/***
 *    ██████╗ ███████╗ ██████╗  ██████╗ 
 *    ██╔══██╗██╔════╝██╔════╝ ██╔═══██╗
 *    ██║  ██║█████╗  ██║  ███╗██║   ██║
 *    ██║  ██║██╔══╝  ██║   ██║██║   ██║
 *    ██████╔╝███████╗╚██████╔╝╚██████╔╝
 *    ╚═════╝ ╚══════╝ ╚═════╝  ╚═════╝ 
 *    
 * https://dego.finance
                                  
* MIT License
* ===========
*
* Copyright (c) 2020 dego
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
*/
// File: @openzeppelin/contracts/math/Math.sol

pragma solidity ^0.5.0;

/**
 * @dev Standard math utilities missing in the Solidity language.
 */
library Math {
    /**
     * @dev Returns the largest of two numbers.
     */
    function max(uint256 a, uint256 b) internal pure returns (uint256) {
        return a >= b ? a : b;
    }

    /**
     * @dev Returns the smallest of two numbers.
     */
    function min(uint256 a, uint256 b) internal pure returns (uint256) {
        return a < b ? a : b;
    }

    /**
     * @dev Returns the average of two numbers. The result is rounded towards
     * zero.
     */
    function average(uint256 a, uint256 b) internal pure returns (uint256) {
        // (a + b) / 2 can overflow, so we distribute
        return (a / 2) + (b / 2) + ((a % 2 + b % 2) / 2);
    }
}

// File: @openzeppelin/contracts/math/SafeMath.sol

pragma solidity ^0.5.0;

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     * - Subtraction cannot overflow.
     *
     * _Available since v2.4.0._
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;

        return c;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return div(a, b, "SafeMath: division by zero");
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     *
     * _Available since v2.4.0._
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0, errorMessage);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts with custom message when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     *
     * _Available since v2.4.0._
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}

// File: @openzeppelin/contracts/GSN/Context.sol

pragma solidity ^0.5.0;

/*
 * @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 GSN 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.
 */
contract Context {
    // Empty internal constructor, to prevent people from mistakenly deploying
    // an instance of this contract, which should be used via inheritance.
    constructor () internal { }
    // solhint-disable-previous-line no-empty-blocks

    function _msgSender() internal view returns (address payable) {
        return msg.sender;
    }

    function _msgData() internal view returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}

// File: @openzeppelin/contracts/introspection/IERC165.sol

pragma solidity ^0.5.0;

/**
 * @dev Interface of the ERC165 standard, as defined in the
 * https://eips.ethereum.org/EIPS/eip-165[EIP].
 *
 * Implementers can declare support of contract interfaces, which can then be
 * queried by others ({ERC165Checker}).
 *
 * For an implementation, see {ERC165}.
 */
interface IERC165 {
    /**
     * @dev Returns true if this contract implements the interface defined by
     * `interfaceId`. See the corresponding
     * https://eips.ethereum.org/EIPS/eip-165#how-interfaces-are-identified[EIP section]
     * to learn more about how these ids are created.
     *
     * This function call must use less than 30 000 gas.
     */
    function supportsInterface(bytes4 interfaceId) external view returns (bool);
}

// File: @openzeppelin/contracts/token/ERC721/IERC721.sol

pragma solidity ^0.5.0;


/**
 * @dev Required interface of an ERC721 compliant contract.
 */
contract IERC721 is IERC165 {
    event Transfer(address indexed from, address indexed to, uint256 indexed tokenId);
    event Approval(address indexed owner, address indexed approved, uint256 indexed tokenId);
    event ApprovalForAll(address indexed owner, address indexed operator, bool approved);

    /**
     * @dev Returns the number of NFTs in `owner`'s account.
     */
    function balanceOf(address owner) public view returns (uint256 balance);

    /**
     * @dev Returns the owner of the NFT specified by `tokenId`.
     */
    function ownerOf(uint256 tokenId) public view returns (address owner);

    /**
     * @dev Transfers a specific NFT (`tokenId`) from one account (`from`) to
     * another (`to`).
     *
     *
     *
     * Requirements:
     * - `from`, `to` cannot be zero.
     * - `tokenId` must be owned by `from`.
     * - If the caller is not `from`, it must be have been allowed to move this
     * NFT by either {approve} or {setApprovalForAll}.
     */
    function safeTransferFrom(address from, address to, uint256 tokenId) public;
    /**
     * @dev Transfers a specific NFT (`tokenId`) from one account (`from`) to
     * another (`to`).
     *
     * Requirements:
     * - If the caller is not `from`, it must be approved to move this NFT by
     * either {approve} or {setApprovalForAll}.
     */
    function transferFrom(address from, address to, uint256 tokenId) public;
    function approve(address to, uint256 tokenId) public;
    function getApproved(uint256 tokenId) public view returns (address operator);

    function setApprovalForAll(address operator, bool _approved) public;
    function isApprovedForAll(address owner, address operator) public view returns (bool);


    function safeTransferFrom(address from, address to, uint256 tokenId, bytes memory data) public;
}

// File: @openzeppelin/contracts/token/ERC721/IERC721Enumerable.sol

pragma solidity ^0.5.0;


/**
 * @title ERC-721 Non-Fungible Token Standard, optional enumeration extension
 * @dev See https://eips.ethereum.org/EIPS/eip-721
 */
contract IERC721Enumerable is IERC721 {
    function totalSupply() public view returns (uint256);
    function tokenOfOwnerByIndex(address owner, uint256 index) public view returns (uint256 tokenId);

    function tokenByIndex(uint256 index) public view returns (uint256);
}

// File: @openzeppelin/contracts/token/ERC721/IERC721Receiver.sol

pragma solidity ^0.5.0;

