feat(incentives): add interface (#1678)

**Motivation:**

We need approval on initial design of the upcoming incentives council
feature release. Historically, we've used
[EigenHopper](https://github.com/Layr-Labs/EigenHopper/tree/master) for
token emissions. Now we're looking to make some improvements.

**Modifications:**

- Drafted a consolidated interface that combines the two `EigenHopper`
contracts into a single new contract.

**Result:**

Single consolidated interface with hopper functionality and proposed
ELIP-012 functionality.

Author: 0xClandestine

src/contracts/interfaces/IEmissionsController.sol

@@ -0,0 +1,176 @@
+// SPDX-License-Identifier: BUSL-1.1
+pragma solidity >=0.5.0;
+
+/// @title IEmissionsControllerErrors
+/// @notice Errors for the IEmissionsController contract.
+interface IEmissionsControllerErrors {
+    // TODO: Define with implementation.
+
+    }
+
+/// @title IEmissionsControllerTypes
+/// @notice Types for the IEmissionsController contract.
+interface IEmissionsControllerTypes {
+    /// @notice Distribution types as defined in the ELIP.
+    /// @dev Ref: "Distribution Submission types may include: createRewardsForAllEarners, createOperatorSetTotalStakeRewardsSubmission, createOperatorSetUniqueStakeRewardsSubmission, EigenDA Distribution, Manual Distribution."
+    enum DistributionType {
+        RewardsForAllEarners,
+        OperatorSetTotalStake,
+        OperatorSetUniqueStake,
+        EigenDA,
+        Manual
+    }
+
+    /// @notice A Distribution structure containing weight, type and strategies.
+    /// @dev Ref: "A Distribution consists of N fields: Weight, Distribution-type, Strategies and Multipliers."
+    struct Distribution {
+        /// The bips denominated weight of the distribution.
+        uint256 weight;
+        /// The type of distribution.
+        DistributionType distributionType;
+        /// The encoded rewards submission (either `RewardsSubmission` or `OperatorDirectedRewardsSubmission`).
+        bytes encodedRewardsSubmission;
+    }
+}
+
+/// @title IEmissionsControllerEvents
+/// @notice Events for the IEmissionsController contract.
+interface IEmissionsControllerEvents is IEmissionsControllerTypes {
+    /// @notice Emitted when a distribution is updated.
+    /// @param distributionId The id of the distribution.
+    /// @param distribution The distribution.
+    event DistributionUpdated(uint256 indexed distributionId, Distribution distribution);
+
+    /// @notice Emitted when a distribution is added.
+    /// @param distributionId The id of the distribution.
+    /// @param distribution The distribution.
+    event DistributionAdded(uint256 indexed distributionId, Distribution distribution);
+
+    /// @notice Emitted when a distribution is removed.
+    /// @param distributionId The id of the distribution.
+    event DistributionRemoved(uint256 indexed distributionId);
+
+    /// @notice Emitted when the Incentive Council address is updated.
+    /// @param incentiveCouncil The new Incentive Council address.
+    event IncentiveCouncilUpdated(address indexed incentiveCouncil);
+
+    /// @notice Emitted when the inflation rate is updated.
+    /// @param inflationRate The new inflation rate.
+    event InflationRateUpdated(uint256 indexed inflationRate);
+}
+
+/// @title IEmissionsController
+/// @notice Interface for the EmissionsController contract, which acts as the upgraded ActionGenerator.
+/// @dev Ref: "This proposal requires upgrades to the TokenHopper and Action Generator contracts."
+interface IEmissionsController is IEmissionsControllerErrors, IEmissionsControllerEvents {
+    /// -----------------------------------------------------------------------
+    /// Constants
+    /// -----------------------------------------------------------------------
+    /// @notice The rate of inflation for emissions.
+    /// @dev Immutable/constant variable that requires an upgrade to modify.
+    function EMISSIONS_INFLATION_RATE() external view returns (uint256);
+
+    /// @notice The start time of the emissions.
+    /// @dev Immutable/constant variable that requires an upgrade to modify.
+    function EMISSIONS_START_TIME() external view returns (uint256);
+
+    /// @notice The cooldown seconds of the emissions.
+    /// @dev Immutable/constant variable that requires an upgrade to modify.
+    function EMISSIONS_COOLDOWN_SECONDS() external view returns (uint256);
+
+    /// -----------------------------------------------------------------------
+    /// Initialization Functions
