Voting.sol

// SPDX-License-Identifier: AGPL-3.0-only
pragma solidity ^0.8.0;

import "../../common/implementation/FixedPoint.sol";
import "../../common/implementation/Testable.sol";
import "../interfaces/FinderInterface.sol";
import "../interfaces/OracleInterface.sol";
import "../interfaces/OracleAncillaryInterface.sol";
import "../interfaces/VotingInterface.sol";
import "../interfaces/VotingAncillaryInterface.sol";
import "../interfaces/IdentifierWhitelistInterface.sol";
import "./Registry.sol";
import "./ResultComputation.sol";
import "./VoteTiming.sol";
import "./VotingToken.sol";
import "./Constants.sol";

import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/utils/math/SafeMath.sol";
import "@openzeppelin/contracts/utils/cryptography/ECDSA.sol";

/**
 * @title Voting system for Oracle.
 * @dev Handles receiving and resolving price requests via a commit-reveal voting scheme.
 */
contract Voting is
    Testable,
    Ownable,
    OracleInterface,
    OracleAncillaryInterface, // Interface to support ancillary data with price requests.
    VotingInterface,
    VotingAncillaryInterface // Interface to support ancillary data with voting rounds.
{
    using FixedPoint for FixedPoint.Unsigned;
    using SafeMath for uint256;
    using VoteTiming for VoteTiming.Data;
    using ResultComputation for ResultComputation.Data;

    /****************************************
     *        VOTING DATA STRUCTURES        *
     ****************************************/

    // Identifies a unique price request for which the Oracle will always return the same value.
    // Tracks ongoing votes as well as the result of the vote.
    struct PriceRequest {
        bytes32 identifier;
        uint256 time;
        // A map containing all votes for this price in various rounds.
        mapping(uint256 => VoteInstance) voteInstances;
        // If in the past, this was the voting round where this price was resolved. If current or the upcoming round,
        // this is the voting round where this price will be voted on, but not necessarily resolved.
        uint256 lastVotingRound;
        // The index in the `pendingPriceRequests` that references this PriceRequest. A value of UINT_MAX means that
        // this PriceRequest is resolved and has been cleaned up from `pendingPriceRequests`.
        uint256 index;
        bytes ancillaryData;
    }

    struct VoteInstance {
        // Maps (voterAddress) to their submission.
        mapping(address => VoteSubmission) voteSubmissions;
        // The data structure containing the computed voting results.
        ResultComputation.Data resultComputation;
    }

    struct VoteSubmission {
        // A bytes32 of `0` indicates no commit or a commit that was already revealed.
        bytes32 commit;
        // The hash of the value that was revealed.
        // Note: this is only used for computation of rewards.
        bytes32 revealHash;
    }

    struct Round {
        uint256 snapshotId; // Voting token snapshot ID for this round.  0 if no snapshot has been taken.
        FixedPoint.Unsigned inflationRate; // Inflation rate set for this round.
        FixedPoint.Unsigned gatPercentage; // Gat rate set for this round.
        uint256 rewardsExpirationTime; // Time that rewards for this round can be claimed until.
    }

    // Represents the status a price request has.
    enum RequestStatus {
        NotRequested, // Was never requested.
        Active, // Is being voted on in the current round.
        Resolved, // Was resolved in a previous round.
        Future // Is scheduled to be voted on in a future round.
    }

    // Only used as a return value in view methods -- never stored in the contract.
    struct RequestState {
        RequestStatus status;
        uint256 lastVotingRound;
    }

    /****************************************
     *          INTERNAL TRACKING           *
     ****************************************/

    // Maps round numbers to the rounds.
    mapping(uint256 => Round) public rounds;

    // Maps price request IDs to the PriceRequest struct.
    mapping(bytes32 => PriceRequest) private priceRequests;

    // Price request ids for price requests that haven't yet been marked as resolved.
    // These requests may be for future rounds.
    bytes32[] internal pendingPriceRequests;

    VoteTiming.Data public voteTiming;

    // Percentage of the total token supply that must be used in a vote to
    // create a valid price resolution. 1 == 100%.
    FixedPoint.Unsigned public gatPercentage;

    // Global setting for the rate of inflation per vote. This is the percentage of the snapshotted total supply that
    // should be split among the correct voters.
    // Note: this value is used to set per-round inflation at the beginning of each round. 1 = 100%.
    FixedPoint.Unsigned public inflationRate;

    // Time in seconds from the end of the round in which a price request is
    // resolved that voters can still claim their rewards.
    uint256 public rewardsExpirationTimeout;

    // Reference to the voting token.
    VotingToken public votingToken;

    // Reference to the Finder.
    FinderInterface private finder;

    // If non-zero, this contract has been migrated to this address. All voters and
    // financial contracts should query the new address only.
    address public migratedAddress;

    // Max value of an unsigned integer.
    uint256 private constant UINT_MAX = ~uint256(0);

