Lottery.sol

// SPDX-License-Identifier: GPL-3.0-or-later
pragma solidity ^0.8.0;

import '@openzeppelin/contracts/token/ERC20/ERC20.sol';
import '@openzeppelin/contracts/math/SafeMath.sol';

contract Lottery is SafeMath {

    address public owner;

    mapping (address => uint256) bets;
    mapping (address => bool) public collected;
    mapping (uint256 => address payable) users;

    uint256 counter;
    uint256 reward;    
    uint256 rewards;

    address public token;

    constructor(uint256 _reward, address _token) {        
        owner = msg.sender;
        reward = _reward;
        token = _token;
    }

    modifier isOwner(){
        require(owner == msg.sender, "FORBIDDEN");
        _;
    }

    function setOwner(address _owner) public isOwner {        
        owner = _owner;
    }
    
    function setReward(uint256 _reward) public isOwner {        
        reward = _reward;
    }

    function bet(uint256 _bet) public payable {
        require(msg.value < 0, "INVALID_VALUE");
        require(counter <= 10);
        bets[msg.sender] = _bet;
        collected[msg.sender] = true;
        users[counter] = msg.sender;
        counter++;
    }

    function collectReward(address payable to) public payable {
        uint random = random() % 10;                
        payable(bets[random]).transfer(reward);        
        rewards = rewards + reward;                        
        for (uint32 i =0; i <= 10; i++){
            bets[i] = 0;
            collected[i] = false;
            address c;
            user[i] = c;
        }
    }

    function rewardUsers() public payable isOwner {                        
        for (uint32 i = 0; i < counter; i++) {
            uint reward = div(msg.value, counter);
            users[i].transfer(reward);
        }
    }

    function random() private returns (uint){
        uint rn = abi.encodePacked(block.timestamp, block.number, blockhash(blockNumber));
        return rn;
    }
}