Contract Address Details

// SPDX-License-Identifier: MIT
pragma solidity 0.7.6;

import "../interface/IIVoterWhitelister.sol";
import "../../addressUpdater/implementation/AddressUpdatable.sol";
import "../../genesis/interface/IIPriceSubmitter.sol";
import "../../governance/implementation/Governed.sol";
import "../../token/interface/IIVPToken.sol";
import "../../userInterfaces/IFtsoRegistry.sol";
import "../../utils/implementation/SafePct.sol";
import "@openzeppelin/contracts/math/SafeMath.sol";


contract VoterWhitelister is IIVoterWhitelister, Governed, AddressUpdatable {
    using SafeMath for uint256;
    using SafePct for uint256;

    uint256 internal constant TERA = 10 ** 12;                    // 10^12
    uint256 internal constant BIPS100 = 10 ** 4;                  // 100 * 100%

    uint256 public override defaultMaxVotersForFtso;
        
    /**
     * Maximum number of voters in a single ftso whitelist.
     * Adjustable separately for each ftsoIndex.
     */
    mapping (uint256 => uint256) public override maxVotersForFtso;
    
    // mapping: ftsoIndex => array of whitelisted voters for this ftso
    mapping (uint256 => address[]) internal whitelist;
    
    IIPriceSubmitter public immutable priceSubmitter;
    
    IFtsoRegistry public ftsoRegistry;

    address public ftsoManager;

    modifier onlyFtsoManager {
        require(msg.sender == ftsoManager, "only ftso manager");
        _;
    }
    
    constructor(
        address _governance,
        address _addressUpdater,
        IIPriceSubmitter _priceSubmitter,
        uint256 _defaultMaxVotersForFtso
    )
        Governed(_governance) AddressUpdatable(_addressUpdater)
    {
        priceSubmitter = _priceSubmitter;
        defaultMaxVotersForFtso = _defaultMaxVotersForFtso;
    }
    
    /**
     * Request to whitelist `_voter` account to all active ftsos.
     * May be called by any address.
     * It returns an array of supported ftso indices and success flag per index.
     */
    function requestFullVoterWhitelisting(
        address _voter
    ) 
        external override 
        returns (
            uint256[] memory _supportedIndices,
            bool[] memory _success
        )
    {
        if (_isTrustedAddress(_voter)) {
            revert("trusted address");
        }

        _supportedIndices = ftsoRegistry.getSupportedIndices();
        uint256 len = _supportedIndices.length;
        _success = new bool[](len);
        for (uint256 i = 0; i < len; i++) {
            _success[i] = _requestWhitelistingVoter(_voter, _supportedIndices[i]);
        }
    }
    
    /**
     * Request to whitelist `_voter` account to ftso at `_ftsoIndex`. Will revert if vote power too low.
     * May be called by any address.
     */
    function requestWhitelistingVoter(address _voter, uint256 _ftsoIndex) external override {
        if (_isTrustedAddress(_voter)) {
            revert("trusted address");
        }
        
        bool success = _requestWhitelistingVoter(_voter, _ftsoIndex);
        require(success, "vote power too low");
    }

    /**
     * Set the maximum number of voters in the whitelist for FTSO at index `_ftsoIndex`.
     * Calling this function might remove several voters with the least votepower from the whitelist.
     */
    function setMaxVotersForFtso(uint256 _ftsoIndex, uint256 _newMaxVoters) external override onlyGovernance {
        maxVotersForFtso[_ftsoIndex] = _newMaxVoters;
        // need to remove any?
        address[] storage addressesForFtso = whitelist[_ftsoIndex];
        if (_newMaxVoters >= addressesForFtso.length) {
            return;
        }
        // remove voters with minimum vote power
        IIFtso ftso = ftsoRegistry.getFtso(_ftsoIndex);
        uint256[] memory votePowers = _getVotePowerWeights(ftso, addressesForFtso);
        uint256 length = votePowers.length;
        uint256 toRemove = length - _newMaxVoters;
        address[] memory removedVoters = new address[](toRemove);
        for (uint256 n = 0; n < toRemove; n++) {
            uint256 minIndex = _findMinimum(votePowers, length);
            removedVoters[n] = addressesForFtso[minIndex];
            if (minIndex < length - 1) {
                addressesForFtso[minIndex] = addressesForFtso[length - 1];
                votePowers[minIndex] = votePowers[length - 1];
            }
            addressesForFtso.pop();
            --length;
        }
        _votersRemovedFromWhitelist(removedVoters, _ftsoIndex);
    }
    
    /**
     * Set the maximum number of voters in the whitelist for a new FTSO.
     */
    function setDefaultMaxVotersForFtso(uint256 _defaultMaxVotersForFtso) external override onlyGovernance {
        defaultMaxVotersForFtso = _defaultMaxVotersForFtso;
    }
    
    /**
     * Create whitelist with default size for ftso.
     */
    function addFtso(uint256 _ftsoIndex) external override onlyFtsoManager {
        require(maxVotersForFtso[_ftsoIndex] == 0, "whitelist already exist");
        maxVotersForFtso[_ftsoIndex] = defaultMaxVotersForFtso;
    }
    
    /**
     * Clear whitelist for ftso at `_ftsoIndex`.
     */
    function removeFtso(uint256 _ftsoIndex) external override onlyFtsoManager {
        _votersRemovedFromWhitelist(whitelist[_ftsoIndex], _ftsoIndex);
        delete whitelist[_ftsoIndex];
        delete maxVotersForFtso[_ftsoIndex];
    }

    /**
     * Remove `_trustedAddress` from whitelist for ftso at `_ftsoIndex`.
     */
    function removeTrustedAddressFromWhitelist(address _trustedAddress, uint256 _ftsoIndex) external override {
        if (!_isTrustedAddress(_trustedAddress)) {
            revert("not trusted address");
        }
        address[] storage addressesForFtso = whitelist[_ftsoIndex];
        uint256 length = addressesForFtso.length;

        // find index of _trustedAddress
        uint256 index = 0;
        for ( ; index < length; index++) {
            if (addressesForFtso[index] == _trustedAddress) {
                break;
            }
        }

        require(index < length, "trusted address not whitelisted");
        
        // kick the index out and replace it with the last one
        address[] memory removedVoters = new address[](1);
        removedVoters[0] = addressesForFtso[index];
        addressesForFtso[index] = addressesForFtso[length - 1];
        addressesForFtso.pop();
        _votersRemovedFromWhitelist(removedVoters, _ftsoIndex);
    }

    /**
     * Get whitelisted price providers for ftso with `_symbol`
     */
    function getFtsoWhitelistedPriceProvidersBySymbol(
        string memory _symbol
    ) 
        external view override 
        returns (
            address[] memory
    ) 
    {
        uint256 ftsoIndex = ftsoRegistry.getFtsoIndex(_symbol);
        return getFtsoWhitelistedPriceProviders(ftsoIndex);
    }

    /**
     * Get whitelisted price providers for ftso at `_ftsoIndex`
     */
    function getFtsoWhitelistedPriceProviders(uint256 _ftsoIndex) public view override returns (address[] memory) {
        uint256 maxVoters = maxVotersForFtso[_ftsoIndex];
        require(maxVoters > 0, "FTSO index not supported");
        return whitelist[_ftsoIndex];
    }

    /**
     * @notice Implementation of the AddressUpdatable abstract method.
     */
    function _updateContractAddresses(
        bytes32[] memory _contractNameHashes,
        address[] memory _contractAddresses
    )
        internal override
    {
        ftsoRegistry = IFtsoRegistry(_getContractAddress(_contractNameHashes, _contractAddresses, "FtsoRegistry"));
        ftsoManager = _getContractAddress(_contractNameHashes, _contractAddresses, "FtsoManager");
    }

    /**
     * Request to whitelist `_voter` account to ftso at `_ftsoIndex` - implementation.
     */
    function _requestWhitelistingVoter(address _voter, uint256 _ftsoIndex) internal returns(bool) {
        uint256 maxVoters = maxVotersForFtso[_ftsoIndex];
        require(maxVoters > 0, "FTSO index not supported");
        
        address[] storage addressesForFtso = whitelist[_ftsoIndex];
        uint256 length = addressesForFtso.length;
        
        // copy to memory and check if it contains _voter
        address[] memory addresses = new address[](length + 1);
        for (uint256 i = 0; i < length; i++) {
            address addr = addressesForFtso[i];
            if (addr == _voter) {
                // _voter is already whitelisted, return
                return true;
            }
            addresses[i] = addr;
        }
        addresses[length] = _voter;
        
        // can we just add a new one?
        if (length < maxVoters) {
            addressesForFtso.push(_voter);
            _voterWhitelisted(_voter, _ftsoIndex);
            return true;
        }
        
        // find a candidate to kick out
        uint256 minIndex = _minVotePowerIndex(addresses, _ftsoIndex);
        if (minIndex == length) {
            // the new _voter has the minimum vote power, do nothing
            return false;
        }
        
        // kick the minIndex out and replace it with _voter
        address[] memory removedVoters = new address[](1);
        removedVoters[0] = addresses[minIndex];
        addressesForFtso[minIndex] = _voter;
        _votersRemovedFromWhitelist(removedVoters, _ftsoIndex);
        _voterWhitelisted(_voter, _ftsoIndex);

        return true;
    }
    
    /**
     * Find index of the element with minimum vote power weight.
     * In case of a tie, returns later index.
     */
    function _minVotePowerIndex(address[] memory _addresses, uint256 _ftsoIndex) internal returns (uint256) {
        IIFtso ftso = ftsoRegistry.getFtso(_ftsoIndex);
        uint256[] memory votePowers = _getVotePowerWeights(ftso, _addresses);
        return _findMinimum(votePowers, votePowers.length);
    }
    
