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//! Module dedicated to email envelope flags synchronization.
//!
//! This module contains a single function [sync] that synchronizes
//! multiple email envelope flags sources.
pub mod config;
use std::collections::HashSet;
use super::{Flag, Flags};
/// The email envelope flag synchronizer.
///
/// Folds multiple source of flags into one synchronized flags.
pub fn sync(
local_cache: Option<&Flags>,
local: Option<&Flags>,
remote_cache: Option<&Flags>,
remote: Option<&Flags>,
) -> Flags {
let mut synchronized_flags: HashSet<Flag> = HashSet::default();
let mut all_flags: HashSet<Flag> = HashSet::default();
all_flags.extend(local_cache.map(|e| e.0.clone()).unwrap_or_default());
all_flags.extend(local.map(|e| e.0.clone()).unwrap_or_default());
all_flags.extend(remote_cache.map(|e| e.0.clone()).unwrap_or_default());
all_flags.extend(remote.map(|e| e.0.clone()).unwrap_or_default());
for flag in all_flags {
match (
local_cache.and_then(|e| e.get(&flag)),
local.and_then(|e| e.get(&flag)),
remote_cache.and_then(|e| e.get(&flag)),
remote.and_then(|e| e.get(&flag)),
) {
// The flag exists nowhere, which cannot happen since the
// flags hashset is built from envelopes flags.
(None, None, None, None) => (),
// The flag only exists in remote side, which means a new
// flag has been added.
(None, None, None, Some(_)) => {
synchronized_flags.insert(flag.clone());
}
// The flag only exists in remote cache, which means an
// outdated flag needs to be removed.
(None, None, Some(_), None) => {
synchronized_flags.remove(&flag);
}
// The flag exists in remote side but not in local side,
// which means there is a conflict. Since we cannot
// determine which side (local removed or remote added) is
// the most up-to-date, it is safer to consider the remote
// added side up-to-date (or local removed in case of
// [`Flag::Deleted`]) in order not to lose data.
//
// TODO: make this behaviour customizable.
(None, None, Some(_), Some(_)) if flag == Flag::Deleted => {
synchronized_flags.remove(&flag);
}
(None, None, Some(_), Some(_)) => {
synchronized_flags.insert(flag.clone());
}
// The flag only exists in local side, which means a new
// flag has been added.
(None, Some(_), None, None) => {
synchronized_flags.insert(flag.clone());
}
// The flag exists in local and remote sides, which means
// a new (same) flag has been added both sides at the same
// time.
(None, Some(_), None, Some(_)) => {
synchronized_flags.insert(flag.clone());
}
// The flag exists in local side and remote cache side,
// which means a new (same) flag has been added local side
// but removed remote side. Since we cannot determine
// which side (local added or remote removed) is the most
// up-to-date, it is safer to consider the local added
// side up-to-date (or remote removed in case of
// [`Flag::Deleted`]) in order not to lose data.
//
// TODO: make this behaviour customizable.
(None, Some(_), Some(_), None) if flag == Flag::Deleted => {
synchronized_flags.remove(&flag);
}
(None, Some(_), Some(_), None) => {
synchronized_flags.insert(flag.clone());
}
// The flag exists everywhere except in local cache, which
// means the local cache misses a flag.
(None, Some(_), Some(_), Some(_)) => {
synchronized_flags.insert(flag.clone());
}
// The flag only exists in local cache side, which means
// the local cache has an outdated flag.
(Some(_), None, None, None) => {
synchronized_flags.remove(&flag);
}
// The flag exists in local cache side and remote side,
// which means a new (same) flag has been removed local
// cache side but added remote side. Since we cannot
// determine which side (local removed or remote added) is
// the most up-to-date, it is safer to consider the remote
// added side up-to-date (or local removed in case of
// [`Flag::Deleted`]) in order not to lose data.
//
// TODO: make this behaviour customizable.
(Some(_), None, None, Some(_)) if flag == Flag::Deleted => {
synchronized_flags.remove(&flag);
}
(Some(_), None, None, Some(_)) => {
synchronized_flags.insert(flag.clone());
}
// The flag exists in both caches, which means a old flag
// needs to be removed everywhere.
(Some(_), None, Some(_), None) => {
synchronized_flags.remove(&flag);
}
// The flag exists everywhere except in local side, which
// means a flag has been removed local side and needs to
// be removed everywhere else.
(Some(_), None, Some(_), Some(_)) => {
synchronized_flags.remove(&flag);
}
// The flag exists in the local sides but not in remote
// sides, which means there is a conflict. Since we cannot
// determine which side is the most up-to-date, it is
// safer to consider the local side side up-to-date (or
// remote side in case of [`Flag::Deleted`]) in order not
// to lose data.
//
// TODO: make this behaviour customizable.
(Some(_), Some(_), None, None) if flag == Flag::Deleted => {
synchronized_flags.remove(&flag);
}
(Some(_), Some(_), None, None) => {
synchronized_flags.insert(flag.clone());
}
// The flag exists everywhere except in remote cache side,
// which means the remote cache misses a flag.
