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//! An address to an actor is a way to send it a message. An address allows an actor to be sent any
//! kind of message that it can receive.
use std::error::Error;
use std::fmt::{self, Display, Formatter};
use std::future::Future;
use std::mem;
use std::pin::Pin;
use std::task::{Context, Poll};
use catty::Receiver;
use flume::r#async::SendFut as ChannelSendFuture;
use flume::Sender;
use futures_core::Stream;
use futures_util::{FutureExt, StreamExt};
use crate::envelope::{NonReturningEnvelope, ReturningEnvelope};
use crate::manager::AddressMessage;
use crate::refcount::{Either, RefCounter, Strong, Weak};
use crate::sink::AddressSink;
use crate::{Actor, Handler, KeepRunning, Message};
/// The future returned [`Address::send`](struct.Address.html#method.send).
/// It resolves to `Result<M::Result, Disconnected>`.
// This simply wraps the enum in order to hide the implementation details of the inner future
// while still leaving outer future nameable.
pub struct SendFuture<A: Actor, M: Message>(SendFutureInner<A, M>);
enum SendFutureInner<A: Actor, M: Message> {
Disconnected,
Sending(
ChannelSendFuture<'static, AddressMessage<A>>,
Receiver<M::Result>,
),
Receiving(Receiver<M::Result>),
}
impl<A: Actor, M: Message> Default for SendFutureInner<A, M> {
fn default() -> Self {
SendFutureInner::Disconnected
}
}
pub(crate) fn poll_rx<T>(rx: &mut Receiver<T>, ctx: &mut Context) -> Poll<Result<T, Disconnected>> {
rx.poll_unpin(ctx).map(|r| r.map_err(|_| Disconnected))
}
impl<A: Actor, M: Message> Future for SendFuture<A, M> {
type Output = Result<M::Result, Disconnected>;
fn poll(self: Pin<&mut Self>, ctx: &mut Context) -> Poll<Self::Output> {
let this = self.get_mut();
let (poll, new) = match mem::take(&mut this.0) {
old @ SendFutureInner::Disconnected => (Poll::Ready(Err(Disconnected)), old),
SendFutureInner::Sending(mut tx, mut rx) => {
if tx.poll_unpin(ctx).is_ready() {
(poll_rx(&mut rx, ctx), SendFutureInner::Receiving(rx))
} else {
(Poll::Pending, SendFutureInner::Sending(tx, rx))
}
}
SendFutureInner::Receiving(mut rx) => {
(poll_rx(&mut rx, ctx), SendFutureInner::Receiving(rx))
}
};
this.0 = new;
poll
}
}
/// The future returned from [`Address::do_send_async`](struct.Address.html#method.do_send_async).
/// It resolves to `Result<(), Disconnected>`.
pub struct DoSendFuture<A: Actor>(DoSendFutureInner<A>);
enum DoSendFutureInner<A: Actor> {
Disconnected,
Send(ChannelSendFuture<'static, AddressMessage<A>>),
}
impl<A: Actor> Future for DoSendFuture<A> {
type Output = Result<(), Disconnected>;
fn poll(self: Pin<&mut Self>, ctx: &mut Context) -> Poll<Self::Output> {
match &mut self.get_mut().0 {
DoSendFutureInner::Disconnected => Poll::Ready(Err(Disconnected)),
DoSendFutureInner::Send(tx) => {
tx.poll_unpin(ctx).map(|res| res.map_err(|_| Disconnected))
}
}
}
}
/// The actor is no longer running and disconnected from the sending address. For why this could
/// occur, see the [`Actor::stopping`](../trait.Actor.html#method.stopping) and
/// [`Actor::stopped`](../trait.Actor.html#method.stopped) methods.
#[derive(Clone, Eq, PartialEq, Debug)]
pub struct Disconnected;
impl Display for Disconnected {
fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
f.write_str("Actor address disconnected")
}
}
impl Error for Disconnected {}
/// An `Address` is a reference to an actor through which [`Message`s](../trait.Message.html) can be
/// sent. It can be cloned to create more addresses to the same actor.
