Add (partial) support for IoT XEPs

That is XEP-0323, -0324, -0325, and -0347.

SMACK-727.

documentation/extensions/iot.md

@@ -0,0 +1,116 @@
+Internet of Things (XEP-0323, -0324, -0325, -0347)
+==================================================
+
+The Internet of Things (IoT) XEPs are an experimental open standard how XMPP can be used for IoT. They currently consists of
+- XEP-0323 Sensor Data
+- XEP-0324 Provisioning
+- XEP-0325 Control
+- XEP-0326 Concentrators
+- XEP-0347 Discovery
+
+Smack only supports a subset of the functionality described by the XEPs!
+
+Thing Builder
+-------------
+
+The `org.jivesoftware.smackx.iot.Thing` class acts as basic entity representing a single "Thing" which can used to retrieve data from or to send control commands to. `Things` are constructed using a builder API.
+
+
+Reading data from things
+------------------------
+
+For example, we can build a Thing which provides the current temperature with
+
+```java
+Thing dataThing = Thing.builder().setKey(key).setSerialNumber(sn).setMomentaryReadOutRequestHandler(new ThingMomentaryReadOutRequest() {
+    @Override
+    public void momentaryReadOutRequest(ThingMomentaryReadOutResult callback) {
+        int temp = getCurrentTemperature();
+        IoTDataField.IntField field = new IntField("temperature", temp);
+        callback.momentaryReadOut(Collections.singletonList(field));
+    }
+}).build();
+```
+
+While not strictly required, most things are identified via a key and serial number. We also build the thing with a "momentary read out request handler" which when triggered, retrieved the current temperature and reports it back to the requestor.
+
+After the `Thing` is build, it needs to be made available so that other entities within the federated XMPP network can use it. Right now, we only intall the Thing in the `IoTDataManager`, which means the thing will act on read out requests but not be managed by a provisioning server.
+
+```java
+IoTDataManager iotDataManager = IoTDataManager.getInstanceFor(connection);
+iotDataManager.installThing(thing);
+```
+
+The data can be read out also by using the `IoTDataManager`:
+
+```java
+FullJid jid = …
+List<IoTFieldsExtension> values = iotDataManager.requestMomentaryValuesReadOut(jid);
+```
+
+Now you have to unwrap the `IoTDataField` instances from the `IoTFieldsExtension`. Note that Smack currently only supports a subset of the specified data types.
+
+Controlling a thing
+-------------------
+
+Things can also be controlled, e.g. to turn on a light. Let's create thing which can be used to turn the light on and off.
+
+```java
+Thing controlThing = Thing.builder().setKey(key).setSerialNumber(sn).setControlRequestHandler(new ThingControlRequest() {
+    @Override
+    public void processRequest(Jid from, Collection<SetData> setData) throws XMPPErrorException {
+        for (final SetData data : setData) {
+            if (!data.getName().equals("light")) continue;
+            if (!(data instanceof SetBoolData)) continue;
+            SetBoolData boolData = (SetBoolData) data;
+            setLight(boolData.getBooleanValue());
+        }
+    }
+}).build();
+```
+
+No we have to install this thing into the `IoTControlManager`:
+
+```java
+IoTControlManager iotControlManager = IoTControlManager.getInstanceFor(connection);
+iotControlManager.installThing(thing);
+```
+
+The `IoTControlManager` can also be used to control a thing:
+
+```java
+FullJid jid = …
+SetData setData = new SetBoolData("light", true);
+iotControlManager.setUsingIq(jid, setData);
+```
+
+Smack currently only supports a subset of the possible data types for set data.
+
+Discovery
+---------
+
+You may wondered how a full JIDs of things can be determined. One approach is using the discovery mechanisms specified in XEP-0347. Smack provides the `IoTDiscoveryManager` as API for this.
+
+For example, instead of just installing the previous things in the `IoTDataManager` and/or `IoTControlManager`, we could also use the `IoTDiscoveryManger` to register the thing with a registry. Doing thing also installs the thing in the `IoTDataManager` and the `IoTControlManager`.
+
+```java
+IoTDiscoveryManager iotDiscoveryManager = IoTDiscoveryManager.getInstanceFor(connection);
+iotDiscovyerManager.registerThing(thing);
+```
+
+The registry will now make the thing known to a broader audience, and available for a potential owner.
+
+The `IoTDiscoveryManager` can also be used to claim, disown, remove and unregister a thing.
+
+Provisioning
+------------
+
+Things can usually only be used by other things if they are friends. Since a thing normally can't decide on its own if an incoming friendship request should be granted or not, we can delegate this decission to a provisioning service. Smack provides the `IoTProvisinoManager` to deal with friendship and provisioning.
+
+For example, if you want to befriend another thing:
+
+```java
+BareJid jid = …
+IoTProvisioningManager iotProvisioningManager = IoTProvisioningManager.getInstanceFor(connection);
+iotProvisioningManager.sendFriendshipRequest(jid);
+```