pragma solidity ^0.6.1;

contract Lottery{

    address public manager;

    address payable[] public players;

    uint public playersCounter;

    uint public maxPlayersNumbers;

    event PlayerJoined(address player);
    event PlayerWon(address player, uint amount);

    constructor(uint playersNumber) public {
        maxPlayersNumbers = playersNumber;
        manager = msg.sender;
    }

    function join() payable public {
        require(msg.value >= .1 ether);

        players.push(msg.sender);
        playersCounter++;

        emit PlayerJoined(msg.sender);

        if (playersCounter >= maxPlayersNumbers) {
            drawWinner();
        }
    }

    function getPlayers() public view returns (address payable[] memory){
        return players;
    }

    function forceDrawing() public onlyManager{
        require(msg.sender == manager);

        drawWinner();
    }

    modifier onlyManager {
        require(msg.sender == manager);
        _;
    }

    function drawWinner() private {
        uint index = random() % players.length;
        uint amount = address(this).balance;

        address payable winner = players[index];
        winner.transfer(amount);

        players = new address payable[](0);
        playersCounter = 0;

        emit PlayerWon(winner, amount);

    }

    function random() private view returns (uint) {
        return uint(keccak256(
            abi.encodePacked(block.difficulty, now, players)));

    }

}