/// By default (i.e without specifying the second type parameter, `Rc`, to be
/// [weak](../refcount/struct.Weak.html)), `Address`es are strong. Therefore, when all `Address`es
/// are dropped, the actor will be stopped. In other words, any existing `Address`es will inhibit
/// the dropping of an actor. If this is undesirable, then a [`WeakAddress`](type.WeakAddress.html)
/// should be used instead. An address is created by calling the
/// [`Actor::create`](../trait.Actor.html#method.create) or
/// [`Context::run`](../struct.Context.html#method.run) methods, or by cloning another `Address`.
pub struct Address<A: Actor, Rc: RefCounter = Strong> {
pub(crate) sender: Sender<AddressMessage<A>>,
pub(crate) ref_counter: Rc,
}
/// A `WeakAddress` is a reference to an actor through which [`Message`s](../trait.Message.html) can be
/// sent. It can be cloned. Unlike [`Address`](struct.Address.html), a `WeakAddress` will not inhibit
/// the dropping of an actor. It is created by the [`Address::downgrade`](struct.Address.html#method.downgrade)
/// method.
pub type WeakAddress<A> = Address<A, Weak>;
/// Functions which apply only to strong addresses (the default kind).
impl<A: Actor> Address<A, Strong> {
/// Create a weak address to the actor. Unlike with the strong variety of address (this kind),
/// an actor will not be prevented from being dropped if only weak sinks, channels, and
/// addresses exist.
pub fn downgrade(&self) -> WeakAddress<A> {
WeakAddress {
sender: self.sender.clone(),
ref_counter: self.ref_counter.downgrade(),
}
}
}
/// Functions which apply only to addresses which can either be strong or weak.
impl<A: Actor> Address<A, Either> {
/// Converts this address into a weak address.
pub fn downgrade(&self) -> WeakAddress<A> {
WeakAddress {
sender: self.sender.clone(),
ref_counter: self.ref_counter.clone().into_weak(),
}
}
}
/// Functions which apply to any kind of address, be they strong or weak.
impl<A: Actor, Rc: RefCounter> Address<A, Rc> {
/// Returns whether the actor referred to by this address is running and accepting messages.
///
/// ```rust
/// # use xtra::prelude::*;
/// # use xtra::spawn::Smol;
/// # use std::time::Duration;
/// # struct MyActor;
/// # impl Actor for MyActor {}
/// # use smol::Timer;
/// struct Shutdown;
///
/// impl Message for Shutdown {
/// type Result = ();
/// }
///
/// #[async_trait::async_trait]
/// impl Handler<Shutdown> for MyActor {
/// async fn handle(&mut self, _: Shutdown, ctx: &mut Context<Self>) {
/// ctx.stop();
/// }
/// }
///
/// smol::block_on(async {
/// let addr = MyActor.create(None).spawn(&mut Smol::Global);
/// assert!(addr.is_connected());
/// addr.send(Shutdown).await;
/// Timer::after(Duration::from_secs(1)).await; // Give it time to shut down
/// assert!(!addr.is_connected());
/// })
/// ```
pub fn is_connected(&self) -> bool {
self.ref_counter.is_connected()
}
/// Convert this address into a generic address which can be weak or strong.
pub fn as_either(&self) -> Address<A, Either> {
Address {
ref_counter: self.ref_counter.clone().into_either(),
sender: self.sender.clone(),
}
}
/// Send a [`Message`](../trait.Message.html) to the actor without waiting for a response.
/// If the actor's mailbox is full, it will block. If this returns `Err(Disconnected)`, then the
/// actor is stopped and not accepting messages. If this returns `Ok(())`, the will be delivered,
/// but may not be handled in the event that the actor stops itself (by calling
/// [`Context::stop`](../struct.Context.html#method.stop)) before it was handled.
pub fn do_send<M>(&self, message: M) -> Result<(), Disconnected>
where
M: Message,
A: Handler<M>,
{
if self.is_connected() {
// To read more about what an envelope is and why we use them, look under `envelope.rs`
let envelope = NonReturningEnvelope::<A, M>::new(message);
self.sender
.send(AddressMessage::Message(Box::new(envelope)))
.map_err(|_| Disconnected)
} else {
Err(Disconnected)
}
}
/// Send a [`Message`](../trait.Message.html) to the actor without waiting for a response.
