/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.brooklyn.core.mgmt.internal;

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

import java.util.Collections;
import java.util.Map;

import org.apache.brooklyn.api.entity.Entity;
import org.apache.brooklyn.api.entity.Group;
import org.apache.brooklyn.api.mgmt.SubscriptionHandle;
import org.apache.brooklyn.api.mgmt.SubscriptionManager;
import org.apache.brooklyn.api.sensor.Sensor;
import org.apache.brooklyn.api.sensor.SensorEvent;
import org.apache.brooklyn.api.sensor.SensorEventListener;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.google.common.base.Objects;
import com.google.common.base.Predicate;

public abstract class AbstractSubscriptionManager implements SubscriptionManager {

    // TODO Perhaps could use guava's SynchronizedSetMultimap? But need to check its synchronization guarantees.
    //      That would replace the utils used for subscriptionsBySubscriber etc.
    
    @SuppressWarnings("unused")
    private static final Logger LOG = LoggerFactory.getLogger(AbstractSubscriptionManager.class);

    /** performs the actual subscription; should return the subscription parameter as the handle */
    protected abstract <T> SubscriptionHandle subscribe(Map<String, Object> flags, Subscription<T> s);
    /** performs the actual publishing -- ie distribution to subscriptions */
    @Override
    public abstract <T> void publish(final SensorEvent<T> event);

    public static class EntitySensorToken {
        Entity e;
        Sensor<?> s;
        String sName;
        public EntitySensorToken(Entity e, Sensor<?> s) {
            this.e = e;
            this.s = s;
            this.sName = (s == null) ? null : checkNotNull(s.getName(), "sensor must have non-null name: %s", s);
        }
        @Override
        public int hashCode() {
            return Objects.hashCode(e, sName);
        }
        @Override
        public boolean equals(Object obj) {
            if (this == obj) return true;
            if (!(obj instanceof EntitySensorToken)) return false;
            if (!Objects.equal(e, ((EntitySensorToken)obj).e)) return false;
            if (!Objects.equal(sName, ((EntitySensorToken)obj).sName)) return false;
            return true;
        }
        @Override
        public String toString() {
            return (e != null ? e.getId() :  "*")+":"+(s != null ? sName : "*");
        }
    }
    static Object makeEntitySensorToken(Entity e, Sensor<?> s) {
        return new EntitySensorToken(e, s);
    }
    static Object makeEntitySensorToken(SensorEvent<?> se) {
        return makeEntitySensorToken(se.getSource(), se.getSensor());
    }
    
    /** @see SubscriptionManager#subscribe(Map, Entity, Sensor, SensorEventListener) */
    @Override
    public final <T> SubscriptionHandle subscribe(Entity producer, Sensor<T> sensor, SensorEventListener<? super T> listener) {
        return subscribe(Collections.<String,Object>emptyMap(), producer, sensor, listener);
    }
 
    /**
     * This implementation handles the following flags, in addition to those described in the {@link SubscriptionManager}
     * interface:
     * <ul>
     * <li>subscriberExecutionManagerTag - a tag to pass to execution manager (without setting any execution semantics / TaskPreprocessor);
     *      if not supplied and there is a subscriber, this will be inferred from the subscriber and set up with SingleThreadedScheduler
     * <li>eventFilter - a Predicate&lt;SensorEvent&gt; instance to filter what events are delivered
     * </ul>
     * 
     * @see SubscriptionManager#subscribe(Map, Entity, Sensor, SensorEventListener)
     */
    @Override
    public final <T> SubscriptionHandle subscribe(Map<String, Object> flags, Entity producer, Sensor<T> sensor, SensorEventListener<? super T> listener) {
        return subscribe(flags, new Subscription<T>(producer, sensor, listener));
    }
        
    /** @see SubscriptionManager#subscribeToChildren(Map, Entity, Sensor, SensorEventListener) */
    @Override
    public final <T> SubscriptionHandle subscribeToChildren(Entity parent, Sensor<T> sensor, SensorEventListener<? super T> listener) {
        return subscribeToChildren(Collections.<String,Object>emptyMap(), parent, sensor, listener);
    }

    /** @see SubscriptionManager#subscribe(Map, Entity, Sensor, SensorEventListener) */
    @Override
    public final  <T> SubscriptionHandle subscribeToChildren(Map<String, Object> flags, final Entity parent, Sensor<T> sensor, SensorEventListener<? super T> listener) {
        Predicate<SensorEvent<T>> eventFilter = new Predicate<SensorEvent<T>>() {
            @Override
            public boolean apply(SensorEvent<T> input) {
                return parent != null && input.getSource() != null && parent.equals(input.getSource().getParent());
            }
        };
        flags.put("eventFilter", eventFilter);
        return subscribe(flags, null, sensor, listener);
    }

    /** @see SubscriptionManager#subscribeToChildren(Map, Entity, Sensor, SensorEventListener) */
    @Override
    public final <T> SubscriptionHandle subscribeToMembers(Group parent, Sensor<T> sensor, SensorEventListener<? super T> listener) {
        return subscribeToMembers(Collections.<String,Object>emptyMap(), parent, sensor, listener);
    }

    /** @see SubscriptionManager#subscribe(Map, Entity, Sensor, SensorEventListener) */
    @Override
    public final  <T> SubscriptionHandle subscribeToMembers(Map<String, Object> flags, final Group parent, Sensor<T> sensor, SensorEventListener<? super T> listener) {
        Predicate<SensorEvent<T>> eventFilter = new Predicate<SensorEvent<T>>() {
            @Override
            public boolean apply(SensorEvent<T> input) {
                return parent.getMembers().contains(input.getSource());
            }
        };
        flags.put("eventFilter", eventFilter);
        return subscribe(flags, null, sensor, listener);
    }

    protected <T> Object getSubscriber(Map<String, Object> flags, Subscription<T> s) {
        return s.subscriber!=null ? s.subscriber : flags.containsKey("subscriber") ? flags.remove("subscriber") : s.listener;
    }

}
