wirelesstags

wirelesstags - JavaScript API for the Wireless Sensor Tags platform

Aims to provide a well-structured API to the Wireless Sensor Tag platform by interfacing with its JSON Web Service API. It is primarily intended, designed, and tested for server-side use through NodeJS. (However, making it usable within a browser is a future goal, and corresponding contributions are welcome too.)

Installation and setup

$ npm install wirelesstags

The library (specifically, the platform.signin() method, see below) will need authentication information. The library supports two default ways to pick up this information:

1. A file $HOME/.wirelesstags in JSON format, with the necessary authentication information (currently keys username and password). This file should obviously be readable only by the user running the app.
2. Environment variables WIRELESSTAG_API_USER and WIRELESSTAG_API_PASSWORD, if set, will override whatever is found in the default options file.

It is strongly recommended to create a separate account as a "limited user" for using this library rather than your main account(s) at Wirelesstag.com. This makes it easy to change the password or delete the account altogether if the password happens to leak out, and allows controlling which tag managers and tags are visible to the account. Note also that wirelesstag.com stores your password in clear text (you can verify by recovering it), and hence never use a password there that you use anywhere else.

Usage

Principle objects

The principle object hierarchy is the following:

• WirelessTagPlatform: Top-level object representing the cloud interface to the platform. Emits discover events for WirelessTagManager instances upon calling platform.discoverTagManagers().

• WirelessTagManager: Object representing a Tag Manager. Discovered through the platform object. Emits discover events for Wireless Tags associated with the tag manager upon calling tagManager.discoverTags().

• WirelessTag: Object representing a Wireless Tag. Discovered through the tag manager object. Tags have sensor capabilities, which can be queried using tag.hasHumiditySensor() etc methods, or as an array of strings via tag.sensorCapabilities(). Sensor objects can be discovered by calling tag.discoverSensors(), which emits a discover event for each newly found sensor. They can be iterated over using tag.eachSensor(), which takes a callback.

• WirelessTagSensor: Object abstracting a sensor that is part of a Wireless Tag. Sensor objects are of a type (sensor.sensorType), and usually have a reading and an eventState property. They can be armed or disarmed (sensor.arm() and sensor.disarm()), and their monitoring and notification configuration is available as properties of the object returned by sensor.monitoringConfig().

Initialize platform, connect to cloud, and discover tag managers

The platform object can be created using its constructor, or using the static method WirelessTagPlatform.create().

var WirelessTagPlatform = require('wirelesstags');
 
// Passing a config object is optional. Default for apiBaseURI is
// https://www.mytaglist.com
var platform = new WirelessTagPlatform({ apiBaseURI: 'https://my.wirelesstag.com' });

When using the static create() method, it will try to load configuration options from ~/.wirelesstags, or from the environment:

var WirelessTagPlatform = require('wirelesstags');
 
var platform = WirelessTagPlatform.create();

Platform instances emit a connect event after successful logging in, and a discover event for each tag manager object. The signin() and discoverTagManagers() methods also return promises, the latter with an array of tag manager objects.

Define or obtain connection options:

var opts = { username: '[e-mail]', password: 'supersecret' };
// or load from default configuration file or environment variables:
opts = WirelessTagPlatform.loadConfig();

Connect and discover tag managers using event handlers

platform.on('connect', () => {
    console.log("connected to Wireless Tag cloud");
    platform.discoverTagManagers();
});
platform.on('discover', (tagManager) => {
    console.log("found tag manager", tagManager.name, tagManager.mac);
});
// once the listeners are set up we can connect
platform.signin(opts)

A platform instance (since v0.6.0) caches tag manager objects resulting from a call to discoverTagManagers(). Subsequent calls will not update properties of these objects, but emit discover events only for newly found (not previously cached) tag managers. This allows an application to scan periodically for new tag managers, without receiving discover events redundantly for the same objects.

Connect and discover tag managers using returned promises

platform.connect(opts).then(() => {
    return platform.discoverTagManagers();
}).then((tagManagers) => {
    tagManagers.forEach((tagManager) => {
        console.log("found tag manager", tagManager.name, tagManager.mac);
    });
});

The method always promises all tag manager objects found (hence the number of discover events fired will only on the first call be the same as the number of objects promised). Since v0.6.0, if called repeatedly the objects promised for tag managers discovered previously will be the same (but with updated properties), allowing an application to scan periodically for new tag managers without losing the application's state of prviously returnd objects.

