/**
 *Submitted for verification at Etherscan.io on 2021-12-29
*/

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/math/SafeMath.sol)

pragma solidity ^0.8.0;

// CAUTION
// This version of SafeMath should only be used with Solidity 0.8 or later,
// because it relies on the compiler's built in overflow checks.

/**
 * @dev Wrappers over Solidity's arithmetic operations.
 *
 * NOTE: `SafeMath` is generally not needed starting with Solidity 0.8, since the compiler
 * now has built in overflow checking.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            uint256 c = a + b;
            if (c < a) return (false, 0);
            return (true, c);
        }
    }

    /**
     * @dev Returns the substraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            if (b > a) return (false, 0);
            return (true, a - b);
        }
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            // 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 (true, 0);
            uint256 c = a * b;
            if (c / a != b) return (false, 0);
            return (true, c);
        }
    }

    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            if (b == 0) return (false, 0);
            return (true, a / b);
        }
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            if (b == 0) return (false, 0);
            return (true, a % b);
        }
    }

    /**
     * @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) {
        return a + b;
    }

    /**
     * @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 a - b;
    }

    /**
     * @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) {
        return a * b;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator.
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting 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 a % b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        unchecked {
            require(b <= a, errorMessage);
            return a - b;
        }
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting 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.
     */
    function div(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        unchecked {
            require(b > 0, errorMessage);
            return a / b;
        }
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * 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,
        string memory errorMessage
    ) internal pure returns (uint256) {
        unchecked {
            require(b > 0, errorMessage);
            return a % b;
        }
    }
}

// OpenZeppelin Contracts v4.4.1 (utils/Context.sol)

pragma solidity ^0.8.0;

/**
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }
}

// OpenZeppelin Contracts v4.4.1 (access/Ownable.sol)

pragma solidity ^0.8.0;


/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor() {
        _transferOwnership(_msgSender());
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
        _;
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        _transferOwnership(address(0));
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }

}


pragma solidity ^0.8.0;

/**
 * @title ERC721 token receiver interface
 * @dev Interface for any contract that wants to support safeTransfers
 * from ERC721 asset contracts.
 */
interface IERC721Receiver {
    /**
     * @dev Whenever an {IERC721} `tokenId` token is transferred to this contract via {IERC721-safeTransferFrom}
     * by `operator` from `from`, this function is called.
     *
     * It must return its Solidity selector to confirm the token transfer.
     * If any other value is returned or the interface is not implemented by the recipient, the transfer will be reverted.
     *
     * The selector can be obtained in Solidity with `IERC721.onERC721Received.selector`.
     */
    function onERC721Received(
        address operator,
        address from,
        uint256 tokenId,
        bytes calldata data
    ) external returns (bytes4);
}

// OpenZeppelin Contracts v4.4.1 (utils/introspection/IERC165.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC165 standard, as defined in the
 * https://eips.ethereum.org/EIPS/eip-165[EIP].
 *
 * Implementers can declare support of contract interfaces, which can then be
 * queried by others ({ERC165Checker}).
 *
 * For an implementation, see {ERC165}.
 */
interface IERC165 {
    /**
     * @dev Returns true if this contract implements the interface defined by
     * `interfaceId`. See the corresponding
     * https://eips.ethereum.org/EIPS/eip-165#how-interfaces-are-identified[EIP section]
     * to learn more about how these ids are created.
     *
     * This function call must use less than 30 000 gas.
     */
    function supportsInterface(bytes4 interfaceId) external view returns (bool);
}


// OpenZeppelin Contracts v4.4.1 (token/ERC721/IERC721.sol)

pragma solidity ^0.8.0;


/**
 * @dev Required interface of an ERC721 compliant contract.
 */
interface IERC721 is IERC165 {
    /**
     * @dev Emitted when `tokenId` token is transferred from `from` to `to`.
     */
    event Transfer(address indexed from, address indexed to, uint256 indexed tokenId);

    /**
     * @dev Emitted when `owner` enables `approved` to manage the `tokenId` token.
     */
    event Approval(address indexed owner, address indexed approved, uint256 indexed tokenId);

    /**
     * @dev Emitted when `owner` enables or disables (`approved`) `operator` to manage all of its assets.
     */
    event ApprovalForAll(address indexed owner, address indexed operator, bool approved);

    /**
     * @dev Returns the number of tokens in ``owner``'s account.
     */
    function balanceOf(address owner) external view returns (uint256 balance);

    /**
     * @dev Returns the owner of the `tokenId` token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function ownerOf(uint256 tokenId) external view returns (address owner);