/**
 * @title ERC721 token receiver interface
 * @dev Interface for any contract that wants to support safeTransfers
 * from ERC721 asset contracts.
 */
contract IERC721Receiver {
    /**
     * @notice Handle the receipt of an NFT
     * @dev The ERC721 smart contract calls this function on the recipient
     * after a {IERC721-safeTransferFrom}. This function MUST return the function selector,
     * otherwise the caller will revert the transaction. The selector to be
     * returned can be obtained as `this.onERC721Received.selector`. This
     * function MAY throw to revert and reject the transfer.
     * Note: the ERC721 contract address is always the message sender.
     * @param operator The address which called `safeTransferFrom` function
     * @param from The address which previously owned the token
     * @param tokenId The NFT identifier which is being transferred
     * @param data Additional data with no specified format
     * @return bytes4 `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`
     */
    function onERC721Received(address operator, address from, uint256 tokenId, bytes memory data)
    public returns (bytes4);
}

// File: @openzeppelin/contracts/utils/Address.sol

pragma solidity ^0.5.5;

/**
 * @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) {
        // According to EIP-1052, 0x0 is the value returned for not-yet created accounts
        // and 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470 is returned
        // for accounts without code, i.e. `keccak256('')`
        bytes32 codehash;
        bytes32 accountHash = 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470;
        // solhint-disable-next-line no-inline-assembly
        assembly { codehash := extcodehash(account) }
        return (codehash != accountHash && codehash != 0x0);
    }

    /**
     * @dev Converts an `address` into `address payable`. Note that this is
     * simply a type cast: the actual underlying value is not changed.
     *
     * _Available since v2.4.0._
     */
    function toPayable(address account) internal pure returns (address payable) {
        return address(uint160(account));
    }

    /**
     * @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].
     *
     * _Available since v2.4.0._
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        // solhint-disable-next-line avoid-call-value
        (bool success, ) = recipient.call.value(amount)("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }
}

// File: @openzeppelin/contracts/drafts/Counters.sol

pragma solidity ^0.5.0;


/**
 * @title Counters
 * @author Matt Condon (@shrugs)
 * @dev Provides counters that can only be incremented or decremented by one. This can be used e.g. to track the number
 * of elements in a mapping, issuing ERC721 ids, or counting request ids.
 *
 * Include with `using Counters for Counters.Counter;`
 * Since it is not possible to overflow a 256 bit integer with increments of one, `increment` can skip the {SafeMath}
 * overflow check, thereby saving gas. This does assume however correct usage, in that the underlying `_value` is never
 * directly accessed.
 */
library Counters {
    using SafeMath for uint256;

    struct Counter {
        // This variable should never be directly accessed by users of the library: interactions must be restricted to
        // the library's function. As of Solidity v0.5.2, this cannot be enforced, though there is a proposal to add
        // this feature: see https://github.com/ethereum/solidity/issues/4637
        uint256 _value; // default: 0
    }

    function current(Counter storage counter) internal view returns (uint256) {
        return counter._value;
    }

    function increment(Counter storage counter) internal {
        // The {SafeMath} overflow check can be skipped here, see the comment at the top
        counter._value += 1;
    }

    function decrement(Counter storage counter) internal {
        counter._value = counter._value.sub(1);
    }
}

// File: @openzeppelin/contracts/introspection/ERC165.sol

pragma solidity ^0.5.0;


/**
 * @dev Implementation of the {IERC165} interface.
 *
 * Contracts may inherit from this and call {_registerInterface} to declare
 * their support of an interface.
 */
contract ERC165 is IERC165 {
    /*
     * bytes4(keccak256('supportsInterface(bytes4)')) == 0x01ffc9a7
     */
    bytes4 private constant _INTERFACE_ID_ERC165 = 0x01ffc9a7;

    /**
     * @dev Mapping of interface ids to whether or not it's supported.
     */
    mapping(bytes4 => bool) private _supportedInterfaces;

    constructor () internal {
        // Derived contracts need only register support for their own interfaces,
        // we register support for ERC165 itself here
        _registerInterface(_INTERFACE_ID_ERC165);
    }

    /**
     * @dev See {IERC165-supportsInterface}.
     *
     * Time complexity O(1), guaranteed to always use less than 30 000 gas.
     */
    function supportsInterface(bytes4 interfaceId) external view returns (bool) {
        return _supportedInterfaces[interfaceId];
    }

    /**
     * @dev Registers the contract as an implementer of the interface defined by
     * `interfaceId`. Support of the actual ERC165 interface is automatic and
     * registering its interface id is not required.
     *
     * See {IERC165-supportsInterface}.
     *
     * Requirements:
     *
     * - `interfaceId` cannot be the ERC165 invalid interface (`0xffffffff`).
     */
    function _registerInterface(bytes4 interfaceId) internal {
        require(interfaceId != 0xffffffff, "ERC165: invalid interface id");
        _supportedInterfaces[interfaceId] = true;
    }
}

// File: @openzeppelin/contracts/token/ERC721/ERC721.sol

pragma solidity ^0.5.0;








