Nestor has a large and growing directory of powers that lets you add superpowers to your Bot.
But there are scenarios where you would want to write your own powers that power Nestor. For e.g. to access your private stats server, or your own database to get results or make deploys to your own custom infrastructure.
Nestor can be programmed using Javascript to create a powerful bot for your team that can automate away the mundane.
Nestor's API is based on Hubot's API and it tries to be as compatible as possible with Hubot's API -- The Nestor Programming Manual has also been adapted from the Hubot documentation.
Nestor is powered by "powers" that are analogous to Hubot scripts.
A Nestor power is at its most fundamental an NPM package with a couple of caveats:
- It must have nestorbot as a dependency
- It must contain a JSON file called
nestor.jsonwith details about the power. More on that later. - It must export a function that accepts an instance of
[Robot](https://github.com/zerobotlabs/nestorbot/blob/master/src/robot.js)
Something like this:
module.exports = function(robot) {
// Your code goes here...
};Nestor can hear messages said in a Slack channel or respond to
messages directly addressed at it.
A hear method is invoked for every message that is received in a channel whereas respond is invoked when a message is addressed to nestorbot itself (for e.g. "@nestorbot what's the weather now?")
Both methods take a regular expression and a callback function as parameters.
For example:
module.exports = function(robot) {
robot.hear(/gif( me)? (.*?)$/i, function(msg, done) {
// your code here
});
robot.respond(/hello/i, function(msg, done) {
// your code here
});
};The robot.hear(/gif( me)? (.*?)$/i callback is called anytime a message's text matches. For example:
- gif me honey badger
- gif fail whale
- give me a gif star wars
The robot.respond /hello/i callback is only called for messages that are immediately preceded by nestorbot's nickname.
- @nestorbot: hello
- hello @nestorbot
It wouldn't be called for:
- nestorbot hello
- because it doesn't contain the Slack User ID for nestorbot
- hello
- because it is not addressed to nestorbot
The msg parameter is an instance of Response. With it, you can send a message back to the channel the msg came from, or reply to the person that sent the message. For example:
module.exports = function(robot) {
robot.hear(/gif me honeybadger/i, function(msg, done) {
msg.send("https://media.giphy.com/media/aui0RuYoqtRa8/giphy-facebook_s.jpg", done)
});
robot.respond(/weather in san francisco/i, function(msg, done) {
msg.reply("sunny and awesome", done);
});
};The robot.hear /gif me honeybadgers/ callback sends a message exactly as specified regardless of who said it, "https://media.giphy.com/media/aui0RuYoqtRa8/giphy-facebook_s.jpg"
If a user Bob says "@nestorbot: weather in san francisco", robot.respond /weather in san francisco/i callback sends a message "@bob: sunny and awesome"
For users familiar with the existing Hubot API, you might have been
curious about the presence of a "done" argument in robot.hear and
robot.respond. This is because Nestor powers are invoked in
container-ized sandboxes that exit once the power has been completed.
Since node.js methods are asynchronous, we need to let the Nestor Power
Execution Engine that the power has completed -- and that's where the
done argument comes in. When done is passed as an argument to either
send or reply the Execution Engine will then "return" from the
function and the power will no longer be executed.
If you need to send data more than once, not to worry -- msg.reply and
msg.send return promises that can be used to order messages in a given
sequence. As an example:
module.exports = function(robot) {
robot.respond(/weather in san francisco/i, function(msg, done) {
msg.reply("sunny and awesome").then(function() {
msg.send("the best weather", done);
});
});
};will first send "sunny and awesome", followed by "the best weather".
So far, our powers have had static responses, which while amusing, are boring functionality-wise. msg.match has the result of matching the incoming message against the regular expression. This is just a JavaScript thing, which ends up being an array with index 0 being the full text matching the expression. If you include capture groups, those will be populated res.match. For example, if we update an power like:
module.exports = function(robot) {
robot.respond(/weather in (.*)/i, function(msg, done) {
// your code here
});
};If Bob says "@nestorbot: weather in san francisco", then res.match[0] is "weather in san francisco", and res.match[1] is just "san francisco". Now we can start doing more dynamic things:
module.exports = function(robot) {
robot.respond(/weather in (.*)/i, function(msg, done) {
location = msg.match[1];
if(location == "san francisco") {
msg.reply("sunny and awesome", done);
} else {
msg.reply("i don't know", done);
}
});
};Nestorbot can make HTTP calls on your behalf to integrate & consume third party APIs. This can be through an instance of node-scoped-http-client available at robot.http. The simplest case looks like:
module.exports = function(robot) {
robot.http("https://my-favorite-website").get()(function(err, res, body) {
// Your code here
});
};A post looks like:
module.exports = function(robot) {
var data = JSON.stringify({
foo: 'bar'
});
robot.http("https://my-favorite-website").
header('Content-Type', 'application/json').
