topic-democracy/contracts/democracy/Proposal.sol

pragma solidity >=0.5.0 <0.6.0;

import "../common/Controlled.sol";
import "../common/MessageSigned.sol";
import "../common/MerkleProof.sol";
import "../token/MiniMeToken.sol";
import "./Delegation.sol";
import "./TrustNetworkInterface.sol";

/**
 * @title Proposal
 * @author Ricardo Guilherme Schmidt (Status Research & Development GmbH)
 * Store votes and tabulate results for Democracy  
 */
contract Proposal is Controlled, MessageSigned {
    MiniMeToken public token;
    Delegation public delegation;
    uint256 public tabulationBlockDelay;
    
    bytes32 topic; 
    bytes32 txHash;
    uint blockStart;
    uint voteBlockEnd;

    //votes storage
    bytes32[] signatures;
    mapping(address => Vote) voteMap;

    //tabulation process 
    uint256 lastTabulationBlock;
    mapping(address => address) delegationOf;
    mapping(address => address) tabulated;
    mapping(uint8 => uint256) results;

    Vote result;
    

    enum Vote { 
        Null,
        Reject, 
        Approve
    }

    constructor(
        MiniMeToken _token,
        Delegation _delegation,
        bytes32 _topic,
        bytes32 _txHash,
        uint256 _tabulationBlockDelay,
        uint256 _blockStart,
        uint256 _blockEndDelay
    ) 
        public

    {
        delegation = _delegation;
        token = _token;
        tabulationBlockDelay = _tabulationBlockDelay;
        topic = _topic;
        txHash = _txHash;
        blockStart = _blockStart;
        voteBlockEnd = blockStart + _blockEndDelay;
    }

    function addVotes(bytes32 _signatures)
        external
    {
        require(block.number >= blockStart, "Voting not started");
        require(block.number <= voteBlockEnd, "Voting ended");
        signatures.push(_signatures);
    } 

    function tabulateSigned(Vote _vote, uint256 _position, bytes32[] calldata _proof, bytes calldata _signature) 
        external
    {
        require(block.number > voteBlockEnd, "Voting running");
        require(MerkleProof.verifyProof(_proof, signatures[_position], keccak256(_signature)), "Invalid proof");
        address _voter = recoverAddress(keccak256(abi.encodePacked(address(this), _vote)), _signature);
        require(voteMap[_voter] == Vote.Null, "Already tabulated");
        voteMap[_voter] = _vote;
        setTabulation(_voter, _voter, _vote);
    }

    function tabulateDelegated(address _voter) 
        external
    {
        require(block.number > voteBlockEnd, "Voting running");
        (address _claimer, Vote _vote) = findNearestDelegatable(_voter); // try finding first delegate from chain which voted
        setTabulation(_voter, _claimer, _vote);
    }   

    function precomputeDelegation(address _start, bool _clean) external {
        require(block.number > voteBlockEnd, "Voting running");
        cacheDelegation(_start,_clean);
    }

    function finalize()
        external
    {
        require(block.number > voteBlockEnd, "Voting running");
        require(lastTabulationBlock + tabulationBlockDelay > block.number, "Tabulation running");
        require(result == Vote.Null, "Already finalized");
        uint256 totalTokens = token.totalSupplyAt(voteBlockEnd);
        uint256 approvals = results[uint8(Vote.Approve)];
        uint256 rejects = results[uint8(Vote.Reject)];
        uint256 approvalQuorum = (totalTokens / 2);
        if(approvals-rejects >= approvalQuorum) {
            result = Vote.Approve;
        } else {
            result = Vote.Reject;
        }
    }

    function clear() 
        external
        onlyController 
    {
        require(result != Vote.Null, "Not finalized");
        selfdestruct(controller);
    }


    function setTabulation(address _voter, address _claimer, Vote _vote) internal {
        require(_vote != Vote.Null, "Cannot be Vote.Null");
        uint256 voterBalance = token.balanceOfAt(_voter, voteBlockEnd);
        address currentClaimer = tabulated[_voter];
        if(currentClaimer != address(0))
        {
            require(currentClaimer != _voter, "Voter already tabulated");
            require(currentClaimer != _claimer, "Claimer already tabulated");
            Vote oldVote = voteMap[currentClaimer];
            require(oldVote != _vote, "Doesn't changes tabulation");
            results[uint8(oldVote)] -= voterBalance;
        }
        tabulated[_voter] = _claimer;
        results[uint8(_vote)] += voterBalance;
        lastTabulationBlock = block.number;
    }

    function findNearestDelegatable(address _voter) internal view returns (address claimer, Vote vote){
        vote = voteMap[_voter];
        require(vote == Vote.Null, "Not delegatable");
        claimer = _voter; // try finding first delegate from chain which voted
        while(vote == Vote.Null) {
            claimer = delegationOf[claimer];
            if(claimer == address(0)){
                claimer = delegation.delegatedToAt(claimer, voteBlockEnd);  
            }
            require(claimer != address(0), "No delegate vote found");
            vote = voteMap[claimer]; //loads delegate vote.
        }
    }

    function cacheDelegation(address _delegator, bool _clean) private returns (address) {
        address delegate;
        if(!_clean) {
            delegate = delegationOf[_delegator];
        }
        if(delegate == address(0)){
            delegate = delegation.delegatedToAt(_delegator, voteBlockEnd); //get delegate chain tail
        }
        require(delegate != address(0), "No delegate vote found");
        if(voteMap[delegate] == Vote.Null) {
            delegate = cacheDelegation(delegate, _clean);
        }
        delegationOf[_delegator] = delegate;
        
        return delegate;
        
    }

}