    // Max length in bytes of ancillary data that can be appended to a price request.
    // As of December 2020, the current Ethereum gas limit is 12.5 million. This requestPrice function's gas primarily
    // comes from computing a Keccak-256 hash in _encodePriceRequest and writing a new PriceRequest to
    // storage. We have empirically determined an ancillary data limit of 8192 bytes that keeps this function
    // well within the gas limit at ~8 million gas. To learn more about the gas limit and EVM opcode costs go here:
    // - https://etherscan.io/chart/gaslimit
    // - https://github.com/djrtwo/evm-opcode-gas-costs
    uint256 public constant ancillaryBytesLimit = 8192;

    bytes32 public snapshotMessageHash = ECDSA.toEthSignedMessageHash(keccak256(bytes("Sign For Snapshot")));

    /***************************************
     *                EVENTS                *
     ****************************************/

    event VoteCommitted(
        address indexed voter,
        uint256 indexed roundId,
        bytes32 indexed identifier,
        uint256 time,
        bytes ancillaryData
    );

    event EncryptedVote(
        address indexed voter,
        uint256 indexed roundId,
        bytes32 indexed identifier,
        uint256 time,
        bytes ancillaryData,
        bytes encryptedVote
    );

    event VoteRevealed(
        address indexed voter,
        uint256 indexed roundId,
        bytes32 indexed identifier,
        uint256 time,
        int256 price,
        bytes ancillaryData,
        uint256 numTokens
    );

    event RewardsRetrieved(
        address indexed voter,
        uint256 indexed roundId,
        bytes32 indexed identifier,
        uint256 time,
        bytes ancillaryData,
        uint256 numTokens
    );

    event PriceRequestAdded(uint256 indexed roundId, bytes32 indexed identifier, uint256 time);

    event PriceResolved(
        uint256 indexed roundId,
        bytes32 indexed identifier,
        uint256 time,
        int256 price,
        bytes ancillaryData
    );

    /**
     * @notice Construct the Voting contract.
     * @param _phaseLength length of the commit and reveal phases in seconds.
     * @param _gatPercentage of the total token supply that must be used in a vote to create a valid price resolution.
     * @param _inflationRate percentage inflation per round used to increase token supply of correct voters.
     * @param _rewardsExpirationTimeout timeout, in seconds, within which rewards must be claimed.
     * @param _votingToken address of the UMA token contract used to commit votes.
     * @param _finder keeps track of all contracts within the system based on their interfaceName.
     * @param _timerAddress Contract that stores the current time in a testing environment.
     * Must be set to 0x0 for production environments that use live time.
     */
    constructor(
        uint256 _phaseLength,
        FixedPoint.Unsigned memory _gatPercentage,
        FixedPoint.Unsigned memory _inflationRate,
        uint256 _rewardsExpirationTimeout,
        address _votingToken,
        address _finder,
        address _timerAddress
    ) Testable(_timerAddress) {
        voteTiming.init(_phaseLength);
        require(_gatPercentage.isLessThanOrEqual(1), "GAT percentage must be <= 100%");
        gatPercentage = _gatPercentage;
        inflationRate = _inflationRate;
        votingToken = VotingToken(_votingToken);
        finder = FinderInterface(_finder);
        rewardsExpirationTimeout = _rewardsExpirationTimeout;
    }

    /***************************************
                    MODIFIERS
    ****************************************/

    modifier onlyRegisteredContract() {
        if (migratedAddress != address(0)) {
            require(msg.sender == migratedAddress, "Caller must be migrated address");
        } else {
            Registry registry = Registry(finder.getImplementationAddress(OracleInterfaces.Registry));
            require(registry.isContractRegistered(msg.sender), "Called must be registered");
        }
        _;
    }

    modifier onlyIfNotMigrated() {
        require(migratedAddress == address(0), "Only call this if not migrated");
        _;
    }

    /****************************************
     *  PRICE REQUEST AND ACCESS FUNCTIONS  *
     ****************************************/

    /**
     * @notice Enqueues a request (if a request isn't already present) for the given `identifier`, `time` pair.
     * @dev Time must be in the past and the identifier must be supported. The length of the ancillary data
     * is limited such that this method abides by the EVM transaction gas limit.
     * @param identifier uniquely identifies the price requested. eg BTC/USD (encoded as bytes32) could be requested.
     * @param time unix timestamp for the price request.
     * @param ancillaryData arbitrary data appended to a price request to give the voters more info from the caller.
     */
    function requestPrice(
        bytes32 identifier,
        uint256 time,
        bytes memory ancillaryData
    ) public override onlyRegisteredContract() {
        uint256 blockTime = getCurrentTime();
        require(time <= blockTime, "Can only request in past");
        require(_getIdentifierWhitelist().isIdentifierSupported(identifier), "Unsupported identifier request");
        require(ancillaryData.length <= ancillaryBytesLimit, "Invalid ancillary data");

        bytes32 priceRequestId = _encodePriceRequest(identifier, time, ancillaryData);
        PriceRequest storage priceRequest = priceRequests[priceRequestId];
        uint256 currentRoundId = voteTiming.computeCurrentRoundId(blockTime);

