
     *
     * - `recipient` cannot be the zero address.
     * - the caller must have a balance of at least `amount`.
     */
    function transfer(address recipient, uint256 amount) public virtual override returns (bool) {
        _transfer(_msgSender(), recipient, amount);
        return true;
    }

    /**
     * @dev See {IERC20-allowance}.
     */
    function allowance(address owner, address spender) public view virtual override returns (uint256) {
        return _allowances[owner][spender];
    }

    /**
     * @dev See {IERC20-approve}.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 amount) public virtual override returns (bool) {
        _approve(_msgSender(), spender, amount);
        return true;
    }

    /**
     * @dev See {IERC20-transferFrom}.
     *
     * Emits an {Approval} event indicating the updated allowance. This is not
     * required by the EIP. See the note at the beginning of {ERC20}.
     *
     * Requirements:
     *
     * - `sender` and `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     * - the caller must have allowance for ``sender``'s tokens of at least
     * `amount`.
     */
    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) public virtual override returns (bool) {
        _transfer(sender, recipient, amount);

        uint256 currentAllowance = _allowances[sender][_msgSender()];
        require(currentAllowance >= amount, "ERC20: transfer amount exceeds allowance");
        unchecked {
            _approve(sender, _msgSender(), currentAllowance - amount);
        }

        return true;
    }

    /**
     * @dev Atomically increases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender] + addedValue);
        return true;
    }

    /**
     * @dev Atomically decreases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `spender` must have allowance for the caller of at least
     * `subtractedValue`.
     */
    function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {
        uint256 currentAllowance = _allowances[_msgSender()][spender];
        require(currentAllowance >= subtractedValue, "ERC20: decreased allowance below zero");
        unchecked {
            _approve(_msgSender(), spender, currentAllowance - subtractedValue);
        }

        return true;
    }

    /**
     * @dev Moves `amount` of tokens from `sender` to `recipient`.
     *
     * This internal function is equivalent to {transfer}, and can be used to
     * e.g. implement automatic token fees, slashing mechanisms, etc.
     *
     * Emits a {Transfer} event.
     *
     * Requirements:
     *
     * - `sender` cannot be the zero address.
     * - `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     */
    function _transfer(
        address sender,
        address recipient,
        uint256 amount
    ) internal virtual {
        require(sender != address(0), "ERC20: transfer from the zero address");
        require(recipient != address(0), "ERC20: transfer to the zero address");

        _beforeTokenTransfer(sender, recipient, amount);

        uint256 senderBalance = _balances[sender];
        require(senderBalance >= amount, "ERC20: transfer amount exceeds balance");
        unchecked {
            _balances[sender] = senderBalance - amount;
        }
        _balances[recipient] += amount;

        emit Transfer(sender, recipient, amount);

        _afterTokenTransfer(sender, recipient, amount);
    }

    /** @dev Creates `amount` tokens and assigns them to `account`, increasing
     * the total supply.
     *
     * Emits a {Transfer} event with `from` set to the zero address.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     */
    function _mint(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: mint to the zero address");

        _beforeTokenTransfer(address(0), account, amount);

        _totalSupply += amount;
        _balances[account] += amount;
        emit Transfer(address(0), account, amount);

        _afterTokenTransfer(address(0), account, amount);
    }

    /**
     * @dev Destroys `amount` tokens from `account`, reducing the
     * total supply.
     *
     * Emits a {Transfer} event with `to` set to the zero address.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     * - `account` must have at least `amount` tokens.
     */
    function _burn(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: burn from the zero address");

        _beforeTokenTransfer(account, address(0), amount);

        uint256 accountBalance = _balances[account];
        require(accountBalance >= amount, "ERC20: burn amount exceeds balance");
        unchecked {
            _balances[account] = accountBalance - amount;
        }
        _totalSupply -= amount;

        emit Transfer(account, address(0), amount);

        _afterTokenTransfer(account, address(0), amount);
    }

    /**
     * @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens.
     *
     * This internal function is equivalent to `approve`, and can be used to
     * e.g. set automatic allowances for certain subsystems, etc.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `owner` cannot be the zero address.
     * - `spender` cannot be the zero address.
     */
    function _approve(
        address owner,
        address spender,
        uint256 amount
    ) internal virtual {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");

