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elements-common
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/*
Copyright 2015-2019 Futeh Kao

Licensed 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 net.e6tech.elements.common.notification;

import net.e6tech.elements.common.subscribe.Broadcast;
import net.e6tech.elements.common.subscribe.Notice;
import net.e6tech.elements.common.subscribe.Subscriber;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.Executor;

/**
 * Created by futeh on 1/21/16.
 */
@SuppressWarnings({"unchecked", "squid:S1149"})
public class NotificationCenter implements Broadcast {

    private Map> srcNotificationListeners = new ConcurrentHashMap<>();
    private Map> notificationListeners = new ConcurrentHashMap<>();

    // for broadcasting
    Map> subscribers = new ConcurrentHashMap<>();
    List broadcasts = new CopyOnWriteArrayList<>();
    Executor executor = runnable -> new Thread(runnable).start();

    public Executor getExecutor() {
        return executor;
    }

    public void setExecutor(Executor executor) {
        this.executor = executor;
    }

    public void addSourceNotificationListener(Object src, NotificationListener listener) {
        List listeners = srcNotificationListeners.computeIfAbsent(src, n -> new CopyOnWriteArrayList<>());
        listeners.add(listener);
    }

    public void removeSourceNotificationListener(Object src, NotificationListener listener) {
        List listeners = srcNotificationListeners.computeIfAbsent(src, n -> new CopyOnWriteArrayList<>());
        listeners.remove(listener);
    }

    public  void addNotificationListener(Class cls, NotificationListener listener) {
        List listeners = notificationListeners.computeIfAbsent(cls, n -> new CopyOnWriteArrayList<>());
        listeners.add(listener);
    }

    public  void removeNotificationListener(Class cls, NotificationListener listener) {
        List listeners = notificationListeners.computeIfAbsent(cls, n -> new CopyOnWriteArrayList<>());
        listeners.remove(listener);
    }

    public void fireNotification(Notification notification) {
        if (notification.source() != null) {
            List listeners = srcNotificationListeners.get(notification.source());
            if (listeners != null) {
                listeners.forEach(listener -> listener.onEvent(notification));
            }
        }

        Class cls = notification.getClass();
        while (!cls.equals(Object.class)) {
            List listeners = notificationListeners.get(cls);
            if (listeners != null) {
                listeners.forEach(listener -> listener.onEvent(notification));
                break;
            }
            cls = cls.getSuperclass();
        }
    }

    public List getNotificationListeners(Notification notification) {
        List listeners = new ArrayList<>();
        if (notification.source() != null) {
            List list = srcNotificationListeners.get(notification.source());
            if (list != null)
                listeners.addAll(list);
        }
        List list = notificationListeners.get(notification.getClass());
        if (list != null)
            listeners.addAll(list);

        return list == null ? Collections.emptyList() : list;
    }

    // ***************************************************************************************
    // Broadcast
    // ***************************************************************************************
    @Override
    public void subscribe(String topic, Subscriber subscriber) {
        List list = subscribers.computeIfAbsent(topic, key -> new CopyOnWriteArrayList<>());
        synchronized (list) {
            list.add(subscriber);
        }
        for (Broadcast broadcast: broadcasts) {
            broadcast.subscribe(topic, subscriber);
        }
    }

    @Override
    public void unsubscribe(String topic, Subscriber subscriber) {
        List list = subscribers.computeIfAbsent(topic, key -> new CopyOnWriteArrayList<>());
        synchronized (list) {
            list.remove(subscriber);
        }

        for (Broadcast broadcast: broadcasts) {
            broadcast.unsubscribe(topic, subscriber);
        }
    }

    @Override
    public void publish(Notice notice) {
        for (Broadcast broadcast: broadcasts) {
            broadcast.publish(notice);
        }
    }

    public void addBroadcast(Broadcast broadcast) {
        broadcasts.add(broadcast);
        for (Map.Entry> entry : subscribers.entrySet()) {
            for (Subscriber subscriber : entry.getValue()) {
                broadcast.subscribe(entry.getKey(), subscriber);
            }
        }
    }

    public void removeBroadcast(Broadcast broadcast) {
        broadcasts.remove(broadcast);
        for (Map.Entry> entry : subscribers.entrySet()) {
            for (Subscriber subscriber : entry.getValue()) {
                broadcast.unsubscribe(entry.getKey(), subscriber);
            }
        }
    }

}