HTTP request with Alexa and Lambda on SDK v2, how to make it works?

Question

I am playing with ASK SDK v2 provided by Amazon in order to make Skill for Alexa but I face an architectural problem :

First of all, the HTTP request works like a charm but I would like to return speach response if and only if my HTTP request is complete but I don't even know if it's possible because of the "handle" function that should return something (look at comments) :

const MyIntentHandler = {

  canHandle(handlerInput) {
    const request = handlerInput.requestEnvelope.request;
    return request.type === 'LaunchRequest' || (request.type === 'IntentRequest' && request.intent.name === 'MyIntent');
  },
  handle(handlerInput) {

    var options = {
      host: 'http://foo.com',
      port: 80,
      path: '/mypath',
      method: 'GET'
    };

    var req = http.request(options, function(result){
      result.on("end", function(){
        //I would like to return speak here like that :
        //return handlerInput.responseBuilder.speak("It works").withSimpleCard("MyTestApp", "It works").getResponse()
      })
    });
    req.end();
    //And I would like to remove this line to manage response in result.on("end", function(){}) above
    return handlerInput.responseBuilder.speak("It works").withSimpleCard("MyTestApp", "It works").getResponse();
  },
};

Any idea to deal with this ?

Answer 1

I found the official way to make it :

1) Create a new funtion that manage http request and return a promise :

function httpGet(options) {
  return new Promise(((resolve, reject) => {

    const request = http.request(options, (response) => {
      response.setEncoding('utf8');
      let returnData = '';

      if (response.statusCode < 200 || response.statusCode >= 300) {
        return reject(new Error(`${response.statusCode}: ${response.req.getHeader('host')} ${response.req.path}`));
      }

      response.on('data', (chunk) => {
        returnData += chunk;
      });

      response.on('end', () => {
        resolve(JSON.parse(returnData));
      });

      response.on('error', (error) => {
        reject(error);
      });
    });
    
    request.on('error', function (error) {
      reject(error);
    });
    
    request.end();
  }));
}

2) In the Intent, return a promise in which you call your httpGet function :

const MyIntentHandler = {

  canHandle(handlerInput) {
    const request = handlerInput.requestEnvelope.request;
    return request.type === 'LaunchRequest' || (request.type === 'IntentRequest' && request.intent.name === 'MyIntent');
  },
  handle(handlerInput) {

    var options = {
      host: 'http://foo.com',
      port: 80,
      path: '/mypath',
      method: 'GET'
    };

    return new Promise((resolve, reject) => {
     httpGet(options).then((response) => {
       resolve(handlerInput.responseBuilder.speak("It is done.").getResponse());
     }).catch((error) => {
        resolve(handlerInput.responseBuilder.speak('Thor is not available at the moment. Please try again later or contact your administrator.')
        .getResponse());
      });
    });
  },
};

This is the way to do it properly. My example is base on alexa petmatch sample.