// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

/*
    Fully commented standard ERC721 Distilled from OpenZeppelin Docs
    Base for Building ERC721 by Martin McConnell
    All the utility without the fluff.
*/


interface IERC165 {
    function supportsInterface(bytes4 interfaceId) external view returns (bool);
}

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`.
    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;
}

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);
}

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);
}

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);
            }
        }
    }
}

abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }
}

abstract contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor() {
        _setOwner(_msgSender());
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
        _;
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        _setOwner(address(0));
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        _setOwner(newOwner);
    }

    function _setOwner(address newOwner) private {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}

abstract contract Functionality {
    function toString(uint256 value) internal pure returns (string memory) {
        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);
    }
    
    bool private _reentryKey = false;
    modifier reentryLock {
        require(!_reentryKey, "attempt to reenter a locked function");
        _reentryKey = true;
        _;
        _reentryKey = false;
    }
}


// ******************************************************************************************************************************
// **************************************************  Start of Main Contract ***************************************************
// ******************************************************************************************************************************

contract dice is IERC721, Ownable, Functionality {

    using Address for address;
    
    // Token name
    string private _name;

    // Token symbol
    string private _symbol;
    
    // URI Root Location for Json Files
    string private _baseURI;

    // 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;
    
    //for setting purchase limits per collection
    mapping(uint256 => mapping(address => uint256)) public numPurchased;
    
    struct diceGroup {
        bool diceLock;
        
        uint256 numTokens; //tokens minted so far
        uint256 maxTokens; //max tokens of this type
        uint256 startId; //Start location for tokenID
        uint256 price; //Cost in wei
        uint256 payoutPercent;
        uint256 payoutBalance;
        uint256 giveawayBalance;
        uint256 purchaseThreshold;
        
        string tokenURI;
        address payoutAddress;
    }
    
    diceGroup[] collection;
    
    //TokenID to collection ID
    mapping (uint256 => uint256) diceType;
    
    //Holder's Dice Bag
    mapping (address => uint256[]) diceBag;
    
    //Global Variables
    uint256 totalTokensReserved;
    uint256 primaryBalance;
    
    /**
     * @dev Initializes the contract by setting a `name` and a `symbol` to the token collection.
     */
    constructor() {
        _name = "DICE";
        _symbol = "DICE";
        _baseURI = "https://triple7dice.club/metadata/contract.json";
    }

    // **************************************** Internal Functions *******************
    function createDice(uint256 maxTokens, uint256 price, string memory uri_, uint256 maxPurchase) external onlyOwner reentryLock {
        //initialize the new token
        diceGroup memory newDice;
        newDice.numTokens = 0;
        newDice.maxTokens = maxTokens;
        newDice.startId = totalTokensReserved;
        newDice.payoutAddress = address(0);
        newDice.payoutPercent = 0;
        newDice.giveawayBalance = 0;
        newDice.price = price;
        newDice.tokenURI = uri_;
        newDice.diceLock = true;
        newDice.purchaseThreshold = maxPurchase;
        
        //Incriment the allocation variable
        totalTokensReserved += maxTokens;
        
        //Add the new token to the collection
        collection.push(newDice);
    }
    
    function mint(uint256 ID, uint256 amount) external payable {
        diceGroup memory tempId = collection[ID];
        uint256 price = tempId.price;
        
        require(amount > 0, "You must mint a positive number");
        require(numPurchased[ID][_msgSender()] + amount <= tempId.purchaseThreshold, "Can't mint that many");
        require(amount + tempId.numTokens + tempId.giveawayBalance <= tempId.maxTokens, "Not enough dice remaining");
        require(msg.value >= price * amount, "You can't afford that");
        require(!tempId.diceLock, "Those dice are not for sale");
        
        //handle payouts
        uint256 reserve = (amount * price * tempId.payoutPercent) / 100;
        uint256 leftoverBalance = (price * amount) - reserve;
        collection[ID].payoutBalance += reserve;
        primaryBalance += leftoverBalance;
        
        //mint tokens and update tallies
        uint256 tokenStart = collection[ID].startId + collection[ID].numTokens;
        for ( uint256 i; i < amount; i++) {
            _safeMint(_msgSender(), tokenStart + i);
            diceType[tokenStart + i] = ID;
        }
        collection[ID].numTokens +=amount;
        
        if ((price * amount) < msg.value) {
            uint256 change = (msg.value - (price*amount));
            (bool success, ) = msg.sender.call{value: change}("");
            require(success, "Mint: unable to send change to user");
        }
        
