// SPDX-License-Identifier: GPL-3.0-only
pragma solidity ^0.8.19;

import {OwnableUpgradeable} from "@openzeppelin/contracts-upgradeable/access/OwnableUpgradeable.sol";
import {EnumerableSet} from "@openzeppelin/contracts/utils/structs/EnumerableSet.sol";

/// @title Bannable
/// @dev Contract module which allows an owner to ban or unban addresses.
/// Utilizes OpenZeppelin's OwnableUpgradeable for ownership management.
abstract contract Bannable is OwnableUpgradeable {
    using EnumerableSet for EnumerableSet.AddressSet;

    // ------------------------
    // STATE VARIABLES
    // ------------------------

    // @dev DEPRECATED: This storage slot is no longer used as of ERC7201 migration
    // @dev Kept for upgrade compatibility - do not use
    EnumerableSet.AddressSet private banList;

    // ------------------------
    // ERC7201 STORAGE
    // ------------------------

    /// @custom:storage-location erc7201:bannable.v1.banlist
    struct BanListStorage {
        EnumerableSet.AddressSet banList;
    }

    // keccak256(abi.encode(uint256(keccak256("bannable.v1.banlist")) - 1)) & ~bytes32(uint256(0xff))
    bytes32 private constant BAN_LIST_STORAGE_LOCATION = 0xc570069450541cbafa33b546085c421153a2f00786cad22bec4f4eb838578e00;

    function _getBanListStorage() private pure returns (BanListStorage storage $) {
        assembly {
            $.slot := BAN_LIST_STORAGE_LOCATION
        }
    }

    // ------------------------
    // EVENTS
    // ------------------------

    event Banned(address indexed account);
    event UnBanned(address indexed account);

    // ------------------------
    // ERRORS
    // ------------------------

    error AccountBanned();
    error AlreadyBanned();
    error NotBanned();

    // ------------------------
    // MODIFIERS
    // ------------------------

    /// @notice Modifier that reverts if the account is banned.
    /// @param account The address to check for a ban.
    modifier notBanned(address account) {
        if (isBanned(account)) {
            revert AccountBanned();
        }
        _;
    }

    // ------------------------
    // FUNCTIONS
    // ------------------------

    /// @notice Bans a specified account.
    /// @dev Can only be called by the contract owner.
    /// @param account The address to be banned.
    function ban(address account) external onlyOwner {
        BanListStorage storage $ = _getBanListStorage();
        bool success = $.banList.add(account);

        if (!success) {
            revert AlreadyBanned();
        }

        emit Banned(account);
    }

    /// @notice Unbans a specified account.
    /// @dev Can only be called by the contract owner.
    /// @param account The address to be unbanned.
    function unban(address account) external onlyOwner {
        BanListStorage storage $ = _getBanListStorage();
        bool success = $.banList.remove(account);

        if (!success) {
            revert NotBanned();
        }

        emit UnBanned(account);
    }

    /// @notice Retrieves the banned address at a specific index.
    /// @param index The index of the banned address in the list.
    /// @return The address of the banned account.
    function getBan(uint256 index) external view returns (address) {
        BanListStorage storage $ = _getBanListStorage();
        return $.banList.at(index);
    }

    /// @notice Lists all banned addresses.
    /// @return An array of banned addresses.
    function listBanned() external view returns (address[] memory) {
        BanListStorage storage $ = _getBanListStorage();
        return $.banList.values();
    }

    /// @notice Checks if an account is banned.
    /// @param account The address to check.
    /// @return True if the account is banned, false otherwise.
    function isBanned(address account) public view returns (bool) {
        BanListStorage storage $ = _getBanListStorage();
        return $.banList.contains(account);
    }

    /// @notice Bans a list of accounts.
    /// @param accounts The addresses to ban.
    /// @dev Can only be called by the contract owner.
    function batchBan(address[] calldata accounts) external onlyOwner {
        BanListStorage storage $ = _getBanListStorage();
        uint256 length = accounts.length;

        for (uint256 i; i < length;) {
            if (!$.banList.contains(accounts[i])) {
                $.banList.add(accounts[i]);
                emit Banned(accounts[i]);
            }

            unchecked {
                ++i;
            }
        }
    }
}