// File: /src/contracts/OG.sol



/*

     OOOOOOOOO                  GGGGGGGGGGGGG
   OO:::::::::OO             GGG::::::::::::G
 OO:::::::::::::OO         GG:::::::::::::::G
O:::::::OOO:::::::O       G:::::GGGGGGGG::::G
O::::::O   O::::::O      G:::::G       GGGGGG
O:::::O     O:::::O     G:::::G              
O:::::O     O:::::O     G:::::G              
O:::::O     O:::::O     G:::::G    GGGGGGGGGG
O:::::O     O:::::O     G:::::G    G::::::::G
O:::::O     O:::::O     G:::::G    GGGGG::::G
O:::::O     O:::::O     G:::::G        G::::G
O::::::O   O::::::O      G:::::G       G::::G
O:::::::OOO:::::::O       G:::::GGGGGGGG::::G
 OO:::::::::::::OO         GG:::::::::::::::G
   OO:::::::::OO             GGG::::::GGG:::G
     OOOOOOOOO                  GGGGGG   GGGG
     
*/

// SPDX-License-Identifier: MIT

pragma solidity 0.8.0;

import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
import "@openzeppelin/contracts/token/ERC721/extensions/ERC721Enumerable.sol";
import '@openzeppelin/contracts/token/ERC20/ERC20.sol';
import '@openzeppelin/contracts/access/Ownable.sol';
import '@openzeppelin/contracts/utils/Strings.sol';
import 'base64-sol/base64.sol';
import './interfaces/GotTokenInterface.sol';
import './interfaces/OGColorInterface.sol';
import './libs/Customizer.sol';
import './libs/Digits.sol';
import './ERC/HumbleERC721Enumerable.sol';

/**
 * @title OG
 * @author nfttank.eth
 * OG is a free, vector based NFT that is rendered on-chain. OG tokens represent numbers from 0-10000 and are licensed
 * under a public domain CC0 license. Feel free to use your OG tokens in any way you want.
 * Thank you for being a number with me.
 */
contract OG is HumbleERC721Enumerable, Ownable {

    mapping(address => string) private _supportedSlugs;
    mapping(string => address) private _trustedContracts;
    address[] private _supportedCollections;
    bool private _paused;
    uint16 private _unlockSupply;
    uint256 private _currentId = 12; // increases, starting with 13
    uint256 private _currentDozenId = 13; // decreases, starting with 12

    constructor() ERC721("OG", "OG") Ownable() {
        _trustedContracts["gottoken"] = address(0);
        _trustedContracts["ogcolor"] = address(0);
        _paused = true;
        _unlockSupply = 5000;
    }

    function setPaused(bool paused) external onlyOwner {
        _paused = paused;
    }

    function setUnlockSupply(uint16 unlockSupply) external onlyOwner {
         _unlockSupply = unlockSupply;
    }

    function addSupportedCollection(address contractAddress) external onlyOwner {
         _supportedCollections.push(contractAddress);
    }

    function clearSupportedCollections() external onlyOwner {
         delete _supportedCollections;
    }
    
    function setSupportedCollectionSlug(address contractAddress, string calldata svgSlug) external onlyOwner {
        _supportedSlugs[contractAddress] = svgSlug;
    }

    function setSupportedCollectionSlugBase64(address contractAddress, string calldata base64EncodedSvgSlug) external onlyOwner {
        _supportedSlugs[contractAddress] = string(Base64.decode(base64EncodedSvgSlug));
    }

    function setTrustedContractAddresses(address gotTokenAddress, address ogColorAddress) external onlyOwner {
        _trustedContracts["gottoken"] = gotTokenAddress;
        _trustedContracts["ogcolor"] = ogColorAddress;
    }
    
    function renderSvg(uint256 tokenId) public virtual view returns (string memory) {
        require(tokenId >= 0 && tokenId <= 9999, "Token Id invalid");
        
        (string memory back, string memory frame, string memory digit, string memory slug)
            = Customizer.getColors(this, _trustedContracts["ogcolor"], tokenId);
        
        address supportedCollection = Customizer.getOwnedSupportedCollection(this, _trustedContracts["gottoken"], _supportedCollections, tokenId);
        bool hasCollection = supportedCollection != address(0);

        string[8] memory parts;

        parts[0] = "<svg xmlns='http://www.w3.org/2000/svg' xmlns:xlink='http://www.w3.org/1999/xlink' width='1000' height='1000' viewBox='0 0 1000 1000'>";
        
