openzeppelin-contracts/contracts/access/extensions/AccessControlEnumerable.sol

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.4.0) (access/extensions/AccessControlEnumerable.sol)

pragma solidity ^0.8.20;

import {IAccessControlEnumerable} from "./IAccessControlEnumerable.sol";
import {AccessControl} from "../AccessControl.sol";
import {EnumerableSet} from "../../utils/structs/EnumerableSet.sol";
import {IERC165} from "../../utils/introspection/ERC165.sol";

/**
 * @dev Extension of {AccessControl} that allows enumerating the members of each role.
 */
abstract contract AccessControlEnumerable is IAccessControlEnumerable, AccessControl {
    using EnumerableSet for EnumerableSet.AddressSet;

    mapping(bytes32 role => EnumerableSet.AddressSet) private _roleMembers;

    /// @inheritdoc IERC165
    function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
        return interfaceId == type(IAccessControlEnumerable).interfaceId || super.supportsInterface(interfaceId);
    }

    /**
     * @dev Returns one of the accounts that have `role`. `index` must be a
     * value between 0 and {getRoleMemberCount}, non-inclusive.
     *
     * Role bearers are not sorted in any particular way, and their ordering may
     * change at any point.
     *
     * WARNING: When using {getRoleMember} and {getRoleMemberCount}, make sure
     * you perform all queries on the same block. See the following
     * https://forum.openzeppelin.com/t/iterating-over-elements-on-enumerableset-in-openzeppelin-contracts/2296[forum post]
     * for more information.
     */
    function getRoleMember(bytes32 role, uint256 index) public view virtual returns (address) {
        return _roleMembers[role].at(index);
    }

    /**
     * @dev Returns the number of accounts that have `role`. Can be used
     * together with {getRoleMember} to enumerate all bearers of a role.
     */
    function getRoleMemberCount(bytes32 role) public view virtual returns (uint256) {
        return _roleMembers[role].length();
    }

    /**
     * @dev Return all accounts that have `role`
     *
     * WARNING: This operation will copy the entire storage to memory, which can be quite expensive. This is designed
     * to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that
     * this function has an unbounded cost, and using it as part of a state-changing function may render the function
     * uncallable if the set grows to a point where copying to memory consumes too much gas to fit in a block.
     */
    function getRoleMembers(bytes32 role) public view virtual returns (address[] memory) {
        return _roleMembers[role].values();
    }

    /**
     * @dev Overload {AccessControl-_grantRole} to track enumerable memberships
     */
    function _grantRole(bytes32 role, address account) internal virtual override returns (bool) {
        bool granted = super._grantRole(role, account);
        if (granted) {
            _roleMembers[role].add(account);
        }
        return granted;
    }

    /**
     * @dev Overload {AccessControl-_revokeRole} to track enumerable memberships
     */
    function _revokeRole(bytes32 role, address account) internal virtual override returns (bool) {
        bool revoked = super._revokeRole(role, account);
        if (revoked) {
            _roleMembers[role].remove(account);
        }
        return revoked;
    }
}