// 1. A session may update any existing topic. Update values must be of the same type as the topic being updated.

    // Add a topic first with a string type
    session.topics.add('foo', '').then(function() {
        // Update the topic
        return session.topics.update('foo', 'hello');
    }).then(function() {
        // Update the topic again
        return session.topics.update('foo', 'world');
    });

    // 2. If using RecordContent metadata, update values are constructed from the metadata

    // Create a new metadata instance
    var meta = new diffusion.metadata.RecordContent();

    meta.addRecord('record', 1, {
        'field' : meta.integer()
    });

    // Create a builder to set values
    var builder = meta.builder();

    builder.add('record', {
        field : 123
    });

    // Update the topic with the new value
    session.topics.add('topic', '').then(function() {
        session.topics.update('topic', builder.build());
    });

@import Diffusion;

@implementation TopicUpdateExample {
    PTDiffusionSession* _session;
}

-(void)startWithURL:(NSURL*)url {

    PTDiffusionCredentials *const credentials =
        [[PTDiffusionCredentials alloc] initWithPassword:@"password"];

    PTDiffusionSessionConfiguration *const sessionConfiguration =
        [[PTDiffusionSessionConfiguration alloc] initWithPrincipal:@"control"
                                                       credentials:credentials];

    NSLog(@"Connecting...");

    [PTDiffusionSession openWithURL:url
                      configuration:sessionConfiguration
                  completionHandler:^(PTDiffusionSession *session, NSError *error)
    {
        if (!session) {
            NSLog(@"Failed to open session: %@", error);
            return;
        }

        // At this point we now have a connected session.
        NSLog(@"Connected.");

        // Set ivar to maintain a strong reference to the session.
        _session = session;

        // Add topic.
        [self addTopicForSession:session];
    }];
}

static NSString *const _TopicPath = @"Example/Updating";

-(void)addTopicForSession:(PTDiffusionSession *const)session {
    // Add a single value topic without an initial value.
    [session.topicControl addWithTopicPath:_TopicPath
                                      type:PTDiffusionTopicType_SingleValue
                                     value:nil
                         completionHandler:^(NSError * _Nullable error)
    {
        if (error) {
            NSLog(@"Failed to add topic. Error: %@", error);
        } else {
            NSLog(@"Topic created.");

            // Update topic after a short wait.
            [self updateTopicForSession:session withValue:1];
        }
    }];
}

-(void)updateTopicForSession:(PTDiffusionSession *const)session
                   withValue:(const NSUInteger)value {
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(1.0 * NSEC_PER_SEC)),
        dispatch_get_main_queue(), ^
    {
        // Get the non-exclusive updater.
        PTDiffusionTopicUpdater *const updater = session.topicUpdateControl.updater;

        // Prepare data to update topic with.
        NSString *const string =
            [NSString stringWithFormat:@"Update #%lu", (unsigned long)value];
        NSData *const data = [string dataUsingEncoding:NSUTF8StringEncoding];
        PTDiffusionContent *const content =
            [[PTDiffusionContent alloc] initWithData:data];

        // Update the topic.
        [updater updateWithTopicPath:_TopicPath
                               value:content
                   completionHandler:^(NSError *const error)
        {
            if (error) {
                NSLog(@"Failed to update topic. Error: %@", error);
            } else {
                NSLog(@"Topic updated to \"%@\"", string);

                // Update topic after a short wait.
                [self updateTopicForSession:session withValue:value + 1];
            }
        }];
    });
}

@end

import com.pushtechnology.diffusion.client.Diffusion;
import com.pushtechnology.diffusion.client.callbacks.TopicTreeHandler;
import com.pushtechnology.diffusion.client.features.control.topics.TopicControl;
import com.pushtechnology.diffusion.client.features.control.topics.TopicControl.AddCallback;
import com.pushtechnology.diffusion.client.features.control.topics.TopicUpdateControl;
import com.pushtechnology.diffusion.client.features.control.topics.TopicUpdateControl.Updater.UpdateCallback;
import com.pushtechnology.diffusion.client.session.Session;
import com.pushtechnology.diffusion.client.topics.details.TopicType;

/**
 * An example of using a control client to create and update a topic in non
 * exclusive mode (as opposed to acting as an exclusive update source). In this
 * mode other clients could update the same topic (on a last update wins basis).
 * <P>
 * This uses the 'TopicControl' feature to create a topic and the
 * 'TopicUpdateControl' feature to send updates to it.
 * <P>
 * To send updates to a topic, the client session requires the 'update_topic'
 * permission for that branch of the topic tree.
 *
 * @author Push Technology Limited
 * @since 5.3
 */
public final class ControlClientUpdatingSingleValueTopic {

    private static final String TOPIC = "MyTopic";

    private final Session session;
    private final TopicControl topicControl;
    private final TopicUpdateControl updateControl;

    /**
     * Constructor.
     */
    public ControlClientUpdatingSingleValueTopic() {

        session =
            Diffusion.sessions().principal("control").password("password")
                .open("ws://diffusion.example.com:80");

        topicControl = session.feature(TopicControl.class);
        updateControl = session.feature(TopicUpdateControl.class);

        // Create the topic and request that it is removed when the session
        // closes
        topicControl.addTopic(
            TOPIC,
            TopicType.SINGLE_VALUE,
            new AddCallback.Default() {
                @Override
                public void onTopicAdded(String topicPath) {
                    topicControl.removeTopicsWithSession(
                        TOPIC,
                        new TopicTreeHandler.Default());
                }
            });

    }

    /**
     * Update the topic with a string value.
     *
     * @param value the update value
     * @param callback the update callback
     */
    public void update(String value, UpdateCallback callback) {
        updateControl.updater().update(TOPIC, value, callback);
    }

    /**
     * Close the session.
     */
    public void close() {
        session.close();
    }
}