        RequestStatus requestStatus = _getRequestStatus(priceRequest, currentRoundId);

        if (requestStatus == RequestStatus.NotRequested) {
            // Price has never been requested.
            // Price requests always go in the next round, so add 1 to the computed current round.
            uint256 nextRoundId = currentRoundId.add(1);

            PriceRequest storage newPriceRequest = priceRequests[priceRequestId];
            newPriceRequest.identifier = identifier;
            newPriceRequest.time = time;
            newPriceRequest.lastVotingRound = nextRoundId;
            newPriceRequest.index = pendingPriceRequests.length;
            newPriceRequest.ancillaryData = ancillaryData;

            pendingPriceRequests.push(priceRequestId);
            emit PriceRequestAdded(nextRoundId, identifier, time);
        }
    }

    // Overloaded method to enable short term backwards compatibility. Will be deprecated in the next DVM version.
    function requestPrice(bytes32 identifier, uint256 time) public override {
        requestPrice(identifier, time, "");
    }

    /**
     * @notice Whether the price for `identifier` and `time` is available.
     * @dev Time must be in the past and the identifier must be supported.
     * @param identifier uniquely identifies the price requested. eg BTC/USD (encoded as bytes32) could be requested.
     * @param time unix timestamp of for the price request.
     * @param ancillaryData arbitrary data appended to a price request to give the voters more info from the caller.
     * @return _hasPrice bool if the DVM has resolved to a price for the given identifier and timestamp.
     */
    function hasPrice(
        bytes32 identifier,
        uint256 time,
        bytes memory ancillaryData
    ) public view override onlyRegisteredContract() returns (bool) {
        (bool _hasPrice, , ) = _getPriceOrError(identifier, time, ancillaryData);
        return _hasPrice;
    }

    // Overloaded method to enable short term backwards compatibility. Will be deprecated in the next DVM version.
    function hasPrice(bytes32 identifier, uint256 time) public view override returns (bool) {
        return hasPrice(identifier, time, "");
    }

    /**
     * @notice Gets the price for `identifier` and `time` if it has already been requested and resolved.
     * @dev If the price is not available, the method reverts.
     * @param identifier uniquely identifies the price requested. eg BTC/USD (encoded as bytes32) could be requested.
     * @param time unix timestamp of for the price request.
     * @param ancillaryData arbitrary data appended to a price request to give the voters more info from the caller.
     * @return int256 representing the resolved price for the given identifier and timestamp.
     */
    function getPrice(
        bytes32 identifier,
        uint256 time,
        bytes memory ancillaryData
    ) public view override onlyRegisteredContract() returns (int256) {
        (bool _hasPrice, int256 price, string memory message) = _getPriceOrError(identifier, time, ancillaryData);

        // If the price wasn't available, revert with the provided message.
        require(_hasPrice, message);
        return price;
    }

    // Overloaded method to enable short term backwards compatibility. Will be deprecated in the next DVM version.
    function getPrice(bytes32 identifier, uint256 time) public view override returns (int256) {
        return getPrice(identifier, time, "");
    }

    /**
     * @notice Gets the status of a list of price requests, identified by their identifier and time.
     * @dev If the status for a particular request is NotRequested, the lastVotingRound will always be 0.
     * @param requests array of type PendingRequest which includes an identifier and timestamp for each request.
     * @return requestStates a list, in the same order as the input list, giving the status of each of the specified price requests.
     */
    function getPriceRequestStatuses(PendingRequestAncillary[] memory requests)
        public
        view
        returns (RequestState[] memory)
    {
        RequestState[] memory requestStates = new RequestState[](requests.length);
        uint256 currentRoundId = voteTiming.computeCurrentRoundId(getCurrentTime());
        for (uint256 i = 0; i < requests.length; i++) {
            PriceRequest storage priceRequest =
                _getPriceRequest(requests[i].identifier, requests[i].time, requests[i].ancillaryData);

            RequestStatus status = _getRequestStatus(priceRequest, currentRoundId);

            // If it's an active request, its true lastVotingRound is the current one, even if it hasn't been updated.
            if (status == RequestStatus.Active) {
                requestStates[i].lastVotingRound = currentRoundId;
            } else {
                requestStates[i].lastVotingRound = priceRequest.lastVotingRound;
            }
            requestStates[i].status = status;
        }
        return requestStates;
    }

    // Overloaded method to enable short term backwards compatibility. Will be deprecated in the next DVM version.
    function getPriceRequestStatuses(PendingRequest[] memory requests) public view returns (RequestState[] memory) {
        PendingRequestAncillary[] memory requestsAncillary = new PendingRequestAncillary[](requests.length);

        for (uint256 i = 0; i < requests.length; i++) {
            requestsAncillary[i].identifier = requests[i].identifier;
            requestsAncillary[i].time = requests[i].time;
            requestsAncillary[i].ancillaryData = "";
        }
        return getPriceRequestStatuses(requestsAncillary);
    }

    /****************************************
     *            VOTING FUNCTIONS          *
     ****************************************/

