// Some custom authoriser which uses auth_key header/queryParam
// and passes user claims onto next function, such as $connect
function customAuthoriser () { ... }

// Websockets $connect action to create a connection for authenticated 
// user + inserts into db using user_id as key
function connect (authClaims) { ... }

// Websockets $disconnect action to remove connection/s 
// for specific user or set of users
function disconnect () { ... }

// Websockets $defaultMessage action to gracefully handle requests
// which are not supported by API
function defaultMessage () { ... }

// Send a message to a connection
// e.g., chat room, which certain user is a part of needs to be notified
// when new messages are sent there
function sendMessage (connectionId, message) { ... }

// Database change stream broadcast event
function broadcast (event) { ... }

# CloudFormation template
MainTable:
  Type: 'AWS::DynamoDB::Table'
  DeletionPolicy: Retain
  Properties:
    TableName: ${self:provider.environment.mainTable}-${self:provider.stage}
    StreamSpecification:
      StreamViewType: NEW_AND_OLD_IMAGES
    ...

export async function broadcast (
  event: DynamoDBStreamEvent,
  context: Context,
  callback: Callback
) {
  const record = event.Records[0].dynamodb;

  // do something with record here
  // e.g., find users who are associated with entity
  // and broadcast change if any open websockets connections
  // match user ids

  ...
}

// https://rxjs-dev.firebaseapp.com/api/webSocket/webSocket
import {webSocket} from 'rxjs/webSocket';

function setup () {
  const apiGatewayWebsocketUrl = 
    'wss://abcd-1234.ap-southeast.aws.amazon.com';
  const subject = webSocket(apiGatewayWebsocketUrl);
    
  subject.subscribe(
    // Called whenever there is a message from the server
    msg => console.log('message received: ' + msg),

    // Called if at any point WebSocket API signals some kind of error
    err => console.log(err),

    // Called when connection is closed (for whatever reason)
    () => console.log('complete')
  );
}

// https://github.com/RxSwiftCommunity/RxStarscream
import RxStarscream

socket = WebSocket(url: URL(string: "ws://localhost:8080/")!)
socket.connect()

socket.rx.response.subscribe(onNext: { (response: WebSocketEvent) in
  switch response {
    case .connected:
      print("Connected")
    case .disconnected(let error):
      print("Disconnected with optional error : \(error)")
    case .message(let msg):
      print("Message : \(msg)")
    case .data(_):
      print("Data")
    case .pong:
      print("Pong")
  }
}).disposed(by: disposeBag)