    /**
     * Calculate vote power weights like FTSO.
     * Unlike FTSO, it calls VPToken vote power in a batch to limit gas consumption.
     * Another difference with FTSO is that voter turnout is ignored (it makes
     * no sense for whitelist, since it has to be initialized before any voting occurs).
     * Apart from turnout, the results should be equal as for FTSO.
     */
    function _getVotePowerWeights(IIFtso ftso, address[] memory _addresses) internal 
        returns (uint256[] memory _votePowers)
    {
        // get parameters
        IIVPToken[] memory assets;
        uint256[] memory assetMultipliers;
        uint256 totalVotePowerNat;
        uint256 totalVotePowerAsset;
        uint256 assetWeightRatio;
        uint256 votePowerBlock;
        (assets, assetMultipliers, totalVotePowerNat, totalVotePowerAsset, assetWeightRatio, votePowerBlock)
            = ftso.getVoteWeightingParameters();
        // nat vote powers
        uint256[] memory wNatVP = 
            _getNativeVotePowerWeights(ftso.wNat(), totalVotePowerNat, _addresses, votePowerBlock);
        // asset vote powers
        uint256[] memory combinedAssetVP = 
            _getAssetVotePowerWeights(assets, assetMultipliers, totalVotePowerAsset, _addresses, votePowerBlock);
        // combine asset and wNat
        return _computeWeightedSum(wNatVP, combinedAssetVP, assetWeightRatio);
    }
    
    /**
     * Calculate native vote power weights like FTSO.
     */
    function _getNativeVotePowerWeights(
        IIVPToken _wNat,
        uint256 _totalVotePowerNat,
        address[] memory _addresses, 
        uint256 _blockNumber
    )
        internal
        returns (uint256[] memory _wNatVP)
    {
        _wNatVP = _getVotePowers(_wNat, _addresses, _blockNumber);
        if (_totalVotePowerNat == 0) {
            return _wNatVP;  // if total is 0, all values must be 0, no division needed
        }
        for (uint256 i = 0; i < _addresses.length; i++) {
            _wNatVP[i] = _wNatVP[i].mulDiv(TERA, _totalVotePowerNat);
        }
    }
    
    /**
     * Calculate asset vote power weights like FTSO.
     */
    function _getAssetVotePowerWeights(
        IIVPToken[] memory _assets,
        uint256[] memory _assetMultipliers,
        uint256 _totalVotePowerAsset,
        address[] memory _addresses, 
        uint256 _blockNumber
    )
        internal 
        returns (uint256[] memory _combinedAssetVP)
    {
        _combinedAssetVP = new uint256[](_addresses.length);
        for (uint256 i = 0; i < _addresses.length; i++) {
            _combinedAssetVP[i] = 0;
        }
        if (_totalVotePowerAsset == 0) {
            return _combinedAssetVP;
        }
        uint256 divisor = _totalVotePowerAsset.mul(1e18);
        for (uint256 n = 0; n < _assets.length; n++) {
            IIVPToken asset = _assets[n];
            if (address(asset) != address(0)) {
                uint256[] memory assetVP = _getVotePowers(asset, _addresses, _blockNumber);
                // add
                for (uint256 i = 0; i < _addresses.length; i++) {
                    uint256 weightedVP = assetVP[i].mulDiv(_assetMultipliers[n], divisor);
                    _combinedAssetVP[i] = _combinedAssetVP[i].add(weightedVP);
                }
            }
        }
    }
    
    /**
     * Get vote powers from VPToken in a batch.
     * This is needed to avoid gas consumption of many cros-contract calls.
     */
    function _getVotePowers(
        IIVPToken _token, 
        address[] memory _addresses, 
        uint256 _blockNumber
    )
        internal 
        returns (uint256[] memory)
    {
        // warm up cache for new voter (in this way everyone pays cache storing price for himself)
        _token.votePowerOfAtCached(_addresses[_addresses.length - 1], _blockNumber);
        // get all vote powers in a batch
        return _token.batchVotePowerOfAt(_addresses, _blockNumber);
    }
    
    /**
     * Checks if _voter is trusted address
     */
    function _isTrustedAddress(address _voter) internal view returns(bool) {
        address[] memory trustedAddresses = priceSubmitter.getTrustedAddresses();
        for (uint256 i = 0; i < trustedAddresses.length; i++) {
            if (trustedAddresses[i] == _voter) {
                return true;
            }
        }
        return false;
    }
    
    /**
     * Update a voter whitelisting and emit an event.
     */    
    function _voterWhitelisted(address _voter, uint256 _ftsoIndex) private {
        emit VoterWhitelisted(_voter, _ftsoIndex);
        priceSubmitter.voterWhitelisted(_voter, _ftsoIndex);
    }
    
    /**
     * Update when a  voter is removed from the whitelist. And emit an event.
     */    
    function _votersRemovedFromWhitelist(address[] memory _removedVoters, uint256 _ftsoIndex) private {
        for (uint256 i = 0; i < _removedVoters.length; i++) {
            emit VoterRemovedFromWhitelist(_removedVoters[i], _ftsoIndex);
        }
        priceSubmitter.votersRemovedFromWhitelist(_removedVoters, _ftsoIndex);
    }

    /**
     * Calculate sum of all values in an array.
     */
    function _arraySum(uint256[] memory array) private pure returns (uint256) {
        uint256 result = 0;
        for (uint256 i = 0; i < array.length; i++) {
            result = result.add(array[i]);
        }
        return result;
    }
    
    /**
     * Calculate weighted sum of two arrays (like in FTSO):
     *  result[i] = (100% - _assetWeightRatio) * _weightsNat[i] + _assetWeightRatio * _weightsAsset[i]
     */
    function _computeWeightedSum(
        uint256[] memory _weightsNat,
        uint256[] memory _weightsAsset,
        uint256 _assetWeightRatio
    )
        private pure 
        returns (uint256[] memory _weights)
    {
        uint256 weightAssetSum = _arraySum(_weightsAsset);
        uint256 weightNatSum = _arraySum(_weightsNat);
        uint256 weightAssetShare = weightAssetSum > 0 ? _assetWeightRatio : 0;
        uint256 weightNatShare = weightNatSum > 0 ? BIPS100 - weightAssetShare : 0;
        _weights = new uint256[](_weightsNat.length);
        for (uint256 i = 0; i < _weightsNat.length; i++) {
            uint256 weightNat = 0;
            if (weightNatShare > 0) {
                weightNat = weightNatShare.mulDiv(TERA * _weightsNat[i], weightNatSum * BIPS100);
            }
            uint256 weightAsset = 0;
            if (weightAssetShare > 0) {
                weightAsset = weightAssetShare.mulDiv(TERA * _weightsAsset[i], weightAssetSum * BIPS100);
            }
            _weights[i] = weightNat + weightAsset;
        }
    }

    /**
     * Find minimum index of an uint256 array.
     * In case of a tie, returns later index.
     */
    function _findMinimum(uint256[] memory _votePowers, uint256 _length) private pure returns (uint256) {
        uint256 minIndex = 0;
        uint256 minVP = _votePowers[0];
        for (uint256 i = 0; i < _length; i++) {
            uint256 vp = _votePowers[i];
            // using `<=` ensures that later index is used if there is a tie
            // this is useful because in requestWhitelistingVoter, the new voter is last
            // also, when removing, it is cheaper to remove last element
            if (vp <= minVP) {
                minIndex = i;
                minVP = vp;
            }
        }
        return minIndex;
    }
}
        

// SPDX-License-Identifier: MIT
pragma solidity 0.7.6;

import "../interface/IIAddressUpdatable.sol";


abstract contract AddressUpdatable is IIAddressUpdatable {

    // https://docs.soliditylang.org/en/v0.8.7/contracts.html#constant-and-immutable-state-variables
    // No storage slot is allocated
    bytes32 internal constant ADDRESS_STORAGE_POSITION = 
        keccak256("flare.diamond.AddressUpdatable.ADDRESS_STORAGE_POSITION");

    modifier onlyAddressUpdater() {
        require (msg.sender == getAddressUpdater(), "only address updater");
        _;
    }

    constructor(address _addressUpdater) {
        setAddressUpdaterValue(_addressUpdater);
    }

    function getAddressUpdater() public view returns (address _addressUpdater) {
        // Only direct constants are allowed in inline assembly, so we assign it here
        bytes32 position = ADDRESS_STORAGE_POSITION;
        // solhint-disable-next-line no-inline-assembly
        assembly {
            _addressUpdater := sload(position)
        }
    }

    /**
     * @notice external method called from AddressUpdater only
     */
    function updateContractAddresses(
        bytes32[] memory _contractNameHashes,
        address[] memory _contractAddresses
    )
        external override
        onlyAddressUpdater
    {
        // update addressUpdater address
        setAddressUpdaterValue(_getContractAddress(_contractNameHashes, _contractAddresses, "AddressUpdater"));
        // update all other addresses
        _updateContractAddresses(_contractNameHashes, _contractAddresses);
    }