Discovering tags and their sensors

The tag manager object emits discover events for each tag associated with it after starting discovery by calling tagManager.discoverTags(). In the same way, tag objects emit discover events for each of their newly found sensors after initiating discovery with tag.discoverSensors().

The discovery methods also promise arrays of tags and sensors, respectively. Either approach (promises or events) can be used.

The tag.discoverSensors() method always promises an array of all its sensors, whereas it emits discover events only for newly found sensors. Subsequent tag.discoverSensors() calls will promise the same sensor objects (unless there were new sensors, but the current generation of Wireless Tags cannot dynamically gain sensors).

In contrast, tagManager.discoverTags() always emits the same number of events as there are elements in the promised array of tag objects, and the tag objects are always new objects, because tag manager objects don't cache their associated tag objects. Indeed in practice tags can be dynamically associated with or disassociated from tag managers.

Discovering tags and sensors using event handlers

tagManager.on('discover', (tag) => {
    console.log("Tag", tag.name, "(slaveId=" + tag.slaveId + ")", tag.uuid);
    console.log(".. last updated", tag.lastUpdated());
    tag.on('discover', (sensor) => {
        console.log("..", sensor.sensorType, "of", sensor.wirelessTag.name);
        console.log("    reading:", sensor.reading);
        console.log("    state:", sensor.eventState);
        console.log("    armed:", sensor.isArmed());
    });
    tag.discoverSensors();
});
tagManager.discoverTags();

Discovering tags and sensors using promises

tagManager.discoverTags().then((tags) => {
    tags.forEach((tag) => {
        console.log("Tag", tag.name, "(slaveId=" + tag.slaveId + ")", tag.uuid);
    });
    return Promise.all(tags.map((tag) => { return tag.discoverSensors(); }));
}).then((sensorLists) => {
    sensorLists.forEach((sensors) => {
        var tag = sensors[0].wirelessTag;
        console.log("Sensors of tag", tag.name, tag.uuid);
        sensors.forEach((sensor) => {
            console.log("..", sensor.sensorType, "sensor");
            console.log("    reading:", sensor.reading);
            console.log("    state:", sensor.eventState);
            console.log("    armed:", sensor.isArmed());
        });
    });
});

Discovering tags and sensors directly from platform

Since v0.6.0, tag objects can be discovered directly in one go from the platform object, without first finding the tag manager objects.

In terms of performance as determined by the sequence of cloud API calls, there is no difference to finding the tag managers first if only one tag manager is accessible to the connected account. However, in the case of multiple tag managers under the account, the difference can be notable (because currently the cloud API does not support filtering tags by tag manager at the server).

platform.discoverTags().then((tags) => {
    tags.forEach((tag) => {
        console.log("Tag", tag.name, "of", tag,wirelessTagManager.name,
                    "(slaveId=" + tag.slaveId + ")", tag.uuid);
    });
    // the following may need rate-limiting if there are many tags
    // (e.g., see package p-limit for rate-limiting promises)
    return Promise.all(tags.map((tag) => { return tag.discoverSensors(); }));
}).then((sensorLists) => {
    sensorLists.forEach((sensors) => {
        var tag = sensors[0].wirelessTag;
        console.log("Sensors of tag", tag.name, tag.uuid);
        sensors.forEach((sensor) => {
            console.log("..", sensor.sensorType, "sensor");
            console.log("    reading:", sensor.reading);
            console.log("    state:", sensor.eventState);
            console.log("    armed:", sensor.isArmed());
        });
    });
});

Finding a specific tag

Each tag is uniquely identified by a UUID (available as tag.uuid). This could be used to pass a query to platform.discoverTags():

var uuidOfTag = 'DESIRED UUID VALUE';
platform.discoverTags({ uuid: uuidOfTag }).then((tags) => {
    if (tags.length === 0) throw new Error("tag not found");
    return tags[0].discoverSensors();
}).then((sensorList) => {
    var tag = sensorList[0].wirelessTag;
    console.log("Sensors of tag", tag.name, tag.uuid);
    sensorList.forEach((sensor) => {
        console.log("..", sensor.sensorType, "sensor");
        console.log("    reading:", sensor.reading);
        console.log("    state:", sensor.eventState);
        console.log("    armed:", sensor.isArmed());
    });
});

It should be noted that this has no performance advantage over filtering the list of tag objects from platform.discoverTags(), because the JSON Web Service API has no server-side support for querying by UUID.

