// SPDX-License-Identifier: GPL-3.0

pragma solidity 0.8.6;

library RingBufferLib {
    /**
    * @notice Returns wrapped TWAB index.
    * @dev  In order to navigate the TWAB circular buffer, we need to use the modulo operator.
    * @dev  For example, if `_index` is equal to 32 and the TWAB circular buffer is of `_cardinality` 32,
    *       it will return 0 and will point to the first element of the array.
    * @param _index Index used to navigate through the TWAB circular buffer.
    * @param _cardinality TWAB buffer cardinality.
    * @return TWAB index.
    */
    function wrap(uint256 _index, uint256 _cardinality) internal pure returns (uint256) {
        return _index % _cardinality;
    }

    /**
    * @notice Computes the negative offset from the given index, wrapped by the cardinality.
    * @dev  We add `_cardinality` to `_index` to be able to offset even if `_amount` is superior to `_cardinality`.
    * @param _index The index from which to offset
    * @param _amount The number of indices to offset.  This is subtracted from the given index.
    * @param _cardinality The number of elements in the ring buffer
    * @return Offsetted index.
     */
    function offset(
        uint256 _index,
        uint256 _amount,
        uint256 _cardinality
    ) internal pure returns (uint256) {
        return wrap(_index + _cardinality - _amount, _cardinality);
    }

    /// @notice Returns the index of the last recorded TWAB
    /// @param _nextIndex The next available twab index.  This will be recorded to next.
    /// @param _cardinality The cardinality of the TWAB history.
    /// @return The index of the last recorded TWAB
    function newestIndex(uint256 _nextIndex, uint256 _cardinality)
        internal
        pure
        returns (uint256)
    {
        if (_cardinality == 0) {
            return 0;
        }

        return wrap(_nextIndex + _cardinality - 1, _cardinality);
    }

    /// @notice Computes the ring buffer index that follows the given one, wrapped by cardinality
    /// @param _index The index to increment
    /// @param _cardinality The number of elements in the Ring Buffer
    /// @return The next index relative to the given index.  Will wrap around to 0 if the next index == cardinality
    function nextIndex(uint256 _index, uint256 _cardinality)
        internal
        pure
        returns (uint256)
    {
        return wrap(_index + 1, _cardinality);
    }
}