    /**
     * @notice virtual method that a contract extending AddressUpdatable must implement
     */
    function _updateContractAddresses(
        bytes32[] memory _contractNameHashes,
        address[] memory _contractAddresses
    ) internal virtual;

    /**
     * @notice helper method to get contract address
     * @dev it reverts if contract name does not exist
     */
    function _getContractAddress(
        bytes32[] memory _nameHashes,
        address[] memory _addresses,
        string memory _nameToFind
    )
        internal pure
        returns(address)
    {
        bytes32 nameHash = keccak256(abi.encode(_nameToFind));
        address a = address(0);
        for (uint256 i = 0; i < _nameHashes.length; i++) {
            if (nameHash == _nameHashes[i]) {
                a = _addresses[i];
                break;
            }
        }
        require(a != address(0), "address zero");
        return a;
    }

    function setAddressUpdaterValue(address _addressUpdater) internal {
        // Only direct constants are allowed in inline assembly, so we assign it here
        bytes32 position = ADDRESS_STORAGE_POSITION;
        // solhint-disable-next-line no-inline-assembly  
        assembly {
            sstore(position, _addressUpdater)
        }
    }
}
          

// SPDX-License-Identifier: MIT
pragma solidity >=0.7.6 <0.9;


interface IIAddressUpdatable {
    /**
     * @notice Updates contract addresses - should be called only from AddressUpdater contract
     * @param _contractNameHashes       list of keccak256(abi.encode(...)) contract names
     * @param _contractAddresses        list of contract addresses corresponding to the contract names
     */
    function updateContractAddresses(
        bytes32[] memory _contractNameHashes,
        address[] memory _contractAddresses
        ) external;
}
          

// SPDX-License-Identifier: MIT
pragma solidity >=0.7.6 <0.9;

import "../../genesis/interface/IFtsoGenesis.sol";
import "../../userInterfaces/IFtso.sol";
import "../../token/interface/IIVPToken.sol";


interface IIFtso is IFtso, IFtsoGenesis {

    /// function finalizePriceReveal
    /// called by reward manager only on correct timing.
    /// if price reveal period for epoch x ended. finalize.
    /// iterate list of price submissions
    /// find weighted median
    /// find adjucant 50% of price submissions.
    /// Allocate reward for any price submission which is same as a "winning" submission
    function finalizePriceEpoch(uint256 _epochId, bool _returnRewardData) external
        returns(
            address[] memory _eligibleAddresses,
            uint256[] memory _natWeights,
            uint256 _totalNatWeight
        );

    function fallbackFinalizePriceEpoch(uint256 _epochId) external;

    function forceFinalizePriceEpoch(uint256 _epochId) external;

    // activateFtso will be called by ftso manager once ftso is added 
    // before this is done, FTSO can't run
    function activateFtso(
        uint256 _firstEpochStartTs,
        uint256 _submitPeriodSeconds,
        uint256 _revealPeriodSeconds
    ) external;

    function deactivateFtso() external;

    // update initial price and timestamp - only if not active
    function updateInitialPrice(uint256 _initialPriceUSD, uint256 _initialPriceTimestamp) external;

    function configureEpochs(
        uint256 _maxVotePowerNatThresholdFraction,
        uint256 _maxVotePowerAssetThresholdFraction,
        uint256 _lowAssetUSDThreshold,
        uint256 _highAssetUSDThreshold,
        uint256 _highAssetTurnoutThresholdBIPS,
        uint256 _lowNatTurnoutThresholdBIPS,
        address[] memory _trustedAddresses
    ) external;

    function setAsset(IIVPToken _asset) external;

    function setAssetFtsos(IIFtso[] memory _assetFtsos) external;

    // current vote power block will update per reward epoch. 
    // the FTSO doesn't have notion of reward epochs.
    // reward manager only can set this data. 
    function setVotePowerBlock(uint256 _blockNumber) external;

    function initializeCurrentEpochStateForReveal(uint256 _circulatingSupplyNat, bool _fallbackMode) external;
  
    /**
     * @notice Returns ftso manager address
     */
    function ftsoManager() external view returns (address);

    /**
     * @notice Returns the FTSO asset
     * @dev Asset is null in case of multi-asset FTSO
     */
    function getAsset() external view returns (IIVPToken);

    /**
     * @notice Returns the Asset FTSOs
     * @dev AssetFtsos is not null only in case of multi-asset FTSO
     */
    function getAssetFtsos() external view returns (IIFtso[] memory);

    /**
     * @notice Returns current configuration of epoch state
     * @return _maxVotePowerNatThresholdFraction        High threshold for native token vote power per voter
     * @return _maxVotePowerAssetThresholdFraction      High threshold for asset vote power per voter
     * @return _lowAssetUSDThreshold            Threshold for low asset vote power
     * @return _highAssetUSDThreshold           Threshold for high asset vote power
     * @return _highAssetTurnoutThresholdBIPS   Threshold for high asset turnout
     * @return _lowNatTurnoutThresholdBIPS      Threshold for low nat turnout
     * @return _trustedAddresses                Trusted addresses - use their prices if low nat turnout is not achieved
     */
    function epochsConfiguration() external view 
        returns (
            uint256 _maxVotePowerNatThresholdFraction,
            uint256 _maxVotePowerAssetThresholdFraction,
            uint256 _lowAssetUSDThreshold,
            uint256 _highAssetUSDThreshold,
            uint256 _highAssetTurnoutThresholdBIPS,
            uint256 _lowNatTurnoutThresholdBIPS,
            address[] memory _trustedAddresses
        );

    /**
     * @notice Returns parameters necessary for approximately replicating vote weighting.
     * @return _assets                  the list of Assets that are accounted in vote
     * @return _assetMultipliers        weight of each asset in (multiasset) ftso, mutiplied by TERA
     * @return _totalVotePowerNat       total native token vote power at block
     * @return _totalVotePowerAsset     total combined asset vote power at block
     * @return _assetWeightRatio        ratio of combined asset vp vs. native token vp (in BIPS)
     * @return _votePowerBlock          vote powewr block for given epoch
     */
    function getVoteWeightingParameters() external view 
        returns (
            IIVPToken[] memory _assets,
            uint256[] memory _assetMultipliers,
            uint256 _totalVotePowerNat,
            uint256 _totalVotePowerAsset,
            uint256 _assetWeightRatio,
            uint256 _votePowerBlock
        );

    function wNat() external view returns (IIVPToken);
    
    /**
     * @notice Returns current asset price calculated from trusted providers
     * @return _price               Price in USD multiplied by ASSET_PRICE_USD_DECIMALS
     * @return _timestamp           Time when price was updated for the last time
     */
    function getCurrentPriceFromTrustedProviders() external view returns (uint256 _price, uint256 _timestamp);
}
          

// SPDX-License-Identifier: MIT
pragma solidity >=0.7.6 <0.9;


interface IFtsoGenesis {

    /**
     * @notice Reveals submitted price during epoch reveal period - only price submitter
     * @param _voter                Voter address
     * @param _epochId              Id of the epoch in which the price hash was submitted
     * @param _price                Submitted price in USD
     * @notice The hash of _price and _random must be equal to the submitted hash
     * @notice Emits PriceRevealed event
     */
    function revealPriceSubmitter(
        address _voter,
        uint256 _epochId,
        uint256 _price,
        uint256 _wNatVP
    ) external;

    /**
     * @notice Get (and cache) wNat vote power for specified voter and given epoch id
     * @param _voter                Voter address
     * @param _epochId              Id of the epoch in which the price hash was submitted
     * @return wNat vote power
     */
    function wNatVotePowerCached(address _voter, uint256 _epochId) external returns (uint256);
}
          

// SPDX-License-Identifier: MIT
pragma solidity >=0.7.6 <0.9;


interface IFtsoManagerGenesis {

    function getCurrentPriceEpochId() external view returns (uint256 _priceEpochId);

}
          

// SPDX-License-Identifier: MIT
pragma solidity >=0.7.6 <0.9;

import "./IFtsoGenesis.sol";


interface IFtsoRegistryGenesis {

    function getFtsos(uint256[] memory _indices) external view returns(IFtsoGenesis[] memory _ftsos);
}
          

// SPDX-License-Identifier: MIT
pragma solidity >=0.7.6 <0.9;

import "../../userInterfaces/IPriceSubmitter.sol";
interface IIPriceSubmitter is IPriceSubmitter {

    /**
     * Set trusted addresses that are always allowed to submit and reveal.
     * Only ftso manager can call this method.
     */
    function setTrustedAddresses(address[] memory _trustedAddresses) external;

    /**
     * Called from whitelister when new voter has been whitelisted.
     */
    function voterWhitelisted(address _voter, uint256 _ftsoIndex) external;
    
    /**
     * Called from whitelister when one or more voters have been removed.
     */
    function votersRemovedFromWhitelist(address[] memory _voters, uint256 _ftsoIndex) external;

    /**
     * Returns a list of trusted addresses that are always allowed to submit and reveal.
     */
    function getTrustedAddresses() external view returns (address[] memory);
}
          

// SPDX-License-Identifier: MIT
pragma solidity 0.7.6;

import { GovernedBase } from "./GovernedBase.sol";


/**
 * @title Governed
 * @dev For deployed, governed contracts, enforce a non-zero address at create time.
 **/
contract Governed is GovernedBase {
    constructor(address _governance) GovernedBase(_governance) {
        require(_governance != address(0), "_governance zero");
    }
}
          