Another way to uniquely (at a moment in time) specify a tag is by tag manager (as identified by its MAC) and the tag's slaveId (a consecutive numbering for the tags associated with a tag manager):

var MAC = '123456789ABCDEF' // replace with MAC of tag manager;
var slaveId = 12; // replace with slave ID of desired tag;
platform.findTagManager(MAC).then((tagMgr) => {
    if (! tagMgr) throw new Error("tag manager not found");
    return tagMgr.findTagById(slaveId); // rejects if not found
}).then((tag) => tag.discoverSensors()).then((sensorList) => {
    var tag = sensorList[0].wirelessTag;
    console.log("Sensors of tag", tag.name, tag.uuid);
    sensorList.forEach((sensor) => {
        console.log("..", sensor.sensorType, "sensor");
        console.log("    reading:", sensor.reading);
        console.log("    state:", sensor.eventState);
        console.log("    armed:", sensor.isArmed());
    });
}).catch((err) => console.error(err.stack ? err.stack : err));

For an account with access to many tags this may perform noticeably better than filtering by UUID, because once the tag manager is found (and the number of tag managers is likely at least an order of magnitude smaller than the number of tags), obtaining the tag's data by slaveId is supported server-side.

Accessing sensors through tag object

Once the promise returned from tag.discoverSensors() is fulfilled, sensor objects can also be accessed through the methods of the tag object (because tag objects cache their sensors, and in practice sensors can't be associated with or disassociated from a tag dynamically). Either use tag.eachSensor() with a callback that accepts a sensor object, or use each sensor's individual accessor property, which are all named zzzzSensor, where zzzz is the type of sensor, for example tag.lightSensor. The method tag.sensorCapabilities() returns an array of strings denoting the possible zzzz values.

Changing the temperature unit

By default temperature sensors give their readings and monitoring thresholds in ºC. The unit can be changed by setting sensor.monitoringConfig().unit:

if (sensor.sensorType === "temp") {
    // temperature reading and thresholds in ºC:
    sensor.monitoringConfig().unit = "degC";
    // temperature reading and thresholds in ºF:
    sensor.monitoringConfig().unit = "degF";
    // if desired, the change can be saved to become persistent:
    sensor.monitoringConfig().save().then((mconfig) => {
        console.log("saved monitoring config of temp of", sensor.wirelessTag.name);
        console.log("... unit is now", mconfig.unit);
    });
}

Updating sensor values and tag information

Updating the tag object's data also updates its sensors. tag.update() updates a tag object's data from the cloud, and tag.liveUpdate() requests that the tag immediately post its latest information.

To regularly update a tag object's data whenver the tag posts its latest information, a loop can be started with tag.startUpdateLoop(), and stopped by tag.stopUpdateLoop().

Promises versus Callbacks

The library attempts to support both returning Promises from API-calling asynchronous functions, and the traditional callback mechanism.

Callbacks are generally called with an error as the first argument if one occurred, and as the second argument with an object that has keys object (the object in which the operation was performed), and value (the resulting value from that operation) if the operation had a result that is not saving or updating a property value of the object. For example, in platform.isConnected(cb), cb will be called with { object: platform, value: false } if the instance wasn't yet connected.

It is considered a bad idea, and not supported (even if it may often work) to mix passing callbacks and using the returned Promises.

Note that callback behaviour is not currently tested as part of the test suite, so there could be bugs.

Full documentation

As of v0.7.0, API documentation is fairly complete:

• Online API documentation
• See the examples/ directory for tutorial scripts that give basic, but fully working demonstrations of how the library can be used.

This library should be considered beta. Use at your own peril. Aside from the API documentation, consider looking at the (fairly extensive) test suite for guidance.

How to support

Aside from reporting issues and contributing pull requests, if you plan to buy from Wireless Sensor Tag, please consider using this link to their website. If more than 10 people do so, and some end up buying, I stand to receive a discount on a past purchase of mine, which will allow me to buy other types of tags in the future and support those too. (See #45 for an example.)

License

Available under the MIT License.