    /**
     * @notice Commit a vote for a price request for `identifier` at `time`.
     * @dev `identifier`, `time` must correspond to a price request that's currently in the commit phase.
     * Commits can be changed.
     * @dev Since transaction data is public, the salt will be revealed with the vote. While this is the system’s expected behavior,
     * voters should never reuse salts. If someone else is able to guess the voted price and knows that a salt will be reused, then
     * they can determine the vote pre-reveal.
     * @param identifier uniquely identifies the committed vote. EG BTC/USD price pair.
     * @param time unix timestamp of the price being voted on.
     * @param ancillaryData arbitrary data appended to a price request to give the voters more info from the caller.
     * @param hash keccak256 hash of the `price`, `salt`, voter `address`, `time`, current `roundId`, and `identifier`.
     */
    function commitVote(
        bytes32 identifier,
        uint256 time,
        bytes memory ancillaryData,
        bytes32 hash
    ) public override onlyIfNotMigrated() {
        require(hash != bytes32(0), "Invalid provided hash");
        // Current time is required for all vote timing queries.
        uint256 blockTime = getCurrentTime();
        require(
            voteTiming.computeCurrentPhase(blockTime) == VotingAncillaryInterface.Phase.Commit,
            "Cannot commit in reveal phase"
        );

        // At this point, the computed and last updated round ID should be equal.
        uint256 currentRoundId = voteTiming.computeCurrentRoundId(blockTime);

        PriceRequest storage priceRequest = _getPriceRequest(identifier, time, ancillaryData);
        require(
            _getRequestStatus(priceRequest, currentRoundId) == RequestStatus.Active,
            "Cannot commit inactive request"
        );

        priceRequest.lastVotingRound = currentRoundId;
        VoteInstance storage voteInstance = priceRequest.voteInstances[currentRoundId];
        voteInstance.voteSubmissions[msg.sender].commit = hash;

        emit VoteCommitted(msg.sender, currentRoundId, identifier, time, ancillaryData);
    }

    // Overloaded method to enable short term backwards compatibility. Will be deprecated in the next DVM version.
    function commitVote(
        bytes32 identifier,
        uint256 time,
        bytes32 hash
    ) public override onlyIfNotMigrated() {
        commitVote(identifier, time, "", hash);
    }

    /**
     * @notice Snapshot the current round's token balances and lock in the inflation rate and GAT.
     * @dev This function can be called multiple times, but only the first call per round into this function or `revealVote`
     * will create the round snapshot. Any later calls will be a no-op. Will revert unless called during reveal period.
     * @param signature  signature required to prove caller is an EOA to prevent flash loans from being included in the
     * snapshot.
     */
    function snapshotCurrentRound(bytes calldata signature)
        external
        override(VotingInterface, VotingAncillaryInterface)
        onlyIfNotMigrated()
    {
        uint256 blockTime = getCurrentTime();
        require(voteTiming.computeCurrentPhase(blockTime) == Phase.Reveal, "Only snapshot in reveal phase");
        // Require public snapshot require signature to ensure caller is an EOA.
        require(ECDSA.recover(snapshotMessageHash, signature) == msg.sender, "Signature must match sender");
        uint256 roundId = voteTiming.computeCurrentRoundId(blockTime);
        _freezeRoundVariables(roundId);
    }

    /**
     * @notice Reveal a previously committed vote for `identifier` at `time`.
     * @dev The revealed `price`, `salt`, `address`, `time`, `roundId`, and `identifier`, must hash to the latest `hash`
     * that `commitVote()` was called with. Only the committer can reveal their vote.
     * @param identifier voted on in the commit phase. EG BTC/USD price pair.
     * @param time specifies the unix timestamp of the price being voted on.
     * @param price voted on during the commit phase.
     * @param ancillaryData arbitrary data appended to a price request to give the voters more info from the caller.
     * @param salt value used to hide the commitment price during the commit phase.
     */
    function revealVote(
        bytes32 identifier,
        uint256 time,
        int256 price,
        bytes memory ancillaryData,
        int256 salt
    ) public override onlyIfNotMigrated() {
        require(voteTiming.computeCurrentPhase(getCurrentTime()) == Phase.Reveal, "Cannot reveal in commit phase");
        // Note: computing the current round is required to disallow people from revealing an old commit after the round is over.
        uint256 roundId = voteTiming.computeCurrentRoundId(getCurrentTime());

        PriceRequest storage priceRequest = _getPriceRequest(identifier, time, ancillaryData);
        VoteInstance storage voteInstance = priceRequest.voteInstances[roundId];
        VoteSubmission storage voteSubmission = voteInstance.voteSubmissions[msg.sender];

        // Scoping to get rid of a stack too deep error.
        {
            // 0 hashes are disallowed in the commit phase, so they indicate a different error.
            // Cannot reveal an uncommitted or previously revealed hash
            require(voteSubmission.commit != bytes32(0), "Invalid hash reveal");
            require(
                keccak256(abi.encodePacked(price, salt, msg.sender, time, ancillaryData, roundId, identifier)) ==
                    voteSubmission.commit,
                "Revealed data != commit hash"
            );
            // To protect against flash loans, we require snapshot be validated as EOA.
            require(rounds[roundId].snapshotId != 0, "Round has no snapshot");
        }

