Add tags() method that returns Option<Arc<RwLock<BTreeMap<u64, String>>>>.
The BTreeMap holds available tags in a mail backend and uses the tag's
hash as key.
The method returns an Option because not all backends may support
tagging.
Change folders() signature:
- fn folders(&self) -> FnvHashMap<FolderHash, Folder>;
+ fn folders(&self) -> Result<FnvHashMap<FolderHash, Folder>>;
Imap may not be online, therefore we need the ability to return an
error.
Make startup methods return Results so that the main binary can exit
cleanly instead of using std::process::exit from arbitrary positions,
which exits the process immediately and doesn't run destructors.
The operation() method on the MailBackend trait returns a trait object
that can read or modify an Envelope directly from the backend. This is
used to get eg the envelope's text, or set flags. It has two arguments,
envelope hash and folder hash.
Only the Maildir backend needed the latter argument, and it can be replaced with a dictionary to match envelope hashes to folder hashes within the Maildir backend.
Add a boolean field to accounts that states if the account can be
accessed. Local backends (Maildir/mbox) return true every time, but
remote backends (IMAP) may not. Accounts start as offline and then get
initialised when their status goes to online. Right now if an IMAP
account startup but later get offline, there are crashes. With this
change the account can be switched back to offline when that happens.
