// SPDX-License-Identifier: UNLICENSED

pragma solidity ^0.8.0;

/**
 * @title SOMA ERC20 History Upgradeable Contract.
 * @author SOMA.finance
 * @notice An ERC20 extension to keep a history of each account's voting balance.
 */
interface IERC20HistoryUpgradeable {
    /**
     * @notice Emitted when a token transfer or delegate change results in changes to a delegate's number of votes.
     * @param account The account that had a change in balance.
     * @param previousBalance The previous balance of `account`.
     * @param newBalance The new balance of `account`.
     */
    event BalanceChanged(address indexed account, uint256 previousBalance, uint256 newBalance);

    /**
     * @notice Returns the balance for `account` at the end of `blockNumber`.
     * @param account The account to return the past balance of.
     * @param blockNumber The block number to return ``account``'s balance at.
     * @custom:requirement `blockNumber` must have been already mined.
     * @return The balance of `account` at `blockNumber`.
     */
    function getPastBalance(address account, uint256 blockNumber) external view returns (uint256);

    /**
     * @notice Returns the total supply of votes available at the end of a past block (`blockNumber`).
     * @dev This value is the sum of all available votes, which is not necessarily the sum of all delegated votes.
     * Votes that have not been delegated are still part of total supply, even though they would not participate in a
     * vote.
     * @param blockNumber The block number to return the total supply at.
     * @custom:requirement `blockNumber` must have been already mined.
     * @return The total supply at `blockNumber`.
     */
    function getPastTotalSupply(uint256 blockNumber) external view returns (uint256);
}