        // OGColor delivers whole definitions like <linearGradient id='back'><stop stop-color='#FFAAFF'/></linearGradient>
        parts[1] = string(abi.encodePacked("<defs>", back, frame, digit, slug, "</defs>"));
        parts[2] = "<mask id='_mask'>";
        
        if (hasCollection)
            parts[3] = "<path id='path-0' d='M 504.28 105.614 C 804.145 105.541 991.639 430.111 841.768 689.836 C 691.898 949.563 317.067 949.655 167.072 690 C 26.805 447.185 181.324 140.169 459.907 108.16 Z' style='fill: none;'/>";
        else
            parts[3] = "";
            
        // don't apply colors on this string, this should be kept white
        parts[4] = string(abi.encodePacked("<circle cx='500' cy='500' r='450' fill='#ffffff' stroke='none' /></mask><circle cx='500' cy='500' r='450' fill='url(#back)' mask='url(#_mask)' stroke-width='130' stroke='url(#frame)' stroke-linejoin='miter' stroke-linecap='square' stroke-miterlimit='3' />"));

        parts[5] = Digits.generateDigits(tokenId);
          
        if (hasCollection)  
            parts[6] = _supportedSlugs[supportedCollection];
        else
            parts[6] = "";
            
        parts[7] = "</svg>";
        
        return string(abi.encodePacked(parts[0], parts[1], parts[2], parts[3], parts[4], parts[5], parts[6], parts[7]));
    }
    
    function tokenURI(uint256 tokenId) override public view returns (string memory) {
        require(tokenId >= 0 && tokenId <= 9999, "Token Id invalid");
    
        string memory colorAttributes = Customizer.getColorAttributes(this, _trustedContracts["ogcolor"], tokenId);

        string memory attributes = string(abi.encodePacked(
            '"attributes": [',
            colorAttributes, 
            bytes(colorAttributes).length > 0 ? ', ' : '',
            '{ "trait_type": "Tier", "value": "', tier(tokenId), '" }'
            ']'));
        
        string memory json = Base64.encode(bytes(string(abi.encodePacked('{"name": "OG #', Strings.toString(tokenId), '", "description": "OG by Tank", ', attributes, ', "image": "data:image/svg+xml;base64,', Base64.encode(bytes(renderSvg(tokenId))), '"}'))));
        return string(abi.encodePacked('data:application/json;base64,', json));
    }

    function tier(uint256 tokenId) public pure returns (string memory) {
        require(tokenId >= 0 && tokenId <= 9999, "Token Id invalid");

        if (tokenId == 42 || tokenId == 69 || tokenId == 420 || tokenId == 666 || tokenId == 1337)
            return 'Meme';
        else if (tokenId == 33 || tokenId == 888 || tokenId == 2745 || tokenId == 3178 || tokenId == 4156 || tokenId == 6529)
            return 'Honorary';
        else if (tokenId > 0 && tokenId < 13)
            return 'OG Dozen';
        else if (tokenId < 1)
            return 'Glitch';

        return 'OG';
    }

    function mint(uint16 count) public {

        require(!_paused, "Minting is paused");
        require(_currentId < 9999, "Maximum amount of sequential mints reached");

        address sender = _msgSender();
        
        if (sender != owner()) {
            require(count > 0 && count <= 10, "Minting is limited to max. 10 per wallet");
            require(balanceOf(sender) + count <= 10, "Minting is limited to max. 10 per wallet");
        }            

        for (uint16 i = 0; i < count; i++) {
            uint256 newId = ++_currentId;
            if (newId <= 9999) {
                _safeMint(sender, newId);
            }
        }
    }

    function mintOgDozen() public {

        require(!_paused, "Minting is paused");
        require(canMintOgDozen(), "Unlock supply has not yet been reached to mint OG dozen tokens.");

        require(_currentDozenId > 0+1 && _currentDozenId <= 12+1, "No OG dozen tokens available anymore");

        address sender = _msgSender();
        
        if (sender != owner())
            require(balanceOf(sender) + 1 <= 10, "Minting is limited to max. 10 per wallet");

