// SPDX-License-Identifier: AGPL-3.0-only
pragma solidity >=0.8.4 <0.9.0;

/**
  @title Governable contract
  @notice Manages the governance role
 */
interface IPriceGovernable {
  /*///////////////////////////////////////////////////////////////
                              EVENTS
  //////////////////////////////////////////////////////////////*/

  /**
    @notice Emitted when pendingGovernance accepts to be governance
    @param _governance Address of the new governance
   */
  event GovernanceSet(address _governance);

  /**
    @notice Emitted when new governance is proposed
    @param _pendingGovernance The address proposed to be the new governance
   */
  event GovernanceProposal(address _pendingGovernance);

  /*///////////////////////////////////////////////////////////////
                              ERRORS
  //////////////////////////////////////////////////////////////*/

  /**
    @notice Thrown when the caller of the function is not governance
   */
  error PriceGovernable_OnlyGovernance();

  /**
    @notice Thrown when the caller of the function is not pendingGovernance
   */
  error PriceGovernable_OnlyPendingGovernance();

  /**
    @notice Thrown when trying to set governance to zero address
   */
  error PriceGovernable_NoGovernanceZeroAddress();

  /*///////////////////////////////////////////////////////////////
                            VARIABLES
  //////////////////////////////////////////////////////////////*/

  /**
    @notice Returns the governance address
    @return _governance The governance address
   */
  function governance() external view returns (address _governance);

  /**
    @notice Returns the pendingGovernance address
    @return _pendingGovernance The pendingGovernance address
   */
  function pendingGovernance() external view returns (address _pendingGovernance);

  /*///////////////////////////////////////////////////////////////
                              LOGIC
  //////////////////////////////////////////////////////////////*/

  /**
    @notice Proposes a new address to be governance
    @param _governance The address being proposed as the new governance
   */
  function setGovernance(address _governance) external;

  /**
    @notice Changes the governance from the current one to the previously proposed address
   */
  function acceptGovernance() external;
}