/**
 * @title ERC721 Non-Fungible Token Standard basic implementation
 * @dev see https://eips.ethereum.org/EIPS/eip-721
 */
contract ERC721 is Context, ERC165, IERC721 {
    using SafeMath for uint256;
    using Address for address;
    using Counters for Counters.Counter;

    // Equals to `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`
    // which can be also obtained as `IERC721Receiver(0).onERC721Received.selector`
    bytes4 private constant _ERC721_RECEIVED = 0x150b7a02;

    // Mapping from token ID to owner
    mapping (uint256 => address) private _tokenOwner;

    // Mapping from token ID to approved address
    mapping (uint256 => address) private _tokenApprovals;

    // Mapping from owner to number of owned token
    mapping (address => Counters.Counter) private _ownedTokensCount;

    // Mapping from owner to operator approvals
    mapping (address => mapping (address => bool)) private _operatorApprovals;

    /*
     *     bytes4(keccak256('balanceOf(address)')) == 0x70a08231
     *     bytes4(keccak256('ownerOf(uint256)')) == 0x6352211e
     *     bytes4(keccak256('approve(address,uint256)')) == 0x095ea7b3
     *     bytes4(keccak256('getApproved(uint256)')) == 0x081812fc
     *     bytes4(keccak256('setApprovalForAll(address,bool)')) == 0xa22cb465
     *     bytes4(keccak256('isApprovedForAll(address,address)')) == 0xe985e9c5
     *     bytes4(keccak256('transferFrom(address,address,uint256)')) == 0x23b872dd
     *     bytes4(keccak256('safeTransferFrom(address,address,uint256)')) == 0x42842e0e
     *     bytes4(keccak256('safeTransferFrom(address,address,uint256,bytes)')) == 0xb88d4fde
     *
     *     => 0x70a08231 ^ 0x6352211e ^ 0x095ea7b3 ^ 0x081812fc ^
     *        0xa22cb465 ^ 0xe985e9c ^ 0x23b872dd ^ 0x42842e0e ^ 0xb88d4fde == 0x80ac58cd
     */
    bytes4 private constant _INTERFACE_ID_ERC721 = 0x80ac58cd;

    constructor () public {
        // register the supported interfaces to conform to ERC721 via ERC165
        _registerInterface(_INTERFACE_ID_ERC721);
    }

    /**
     * @dev Gets the balance of the specified address.
     * @param owner address to query the balance of
     * @return uint256 representing the amount owned by the passed address
     */
    function balanceOf(address owner) public view returns (uint256) {
        require(owner != address(0), "ERC721: balance query for the zero address");

        return _ownedTokensCount[owner].current();
    }

    /**
     * @dev Gets the owner of the specified token ID.
     * @param tokenId uint256 ID of the token to query the owner of
     * @return address currently marked as the owner of the given token ID
     */
    function ownerOf(uint256 tokenId) public view returns (address) {
        address owner = _tokenOwner[tokenId];
        require(owner != address(0), "ERC721: owner query for nonexistent token");

        return owner;
    }

    /**
     * @dev Approves another address to transfer the given token ID
     * The zero address indicates there is no approved address.
     * There can only be one approved address per token at a given time.
     * Can only be called by the token owner or an approved operator.
     * @param to address to be approved for the given token ID
     * @param tokenId uint256 ID of the token to be approved
     */
    function approve(address to, uint256 tokenId) public {
        address owner = 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"
        );

        _tokenApprovals[tokenId] = to;
        emit Approval(owner, to, tokenId);
    }

    /**
     * @dev Gets the approved address for a token ID, or zero if no address set
     * Reverts if the token ID does not exist.
     * @param tokenId uint256 ID of the token to query the approval of
     * @return address currently approved for the given token ID
     */
    function getApproved(uint256 tokenId) public view returns (address) {
        require(_exists(tokenId), "ERC721: approved query for nonexistent token");

        return _tokenApprovals[tokenId];
    }

    /**
     * @dev Sets or unsets the approval of a given operator
     * An operator is allowed to transfer all tokens of the sender on their behalf.
     * @param to operator address to set the approval
     * @param approved representing the status of the approval to be set
     */
    function setApprovalForAll(address to, bool approved) public {
        require(to != _msgSender(), "ERC721: approve to caller");

        _operatorApprovals[_msgSender()][to] = approved;
        emit ApprovalForAll(_msgSender(), to, approved);
    }

    /**
     * @dev Tells whether an operator is approved by a given owner.
     * @param owner owner address which you want to query the approval of
     * @param operator operator address which you want to query the approval of
     * @return bool whether the given operator is approved by the given owner
     */
    function isApprovedForAll(address owner, address operator) public view returns (bool) {
        return _operatorApprovals[owner][operator];
    }

    /**
     * @dev Transfers the ownership of a given token ID to another address.
     * Usage of this method is discouraged, use {safeTransferFrom} whenever possible.
     * Requires the msg.sender to be the owner, approved, or operator.
     * @param from current owner of the token
     * @param to address to receive the ownership of the given token ID
     * @param tokenId uint256 ID of the token to be transferred
     */
    function transferFrom(address from, address to, uint256 tokenId) public {
        //solhint-disable-next-line max-line-length
        require(_isApprovedOrOwner(_msgSender(), tokenId), "ERC721: transfer caller is not owner nor approved");

