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

pragma solidity >=0.8.0;

import './IRewarder.sol';
import './IStake.sol';
import './IMajorCandidates.sol';
import './IERC20.sol';

/// @dev Election contract interface
/// @author Alexandas
interface IElection {

	/// @dev emit when ERC20 token address updated
	/// @param token ERC20 token address
	event TokenUpdated(IERC20 token);

	/// @dev emit when `Rewarder` contract updated
	/// @param rewarder `Rewarder` contract 
	event RewarderUpdated(IRewarder rewarder);

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

	/// @dev emit when `MajorCandidates` contract updated
	/// @param majorCandidates `MajorCandidates` contract 
	event MajorCandidatesUpdated(IMajorCandidates majorCandidates);

	/// @dev emit when vote frozen period updated
	/// @param period vote frozen period
	event VoteFrozenPeriodUpdated(uint256 period);

	/// @dev emit when shares updated for a specific candidate
	/// @param candidate candidate address
	event ShareUpdated(address candidate);

	/// @dev emit when voter voted for a candidate
	/// @param candidate candidate address
	/// @param voter voter address
	/// @param amount token amount
	event Vote(address candidate, address voter, uint256 amount);

	/// @dev emit when voter claimed the reward
	/// @param candidate candidate address
	/// @param voter voter address
	/// @param to receiver address
	/// @param amount reward amount
	event Claimed(address candidate, address voter, address to, uint256 amount);

	/// @dev emit when voter withdrawn the votes
	/// @param candidate candidate address
	/// @param voter voter address
	/// @param to receiver address
	/// @param amount reward amount
	event Withdrawn(address candidate, address voter, address to, uint256 amount);

	/// @dev voter vote a specific candidate
	/// @param candidate candidate address
	/// @param voter voter address
	/// @param amount reward amount
	/// @param anchor anchor candidate address
	/// @param maxSlippage maximum rank change value for the candidate from the anchor candidate
	function vote(
		address candidate,
		address voter,
		uint256 amount,
		address anchor,
		uint256 maxSlippage
	) external;

	/// @dev voter claim reward for a specific candidate
	/// @param candidate candidate address
	/// @param to receiver address
	function claim(address candidate, address to) external;

	/// @dev voter withdraw reward for a specific candidate
	/// @param candidate candidate address
	/// @param amount reward amount
	/// @param to receiver address
	/// @param anchor anchor candidate address
	/// @param maxSlippage maximum rank change value for the candidate from the anchor candidate
	function withdraw(
		address candidate,
		uint256 amount,
		address to,
		address anchor,
		uint256 maxSlippage
	) external;

	/// @dev voter withdraw votes and claim reward for a specific candidate
	/// @param candidate candidate address
	/// @param amount reward amount
	/// @param to receiver address
	/// @param anchor anchor candidate address
	/// @param maxSlippage maximum rank change value for the candidate from the anchor candidate
	function withdrawAndClaim(
		address candidate,
		uint256 amount,
		address to,
		address anchor,
		uint256 maxSlippage
	) external;

	/// @dev candidate allocate reward for the voters
	/// @param candidate candidate address
	/// @param amount reward amount
	function onAllocate(address candidate, uint256 amount) external;

	/// @dev return ERC20 token address
	function token() external view returns(IERC20);

	/// @dev return `Rewarder` contract address
	function rewarder() external view returns(IRewarder);

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

	/// @dev return `MajorCandidates` contract address
	function majorCandidates() external view returns(IMajorCandidates);

	/// @dev return precision for shares
	function ACC_PRECISION() external view returns(uint256);

	/// @dev return votes for a specific candidate
	/// @param candidate candidate address
	/// @return votes for a specific candidate
	function voteSupply(address candidate) external view returns(uint256);

	/// @dev pending reward for a voter given a candidate
	/// @param candidate candidate address
	/// @param voter voter address
	/// @return pending pending reward
	function pendingReward(address candidate, address voter) external view returns (uint256 pending);

}