contract MixinStakingPool is
    MixinAbstract,
    MixinStakingPoolRewards
{
    using LibSafeMath for uint256;
    using LibSafeDowncast for uint256;

    /// @dev Asserts that the sender is the operator of the input pool.
    /// @param poolId Pool sender must be operator of.
    modifier onlyStakingPoolOperator(bytes32 poolId) {
        _assertSenderIsPoolOperator(poolId);
        _;
    }

    /// @dev Create a new staking pool. The sender will be the operator of this pool.
    /// Note that an operator must be payable.
    /// @param operatorShare Portion of rewards owned by the operator, in ppm.
    /// @param addOperatorAsMaker Adds operator to the created pool as a maker for convenience iff true.
    /// @return poolId The unique pool id generated for this pool.
    function createStakingPool(uint32 operatorShare, bool addOperatorAsMaker)
        external
        returns (bytes32 poolId)
    {
        // note that an operator must be payable
        address operator = msg.sender;

        // compute unique id for this pool
        poolId = lastPoolId = bytes32(uint256(lastPoolId).safeAdd(1));

        // sanity check on operator share
        _assertNewOperatorShare(
            poolId,
            PPM_DENOMINATOR,    // max operator share
            operatorShare
        );

        // create and store pool
        IStructs.Pool memory pool = IStructs.Pool({
            operator: operator,
            operatorShare: operatorShare
        });
        _poolById[poolId] = pool;

        // Staking pool has been created
        emit StakingPoolCreated(poolId, operator, operatorShare);

        if (addOperatorAsMaker) {
            joinStakingPoolAsMaker(poolId);
        }

        return poolId;
    }

    /// @dev Decreases the operator share for the given pool (i.e. increases pool rewards for members).
    /// @param poolId Unique Id of pool.
    /// @param newOperatorShare The newly decreased percentage of any rewards owned by the operator.
    function decreaseStakingPoolOperatorShare(bytes32 poolId, uint32 newOperatorShare)
        external
        onlyStakingPoolOperator(poolId)
    {
        // load pool and assert that we can decrease
        uint32 currentOperatorShare = _poolById[poolId].operatorShare;
        _assertNewOperatorShare(
            poolId,
            currentOperatorShare,
            newOperatorShare
        );

        // decrease operator share
        _poolById[poolId].operatorShare = newOperatorShare;
        emit OperatorShareDecreased(
            poolId,
            currentOperatorShare,
            newOperatorShare
        );
    }

    /// @dev Allows caller to join a staking pool as a maker.
    /// @param poolId Unique id of pool.
    function joinStakingPoolAsMaker(bytes32 poolId)
        public
    {
        address maker = msg.sender;
        poolIdByMaker[maker] = poolId;
        emit MakerStakingPoolSet(
            maker,
            poolId
        );
    }

    /// @dev Returns a staking pool
    /// @param poolId Unique id of pool.
    function getStakingPool(bytes32 poolId)
        public
        view
        returns (IStructs.Pool memory)
    {
        return _poolById[poolId];
    }

    /// @dev Reverts iff a staking pool does not exist.
    /// @param poolId Unique id of pool.
    function _assertStakingPoolExists(bytes32 poolId)
        internal
        view
    {
        if (_poolById[poolId].operator == NIL_ADDRESS) {
            // we use the pool's operator as a proxy for its existence
            LibRichErrors.rrevert(
                LibStakingRichErrors.PoolExistenceError(
                    poolId,
                    false
                )
            );
        }
    }

    /// @dev Reverts iff the new operator share is invalid.
    /// @param poolId Unique id of pool.
    /// @param currentOperatorShare Current operator share.
    /// @param newOperatorShare New operator share.
    function _assertNewOperatorShare(
        bytes32 poolId,
        uint32 currentOperatorShare,
        uint32 newOperatorShare
    )
        private
        pure
    {
        // sanity checks
        if (newOperatorShare > PPM_DENOMINATOR) {
            // operator share must be a valid fraction
            LibRichErrors.rrevert(LibStakingRichErrors.OperatorShareError(
                LibStakingRichErrors.OperatorShareErrorCodes.OperatorShareTooLarge,
                poolId,
                newOperatorShare
            ));
        } else if (newOperatorShare >= currentOperatorShare) {
            // new share must be less than the current share
            LibRichErrors.rrevert(LibStakingRichErrors.OperatorShareError(
                LibStakingRichErrors.OperatorShareErrorCodes.CanOnlyDecreaseOperatorShare,
                poolId,
                newOperatorShare
            ));
        }
    }

    /// @dev Asserts that the sender is the operator of the input pool.
    /// @param poolId Pool sender must be operator of.
    function _assertSenderIsPoolOperator(bytes32 poolId)
        private
        view
    {
        address operator = _poolById[poolId].operator;
        if (msg.sender != operator) {
            LibRichErrors.rrevert(
                LibStakingRichErrors.OnlyCallableByPoolOperatorError(
                    msg.sender,
                    poolId
                )
            );
        }
    }
}
function _assertStakingPoolExists(bytes32 poolId)
        internal
        view
    {
        if (_poolById[poolId].operator == NIL_ADDRESS) {
            // we use the pool's operator as a proxy for its existence
            LibRichErrors.rrevert(
                LibStakingRichErrors.PoolExistenceError(
                    poolId,
                    false
                )
            );
        }
    }
/// @dev Reverts iff a staking pool does not exist.
/// @param poolId Unique id of pool.