        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }

    /**
     * @dev Hook that is called before any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * will be transferred to `to`.
     * - when `from` is zero, `amount` tokens will be minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens 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 amount
    ) internal virtual {}

    /**
     * @dev Hook that is called after any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * has been transferred to `to`.
     * - when `from` is zero, `amount` tokens have been minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens have been 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 _afterTokenTransfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {}
}

// File: contracts/BokkyPooBahsRedBlackTreeLibrary.sol



pragma solidity ^0.8.0;

// ----------------------------------------------------------------------------
// BokkyPooBah's Red-Black Tree Library v1.0-pre-release-a
//
// A Solidity Red-Black Tree binary search library to store and access a sorted
// list of unsigned integer data. The Red-Black algorithm rebalances the binary
// search tree, resulting in O(log n) insert, remove and search time (and ~gas)
//
// https://github.com/bokkypoobah/BokkyPooBahsRedBlackTreeLibrary
//
//
// Enjoy. (c) BokkyPooBah / Bok Consulting Pty Ltd 2020. The MIT Licence.
// ----------------------------------------------------------------------------
library BokkyPooBahsRedBlackTreeLibrary {

    struct Node {
        uint parent;
        uint left;
        uint right;
        bool red;
    }

    struct Tree {
        uint root;
        mapping(uint => Node) nodes;
    }

    uint private constant EMPTY = 0;

    function first(Tree storage self) internal view returns (uint _key) {
        _key = self.root;
        if (_key != EMPTY) {
            while (self.nodes[_key].left != EMPTY) {
                _key = self.nodes[_key].left;
            }
        }
    }
    function last(Tree storage self) internal view returns (uint _key) {
        _key = self.root;
        if (_key != EMPTY) {
            while (self.nodes[_key].right != EMPTY) {
                _key = self.nodes[_key].right;
            }
        }
    }
    function next(Tree storage self, uint target) internal view returns (uint cursor) {
        require(target != EMPTY);
        if (self.nodes[target].right != EMPTY) {
            cursor = treeMinimum(self, self.nodes[target].right);
        } else {
            cursor = self.nodes[target].parent;
            while (cursor != EMPTY && target == self.nodes[cursor].right) {
                target = cursor;
                cursor = self.nodes[cursor].parent;
            }
        }
    }
    function prev(Tree storage self, uint target) internal view returns (uint cursor) {
        require(target != EMPTY);
        if (self.nodes[target].left != EMPTY) {
            cursor = treeMaximum(self, self.nodes[target].left);
        } else {
            cursor = self.nodes[target].parent;
            while (cursor != EMPTY && target == self.nodes[cursor].left) {
                target = cursor;
                cursor = self.nodes[cursor].parent;
            }
        }
    }
    function exists(Tree storage self, uint key) internal view returns (bool) {
        return (key != EMPTY) && ((key == self.root) || (self.nodes[key].parent != EMPTY));
    }
    function isEmpty(uint key) internal pure returns (bool) {
        return key == EMPTY;
    }
    function getEmpty() internal pure returns (uint) {
        return EMPTY;
    }
    function getNode(Tree storage self, uint key) internal view returns (uint _returnKey, uint _parent, uint _left, uint _right, bool _red) {
        require(exists(self, key));
        return(key, self.nodes[key].parent, self.nodes[key].left, self.nodes[key].right, self.nodes[key].red);
    }

