// Contract: usernamenft
// Target function: function mintUsernameToken(string memory _username) internal
.
	 *
	 * 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);
}





/**
 * @dev Contract module that helps prevent reentrant calls to a function.
 *
 * Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
 * available, which can be applied to functions to make sure there are no nested
 * (reentrant) calls to them.
 *
 * Note that because there is a single `nonReentrant` guard, functions marked as
 * `nonReentrant` may not call one another. This can be worked around by making
 * those functions `private`, and then adding `external` `nonReentrant` entry
 * points to them.
 *
 * TIP: If you would like to learn more about reentrancy and alternative ways
 * to protect against it, check out our blog post
 * https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
 */
abstract contract ReentrancyGuard {
	// Booleans are more expensive than uint256 or any type that takes up a full
	// word because each write operation emits an extra SLOAD to first read the
	// slot's contents, replace the bits taken up by the boolean, and then write
	// back. This is the compiler's defense against contract upgrades and
	// pointer aliasing, and it cannot be disabled.

	// The values being non-zero value makes deployment a bit more expensive,
	// but in exchange the refund on every call to nonReentrant will be lower in
	// amount. Since refunds are capped to a percentage of the total
	// transaction's gas, it is best to keep them low in cases like this one, to
	// increase the likelihood of the full refund coming into effect.
	uint256 private constant _NOT_ENTERED = 1;
	uint256 private constant _ENTERED = 2;

	uint256 private _status;

	constructor() {
		_status = _NOT_ENTERED;
	}

	/**
	 * @dev Prevents a contract from calling itself, directly or indirectly.
	 * Calling a `nonReentrant` function from another `nonReentrant`
	 * function is not supported. It is possible to prevent this from happening
	 * by making the `nonReentrant` function external, and make it call a
	 * `private` function that does the actual work.
	 */
	modifier nonReentrant() {
		// On the first call to nonReentrant, _notEntered will be true
		require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

		// Any calls to nonReentrant after this point will fail
		_status = _ENTERED;

		_;

		// By storing the original value once again, a refund is triggered (see
		// https://eips.ethereum.org/EIPS/eip-2200)
		_status = _NOT_ENTERED;
	}
}





/**
 * @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);
	}

	function _verifyCallResult(
		bool success,
		bytes memory returndata,
		string memory errorMessage
	) private 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);
			}
		}
	}
}





/// [MIT License]
/// @title Base64
/// @notice Provides a function for encoding some bytes in base64
/// @author Brecht Devos <brecht@loopring.org>
library Base64 {
	bytes internal constant TABLE = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

	/// @notice Encodes some bytes to the base64 representation
	function encode(bytes memory data) internal pure returns (string memory) {
		uint256 len = data.length;
		if (len == 0) return "";

		// multiply by 4/3 rounded up
		uint256 encodedLen = 4 * ((len + 2) / 3);

		// Add some extra buffer at the end
		bytes memory result = new bytes(encodedLen + 32);

		bytes memory table = TABLE;

		assembly {
			let tablePtr := add(table, 1)
			let resultPtr := add(result, 32)

			for {
				let i := 0
			} lt(i, len) {

			} {
				i := add(i, 3)
				let input := and(mload(add(data, i)), 0xffffff)

				let out := mload(add(tablePtr, and(shr(18, input), 0x3F)))
				out := shl(8, out)
				out := add(out, and(mload(add(tablePtr, and(shr(12, input), 0x3F))), 0xFF))
				out := shl(8, out)
				out := add(out, and(mload(add(tablePtr, and(shr(6, input), 0x3F))), 0xFF))
				out := shl(8, out)
				out := add(out, and(mload(add(tablePtr, and(input, 0x3F))), 0xFF))
				out := shl(224, out)

				mstore(resultPtr, out)

				resultPtr := add(resultPtr, 4)
			}

			switch mod(len, 3)
			case 1 {
				mstore(sub(resultPtr, 2), shl(240, 0x3d3d))
			}
			case 2 {
				mstore(sub(resultPtr, 1), shl(248, 0x3d))
			}

			mstore(result, encodedLen)
		}

		return string(result);
	}
}





/**
 * @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);
	}
}





/**
 * username-nft Contract
 */
contract usernamenft is ERC721, ReentrancyGuard, Ownable
{
	struct Username
	{
		string username;
		bytes6 bg_color;
		bytes6 text_color;
		string comment;
		bool exists;
	}

	mapping(uint => Username) private usernamesMapping;
	mapping(string => bool) private usernameExistsMapping;

	uint private end_date;
	uint public max_usernames_per_transaction = 10;
	uint public username_price = 100000000000000000;
	uint public total_usernames = 0;
	uint public max_username_supply = 8888;
	bool public max_username_supply_overriden = false;


	/**
	 * @dev Set up the contract and randomly set the cut off time for season one.
	 */
	constructor() ERC721("username-nft", "NAME") Ownable()
	{
		end_date = getRandomEndDate();
	}


	/**
	 * @dev Allow withdrawal from the main wallet.
	 */
	function withdraw() public onlyOwner
	{
		uint balance = address(this).balance;
		payable(msg.sender).transfer(balance);
	}


	/**
	 * @dev Public payable method to process a single username.
	 *
	 * @param _username string memory
	 */
	function mintUsername(string memory _username) public payable nonReentrant
	{
		require(validateContract());
		require(msg.value >= username_price, "Not enough ether.");
		require(validateUsername(_username));

		mintUsernameToken(_username);
	}


	/**
	 * @dev Public payable method to process an array usernames.
	 *
	 * @param _usernames string[] memory
	 */
	function mintUsernameMulti(string[] memory _usernames) public payable nonReentrant
	{
		require(validateContract());

		uint num_usernames = _usernames.length;

		require(msg.value >= (username_price * num_usernames), "Not enough ether.");
		require((num_usernames > 0) && (num_usernames <= max_usernames_per_transaction), "Too many usernames.");

		// Loop through each username to make sure each of them are valid.
		for (uint i=0; i<num_usernames; i++)
		{
			require(validateUsername(_usernames[i]));
		}

		// All good to go - now mint all the usernames.
		for (uint i=0; i<num_usernames; i++)
		{
			mintUsernameToken(_usernames[i]);
		}
	}


	/**
	 * @dev Check the general contract requirements for minting
	 *
	 * @return bool
	 */
	function validateContract() internal returns(bool)
	{
		// If we've hit the end date and the max supply hasn't been cut down yet, reduce it.
		if ((block.timestamp > end_date) && (!max_username_supply_overriden))
		{
			uint new_max_username_supply = total_usernames + 50;
			if (new_max_username_supply < max_username_supply) max_username_supply = new_max_username_supply;
			max_username_supply_overriden = true;
		}

		require((total_usernames < max_username_supply), "Season one has ended.");

		return true;
	}


	/**
	 * @dev Check the username to make sure it's valid.
	 *
	 * @param _username string memory
	 * @return bool
	 */
	function validateUsername(string memory _username) internal view returns(bool)
	{
		require(usernameExistsMapping[_username] != true, "username exists.");
		require(onlyValidCharacters(_username), "Lowercase letters and numbers only.");
		require(((bytes(_username).length >= 2) && (bytes(_username).length <= 10)), "Must be between 2 and 10 characters.");

		return true;
	}