Add support for QoS in sample.

[DenisBiryukov91]

Add support for QoS in sample (see eclipse-zenoh/zenoh#730)

[eclipse-zenoh-bot]

@DenisBiryukov91 If this pull request contains a bugfix or a new feature, then please consider using Closes #ISSUE-NUMBER syntax to link it to an issue.

[DariusIMP]

Thanks Denis, I just left a couple of comments :)

[DariusIMP]

Why moving sample kind and congestion control under prelude? I wonder because here for instance it's under publication, but it's true that it also appears under prelude (here). So what's the criteria, @p-avital may give us more insight

[DenisBiryukov91]

It was mostly done to avoid circular dependencies between modules (yes, I know that kotlin/java can handle it). Also these types are really not something proper to publication only since they appear in other contexts (especially after this pr)

[DariusIMP]

Ack.

[DariusIMP]

Let's wait for the changes to be under eclipse-zenoh's repository, in order to not make the packages dependent on a private repository.

[DenisBiryukov91]

Fixed

[DariusIMP]

Let me suggest some changes here. So far all the communication through the JNI logic has been subjected to a delegation pattern, in which all the "ViaJNI" functions are contained within "JNI" objects on the 'jni' package in order to centralize that kind of logic there. So for the sake of sticking to that architectural design I'd do:

Suggested change

	/**
	* Quality of service settings used to send zenoh message.
	*/
	class QoS internal constructor(internal val qos: Byte) {
	/**
	* Returns priority of the message.
	*/
	fun priority(): Priority {
	return Priority.fromInt(getPriorityViaJNI(qos))
	}
	/**
	* Returns congestion control setting of the message.
	*/
	fun congestionControl(): CongestionControl {
	return CongestionControl.fromInt(getCongestionControlViaJNI(qos))
	}
	/**
	* Returns express flag. If it is true, the message is not batched to reduce the latency.
	*/
	fun express(): Boolean {
	return getExpressViaJNI(qos);
	}
	companion object {
	/**
	* Returns default QoS settings.
	*/
	fun default(): QoS {
	return QoS(getDefaultViaJNI())
	}
	private external fun getDefaultViaJNI(): Byte
	}
	private external fun getPriorityViaJNI(_qos: Byte): Int
	private external fun getCongestionControlViaJNI(_qos: Byte): Int
	private external fun getExpressViaJNI(_qos:Byte): Boolean
	}
	/**
	* Quality of service settings used to send zenoh message.
	*/
	class QoS internal constructor(private val jniQoS: JNIQoS) {
	internal constructor(qos: Byte): this(JNIQoS(qos))
	/**
	* Returns priority of the message.
	*/
	fun priority(): Priority = jniQoS.getPriority()
	/**
	* Returns congestion control setting of the message.
	*/
	fun congestionControl(): CongestionControl = jniQoS.getCongestionControl()
	/**
	* Returns express flag. If it is true, the message is not batched to reduce the latency.
	*/
	fun express(): Boolean = jniQoS.getExpress()
	companion object {
	/**
	* Returns default QoS settings.
	*/
	fun default(): QoS {
	return QoS(JNIQoS())
	}
	}
	}

and where on the JNIQoS class contained within the jni package you'd have something like:

internal class JNIQoS internal constructor(private val qos: Byte) {

    internal constructor(): this(getDefaultQoSViaJNI())

    fun getExpress(): Boolean {
        return getExpressViaJNI(qos)
    }

    fun getCongestionControl(): CongestionControl {
        return CongestionControl.fromInt(getCongestionControlViaJNI(qos))
    }

    fun getPriority(): Priority {
        return Priority.fromInt(getPriorityViaJNI(qos))
    }

    private external fun getDefaultQoSViaJNI(): Byte
    private external fun getPriorityViaJNI(_qos: Byte): Int
    private external fun getCongestionControlViaJNI(_qos: Byte): Int
    private external fun getExpressViaJNI(_qos:Byte): Boolean
}

[DenisBiryukov91]

Done

[DariusIMP]

Here you can add a default value, in order to not needing to call QoS.default() wherever you create a new sample.

Suggested change

	val qos: QoS,
	val qos: QoS = QoS.default(),

[DenisBiryukov91]

The issues is, there is no really default value of qos for sample, since it would depend on the context where sample is used (either in subscribe, or query.reply). It is to be addressed later in the sample rework.

[DariusIMP]

Ack.

[DariusIMP]

LGTM

[DariusIMP]

Sorry I'm back, just a bit of nitpicking, you don't need a function to return a private attribute the java way, just declare jniQoS as internal, and then instead of calling sample.qos.jni().qos call sample.qos.jniQoS.qos, just to avoid boilerplate code.
Also, can you add spaces between the functions and their kdoc comments? And newlines at the end of files that have them missing? That'd be nice. Besides that, LGTM.