reRPC
=====

`reRPC` is a simplified and flexible RPC system with unified model for client-to-server and server-to-server communication on top of HTTP and/or Socket.IO.

It provides an unified approach to define both a HTTP path and a Socket.IO event handlers as a single async function that can be invoked with a dedicated library.

## Status

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This library is production-ready.

Please refer to [releases/changelog](https://github.com/naderio/rerpc/releases) and [roadmap](https://github.com/naderio/rerpc/issues/1) for more information. 

## Description

`reRPC` enable you to do the following:
- define an async Node.js function (`lib.doSomething = async (payload) => { ... ; return result; };`)
- call the defined function from client by mean of:
  - client library (`result = await lib.doSomething(payload);`)
  - HTTP request (`POST /rerpc/doSomething` with payload as JSON in body)
  - Socket.IO event (`socketio.emit('/rerpc', 'doSomething', payload, (result) => { ... });`)

`reRPC` exposes defined functions by attaching itself to:
- `/rerpc` route on an [Express](https://expressjs.com/) app or route instance
- `/rerpc` event on a [Socket.IO](https://socket.io/) instance

## Goals

- enable writing a function once and call it with dedicated library, HTTP request and/or Socket.IO event
- simplify function invocation interface by mean of `async/await` and ES2015 `Proxy`
- stay simple:
  - do not create and manage transport connection, even in frontend
  - no middleware, authentication, ...
  - delegate customisation code to transport (Express and/or Socket.IO)
- stay flexible:
  - enable function to access transport layer
  - enable function context augmentation
  - enable [payload processing customisation](doc/payload-processing.md)
  - enable [error handling customisation](doc/error-handling.md)
  - enable [prefix customisation](doc/prefix.md)

## Requirements

`reRPC` makes use of a number of ES2015+ features, most notably `async/await` and `Proxy`. Therefore:

- Node v8+
- Transpiler for browser code

## Usage

Refer to [`doc` folder](./doc) for more documentation.

### Server

```javascript
const express = require('express');
const app = express();
app.use(express.json());
const http = require('http').Server(app);
app.io = require('socket.io')(http);
http.listen(5000);

// initiate
const rerpc = require('rerpc')({});

// define function
async function greet({ name }) {
  return `Hello ${name}!`;
}

// register function
rerpc.register({ greet });

// attach to Express app our route, creates '/rerpc' route
rerpc.attachToExpress(app);

// attach to Socket.IO instance, creates '/rerpc' event
app.io.on('connect', soc => rerpc.attachToSocketIO(soc));
```

### Client

#### Using dedicated library

```javascript
const rerpc = require('rerpc/client')({
  transport: 'http',
  transportHandler: 'http://localhost:5000',
});

// or

const socketio = require('socket.io-client')('http://localhost:5000/');

const rerpc = require('rerpc/client')({
  transport: 'socket.io',
  transportHandler: socketio,
});

// then

try {
  const result = await rerpc.fn.greet({ name: 'World' });
  console.log(result); // => "Hello World!"
} catch(error) {
  console.error(error);
}
```

#### Using `CURL`

```bash
curl -X POST 'http://localhost:5000/rerpc/greet' -H 'Content-Type: application/json' -d '{"name": "World"}'
# => { "$result": "Hello World!" } OR {" $error": { ... } }
```

#### Using `fetch`

```javascript
const response = await fetch('http://localhost:5000/rerpc/greet', {
  method: 'post',
  headers: new Headers({ 'Content-Type': 'application/json' }),
  body: JSON.stringify({ name: 'World' }),
});

const result = await response.json();

console.log(result); // => { "$result": "Hello World!" } OR { "$error:" { ... } }
```

#### Using Socket.IO

```javascript
const socketio = require('socket.io-client')('http://localhost:5000/');

socketio.emit('/rerpc', 'greet', { name: 'World' }, (result => {
  console.log(result); // => { "$result": "Hello World!" } OR { "$error:" { ... } }
});
```

## Code Samples

Refer to [`samples` folder](./samples) for more examples.