    }
    
    function founderMint(uint256 ID, address[] memory to) external reentryLock{
        uint256 arraySize = to.length;
        require(_msgSender() == collection[ID].payoutAddress || _msgSender() == owner());
        diceGroup memory tempId = collection[ID];
        require(tempId.numTokens + tempId.giveawayBalance + arraySize <= tempId.maxTokens, "Not enough dice remaining");

        uint256 tokenStart = tempId.startId + tempId.numTokens;
        collection[ID].numTokens += arraySize;

        if (collection[ID].giveawayBalance >= arraySize) {
            collection[ID].giveawayBalance -= arraySize;
        } else {
            collection[ID].giveawayBalance = 0;
        }
        
        for (uint256 i; i < arraySize; i++) {
            diceType[tokenStart + i] = ID;
            _safeMint(to[i], tokenStart + i);
        }
    }
    
    function assignFounder(uint256 ID, uint256 founderPercentage, address receiver, uint256 freebies) external onlyOwner {
        //Approve a sponsored account to receive payment or ammend contract terms
        collection[ID].payoutPercent = founderPercentage;
        collection[ID].payoutAddress = receiver;
        collection[ID].giveawayBalance = freebies;
    }
    
    function ownerFunds() external view onlyOwner returns(uint256) {
        return primaryBalance;
    }
    
    function withdraw(uint256 sendAmount) external onlyOwner {
        require(sendAmount <= primaryBalance);
        primaryBalance -= sendAmount;
        
        (bool success, ) = msg.sender.call{value: sendAmount}("");
        require(success, "Transaction Unsuccessful");
    }
    
    function receiveFunds(uint256 ID) external reentryLock {
        //Verify ownership of the token class
        require(collection[ID].payoutAddress != address(0));
        require(_msgSender() == collection[ID].payoutAddress, "Unauthorized Transaction!");
        
        uint256 sendAmount = collection[ID].payoutBalance;
        collection[ID].payoutBalance = 0;
        
        (bool success, ) = msg.sender.call{value: sendAmount}("");
        require(success, "Transaction Unsuccessful");
    }

    //@dev See {IERC165-supportsInterface}. Interfaces Supported by this Standard
    function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
        return  interfaceId == type(IERC721).interfaceId ||
                interfaceId == type(IERC721Metadata).interfaceId ||
                interfaceId == type(IERC165).interfaceId ||
                interfaceId == dice.onERC721Received.selector;
    }
    
    // **************************************** Metadata Standard Functions **********
    //@dev Returns the token collection name.
    function name() external view returns (string memory){
        return _name;
    }

    //@dev Returns the token collection symbol.
    function symbol() external view returns (string memory){
        return _symbol;
    }
    
    // ******************************* Dice Interface ********************************
    
    function setPurchaseMax(uint groupID, uint256 maxPerWallet) external {
        require(_msgSender() == owner() || _msgSender() == collection[groupID].payoutAddress, "unauthorized access");
        collection[groupID].purchaseThreshold = maxPerWallet;
    }
    
    function getType(uint256 tokenId) external view returns (uint256) {
        return diceType[tokenId];
    }
    
    function getPrice(uint256 groupID) external view returns (uint256) {
        return collection[groupID].price;
    }
    
    function getDiceMinted(uint256 groupID) external view returns (uint256) {
        return collection[groupID].numTokens;
    }
    
    function getURI(uint256 groupID) external view returns (string memory) {
        return collection[groupID].tokenURI;
    }
    
    function getAllDice(address holder) external view returns (uint256[] memory) {
        return diceBag[holder];
    }
    
    function setURI(uint256 groupID, string memory uri_) external {
        require(_msgSender() == owner() || _msgSender() == collection[groupID].payoutAddress, "unauthorized access");
        collection[groupID].tokenURI = uri_;
    }
    
    function verifyFunds(uint256 ID) external view returns(uint256) {
        require(_msgSender() == owner() || _msgSender() == collection[ID].payoutAddress, "unauthorized access");
        return collection[ID].payoutBalance;
    }
    
    function lockMint(uint256 ID) external {
        require(_msgSender() == owner() || _msgSender() == collection[ID].payoutAddress, "unauthorized access");
        collection[ID].diceLock = true;
    }
    
    function unlockMint(uint256 ID) external {
        require(_msgSender() == owner() || _msgSender() == collection[ID].payoutAddress, "unauthorized access");
        collection[ID].diceLock = false;
    }
    
    function checkLock(uint256 ID) external view returns(bool) {
        return collection[ID].diceLock;
    }
    
