You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
139 lines
4.5 KiB
139 lines
4.5 KiB
// SPDX-License-Identifier: GPL-3.0
|
|
|
|
pragma solidity >=0.7.0 <0.9.0;
|
|
|
|
/**
|
|
* @title Ballot
|
|
* @dev Implements voting process along with vote delegation
|
|
*/
|
|
contract Ballot {
|
|
|
|
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
|
|
}
|
|
|
|
struct Proposal {
|
|
// If you can limit the length to a certain number of bytes,
|
|
// always use one of bytes1 to bytes32 because they are much cheaper
|
|
bytes32 name; // short name (up to 32 bytes)
|
|
uint voteCount; // number of accumulated votes
|
|
}
|
|
|
|
address public chairperson;
|
|
|
|
mapping(address => Voter) public voters;
|
|
|
|
Proposal[] public proposals;
|
|
|
|
/**
|
|
* @dev Create a new ballot to choose one of 'proposalNames'.
|
|
* @param proposalNames names of proposals
|
|
*/
|
|
constructor(bytes32[] memory proposalNames) {
|
|
chairperson = msg.sender;
|
|
voters[chairperson].weight = 1;
|
|
|
|
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
|
|
}));
|
|
}
|
|
}
|
|
|
|
/**
|
|
* @dev Give 'voter' the right to vote on this ballot. May only be called by 'chairperson'.
|
|
* @param voter address of voter
|
|
*/
|
|
function giveRightToVote(address voter) public {
|
|
require(
|
|
msg.sender == chairperson,
|
|
"Only chairperson can give right to vote."
|
|
);
|
|
require(
|
|
!voters[voter].voted,
|
|
"The voter already voted."
|
|
);
|
|
require(voters[voter].weight == 0, "Voter already has the right to vote.");
|
|
voters[voter].weight = 1;
|
|
}
|
|
|
|
/**
|
|
* @dev Delegate your vote to the voter 'to'.
|
|
* @param to address to which vote is delegated
|
|
*/
|
|
function delegate(address to) public {
|
|
Voter storage sender = voters[msg.sender];
|
|
require(!sender.voted, "You already voted.");
|
|
require(to != msg.sender, "Self-delegation is disallowed.");
|
|
|
|
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.");
|
|
}
|
|
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;
|
|
}
|
|
}
|
|
|
|
/**
|
|
* @dev Give your vote (including votes delegated to you) to proposal 'proposals[proposal].name'.
|
|
* @param proposal index of proposal in the proposals array
|
|
*/
|
|
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.");
|
|
require(proposal < proposals.length, "Invalid proposal index.");
|
|
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.
|
|
* @return winningProposal_ index of winning proposal in the proposals array
|
|
*/
|
|
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;
|
|
}
|
|
}
|
|
}
|
|
|
|
/**
|
|
* @dev Calls winningProposal() function to get the index of the winner contained in the proposals array and then
|
|
* @return winnerName_ the name of the winner
|
|
*/
|
|
function winnerName() public view
|
|
returns (bytes32 winnerName_)
|
|
{
|
|
winnerName_ = proposals[winningProposal()].name;
|
|
}
|
|
}
|
|
|