    function insert(Tree storage self, uint key) internal {
        require(key != EMPTY);
        require(!exists(self, key));
        uint cursor = EMPTY;
        uint probe = self.root;
        while (probe != EMPTY) {
            cursor = probe;
            if (key < probe) {
                probe = self.nodes[probe].left;
            } else {
                probe = self.nodes[probe].right;
            }
        }
        self.nodes[key] = Node({parent: cursor, left: EMPTY, right: EMPTY, red: true});
        if (cursor == EMPTY) {
            self.root = key;
        } else if (key < cursor) {
            self.nodes[cursor].left = key;
        } else {
            self.nodes[cursor].right = key;
        }
        insertFixup(self, key);
    }
    function remove(Tree storage self, uint key) internal {
        require(key != EMPTY);
        require(exists(self, key));
        uint probe;
        uint cursor;
        if (self.nodes[key].left == EMPTY || self.nodes[key].right == EMPTY) {
            cursor = key;
        } else {
            cursor = self.nodes[key].right;
            while (self.nodes[cursor].left != EMPTY) {
                cursor = self.nodes[cursor].left;
            }
        }
        if (self.nodes[cursor].left != EMPTY) {
            probe = self.nodes[cursor].left;
        } else {
            probe = self.nodes[cursor].right;
        }
        uint yParent = self.nodes[cursor].parent;
        self.nodes[probe].parent = yParent;
        if (yParent != EMPTY) {
            if (cursor == self.nodes[yParent].left) {
                self.nodes[yParent].left = probe;
            } else {
                self.nodes[yParent].right = probe;
            }
        } else {
            self.root = probe;
        }
        bool doFixup = !self.nodes[cursor].red;
        if (cursor != key) {
            replaceParent(self, cursor, key);
            self.nodes[cursor].left = self.nodes[key].left;
            self.nodes[self.nodes[cursor].left].parent = cursor;
            self.nodes[cursor].right = self.nodes[key].right;
            self.nodes[self.nodes[cursor].right].parent = cursor;
            self.nodes[cursor].red = self.nodes[key].red;
            (cursor, key) = (key, cursor);
        }
        if (doFixup) {
            removeFixup(self, probe);
        }
        delete self.nodes[cursor];
    }

    function treeMinimum(Tree storage self, uint key) private view returns (uint) {
        while (self.nodes[key].left != EMPTY) {
            key = self.nodes[key].left;
        }
        return key;
    }
    function treeMaximum(Tree storage self, uint key) private view returns (uint) {
        while (self.nodes[key].right != EMPTY) {
            key = self.nodes[key].right;
        }
        return key;
    }

    function rotateLeft(Tree storage self, uint key) private {
        uint cursor = self.nodes[key].right;
        uint keyParent = self.nodes[key].parent;
        uint cursorLeft = self.nodes[cursor].left;
        self.nodes[key].right = cursorLeft;
        if (cursorLeft != EMPTY) {
            self.nodes[cursorLeft].parent = key;
        }
        self.nodes[cursor].parent = keyParent;
        if (keyParent == EMPTY) {
            self.root = cursor;
        } else if (key == self.nodes[keyParent].left) {
            self.nodes[keyParent].left = cursor;
        } else {
            self.nodes[keyParent].right = cursor;
        }
        self.nodes[cursor].left = key;
        self.nodes[key].parent = cursor;
    }
    function rotateRight(Tree storage self, uint key) private {
        uint cursor = self.nodes[key].left;
        uint keyParent = self.nodes[key].parent;
        uint cursorRight = self.nodes[cursor].right;
        self.nodes[key].left = cursorRight;
        if (cursorRight != EMPTY) {
            self.nodes[cursorRight].parent = key;
        }
        self.nodes[cursor].parent = keyParent;
        if (keyParent == EMPTY) {
            self.root = cursor;
        } else if (key == self.nodes[keyParent].right) {
            self.nodes[keyParent].right = cursor;
        } else {
            self.nodes[keyParent].left = cursor;
        }
        self.nodes[cursor].right = key;
        self.nodes[key].parent = cursor;
    }