    /**
     * @dev Safely transfers `tokenId` token from `from` to `to`, checking first that contract recipients
     * are aware of the ERC721 protocol to prevent tokens from being forever locked.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must exist and be owned by `from`.
     * - If the caller is not `from`, it must be have been allowed to move this token by either {approve} or {setApprovalForAll}.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId
    ) external;

    /**
     * @dev Transfers `tokenId` token from `from` to `to`.
     *
     * WARNING: Usage of this method is discouraged, use {safeTransferFrom} whenever possible.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must be owned by `from`.
     * - If the caller is not `from`, it must be approved to move this token by either {approve} or {setApprovalForAll}.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(
        address from,
        address to,
        uint256 tokenId
    ) external;

    /**
     * @dev Gives permission to `to` to transfer `tokenId` token to another account.
     * The approval is cleared when the token is transferred.
     *
     * Only a single account can be approved at a time, so approving the zero address clears previous approvals.
     *
     * Requirements:
     *
     * - The caller must own the token or be an approved operator.
     * - `tokenId` must exist.
     *
     * Emits an {Approval} event.
     */
    function approve(address to, uint256 tokenId) external;

    /**
     * @dev Returns the account approved for `tokenId` token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function getApproved(uint256 tokenId) external view returns (address operator);

    /**
     * @dev Approve or remove `operator` as an operator for the caller.
     * Operators can call {transferFrom} or {safeTransferFrom} for any token owned by the caller.
     *
     * Requirements:
     *
     * - The `operator` cannot be the caller.
     *
     * Emits an {ApprovalForAll} event.
     */
    function setApprovalForAll(address operator, bool _approved) external;

    /**
     * @dev Returns if the `operator` is allowed to manage all of the assets of `owner`.
     *
     * See {setApprovalForAll}
     */
    function isApprovedForAll(address owner, address operator) external view returns (bool);

    /**
     * @dev Safely transfers `tokenId` token from `from` to `to`.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must exist and be owned by `from`.
     * - If the caller is not `from`, it must be approved to move this token by either {approve} or {setApprovalForAll}.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId,
        bytes calldata data
    ) external;
}

contract KnightStaking is IERC721Receiver, Ownable {
  using SafeMath for uint256;
  bytes4 private constant _ERC721_RECEIVED = 0x150b7a02;

  event RewardAdded(uint256 time, uint256 rewardAmount);
  event RewardClaimed(uint256 tokenID, address owner);

  event Staked(address staker, uint256 tokenID, uint256 stakedTime);
  event UnStaked(uint256 tokenID, uint256 unstakedTime);

  /*
  Used to store the information of the Staked NFT.
  */
  struct StakedNFT{
    uint256 startTime;
    uint256 claimableReward;
    address staker;
    bool isStaked;
    uint256 lastClaims;
  }

  //staked tokenID list 
  uint256[] public stakedNFTs;
  //maps tokenID => Staked NFT
  mapping(uint256 => StakedNFT) public stakedInfo;
  //nft address
  address public nft;

  constructor(address _nft){
    nft = _nft;
  }

  /*
  Handle the eth receive function 
  */
  receive() external payable{
    addReward();
  }

  // reward = ( YourNFTStakedTime / TotalNFTStakedTime ) * AmountDistributed 
  function addReward() public payable{
    if(msg.value>0){
        //perform distribution
        uint256 totalTime = 0;
        for(uint256 i=0; i < stakedNFTs.length ; i++){
            StakedNFT memory staked = stakedInfo[stakedNFTs[i]];
            totalTime += block.timestamp.sub(staked.startTime);
        }
        for(uint256 i=0; i< stakedNFTs.length; i++){
            StakedNFT storage _stakedInfo = stakedInfo[stakedNFTs[i]];
            uint256 timeSpan = block.timestamp.sub(_stakedInfo.startTime);
            uint256 reward = timeSpan.mul(msg.value).div(totalTime);
            _stakedInfo.startTime = block.timestamp;
            _stakedInfo.claimableReward = reward; 
        }
        emit RewardAdded(block.timestamp, msg.value);
    }
   
