// SPDX-License-Identifier: GPL-2.0-or-later

pragma solidity >=0.8.0;

import './IElection.sol';
import './IStake.sol';

/// @dev MajorCandidates interface
/// @author Alexandas
interface IMajorCandidates {

	/// @dev emit when max major candidates changed
	/// @param max max major candidates
	event MaxMajorCandidateUpdated(uint256 max);

	/// @dev emit when `Election` contract changed
	/// @param election `Election` contract address
	event ElectionUpdated(IElection election);

	/// @dev emit when `Stake` contract updated
	/// @param stake `Stake` contract 
	event StakeUpdated(IStake stake);

	/// @dev emit when a candidate insert or update in the sorted list
	/// @param candidate candidate address
	/// @param amount candidate votes
	event UpsetCandidate(address candidate, uint256 amount);

	/// @dev emit when a candidate removed from the sorted list
	/// @param candidate candidate address
	event RemoveCandidate(address candidate);

	/// @dev insert or update a candidate in the sorted list
	/// @param candidate candidate address
	/// @param amount candidate votes
	/// @param anchor anchor candidate address
	/// @param maxSlippage maximum rank change value for the candidate from the anchor candidate
	function upsetCandidateWithAnchor(
		address candidate,
		uint256 amount,
		address anchor,
		uint256 maxSlippage
	) external;

	/// @dev emit removed a candidate from the sorted list
	/// @param candidate candidate address
	function remove(address candidate) external;

	/// @dev return max major candidates
	function MAX_MAJOR_CANDIDATES() external view returns(uint256);

	/// @dev return `Election` contract address
	function election() external view returns(IElection);

	/// @dev return `Stake` contract address
	function stake() external view returns(IStake);

	/// @dev return whether a candidate is existed in the sorted list
	/// @param candidate candidate address
	/// @return whether the candidate is existed in the sorted list
	function exists(address candidate) external view returns (bool);

	/// @dev return whether a candidate is a major candidate
	/// @param candidate candidate address
	/// @return existed the candidate is a major candidate
	function isMajor(address candidate) external view returns(bool existed);

	/// @dev return all major candidates
	/// @return majors all major candidates
	function majorCandidateList() external view returns(address[] memory majors);


}