        _safeMint(sender, --_currentDozenId);
    }

    function exists(uint256 tokenId) external view returns (bool) {
        return _exists(tokenId);
    }

    function canMintOgDozen() public view returns (bool) {
        return totalSupply() >= _unlockSupply && !_exists(1);
    }
}
// File: /src/contracts/libs/Digits.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.8.0;

import '@openzeppelin/contracts/utils/Strings.sol';

library Digits {
 
    uint16 constant private _digitheight = 3435; // needs div /10 // 4er-2061 * 0.6 3er evtl *.8

    // needs to be prefixed to be like: "<path transform='translate(%x%, %y%) scale(%x%, %y%)' ";
    function getDigitPath(uint256 tokenId) private pure returns (string memory) {
        require(tokenId >= 0 && tokenId <= 9, "Token Id invalid");
        
        if (tokenId == 0)
            return "d=' M 143.151 343.5 C 230.072 343.5 286.302 276.215 286.302 171.752 C 286.302 67.004 230.357 0 143.151 0 C 55.939 0 0 67.004 0 171.752 C 0 276.215 56.225 343.5 143.151 343.5 Z  M 143.151 265.588 C 108.697 265.588 89.651 232 89.651 171.752 C 89.651 111.5 108.697 77.912 143.151 77.912 C 177.319 77.912 196.646 111.785 196.646 172.033 C 196.646 232.285 177.605 265.588 143.151 265.588 Z ' fill='url(#digit)' />";
    
        if (tokenId == 1)
            return "d=' M 0 0 L 0 77.843 L 50.921 77.843 L 50.921 343.5 L 143.459 343.5 L 143.459 0 L 0 0 Z  M 0 343.5 L 0 265.657 L 50.921 265.657 L 50.921 0 L 143.459 0 L 143.459 343.5 L 0 343.5 Z  M 194.38 343.5 L 194.38 265.657 L 143.459 265.657 L 143.459 0 L 50.921 0 L 50.921 343.5 L 194.38 343.5 Z ' fill='url(#digit)' />";
            
        if (tokenId == 2)
            return "d=' M 156.002 264.058 C 227.642 181.076 243.236 148.719 243.236 106.57 C 243.236 43.685 194.177 0 123.127 0 C 49.79 0 5.4 44.768 5.4 112.494 L 5.4 118.689 L 93.943 118.689 L 93.943 112.217 C 93.943 92.054 105.407 79.371 124.209 79.371 C 141.365 79.371 153.333 91.55 153.333 109.713 C 153.333 138.469 134.772 164.157 0 323.111 L 0 343.5 L 249.124 343.5 L 249.124 264.058 L 156.002 264.058 Z ' fill='url(#digit)' />";
            
        if (tokenId == 3)
            return "d=' M 171.407 123.294 L 238.794 15.423 L 238.794 0 L 8.426 0 L 8.426 76.525 L 121.108 76.525 L 66.438 166.404 L 66.438 185.113 L 120.215 185.113 C 146.341 185.113 163.016 200.335 163.016 224.875 C 163.016 249.411 146.927 266.303 123.976 266.303 C 101.899 266.303 87.183 250.577 86.173 226.91 L 0 226.91 C 2.019 296.408 51.616 343.5 123.764 343.5 C 197.427 343.5 250.34 294.605 250.34 226.329 C 250.34 174.335 219.544 135.37 171.412 123.294 L 171.407 123.294 Z ' fill='url(#digit)' />";
            
        if (tokenId == 4)
            return "d=' M 284.201 204.819 L 253.162 204.819 L 253.162 129.166 L 191.27 129.166 L 171.125 204.819 L 116.186 204.819 L 201.265 0 L 110.039 0 L 0 264.986 L 0 281.784 L 164.901 281.784 L 164.901 343.5 L 253.167 343.5 L 253.167 281.784 L 284.206 281.784 L 284.201 204.819 Z ' fill='url(#digit)' />";
            
