voting.rho

/// @title Voting with delegation.

new Ballot,
trace(`rho:io:stderr`),
stdout(`rho:io:stdout`),
insertArbitrary(`rho:registry:insertArbitrary`)
in {
  new uriCh in {
    insertArbitrary!(*Ballot, *uriCh) | for(@uri <- uriCh) {
      stdout!(["#define $Ballot", uri])
    }
  }
  |

  // See example / demo below.
  contract Ballot(@{proposalNames /\ Set(hd, ...tail)}, return) = {
    new chairperson, winningProposalName, voterWeightCh, votedCh, countCh, delegateCh in {
      return!(bundle+{*chairperson}, bundle+{*winningProposalName}) |

      voterWeightCh!({}) | votedCh!({}) | countCh!({}) | delegateCh!({}) |

      contract chairperson(@"giveRightToVote", return) = {
        // "voter" is perhaps a mis-nomer. "votingRight" might be better.
        new voter in {
          trace!({"chair": *chairperson, "gives right to vote": *voter}) |
          return!(bundle+{*voter}) |

          for (@voterWeight <- voterWeightCh) {
            voterWeightCh!(voterWeight.set(bundle0{*voter}, 1))
          }|

          contract voter(@"vote", @proposal, eject, ack) = {
             trace!({"voter": *voter, "for": proposal}) |
            if(proposalNames.contains(proposal) == false) { eject!({"unknown proposal": proposal}) }
            else {
              trace!("valid proposal") |
              for (@votedFor <- votedCh) {
                if (votedFor.contains(bundle0{*voter})) {
                  votedCh!(votedFor) |
                  eject!("already voted")
                } else {
                  trace!("allowed to vote") |
                  for(@count <- countCh; @voterWeight <- voterWeightCh) {
                    trace!({"voter": *voter, "weight": voterWeight.get(bundle0{*voter}),
                      "proposal": proposal}) |
                    voterWeightCh!(voterWeight) |
                    ack!(Nil) |
                    votedCh!(votedFor.set(bundle0{*voter}, proposal)) |
                    countCh!(count.set(proposal,
                      count.getOrElse(proposal, 0) +
                        voterWeight.getOrElse(bundle0{*voter}, 0)))
                  }
                }
              }
            }
          } |
          contract voter(@"delegate", @to, eject, ack) = {
            // ISSUE: precedence of {bundle{}} around ==
            if ({bundle0{to}} == {bundle0{*voter}}) {
              eject!("Self-delegation is disallowed.")
            } else {
              for (@votedFor <- votedCh) {
                // trace!({"delegate already voted?": votedFor, "voter": *voter}) |
                votedCh!(votedFor) | // ISSUE: peek

                if(votedFor.contains(bundle0{*voter})) {
                  eject!("You already voted.")
                } else {
                  for (@delegateOf <- delegateCh) {
                    new loop, finish in {
                      loop!(bundle0{to}) |
                      contract loop(@whom) = {
                        // trace!({"delegate loop": whom}) |
                        if (whom == {bundle0{*voter}}) {
                          eject!("Found loop in delegation.") |
                          delegateCh!(delegateOf)
                        } else {
                          if (delegateOf.contains(whom)) {
                            loop!(delegateOf.get(whom))
                          } else {
                            finish!(whom)
                          }
                        }
                      } |
                      contract finish(@whom) = {
                        // trace!({"delegate finish": whom, "voter": *voter}) |
                        delegateCh!(delegateOf.set(bundle0{*voter}, whom)) |
                        ack!(Nil) |

                        for (@count <- countCh; @voterWeight <- voterWeightCh) {
                          if (votedFor.contains(whom)) {
                            trace!({"delegate already voted": whom}) |
                            // If the delegate already voted,
                            // directly add to the number of votes
                            countCh!(count.set(votedFor.get(whom),
                              count.getOrElse(votedFor.get(whom), 0) +
                                voterWeight.getOrElse(bundle0{*voter}, 1))) |
                            voterWeightCh!(voterWeight)
                          } else {
                            trace!({"add voter weight": voterWeight.get(bundle0{*voter}),
                              "to delegate weight": voterWeight.get(whom)}) |
                            // If the delegate did not vote yet,
                            // add to her weight.
                            voterWeightCh!(voterWeight.set(whom,
                              voterWeight.getOrElse(whom, 1) +
                                voterWeight.getOrElse(bundle0{*voter}, 1))) |
                            countCh!(count)
                          }
                        }
                      }
                    }
                  }
                }
              }
            }
          }
        }
      } |
      contract winningProposalName(return) = {
        for(@count <- countCh) {
          countCh!(count) |
          new loop in {
            contract loop(@best, @bestCount, @rest) = {
              match rest {
                Set() => { return!((best, count)) }
                Set(hd, ...tail) => {
                  if (count.getOrElse(hd, 0) > bestCount) {
                    loop!(hd, count.getOrElse(hd, 0), tail)
                  } else {
                    loop!(best, bestCount, tail)
                  }
                }
              }
            } |
            match proposalNames {
              Set(hd, ...tail) => { loop!(hd, count.getOrElse(hd, 0), tail) }
            }
          }
        }
      }
    }
  }
  |
  new bCh, v1Ch, v2Ch, v3Ch in {
    Ballot!(Set("Lincoln", "Douglas"), *bCh) |
    for (chairperson, winningProposalName <- bCh) {
      trace!({"Ballot returned": *chairperson}) |
      chairperson!("giveRightToVote", *v1Ch) |
      chairperson!("giveRightToVote", *v2Ch) |
      chairperson!("giveRightToVote", *v3Ch) |
      for(v1 <- v1Ch; v2 <- v2Ch; v3 <- v3Ch) {
        v3!("delegate", bundle0{*v2}, *trace, *v3Ch) |
        v3!("delegate", bundle0{*v3}, *trace, *v3Ch) |
        for(_ <- v3Ch) {
          v1!("vote", "Douglas", *trace, *v1Ch) |
          v1!("vote", "Lincoln", *trace, *v1Ch) |
          v1!("vote", "Abe Lincoln", *trace, *v1Ch) |
          v2!("vote", "Lincoln", *trace, *v2Ch) |
          for(_ <- v1Ch; _ <- v2Ch) {
            // trace!("votes done") |
            winningProposalName!(*bCh) |
            for(@w <- bCh) {
              trace!({"winner": w})
            }
          }
        }
      }
    }
  }
}


