use std::error::Error as StdError; use std::fmt; use std::sync::Arc; use crate::imap::mailbox_view::MailboxView; use crate::mail::user::User; #[derive(Debug)] pub enum Error { ForbiddenTransition, } impl fmt::Display for Error { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { write!(f, "Forbidden Transition") } } impl StdError for Error {} pub enum State { NotAuthenticated, Authenticated(Arc), Selected(Arc, MailboxView), // Examined is like Selected, but indicates that the mailbox is read-only Examined(Arc, MailboxView), Logout, } pub enum Transition { None, Authenticate(Arc), Examine(MailboxView), Select(MailboxView), Unselect, Logout, } // See RFC3501 section 3. // https://datatracker.ietf.org/doc/html/rfc3501#page-13 impl State { pub fn apply(self, tr: Transition) -> Result { match (self, tr) { (s, Transition::None) => Ok(s), (State::NotAuthenticated, Transition::Authenticate(u)) => Ok(State::Authenticated(u)), ( State::Authenticated(u) | State::Selected(u, _) | State::Examined(u, _), Transition::Select(m), ) => Ok(State::Selected(u, m)), ( State::Authenticated(u) | State::Selected(u, _) | State::Examined(u, _), Transition::Examine(m), ) => Ok(State::Examined(u, m)), (State::Selected(u, _) | State::Examined(u, _), Transition::Unselect) => { Ok(State::Authenticated(u)) } (_, Transition::Logout) => Ok(State::Logout), _ => Err(Error::ForbiddenTransition), } } }