        if (tokenId == 5)
           return "d=' M 123.333 114.832 L 92.093 114.832 L 96.324 76.524 L 226.119 76.524 L 226.119 0 L 27.075 0 L 8.32 175.014 L 16.887 186.105 L 121.374 186.105 C 145.99 186.105 162.882 202.568 162.882 226.679 C 162.882 249.412 146.788 266.304 124.711 266.304 C 102.13 266.304 86.111 249.998 86.111 227.204 L 0 227.204 C 0 295.328 51.555 343.5 124.711 343.5 C 197.929 343.5 250.205 294.884 250.205 226.684 C 250.205 160.858 198.514 114.842 123.338 114.842 L 123.333 114.832 Z ' fill='url(#digit)' />";
            
        if (tokenId == 6)
            return "d=' M 152.692 109.295 C 145.089 109.295 137.718 109.82 130.479 110.926 C 152.626 73.91 174.971 37.046 197.073 0 L 100.112 0 L 38.399 104.029 C 10.279 151.122 0 185.189 0 219.61 C 0 292.874 54.433 343.5 133.664 343.5 C 212.451 343.5 266.743 292.798 266.743 219.181 C 266.743 154.287 219.882 109.295 152.692 109.295 L 152.692 109.295 Z  M 133.371 266.379 C 106.17 266.379 86.466 247.255 86.466 219.181 C 86.466 190.818 106.17 171.482 133.371 171.482 C 160.86 171.482 180.277 190.818 180.277 219.181 C 180.277 247.255 160.86 266.379 133.371 266.379 Z ' fill='url(#digit)' />";
            
        if (tokenId == 7)
            return "d=' M 0 0 L 0 80.487 L 141.739 80.487 L 36.736 343.5 L 133.629 343.5 L 263.798 13.399 L 263.798 0 L 0 0 Z ' fill='url(#digit)' />";
            
        if (tokenId == 8)
            return "d=' M 215.493 162.467 C 238.458 144.232 250.107 121.726 250.107 95.201 C 250.107 38.495 201.849 0 129.696 0 C 57.538 0 8.999 38.781 8.999 95.206 C 8.999 121.431 20.6 143.858 43.47 162.413 C 14.098 181.052 0 206.218 0 239.137 C 0 301.409 52.199 343.5 129.415 343.5 C 206.632 343.5 259.116 301.123 259.116 239.132 C 259.116 206.435 244.782 181.289 215.498 162.462 L 215.493 162.467 Z  M 129.701 65.119 C 151.882 65.119 166.96 78.926 166.96 97.866 C 166.96 116.81 151.882 130.617 129.701 130.617 C 107.52 130.617 92.162 116.81 92.162 97.866 C 92.162 78.926 107.52 65.119 129.701 65.119 Z  M 129.701 275.347 C 103.22 275.347 85.679 259.363 85.679 236.403 C 85.679 213.444 103.22 197.455 129.701 197.455 C 156.182 197.455 173.437 213.444 173.437 236.403 C 173.437 259.363 156.182 275.347 129.701 275.347 Z ' fill='url(#digit)' />";
            
        if (tokenId == 9)
            return "d=' M 132.772 0 C 54.167 0 0 50.585 0 124.033 C 0 188.777 46.752 233.666 113.788 233.666 C 121.369 233.666 128.722 233.142 135.94 232.039 C 113.808 269.035 91.268 306.63 69.217 343.5 L 165.955 343.5 L 227.818 238.919 C 255.657 191.935 266.128 157.946 266.128 123.605 C 266.128 50.51 211.821 0 132.772 0 L 132.772 0 Z  M 133.064 172.201 C 104.188 172.201 83.945 152.617 83.945 124.033 C 83.945 95.731 104.188 76.364 133.064 76.364 C 161.654 76.364 182.184 95.731 182.184 124.033 C 182.184 152.617 161.654 172.201 133.064 172.201 Z ' fill='url(#digit)' />";

        return "";
    }

    // needs div /10
    function getDigitWidth(uint256 tokenId) public pure returns (uint16) {
        require(tokenId >= 0 && tokenId <= 9, "Token Id invalid");

        if (tokenId == 0)
            return 2863;
    
        if (tokenId == 1)
            return 1944;
            
        if (tokenId == 2)
            return 2491;
            
