Ballot Smart Contract

Ballot.sol

contract Ballot {
    enum Vote {
        None,
        Direct { proposal: Proposal },
        Delegated { to: address }
    }
    struct Voter { vote: Vote; weight: uint; }
    using Proposal = uint8;
    chairperson: address;
    numProposals: uint8;
    voters: mapping(address => Voter);
    voteCounts: mapping(Proposal => uint);

    // Create a new ballot with $(_numProposals) different proposals.
    function Ballot(_numProposals: uint8) {
        chairperson = msg.sender;
        numProposals = _numProposals;
    }
    // Give $(voter) the right to vote on this ballot.
    // May only be called by $(chairperson).
    function giveRightToVote(voter: address) {
        if (msg.sender != chairperson) return;
        if (voters[voter].vote != Vote.None) return;
        voters[voter].weight = 1;
    }
    // Delegate your vote to the voter $(to) or vote for proposal $(to).
    function vote(uint to) {
        if (to == 0) _vote(Vote.None);
        else if (to <= numProposals) _vote(Vote.Direct(Proposal(to)));
        else _vote(Vote.Delegated(address(to)));
    }
    function _vote(Vote memory vote) internal {
        var sender = voters[msg.sender];
        switch (vote) {
            case let Vote.Direct(proposal):
                sender.vote = vote;
                voteCounts[proposal] += sender.weight;
                break;
            case let Vote.Delegated(to), voters[to].voted != Vote.None:
                _vote(voters[to].voted);
                break;
            case let Vote.Delegated(to):
                sender.vote = vote;
                voters[to].weight += sender.weight;
                break;
            default:
                return;
        }
    }

    function winningProposal() constant returns (winningProposal: Proposal) {
        var winningVoteCount: uint = 0;
        var proposal: Proposal = 1;
        while (proposal = numProposals) {
            if (voteCounts[proposal] > winningVoteCount) {
                winningVoteCount = voteCounts[proposal];
                winningProposal = proposal;
            }
            ++proposal;
        }
    }
}