event-engine 0.2.0

//! Events provide the mechansim by which plugins communicate with each other. Events correspond to
//! statically typed messages defined by the application.
use crate::errors::EngineError;
use zmq::Socket;
use std::error::Error;

/// An event type in the application. Event types have a name, which be used to
/// specify subscriptions by components (plugins) in applications.
/// They also have a filter, which is a byte array that appears at the beginning
/// of every message of the type. The filter must uniquely determine messages to b
/// of said type.
pub trait EventType {
    /// return the name of the event type
    // TODO -- can we return String and Vec[u8]?
    fn get_name(&self) -> String;

    /// compute the byte array filter for all messages of this event type.
    /// The filter must uniquely determine this event type.  The default
    /// implementation just returns the event name as bytes.
    fn get_filter(&self) -> Result<Vec<u8>, EngineError>;
}

/// Public API for defining events in an application.
/// Events are typed messages that can be sent over a ZMQ socket. Event are equipped
/// with functions to
pub trait Event {
    /// convert the event to a raw byte array
    fn to_bytes(&self) -> Result<Vec<u8>, EngineError>;

    fn from_bytes(bytes: Vec<u8>) -> Result<Self, Box<dyn Error>>
    where
        Self: Sized;

    /// send an event message to all subscribers
    fn send(&self, pub_socket: &mut Socket) -> Result<(), EngineError> {
        let data = self.to_bytes()?;
        pub_socket.send(data, 0)?;
        Ok(())
    }
}