        // Get the frozen snapshotId
        uint256 snapshotId = rounds[roundId].snapshotId;

        delete voteSubmission.commit;

        // Get the voter's snapshotted balance. Since balances are returned pre-scaled by 10**18, we can directly
        // initialize the Unsigned value with the returned uint.
        FixedPoint.Unsigned memory balance = FixedPoint.Unsigned(votingToken.balanceOfAt(msg.sender, snapshotId));

        // Set the voter's submission.
        voteSubmission.revealHash = keccak256(abi.encode(price));

        // Add vote to the results.
        voteInstance.resultComputation.addVote(price, balance);

        emit VoteRevealed(msg.sender, roundId, identifier, time, price, ancillaryData, balance.rawValue);
    }

    // Overloaded method to enable short term backwards compatibility. Will be deprecated in the next DVM version.
    function revealVote(
        bytes32 identifier,
        uint256 time,
        int256 price,
        int256 salt
    ) public override {
        revealVote(identifier, time, price, "", salt);
    }

    /**
     * @notice commits a vote and logs an event with a data blob, typically an encrypted version of the vote
     * @dev An encrypted version of the vote is emitted in an event `EncryptedVote` to allow off-chain infrastructure to
     * retrieve the commit. The contents of `encryptedVote` are never used on chain: it is purely for convenience.
     * @param identifier unique price pair identifier. Eg: BTC/USD price pair.
     * @param time unix timestamp of for the price request.
     * @param ancillaryData arbitrary data appended to a price request to give the voters more info from the caller.
     * @param hash keccak256 hash of the price you want to vote for and a `int256 salt`.
     * @param encryptedVote offchain encrypted blob containing the voters amount, time and salt.
     */
    function commitAndEmitEncryptedVote(
        bytes32 identifier,
        uint256 time,
        bytes memory ancillaryData,
        bytes32 hash,
        bytes memory encryptedVote
    ) public override {
        commitVote(identifier, time, ancillaryData, hash);

        uint256 roundId = voteTiming.computeCurrentRoundId(getCurrentTime());
        emit EncryptedVote(msg.sender, roundId, identifier, time, ancillaryData, encryptedVote);
    }

    // Overloaded method to enable short term backwards compatibility. Will be deprecated in the next DVM version.
    function commitAndEmitEncryptedVote(
        bytes32 identifier,
        uint256 time,
        bytes32 hash,
        bytes memory encryptedVote
    ) public override {
        commitVote(identifier, time, "", hash);

        commitAndEmitEncryptedVote(identifier, time, "", hash, encryptedVote);
    }

    /**
     * @notice Submit a batch of commits in a single transaction.
     * @dev Using `encryptedVote` is optional. If included then commitment is emitted in an event.
     * Look at `project-root/common/Constants.js` for the tested maximum number of
     * commitments that can fit in one transaction.
     * @param commits struct to encapsulate an `identifier`, `time`, `hash` and optional `encryptedVote`.
     */
    function batchCommit(CommitmentAncillary[] memory commits) public override {
        for (uint256 i = 0; i < commits.length; i++) {
            if (commits[i].encryptedVote.length == 0) {
                commitVote(commits[i].identifier, commits[i].time, commits[i].ancillaryData, commits[i].hash);
            } else {
                commitAndEmitEncryptedVote(
                    commits[i].identifier,
                    commits[i].time,
                    commits[i].ancillaryData,
                    commits[i].hash,
                    commits[i].encryptedVote
                );
            }
        }
    }

    // Overloaded method to enable short term backwards compatibility. Will be deprecated in the next DVM version.
    function batchCommit(Commitment[] memory commits) public override {
        CommitmentAncillary[] memory commitsAncillary = new CommitmentAncillary[](commits.length);

        for (uint256 i = 0; i < commits.length; i++) {
            commitsAncillary[i].identifier = commits[i].identifier;
            commitsAncillary[i].time = commits[i].time;
            commitsAncillary[i].ancillaryData = "";
            commitsAncillary[i].hash = commits[i].hash;
            commitsAncillary[i].encryptedVote = commits[i].encryptedVote;
        }
        batchCommit(commitsAncillary);
    }

    /**
     * @notice Reveal multiple votes in a single transaction.
     * Look at `project-root/common/Constants.js` for the tested maximum number of reveals.
     * that can fit in one transaction.
     * @dev For more info on reveals, review the comment for `revealVote`.
     * @param reveals array of the Reveal struct which contains an identifier, time, price and salt.
     */
    function batchReveal(RevealAncillary[] memory reveals) public override {
        for (uint256 i = 0; i < reveals.length; i++) {
            revealVote(
                reveals[i].identifier,
                reveals[i].time,
                reveals[i].price,
                reveals[i].ancillaryData,
                reveals[i].salt
            );
        }
    }