    function insertFixup(Tree storage self, uint key) private {
        uint cursor;
        while (key != self.root && self.nodes[self.nodes[key].parent].red) {
            uint keyParent = self.nodes[key].parent;
            if (keyParent == self.nodes[self.nodes[keyParent].parent].left) {
                cursor = self.nodes[self.nodes[keyParent].parent].right;
                if (self.nodes[cursor].red) {
                    self.nodes[keyParent].red = false;
                    self.nodes[cursor].red = false;
                    self.nodes[self.nodes[keyParent].parent].red = true;
                    key = self.nodes[keyParent].parent;
                } else {
                    if (key == self.nodes[keyParent].right) {
                      key = keyParent;
                      rotateLeft(self, key);
                    }
                    keyParent = self.nodes[key].parent;
                    self.nodes[keyParent].red = false;
                    self.nodes[self.nodes[keyParent].parent].red = true;
                    rotateRight(self, self.nodes[keyParent].parent);
                }
            } else {
                cursor = self.nodes[self.nodes[keyParent].parent].left;
                if (self.nodes[cursor].red) {
                    self.nodes[keyParent].red = false;
                    self.nodes[cursor].red = false;
                    self.nodes[self.nodes[keyParent].parent].red = true;
                    key = self.nodes[keyParent].parent;
                } else {
                    if (key == self.nodes[keyParent].left) {
                      key = keyParent;
                      rotateRight(self, key);
                    }
                    keyParent = self.nodes[key].parent;
                    self.nodes[keyParent].red = false;
                    self.nodes[self.nodes[keyParent].parent].red = true;
                    rotateLeft(self, self.nodes[keyParent].parent);
                }
            }
        }
        self.nodes[self.root].red = false;
    }

    function replaceParent(Tree storage self, uint a, uint b) private {
        uint bParent = self.nodes[b].parent;
        self.nodes[a].parent = bParent;
        if (bParent == EMPTY) {
            self.root = a;
        } else {
            if (b == self.nodes[bParent].left) {
                self.nodes[bParent].left = a;
            } else {
                self.nodes[bParent].right = a;
            }
        }
    }
    function removeFixup(Tree storage self, uint key) private {
        uint cursor;
        while (key != self.root && !self.nodes[key].red) {
            uint keyParent = self.nodes[key].parent;
            if (key == self.nodes[keyParent].left) {
                cursor = self.nodes[keyParent].right;
                if (self.nodes[cursor].red) {
                    self.nodes[cursor].red = false;
                    self.nodes[keyParent].red = true;
                    rotateLeft(self, keyParent);
                    cursor = self.nodes[keyParent].right;
                }
                if (!self.nodes[self.nodes[cursor].left].red && !self.nodes[self.nodes[cursor].right].red) {
                    self.nodes[cursor].red = true;
                    key = keyParent;
                } else {
                    if (!self.nodes[self.nodes[cursor].right].red) {
                        self.nodes[self.nodes[cursor].left].red = false;
                        self.nodes[cursor].red = true;
                        rotateRight(self, cursor);
                        cursor = self.nodes[keyParent].right;
                    }
                    self.nodes[cursor].red = self.nodes[keyParent].red;
                    self.nodes[keyParent].red = false;
                    self.nodes[self.nodes[cursor].right].red = false;
                    rotateLeft(self, keyParent);
                    key = self.root;
                }
            } else {
                cursor = self.nodes[keyParent].left;
                if (self.nodes[cursor].red) {
                    self.nodes[cursor].red = false;
                    self.nodes[keyParent].red = true;
                    rotateRight(self, keyParent);
                    cursor = self.nodes[keyParent].left;
                }
                if (!self.nodes[self.nodes[cursor].right].red && !self.nodes[self.nodes[cursor].left].red) {
                    self.nodes[cursor].red = true;
                    key = keyParent;
                } else {
                    if (!self.nodes[self.nodes[cursor].left].red) {
                        self.nodes[self.nodes[cursor].right].red = false;
                        self.nodes[cursor].red = true;
                        rotateLeft(self, cursor);
                        cursor = self.nodes[keyParent].left;
                    }
                    self.nodes[cursor].red = self.nodes[keyParent].red;
                    self.nodes[keyParent].red = false;
                    self.nodes[self.nodes[cursor].left].red = false;
                    rotateRight(self, keyParent);
                    key = self.root;
                }
            }
        }
        self.nodes[key].red = false;
    }
}
// ----------------------------------------------------------------------------
// End - BokkyPooBah's Red-Black Tree Library
// ----------------------------------------------------------------------------
// 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/token/ERC20/extensions/IERC20Metadata.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "../IERC20.sol";

/**
 * @dev Interface for the optional metadata functions from the ERC20 standard.
 *
 * _Available since v4.1._
 */
interface IERC20Metadata is IERC20 {
    /**
     * @dev Returns the name of the token.
     */
    function name() external view returns (string memory);

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

    /**
     * @dev Returns the decimals places of the token.
     */
    function decimals() external view returns (uint8);
}