        if (tokenId == 3)
            return 2503;
            
        if (tokenId == 4)
            return 2842;
            
        if (tokenId == 5)
            return 2502;
            
        if (tokenId == 6)
            return 2667;
            
        if (tokenId == 7)
            return 2638;
            
        if (tokenId == 8)
            return 2591;
            
        if (tokenId == 9)
            return 2661;
            
        return 0;
    }

    function getScaleFactor(uint256 numberCharCount) private pure returns (uint16) {
        
        if (numberCharCount == 1)
            return 9;

        if (numberCharCount == 2)
            return 7;
        
        return 6;
    }

    function getDigitBounds(uint16 number, uint256 numberDigitCount, uint16 scaleFactorTimesTen, uint16 currentIndex) public pure returns (uint16 x, uint16 y) {

        uint16 height = (_digitheight /* is x10 */ * scaleFactorTimesTen) / 100;
        uint16 width = (getDigitWidth(number) /* is x10 */ * scaleFactorTimesTen) / 100;
        uint16 distanceX = 50;
        uint16 distanceY = 40;
        uint16 alignWidth = (3000 /* is x10 */ * scaleFactorTimesTen) / 100;
        uint16 deltaX = (alignWidth - width) / 2;

        if (numberDigitCount == 1) {
            x = (1000 - width) / 2;
            y = (1000 - height) / 2;
        }        
        else if (numberDigitCount == 2) {
            distanceX = 30;
            x = (currentIndex == 0) ? 500 - width - deltaX - distanceX : 501 + deltaX + distanceX;
            y = (1000 - height) / 2;
        }
        else if (numberDigitCount == 3) {
            if (currentIndex == 0)
                x = (1000 - width) / 2;
            else
                x = (currentIndex == 1) ? 500 - width - deltaX - distanceX : 501 + deltaX + distanceX;
            y = (currentIndex == 0) ? 500 - height - distanceY : 501 + distanceY;
            y -= 15; // -15 to the top because with three chars it seems like the text is too far away from the top while mathematically it would be correct 
        }
        else if (numberDigitCount == 4) {
            x = (currentIndex == 0 || currentIndex == 2) ? 500 - width - deltaX - distanceX : 501 + deltaX + distanceX;
            y = (currentIndex == 0 || currentIndex == 1) ? 500 - height - distanceY : 501 + distanceY;
        }

        // adjust '1' a few pixels because it looks off when perfectly centered
        if (number == 1) {
            if (numberDigitCount == 2) {
                if (currentIndex == 0) {
                    x -= 7;
                } else if (currentIndex == 1) {
                    x += 7;
                }
            } else if (numberDigitCount == 3) {
                if (currentIndex == 1 || currentIndex == 2) {
                    x += 7;
                }
            } else if (numberDigitCount == 4) {
                x += 8;
            }
        }
    }

    function generateDigits(uint256 tokenId) public pure returns (string memory) {
        require(tokenId >= 0 && tokenId <= 9999, "Token Id invalid");
        
        bytes memory stringBytes = bytes(Strings.toString(tokenId));
        
        string[] memory parts = new string[](stringBytes.length);
        
        for (uint16 i = 0; i < stringBytes.length; i++)
        {
            uint16 number = uint16(uint8(stringBytes[i])) - 48; // charIndex - 48 is the numeric value

            uint16 scaleFactor = getScaleFactor(stringBytes.length);
            (uint16 rectX, uint16 rectY) = getDigitBounds(number, stringBytes.length, scaleFactor, i);

            string memory scaleFactorString = string(abi.encodePacked("0.", Strings.toString(scaleFactor)));
            parts[i] = string(abi.encodePacked("<path transform='translate(", Strings.toString(rectX), ", ", Strings.toString(rectY), ") scale(", scaleFactorString, ", ", scaleFactorString, ")' ", getDigitPath(number)));
        }

        if (stringBytes.length == 1) 
            return parts[0];        
        if (stringBytes.length == 2) 
            return string(abi.encodePacked(parts[0], parts[1]));
        else if (stringBytes.length == 3)
            return string(abi.encodePacked(parts[0], parts[1], parts[2]));
        else
            return string(abi.encodePacked(parts[0], parts[1], parts[2], parts[3]));
    }
}
// File: /src/contracts/libs/Customizer.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.8.0;