    // Overloaded method to enable short term backwards compatibility. Will be deprecated in the next DVM version.
    function batchReveal(Reveal[] memory reveals) public override {
        RevealAncillary[] memory revealsAncillary = new RevealAncillary[](reveals.length);

        for (uint256 i = 0; i < reveals.length; i++) {
            revealsAncillary[i].identifier = reveals[i].identifier;
            revealsAncillary[i].time = reveals[i].time;
            revealsAncillary[i].price = reveals[i].price;
            revealsAncillary[i].ancillaryData = "";
            revealsAncillary[i].salt = reveals[i].salt;
        }
        batchReveal(revealsAncillary);
    }

    /**
     * @notice Retrieves rewards owed for a set of resolved price requests.
     * @dev Can only retrieve rewards if calling for a valid round and if the call is done within the timeout threshold
     * (not expired). Note that a named return value is used here to avoid a stack to deep error.
     * @param voterAddress voter for which rewards will be retrieved. Does not have to be the caller.
     * @param roundId the round from which voting rewards will be retrieved from.
     * @param toRetrieve array of PendingRequests which rewards are retrieved from.
     * @return totalRewardToIssue total amount of rewards returned to the voter.
     */
    function retrieveRewards(
        address voterAddress,
        uint256 roundId,
        PendingRequestAncillary[] memory toRetrieve
    ) public override returns (FixedPoint.Unsigned memory totalRewardToIssue) {
        if (migratedAddress != address(0)) {
            require(msg.sender == migratedAddress, "Can only call from migrated");
        }
        require(roundId < voteTiming.computeCurrentRoundId(getCurrentTime()), "Invalid roundId");

        Round storage round = rounds[roundId];
        bool isExpired = getCurrentTime() > round.rewardsExpirationTime;
        FixedPoint.Unsigned memory snapshotBalance =
            FixedPoint.Unsigned(votingToken.balanceOfAt(voterAddress, round.snapshotId));

        // Compute the total amount of reward that will be issued for each of the votes in the round.
        FixedPoint.Unsigned memory snapshotTotalSupply =
            FixedPoint.Unsigned(votingToken.totalSupplyAt(round.snapshotId));
        FixedPoint.Unsigned memory totalRewardPerVote = round.inflationRate.mul(snapshotTotalSupply);

        // Keep track of the voter's accumulated token reward.
        totalRewardToIssue = FixedPoint.Unsigned(0);

        for (uint256 i = 0; i < toRetrieve.length; i++) {
            PriceRequest storage priceRequest =
                _getPriceRequest(toRetrieve[i].identifier, toRetrieve[i].time, toRetrieve[i].ancillaryData);
            VoteInstance storage voteInstance = priceRequest.voteInstances[priceRequest.lastVotingRound];
            // Only retrieve rewards for votes resolved in same round
            require(priceRequest.lastVotingRound == roundId, "Retrieve for votes same round");

            _resolvePriceRequest(priceRequest, voteInstance);

            if (voteInstance.voteSubmissions[voterAddress].revealHash == 0) {
                continue;
            } else if (isExpired) {
                // Emit a 0 token retrieval on expired rewards.
                emit RewardsRetrieved(
                    voterAddress,
                    roundId,
                    toRetrieve[i].identifier,
                    toRetrieve[i].time,
                    toRetrieve[i].ancillaryData,
                    0
                );
            } else if (
                voteInstance.resultComputation.wasVoteCorrect(voteInstance.voteSubmissions[voterAddress].revealHash)
            ) {
                // The price was successfully resolved during the voter's last voting round, the voter revealed
                // and was correct, so they are eligible for a reward.
                // Compute the reward and add to the cumulative reward.

                FixedPoint.Unsigned memory reward =
                    snapshotBalance.mul(totalRewardPerVote).div(
                        voteInstance.resultComputation.getTotalCorrectlyVotedTokens()
                    );
                totalRewardToIssue = totalRewardToIssue.add(reward);

                // Emit reward retrieval for this vote.
                emit RewardsRetrieved(
                    voterAddress,
                    roundId,
                    toRetrieve[i].identifier,
                    toRetrieve[i].time,
                    toRetrieve[i].ancillaryData,
                    reward.rawValue
                );
            } else {
                // Emit a 0 token retrieval on incorrect votes.
                emit RewardsRetrieved(
                    voterAddress,
                    roundId,
                    toRetrieve[i].identifier,
                    toRetrieve[i].time,
                    toRetrieve[i].ancillaryData,
                    0
                );
            }

            // Delete the submission to capture any refund and clean up storage.
            delete voteInstance.voteSubmissions[voterAddress].revealHash;
        }

        // Issue any accumulated rewards.
        if (totalRewardToIssue.isGreaterThan(0)) {
            require(votingToken.mint(voterAddress, totalRewardToIssue.rawValue), "Voting token issuance failed");
        }
    }

    // Overloaded method to enable short term backwards compatibility. Will be deprecated in the next DVM version.
    function retrieveRewards(
        address voterAddress,
        uint256 roundId,
        PendingRequest[] memory toRetrieve
    ) public override returns (FixedPoint.Unsigned memory) {
        PendingRequestAncillary[] memory toRetrieveAncillary = new PendingRequestAncillary[](toRetrieve.length);

        for (uint256 i = 0; i < toRetrieve.length; i++) {
            toRetrieveAncillary[i].identifier = toRetrieve[i].identifier;
            toRetrieveAncillary[i].time = toRetrieve[i].time;
            toRetrieveAncillary[i].ancillaryData = "";
        }

        return retrieveRewards(voterAddress, roundId, toRetrieveAncillary);
    }

    /****************************************
     *        VOTING GETTER FUNCTIONS       *
     ****************************************/