// SPDX-License-Identifier: MIT
pragma solidity 0.7.6;

import "../../userInterfaces/IGovernanceSettings.sol";


/**
 * @title Governed Base
 * @notice This abstract base class defines behaviors for a governed contract.
 * @dev This class is abstract so that specific behaviors can be defined for the constructor.
 *   Contracts should not be left ungoverned, but not all contract will have a constructor
 *   (for example those pre-defined in genesis).
 **/
abstract contract GovernedBase {
    struct TimelockedCall {
        uint256 allowedAfterTimestamp;
        bytes encodedCall;
    }
    
    // solhint-disable-next-line const-name-snakecase
    IGovernanceSettings public constant governanceSettings = 
        IGovernanceSettings(0x1000000000000000000000000000000000000007);

    address private initialGovernance;

    bool private initialised;
    
    bool public productionMode;
    
    bool private executing;
    
    mapping(bytes4 => TimelockedCall) public timelockedCalls;
    
    event GovernanceCallTimelocked(bytes4 selector, uint256 allowedAfterTimestamp, bytes encodedCall);
    event TimelockedGovernanceCallExecuted(bytes4 selector, uint256 timestamp);
    event TimelockedGovernanceCallCanceled(bytes4 selector, uint256 timestamp);
    
    event GovernanceInitialised(address initialGovernance);
    event GovernedProductionModeEntered(address governanceSettings);
    
    modifier onlyGovernance {
        if (executing || !productionMode) {
            _beforeExecute();
            _;
        } else {
            _recordTimelockedCall(msg.data);
        }
    }
    
    modifier onlyImmediateGovernance () {
        _checkOnlyGovernance();
        _;
    }

    constructor(address _initialGovernance) {
        if (_initialGovernance != address(0)) {
            initialise(_initialGovernance);
        }
    }

    /**
     * @notice Execute the timelocked governance calls once the timelock period expires.
     * @dev Only executor can call this method.
     * @param _selector The method selector (only one timelocked call per method is stored).
     */
    function executeGovernanceCall(bytes4 _selector) external {
        require(governanceSettings.isExecutor(msg.sender), "only executor");
        TimelockedCall storage call = timelockedCalls[_selector];
        require(call.allowedAfterTimestamp != 0, "timelock: invalid selector");
        require(block.timestamp >= call.allowedAfterTimestamp, "timelock: not allowed yet");
        bytes memory encodedCall = call.encodedCall;
        delete timelockedCalls[_selector];
        executing = true;
        //solhint-disable-next-line avoid-low-level-calls
        (bool success,) = address(this).call(encodedCall);
        executing = false;
        emit TimelockedGovernanceCallExecuted(_selector, block.timestamp);
        _passReturnOrRevert(success);
    }
    
    /**
     * Cancel a timelocked governance call before it has been executed.
     * @dev Only governance can call this method.
     * @param _selector The method selector.
     */
    function cancelGovernanceCall(bytes4 _selector) external onlyImmediateGovernance {
        require(timelockedCalls[_selector].allowedAfterTimestamp != 0, "timelock: invalid selector");
        emit TimelockedGovernanceCallCanceled(_selector, block.timestamp);
        delete timelockedCalls[_selector];
    }
    
    /**
     * Enter the production mode after all the initial governance settings have been set.
     * This enables timelocks and the governance is afterwards obtained by calling 
     * governanceSettings.getGovernanceAddress(). 
     */
    function switchToProductionMode() external {
        _checkOnlyGovernance();
        require(!productionMode, "already in production mode");
        initialGovernance = address(0);
        productionMode = true;
        emit GovernedProductionModeEntered(address(governanceSettings));
    }

    /**
     * @notice Initialize the governance address if not first initialized.
     */
    function initialise(address _initialGovernance) public virtual {
        require(initialised == false, "initialised != false");
        initialised = true;
        initialGovernance = _initialGovernance;
        emit GovernanceInitialised(_initialGovernance);
    }
    
    /**
     * Returns the current effective governance address.
     */
    function governance() public view returns (address) {
        return productionMode ? governanceSettings.getGovernanceAddress() : initialGovernance;
    }

    function _beforeExecute() private {
        if (executing) {
            // can only be run from executeGovernanceCall(), where we check that only executor can call
            // make sure nothing else gets executed, even in case of reentrancy
            assert(msg.sender == address(this));
            executing = false;
        } else {
            // must be called with: productionMode=false
            // must check governance in this case
            _checkOnlyGovernance();
        }
    }

    function _recordTimelockedCall(bytes calldata _data) private {
        _checkOnlyGovernance();
        bytes4 selector;
        //solhint-disable-next-line no-inline-assembly
        assembly {
            selector := calldataload(_data.offset)
        }
        uint256 timelock = governanceSettings.getTimelock();
        uint256 allowedAt = block.timestamp + timelock;
        timelockedCalls[selector] = TimelockedCall({
            allowedAfterTimestamp: allowedAt,
            encodedCall: _data
        });
        emit GovernanceCallTimelocked(selector, allowedAt, _data);
    }
    
    function _checkOnlyGovernance() private view {
        require(msg.sender == governance(), "only governance");
    }
    
    function _passReturnOrRevert(bool _success) private pure {
        // pass exact return or revert data - needs to be done in assembly
        //solhint-disable-next-line no-inline-assembly
        assembly {
            let size := returndatasize()
            let ptr := mload(0x40)
            mstore(0x40, add(ptr, size))
            returndatacopy(ptr, 0, size)
            if _success {
                return(ptr, size)
            }
            revert(ptr, size)
        }
    }
}
          

// SPDX-License-Identifier: MIT
pragma solidity >=0.7.6 <0.9;

interface IICleanable {
    /**
     * Set the contract that is allowed to call history cleaning methods.
     */
    function setCleanerContract(address _cleanerContract) external;
    
    /**
     * Set the cleanup block number.
     * Historic data for the blocks before `cleanupBlockNumber` can be erased,
     * history before that block should never be used since it can be inconsistent.
     * In particular, cleanup block number must be before current vote power block.
     * @param _blockNumber The new cleanup block number.
     */
    function setCleanupBlockNumber(uint256 _blockNumber) external;
    
    /**
     * Get the current cleanup block number.
     */
    function cleanupBlockNumber() external view returns (uint256);
}
          

// SPDX-License-Identifier: MIT
pragma solidity >=0.7.6 <0.9;

import "../../userInterfaces/IVPToken.sol";
import "../../userInterfaces/IGovernanceVotePower.sol";

interface IIGovernanceVotePower is IGovernanceVotePower {
    /**
     * Event triggered when an delegator's balance changes.
     *
     * Note: the event is always emitted from `GovernanceVotePower`.
     */
    event DelegateVotesChanged(
    address indexed delegate, 
    uint256 previousBalance, 
    uint256 newBalance
    );

    /**
     * Event triggered when an account delegates to another account.
     *
     * Note: the event is always emitted from `GovernanceVotePower`.
     */
    event DelegateChanged(
    address indexed delegator, 
    address indexed fromDelegate, 
    address indexed toDelegate
    );

    /**
     * Update vote powers when tokens are transfered.
     **/
    function updateAtTokenTransfer(
        address _from,
        address _to,
        uint256 _fromBalance,
        uint256 _toBalance,
        uint256 _amount
    ) external;

    /**
     * Set the cleanup block number.
     * Historic data for the blocks before `cleanupBlockNumber` can be erased,
     * history before that block should never be used since it can be inconsistent.
     * In particular, cleanup block number must be before current vote power block.
     * @param _blockNumber The new cleanup block number.
     */
    function setCleanupBlockNumber(uint256 _blockNumber) external;

    /**
     * Set the contract that is allowed to call history cleaning methods.
     */
    function setCleanerContract(address _cleanerContract) external;

    /**
     * @notice Get the token that this governance vote power contract belongs to.
     */
    function ownerToken() external view returns (IVPToken);

    function getCleanupBlockNumber() external view returns(uint256);
}
          

// SPDX-License-Identifier: MIT
pragma solidity >=0.7.6 <0.9;

import "../../userInterfaces/IVPToken.sol";
import "../../userInterfaces/IVPContractEvents.sol";
import "./IICleanable.sol";

interface IIVPContract is IICleanable, IVPContractEvents {
    /**
     * Update vote powers when tokens are transfered.
     * Also update delegated vote powers for percentage delegation
     * and check for enough funds for explicit delegations.
     **/
    function updateAtTokenTransfer(
        address _from, 
        address _to, 
        uint256 _fromBalance,
        uint256 _toBalance,
        uint256 _amount
    ) external;

    /**
     * @notice Delegate `_bips` percentage of voting power to `_to` from `_from`
     * @param _from The address of the delegator
     * @param _to The address of the recipient
     * @param _balance The delegator's current balance
     * @param _bips The percentage of voting power to be delegated expressed in basis points (1/100 of one percent).
     *   Not cummulative - every call resets the delegation value (and value of 0 revokes delegation).
     **/
    function delegate(
        address _from, 
        address _to, 
        uint256 _balance, 
        uint256 _bips
    ) external;
    
    /**
     * @notice Explicitly delegate `_amount` of voting power to `_to` from `msg.sender`.
     * @param _from The address of the delegator
     * @param _to The address of the recipient
     * @param _balance The delegator's current balance
     * @param _amount An explicit vote power amount to be delegated.
     *   Not cummulative - every call resets the delegation value (and value of 0 undelegates `to`).
     **/    
    function delegateExplicit(
        address _from, 
        address _to, 
        uint256 _balance, 
        uint _amount
    ) external;    

