feat: create semaphore voting contract

Former-commit-id: 55d2ff7b1f

contracts/SemaphoreVoting.sol

@@ -0,0 +1,102 @@
+//SPDX-License-Identifier: GPL-3.0
+pragma solidity ^0.8.4;
+
+import "./SemaphoreCore.sol";
+import "./SemaphoreGroups.sol";
+import "@openzeppelin/contracts/access/Ownable.sol";
+
+contract SemaphoreVoting is SemaphoreCore, SemaphoreGroups {
+  /// @dev Emitted when a ballot is created.
+  /// @param ballotId: ...
+  /// @param coordinator: ...
+  /// @param startDate: ...
+  /// @param endDate: ...
+  event BallotCreated(uint256 ballotId, address coordinator, uint256 startDate, uint256 endDate);
+
+  /// @dev Emitted when a user votes on a ballot.
+  /// @param ballotId: ...
+  /// @param vote: user vote (encrypted or not).
+  event VoteAdded(uint256 indexed ballotId, bytes vote);
+
+  /// @dev Emitted when a decryption key is published.
+  /// @param ballotId: ...
+  /// @param decryptionKey: decryption key.
+  event DecryptionKeyPublished(uint256 indexed ballotId, uint256 decryptionKey);
+
+  // The ballot structure.
+  struct Ballot {
+    address coordinator; // Coordinator of the ballot.
+    uint256 startDate; // Ballot start timestamp.
+    uint256 endDate; // Ballot end timestamp.
+  }
+
+  /// @dev Gets a ballot id and returns the ballot data.
+  mapping(uint256 => Ballot) private ballots;
+
+  modifier onlyCoordinator(uint256 _ballotId) {
+    require(ballots[_ballotId].coordinator == _msgSender(), "SemaphoreVoting: caller is not the ballot coordinator");
+    _;
+  }
+
+  /// @dev Creates ...
+  /// @param _ballotId: Id of the ballot.
+  function createBallot(
+    uint256 _ballotId,
+    address _coordinator,
+    uint256 _startDate,
+    uint256 _endDate
+  ) external {
+    _createGroup(_ballotId, 20, 0);
+
+    Ballot memory ballot;
+
+    ballot.coordinator = _coordinator;
+    ballot.startDate = _startDate;
+    ballot.endDate = _endDate;
+
+    ballots[_ballotId] = ballot;
+
+    emit BallotCreated(_ballotId, _coordinator, _startDate, _endDate);
+  }
+
+  /// @dev Creates ...
+  /// @param _ballotId: Id of the ballot.
+  function addVoter(uint256 _ballotId, uint256 _identityCommitment) external onlyCoordinator(_ballotId) {
+    require(
+      block.timestamp < ballots[_ballotId].startDate,
+      "SemaphoreVoting: voters can be added before the start date"
+    );
+
+    _addIdentityCommitment(_ballotId, _identityCommitment);
+  }
+
+  function vote(
+    bytes memory _vote,
+    uint256 _root,
+    uint256 _nullifierHash,
+    uint256 _ballotId,
+    uint256[8] calldata _proof
+  ) public onlyCoordinator(_ballotId) {
+    Ballot memory ballot = ballots[_ballotId];
+
+    require(block.timestamp > ballot.startDate, "SemaphoreVoting: Invalid vote in advance");
+    require(block.timestamp < ballot.endDate, "SemaphoreVoting: Invalid late vote");
+
+    require(_ballotId == rootHistory[_root], "SemaphoreVoting: the root does not match any ballot");
+    require(_isValidProof(_vote, _root, _nullifierHash, _ballotId, _proof), "SemaphoreVoting: the proof is not valid");
+
+    // Prevent double-signaling (nullifierHash = hash(ballotId + identityNullifier)).
+    _saveNullifierHash(_nullifierHash);
+
+    emit VoteAdded(_ballotId, _vote);
+  }
+
+  /// @dev Publishes the key to decrypt the votes of a ballot.
+  /// @param _ballotId: ballot id.
+  /// @param _decryptionKey: ballot decryption key.
+  function publishDecryptionKey(uint256 _ballotId, uint256 _decryptionKey) external onlyCoordinator(_ballotId) {
+    require(block.timestamp > ballots[_ballotId].endDate, "decryption key can be published after the end date");
+
+    emit DecryptionKeyPublished(_ballotId, _decryptionKey);
+  }
+}