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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<User>),
Selected(Arc<User>, MailboxView),
// Examined is like Selected, but indicates that the mailbox is read-only
Examined(Arc<User>, MailboxView),
Logout,
}
pub enum Transition {
None,
Authenticate(Arc<User>),
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(())
}
}
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