# Overview [![Build Status](https://www.bottleneck.me/api/badges/frontwork-vendor/rpclibrary/status.svg)](https://www.bottleneck.me/frontwork-vendor/rpclibrary)
rpclibrary is a websocket on steroids!

# How to install
```
npm i rpclibrary
```

# Quickstart
```typescript
import {Backend, Frontend} from 'rpclibrary' 

const echo = (x) => x

const server = new Backend.RPCServer(port, [{
    name: 'HelloWorldRPCGroup',
    exportRPCs: ()  => [
        echo, //named function variable
        function echof(x){ return x }, //named function
        {
            name: 'echoExplicit', //describing object
            call: async (x) => x
        }
    ]
}])

const client = new Frontend.RPCSocket(port, host)

client.connect().then(async () => {
    const r0 = await client['HelloWorldRPCGroup'].echo('Hello')
    const r1 = await client['HelloWorldRPCGroup'].echof('World')
    const r2 = await client['HelloWorldRPCGroup'].echoExplicit('RPC!')

    console.log(r0,r1,r2) //Hello World RPC!
})

```

# Using callbacks

rpclibrary offers a special type of call that can be used with callbacks. The callback **has to be the last argument** and **may be the only passed function**. 

In order to function, some metadata has to be included in the return value of hooks. On success, the function is expected to return a `{ result: 'Success', uuid: string }` (Types.SubscriptionResponse) or in case of errors a `{ result: 'Error' }`(Types.ErrorResponse).

The uuid, as the name implies, is used to uniquely identify the callback for a given invocation and also dictates the name given to the client-side RPC. Unless you got a preferred way of generating these (e.g. using some kind of unique information important to your task) we recommend [uuid](https://www.npmjs.com/package/uuid) for this purpose. 

You should unhook the client socket once you're done with it as not to cause security or control flow issues.

```typescript
import {Backend, Frontend, Utils} from 'rpclibrary'

const callbacks:Map<string, Function> = new Map()

const server = new Backend.RPCServer(port, [{
    name: 'HelloWorldRPCGroup',
    exportRPCs: ()  => [
        function  triggerCallbacks(...messages){ callbacks.forEach(cb => cb.apply({}, messages)) },
        {
            name: 'subscribe',
            hook: async (callback) => {
                const randStr = 'generate_a_random_string_here'
                callbacks.set(randStr, callback); 
                return { result: 'Success', uuid: randStr} 
            }
        },{
            name: 'unsubscribe',
            call: async (uuid) => { callbacks.delete(uuid) }
        }
    ]
}])

const client = new Frontend.RPCSocket(port, host)
client.connect().then(async () => {
    const res = await client['HelloWorldRPCGroup'].subscribe(async (...args:any) => {
        console.log.apply(console, args)

        /* close the callbacks once you're done */
        await client['HelloWorldRPCGroup'].unsubscribe(res.uuid)
        client.unhook(res.uuid)
    })

    await client['HelloWorldRPCGroup'].triggerCallbacks("Hello", "World", "Callbacks")
})
```

If you need to include further response data into your `SubscriptionResponse` you can extend it using the server's first generic parameter `SubResType`

```typescript
new RPCServer<{extension: string}>(port, {
    name: 'MyRPCGroup',
    exportRPCs: ()  => [{
        name: 'subscribe',
        hook: async (callback) => {
            return {
                result: 'Success',
                uuid: 'very_random_string',
                extension: 'your_data_here' //tsc will demand this field
            }
        }
    }]
})

```

#Experimental typing support
It is possible to declare pseudo-interfaces for servers and clients by using server's second generic parameter.
This feature is currently still in development and considered **unstable and untested**. Use with caution.

```typescript
type MyInterface = { 
    Group1: { 
        triggerCallbacks: (...args:any[]) => Promise<void>,
        subscribe: (param:string, callback:Function) => Promise<SubscriptionResponse<{a: string}>>,
        unsubscribe: (uuid:string) => Promise<void>
    },
    Group2: {
        echo: (x:string) => Promise<string>
    }
}
```
Create a client using
```typescript
RPCSocket.makeSocket<MyInterface>(port, host).then((async (client) => {
    const r = await client.Group2.echo("hee") //tsc knows about available RPCs 
}))

/* OR */

const client = new Frontend.RPCSocket(port, host)
client.connect<MyInterface>().then((async (client) => {
    const r = await client.Group2.echo("hee") //tsc knows about available RPCs 
})) 
```

Create a server using
```typescript
new RPCServer<{a:string}, MyInterface>(port, 
    [{
        //...
    },{
        name: 'Group2', //Auto completion for names
        exportRPCs: () => [{
            name: 'echo', //this name too!
            call: async (x) => x+"llo World!" //the paramter and return types are known by tsc 
        }]
    }]
)
```

# [Full documentation](https://www.versioncontrol.me/frontwork-documentation/rpclibrary)