Bi-directional reactive protocol

Real-time, type-safe data flow without the hassle.

Operations

• Method
  Call a remote function (RPC)
• Event
  Listen to remote events
• Observable
  Subscribe to remote observable values

In the following documentation, the code that provide implementations is called server and the code that consumes the implementation remotely is called client

Method

Allows client to invoke a function implemented in the server side, and optionally gets a value back.

To define and implement remotely-callable methods:

1. invoke the irpc constructor with a generic type parameter {local: {methods: MyMethods}}
2. provide implementations in the methods field in the constructor

type MyMethods = { add(a:number, b:number) => number }
const server = init<{ local: { methods: MyMethods } }>(
  transport,
  { methods: {add: (a, b) => a + b} }
);

To consume the remote methods:

1. invoke the irpc constructor with a generic type parameter {remote: {methods: MyMethods}}
2. invoke the methods via instance.remote.methods

const client = init<{ remote: { methods: MyMethods } }>(
  transport,
  {}
);
const sum = await client.remote.methods.add(2, 3); // sum = 5

Event

Allow clients to subscribe to events emitted from the server side.

To define and implement remotely-listenable events:

1. invoke the irpc constructor with a generic type parameter {local: {events: MyEvents}}
2. emit the event via instance.local.events

type MyEvents = { tick: number };
const server = init<{ local: { events: MyEvents } }>(
  transport, 
  {}
);

// emit the event every second
setInterval(() => server.local.events.tick(Date.now()), 1000);

To listen to the remote events:

1. invoke the irpc constructor with a generic type parameter {remote: {events: MyEvents}}
2. invoke the Events via instance.remote.events

const client = init<{ remote: { events: MyEvents } }>(
  transport, 
  {}
);
const unsubscribe = client.remote.events.tick((time) => console.log(time));

// unsubscribe later
unsubscribe();

Observable

Observable is very similar to Event, but it is lazy. The observable logic is only initiated on the first subscription and will not re-initiate for subsequent subscriptions. Also the teardown logic will only be run when the last subscriber unsubscribes.

To define and implement remotely-observable values:

1. invoke the irpc constructor with a generic type parameter {local: {observables: MyObservables}}
2. provide implementations in the observables field in the constructor

type MyObservables = { foo: number };
const server = init<{ local: { observables: MyObservables } }>(
  transport, {
  observables: (callback) => {
    const timer = setInterval(() => callback(new Date()), 50);
    return () => clearInterval(timer);
  },
});

To subscribe to the remote observables:

1. invoke the irpc constructor with a generic type parameter {remote: {observables: MyObservables}}
2. invoke the Observables via instance.remote.observables

const client = init<{ remote: { observables: MyObservables } }>(
  transport, 
  {}
);
const unsubscribe = client.remote.observables.foo((val) => console.log(val));

// unsubscribe later
unsubscribe();

Untyped Access

Access the API in a untyped-manner via the DYNAMIC symbol.

const sum = await client.remote.methods[DYNAMIC]('add', 2, 3); // sum = 5

Transport

Transport is the implementation that actually delivers the data. The implementation dictates what and how data types are "transmitted" to the remote side.

• LocalBridgeTransport
  In-memory tranport, mainly for testing. Since all data lives in the same program memory, all data types are supported.
• PostMessageTransport
  Built on top of browser's postMessage API, mainly for communication between iframes or workers. Check the docs of postMessage to find out what data types are supported. The transfer option is also exposed so one can decide to transfer the data instead of cloning it.
• WebSocketTransport: (coming soon)

TODO

• Validation of payload data type (command args and return values, etc)
• Allow parameters when subscribing to an observable
• Properly teardown/reset stuff when disconnect