/// If the actor's mailbox is full, it will asynchronously wait. If this returns
/// `Err(Disconnected)`, then the actor is stopped and not accepting messages. If this returns
/// `Ok(())`, the will be delivered, but may not be handled in the event that the actor stops
/// itself (by calling [`Context::stop`](../struct.Context.html#method.stop)) before it was handled.
pub fn do_send_async<M>(&self, message: M) -> DoSendFuture<A>
where
M: Message,
A: Handler<M>,
{
if self.is_connected() {
let envelope = NonReturningEnvelope::<A, M>::new(message);
let fut = self
.sender
.clone()
.into_send_async(AddressMessage::Message(Box::new(envelope)));
DoSendFuture(DoSendFutureInner::Send(fut))
} else {
DoSendFuture(DoSendFutureInner::Disconnected)
}
}
/// Send a [`Message`](../trait.Message.html) to the actor and asynchronously wait for a response. If this
/// returns `Err(Disconnected)`, then the actor is stopped and not accepting messages. Like most
/// futures, this must be polled to actually send the message.
pub fn send<M>(&self, message: M) -> SendFuture<A, M>
where
M: Message,
A: Handler<M>,
{
if self.is_connected() {
let (envelope, rx) = ReturningEnvelope::<A, M>::new(message);
let tx = self
.sender
.clone()
.into_send_async(AddressMessage::Message(Box::new(envelope)));
SendFuture(SendFutureInner::Sending(tx, rx))
} else {
SendFuture(SendFutureInner::Disconnected)
}
}
/// Attaches a stream to this actor such that all messages produced by it are forwarded to the
/// actor. This could, for instance, be used to forward messages from a socket to the actor
/// (after the messages have been appropriately `map`ped). This is a convenience method over
/// explicitly forwarding a stream to this address and checking when to stop forwarding.
///
/// Often, this should be spawned onto an executor to run in the background. **Do not await this
/// inside of an actor** - this will cause it to await forever and never receive any messages.
///
/// **Note:** if this stream's continuation should prevent the actor from being dropped, this
/// method should be called on [`Address`](struct.Address.html). Otherwise, it should be called
/// on [`WeakAddress`](type.WeakAddress.html).
pub async fn attach_stream<S, M, K>(self, stream: S)
where
K: Into<KeepRunning> + Send,
M: Message<Result = K>,
A: Handler<M>,
S: Stream<Item = M> + Send,
{
futures_util::pin_mut!(stream);
while let Some(m) = stream.next().await {
let res = self.send(m); // Bound to make it Sync
if !matches!(res.await.map(Into::into), Ok(KeepRunning::Yes)) {
break;
}
}
}
/// Converts this address into a [futures `Sink`](https://docs.rs/futures/0.3/futures/io/struct.Sink.html).
pub fn into_sink(self) -> AddressSink<A, Rc> {
AddressSink {
sink: self.sender.clone().into_sink(),
ref_counter: self.ref_counter.clone(),
}
}
}
// Required because #[derive] adds an A: Clone bound
impl<A: Actor, Rc: RefCounter> Clone for Address<A, Rc> {
fn clone(&self) -> Self {
Address {
sender: self.sender.clone(),
ref_counter: self.ref_counter.clone(),
}
}
}
// Drop impls cannot be specialised, so a little bit of fanagling is used in the RefCounter impl
impl<A: Actor, Rc: RefCounter> Drop for Address<A, Rc> {
fn drop(&mut self) {
// We should notify the ActorManager that there are no more strong Addresses and the actor
// should be stopped.
if self.ref_counter.is_last_strong() {
let _ = self.sender.send(AddressMessage::LastAddress);
}
}
}