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index.js
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index.js
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/**
* @author Ryan Ward
* @version 1.4
*
* This is a small alexa skill that can tell a user the price of several different cryptocurrencies.
* Currently the skill only responds with the USD value of each cryptocurrency.
*
* Please note that this is the first released version on the Alexa Skill Store.
*
* Future Plans:
* - Support different currencies other than USD, depending on the location of the user.
*/
"use strict";
// Include the Alexa SDK
var Alexa = require("alexa-sdk");
// Include https to be able to make api calls.
var https = require("https");
// The different messages corresponding to the different intents.
var errorMessage = "I'm sorry, I didn't get that. Could you please ask again?";
var helpMessage = "Simply ask for the price of any popular cryptocurrency. For example you could say, 'ask coin check for the current price of Bitcoin.'";
var launchMessage = "Welcome to coin check! What currency do you want to hear the price of?";
var goodbyeMessage = "Goodbye!";
var thresholdMessage = "Please ask for the top one or more cryptocurrencies. Could you please ask again?"
var DEFAULT_TOP_CURRENCIES = 5;
// The handlers object tells Alexa how to handle various actions
var handlers = {
/**
* The LaunchRequest is called when the user asks 'Alexa open coin check.'
*/
"LaunchRequest": function ()
{
this.emit(":ask", launchMessage);
this.emit(":responseReady");
},
/**
* The HelpIntent is called when the user responds to the prompt with 'Help.'
*/
"AMAZON.HelpIntent": function() {
this.emit(":ask", helpMessage);
this.emit(":responseReady");
},
/**
* The PriceIntent is called when the user responds to the prompt with the name
* of a popular cryptocurrency.
*/
"PriceIntent": function ()
{
var answerSlotValid = isAnswerSlotValid(this.event.request.intent);
if (!answerSlotValid || this.event.request.intent.slots.cryptocurrency.value == null) {
this.emit(":ask", errorMessage);
this.emit(":responseReady");
}
else {
var crypto = this.event.request.intent.slots.cryptocurrency.value;
if (typeof(crypto) != "undefined")
{
crypto = crypto.toLowerCase();
crypto = crypto.replace(" ", "-");
var path = "https://api.coinmarketcap.com/v1/ticker/" + crypto + "/";
var req = https.get(path, res =>
{
res.setEncoding('utf8');
var returnData = "";
res.on('data', chunk => {
returnData = returnData + chunk;
});
res.on('end', () => {
try {
var result = JSON.parse(returnData);
if (typeof(result[0]) == "undefined") {
this.emit(":ask", errorMessage);
this.emit(":responseReady");
}
else {
var price = result[0].price_usd;
var priceMessage = "The current price of " + crypto + " is " + price + " USD";
this.emit(":tell", priceMessage);
this.emit(":responseReady");
}
}
catch (e) {
this.emit(":ask", errorMessage);
this.emit(":responseReady");
}
});
res.on('error', () => {
this.emit(":ask", errorMessage);
this.emit(":responseReady");
});
});
req.end();
}
}
},
/**
* The TopCurrencies function is called when the user asks for the top currencies.
* If the {number} is left out of the request then the response returns the top 5 currencies.
*/
"TopCurrencies": function() {
var number = this.event.request.intent.slots.number.value;
if (number == null) {
number = DEFAULT_TOP_CURRENCIES;
}
else if (number < 1) {
this.emit(":ask", thresholdMessage);
this.emit(":responseReady");
}
var path = "https://api.coinmarketcap.com/v1/ticker/?limit=" + number;
var req = https.get(path, res =>
{
res.setEncoding('utf8');
var returnData = "";
res.on('data', chunk => {
returnData = returnData + chunk;
});
res.on('end', () => {
try {
var result = JSON.parse(returnData);
if (typeof(result[0]) == "undefined") {
this.emit(":ask", errorMessage);
this.emit(":responseReady");
}
else {
var list = "The top " + number + " currencies are " + currencyList(result);
this.emit(":tell", list);
this.emit(":responseReady");
}
}
catch (e) {
this.emit(":ask", errorMessage);
this.emit(":responseReady");
}
});
res.on('error', () => {
this.emit(":ask", errorMessage);
this.emit(":responseReady");
});
});
req.end();
},
/**
* The Unhandled function is called when an unspecified for in the intent is present.
*/
"Unhandled": function() {
this.emit(":ask", errorMessage);
this.emit(":responseReady");
},
/**
* The CancelIntent function is called when the user responds to the prompt with 'Cancel.'
*/
'AMAZON.CancelIntent': function () {
this.emit(':tell', goodbyeMessage);
},
/**
* The StopIntent function is called when the user responds to the prompt with 'Stop.'
*/
'AMAZON.StopIntent': function () {
this.emit(':tell', goodbyeMessage);
}
};
/**
* Returns false if the answer slot is not valid and true otherwise.
* For example if the answer slot was "", this would return false.
* However if the answer slot was "Bicoin", this would return true.
*/
function isAnswerSlotValid(intent) {
var answerSlotFilled = intent && intent.slots &&
intent.slots.cryptocurrency && intent.slots.cryptocurrency.value;
return answerSlotFilled;
}
/**
* Returns a list of the currencies from the parsed JSON response as a string.
*/
function currencyList(result) {
var list = "";
for (var i = 0; i < result.length - 1; i++) {
list += result[i].name + ", ";
}
list += "and " + result[result.length - 1].name;
return list;
}
// This is the function that AWS Lambda calls every time Alexa uses your skill.
exports.handler = function(event, context, callback) {
// Create an instance of the Alexa library and pass it the requested command.
var alexa = Alexa.handler(event, context);
// Give our Alexa instance instructions for handling commands and execute the request.
alexa.registerHandlers(handlers);
alexa.execute();
};