from typing import Iterable

ROLE_ADMIN = "admin"
ROLE_OPERATOR = "operator"
ROLE_VIEWER = "viewer"

ALL_ROLES = (ROLE_ADMIN, ROLE_OPERATOR, ROLE_VIEWER)

ROLE_LABELS = {
    ROLE_ADMIN: "管理员",
    ROLE_OPERATOR: "运营",
    ROLE_VIEWER: "只读",
}


def is_admin(role: str) -> bool:
    return role == ROLE_ADMIN


def can_write(role: str) -> bool:
    return role in (ROLE_ADMIN, ROLE_OPERATOR)


def can_manage_users(role: str) -> bool:
    return role == ROLE_ADMIN


def ensure_role(role: str) -> str:
    if role not in ALL_ROLES:
        raise ValueError(f"无效角色: {role}")
    return role