    /**
     * @notice Gets the queries that are being voted on this round.
     * @return pendingRequests array containing identifiers of type `PendingRequest`.
     * and timestamps for all pending requests.
     */
    function getPendingRequests()
        external
        view
        override(VotingInterface, VotingAncillaryInterface)
        returns (PendingRequestAncillary[] memory)
    {
        uint256 blockTime = getCurrentTime();
        uint256 currentRoundId = voteTiming.computeCurrentRoundId(blockTime);

        // Solidity memory arrays aren't resizable (and reading storage is expensive). Hence this hackery to filter
        // `pendingPriceRequests` only to those requests that have an Active RequestStatus.
        PendingRequestAncillary[] memory unresolved = new PendingRequestAncillary[](pendingPriceRequests.length);
        uint256 numUnresolved = 0;

        for (uint256 i = 0; i < pendingPriceRequests.length; i++) {
            PriceRequest storage priceRequest = priceRequests[pendingPriceRequests[i]];
            if (_getRequestStatus(priceRequest, currentRoundId) == RequestStatus.Active) {
                unresolved[numUnresolved] = PendingRequestAncillary({
                    identifier: priceRequest.identifier,
                    time: priceRequest.time,
                    ancillaryData: priceRequest.ancillaryData
                });
                numUnresolved++;
            }
        }

        PendingRequestAncillary[] memory pendingRequests = new PendingRequestAncillary[](numUnresolved);
        for (uint256 i = 0; i < numUnresolved; i++) {
            pendingRequests[i] = unresolved[i];
        }
        return pendingRequests;
    }

    /**
     * @notice Returns the current voting phase, as a function of the current time.
     * @return Phase to indicate the current phase. Either { Commit, Reveal, NUM_PHASES_PLACEHOLDER }.
     */
    function getVotePhase() external view override(VotingInterface, VotingAncillaryInterface) returns (Phase) {
        return voteTiming.computeCurrentPhase(getCurrentTime());
    }

    /**
     * @notice Returns the current round ID, as a function of the current time.
     * @return uint256 representing the unique round ID.
     */
    function getCurrentRoundId() external view override(VotingInterface, VotingAncillaryInterface) returns (uint256) {
        return voteTiming.computeCurrentRoundId(getCurrentTime());
    }

    /****************************************
     *        OWNER ADMIN FUNCTIONS         *
     ****************************************/

    /**
     * @notice Disables this Voting contract in favor of the migrated one.
     * @dev Can only be called by the contract owner.
     * @param newVotingAddress the newly migrated contract address.
     */
    function setMigrated(address newVotingAddress)
        external
        override(VotingInterface, VotingAncillaryInterface)
        onlyOwner
    {
        migratedAddress = newVotingAddress;
    }

    /**
     * @notice Resets the inflation rate. Note: this change only applies to rounds that have not yet begun.
     * @dev This method is public because calldata structs are not currently supported by solidity.
     * @param newInflationRate sets the next round's inflation rate.
     */
    function setInflationRate(FixedPoint.Unsigned memory newInflationRate)
        public
        override(VotingInterface, VotingAncillaryInterface)
        onlyOwner
    {
        inflationRate = newInflationRate;
    }

    /**
     * @notice Resets the Gat percentage. Note: this change only applies to rounds that have not yet begun.
     * @dev This method is public because calldata structs are not currently supported by solidity.
     * @param newGatPercentage sets the next round's Gat percentage.
     */
    function setGatPercentage(FixedPoint.Unsigned memory newGatPercentage)
        public
        override(VotingInterface, VotingAncillaryInterface)
        onlyOwner
    {
        require(newGatPercentage.isLessThan(1), "GAT percentage must be < 100%");
        gatPercentage = newGatPercentage;
    }

    /**
     * @notice Resets the rewards expiration timeout.
     * @dev This change only applies to rounds that have not yet begun.
     * @param NewRewardsExpirationTimeout how long a caller can wait before choosing to withdraw their rewards.
     */
    function setRewardsExpirationTimeout(uint256 NewRewardsExpirationTimeout)
        public
        override(VotingInterface, VotingAncillaryInterface)
        onlyOwner
    {
        rewardsExpirationTimeout = NewRewardsExpirationTimeout;
    }

    /****************************************
     *    PRIVATE AND INTERNAL FUNCTIONS    *
     ****************************************/

    // Returns the price for a given identifer. Three params are returns: bool if there was an error, int to represent
    // the resolved price and a string which is filled with an error message, if there was an error or "".
    function _getPriceOrError(
        bytes32 identifier,
        uint256 time,
        bytes memory ancillaryData
    )
        private
        view
        returns (
            bool,
            int256,
            string memory
        )
    {
        PriceRequest storage priceRequest = _getPriceRequest(identifier, time, ancillaryData);
        uint256 currentRoundId = voteTiming.computeCurrentRoundId(getCurrentTime());

