contract Profile is ERC721Enumerable {
    event NameChange(uint256 indexed tokenId, string newName);
    event BioChange(uint256 indexed tokenId, string bio);

    uint256 public constant NAME_CHANGE_PRICE = 50;
    uint256 public constant BIO_CHANGE_PRICE = 100;

    mapping(uint256 => string) public bio;

    // Mapping from token ID to name
    mapping(uint256 => string) private _tokenName;

    // Mapping if certain name string has already been reserved
    mapping(string => bool) private _nameReserved;

    constructor(string memory _name, string memory _symbol)
        ERC721(_name, _symbol)
    {}

    function changeBio(uint256 _tokenId, string memory _bio) public virtual {
        address owner = ownerOf(_tokenId);
        require(msg.sender == owner, "ERC721: caller is not the owner");

        bio[_tokenId] = _bio;
        emit BioChange(_tokenId, _bio);
    }

    function changeName(uint256 tokenId, string memory newName) public virtual {
        address owner = ownerOf(tokenId);

        require(msg.sender == owner, "ERC721: caller is not the owner");
        require(validateName(newName) == true, "Not a valid new name");
        require(
            sha256(bytes(newName)) != sha256(bytes(_tokenName[tokenId])),
            "New name is same as the current one"
        );
        require(isNameReserved(newName) == false, "Name already reserved");

        // If already named, dereserve old name
        if (bytes(_tokenName[tokenId]).length > 0) {
            toggleReserveName(_tokenName[tokenId], false);
        }
        toggleReserveName(newName, true);
        _tokenName[tokenId] = newName;
        emit NameChange(tokenId, newName);
    }

    /**
     * @dev Reserves the name if isReserve is set to true, de-reserves if set to false
     */
    function toggleReserveName(string memory str, bool isReserve) internal {
        _nameReserved[toLower(str)] = isReserve;
    }

    /**
     * @dev Returns name of the NFT at index.
     */
    function tokenNameByIndex(uint256 index)
        public
        view
        returns (string memory)
    {
        return _tokenName[index];
    }

    /**
     * @dev Returns if the name has been reserved.
     */
    function isNameReserved(string memory nameString)
        public
        view
        returns (bool)
    {
        return _nameReserved[toLower(nameString)];
    }

    function validateName(string memory str) public pure returns (bool) {
        bytes memory b = bytes(str);
        if (b.length < 1) return false;
        if (b.length > 25) return false; // Cannot be longer than 25 characters
        if (b[0] == 0x20) return false; // Leading space
        if (b[b.length - 1] == 0x20) return false; // Trailing space

        bytes1 lastChar = b[0];

        for (uint256 i; i < b.length; i++) {
            bytes1 char = b[i];

            if (char == 0x20 && lastChar == 0x20) return false; // Cannot contain continous spaces

            if (
                !(char >= 0x30 && char <= 0x39) && //9-0
                !(char >= 0x41 && char <= 0x5A) && //A-Z
                !(char >= 0x61 && char <= 0x7A) && //a-z
                !(char == 0x20) //space
            ) return false;

            lastChar = char;
        }

        return true;
    }

    /**
     * @dev Converts the string to lowercase
     */
    function toLower(string memory str) public pure returns (string memory) {
        bytes memory bStr = bytes(str);
        bytes memory bLower = new bytes(bStr.length);
        for (uint256 i = 0; i < bStr.length; i++) {
            // Uppercase character
            if ((uint8(bStr[i]) >= 65) && (uint8(bStr[i]) <= 90)) {
                bLower[i] = bytes1(uint8(bStr[i]) + 32);
            } else {
                bLower[i] = bStr[i];
            }
        }
        return string(bLower);
    }
}
function toLower(string memory str) public pure returns (string memory) {
    bytes memory bStr = bytes(str);
    bytes memory bLower = new bytes(bStr.length);
    for (uint256 i = 0; i < bStr.length; i++) {
        // Uppercase character
        if ((uint8(bStr[i]) >= 65) && (uint8(bStr[i]) <= 90)) {
            bLower[i] = bytes1(uint8(bStr[i]) + 32);
        } else {
            bLower[i] = bStr[i];
        }
    }
    return string(bLower);
}

/**
 * @dev Converts the string to lowercase
 */