Table of Contents

• Introduction
• Features
• Examples
  • Express
• API
  • request
  • response
  • payload
  • endpoint
• Request Handlers
  • Discovery
  • CameraStreamController
• Execute Code On Every Request
  • pre()
  • post()
• License

alexa-smart-home-app

A Node module to simplify the development of Alexa skills (applications.) This module is clone for alexa-app then redesign for alexa smart home skill

Introduction

This module parses HTTP JSON requests from the Alexa platform and builds the JSON response that consumed by an Alexa-compatible device, such as the Echo.

It provides a DSL for defining event.

Features

Examples

Express

var express = require("express");
var alexa = require("alexa-app");
var express_app = express();
 
var app = new alexa.app("sample");
 
// setup the alexa app and attach it to express before anything else
app.express({ expressApp: express_app });
 
// now POST calls to /sample in express will be handled by the app.request() function
// GET calls will not be handled
 
// from here on, you can setup any other express routes or middleware as normal

The express function accepts the following parameters.

• expressApp the express app instance to attach to
• router the express router instance to attach to
• endpoint the path to attach the express app or router to (e.g., passing 'mine' attaches to /mine)
• preRequest function to execute before every POST
• postRequest function to execute after every POST

Either expressApp or router is required.

A full express example is available here.

API

Skills define handlers for Discovery, CameraStreamController, and SceneController, just like normal Alexa development. The alexa-smart-home-app module provides a layer around this functionality that simplifies the interaction. Each handler gets passed a request and response object, which are custom for this module.

request

// return the namespace of request received
String request.namespace()
 
// check if the namespace is discover
Boolean request.isDiscover()
 
// check if the namespace is camera stream controller
Boolean request.isCameraStreamController()
 
// check if the namespace is sceneController
Boolean request.isSceneController()
 
// return the header object
Dialog request.getHeader()
 
// check if you can read header
Boolean request.hasHeader()
 
// return the payload object
Dialog request.getPayload()
 
// check if you can read payload
Boolean request.hasPayload()
 
// return the endpoint object
Dialog request.getEndpoint()
 
// check if you can read endpoint
Boolean request.hasEndpoint()
 
// the raw request JSON object
request.data

response

The response JSON object is automatically built for you. All you need to do is tell it what you want to output.

 
// alexa-discovery @see https://developer.amazon.com/zh/docs/device-apis/alexa-discovery.html
// skill supports discovery
response.endpoint(Object endpoint)
 
// alexa-camerastreamcontroller @see https://developer.amazon.com/zh/docs/device-apis/alexa-camerastreamcontroller.html
// skill supports camerastreamcontroller
response.cameraStream(Object stream)
 
// alexa-camerastreamcontroller @see https://developer.amazon.com/zh/docs/device-apis/alexa-camerastreamcontroller.html
// skill supports camerastreamcontroller
response.sceneController(Object scene)
 
// alexa-errorresponse @see https://developer.amazon.com/zh/docs/device-apis/alexa-errorresponse.html
// skill supports error response
response.errorResponse(String type, String message)
 
// send the response to the Alexa device (success) immediately
// this returns a promise that you must return to continue the
// promise chain. Calling this is optional in most cases as it
// will be called automatically when the handler promise chain
// resolves, but you can call it and return its value in the
// chain to send the response immediately. You can also use it
// to send a response from `post` after failure.
async response.send()
 
// trigger a response failure
// the internal promise containing the response will be rejected, and should be handled by the calling environment
// instead of the Alexa response being returned, the failure message will be passed
// similar to `response.send()`, you must return the value returned from this call to continue the promise chain
// this is equivalent to calling `throw message` in handlers
// *NOTE:* this does not generate a response compatible with Alexa, so when calling it explicitly you may want to handle the response with `.error` or `.post`
async response.fail(String message)

payload

// check if you can read payload
Boolean request.hasPayload()
 
// get the payload object
var session = request.getPayload()
 
// return the value of a session variable
String payload.get(String key)
 