    /**
     * @notice Revoke all delegation from sender to `_who` at given block. 
     *    Only affects the reads via `votePowerOfAtCached()` in the block `_blockNumber`.
     *    Block `_blockNumber` must be in the past. 
     *    This method should be used only to prevent rogue delegate voting in the current voting block.
     *    To stop delegating use delegate/delegateExplicit with value of 0 or undelegateAll/undelegateAllExplicit.
     * @param _from The address of the delegator
     * @param _who Address of the delegatee
     * @param _balance The delegator's current balance
     * @param _blockNumber The block number at which to revoke delegation.
     **/
    function revokeDelegationAt(
        address _from, 
        address _who, 
        uint256 _balance,
        uint _blockNumber
    ) external;
    
        /**
     * @notice Undelegate all voting power for delegates of `msg.sender`
     *    Can only be used with percentage delegation.
     *    Does not reset delegation mode back to NOTSET.
     * @param _from The address of the delegator
     **/
    function undelegateAll(
        address _from,
        uint256 _balance
    ) external;
    
    /**
     * @notice Undelegate all explicit vote power by amount delegates for `msg.sender`.
     *    Can only be used with explicit delegation.
     *    Does not reset delegation mode back to NOTSET.
     * @param _from The address of the delegator
     * @param _delegateAddresses Explicit delegation does not store delegatees' addresses, 
     *   so the caller must supply them.
     * @return The amount still delegated (in case the list of delegates was incomplete).
     */
    function undelegateAllExplicit(
        address _from, 
        address[] memory _delegateAddresses
    ) external returns (uint256);
    
    /**
    * @notice Get the vote power of `_who` at block `_blockNumber`
    *   Reads/updates cache and upholds revocations.
    * @param _who The address to get voting power.
    * @param _blockNumber The block number at which to fetch.
    * @return Vote power of `_who` at `_blockNumber`.
    */
    function votePowerOfAtCached(address _who, uint256 _blockNumber) external returns(uint256);
    
    /**
     * @notice Get the current vote power of `_who`.
     * @param _who The address to get voting power.
     * @return Current vote power of `_who`.
     */
    function votePowerOf(address _who) external view returns(uint256);
    
    /**
    * @notice Get the vote power of `_who` at block `_blockNumber`
    * @param _who The address to get voting power.
    * @param _blockNumber The block number at which to fetch.
    * @return Vote power of `_who` at `_blockNumber`.
    */
    function votePowerOfAt(address _who, uint256 _blockNumber) external view returns(uint256);

    /**
    * @notice Get the vote power of `_who` at block `_blockNumber`, ignoring revocation information (and cache).
    * @param _who The address to get voting power.
    * @param _blockNumber The block number at which to fetch.
    * @return Vote power of `_who` at `_blockNumber`. Result doesn't change if vote power is revoked.
    */
    function votePowerOfAtIgnoringRevocation(address _who, uint256 _blockNumber) external view returns(uint256);

    /**
     * Return vote powers for several addresses in a batch.
     * @param _owners The list of addresses to fetch vote power of.
     * @param _blockNumber The block number at which to fetch.
     * @return A list of vote powers.
     */    
    function batchVotePowerOfAt(
        address[] memory _owners, 
        uint256 _blockNumber
    )
        external view returns(uint256[] memory);

    /**
    * @notice Get current delegated vote power `_from` delegator delegated `_to` delegatee.
    * @param _from Address of delegator
    * @param _to Address of delegatee
    * @param _balance The delegator's current balance
    * @return The delegated vote power.
    */
    function votePowerFromTo(
        address _from, 
        address _to, 
        uint256 _balance
    ) external view returns(uint256);
    
    /**
    * @notice Get delegated the vote power `_from` delegator delegated `_to` delegatee at `_blockNumber`.
    * @param _from Address of delegator
    * @param _to Address of delegatee
    * @param _balance The delegator's current balance
    * @param _blockNumber The block number at which to fetch.
    * @return The delegated vote power.
    */
    function votePowerFromToAt(
        address _from, 
        address _to, 
        uint256 _balance,
        uint _blockNumber
    ) external view returns(uint256);

    /**
     * @notice Compute the current undelegated vote power of `_owner`
     * @param _owner The address to get undelegated voting power.
     * @param _balance Owner's current balance
     * @return The unallocated vote power of `_owner`
     */
    function undelegatedVotePowerOf(
        address _owner,
        uint256 _balance
    ) external view returns(uint256);

    /**
     * @notice Get the undelegated vote power of `_owner` at given block.
     * @param _owner The address to get undelegated voting power.
     * @param _blockNumber The block number at which to fetch.
     * @return The undelegated vote power of `_owner` (= owner's own balance minus all delegations from owner)
     */
    function undelegatedVotePowerOfAt(
        address _owner, 
        uint256 _balance,
        uint256 _blockNumber
    ) external view returns(uint256);

    /**
     * @notice Get the delegation mode for '_who'. This mode determines whether vote power is
     *  allocated by percentage or by explicit value.
     * @param _who The address to get delegation mode.
     * @return Delegation mode (NOTSET=0, PERCENTAGE=1, AMOUNT=2))
     */
    function delegationModeOf(address _who) external view returns (uint256);
    
    /**
    * @notice Get the vote power delegation `_delegateAddresses` 
    *  and `pcts` of an `_owner`. Returned in two separate positional arrays.
    * @param _owner The address to get delegations.
    * @return _delegateAddresses Positional array of delegation addresses.
    * @return _bips Positional array of delegation percents specified in basis points (1/100 or 1 percent)
    * @return _count The number of delegates.
    * @return _delegationMode The mode of the delegation (NOTSET=0, PERCENTAGE=1, AMOUNT=2).
    */
    function delegatesOf(
        address _owner
    )
        external view 
        returns (
            address[] memory _delegateAddresses, 
            uint256[] memory _bips,
            uint256 _count,
            uint256 _delegationMode
        );

    /**
    * @notice Get the vote power delegation `delegationAddresses` 
    *  and `pcts` of an `_owner`. Returned in two separate positional arrays.
    * @param _owner The address to get delegations.
    * @param _blockNumber The block for which we want to know the delegations.
    * @return _delegateAddresses Positional array of delegation addresses.
    * @return _bips Positional array of delegation percents specified in basis points (1/100 or 1 percent)
    * @return _count The number of delegates.
    * @return _delegationMode The mode of the delegation (NOTSET=0, PERCENTAGE=1, AMOUNT=2).
    */
    function delegatesOfAt(
        address _owner,
        uint256 _blockNumber
    )
        external view 
        returns (
            address[] memory _delegateAddresses, 
            uint256[] memory _bips,
            uint256 _count,
            uint256 _delegationMode
        );

    /**
     * The VPToken (or some other contract) that owns this VPContract.
     * All state changing methods may be called only from this address.
     * This is because original msg.sender is sent in `_from` parameter
     * and we must be sure that it cannot be faked by directly calling VPContract.
     * Owner token is also used in case of replacement to recover vote powers from balances.
     */
    function ownerToken() external view returns (IVPToken);
    
    /**
     * Return true if this IIVPContract is configured to be used as a replacement for other contract.
     * It means that vote powers are not necessarily correct at the initialization, therefore
     * every method that reads vote power must check whether it is initialized for that address and block.
     */
    function isReplacement() external view returns (bool);
}
          

// SPDX-License-Identifier: MIT
pragma solidity >=0.7.6 <0.9;

import "../../userInterfaces/IVPToken.sol";
import "../../userInterfaces/IGovernanceVotePower.sol";
import "./IIVPContract.sol";
import "./IIGovernanceVotePower.sol";
import "./IICleanable.sol";

interface IIVPToken is IVPToken, IICleanable {
    /**
     * Set the contract that is allowed to set cleanupBlockNumber.
     * Usually this will be an instance of CleanupBlockNumberManager.
     */
    function setCleanupBlockNumberManager(address _cleanupBlockNumberManager) external;
    
    /**
     * Sets new governance vote power contract that allows token owners to participate in governance voting
     * and delegate governance vote power. 
     */
    function setGovernanceVotePower(IIGovernanceVotePower _governanceVotePower) external;
    
    /**
    * @notice Get the total vote power at block `_blockNumber` using cache.
    *   It tries to read the cached value and if not found, reads the actual value and stores it in cache.
    *   Can only be used if `_blockNumber` is in the past, otherwise reverts.    
    * @param _blockNumber The block number at which to fetch.
    * @return The total vote power at the block (sum of all accounts' vote powers).
    */
    function totalVotePowerAtCached(uint256 _blockNumber) external returns(uint256);
    
    /**
    * @notice Get the vote power of `_owner` at block `_blockNumber` using cache.
    *   It tries to read the cached value and if not found, reads the actual value and stores it in cache.
    *   Can only be used if _blockNumber is in the past, otherwise reverts.    
    * @param _owner The address to get voting power.
    * @param _blockNumber The block number at which to fetch.
    * @return Vote power of `_owner` at `_blockNumber`.
    */
    function votePowerOfAtCached(address _owner, uint256 _blockNumber) external returns(uint256);

    /**
     * Return vote powers for several addresses in a batch.
     * @param _owners The list of addresses to fetch vote power of.
     * @param _blockNumber The block number at which to fetch.
     * @return A list of vote powers.
     */    
    function batchVotePowerOfAt(
        address[] memory _owners, 
        uint256 _blockNumber
    ) external view returns(uint256[] memory);
}
          

