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pub use bus::Bus;
use std::{error::Error, mem};
use std::{fmt::Debug, sync::mpsc::SendError};
pub use subscriber::Subscriber;
mod bus;
mod subscriber;
pub trait Message
where
Self: Clone,
{
type Discriminant: Discriminant<Self>;
fn discriminant(&self) -> Self::Discriminant;
}
pub trait Discriminant<M>
where
Self: PartialEq + Debug,
{
}
impl<T> Discriminant<T> for mem::Discriminant<T> {}
pub trait Subscription
where
Self: PartialEq,
{
type Event: Message;
fn subscribed_to(&self, message: &Self::Event) -> bool;
fn discriminant_set(&self) -> &[<Self::Event as Message>::Discriminant];
fn send_event(&self, message: Self::Event) -> Result<(), SendError<Self::Event>>;
}
pub trait TerminationCondition<M: Message> {
fn terminates(&mut self, message: &M) -> bool;
}
impl<M: Message, T: TerminationCondition<M>> TerminationCondition<M> for Option<T> {
fn terminates(&mut self, message: &M) -> bool {
if let Some(c) = self {
c.terminates(message)
} else {
false
}
}
}
impl<M: Message> TerminationCondition<M> for () {
fn terminates(&mut self, _message: &M) -> bool {
false
}
}
impl<M: Message, F: FnMut(&M) -> bool> TerminationCondition<M> for F {
fn terminates(&mut self, message: &M) -> bool {
self(message)
}
}
pub trait EventDistributor {
type Event: Message;
type Error: Error;
type EventSender;
type SubscriptionSender;
type TerminationCondition: TerminationCondition<Self::Event>;
fn serve_events(&mut self) -> Result<(), Self::Error>;
fn get_event_sink(&self) -> Self::EventSender;
fn get_subscrition_sink(&self) -> Self::SubscriptionSender;
}
mod foo {
use crate::{Discriminant, Message};
#[derive(Clone)]
enum TestMessage {
A,
B,
}
impl Message for TestMessage {
type Discriminant = std::mem::Discriminant<Self>;
fn discriminant(&self) -> Self::Discriminant {
std::mem::discriminant(self)
}
}
impl Discriminant<String> for [char; 5] {}
impl Message for String {
type Discriminant = [char; 5];
fn discriminant(&self) -> Self::Discriminant {
use std::convert::TryInto;
self.chars().take(5).collect::<Vec<_>>().try_into().unwrap()
}
}
}
#[cfg(test)]
mod tests {
use super::*;
use std::{mem::discriminant, sync::mpsc, thread};
type TestBus = Bus<TestMessage, Subscriber<TestMessage>, fn(&TestMessage) -> bool>;
fn terminator(msg: &TestMessage) -> bool {
matches!(msg, TestMessage::Terminate)
}
#[derive(Clone, PartialEq, Debug)]
enum TestMessage {
FooEvent,
Terminate,
}
impl Message for TestMessage {
type Discriminant = mem::Discriminant<Self>;
fn discriminant(&self) -> Self::Discriminant {
discriminant(self)
}
}
#[test]
fn can_accept_subscribers() {
let mut bus: TestBus = Bus::new(terminator);
assert!(bus.subscribers.is_empty());
let subscribe_sink = bus.get_subscrition_sink();
let (tx, _) = mpsc::channel();
let subscriber = Subscriber::<TestMessage> {
sender: tx,
discriminant_set: vec![],
};
let etx = bus.get_event_sink();
etx.send(TestMessage::Terminate).unwrap();
subscribe_sink.send(subscriber).unwrap();
bus.serve_events().unwrap();
assert_eq!(bus.subscribers.len(), 1);
}
#[test]
fn subscriber_recieves_events() {
let mut bus: TestBus = Bus::new(terminator);
let subscribe_sink = bus.get_subscrition_sink();
let (tx, rx) = mpsc::channel();
let subscriber = Subscriber::<TestMessage> {
sender: tx,
discriminant_set: vec![TestMessage::FooEvent.discriminant()],
};
let etx = bus.get_event_sink();
etx.send(TestMessage::FooEvent).unwrap();
subscribe_sink.send(subscriber).unwrap();
thread::spawn(move || bus.serve_events().unwrap());
assert_eq!(rx.recv(), Ok(TestMessage::FooEvent));
etx.send(TestMessage::Terminate).unwrap();
}
impl TerminationCondition<TestMessage> for TestMessage {
fn terminates(&mut self, message: &TestMessage) -> bool {
self == message
}
}
#[test]
fn bus_terminated_by_message() {
let mut bus: Bus<TestMessage, Subscriber<TestMessage>, TestMessage> =
Bus::new(TestMessage::Terminate);
let subscribe_sink = bus.get_subscrition_sink();
let (tx, rx) = mpsc::channel();
let subscriber = Subscriber::<TestMessage> {
sender: tx,
discriminant_set: vec![TestMessage::FooEvent.discriminant()],
};
let etx = bus.get_event_sink();
etx.send(TestMessage::FooEvent).unwrap();
subscribe_sink.send(subscriber).unwrap();
thread::spawn(move || bus.serve_events().unwrap());
assert_eq!(rx.recv(), Ok(TestMessage::FooEvent));
etx.send(TestMessage::Terminate).unwrap();
}
}