+    /// -----------------------------------------------------------------------
+
+    /// @notice Initializes the contract.
+    /// @param incentiveCouncil The initial Incentive Council address.
+    function initialize(
+        address incentiveCouncil
+    ) external;
+
+    /// -----------------------------------------------------------------------
+    /// Permissionless Trigger
+    /// -----------------------------------------------------------------------
+
+    /// @notice Triggers the weekly emissions.
+    /// @dev Try/catch is used to prevent a single reverting rewards submission from halting emissions.
+    /// @dev Pagination is used to prevent out-of-gas errors; multiple calls may be needed to process all submissions.
+    /// @dev Ref: "The ActionGenerator today is a contract ... that is triggered by the Hopper. When triggered, it mints new EIGEN tokens..."
+    /// @dev Permissionless function that can be called by anyone when `isButtonPressable()` returns true.
+    function pressButton() external;
+
+    /// -----------------------------------------------------------------------
+    /// Protocol Council Functions
+    /// -----------------------------------------------------------------------
+
+    /// @notice Sets the Incentive Council address.
+    /// @dev Only the Protocol Council can call this function.
+    /// @dev Ref: "Protocol Council Functions: Set Incentive Council multisig address that can interface with the ActionGenerator..."
+    /// @param incentiveCouncil The new Incentive Council address.
+    function setIncentiveCouncil(
+        address incentiveCouncil
+    ) external;
+
+    /// -----------------------------------------------------------------------
+    /// Incentive Council Functions
+    /// -----------------------------------------------------------------------
+
+    /// @notice Adds a new distribution.
+    /// @dev Only the Incentive Council can call this function.
+    /// @dev Ref: "Incentive Council Functions: addDistribution(weight{int}, distribution-type{see below}, strategiesAndMultipliers())"
+    /// @param distribution The distribution to add.
+    /// @return distributionId The id of the added distribution.
+    function addDistribution(
+        Distribution calldata distribution
+    ) external returns (uint256 distributionId);
+
+    /// @notice Updates an existing distribution.
+    /// @dev Only the Incentive Council can call this function.
+    /// @dev Ref: "Incentive Council Functions: updateDistribution(distributionId)"
+    /// @param distributionId The id of the distribution to update.
+    /// @param distribution The new distribution.
+    function updateDistribution(
+        uint256 distributionId,
+        Distribution calldata distribution
+    ) external;
+
+    /// @notice Cancels a distribution.
+    /// @dev The distribution remains in storage, but is marked as cancelled.
+    /// @dev Only the Incentive Council can call this function.
+    /// @dev Ref: Implied by "updateDistribution" and general management of distributions.
+    /// @param distributionId The id of the distribution to remove.
+    function removeDistribution(
+        uint256 distributionId
+    ) external;
+
+    /// -----------------------------------------------------------------------
+    /// View
+    /// -----------------------------------------------------------------------
+
+    /// @notice Checks if the emissions can be triggered.
+    /// @return True if the cooldown has passed and the system is ready.
+    function isButtonPressable() external view returns (bool);
+
+    /// @notice Returns the next button press time.
+    /// @return The next button press time.
+    function nextButtonPressTime() external view returns (uint256);
+
+    /// @notice Returns the last button press time.
+    /// @return The last button press time.
+    function lastButtonPressTime() external view returns (uint256);
+
+    /// @notice Returns a distribution by index.
+    /// @param distributionId The id of the distribution.
+    /// @return The Distribution struct at the given index.
+    function getDistribution(
+        uint256 distributionId
+    ) external view returns (Distribution memory);
+
+    /// @notice Returns all distributions.
+    /// @return An append-only array of Distribution structs.
+    function getDistributions() external view returns (Distribution[] memory);
+
+    /// @notice Returns the current Incentive Council address.
+    /// @return The Incentive Council address.
+    function getIncentiveCouncil() external view returns (address);
+}