// SPDX-License-Identifier: MIT
pragma solidity >=0.7.6 <0.9;

interface IFtso {
    enum PriceFinalizationType {
        // initial state
        NOT_FINALIZED,
        // median calculation used to find price
        WEIGHTED_MEDIAN,
        // low turnout - price calculated from median of trusted addresses
        TRUSTED_ADDRESSES,
        // low turnout + no votes from trusted addresses - price copied from previous epoch
        PREVIOUS_PRICE_COPIED,
        // price calculated from median of trusted addresses - triggered due to an exception
        TRUSTED_ADDRESSES_EXCEPTION,
        // previous price copied - triggered due to an exception
        PREVIOUS_PRICE_COPIED_EXCEPTION
    }

    event PriceRevealed(
        address indexed voter, uint256 indexed epochId, uint256 price, uint256 timestamp,
        uint256 votePowerNat, uint256 votePowerAsset
    );

    event PriceFinalized(
        uint256 indexed epochId, uint256 price, bool rewardedFtso,
        uint256 lowRewardPrice, uint256 highRewardPrice, PriceFinalizationType finalizationType,
        uint256 timestamp
    );

    event PriceEpochInitializedOnFtso(
        uint256 indexed epochId, uint256 endTime, uint256 timestamp
    );

    event LowTurnout(
        uint256 indexed epochId,
        uint256 natTurnout,
        uint256 lowNatTurnoutThresholdBIPS,
        uint256 timestamp
    );

    /**
     * @notice Returns if FTSO is active
     */
    function active() external view returns (bool);

    /**
     * @notice Returns the FTSO symbol
     */
    function symbol() external view returns (string memory);

    /**
     * @notice Returns current epoch id
     */
    function getCurrentEpochId() external view returns (uint256);

    /**
     * @notice Returns id of the epoch which was opened for price submission at the specified timestamp
     * @param _timestamp            Timestamp as seconds from unix epoch
     */
    function getEpochId(uint256 _timestamp) external view returns (uint256);
    
    /**
     * @notice Returns random number of the specified epoch
     * @param _epochId              Id of the epoch
     */
    function getRandom(uint256 _epochId) external view returns (uint256);

    /**
     * @notice Returns asset price consented in specific epoch
     * @param _epochId              Id of the epoch
     * @return Price in USD multiplied by ASSET_PRICE_USD_DECIMALS
     */
    function getEpochPrice(uint256 _epochId) external view returns (uint256);

    /**
     * @notice Returns current epoch data
     * @return _epochId                 Current epoch id
     * @return _epochSubmitEndTime      End time of the current epoch price submission as seconds from unix epoch
     * @return _epochRevealEndTime      End time of the current epoch price reveal as seconds from unix epoch
     * @return _votePowerBlock          Vote power block for the current epoch
     * @return _fallbackMode            Current epoch in fallback mode - only votes from trusted addresses will be used
     * @dev half-closed intervals - end time not included
     */
    function getPriceEpochData() external view returns (
        uint256 _epochId,
        uint256 _epochSubmitEndTime,
        uint256 _epochRevealEndTime,
        uint256 _votePowerBlock,
        bool _fallbackMode
    );

    /**
     * @notice Returns current epoch data
     * @return _firstEpochStartTs           First epoch start timestamp
     * @return _submitPeriodSeconds         Submit period in seconds
     * @return _revealPeriodSeconds         Reveal period in seconds
     */
    function getPriceEpochConfiguration() external view returns (
        uint256 _firstEpochStartTs,
        uint256 _submitPeriodSeconds,
        uint256 _revealPeriodSeconds
    );
    
    /**
     * @notice Returns asset price submitted by voter in specific epoch
     * @param _epochId              Id of the epoch
     * @param _voter                Address of the voter
     * @return Price in USD multiplied by ASSET_PRICE_USD_DECIMALS
     */
    function getEpochPriceForVoter(uint256 _epochId, address _voter) external view returns (uint256);

    /**
     * @notice Returns current asset price
     * @return _price               Price in USD multiplied by ASSET_PRICE_USD_DECIMALS
     * @return _timestamp           Time when price was updated for the last time
     */
    function getCurrentPrice() external view returns (uint256 _price, uint256 _timestamp);

    /**
     * @notice Returns current asset price details
     * @return _price                                   Price in USD multiplied by ASSET_PRICE_USD_DECIMALS
     * @return _priceTimestamp                          Time when price was updated for the last time
     * @return _priceFinalizationType                   Finalization type when price was updated for the last time
     * @return _lastPriceEpochFinalizationTimestamp     Time when last price epoch was finalized
     * @return _lastPriceEpochFinalizationType          Finalization type of last finalized price epoch
     */
    function getCurrentPriceDetails() external view returns (
        uint256 _price,
        uint256 _priceTimestamp,
        PriceFinalizationType _priceFinalizationType,
        uint256 _lastPriceEpochFinalizationTimestamp,
        PriceFinalizationType _lastPriceEpochFinalizationType
    );

    /**
     * @notice Returns current random number
     */
    function getCurrentRandom() external view returns (uint256);
}
          

// SPDX-License-Identifier: MIT
pragma solidity >=0.7.6 <0.9;
pragma abicoder v2;

import "../ftso/interface/IIFtso.sol";
import "../genesis/interface/IFtsoRegistryGenesis.sol";

interface IFtsoRegistry is IFtsoRegistryGenesis {

    function getFtso(uint256 _ftsoIndex) external view returns(IIFtso _activeFtsoAddress);
    function getFtsoBySymbol(string memory _symbol) external view returns(IIFtso _activeFtsoAddress);
    function getSupportedIndices() external view returns(uint256[] memory _supportedIndices);
    function getSupportedSymbols() external view returns(string[] memory _supportedSymbols);
    function getSupportedFtsos() external view returns(IIFtso[] memory _ftsos);
    function getFtsoIndex(string memory _symbol) external view returns (uint256 _assetIndex);
    function getFtsoSymbol(uint256 _ftsoIndex) external view returns (string memory _symbol);
    function getCurrentPrice(uint256 _ftsoIndex) external view returns(uint256 _price, uint256 _timestamp);
    function getCurrentPrice(string memory _symbol) external view returns(uint256 _price, uint256 _timestamp);

    function getSupportedIndicesAndFtsos() external view 
        returns(uint256[] memory _supportedIndices, IIFtso[] memory _ftsos);

    function getSupportedSymbolsAndFtsos() external view 
        returns(string[] memory _supportedSymbols, IIFtso[] memory _ftsos);

    function getSupportedIndicesAndSymbols() external view 
        returns(uint256[] memory _supportedIndices, string[] memory _supportedSymbols);

    function getSupportedIndicesSymbolsAndFtsos() external view 
        returns(uint256[] memory _supportedIndices, string[] memory _supportedSymbols, IIFtso[] memory _ftsos);
}
          

// SPDX-License-Identifier: MIT
pragma solidity 0.7.6;


/**
 * A special contract that holds Flare governance address.
 * This contract enables updating governance address and timelock only by hard forking the network,
 * meaning only by updating validator code.
 */
interface IGovernanceSettings {
    /**
     * Get the governance account address.
     * The governance address can only be changed by a hardfork.
     */
    function getGovernanceAddress() external view returns (address);
    
    /**
     * Get the time in seconds that must pass between a governance call and execution.
     * The timelock value can only be changed by a hardfork.
     */
    function getTimelock() external view returns (uint256);
    
    /**
     * Get the addresses of the accounts that are allowed to execute the timelocked governance calls
     * once the timelock period expires.
     * Executors can be changed without a hardfork, via a normal governance call.
     */
    function getExecutors() external view returns (address[] memory);
    
    /**
     * Check whether an address is one of the executors.
     */
    function isExecutor(address _address) external view returns (bool);
}
          

// SPDX-License-Identifier: MIT
pragma solidity >=0.7.6 <0.9;

interface IGovernanceVotePower {
    /**
     * @notice Delegate all governance vote power of `msg.sender` to `_to`.
     * @param _to The address of the recipient
     **/
    function delegate(address _to) external;

    /**
     * @notice Undelegate all governance vote power of `msg.sender``.
     **/
    function undelegate() external;

    /**
    * @notice Get the governance vote power of `_who` at block `_blockNumber`
    * @param _who The address to get voting power.
    * @param _blockNumber The block number at which to fetch.
    * @return _votePower    Governance vote power of `_who` at `_blockNumber`.
    */
    function votePowerOfAt(address _who, uint256 _blockNumber) external view returns(uint256);

    /**
    * @notice Get the vote power of `account` at the current block.
    * @param account The address to get voting power.
    * @return Vote power of `account` at the current block number.
    */    
    function getVotes(address account) external view returns (uint256);

    /**
    * @notice Get the delegate's address of `_who` at block `_blockNumber`
    * @param _who The address to get delegate's address.
    * @param _blockNumber The block number at which to fetch.
    * @return Delegate's address of `_who` at `_blockNumber`.
    */
    function getDelegateOfAt(address _who, uint256 _blockNumber) external view returns (address);

    /**
    * @notice Get the delegate's address of `_who` at the current block.
    * @param _who The address to get delegate's address.
    * @return Delegate's address of `_who` at the current block number.
    */    
    function getDelegateOfAtNow(address _who) external  view returns (address);