  }

  function batchStakeNFT(uint256[] memory tokenIDs) external{
      uint256 tokenID = 0;
      for(uint256 i=0; i<tokenIDs.length; i++){
         tokenID = tokenIDs[i];
         require(IERC721(nft).ownerOf(tokenID)==msg.sender, "Staking: Not the NFT owner!");
         require(IERC721(nft).isApprovedForAll(msg.sender, address(this)), "Staking:Staking contract not set as operator!");
        IERC721(nft).safeTransferFrom(msg.sender, address(this), tokenID);
        _stakeNFT(tokenID);
      }
  }

  function stakeNFT(uint256 tokenID) public {
    require(IERC721(nft).ownerOf(tokenID)==msg.sender, "Staking: Not the NFT owner!");
    require(
        address(this) == IERC721(nft).getApproved(tokenID) || IERC721(nft).isApprovedForAll(msg.sender, address(this)), 
        "Staking: NFT not approved for the staking address OR Staking contract not set as operator!"
    );
    IERC721(nft).safeTransferFrom(msg.sender, address(this), tokenID);
    _stakeNFT(tokenID);
  }

  function _stakeNFT(uint256 _tokenID) internal{
    stakedNFTs.push(_tokenID);

    if(hasNFTData(_tokenID)){
      StakedNFT storage stakedNFT = stakedInfo[_tokenID];
      require(!stakedNFT.isStaked, "Staking: NFT already staked!");
      stakedNFT.staker = msg.sender;
      stakedNFT.startTime = block.timestamp;
      stakedNFT.isStaked = true;
    }
    else{
      StakedNFT memory stakedNFT = StakedNFT({
        startTime: block.timestamp,
        claimableReward: 0,
        staker: msg.sender,
        isStaked: true,
        lastClaims: 0
      });
      stakedInfo[_tokenID] = stakedNFT;
    }
    emit Staked(msg.sender, _tokenID, block.timestamp);
  }

  function batchUnStakeNFT(uint256[] memory tokenIDs) external{
      uint256 tokenID = 0;
      for(uint256 i=0; i<tokenIDs.length; i++){
         tokenID = tokenIDs[i];
         claimReward(tokenID);
         IERC721(nft).safeTransferFrom(address(this), msg.sender, tokenID);
         _unstakeNFT(tokenID);
      }
  }

  function unstakeNFT(uint256 tokenID) public {
    claimReward(tokenID);
    IERC721(nft).safeTransferFrom(address(this), msg.sender, tokenID);
    _unstakeNFT(tokenID);
  }

  function _unstakeNFT(uint256 _tokenID) internal {
    StakedNFT storage stakedNFT = stakedInfo[_tokenID];
    require(stakedNFT.isStaked, "Staking: NFT not staked!");
    require(stakedNFT.staker == msg.sender, "Staking: Not the owner of NFT!");

    stakedNFT.isStaked = false;
    stakedNFT.startTime = 0;

    uint256 size = stakedNFTs.length;
    uint256 lastElement = stakedNFTs[size-1];
    stakedNFTs.pop();


    emit UnStaked(_tokenID, block.timestamp);

    for(uint256 i=0; i< size-1 ; i++){
      if(stakedNFTs[i] ==_tokenID){
        stakedNFTs[i] = lastElement;
        return;
      }
    }

  }

  function hasNFTData(uint256 _tokenID) internal view returns(bool){
    if(stakedInfo[_tokenID].staker != address(0)){
      return true;
    }
    return false;
  }

  function claimReward(uint256 tokenID) public{
    StakedNFT storage stakedNFT = stakedInfo[tokenID];
    require(stakedNFT.staker == msg.sender, "Staking: Not the NFT owner");
    uint256 claimableEth = stakedNFT.claimableReward;
    stakedNFT.claimableReward = 0;
    stakedNFT.lastClaims = block.timestamp;
    stakedNFT.startTime = block.timestamp;
    if(claimableEth>0){
      withdrawEth(claimableEth);
    }
  }

  function withdrawEth(uint256 amount) internal{
    (bool os, ) = payable(msg.sender).call{value: amount}("");
    require(os);
  }

  // getters
  function getClaimableEth(uint256 tokenID) external view returns(uint256 ethValue){
    return stakedInfo[tokenID].claimableReward;
  }

  function getStakedNFTInfo(uint256 tokenID) external view returns(StakedNFT memory stakedNft){
    stakedNft = stakedInfo[tokenID];
  }

  function getStakedTime(uint256 tokenID) external view returns(uint256 startTime){
    startTime = stakedInfo[tokenID].startTime;
  }

  function getStakedInfo(uint256 tokenID) external view returns(StakedNFT memory nftInfo){
    nftInfo = stakedInfo[tokenID];
  }

  /*
  Handle the ERC721 recieve.
  */
    function onERC721Received(
        address,
        address,
        uint256,
        bytes calldata data
    )
        public override returns(bytes4)
    {
        return _ERC721_RECEIVED;
    }


  //ERC721 support 
  function supportsInterface(bytes4 interfaceID) external returns (bool){
   
    return interfaceID == _ERC721_RECEIVED ;
  }

}