        RequestStatus requestStatus = _getRequestStatus(priceRequest, currentRoundId);
        if (requestStatus == RequestStatus.Active) {
            return (false, 0, "Current voting round not ended");
        } else if (requestStatus == RequestStatus.Resolved) {
            VoteInstance storage voteInstance = priceRequest.voteInstances[priceRequest.lastVotingRound];
            (, int256 resolvedPrice) =
                voteInstance.resultComputation.getResolvedPrice(_computeGat(priceRequest.lastVotingRound));
            return (true, resolvedPrice, "");
        } else if (requestStatus == RequestStatus.Future) {
            return (false, 0, "Price is still to be voted on");
        } else {
            return (false, 0, "Price was never requested");
        }
    }

    function _getPriceRequest(
        bytes32 identifier,
        uint256 time,
        bytes memory ancillaryData
    ) private view returns (PriceRequest storage) {
        return priceRequests[_encodePriceRequest(identifier, time, ancillaryData)];
    }

    function _encodePriceRequest(
        bytes32 identifier,
        uint256 time,
        bytes memory ancillaryData
    ) private pure returns (bytes32) {
        return keccak256(abi.encode(identifier, time, ancillaryData));
    }

    function _freezeRoundVariables(uint256 roundId) private {
        Round storage round = rounds[roundId];
        // Only on the first reveal should the snapshot be captured for that round.
        if (round.snapshotId == 0) {
            // There is no snapshot ID set, so create one.
            round.snapshotId = votingToken.snapshot();

            // Set the round inflation rate to the current global inflation rate.
            rounds[roundId].inflationRate = inflationRate;

            // Set the round gat percentage to the current global gat rate.
            rounds[roundId].gatPercentage = gatPercentage;

            // Set the rewards expiration time based on end of time of this round and the current global timeout.
            rounds[roundId].rewardsExpirationTime = voteTiming.computeRoundEndTime(roundId).add(
                rewardsExpirationTimeout
            );
        }
    }

    function _resolvePriceRequest(PriceRequest storage priceRequest, VoteInstance storage voteInstance) private {
        if (priceRequest.index == UINT_MAX) {
            return;
        }
        (bool isResolved, int256 resolvedPrice) =
            voteInstance.resultComputation.getResolvedPrice(_computeGat(priceRequest.lastVotingRound));
        require(isResolved, "Can't resolve unresolved request");

        // Delete the resolved price request from pendingPriceRequests.
        uint256 lastIndex = pendingPriceRequests.length - 1;
        PriceRequest storage lastPriceRequest = priceRequests[pendingPriceRequests[lastIndex]];
        lastPriceRequest.index = priceRequest.index;
        pendingPriceRequests[priceRequest.index] = pendingPriceRequests[lastIndex];
        pendingPriceRequests.pop();

        priceRequest.index = UINT_MAX;
        emit PriceResolved(
            priceRequest.lastVotingRound,
            priceRequest.identifier,
            priceRequest.time,
            resolvedPrice,
            priceRequest.ancillaryData
        );
    }

    function _computeGat(uint256 roundId) private view returns (FixedPoint.Unsigned memory) {
        uint256 snapshotId = rounds[roundId].snapshotId;
        if (snapshotId == 0) {
            // No snapshot - return max value to err on the side of caution.
            return FixedPoint.Unsigned(UINT_MAX);
        }

        // Grab the snapshotted supply from the voting token. It's already scaled by 10**18, so we can directly
        // initialize the Unsigned value with the returned uint.
        FixedPoint.Unsigned memory snapshottedSupply = FixedPoint.Unsigned(votingToken.totalSupplyAt(snapshotId));

        // Multiply the total supply at the snapshot by the gatPercentage to get the GAT in number of tokens.
        return snapshottedSupply.mul(rounds[roundId].gatPercentage);
    }

    function _getRequestStatus(PriceRequest storage priceRequest, uint256 currentRoundId)
        private
        view
        returns (RequestStatus)
    {
        if (priceRequest.lastVotingRound == 0) {
            return RequestStatus.NotRequested;
        } else if (priceRequest.lastVotingRound < currentRoundId) {
            VoteInstance storage voteInstance = priceRequest.voteInstances[priceRequest.lastVotingRound];
            (bool isResolved, ) =
                voteInstance.resultComputation.getResolvedPrice(_computeGat(priceRequest.lastVotingRound));
            return isResolved ? RequestStatus.Resolved : RequestStatus.Active;
        } else if (priceRequest.lastVotingRound == currentRoundId) {
            return RequestStatus.Active;
        } else {
            // Means than priceRequest.lastVotingRound > currentRoundId
            return RequestStatus.Future;
        }
    }

    function _getIdentifierWhitelist() private view returns (IdentifierWhitelistInterface supportedIdentifiers) {
        return IdentifierWhitelistInterface(finder.getImplementationAddress(OracleInterfaces.IdentifierWhitelist));
    }
}