    // ************************** Internal Functions ***********************************
    function addDiceToBag(address holder, uint256 tokenId) internal {
        diceBag[holder].push(tokenId);
    }
    
    function removeDiceFromBag(address holder, uint256 tokenId) internal {
        uint256[] memory diceCollection = diceBag[holder];
        bool foundIt;
        uint256 index;
        uint256 length = diceCollection.length;
        
        for (uint256 i; i < length; i++) {
            if (!foundIt) {
                if (diceCollection[i] == tokenId) { foundIt = true;}
            }
            if (foundIt) {
                if (i+1 < length) {
                    diceCollection[i] = diceCollection[i+1];
                    index = i;
                    break;
                }
            }
        }
        
        //make changes to the actual user bag
        if (index < length - 1) {
            diceBag[holder][index] = diceCollection[length - 1];
        }
        diceBag[holder].pop();
    }

    /**
     * @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 {IERC721-approve}.
     */
    function approve(address to, uint256 tokenId) public virtual override {
        address owner = ownerOf(tokenId);
        require(to != owner, "ERC721: approval to current owner");

        require(
            msg.sender == owner || isApprovedForAll(owner, msg.sender),
            "ERC721: approve caller is not owner nor approved for all"
        );

        _approve(to, tokenId);
    }

    /**
     * @dev See {IERC721-getApproved}.
     */
    function getApproved(uint256 tokenId) public view virtual override returns (address) {
        require(_exists(tokenId), "ERC721: approved query for nonexistent token");

        return _tokenApprovals[tokenId];
    }

    /**
     * @dev See {IERC721-setApprovalForAll}.
     */
    function setApprovalForAll(address operator, bool approved) public virtual override {
        require(operator != msg.sender, "ERC721: approve to caller");

        _operatorApprovals[msg.sender][operator] = approved;
        emit ApprovalForAll(msg.sender, 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(msg.sender, 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(msg.sender, 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 = 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 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(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(ownerOf(tokenId), to, tokenId);
    }

    /**
     * @dev Internal function to invoke {IERC721Receiver-onERC721Received} on a target address.
     * The call is not executed if the target address is not a contract.
     *
     * @param from address representing the previous owner of the given token ID
     * @param to target address that will receive the tokens
     * @param tokenId uint256 ID of the token to be transferred
     * @param _data bytes optional data to send along with the call
     * @return bool whether the call correctly returned the expected magic value
     */
    function _checkOnERC721Received(
        address from,
        address to,
        uint256 tokenId,
        bytes memory _data
    ) private returns (bool) {
        if (to.isContract()) {
            try IERC721Receiver(to).onERC721Received(msg.sender, from, tokenId, _data) returns (bytes4 retval) {
                return retval == IERC721Receiver(to).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;
        }
    }
    
    // *********************** ERC721 Token Receiver **********************
    /**
     * @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) {
        //InterfaceID=0x150b7a02
        return this.onERC721Received.selector;
    }

    /**
     * @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 {
        //transfer functions take care of checks so we don't have to
        if(from != address(0)){
            removeDiceFromBag(from, tokenId);
        }
        if(to != address(0)){
            addDiceToBag(to, tokenId);
        }
    }

    //********************************************************
    //**************** Fallback and Generic ******************
    //********************************************************
    
    //contractURI function for OpenSea, This is for ALL dice collections
    function contractURI() external view returns (string memory) {
        return string(abi.encodePacked(_baseURI));
    }
    
    // TokenURI for OS
    function tokenURI(uint256 tokenId) public view returns (string memory) {
        uint256 groupID = diceType[tokenId];
        ///require that token exists
        require((tokenId - collection[groupID].startId) < collection[groupID].numTokens);
        
        return string(abi.encodePacked(collection[groupID].tokenURI, toString((tokenId - collection[groupID].startId)), ".json"));
    }
    
    //Fallback function
    receive () external payable {
        primaryBalance += msg.value;
    }
    
}