Step 7 - Connect the worker to Wolfram Alpha

Author: mattheworiordan

example.js

@@ -3,8 +3,11 @@ const Express = require('express');
 const ServerPort = 3000;
 const worker = require('./worker');
 
-const ApiKey = 'INSERT-YOUR-API-KEY-HERE'; /* Add your API key here */
-if (ApiKey.indexOf('INSERT') === 0) { throw('Cannot run without an API key. Add your key to example.js'); }
+const ApiKey = 'INSERT-YOUR-API-KEY-HERE'; /* Add your Ably API key here */
+if (ApiKey.indexOf('INSERT') === 0) { throw('Cannot run without an Ably API key. Add your key to example.js'); }
+
+const WolframAppId = 'INSERT-YOUR-WOLFRAM-API-KEY-HERE'; /* Add your Wolfram AppID here */
+if (ApiKey.indexOf('INSERT') === 0) { throw('Cannot run without a Wolfram API key. Add your key to example.js'); }
 
 /* Instance the Ably library */
 var rest = new Ably.Rest({ key: ApiKey });
@@ -29,6 +32,6 @@ app.get('/auth', function (req, res) {
 app.use(express.static('public'));
 app.listen(3000);
 
-worker.start(ApiKey, 'wolfram:answers', 'wolfram', 'us-east-1-a-queue.ably.io:5671/shared');
+worker.start(ApiKey, WolframAppId, 'wolfram:answers', 'wolfram', 'us-east-1-a-queue.ably.io:5671/shared');
 
 console.log('Open the Wolfram demo in your browser: https://localhost:' + ServerPort + '/');

package.json

@@ -13,6 +13,7 @@
     "dependencies": {
         "ably": ">=0.9.0-beta",
         "amqplib": "^0.4",
-        "express": ">=4.14.0"
+        "express": ">=4.14.0",
+        "request": ">=2.79.0"
     }
 }

worker.js

@@ -2,9 +2,38 @@
 
 const amqp = require('amqplib/callback_api');
 const Ably = require('ably');
+const request = require('request');
+const querystring = require("querystring");
+const WolframEndpoint = 'http://api.wolframalpha.com/v1/result';
+
+/* Send question over HTTP to Wolfram to find the answer */
+function getAnswerAndPublish(ablyChannel, wolframUrl, question) {
+  console.log('worker:', 'Received question', question, ' - about to ask Wolfram');
+  var timeNow = Date.now();
+  request(wolframUrl, function (error, response, body) {
+    var timePassed = Date.now() - timeNow;
+    if (!error && response.statusCode == 200) {
+      publishAnswer(ablyChannel, question, body, timePassed)
+    } else {
+      if (body) {
+        publishAnswer(ablyChannel, question, "Wolfram couldn't compute: " + body, timePassed);
+      } else {
+        publishAnswer(ablyChannel, question, "Wolfram error: " + JSON.stringify(error), timePassed);
+      }
+    }
+  });
+}
+
+function publishAnswer(ablyChannel, question, answer, wolframTime) {
+  ablyChannel.publish('answer', { question: question, answer: answer, wolframTime: wolframTime }, function(err) {
+    if (err) {
+      console.error('worker:', 'Failed to publish question', question, ' - err:', JSON.stringify(err));
+    }
+  })
+}
 
 /* Start the worker that consumes from the AMQP QUEUE */
-exports.start = function(apiKey, answersChannelName, queueName, queueEndpoint) {
+exports.start = function(apiKey, wolframApiKey, answersChannelName, queueName, queueEndpoint) {
   const appId = apiKey.split('.')[0];
   const queue = appId + ":" + queueName;
   const endpoint = queueEndpoint;
@@ -34,12 +63,9 @@ exports.start = function(apiKey, answersChannelName, queueName, queueEndpoint) {
 
         const messages = Ably.Realtime.Message.fromEncodedArray(decodedEnvelope.messages);
         messages.forEach(function(message) {
-          console.log('worker:', 'Received question', message.data, ' - about to ask Wolfram');
-          answersChannel.publish('answer', 'Placeholder until Wolfram connected', function(err) {
-            if (err) {
-              console.error('worker:', 'Failed to publish question', message.data, ' - err:', JSON.stringify(err));
-            }
-          })
+          var question = message.data;
+          var url = WolframEndpoint + '?' + querystring.stringify({ appid: wolframApiKey, i: question});
+          getAnswerAndPublish(answersChannel, url, question);
         });
 
         /* Remove message from queue */