        _transferFrom(from, to, tokenId);
    }

    /**
     * @dev Safely transfers the ownership of a given token ID to another address
     * If the target address is a contract, it must implement {IERC721Receiver-onERC721Received},
     * which is called upon a safe transfer, and return the magic value
     * `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`; otherwise,
     * the transfer is reverted.
     * Requires the msg.sender to be the owner, approved, or operator
     * @param from current owner of the token
     * @param to address to receive the ownership of the given token ID
     * @param tokenId uint256 ID of the token to be transferred
     */
    function safeTransferFrom(address from, address to, uint256 tokenId) public {
        safeTransferFrom(from, to, tokenId, "");
    }

    /**
     * @dev Safely transfers the ownership of a given token ID to another address
     * If the target address is a contract, it must implement {IERC721Receiver-onERC721Received},
     * which is called upon a safe transfer, and return the magic value
     * `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`; otherwise,
     * the transfer is reverted.
     * Requires the _msgSender() to be the owner, approved, or operator
     * @param from current owner of the token
     * @param to address to receive the ownership of the given token ID
     * @param tokenId uint256 ID of the token to be transferred
     * @param _data bytes data to send along with a safe transfer check
     */
    function safeTransferFrom(address from, address to, uint256 tokenId, bytes memory _data) public {
        require(_isApprovedOrOwner(_msgSender(), tokenId), "ERC721: transfer caller is not owner nor approved");
        _safeTransferFrom(from, to, tokenId, _data);
    }

    /**
     * @dev Safely transfers the ownership of a given token ID to another address
     * If the target address is a contract, it must implement `onERC721Received`,
     * which is called upon a safe transfer, and return the magic value
     * `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`; otherwise,
     * the transfer is reverted.
     * Requires the msg.sender to be the owner, approved, or operator
     * @param from current owner of the token
     * @param to address to receive the ownership of the given token ID
     * @param tokenId uint256 ID of the token to be transferred
     * @param _data bytes data to send along with a safe transfer check
     */
    function _safeTransferFrom(address from, address to, uint256 tokenId, bytes memory _data) internal {
        _transferFrom(from, to, tokenId);
        require(_checkOnERC721Received(from, to, tokenId, _data), "ERC721: transfer to non ERC721Receiver implementer");
    }

    /**
     * @dev Returns whether the specified token exists.
     * @param tokenId uint256 ID of the token to query the existence of
     * @return bool whether the token exists
     */
    function _exists(uint256 tokenId) internal view returns (bool) {
        address owner = _tokenOwner[tokenId];
        return owner != address(0);
    }

    /**
     * @dev Returns whether the given spender can transfer a given token ID.
     * @param spender address of the spender to query
     * @param tokenId uint256 ID of the token to be transferred
     * @return bool whether the msg.sender is approved for the given token ID,
     * is an operator of the owner, or is the owner of the token
     */
    function _isApprovedOrOwner(address spender, uint256 tokenId) internal view 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 Internal function to safely mint a new token.
     * Reverts if the given token ID already exists.
     * If the target address is a contract, it must implement `onERC721Received`,
     * which is called upon a safe transfer, and return the magic value
     * `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`; otherwise,
     * the transfer is reverted.
     * @param to The address that will own the minted token
     * @param tokenId uint256 ID of the token to be minted
     */
    function _safeMint(address to, uint256 tokenId) internal {
        _safeMint(to, tokenId, "");
    }

    /**
     * @dev Internal function to safely mint a new token.
     * Reverts if the given token ID already exists.
     * If the target address is a contract, it must implement `onERC721Received`,
     * which is called upon a safe transfer, and return the magic value
     * `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`; otherwise,
     * the transfer is reverted.
     * @param to The address that will own the minted token
     * @param tokenId uint256 ID of the token to be minted
     * @param _data bytes data to send along with a safe transfer check
     */
    function _safeMint(address to, uint256 tokenId, bytes memory _data) internal {
        _mint(to, tokenId);
        require(_checkOnERC721Received(address(0), to, tokenId, _data), "ERC721: transfer to non ERC721Receiver implementer");
    }

    /**
     * @dev Internal function to mint a new token.
     * Reverts if the given token ID already exists.
     * @param to The address that will own the minted token
     * @param tokenId uint256 ID of the token to be minted
     */
    function _mint(address to, uint256 tokenId) internal {
        require(to != address(0), "ERC721: mint to the zero address");
        require(!_exists(tokenId), "ERC721: token already minted");

        _tokenOwner[tokenId] = to;
        _ownedTokensCount[to].increment();

        emit Transfer(address(0), to, tokenId);
    }

    /**
     * @dev Internal function to burn a specific token.
     * Reverts if the token does not exist.
     * Deprecated, use {_burn} instead.
     * @param owner owner of the token to burn
     * @param tokenId uint256 ID of the token being burned
     */
    function _burn(address owner, uint256 tokenId) internal {
        require(ownerOf(tokenId) == owner, "ERC721: burn of token that is not own");

        _clearApproval(tokenId);

        _ownedTokensCount[owner].decrement();
        _tokenOwner[tokenId] = address(0);

        emit Transfer(owner, address(0), tokenId);
    }

    /**
     * @dev Internal function to burn a specific token.
     * Reverts if the token does not exist.
     * @param tokenId uint256 ID of the token being burned
     */
    function _burn(uint256 tokenId) internal {
        _burn(ownerOf(tokenId), tokenId);
    }

    /**
     * @dev Internal function to transfer ownership of a given token ID to another address.
     * As opposed to {transferFrom}, this imposes no restrictions on msg.sender.
     * @param from current owner of the token
     * @param to address to receive the ownership of the given token ID
     * @param tokenId uint256 ID of the token to be transferred
     */
    function _transferFrom(address from, address to, uint256 tokenId) internal {
        require(ownerOf(tokenId) == from, "ERC721: transfer of token that is not own");
        require(to != address(0), "ERC721: transfer to the zero address");

