Lottery.sol

// SPDX-License-Identifier: GPL-3.0

pragma solidity >=0.8.2 <0.9.0;

contract Lottery {
    address public manager;
    address payable[] public candidates;
    address payable public winner;

    constructor(){
        manager = msg.sender;
    }

    receive() external payable {
        require(msg.value == 1 ether);
        candidates.push(payable(msg.sender));
    }

    function getBalance() public view returns(uint){
        require(msg.sender == manager);
        return address(this).balance;
    }

    function getRandom() public view returns(uint){
       return uint(keccak256(abi.encodePacked(block.prevrandao, block.timestamp, candidates.length)));
    }

    function PickWinner() public {
        require(msg.sender == manager);
        require(candidates.length >= 2);
        uint r = getRandom();
        uint index = r%candidates.length;
        winner = candidates[index];
        winner.transfer(getBalance());
        candidates = new address payable [](0);
    }
}