import "@openzeppelin/contracts/token/ERC721/IERC721.sol";
import "../interfaces/GotTokenInterface.sol";
import "../interfaces/OGColorInterface.sol";

library Customizer {
    
    function safeOwnerOf(IERC721 callingContract, uint256 tokenId) public view returns (address) {
        
        address ownerOfToken = address(0);
                
        try callingContract.ownerOf(tokenId) returns (address a) {
            ownerOfToken = a;
        }
        catch { }

        return ownerOfToken;
    }

    function getColors(IERC721 callingContract, address ogColorContractAddress, uint256 tokenId) external view returns (string memory back, string memory frame, string memory digit, string memory slug) {

        address ownerOfToken = safeOwnerOf(callingContract, tokenId);
        if (ownerOfToken != address(0)) {
            if (ogColorContractAddress != address(0)) {
                OGColorInterface ogColorContract = OGColorInterface(ogColorContractAddress);
                try ogColorContract.getColors(ownerOfToken, tokenId) returns (string memory extBack, string memory extFrame, string memory extDigit, string memory extSlug) {
                    return (extBack, extFrame, extDigit, extSlug);
                }
                catch { }
            }
        }
        
        return ("<linearGradient id='back'><stop stop-color='#ffffff'/></linearGradient>",
                "<linearGradient id='frame'><stop stop-color='#000000'/></linearGradient>",
                "<linearGradient id='digit'><stop stop-color='#000000'/></linearGradient>",
                "<linearGradient id='slug'><stop stop-color='#ffffff'/></linearGradient>");
    }

    function getColorAttributes(IERC721 callingContract, address ogColorContractAddress, uint256 tokenId) external view returns (string memory) {

        address ownerOfToken = safeOwnerOf(callingContract, tokenId);
        if (ownerOfToken != address(0)) {
            if (ogColorContractAddress != address(0)) {
                OGColorInterface ogColorContract = OGColorInterface(ogColorContractAddress);
                try ogColorContract.getOgAttributes(ownerOfToken, tokenId) returns (string memory extAttributes) {
                    return extAttributes;
                }
                catch { }
            }
        }
        
        return "";
    }
    
    function getOwnedSupportedCollection(IERC721 callingContract, address gotTokenContractAddress, address[] memory supportedCollections, uint256 tokenId) external view returns (address) {
        
        if (gotTokenContractAddress == address(0))
            return address(0);
        
        address ownerOfToken = safeOwnerOf(callingContract, tokenId);
        if (ownerOfToken == address(0))
            return address(0);
    
        bool[] memory ownsTokens;
        
        GotTokenInterface gotTokenContract = GotTokenInterface(gotTokenContractAddress);        
        try gotTokenContract.ownsTokenOfContracts(ownerOfToken, supportedCollections, tokenId) returns (bool[] memory returnValue) {
            ownsTokens = returnValue;
        }
        catch { return address(0); }

        // find the first contract which is owned
        for (uint256 i = 0; i < ownsTokens.length; i++) {
            if (ownsTokens[i])
                return supportedCollections[i];
        }

        return address(0);
    }
}

// File: /src/contracts/interfaces/OGColorInterface.sol




// SPDX-License-Identifier: MIT

pragma solidity 0.8.0;

/**
 * @title The interface to access the OGColor contract to get the colors to render OG svgs
 * @author nfttank.eth
 */
interface OGColorInterface {
    function getColors(address forAddress, uint256 tokenId) external view returns (string memory back, string memory frame, string memory digit, string memory slug);
    function getOgAttributes(address forAddress, uint256 tokenId) external view returns (string memory);
}
// File: /src/contracts/interfaces/GotTokenInterface.sol




// SPDX-License-Identifier: MIT

pragma solidity 0.8.0;

/**
 * @title The interface to access the GotToken contract to check if an address owns a given token of a given contract
 * @author nfttank.eth
 */
interface GotTokenInterface {
    function ownsTokenOfContract(address possibleOwner, address contractAddress, uint256 tokenId) external view returns (bool);
    function ownsTokenOfContracts(address possibleOwner, address[] calldata upToTenContractAddresses, uint256 tokenId) external view returns (bool[] memory);
}
// File: /src/contracts/ERC/HumbleERC721Enumerable.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
import "@openzeppelin/contracts/token/ERC721/extensions/ERC721Enumerable.sol";