        _clearApproval(tokenId);

        _ownedTokensCount[from].decrement();
        _ownedTokensCount[to].increment();

        _tokenOwner[tokenId] = to;

        emit Transfer(from, 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.
     *
     * This is an internal detail of the `ERC721` contract and its use is deprecated.
     * @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)
        internal returns (bool)
    {
        if (!to.isContract()) {
            return true;
        }
        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = to.call(abi.encodeWithSelector(
            IERC721Receiver(to).onERC721Received.selector,
            _msgSender(),
            from,
            tokenId,
            _data
        ));
        if (!success) {
            if (returndata.length > 0) {
                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert("ERC721: transfer to non ERC721Receiver implementer");
            }
        } else {
            bytes4 retval = abi.decode(returndata, (bytes4));
            return (retval == _ERC721_RECEIVED);
        }
    }

    /**
     * @dev Private function to clear current approval of a given token ID.
     * @param tokenId uint256 ID of the token to be transferred
     */
    function _clearApproval(uint256 tokenId) private {
        if (_tokenApprovals[tokenId] != address(0)) {
            _tokenApprovals[tokenId] = address(0);
        }
    }
}

// File: @openzeppelin/contracts/token/ERC721/ERC721Enumerable.sol

pragma solidity ^0.5.0;





/**
 * @title ERC-721 Non-Fungible Token with optional enumeration extension logic
 * @dev See https://eips.ethereum.org/EIPS/eip-721
 */
contract ERC721Enumerable is Context, ERC165, ERC721, IERC721Enumerable {
    // Mapping from owner to list of owned token IDs
    mapping(address => 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;

    /*
     *     bytes4(keccak256('totalSupply()')) == 0x18160ddd
     *     bytes4(keccak256('tokenOfOwnerByIndex(address,uint256)')) == 0x2f745c59
     *     bytes4(keccak256('tokenByIndex(uint256)')) == 0x4f6ccce7
     *
     *     => 0x18160ddd ^ 0x2f745c59 ^ 0x4f6ccce7 == 0x780e9d63
     */
    bytes4 private constant _INTERFACE_ID_ERC721_ENUMERABLE = 0x780e9d63;

    /**
     * @dev Constructor function.
     */
    constructor () public {
        // register the supported interface to conform to ERC721Enumerable via ERC165
        _registerInterface(_INTERFACE_ID_ERC721_ENUMERABLE);
    }

    /**
     * @dev Gets the token ID at a given index of the tokens list of the requested owner.
     * @param owner address owning the tokens list to be accessed
     * @param index uint256 representing the index to be accessed of the requested tokens list
     * @return uint256 token ID at the given index of the tokens list owned by the requested address
     */
    function tokenOfOwnerByIndex(address owner, uint256 index) public view returns (uint256) {
        require(index < balanceOf(owner), "ERC721Enumerable: owner index out of bounds");
        return _ownedTokens[owner][index];
    }

    /**
     * @dev Gets the total amount of tokens stored by the contract.
     * @return uint256 representing the total amount of tokens
     */
    function totalSupply() public view returns (uint256) {
        return _allTokens.length;
    }

    /**
     * @dev Gets the token ID at a given index of all the tokens in this contract
     * Reverts if the index is greater or equal to the total number of tokens.
     * @param index uint256 representing the index to be accessed of the tokens list
     * @return uint256 token ID at the given index of the tokens list
     */
    function tokenByIndex(uint256 index) public view returns (uint256) {
        require(index < totalSupply(), "ERC721Enumerable: global index out of bounds");
        return _allTokens[index];
    }

    /**
     * @dev Internal function to transfer ownership of a given token ID to another address.
     * As opposed to transferFrom, this imposes no restrictions on msg.sender.
     * @param from current owner of the token
     * @param to address to receive the ownership of the given token ID
     * @param tokenId uint256 ID of the token to be transferred
     */
    function _transferFrom(address from, address to, uint256 tokenId) internal {
        super._transferFrom(from, to, tokenId);

        _removeTokenFromOwnerEnumeration(from, tokenId);

        _addTokenToOwnerEnumeration(to, tokenId);
    }

    /**
     * @dev Internal function to mint a new token.
     * Reverts if the given token ID already exists.
     * @param to address the beneficiary that will own the minted token
     * @param tokenId uint256 ID of the token to be minted
     */
    function _mint(address to, uint256 tokenId) internal {
        super._mint(to, tokenId);

        _addTokenToOwnerEnumeration(to, tokenId);

        _addTokenToAllTokensEnumeration(tokenId);
    }

    /**
     * @dev Internal function to burn a specific token.
     * Reverts if the token does not exist.
     * Deprecated, use {ERC721-_burn} instead.
     * @param owner owner of the token to burn
     * @param tokenId uint256 ID of the token being burned
     */
    function _burn(address owner, uint256 tokenId) internal {
        super._burn(owner, tokenId);

        _removeTokenFromOwnerEnumeration(owner, tokenId);
        // Since tokenId will be deleted, we can clear its slot in _ownedTokensIndex to trigger a gas refund
        _ownedTokensIndex[tokenId] = 0;

