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

/**
 * WNatDelegationFee interface.
 */
interface IWNatDelegationFee {
    /// Event emitted when a voter fee percentage value is changed.
    event FeePercentageChanged(
        address indexed voter,
        uint16 value,
        uint24 validFromEpochId
    );

    /// Reverts when the fee percentage update offset is not strictly greater than 1.
    error OffsetTooSmall();
    /// Reverts when the minimum fee percentage exceeds 100% (MAX_BIPS).
    error MinFeePercentageInvalid();
    /// Reverts when the default fee percentage is outside [minFeeBIPS, MAX_BIPS].
    error DefaultFeePercentageInvalid();
    /// Reverts when a voter sets a fee percentage outside [minFeeBIPS, MAX_BIPS].
    error FeePercentageInvalid();
    /// Reverts when querying the fee percentage for a future reward epoch beyond the update offset.
    error InvalidRewardEpochId();

    /**
     * Allows voter to set (or update last) fee percentage.
     * @param _feePercentageBIPS Number representing fee percentage in BIPS.
     * @return Returns the reward epoch number when the value becomes effective.
     */
    function setVoterFeePercentage(
        uint16 _feePercentageBIPS
    ) external returns (uint256);

    /// The offset in reward epochs for the fee percentage value to become effective.
    function feePercentageUpdateOffset() external view returns (uint24);

    /// The default fee percentage value.
    function defaultFeePercentageBIPS() external view returns (uint16);

    /// The minimum fee percentage value voters can set (in BIPS).
    function minFeeBIPS() external view returns (uint16);

    /**
     * Returns the current fee percentage of `_voter`.
     * @param _voter Voter address.
     */
    function getVoterCurrentFeePercentage(
        address _voter
    ) external view returns (uint16);

    /**
     * Returns the fee percentage of `_voter` for given reward epoch id.
     * @param _voter Voter address.
     * @param _rewardEpochId Reward epoch id.
     * **NOTE:** fee percentage might still change for the `current + feePercentageUpdateOffset` reward epoch id
     */
    function getVoterFeePercentage(
        address _voter,
        uint256 _rewardEpochId
    ) external view returns (uint16);

    /**
     * Returns the scheduled fee percentage changes of `_voter`.
     * @param _voter Voter address.
     * @return _feePercentageBIPS Positional array of fee percentages in BIPS.
     * @return _validFromEpochId Positional array of reward epoch ids the fee setings are effective from.
     * @return _fixed Positional array of boolean values indicating if settings are subjected to change.
     */
    function getVoterScheduledFeePercentageChanges(
        address _voter
    )
        external
        view
        returns (
            uint256[] memory _feePercentageBIPS,
            uint256[] memory _validFromEpochId,
            bool[] memory _fixed
        );
}