}
          

// SPDX-License-Identifier: MIT
pragma solidity >=0.7.6 <0.9;

import "../genesis/interface/IFtsoGenesis.sol";
import "../genesis/interface/IFtsoRegistryGenesis.sol";
import "../genesis/interface/IFtsoManagerGenesis.sol";

interface IPriceSubmitter {
    /**
     * Event emitted when hash was submitted through PriceSubmitter.
     * @param submitter the address of the sender
     * @param epochId current price epoch id
     * @param hash the submitted hash
     * @param timestamp current block timestamp
     */
    event HashSubmitted(
        address indexed submitter,
        uint256 indexed epochId,
        bytes32 hash,
        uint256 timestamp
    );

    /**
     * Event emitted when prices were revealed through PriceSubmitter.
     * @param voter the address of the sender
     * @param epochId id of the epoch in which the price hash was submitted
     * @param ftsos array of ftsos that correspond to the indexes in the call
     * @param prices the submitted prices
     * @param timestamp current block timestamp
     */
    event PricesRevealed(
        address indexed voter,
        uint256 indexed epochId,
        IFtsoGenesis[] ftsos,
        uint256[] prices,
        uint256 random,
        uint256 timestamp
    );
    
    /**
     * @notice Submits hash for current epoch
     * @param _epochId              Target epoch id to which hash is submitted
     * @param _hash                 Hash of ftso indices, prices, random number and voter address
     * @notice Emits HashSubmitted event
     */
    function submitHash(
        uint256 _epochId,
        bytes32 _hash
    ) external;

    /**
     * @notice Reveals submitted prices during epoch reveal period
     * @param _epochId              Id of the epoch in which the price hashes was submitted
     * @param _ftsoIndices          List of increasing ftso indices
     * @param _prices               List of submitted prices in USD
     * @param _random               Submitted random number
     * @notice The hash of ftso indices, prices, random number and voter address must be equal to the submitted hash
     * @notice Emits PricesRevealed event
     */
    function revealPrices(
        uint256 _epochId,
        uint256[] memory _ftsoIndices,
        uint256[] memory _prices,
        uint256 _random
    ) external;

    /**
     * Returns bitmap of all ftso's for which `_voter` is allowed to submit prices/hashes.
     * If voter is allowed to vote for ftso at index (see *_FTSO_INDEX), the corrsponding
     * bit in the result will be 1.
     */    
    function voterWhitelistBitmap(address _voter) external view returns (uint256);

    function getVoterWhitelister() external view returns (address);
    function getFtsoRegistry() external view returns (IFtsoRegistryGenesis);
    function getFtsoManager() external view returns (IFtsoManagerGenesis);

    /**
     * @notice Returns current random number
     */
    function getCurrentRandom() external view returns (uint256);
    
    /**
     * @notice Returns random number of the specified epoch
     * @param _epochId              Id of the epoch
     */
    function getRandom(uint256 _epochId) external view returns (uint256);
}
          

// SPDX-License-Identifier: MIT
pragma solidity >=0.7.6 <0.9;

interface IVPContractEvents {
    /**
     * Event triggered when an account delegates or undelegates another account. 
     * Definition: `votePowerFromTo(from, to)` is `changed` from `priorVotePower` to `newVotePower`.
     * For undelegation, `newVotePower` is 0.
     *
     * Note: the event is always emitted from VPToken's `writeVotePowerContract`.
     */
    event Delegate(address indexed from, address indexed to, uint256 priorVotePower, uint256 newVotePower);
    
    /**
     * Event triggered only when account `delegator` revokes delegation to `delegatee`
     * for a single block in the past (typically the current vote block).
     *
     * Note: the event is always emitted from VPToken's `writeVotePowerContract` and/or `readVotePowerContract`.
     */
    event Revoke(address indexed delegator, address indexed delegatee, uint256 votePower, uint256 blockNumber);
}
          

// SPDX-License-Identifier: MIT
pragma solidity >=0.7.6 <0.9;

import {IERC20} from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import {IGovernanceVotePower} from "./IGovernanceVotePower.sol";
import {IVPContractEvents} from "./IVPContractEvents.sol";

interface IVPToken is IERC20 {
    /**
     * @notice Delegate by percentage `_bips` of voting power to `_to` from `msg.sender`.
     * @param _to The address of the recipient
     * @param _bips The percentage of voting power to be delegated expressed in basis points (1/100 of one percent).
     *   Not cummulative - every call resets the delegation value (and value of 0 undelegates `to`).
     **/
    function delegate(address _to, uint256 _bips) external;
    
    /**
     * @notice Undelegate all percentage delegations from teh sender and then delegate corresponding 
     *   `_bips` percentage of voting power from the sender to each member of `_delegatees`.
     * @param _delegatees The addresses of the new recipients.
     * @param _bips The percentages of voting power to be delegated expressed in basis points (1/100 of one percent).
     *   Total of all `_bips` values must be at most 10000.
     **/
    function batchDelegate(address[] memory _delegatees, uint256[] memory _bips) external;
        
    /**
     * @notice Explicitly delegate `_amount` of voting power to `_to` from `msg.sender`.
     * @param _to The address of the recipient
     * @param _amount An explicit vote power amount to be delegated.
     *   Not cummulative - every call resets the delegation value (and value of 0 undelegates `to`).
     **/    
    function delegateExplicit(address _to, uint _amount) external;

    /**
    * @notice Revoke all delegation from sender to `_who` at given block. 
    *    Only affects the reads via `votePowerOfAtCached()` in the block `_blockNumber`.
    *    Block `_blockNumber` must be in the past. 
    *    This method should be used only to prevent rogue delegate voting in the current voting block.
    *    To stop delegating use delegate/delegateExplicit with value of 0 or undelegateAll/undelegateAllExplicit.
    * @param _who Address of the delegatee
    * @param _blockNumber The block number at which to revoke delegation.
    */
    function revokeDelegationAt(address _who, uint _blockNumber) external;
    
    /**
     * @notice Undelegate all voting power for delegates of `msg.sender`
     *    Can only be used with percentage delegation.
     *    Does not reset delegation mode back to NOTSET.
     **/
    function undelegateAll() external;
    
    /**
     * @notice Undelegate all explicit vote power by amount delegates for `msg.sender`.
     *    Can only be used with explicit delegation.
     *    Does not reset delegation mode back to NOTSET.
     * @param _delegateAddresses Explicit delegation does not store delegatees' addresses, 
     *   so the caller must supply them.
     * @return The amount still delegated (in case the list of delegates was incomplete).
     */
    function undelegateAllExplicit(address[] memory _delegateAddresses) external returns (uint256);


    /**
     * @dev Should be compatible with ERC20 method
     */
    function name() external view returns (string memory);

    /**
     * @dev Should be compatible with ERC20 method
     */
    function symbol() external view returns (string memory);

    /**
     * @dev Should be compatible with ERC20 method
     */
    function decimals() external view returns (uint8);
    

    /**
     * @notice Total amount of tokens at a specific `_blockNumber`.
     * @param _blockNumber The block number when the totalSupply is queried
     * @return The total amount of tokens at `_blockNumber`
     **/
    function totalSupplyAt(uint _blockNumber) external view returns(uint256);

    /**
     * @dev Queries the token balance of `_owner` at a specific `_blockNumber`.
     * @param _owner The address from which the balance will be retrieved.
     * @param _blockNumber The block number when the balance is queried.
     * @return The balance at `_blockNumber`.
     **/
    function balanceOfAt(address _owner, uint _blockNumber) external view returns (uint256);

    
    /**
     * @notice Get the current total vote power.
     * @return The current total vote power (sum of all accounts' vote powers).
     */
    function totalVotePower() external view returns(uint256);
    
    /**
    * @notice Get the total vote power at block `_blockNumber`
    * @param _blockNumber The block number at which to fetch.
    * @return The total vote power at the block  (sum of all accounts' vote powers).
    */
    function totalVotePowerAt(uint _blockNumber) external view returns(uint256);

    /**
     * @notice Get the current vote power of `_owner`.
     * @param _owner The address to get voting power.
     * @return Current vote power of `_owner`.
     */
    function votePowerOf(address _owner) external view returns(uint256);
    
    /**
    * @notice Get the vote power of `_owner` at block `_blockNumber`
    * @param _owner The address to get voting power.
    * @param _blockNumber The block number at which to fetch.
    * @return Vote power of `_owner` at `_blockNumber`.
    */
    function votePowerOfAt(address _owner, uint256 _blockNumber) external view returns(uint256);

    /**
    * @notice Get the vote power of `_owner` at block `_blockNumber`, ignoring revocation information (and cache).
    * @param _owner The address to get voting power.
    * @param _blockNumber The block number at which to fetch.
    * @return Vote power of `_owner` at `_blockNumber`. Result doesn't change if vote power is revoked.
    */
    function votePowerOfAtIgnoringRevocation(address _owner, uint256 _blockNumber) external view returns(uint256);

    /**
     * @notice Get the delegation mode for '_who'. This mode determines whether vote power is
     *  allocated by percentage or by explicit value. Once the delegation mode is set, 
     *  it never changes, even if all delegations are removed.
     * @param _who The address to get delegation mode.
     * @return delegation mode: 0 = NOTSET, 1 = PERCENTAGE, 2 = AMOUNT (i.e. explicit)
     */
    function delegationModeOf(address _who) external view returns(uint256);
        