        _removeTokenFromAllTokensEnumeration(tokenId);
    }

    /**
     * @dev Gets the list of token IDs of the requested owner.
     * @param owner address owning the tokens
     * @return uint256[] List of token IDs owned by the requested address
     */
    function _tokensOfOwner(address owner) internal view returns (uint256[] storage) {
        return _ownedTokens[owner];
    }

    /**
     * @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 {
        _ownedTokensIndex[tokenId] = _ownedTokens[to].length;
        _ownedTokens[to].push(tokenId);
    }

    /**
     * @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 = _ownedTokens[from].length.sub(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
        _ownedTokens[from].length--;

        // Note that _ownedTokensIndex[tokenId] hasn't been cleared: it still points to the old slot (now occupied by
        // lastTokenId, or just over the end of the array if the token was the last one).
    }

    /**
     * @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.sub(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
        _allTokens.length--;
        _allTokensIndex[tokenId] = 0;
    }
}

// File: contracts/interface/IERC20.sol

pragma solidity ^0.5.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP. Does not include
 * the optional functions; to access them see {ERC20Detailed}.
 */
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);
    function mint(address account, uint amount) external;
    /**
     * @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: contracts/library/SafeERC20.sol

pragma solidity ^0.5.0;





/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for ERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
    using SafeMath for uint256;
    using Address for address;

    function safeTransfer(IERC20 token, address to, uint256 value) internal {
        callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }

    function safeTransferFrom(IERC20 token, address from, address to, uint256 value) internal {
        callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
    }

    function safeApprove(IERC20 token, address spender, uint256 value) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        // solhint-disable-next-line max-line-length
        require((value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }

    function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).add(value);
        callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).sub(value, "SafeERC20: decreased allowance below zero");
        callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves.

        // A Solidity high level call has three parts:
        //  1. The target address is checked to verify it contains contract code
        //  2. The call itself is made, and success asserted
        //  3. The return value is decoded, which in turn checks the size of the returned data.
        // solhint-disable-next-line max-line-length
        require(address(token).isContract(), "SafeERC20: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = address(token).call(data);
        require(success, "SafeERC20: low-level call failed");

        if (returndata.length > 0) { // Return data is optional
            // solhint-disable-next-line max-line-length
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}

// File: contracts/library/Governance.sol

pragma solidity ^0.5.0;

contract Governance {

    address public _governance;

    constructor() public {
        _governance = tx.origin;
    }

    event GovernanceTransferred(address indexed previousOwner, address indexed newOwner);

    modifier onlyGovernance {
        require(msg.sender == _governance, "not governance");
        _;
    }

    function setGovernance(address governance)  public  onlyGovernance
    {
        require(governance != address(0), "new governance the zero address");
        emit GovernanceTransferred(_governance, governance);
        _governance = governance;
    }


}

// File: contracts/interface/IPool.sol

pragma solidity ^0.5.0;


interface IPool {
    function totalSupply( ) external view returns (uint256);
    function balanceOf( address player ) external view returns (uint256);
}

// File: contracts/interface/IGegoToken.sol

pragma solidity ^0.5.0;



contract IGegoToken is IERC721 {

    struct GegoV1 {
        uint256 id;
        uint256 grade;
        uint256 quality;
        uint256 amount;
        uint256 resId;
        address author;
        uint256 createdTime;
        uint256 blockNum;
    }


    struct Gego {
        uint256 id;
        uint256 grade;
        uint256 quality;
        uint256 amount;
        uint256 resBaseId;
        uint256 tLevel;
        uint256 ruleId;
        uint256 nftType;
        address author;
        address erc20;
        uint256 createdTime;
        uint256 blockNum;
    }
    
    function mint(address to, uint256 tokenId) external returns (bool) ;
    function burn(uint256 tokenId) external;
}

// File: contracts/interface/IGegoFactoryV2.sol

pragma solidity ^0.5.0;

pragma experimental ABIEncoderV2;


interface IGegoFactoryV2 {


    function getGego(uint256 tokenId)
        external view
        returns (
            uint256 grade,
            uint256 quality,
            uint256 amount,
            uint256 resBaseId,
            uint256 tLevel,
            uint256 ruleId,
            uint256 nftType,
            address author,
            address erc20,
            uint256 createdTime,
            uint256 blockNum
        );


    function getGegoStruct(uint256 tokenId)
        external view
        returns (IGegoToken.Gego memory gego);

    function burn(uint256 tokenId) external returns ( bool );
    
    function isRulerProxyContract(address proxy) external view returns ( bool );
}

// File: contracts/reward/NFTRewardKCS.sol

pragma solidity ^0.5.0;




// gego







    
contract NFTRewardKCS is IPool,Governance {
    using SafeERC20 for IERC20;
    using SafeMath for uint256;

    IERC20 public _rewardToken = IERC20(0x0);
    IGegoFactoryV2 public _gegoFactory = IGegoFactoryV2(0x0);
    IGegoToken public _gegoToken = IGegoToken(0x0);

    uint256 public _startTime1 =  now + 365 days;
    uint256 public FINISHDURATION1 = 7 days;
    uint256 public _stageFinish1 = 0;
    uint256 public _rewardRate1 = 0;
    bool public _hasStart1 = false;
    uint256 public _startTime2 =  now + 365 days;
    uint256 public FINISHDURATION2 =  7 days;
    uint256 public _stageFinish2 = 0;
    uint256 public _rewardRate2 = 0;
    bool public _hasStart2 = false;
    uint256 public _initReward = 0;
    uint256 public _ruleId = 0;
    uint256 public _nftType = 0;
    uint256 public _lastUpdateTime;
    uint256 public _rewardPerTokenStored;
    mapping(address => uint256) public _userRewardPerTokenPaid;
    mapping(address => uint256) public _rewards;
    
