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There is a newer version: 0.7.0-M1
package brooklyn.event.feed.function;

import static com.google.common.base.Preconditions.checkNotNull;

import java.util.List;
import java.util.Set;
import java.util.concurrent.Callable;
import java.util.concurrent.TimeUnit;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import brooklyn.entity.basic.EntityLocal;
import brooklyn.event.feed.AbstractFeed;
import brooklyn.event.feed.AttributePollHandler;
import brooklyn.event.feed.DelegatingPollHandler;
import brooklyn.event.feed.Poller;

import com.google.common.base.Objects;
import com.google.common.collect.HashMultimap;
import com.google.common.collect.Lists;
import com.google.common.collect.SetMultimap;
import com.google.common.collect.Sets;

/**
 * Provides a feed of attribute values, by periodically invoking functions.
 * 
 * Example usage (e.g. in an entity that extends SoftwareProcessImpl):
 *  * {@code
 * private FunctionFeed feed;
 * 
 * //@Override
 * protected void connectSensors() {
 *   super.connectSensors();
 *   
 *   feed = FunctionFeed.builder()
 *     .entity(this)
 *     .poll(new FunctionPollConfig(SERVICE_UP)
 *         .period(500, TimeUnit.MILLISECONDS)
 *         .callable(new Callable() {
 *             public Boolean call() throws Exception {
 *               return getDriver().isRunning();
 *             }
 *         })
 *         .onError(Functions.constant(Boolan.FALSE))
 *     .build();
 * }
 * 
 * {@literal @}Override
 * protected void disconnectSensors() {
 *   super.disconnectSensors();
 *   if (feed != null) feed.stop();
 * }
 * }
 * 
 * 
 * @author aled
 */
public class FunctionFeed extends AbstractFeed {

    private static final Logger log = LoggerFactory.getLogger(FunctionFeed.class);

    public static Builder builder() {
        return new Builder();
    }
    
    public static class Builder {
        private EntityLocal entity;
        private long period = 500;
        private TimeUnit periodUnits = TimeUnit.MILLISECONDS;
        private List> polls = Lists.newArrayList();
        private volatile boolean built;

        public Builder entity(EntityLocal val) {
            this.entity = val;
            return this;
        }
        public Builder period(long millis) {
            return period(millis, TimeUnit.MILLISECONDS);
        }
        public Builder period(long val, TimeUnit units) {
            this.period = val;
            this.periodUnits = units;
            return this;
        }
        public Builder poll(FunctionPollConfig config) {
            polls.add(config);
            return this;
        }
        public FunctionFeed build() {
            built = true;
            FunctionFeed result = new FunctionFeed(this);
            result.start();
            return result;
        }
        @Override
        protected void finalize() {
            if (!built) log.warn("FunctionFeed.Builder created, but build() never called");
        }
    }
    
    private static class FunctionPollIdentifier {
        final Callable job;

        private FunctionPollIdentifier(Callable job) {
            this.job = checkNotNull(job, "job");
        }

        @Override
        public int hashCode() {
            return Objects.hashCode(job);
        }
        
        @Override
        public boolean equals(Object other) {
            return (other instanceof FunctionPollIdentifier) && Objects.equal(job, ((FunctionPollIdentifier)other).job);
        }
    }
    
    // Treat as immutable once built
    private final SetMultimap> polls = HashMultimap.>create();
    
    protected FunctionFeed(Builder builder) {
        super(builder.entity);
        
        for (FunctionPollConfig config : builder.polls) {
            FunctionPollConfig configCopy = new FunctionPollConfig(config);
            if (configCopy.getPeriod() < 0) configCopy.period(builder.period, builder.periodUnits);
            Callable job = config.getCallable();
            polls.put(new FunctionPollIdentifier(job), configCopy);
        }
    }

    @Override
    protected void preStart() {
        for (final FunctionPollIdentifier pollInfo : polls.keySet()) {
            Set> configs = polls.get(pollInfo);
            long minPeriod = Integer.MAX_VALUE;
            Set> handlers = Sets.newLinkedHashSet();

            for (FunctionPollConfig config : configs) {
                handlers.add(new AttributePollHandler