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Platform-agnostic Java core for Nextop
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package io.nextop.client.node;
import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.Iterables;
import com.google.common.collect.ListMultimap;
import io.nextop.Id;
import io.nextop.Message;
import io.nextop.Route;
import io.nextop.client.*;
import io.nextop.log.Log;
import rx.Observable;
import rx.Scheduler;
import rx.Subscriber;
import rx.Subscription;
import rx.functions.Action0;
import rx.subscriptions.BooleanSubscription;
import rx.subscriptions.Subscriptions;
import javax.annotation.Nullable;
import java.util.ArrayList;
import java.util.List;
public class Head implements MessageControlNode {
public static Head create(MessageContext context, MessageControlState mcs, MessageControlNode downstream,
Scheduler callbackScheduler) {
return new Head(context, mcs, downstream, callbackScheduler);
}
final MessageContext context;
final MessageControlState mcs;
final MessageControlNode downstream;
// callbacks are called on this scheduler
// this is important for ordering, so that send, receive.subscribe from the callback thread
// are correctly subscribed in all cases (always call into the head on the callback thread to get this safety)
final Scheduler callbackScheduler;
final Scheduler.Worker callbackWorker;
final Object receiverMutex = new Object();
final ListMultimap receivers = ArrayListMultimap.create();
final List defaultReceivers = new ArrayList();
Head(MessageContext context, MessageControlState mcs, MessageControlNode downstream, Scheduler callbackScheduler) {
this.context = context;
this.mcs = mcs;
this.downstream = downstream;
this.callbackScheduler = callbackScheduler;
callbackWorker = callbackScheduler.createWorker();
}
/* threading notes:
* if calling from a thread that is not the callback thread,
* receive.subscribe ... send to ensure
* responses get delivered to the receiver.
* Calling send ... receive.subscribe needs to be done
* on the same execution of the callback thread
* to ensure responses get delivered to the receiver.
*/
/** thread-safe */
public void send(final Message message) {
mcs.notifyPending(message.id);
post(new Runnable() {
@Override
public void run() {
onMessageControl(MessageControl.send(message));
}
});
}
/** thread-safe */
public void complete(final Message message) {
mcs.notifyPending(message.id);
post(new Runnable() {
@Override
public void run() {
onMessageControl(MessageControl.send(MessageControl.Type.COMPLETE, message));
}
});
}
/** thread-safe */
public void error(final Message message) {
mcs.notifyPending(message.id);
post(new Runnable() {
@Override
public void run() {
onMessageControl(MessageControl.send(MessageControl.Type.ERROR, message));
}
});
}
/** thread-safe */
public void cancelSend(final Id id) {
post(new Runnable() {
@Override
public void run() {
onMessageControl(MessageControl.send(MessageControl.Type.ERROR, Message.outboxRoute(id)));
}
});
}
/** thread-safe */
public Observable receive(final Route route) {
return Observable.create(new Observable.OnSubscribe() {
@Override
public void call(final Subscriber subscriber) {
synchronized (receiverMutex) {
boolean s = receivers.put(route, subscriber);
assert s;
}
Subscription subscription = Subscriptions.create(new Action0() {
@Override
public void call() {
synchronized (receiverMutex) {
boolean s = receivers.remove(route, subscriber);
assert s;
}
}
});
subscriber.add(subscription);
assert !subscription.isUnsubscribed();
}
});
}
// when a listener is added, only new values are surfaced to it (old values are not surfaced)
/** thread-safe */
public Observable defaultReceive() {
return Observable.create(new Observable.OnSubscribe() {
@Override
public void call(final Subscriber subscriber) {
synchronized (receiverMutex) {
boolean s = defaultReceivers.add(subscriber);
assert s;
}
Subscription subscription = Subscriptions.create(new Action0() {
@Override
public void call() {
synchronized (receiverMutex) {
boolean s = defaultReceivers.remove(subscriber);
assert s;
}
}
});
subscriber.add(subscription);
assert !subscription.isUnsubscribed();
}
});
}
/** thread-safe */
public void init(final @Nullable Bundle savedState) {
post(new Runnable() {
@Override
public void run() {
init(null, savedState);
}
});
}
/** thread-safe */
public void start() {
post(new Runnable() {
@Override
public void run() {
onActive(true);
}
});
}
/** thread-safe */
public void stop() {
post(new Runnable() {
@Override
public void run() {
onActive(false);
}
});
}
/////// MessageControlNode IMPLEMENTATION ///////
@Override
public void init(@Nullable final MessageControlChannel upstream, @Nullable Bundle savedState) {
if (null != upstream) {
throw new IllegalArgumentException();
}
downstream.init(new MessageControlChannel() {
@Override
public MessageControlState getMessageControlState() {
return Head.this.getMessageControlState();
}
@Override
public void onActive(boolean active) {
/* ignore */
}
@Override
public void onMessageControl(final MessageControl mc) {
switch (mc.type) {
case MESSAGE: {
callbackWorker.schedule(new Action0() {
@Override
public void call() {
@Nullable Subscriber firstSubscriber;
synchronized (receiverMutex) {
firstSubscriber = Iterables.getFirst(
Iterables.concat(receivers.get(mc.message.route), defaultReceivers),
null);
}
if (null != firstSubscriber) {
firstSubscriber.onNext(mc.message);
}
}
});
break;
}
case COMPLETE: {
callbackWorker.schedule(new Action0() {
@Override
public void call() {
@Nullable Subscriber firstSubscriber;
synchronized (receiverMutex) {
firstSubscriber = Iterables.getFirst(receivers.get(mc.message.route), null);
}
if (null != firstSubscriber) {
firstSubscriber.onCompleted();
}
}
});
break;
}
case ERROR: {
callbackWorker.schedule(new Action0() {
@Override
public void call() {
@Nullable Subscriber firstSubscriber;
synchronized (receiverMutex) {
firstSubscriber = Iterables.getFirst(receivers.get(mc.message.route), null);
}
if (null != firstSubscriber) {
firstSubscriber.onError(new ReceiveException(mc.message));
}
}
});
break;
}
}
}
@Override
public void post(Runnable r) {
Head.this.post(r);
}
@Override
public void postDelayed(Runnable r, int delayMs) {
Head.this.postDelayed(r, delayMs);
}
@Override
public Scheduler getScheduler() {
return Head.this.getScheduler();
}
}, savedState);
}
@Override
public void onSaveState(Bundle savedState) {
downstream.onSaveState(savedState);
}
/////// MessageControlChannel IMPLEMENTATION ///////
public void onActive(boolean active) {
downstream.onActive(active);
}
public void onMessageControl(MessageControl mc) {
downstream.onMessageControl(mc);
}
@Override
public MessageControlState getMessageControlState() {
return mcs;
}
/////// MessageContext IMPLEMENTATION ///////
public void post(Runnable r) {
context.post(r);
}
public void postDelayed(Runnable r, int delayMs) {
context.postDelayed(r, delayMs);
}
public Scheduler getScheduler() {
return context.getScheduler();
}
public static final class ReceiveException extends Exception {
public final Message message;
private ReceiveException(Message message) {
this.message = message;
}
}
}