    uint256 public _fixRateBase = 100000;
    
    uint256 public _totalWeight;
    mapping(address => uint256) public _weightBalances;

    mapping(address => uint256[]) public _playerGego;
    mapping(uint256 => uint256) public _gegoMapIndex;

    event RewardAdded(uint256 reward);
    event StakedGEGO(address indexed user, uint256 amount);
    event WithdrawnGego(address indexed user, uint256 amount);
    event RewardPaid(address indexed user, uint256 reward);
    event NFTReceived(address operator, address from, uint256 tokenId, bytes data);
    event SetStartTime(uint256 startTime);
    event FinishReward(uint256 reward);
    event StartReward(uint256 reward);

    modifier updateReward(address account) {
        _rewardPerTokenStored = rewardPerToken();
        _lastUpdateTime = lastTimeRewardApplicable();
        if (account != address(0)) {
            _rewards[account] = earned(account);
            _userRewardPerTokenPaid[account] = _rewardPerTokenStored;
        }
        _;
    }

    modifier checkOnRewardTime() {
        require((block.timestamp > _startTime1 && block.timestamp <= _stageFinish1)||(block.timestamp > _startTime2 && block.timestamp <= _stageFinish2), "not on stage");
        _;
    }

    constructor(address rewardToken, address gegoToken, address gegoFactory, uint256 ruleId, uint256 nftType) public {
        _rewardToken = IERC20(rewardToken);
        _gegoToken = IGegoToken(gegoToken);
        _gegoFactory = IGegoFactoryV2(gegoFactory);
        _ruleId = ruleId;
        _nftType = nftType;
    }

    function totalSupply()  public view returns (uint256) {
        return _totalWeight;
    }

    function balanceOf(address account) public view returns (uint256) {
        return _weightBalances[account];
    }

    /* Fee collection for any other token */
    function seize(IERC20 token, uint256 amount) external {
        require(token != _rewardToken, "reward");
        token.safeTransfer(_governance, amount);
    }
    
    /* Fee collection for any other token */
    function seizeErc721(IERC721 token, uint256 tokenId) external {
        require(token != _gegoToken, "reward");
        token.safeTransferFrom(address(this), _governance, tokenId);
    }

    // fix
    function rewardPerToken() public view returns (uint256) {
        if (totalSupply() == 0) {
            return _rewardPerTokenStored;
        }
        if (_lastUpdateTime <= _stageFinish1) {
            return
                _rewardPerTokenStored.add(
                    lastTimeRewardApplicable()
                        .sub(_lastUpdateTime)
                        .mul(_rewardRate1)
                        .mul(1e18)
                        .div(totalSupply())
                );
        }else{
            return
                _rewardPerTokenStored.add(
                    lastTimeRewardApplicable()
                        .sub(_lastUpdateTime)
                        .mul(_rewardRate2)
                        .mul(1e18)
                        .div(totalSupply())
                );
        }
    }

    function earned(address account) public view returns (uint256) {
        return
            balanceOf(account)
                .mul(rewardPerToken().sub(_userRewardPerTokenPaid[account]))
                .div(1e18)
                .add(_rewards[account]);
    }

    
    //the grade is a number between 1-6
    //the quality is a number between 1-10000
    /*
    1   quality	1.1+ 0.1*quality/5000
    2	quality	1.2+ 0.1*(quality-5000)/3000
    3	quality	1.3+ 0.1*(quality-8000/1000
    4	quality	1.4+ 0.2*(quality-9000)/800
    5	quality	1.6+ 0.2*(quality-9800)/180
    6	quality	1.8+ 0.2*(quality-9980)/20
    */

    function getFixRate(uint256 grade,uint256 quality) public pure returns (uint256){

        require(grade > 0 && grade <7, "the gego not token");

        uint256 unfold = 0;
        if( grade == 1 ){
            unfold = quality*10000/5000;
            return unfold.add(110000);
        }else if( grade == 2){
            unfold = quality.sub(5000)*10000/3000;
            return unfold.add(120000);
        }else if( grade == 3){
            unfold = quality.sub(8000)*10000/1000;
           return unfold.add(130000);
        }else if( grade == 4){
            unfold = quality.sub(9000)*20000/800;
           return unfold.add(140000);
        }else if( grade == 5){
            unfold = quality.sub(9800)*20000/180;
            return unfold.add(160000);
        }else{
            unfold = quality.sub(9980)*20000/20;
            return unfold.add(180000);
        }
    }

    function getStakeInfo( uint256 gegoId ) public view returns ( uint256 stakeRate, uint256 amount,uint256 ruleId,uint256 nftType){

        uint256 grade;
        uint256 quality; 
        (grade,quality,amount, , ,ruleId, nftType, , , , ) = _gegoFactory.getGego(gegoId);
        require(amount > 0,"the gego not token");
        stakeRate = getFixRate(grade,quality);
    }