// payload details, as passed by Amazon in the request
payload.details = { ... }

endpoint

// check if you can read endpoint
Boolean request.hasEndpoint()
 
// get the payload object
var session = request.getEndpoint()
 
// return the value of a endpoint variable
String endpoint.get(String key)
 
// return the endpoint's scope
String endpoint.scope
 
// return the endpoint's endpointId
String endpoint.endpointId
 
// return the endpoint's cookie
String endpoint.cookie
 
// endpoint details, as passed by Amazon in the request
endpoint.details = { ... }

Request Handlers

Your app can define a single handler for the discovery event and the cameraStreamController event, and sceneController event.

Discovery

alexaApp.discovery((request, response) => {
  response.endpoint({
    endpointId: 'uniqueIdOfCameraEndpoint',
    manufacturerName: 'the manufacturer name of the endpoint',
    modelName: 'the model name of the endpoint',
    friendlyName: 'Camera',
    description: 'a description that is shown to the customer',
    displayCategories: ['CAMERA'],
    cookie: {
      key1: 'arbitrary key/value pairs for skill to reference this endpoint.',
      key2: 'There can be multiple entries',
      key3: 'but they should only be used for reference purposes.',
      key4: 'This is not a suitable place to maintain current endpoint state.',
    },
    capabilities: [{
      type: 'AlexaInterface',
      interface: 'Alexa.CameraStreamController',
      version: '3',
      cameraStreamConfigurations: [
        {
          protocols: ['RTSP'],
          resolutions: [{ width: 1920, height: 1080 }, { width: 1280, height: 720 }],
          authorizationTypes: ['BASIC'],
          videoCodecs: ['H264', 'MPEG2'],
          audioCodecs: ['G711'],
        },
        {
          protocols: ['RTSP'],
          resolutions: [{ width: 1920, height: 1080 }, { width: 1280, height: 720 }],
          authorizationTypes: ['NONE'],
          videoCodecs: ['H264'],
          audioCodecs: ['AAC'],
        },
      ],
    }],
  });
});

CameraStreamController

alexaApp.cameraStreamController((request, response) => {
  response.cameraStream({
    uri: 'rtsp://username:[e-mail]:443/feed1.mp4',
    expirationTime: '2017-09-27T20:30:30.45Z',
    idleTimeoutSeconds: 30,
    protocol: 'RTSP',
    resolution: {
      width: 1920,
      height: 1080,
    },
    authorizationType: 'BASIC',
    videoCodec: 'H264',
    audioCodec: 'AAC',
  });
});

Execute Code On Every Request

In addition to specific event handlers, you can define functions that will run on every request.

pre()

Executed before any event handlers. This is useful to setup new payload, validate the token, or do any other kind of validations. You can perform asynchronous functionality in pre by returning a Promise.

app.pre = function(request, response, namespace) {
  if (request.hasPayload() && request.getPayload().token != "User Token") {
    // fail ungracefully
    throw "Invalid token";
  }
};
 
// Asynchronous
app.pre = function(request, response, namespace) {
  return db.getUserToken().then(function(token) {
    if (request.hasPayload() && request.getPayload().token != token) {
      throw new Error("Invalid token");
    }
  });
};

Note that the post() method still gets called, even if the pre() function calls send() or fail(). The post method can always override anything done before it.

post()

The last thing executed for every request. It is even called if there is an exception or if a response has already been sent. The post() function can change anything about the response. It can even turn a return response.fail() into a return respond.send() with entirely new content. If post() is called after an exception is thrown, the exception itself will be the 4th argument.

You can perform asynchronous functionality in pre by returning a Promise similar to pre or any of the handlers.

app.post = function(request, response, namespace, exception) {
  if (exception) {
    // always turn an exception into a successful response
    return response.send();
  }
};

Customizing Default Error Messages

app.messages.INVALID_REQUEST_NAMESPACE = "Sorry, the application didn't know what to do with that namespace";

See the code for default messages you can override.

License

Copyright (c) 2018 Clarence Lin

MIT License, see LICENSE for details.