Feature/events

[minecrawler]

@smallka This is the sim-ecs events example. It works on the release/0.5.0 branch!

import {buildWorld, createSystem, ReadEvents, Storage, WriteEvents} from "../src";

/// This example creates a new event, a system that triggers the event once per second,
/// and a system that prints a message whenever the event is received.

class MyEvent {
    constructor(
        public message: string
    ) {}
}

const EventTriggerSystem = createSystem({
    myEvents: WriteEvents(MyEvent),
    lastEvent: Storage({timestamp: 0}),
}).withRunFunction(async ({myEvents, lastEvent}) => {
    if (Date.now() - lastEvent.timestamp >= 1000) {
        await myEvents.publish(new MyEvent('My event just happened!'));
        lastEvent.timestamp = Date.now();
    }
}).build();

const EventListenerSystem = createSystem({
    myEvents: ReadEvents(MyEvent),
}).withRunFunction(({myEvents}) => {
    let myEvent;
    for (myEvent of myEvents.iter()) {
        console.log(myEvent.message);
    }
}).build();

buildWorld()
    .withDefaultScheduling(root => root
        /// Stages will run after one another, however the systems inside may run in any order and even in parallel
        .addNewStage(stage => stage.addSystem(EventTriggerSystem))
        /// So, if we want to receive the shutdown event guaranteed on the same step, we need to use a later stage
        .addNewStage(stage => stage.addSystem(EventListenerSystem))
    )
    .build()
    .run()
    .catch(console.error)
    .then(() => console.log('Finished.'));