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(&mut self, tr: Transition) -> Result<(), Error> { let new_state = match (&self, tr) { (_s, Transition::None) => return Ok(()), (State::NotAuthenticated, Transition::Authenticate(u)) => State::Authenticated(u), ( State::Authenticated(u) | State::Selected(u, _) | State::Examined(u, _), Transition::Select(m), ) => State::Selected(u.clone(), m), ( State::Authenticated(u) | State::Selected(u, _) | State::Examined(u, _), Transition::Examine(m), ) => State::Examined(u.clone(), m), (State::Selected(u, _) | State::Examined(u, _), Transition::Unselect) => { State::Authenticated(u.clone()) } (_, Transition::Logout) => State::Logout, _ => return Err(Error::ForbiddenTransition), }; *self = new_state; Ok(()) } }