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//! # Events specification.
use anyhow::Result;
use tokio::sync::Mutex;
pub(crate) mod chatlist_events;
mod payload;
pub use self::payload::EventType;
/// Event channel.
#[derive(Debug, Clone)]
pub struct Events {
/// Unused receiver to prevent the channel from closing.
_receiver: async_broadcast::InactiveReceiver<Event>,
/// Sender side of the event channel.
sender: async_broadcast::Sender<Event>,
}
impl Default for Events {
fn default() -> Self {
Self::new()
}
}
impl Events {
/// Creates a new event channel.
pub fn new() -> Self {
let (mut sender, _receiver) = async_broadcast::broadcast(1_000);
// We only keep this receiver around
// to prevent the channel from closing.
// Deactivating it to prevent it from consuming memory
// holding events that are not going to be received.
let _receiver = _receiver.deactivate();
// Remove oldest event on overflow.
sender.set_overflow(true);
Self { _receiver, sender }
}
/// Emits an event into event channel.
///
/// If the channel is full, deletes the oldest event first.
pub fn emit(&self, event: Event) {
self.sender.try_broadcast(event).ok();
}
/// Creates an event emitter.
pub fn get_emitter(&self) -> EventEmitter {
EventEmitter(Mutex::new(self.sender.new_receiver()))
}
}
/// A receiver of events from a [`Context`].
///
/// See [`Context::get_event_emitter`] to create an instance. If multiple instances are
/// created events emitted by the [`Context`] will only be delivered to one of the
/// `EventEmitter`s.
///
/// [`Context`]: crate::context::Context
/// [`Context::get_event_emitter`]: crate::context::Context::get_event_emitter
#[derive(Debug)]
pub struct EventEmitter(Mutex<async_broadcast::Receiver<Event>>);
impl EventEmitter {
/// Async recv of an event. Return `None` if the `Sender` has been dropped.
///
/// [`try_recv`]: Self::try_recv
pub async fn recv(&self) -> Option<Event> {
let mut lock = self.0.lock().await;
lock.recv().await.ok()
}
/// Tries to receive an event without blocking.
///
/// Returns error if no events are available for reception
/// or if receiver mutex is locked by a concurrent call to [`recv`]
/// or `try_recv`.
///
/// [`recv`]: Self::recv
pub fn try_recv(&self) -> Result<Event> {
// Using `try_lock` instead of `lock`
// to avoid blocking
// in case there is a concurrent call to `recv`.
let mut lock = self.0.try_lock()?;
let event = lock.try_recv()?;
Ok(event)
}
}
/// The event emitted by a [`Context`] from an [`EventEmitter`].
///
/// Events are documented on the C/FFI API in `deltachat.h` as `DC_EVENT_*` constants. The
/// context emits them in relation to various operations happening, a lot of these are again
/// documented in `deltachat.h`.
///
/// [`Context`]: crate::context::Context
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct Event {
/// The ID of the [`Context`] which emitted this event.
///
/// This allows using multiple [`Context`]s in a single process as they are identified
/// by this ID.
///
/// [`Context`]: crate::context::Context
pub id: u32,
/// The event payload.
///
/// These are documented in `deltachat.h` as the `DC_EVENT_*` constants.
pub typ: EventType,
}