/**
 * @dev This is an alternative implementation to OpenZeppelin's ERC721Enumerable.
 * HumbleERC721Enumerable is focussing on reducing the gas costs by reducing efforts
 * in writing methods.
 * @author nfttank.eth
 */
abstract contract HumbleERC721Enumerable is ERC721, IERC721Enumerable {

    mapping(address => uint256[]) internal _owners;
    uint256 private _totalSupply;

    /**
     * @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-totalSupply}.
     */
    function totalSupply() public view virtual override returns (uint256) {
        return _totalSupply;
    }

    /**
     * @dev See {IERC721Enumerable-tokenByIndex}.
     */
    function tokenByIndex(uint256 index) public view virtual override returns (uint256) {
        require(index < _totalSupply, "ERC721Enumerable: global index out of bounds");
        return index;
    }

    /**
     * @dev See {IERC721Enumerable-tokenOfOwnerByIndex}.
     */
    function tokenOfOwnerByIndex(address owner, uint256 index) public view virtual override returns (uint256 tokenId) {
        require(index < balanceOf(owner), "ERC721Enumerable: owner index out of bounds");
        return _owners[owner][index];
    }

    function _beforeTokenTransfer(address from, address to, uint256 tokenId) internal override {
        
        bool isMint = from == address(0);
        bool isBurn = to == address(0) || to == 0x000000000000000000000000000000000000dEaD;
        
        // transfer + burn
        if (!isMint) {
            uint256[] storage tokenIds = _owners[from];

            for (uint16 i = 0; i < tokenIds.length; i++) {
                if (tokenIds[i] == tokenId) {
                    tokenIds[i] = tokenIds[tokenIds.length-1]; // Move the last element to the deleted spot. Remove the last element.
                    tokenIds.pop();
                    break;
                }
            }
        }

        // mint + tranfer
        if (!isBurn) {
            _owners[to].push(tokenId);
        }

        if (isMint) {
            _totalSupply++;
        }
        else if (isBurn) {
            _totalSupply--;
        }

    }
}
// File: base64-sol/base64.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0;

/// @title Base64
/// @author Brecht Devos - <brecht@loopring.org>
/// @notice Provides functions for encoding/decoding base64
library Base64 {
    string internal constant TABLE_ENCODE = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';
    bytes  internal constant TABLE_DECODE = hex"0000000000000000000000000000000000000000000000000000000000000000"
                                            hex"00000000000000000000003e0000003f3435363738393a3b3c3d000000000000"
                                            hex"00000102030405060708090a0b0c0d0e0f101112131415161718190000000000"
                                            hex"001a1b1c1d1e1f202122232425262728292a2b2c2d2e2f303132330000000000";

    function encode(bytes memory data) internal pure returns (string memory) {
        if (data.length == 0) return '';

        // load the table into memory
        string memory table = TABLE_ENCODE;

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

        // add some extra buffer at the end required for the writing
        string memory result = new string(encodedLen + 32);

        assembly {
            // set the actual output length
            mstore(result, encodedLen)

            // prepare the lookup table
            let tablePtr := add(table, 1)

            // input ptr
            let dataPtr := data
            let endPtr := add(dataPtr, mload(data))

            // result ptr, jump over length
            let resultPtr := add(result, 32)

            // run over the input, 3 bytes at a time
            for {} lt(dataPtr, endPtr) {}
            {
                // read 3 bytes
                dataPtr := add(dataPtr, 3)
                let input := mload(dataPtr)

                // write 4 characters
                mstore8(resultPtr, mload(add(tablePtr, and(shr(18, input), 0x3F))))
                resultPtr := add(resultPtr, 1)
                mstore8(resultPtr, mload(add(tablePtr, and(shr(12, input), 0x3F))))
                resultPtr := add(resultPtr, 1)
                mstore8(resultPtr, mload(add(tablePtr, and(shr( 6, input), 0x3F))))
                resultPtr := add(resultPtr, 1)
                mstore8(resultPtr, mload(add(tablePtr, and(        input,  0x3F))))
                resultPtr := add(resultPtr, 1)
            }