    // stake GEGO 
    function stakeGego(uint256 gegoId)
        public
        updateReward(msg.sender)
        checkOnRewardTime
    {
        uint256[] storage gegoIds = _playerGego[msg.sender];
        if (gegoIds.length == 0) {
            gegoIds.push(0);    
            _gegoMapIndex[0] = 0;
        }
        gegoIds.push(gegoId);
        _gegoMapIndex[gegoId] = gegoIds.length - 1;

        uint256 stakeRate;
        uint256 ercAmount;
        uint256 ruleId;
        uint256 nftType;
        (stakeRate, ercAmount, ruleId, nftType) = getStakeInfo(gegoId);
        
        require(ruleId == _ruleId, "Not conforming to the rules");
        require(nftType == _nftType, "Not conforming to the rules");

        if(ercAmount > 0){
            uint256 stakeWeight = stakeRate.mul(ercAmount).div(_fixRateBase);
            _weightBalances[msg.sender] = _weightBalances[msg.sender].add(stakeWeight);
            _totalWeight = _totalWeight.add(stakeWeight);
        }

        _gegoToken.safeTransferFrom(msg.sender, address(this), gegoId);

        emit StakedGEGO(msg.sender, gegoId);
        
    }
    
    function onERC721Received(address operator, address from, uint256 tokenId, bytes memory data) public returns (bytes4) {
        // if(_hasStart1 == false && _hasStart2 == false) {
        //     return 0;
        // }

        emit NFTReceived(operator, from, tokenId, data);
        return bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"));
    }

    function withdrawGego(uint256 gegoId)
        public
        updateReward(msg.sender)
    {
        require(gegoId > 0, "the gegoId error");
        
        uint256[] memory gegoIds = _playerGego[msg.sender];
        uint256 gegoIndex = _gegoMapIndex[gegoId];
        
        require(gegoIds[gegoIndex] == gegoId, "not gegoId owner");

        uint256 gegoArrayLength = gegoIds.length-1;
        uint256 tailId = gegoIds[gegoArrayLength];

        _playerGego[msg.sender][gegoIndex] = tailId;
        _playerGego[msg.sender][gegoArrayLength] = 0;
        _playerGego[msg.sender].length--;
        _gegoMapIndex[tailId] = gegoIndex;
        _gegoMapIndex[gegoId] = 0;

        uint256 stakeRate;
        uint256 ercAmount;
        (stakeRate, ercAmount,,) = getStakeInfo(gegoId);
        uint256 stakeWeight = stakeRate.mul(ercAmount).div(_fixRateBase);
        _weightBalances[msg.sender] = _weightBalances[msg.sender].sub(stakeWeight);
        _totalWeight = _totalWeight.sub(stakeWeight);
        
        _gegoToken.safeTransferFrom(address(this), msg.sender, gegoId);

        emit WithdrawnGego(msg.sender, gegoId);
    }

    function withdraw()
        public
    {
        uint256[] memory gegoId = _playerGego[msg.sender];
        for (uint8 index = 1; index < gegoId.length; index++) {
            if (gegoId[index] > 0) {
                withdrawGego(gegoId[index]);
            }
        }
    }

    function getPlayerIds( address account ) public view returns( uint256[] memory gegoId )
    {
        gegoId = _playerGego[account];
    }

    function exit() external {
        withdraw();
        getReward();
    }

    function getReward() public updateReward(msg.sender) {
        uint256 reward = earned(msg.sender);
        if (reward > 0) {
            _rewards[msg.sender] = 0;
            _rewardToken.safeTransfer(msg.sender, reward);
            emit RewardPaid(msg.sender, reward);
        }
    }

    function lastTimeRewardApplicable() private view returns (uint256) {
        if (block.timestamp <= _stageFinish1) {
            return Math.min(block.timestamp, _stageFinish1);
        } else if ( _stageFinish1 < block.timestamp && block.timestamp <= _startTime2) {
            return _stageFinish1;
        } else {
            return Math.min(block.timestamp, _stageFinish2);
        }
    }
    
    
    //for extra reward
    function notifyRewardAmount(uint256 reward,uint256 duration, uint256 stage)
        external
        onlyGovernance
        updateReward(address(0))
    {
        if (stage == 1) {
            require(_hasStart1 == false, "stage1 has started");
            FINISHDURATION1 = duration;
        }else{
            require(_hasStart2 == false, "stage2 has started");
            FINISHDURATION2 = duration;
        }
        // uint256 balanceBefore = _rewardToken.balanceOf(address(this));
        // _rewardToken.safeTransferFrom(msg.sender, address(this), reward);
        // uint256 balanceEnd = _rewardToken.balanceOf(address(this));
        //_initReward = _initReward.add(balanceEnd.sub(balanceBefore));
        _initReward = reward; //balanceEnd.sub(balanceBefore);

        emit RewardAdded(_initReward);
    }


    // set fix time to start reward
    function startNFTReward(uint256 startTime, uint256 stage)
        external
        onlyGovernance
        updateReward(address(0))
    {
        if (stage == 1) {
            require(_hasStart1 == false, "stage1 has started");
            _hasStart1 = true;
            _startTime1 = startTime;    
            _stageFinish1 = startTime.add(FINISHDURATION1);
            _rewardRate1 = _initReward.div(FINISHDURATION1);
        } else {
            require(_hasStart2 == false, "stage2 has started");
            _hasStart2 = true;
            _startTime2 = startTime;    
            _stageFinish2 = startTime.add(FINISHDURATION2);
            _rewardRate2 = _initReward.div(FINISHDURATION2);
        }
        
        _lastUpdateTime = startTime;
        emit SetStartTime(startTime);
    }

    function setRuleId( uint256  ruleId) public onlyGovernance {
        _ruleId = ruleId;
    }

    function setNftType( uint256  nftType) public onlyGovernance {
        _nftType = nftType;
    }
}