// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.9;

import "./IDelegationTerms.sol";

/**
 * @title The interface for the primary delegation contract for EigenLayr.
 * @author Layr Labs, Inc.
 * @notice  This is the contract for delegation in EigenLayr. The main functionalities of this contract are
 * - enabling anyone to register as an operator in EigenLayr
 * - allowing new operators to provide a DelegationTerms-type contract, which may mediate their interactions with stakers who delegate to them
 * - enabling any staker to delegate its stake to the operator of its choice
 * - enabling a staker to undelegate its assets from an operator (performed as part of the withdrawal process, initiated through the InvestmentManager)
 */
interface IEigenLayrDelegation {

    /**
     * @notice This will be called by an operator to register itself as an operator that stakers can choose to delegate to.
     * @param dt is the `DelegationTerms` contract that the operator has for those who delegate to them.
     * @dev An operator can set `dt` equal to their own address (or another EOA address), in the event that they want to split payments
     * in a more 'trustful' manner.
     * @dev In the present design, once set, there is no way for an operator to ever modify the address of their DelegationTerms contract.
     */
    function registerAsOperator(IDelegationTerms dt) external;

    /**
     *  @notice This will be called by a staker to delegate its assets to some operator.
     *  @param operator is the operator to whom staker (msg.sender) is delegating its assets
     */
    function delegateTo(address operator) external;

    /**
     * @notice Delegates from `staker` to `operator`.
     * @dev requires that r, vs are a valid ECSDA signature from `staker` indicating their intention for this action
     */
    function delegateToBySignature(address staker, address operator, uint256 expiry, bytes32 r, bytes32 vs) external;

    /**
     * @notice Undelegates `staker` from the operator who they are delegated to.
     * @notice Callable only by the InvestmentManager
     * @dev Should only ever be called in the event that the `staker` has no active deposits in EigenLayer.
     */
    function undelegate(address staker) external;

    /// @notice returns the address of the operator that `staker` is delegated to.
    function delegatedTo(address staker) external view returns (address);

    /// @notice returns the DelegationTerms of the `operator`, which may mediate their interactions with stakers who delegate to them.
    function delegationTerms(address operator) external view returns (IDelegationTerms);

    /// @notice returns the total number of shares in `strategy` that are delegated to `operator`.
    function operatorShares(address operator, IInvestmentStrategy strategy) external view returns (uint256);

    /**
     * @notice Increases the `staker`'s delegated shares in `strategy` by `shares, typically called when the staker has further deposits into EigenLayr
     * @dev Callable only by the InvestmentManager
     */
    function increaseDelegatedShares(address staker, IInvestmentStrategy strategy, uint256 shares) external;

    /**
     * @notice Decreases the `staker`'s delegated shares in each entry of `strategies` by its respective `shares[i]`, typically called when the staker withdraws from EigenLayr
     * @dev Callable only by the InvestmentManager
     */
    function decreaseDelegatedShares(
        address staker,
        IInvestmentStrategy[] calldata strategies,
        uint256[] calldata shares
    ) external;

    /// @notice Returns 'true' if `staker` *is* actively delegated, and 'false' otherwise.
    function isDelegated(address staker) external view returns (bool);

    /// @notice Returns 'true' if `staker` is *not* actively delegated, and 'false' otherwise.
    function isNotDelegated(address staker) external returns (bool);

    /// @notice Returns if an operator can be delegated to, i.e. it has called `registerAsOperator`.
    function isOperator(address operator) external view returns (bool);
}