            // padding with '='
            switch mod(mload(data), 3)
            case 1 { mstore(sub(resultPtr, 2), shl(240, 0x3d3d)) }
            case 2 { mstore(sub(resultPtr, 1), shl(248, 0x3d)) }
        }

        return result;
    }

    function decode(string memory _data) internal pure returns (bytes memory) {
        bytes memory data = bytes(_data);

        if (data.length == 0) return new bytes(0);
        require(data.length % 4 == 0, "invalid base64 decoder input");

        // load the table into memory
        bytes memory table = TABLE_DECODE;

        // every 4 characters represent 3 bytes
        uint256 decodedLen = (data.length / 4) * 3;

        // add some extra buffer at the end required for the writing
        bytes memory result = new bytes(decodedLen + 32);

        assembly {
            // padding with '='
            let lastBytes := mload(add(data, mload(data)))
            if eq(and(lastBytes, 0xFF), 0x3d) {
                decodedLen := sub(decodedLen, 1)
                if eq(and(lastBytes, 0xFFFF), 0x3d3d) {
                    decodedLen := sub(decodedLen, 1)
                }
            }

            // set the actual output length
            mstore(result, decodedLen)

            // prepare the lookup table
            let tablePtr := add(table, 1)

            // input ptr
            let dataPtr := data
            let endPtr := add(dataPtr, mload(data))

            // result ptr, jump over length
            let resultPtr := add(result, 32)

            // run over the input, 4 characters at a time
            for {} lt(dataPtr, endPtr) {}
            {
               // read 4 characters
               dataPtr := add(dataPtr, 4)
               let input := mload(dataPtr)

               // write 3 bytes
               let output := add(
                   add(
                       shl(18, and(mload(add(tablePtr, and(shr(24, input), 0xFF))), 0xFF)),
                       shl(12, and(mload(add(tablePtr, and(shr(16, input), 0xFF))), 0xFF))),
                   add(
                       shl( 6, and(mload(add(tablePtr, and(shr( 8, input), 0xFF))), 0xFF)),
                               and(mload(add(tablePtr, and(        input , 0xFF))), 0xFF)
                    )
                )
                mstore(resultPtr, shl(232, output))
                resultPtr := add(resultPtr, 3)
            }
        }

        return result;
    }
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/introspection/IERC165.sol)

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/utils/introspection/ERC165.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/introspection/ERC165.sol)

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/Strings.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/Strings.sol)

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/utils/Context.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/Context.sol)

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/Address.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/Address.sol)

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/token/ERC721/extensions/IERC721Metadata.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC721/extensions/IERC721Metadata.sol)

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/token/ERC721/extensions/IERC721Enumerable.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC721/extensions/IERC721Enumerable.sol)

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/extensions/ERC721Enumerable.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC721/extensions/ERC721Enumerable.sol)

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/IERC721Receiver.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC721/IERC721Receiver.sol)

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
// OpenZeppelin Contracts v4.4.1 (token/ERC721/IERC721.sol)

pragma solidity ^0.8.0;

import "../../utils/introspection/IERC165.sol";

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

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

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

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

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

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

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

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

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

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

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

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

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC721/ERC721.sol)

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 {
        _setApprovalForAll(_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 Approve `operator` to operate on all of `owner` tokens
     *
     * Emits a {ApprovalForAll} event.
     */
    function _setApprovalForAll(
        address owner,
        address operator,
        bool approved
    ) internal virtual {
        require(owner != operator, "ERC721: approve to caller");
        _operatorApprovals[owner][operator] = approved;
        emit ApprovalForAll(owner, operator, approved);
    }

    /**
     * @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/ERC20/extensions/IERC20Metadata.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/extensions/IERC20Metadata.sol)

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);
}

// File: @openzeppelin/contracts/token/ERC20/IERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/IERC20.sol)

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/ERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/ERC20.sol)

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: @openzeppelin/contracts/access/Ownable.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (access/Ownable.sol)

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() {
        _transferOwnership(_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 {
        _transferOwnership(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");
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}