pragma solidity ^0.5.2;

contract Ballot {
    struct Voter {
        uint weight;
        bool voted;
        address delegate;
        uint vote;
    }

    struct Proposal {
        bytes32 name;
        uint voteCount;
    }

    address public chairperson;
    mapping(address => Voter) public voters;
    Proposal[] public proposals;

    constructor (bytes32[] memory proposalNames) public {
        chairperson = msg.sender;
        voters[chairperson].weight = 1;

        for (uint i = 0; i < proposalNames.length; i++) {
            proposals.push(Proposal({
                name: proposalNames[i],
                voteCount: 0
            }));
        }
    }

    function giveRightToVote(address voter) public {
        require(
            (msg.sender == chairperson) &&
            !voters[voter].voted &&
            (voters[voter].weight == 0)
        );
        voters[voter].weight = 1;
    }

    function delegate(address to) public {
        Voter storage sender = voters[msg.sender];
        require(!sender.voted);

        require(to != msg.sender);

        while (voters[to].delegate != address(0)) {
            to = voters[to].delegate;

            require(to != msg.sender);
        }

        sender.voted = true;
        sender.delegate = to;
        Voter storage delegate_ = voters[to];
        if (delegate_.voted) {
            proposals[delegate_.vote].voteCount += sender.weight;
        } else {
            delegate_.weight += sender.weight;
        }
    }

    function vote(uint proposal) public {
        Voter storage sender = voters[msg.sender];
        require(!sender.voted);
        sender.voted = true;
        sender.vote = proposal;

        proposals[proposal].voteCount += sender.weight;
    }

    function winningProposal() public view
            returns (uint winningProposal_)
    {
        uint winningVoteCount = 0;
        for (uint p = 0; p < proposals.length; p++) {
            if (proposals[p].voteCount > winningVoteCount) {
                winningVoteCount = proposals[p].voteCount;
                winningProposal_ = p;
            }
        }
    }

    function winnerName() public view
            returns (bytes32 winnerName_)
    {
        winnerName_ = proposals[winningProposal()].name;
    }
}