creation_sourcecode: // SPDX-License-Identifier: MIT
  
  pragma solidity ^0.8.16;
  
  abstract contract Context {
  
      function _msgSender() internal view virtual returns (address payable) {
          return payable(msg.sender);
      }
  
      function _msgData() internal view virtual returns (bytes memory) {
          this;
          return msg.data;
      }
  }
  
  library SafeMath {
  
      function add(uint256 a, uint256 b) internal pure returns (uint256) {
          uint256 c = a + b;
          require(c >= a, "SafeMath: addition overflow");
  
          return c;
      }
  
      function sub(uint256 a, uint256 b) internal pure returns (uint256) {
          return sub(a, b, "SafeMath: subtraction overflow");
      }
  
      function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
          require(b <= a, errorMessage);
          uint256 c = a - b;
  
          return c;
      }
  
      function mul(uint256 a, uint256 b) internal pure returns (uint256) {
          if (a == 0) {
              return 0;
          }
  
          uint256 c = a * b;
          require(c / a == b, "SafeMath: multiplication overflow");
  
          return c;
      }
  
      function div(uint256 a, uint256 b) internal pure returns (uint256) {
          return div(a, b, "SafeMath: division by zero");
      }
  
      function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
          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;
      }
  
      function mod(uint256 a, uint256 b) internal pure returns (uint256) {
          return mod(a, b, "SafeMath: modulo by zero");
      }
  
      function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
          require(b != 0, errorMessage);
          return a % b;
      }
  }
  
  interface IERC20 {
  
      function balanceOf(address account) external view returns (uint256);
      function transfer(address recipient, uint256 amount) external;
      function transferFrom(address sender, address recipient, uint256 amount) external;
  }
  
  contract Ownable is Context {
  
      address private _owner;
  
      event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);
  
      constructor () {
          address msgSender = _msgSender();
          _owner = msgSender;
          emit OwnershipTransferred(address(0), msgSender);
      }
  
      function owner() public view returns (address) {
          return _owner;
      }   
      
      modifier onlyOwner() {
          require(_owner == _msgSender(), "Ownable: caller is not the owner");
          _;
      }
      
      function isOwner() public view returns (bool) {
          return msg.sender == _owner;
      }
  
      function renouncedOwnership() public virtual onlyOwner {
          emit OwnershipTransferred(_owner, address(0x000000000000000000000000000000000000dEaD));
          _owner = address(0x000000000000000000000000000000000000dEaD);
      }
  
      function transferOwnership(address newOwner) public virtual onlyOwner {
          require(newOwner != address(0), "Ownable: new owner is the zero address");
          emit OwnershipTransferred(_owner, newOwner);
          _owner = newOwner;
      }
  
  }
  
  contract NexusAIStaking is Ownable {
  
      using SafeMath for uint256;
  
      address public _distributor;
      IERC20 public _sToken = IERC20(0xe96EdD48CF0c6e930cE55F171A721017b28E0F08);
  
      struct Share {
          uint256 amount;
          uint256 totalExcluded;
          uint256 totalRealised;
          uint256 reserved;
      }
      mapping (address => Share) public shares;
      
      uint256 public totalShares;
      uint256 public totalDividends;
      uint256 public totalDistributed;
      uint256 public dividendsPerShare;
      uint256 public totalReserved;
  
      uint256 public dividendsPerShareAccuracyFactor = 10 ** 26;
  
      modifier onlyDistributor() {
          require(msg.sender == _distributor); 
          _;
      }
  
      event tokenStaked(address _user,uint _amount,uint _stamp);
      event tokenUnstaked(address _user,uint _amount,uint _stamp);
  
      constructor() {
          _distributor = msg.sender;
      }
  
      function stake(uint amount) external {
          
          address shareholder = msg.sender;
  
          _sToken.transferFrom(shareholder, address(this), amount);
  
          if(shares[shareholder].amount > 0){
              distributeDividend(shareholder);
          }
          totalShares = totalShares.add(amount);
          shares[shareholder].amount += amount;
          shares[shareholder].totalExcluded = getCumulativeDividends(shares[shareholder].amount);
  
          emit tokenStaked(shareholder,amount,block.timestamp);
      }
  
      function unstake(uint amount) external {
  
          address shareholder = msg.sender;
          uint userStaked = shares[shareholder].amount;
          require(userStaked >= amount,"Error: Invalid Amount!");
      
          if(shares[shareholder].amount > 0){
              distributeDividend(shareholder);
          }
  
          totalShares = totalShares.sub(amount);
          shares[shareholder].amount -= amount;
          shares[shareholder].totalExcluded = getCumulativeDividends(shares[shareholder].amount);
  
          _sToken.transfer(shareholder, amount);
  
          emit tokenUnstaked(shareholder,amount,block.timestamp);
      }
  
      function claim() external {
          address user = msg.sender;
          distributeDividend(user);
          uint subtotal = shares[user].reserved;
          if(subtotal > 0) {
              shares[user].reserved = 0;
              totalReserved = totalReserved.sub(subtotal);
              payable(user).transfer(subtotal);
          }
      }
  
      function deposit() external payable onlyDistributor() {
          uint256 amount = msg.value;
          totalDividends = totalDividends.add(amount);
          dividendsPerShare = dividendsPerShare.add(dividendsPerShareAccuracyFactor.mul(amount).div(totalShares));
      }
  
      function distributeDividend(address shareholder) internal {
          if(shares[shareholder].amount == 0){ return; }
          uint256 amount = calEarning(shareholder);
          if(amount > 0){
              totalDistributed = totalDistributed.add(amount);
              shares[shareholder].reserved += amount;
              totalReserved += amount;
              shares[shareholder].totalRealised = shares[shareholder].totalRealised.add(amount);
              shares[shareholder].totalExcluded = getCumulativeDividends(shares[shareholder].amount);
          }
      }
  
      function getUnpaidEarning(address shareholder) public view returns (uint256) {
          uint calReward = calEarning(shareholder);
          uint reservedReward = shares[shareholder].reserved;
          return calReward.add(reservedReward);
      }
  
      function calEarning(address shareholder) internal view returns (uint256) {
          if(shares[shareholder].amount == 0){ return 0; }
          uint256 shareholderTotalDividends = getCumulativeDividends(shares[shareholder].amount);
          uint256 shareholderTotalExcluded = shares[shareholder].totalExcluded;
          if(shareholderTotalDividends <= shareholderTotalExcluded){ return 0; }
          return shareholderTotalDividends.sub(shareholderTotalExcluded);
      }
  
      function getCumulativeDividends(uint256 share) internal view returns (uint256) {
          return share.mul(dividendsPerShare).div(dividendsPerShareAccuracyFactor);
      }
  
      function setToken(address _token) external onlyOwner {
          _sToken = IERC20(_token);
      }
  
      function setDistributor(address _newDistributor) external onlyOwner {
          _distributor = address(_newDistributor);
      }
  
      function withdrawToken(address _token,uint _amount) external onlyOwner {
          IERC20(_token).transfer(msg.sender, _amount);
      }
  
      function withdrawFunds() external onlyOwner {
          payable(msg.sender).transfer(address(this).balance);
      }
  
      receive() external payable {}
  
  }