    /**
    * @notice Get current delegated vote power `_from` delegator delegated `_to` delegatee.
    * @param _from Address of delegator
    * @param _to Address of delegatee
    * @return The delegated vote power.
    */
    function votePowerFromTo(address _from, address _to) external view returns(uint256);
    
    /**
    * @notice Get delegated the vote power `_from` delegator delegated `_to` delegatee at `_blockNumber`.
    * @param _from Address of delegator
    * @param _to Address of delegatee
    * @param _blockNumber The block number at which to fetch.
    * @return The delegated vote power.
    */
    function votePowerFromToAt(address _from, address _to, uint _blockNumber) external view returns(uint256);
    
    /**
     * @notice Compute the current undelegated vote power of `_owner`
     * @param _owner The address to get undelegated voting power.
     * @return The unallocated vote power of `_owner`
     */
    function undelegatedVotePowerOf(address _owner) external view returns(uint256);
    
    /**
     * @notice Get the undelegated vote power of `_owner` at given block.
     * @param _owner The address to get undelegated voting power.
     * @param _blockNumber The block number at which to fetch.
     * @return The undelegated vote power of `_owner` (= owner's own balance minus all delegations from owner)
     */
    function undelegatedVotePowerOfAt(address _owner, uint256 _blockNumber) external view returns(uint256);
    
    /**
    * @notice Get the vote power delegation `delegationAddresses` 
    *  and `_bips` of `_who`. Returned in two separate positional arrays.
    * @param _who The address to get delegations.
    * @return _delegateAddresses Positional array of delegation addresses.
    * @return _bips Positional array of delegation percents specified in basis points (1/100 or 1 percent)
    * @return _count The number of delegates.
    * @return _delegationMode The mode of the delegation (NOTSET=0, PERCENTAGE=1, AMOUNT=2).
    */
    function delegatesOf(address _who)
        external view 
        returns (
            address[] memory _delegateAddresses,
            uint256[] memory _bips,
            uint256 _count, 
            uint256 _delegationMode
        );
        
    /**
    * @notice Get the vote power delegation `delegationAddresses` 
    *  and `pcts` of `_who`. Returned in two separate positional arrays.
    * @param _who The address to get delegations.
    * @param _blockNumber The block for which we want to know the delegations.
    * @return _delegateAddresses Positional array of delegation addresses.
    * @return _bips Positional array of delegation percents specified in basis points (1/100 or 1 percent)
    * @return _count The number of delegates.
    * @return _delegationMode The mode of the delegation (NOTSET=0, PERCENTAGE=1, AMOUNT=2).
    */
    function delegatesOfAt(address _who, uint256 _blockNumber)
        external view 
        returns (
            address[] memory _delegateAddresses, 
            uint256[] memory _bips, 
            uint256 _count, 
            uint256 _delegationMode
        );

    /**
     * Returns VPContract used for readonly operations (view methods).
     * The only non-view method that might be called on it is `revokeDelegationAt`.
     *
     * @notice `readVotePowerContract` is almost always equal to `writeVotePowerContract`
     * except during upgrade from one VPContract to a new version (which should happen
     * rarely or never and will be anounced before).
     *
     * @notice You shouldn't call any methods on VPContract directly, all are exposed
     * via VPToken (and state changing methods are forbidden from direct calls). 
     * This is the reason why this method returns `IVPContractEvents` - it should only be used
     * for listening to events (`Revoke` only).
     */
    function readVotePowerContract() external view returns (IVPContractEvents);

    /**
     * Returns VPContract used for state changing operations (non-view methods).
     * The only non-view method that might be called on it is `revokeDelegationAt`.
     *
     * @notice `writeVotePowerContract` is almost always equal to `readVotePowerContract`
     * except during upgrade from one VPContract to a new version (which should happen
     * rarely or never and will be anounced before). In the case of upgrade,
     * `writeVotePowerContract` will be replaced first to establish delegations, and
     * after some perio (e.g. after a reward epoch ends) `readVotePowerContract` will be set equal to it.
     *
     * @notice You shouldn't call any methods on VPContract directly, all are exposed
     * via VPToken (and state changing methods are forbidden from direct calls). 
     * This is the reason why this method returns `IVPContractEvents` - it should only be used
     * for listening to events (`Delegate` and `Revoke` only).
     */
    function writeVotePowerContract() external view returns (IVPContractEvents);
    
    /**
     * When set, allows token owners to participate in governance voting
     * and delegate governance vote power.
     */
    function governanceVotePower() external view returns (IGovernanceVotePower);
}
          

// SPDX-License-Identifier: MIT
pragma solidity >=0.7.6 <0.9;

interface IVoterWhitelister {
    /**
     * Raised when an account is removed from the voter whitelist.
     */
    event VoterWhitelisted(address voter, uint256 ftsoIndex);
    
    /**
     * Raised when an account is removed from the voter whitelist.
     */
    event VoterRemovedFromWhitelist(address voter, uint256 ftsoIndex);

    /**
     * Request to whitelist `_voter` account to ftso at `_ftsoIndex`. Will revert if vote power too low.
     * May be called by any address.
     */
    function requestWhitelistingVoter(address _voter, uint256 _ftsoIndex) external;

    /**
     * Request to whitelist `_voter` account to all active ftsos.
     * May be called by any address.
     * It returns an array of supported ftso indices and success flag per index.
     */
    function requestFullVoterWhitelisting(
        address _voter
    ) 
        external 
        returns (
            uint256[] memory _supportedIndices,
            bool[] memory _success
        );

    /**
     * Maximum number of voters in the whitelist for a new FTSO.
     */
    function defaultMaxVotersForFtso() external view returns (uint256);
    
    /**
     * Maximum number of voters in the whitelist for FTSO at index `_ftsoIndex`.
     */
    function maxVotersForFtso(uint256 _ftsoIndex) external view returns (uint256);

    /**
     * Get whitelisted price providers for ftso with `_symbol`
     */
    function getFtsoWhitelistedPriceProvidersBySymbol(string memory _symbol) external view returns (address[] memory);

    /**
     * Get whitelisted price providers for ftso at `_ftsoIndex`
     */
    function getFtsoWhitelistedPriceProviders(uint256 _ftsoIndex) external view returns (address[] memory);
}
          

// SPDX-License-Identifier: MIT

pragma solidity 0.7.6;
import {SafeMath} from "@openzeppelin/contracts/math/SafeMath.sol";

/**
 * @dev Compute percentages safely without phantom overflows.
 *
 * Intermediate operations can overflow even when the result will always
 * fit into computed type. Developers usually
 * assume that overflows raise errors. `SafePct` restores this intuition by
 * reverting the transaction when such an operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 *
 * Can be combined with {SafeMath} and {SignedSafeMath} to extend it to smaller types, by performing
 * all math on `uint256` and `int256` and then downcasting.
 */
library SafePct {
    using SafeMath for uint256;
    /**
     * Requirements:
     *
     * - intermediate operations must revert on overflow
     */
    function mulDiv(uint256 x, uint256 y, uint256 z) internal pure returns (uint256) {
        require(z > 0, "Division by zero");

        if (x == 0) return 0;
        uint256 xy = x * y;
        if (xy / x == y) { // no overflow happened - same as in SafeMath mul
            return xy / z;
        }

        //slither-disable-next-line divide-before-multiply
        uint256 a = x / z;
        uint256 b = x % z; // x = a * z + b

        //slither-disable-next-line divide-before-multiply
        uint256 c = y / z;
        uint256 d = y % z; // y = c * z + d

        return (a.mul(c).mul(z)).add(a.mul(d)).add(b.mul(c)).add(b.mul(d).div(z));
    }
}
          

// SPDX-License-Identifier: MIT
pragma solidity >=0.7.6 <0.9;

import "../../userInterfaces/IVoterWhitelister.sol";


interface IIVoterWhitelister is IVoterWhitelister {
    /**
     * Set the maximum number of voters in the whitelist for FTSO at index `_ftsoIndex`.
     * Possibly removes several voters with the least votepower from the whitelist.
     * Only governance can call this method.
     */
    function setMaxVotersForFtso(uint256 _ftsoIndex, uint256 _newMaxVoters) external;

    /**
     * Set the maximum number of voters in the whitelist for a new FTSO.
     * Only governance can call this method.
     */
    function setDefaultMaxVotersForFtso(uint256 _defaultMaxVotersForFtso) external;

    /**
     * Create whitelist with default size for ftso.
     * Only ftso manager can call this method.
     */
    function addFtso(uint256 _ftsoIndex) external;
    
    /**
     * Clear whitelist for ftso at `_ftsoIndex`.
     * Only ftso manager can call this method.
     */
    function removeFtso(uint256 _ftsoIndex) external;

    /**
     * Remove `_trustedAddress` from whitelist for ftso at `_ftsoIndex`.
     */
    function removeTrustedAddressFromWhitelist(address _trustedAddress, uint256 _ftsoIndex) external;
}
          

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        uint256 c = a + b;
        if (c < a) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the substraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b > a) return (false, 0);
        return (true, a - b);
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) return (true, 0);
        uint256 c = a * b;
        if (c / a != b) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a / b);
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a % b);
    }

    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");
        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a, "SafeMath: subtraction overflow");
        return a - b;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        if (a == 0) return 0;
        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");
        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: division by zero");
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: modulo by zero");
        return a % b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        return a - b;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryDiv}.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a % b;
    }
}
          

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}