/*
pragma solidity >=0.4.22 <0.6.0;

contract Ballot {
    // This declares a new complex type which will
    // be used for variables later.
    // It will represent a single voter.
    struct Voter {
        uint weight; // weight is accumulated by delegation
        bool voted;  // if true, that person already voted
        address delegate; // person delegated to
        uint vote;   // index of the voted proposal
    }

    // This is a type for a single proposal.
    struct Proposal {
        bytes32 name;   // short name (up to 32 bytes)
        uint voteCount; // number of accumulated votes
    }

    address public chairperson;

    // This declares a state variable that
    // stores a `Voter` struct for each possible address.
    mapping(address => Voter) public voters;

    // A dynamically-sized array of `Proposal` structs.
    Proposal[] public proposals;

    /// Create a new ballot to choose one of `proposalNames`.
    constructor(bytes32[] memory proposalNames) public {
        chairperson = msg.sender;
        voters[chairperson].weight = 1;

        // For each of the provided proposal names,
        // create a new proposal object and add it
        // to the end of the array.
        for (uint i = 0; i < proposalNames.length; i++) {
            // `Proposal({...})` creates a temporary
            // Proposal object and `proposals.push(...)`
            // appends it to the end of `proposals`.
            proposals.push(Proposal({
                name: proposalNames[i],
                voteCount: 0
            }));
        }
    }

    // Give `voter` the right to vote on this ballot.
    // May only be called by `chairperson`.
    function giveRightToVote(address voter) public {
        // If the first argument of `require` evaluates
        // to `false`, execution terminates and all
        // changes to the state and to Ether balances
        // are reverted.
        // This used to consume all gas in old EVM versions, but
        // not anymore.
        // It is often a good idea to use `require` to check if
        // functions are called correctly.
        // As a second argument, you can also provide an
        // explanation about what went wrong.
        require(
            msg.sender == chairperson,
            "Only chairperson can give right to vote."
        );
        require(
            !voters[voter].voted,
            "The voter already voted."
        );
        require(voters[voter].weight == 0);
        voters[voter].weight = 1;
    }

    /// Delegate your vote to the voter `to`.
    function delegate(address to) public {
        // assigns reference
        Voter storage sender = voters[msg.sender];
        require(!sender.voted, "You already voted.");

        require(to != msg.sender, "Self-delegation is disallowed.");

        // Forward the delegation as long as
        // `to` also delegated.
        // In general, such loops are very dangerous,
        // because if they run too long, they might
        // need more gas than is available in a block.
        // In this case, the delegation will not be executed,
        // but in other situations, such loops might
        // cause a contract to get "stuck" completely.
        while (voters[to].delegate != address(0)) {
            to = voters[to].delegate;

            // We found a loop in the delegation, not allowed.
            require(to != msg.sender, "Found loop in delegation.");
        }

        // Since `sender` is a reference, this
        // modifies `voters[msg.sender].voted`
        sender.voted = true;
        sender.delegate = to;
        Voter storage delegate_ = voters[to];
        if (delegate_.voted) {
            // If the delegate already voted,
            // directly add to the number of votes
            proposals[delegate_.vote].voteCount += sender.weight;
        } else {
            // If the delegate did not vote yet,
            // add to her weight.
            delegate_.weight += sender.weight;
        }
    }

    /// Give your vote (including votes delegated to you)
    /// to proposal `proposals[proposal].name`.
    function vote(uint proposal) public {
        Voter storage sender = voters[msg.sender];
        require(sender.weight != 0, "Has no right to vote");
        require(!sender.voted, "Already voted.");
        sender.voted = true;
        sender.vote = proposal;

        // If `proposal` is out of the range of the array,
        // this will throw automatically and revert all
        // changes.
        proposals[proposal].voteCount += sender.weight;
    }

    /// @dev Computes the winning proposal taking all
    /// previous votes into account.
    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;
            }
        }
    }

    // Calls winningProposal() function to get the index
    // of the winner contained in the proposals array and then
    // returns the name of the winner
    function winnerName() public view
            returns (bytes32 winnerName_)
    {
        winnerName_ = proposals[winningProposal()].name;
    }
}
 */