airdrop.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.4;
import "@openzeppelin/contracts/token/ERC721/IERC721Receiver.sol";

interface KittensHD {
  function getGeneralMintCounter() external returns (uint256);

  function getPrice(uint256 quantity) external returns (uint256);

  function unpauseMinting() external;

  function pauseMinting() external;

  function daoAnyClaim(uint256 quantity) external;

  function safeTransferFrom(
    address a,
    address b,
    uint256 tokenId
  ) external;
}

contract Airdrop is IERC721Receiver {
  KittensHD public kittensHD;
  address public owner;

  constructor(address kittensHDAddress) {
    owner = msg.sender;
    kittensHD = KittensHD(kittensHDAddress);
  }

  function airdrop(address[] memory holders, uint256 amountEach) external {
    require(msg.sender == owner, "not owner");

    for (uint256 i = 0; i < holders.length; i++) {
      if(!isContract(holders[i])) {
        uint256 currentIndex = kittensHD.getGeneralMintCounter();
        kittensHD.daoAnyClaim(amountEach);
        for (uint256 j = 0; j < amountEach; j++) {
          kittensHD.safeTransferFrom(address(this), holders[i], j + currentIndex);
        }
      }
    }
  }

  function isContract(address addr) internal returns (bool) {
    uint size;
    assembly { size := extcodesize(addr) }
    return size > 0;
  }

  function onERC721Received(
    address operator,
    address from,
    uint256 tokenId,
    bytes calldata data
  ) external override returns (bytes4) {
    return this.onERC721Received.selector;
  }
}