post(data)(function(err, res, body) {
// Your Code Here
});
};err is an error encountered on the way, if one was encountered. You'll generally want to check for this and handle accordingly:
module.exports = function(robot) {
robot.http("https://my-favorite-website").get()(function(err, res, body) {
if (err) {
msg.send("Encountered an error :( " + err);
}
// Your code here -- knowing the HTTP call was successful
});
};res is an instance of node's http.ServerResponse. Most of the methods don't matter as much when using HttpClient, but of interest are statusCode and getHeader. Use statusCode to check for the HTTP status code, where usually non-200 means something bad happened. Use getHeader for peeking at the header, for example to check for rate limiting:
module.exports = function(robot) {
robot.http("https://my-favorite-website").get()(function(err, res, body) {
var rateLimitRemaining;
if (res.statusCode !== 200) {
msg.send("Request didn't come back HTTP 200 :(", done);
}
if (res.getHeader('X-RateLimit-Limit')) {
rateLimitRemaining = parseInt(res.getHeader('X-RateLimit-Limit'));
}
if (rateLimitRemaining && rateLimitRemaining < 1) {
msg.send("Rate Limit hit, stop believing for awhile", done);
}
// Rest of your code
});
};body is the response's body as a string, the thing you probably care about the most:
module.exports = function(robot) {
robot.http("https://my-favorite-website").get()(function(err, res, body) {
msg.send("Got back " + body);
});
};If you are talking to APIs, the easiest way is going to be JSON because it doesn't require any extra dependencies. When making the robot.http call, you should usually set the Accept header to give the API a clue that's what you are expecting back. Once you get the body back, you can parse it with JSON.parse:
module.exports = function(robot) {
robot.http("https://my-favorite-api").
header('Accept', 'application/json').
get()(function(err, res, body) {
var data = JSON.parse(body);
msg.send(data.key + " value is " + data.value);
});
};It's possible to get non-JSON back, like if the API hit an error and it tries to render a normal HTML error instead of JSON. To be on the safe side, you should check the Content-Type, and catch any errors while parsing.
module.exports = function(robot) {
robot.http("https://my-favorite-api").
header('Accept', 'application/json').
get()(function(err, res, body) {
var data, error;
if (response.getHeader('Content-Type') !== 'application/json') {
msg.send("Didn't get back JSON :(");
return;
}
data = null;
try {
return data = JSON.parse(body);
} catch (_error) {
error = _error;
msg.send("Ran into an error parsing JSON :(");
}
});
};XML APIs are harder because there's not a bundled XML parsing library. It's beyond the scope of this documentation to go into detail, but here are a few libraries to check out:
- xml2json (simplest to use, but has some limitations)
- jsdom (JavaScript implementation of the W3C DOM)
- xml2js
For those times that there isn't an API, there's always the possibility of screen-scraping. It's beyond the scope of this documentation to go into detail, but here's a few libraries to check out:
As mentioned, nestorbot uses node-scoped-http-client to provide a simple interface for making HTTP and HTTP requests. Under its hood, it's using node's builtin http and https libraries, but providing an easy DSL for the most common kinds of interaction.
In addition, if node-scoped-http-client doesn't suit you, you can can use http and https yourself directly, or any other node library like request.
If you use API keys and other secrets in your power, it's not a good idea to hard code them in your code. Nestorbot allows you to have environment variables in your power so that code & data can be kept separate. You can set environment variables in the power by going to the section titled "Environment" for each power.
module.exports = function(robot) {
robot.respond(/what is the answer to the ultimate question of life/, function(msg, done) {
answer = process.env.HUBOT_ANSWER_TO_THE_ULTIMATE_QUESTION_OF_LIFE_THE_UNIVERSE_AND_EVERYTHING;
msg.send(answer + ", but what is the question?", done);
});
};We can also check if the environment variable is set and respond accordingly.
module.exports = function(robot) {
robot.respond(/what is the answer to the ultimate question of life/, function(msg, done) {
answer = process.env.HUBOT_ANSWER_TO_THE_ULTIMATE_QUESTION_OF_LIFE_THE_UNIVERSE_AND_EVERYTHING;
if (answer == null) {
msg.send("Missing HUBOT_ANSWER_TO_THE_ULTIMATE_QUESTION_OF_LIFE_THE_UNIVERSE_AND_EVERYTHING in environment: please set and try again", done);
}
msg.send(answer + ", but what is the question?", done);
});
};Nestorbot has a persistent key-value store exposed as robot.brain that can be
used to store and retrieve data by powers.
robot.respond(/have a soda/i, function(res, done) {
// Get number of sodas had (coerced to a number).
var sodasHad = robot.brain.get('totalSodas') * 1 || 0;
if(sodasHad > 4) {
res.reply("I'm too fizzy..", done);
} else {
res.reply('Sure!', done);
}
robot.brain.set('totalSodas', sodasHad+1);
}
robot.respond(/sleep it off/i, function(res, done) {
robot.brain.set('totalSodas', 0);
msg.reply('zzzzz', done);
}If the power needs to lookup user data, there are methods on robot.brain for looking up one or many users by id, name, or 'fuzzy' matching of name: userForName, userForId, and usersForFuzzyName.
module.exports = function(robot) {
robot.respond(/who is @?([\w .\-]+)\?*$/i, function(res, done) {
name = res.match[1].trim();
users = robot.brain.usersForFuzzyName(name);
if(users.length >= 1) {
var user = users[0]
// Do something interesting here..
res.send(name + " is user " user, done);
}
};
};- The filesystem available to Nestor powers is not persistent. Any files that you write will not be available on the next run of the power.
- You have a maximum of 60 seconds to complete a request made to Nestorbot. If there are use cases for which you'd want longer execution time, please get in touch at [email protected].
If you have feature requests, bug reports in both the power as well as the manual, please raise an issue.