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Entity implementation classes, events, and other core elements

There is a newer version: 0.7.0-M1

package brooklyn.location.cloud;

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

import java.util.Collections;
import java.util.List;
import java.util.concurrent.atomic.AtomicReference;

import brooklyn.location.Location;
import brooklyn.management.ManagementContext;

import com.google.common.annotations.Beta;
import com.google.common.base.Predicate;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Lists;

@Beta
public abstract class AbstractAvailabilityZoneExtension implements AvailabilityZoneExtension {

    protected final ManagementContext managementContext;
    protected final AtomicReference> subLocations = new AtomicReference>();
    private final Object mutex = new Object();
    
    public AbstractAvailabilityZoneExtension(ManagementContext managementContext) {
        this.managementContext = checkNotNull(managementContext, "managementContext");
    }

    @Override
    public List getSubLocations(int max) {
        List all = getAllSubLocations();
        return all.subList(0, Math.min(max, all.size()));
    }

    @Override
    public List getSubLocationsByName(Predicate namePredicate, int max) {
        List result = Lists.newArrayList();
        List all = getAllSubLocations();
        for (Location loc : all) {
            if (isNameMatch(loc, namePredicate)) {
                result.add(loc);
            }
        }
        return Collections.unmodifiableList(result);
    }
    
    protected List getAllSubLocations() {
        synchronized (mutex) {
            if (subLocations.get() == null) {
                List result = doGetAllSubLocations();
                subLocations.set(ImmutableList.copyOf(result));
            }
        }
        return subLocations.get();
    }
    
    /**
     * Note called while holding mutex, so do not call code that will result in deadlock!
     * TODO: bad pattern, as this will likely call alien code (such as asking cloud provider?!)
     */
    protected abstract List doGetAllSubLocations();

    protected abstract boolean isNameMatch(Location loc, Predicate namePredicate);
}