// SPDX-License-Identifier: MIT LICENSE


/*

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THIS CONTRACT IS AVAILABLE FOR EDUCATIONAL 
PURPOSES ONLY. YOU ARE SOLELY REPONSIBLE 
FOR ITS USE. I AM NOT RESPONSIBLE FOR ANY
OTHER USE. THIS IS TRAINING/EDUCATIONAL
MATERIAL. ONLY USE IT IF YOU AGREE TO THE
TERMS SPECIFIED ABOVE.
*/
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/utils/math/SafeMath.sol";
import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import "@openzeppelin/contracts/token/ERC20/extensions/ERC20Burnable.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/access/AccessControl.sol";


pragma solidity ^0.8.7;

contract N2D is ERC20, ERC20Burnable, Ownable, AccessControl {
  using SafeMath for uint256;

  mapping(address => uint256) private _balances;

  uint256 private _totalSupply;
  uint256 private MAXSUP;
  uint256 constant MAXIMUMSUPPLY=1000000000*10**18;

  bytes32 public constant MINTER_ROLE = keccak256("MINTER_ROLE");

  constructor() ERC20("N2D Rewards", "N2DR") {
        _setupRole(DEFAULT_ADMIN_ROLE, _msgSender());
        _setupRole(MINTER_ROLE, _msgSender());
      }

  function mint(address to, uint256 amount) external {
    require(hasRole(MINTER_ROLE, _msgSender()), "Not allowed to mint");
    require((MAXSUP+amount)<=MAXIMUMSUPPLY,"Maximum supply has been reached");
    _totalSupply = _totalSupply.add(amount);
    MAXSUP=MAXSUP.add(amount);
    _balances[to] = _balances[to].add(amount);
    _mint(to, amount);
  }

  function burnFrom(address account, uint256 amount) public override {
      if (hasRole(MINTER_ROLE, _msgSender())) {
          _burn(account, amount);
      }
      else {
          super.burnFrom(account, amount);
      }
  }
  
  function totalSupply() public override view returns (uint256) {
    return _totalSupply;
  }

  function maxSupply() public  pure returns (uint256) {
    return MAXIMUMSUPPLY;
  }

}