(Some(_), Some(_), None, Some(_)) => {
synchronized_flags.insert(flag.clone());
}
// The flag exists everywhere except in remote side, which
// means a flag has been removed remote side and needs to
// be removed everywhere else.
(Some(_), Some(_), Some(_), None) => {
synchronized_flags.remove(&flag);
}
// The flag exists everywhere, which means the flag needs
// to be added.
(Some(_), Some(_), Some(_), Some(_)) => {
synchronized_flags.insert(flag.clone());
}
}
}
Flags::from_iter(synchronized_flags)
}
#[cfg(test)]
mod tests {
use crate::flag::{Flag, Flags};
#[test]
fn sync() {
assert_eq!(super::sync(None, None, None, None), Flags::default());
assert_eq!(
super::sync(None, None, None, Some(&Flags::from_iter([Flag::Seen]))),
Flags::from_iter([Flag::Seen]),
);
assert_eq!(
super::sync(
Some(&Flags::default()),
Some(&Flags::default()),
Some(&Flags::default()),
Some(&Flags::from_iter([Flag::Seen])),
),
Flags::from_iter([Flag::Seen]),
);
assert_eq!(
super::sync(
Some(&Flags::default()),
Some(&Flags::default()),
Some(&Flags::from_iter([Flag::Seen])),
Some(&Flags::default()),
),
Flags::default()
);
assert_eq!(
super::sync(
Some(&Flags::default()),
Some(&Flags::default()),
Some(&Flags::from_iter([Flag::Seen])),
Some(&Flags::from_iter([Flag::Seen])),
),
Flags::from_iter([Flag::Seen]),
);
assert_eq!(
super::sync(
Some(&Flags::default()),
Some(&Flags::from_iter([Flag::Seen])),
Some(&Flags::default()),
Some(&Flags::default()),
),
Flags::from_iter([Flag::Seen]),
);
assert_eq!(
super::sync(
Some(&Flags::default()),
Some(&Flags::from_iter([Flag::Seen])),
Some(&Flags::default()),
Some(&Flags::from_iter([Flag::Seen])),
),
Flags::from_iter([Flag::Seen]),
);
assert_eq!(
super::sync(
Some(&Flags::default()),
Some(&Flags::from_iter([Flag::Seen])),
Some(&Flags::from_iter([Flag::Seen])),
Some(&Flags::default()),
),
Flags::from_iter([Flag::Seen]),
);
assert_eq!(
super::sync(
Some(&Flags::default()),
Some(&Flags::from_iter([Flag::Seen])),
Some(&Flags::from_iter([Flag::Seen])),
Some(&Flags::from_iter([Flag::Seen])),
),
Flags::from_iter([Flag::Seen]),
);
assert_eq!(
super::sync(
Some(&Flags::from_iter([Flag::Seen])),
Some(&Flags::default()),
Some(&Flags::default()),
Some(&Flags::default()),
),
Flags::default()
);
assert_eq!(
super::sync(
Some(&Flags::from_iter([Flag::Seen])),
Some(&Flags::default()),
Some(&Flags::default()),
Some(&Flags::from_iter([Flag::Seen])),
),
Flags::from_iter([Flag::Seen]),
);
assert_eq!(
super::sync(
Some(&Flags::from_iter([Flag::Seen])),
Some(&Flags::default()),
Some(&Flags::from_iter([Flag::Seen])),
Some(&Flags::default()),
),
Flags::default(),
);
assert_eq!(
super::sync(
Some(&Flags::from_iter([Flag::Seen])),
Some(&Flags::default()),
Some(&Flags::from_iter([Flag::Seen])),
Some(&Flags::from_iter([Flag::Seen])),
),
Flags::default(),
);
assert_eq!(
super::sync(
Some(&Flags::from_iter([Flag::Seen])),
Some(&Flags::from_iter([Flag::Seen])),
Some(&Flags::default()),
Some(&Flags::default()),
),
Flags::from_iter([Flag::Seen]),
);
assert_eq!(
super::sync(
Some(&Flags::from_iter([Flag::Seen])),
Some(&Flags::from_iter([Flag::Seen])),
Some(&Flags::default()),
Some(&Flags::from_iter([Flag::Seen])),
),
Flags::from_iter([Flag::Seen]),
);
assert_eq!(
super::sync(
Some(&Flags::from_iter([Flag::Seen])),
Some(&Flags::from_iter([Flag::Seen])),
Some(&Flags::from_iter([Flag::Seen])),
Some(&Flags::default()),
),
Flags::default(),
);
assert_eq!(
super::sync(
Some(&Flags::from_iter([Flag::Seen, Flag::Flagged])),
Some(&Flags::from_iter([Flag::Seen, Flag::Flagged])),
Some(&Flags::from_iter([Flag::Seen, Flag::Flagged])),
Some(&Flags::from_iter([Flag::Seen, Flag::Flagged])),
),
Flags::from_iter([Flag::Seen, Flag::Flagged]),
);
}
}