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/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright (c) 2013-2014 sagyf Yang. The Four Group.
 */

package goja.core.libs.event;

import goja.core.libs.Promise;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.ListIterator;
import java.util.concurrent.ConcurrentLinkedQueue;

/**
 *  . 
 *
 * @author sagyf yang
 * @version 1.0 2014-09-11 13:25
 * @since JDK 1.6
 */
public class ArchivedEventStream {


    final int archiveSize;
    final ConcurrentLinkedQueue> events       = new ConcurrentLinkedQueue>();
    final List>                    waiting      = Collections.synchronizedList(new ArrayList>());
    final List>                   pipedStreams = new ArrayList>();

    public ArchivedEventStream(int archiveSize) {
        this.archiveSize = archiveSize;
    }

    public synchronized EventStream eventStream() {
        final EventStream stream = new EventStream(archiveSize);
        for (IndexedEvent event : events) {
            stream.publish(event.data);
        }
        pipedStreams.add(stream);
        return stream;
    }

    public synchronized Promise>> nextEvents(long lastEventSeen) {
        FilterTask filter = new FilterTask(lastEventSeen);
        waiting.add(filter);
        notifyNewEvent();
        return filter;
    }

    public synchronized List availableEvents(long lastEventSeen) {
        List result = new ArrayList();
        for (IndexedEvent event : events) {
            if (event.id > lastEventSeen) {
                result.add(event);
            }
        }
        return result;
    }

    public List archive() {
        List result = new ArrayList();
        for (IndexedEvent event : events) {
            result.add(event.data);
        }
        return result;
    }

    public synchronized void publish(T event) {
        if (events.size() >= archiveSize) {
            events.poll();
        }
        events.offer(new IndexedEvent(event));
        notifyNewEvent();
        for (EventStream eventStream : pipedStreams) {
            eventStream.publish(event);
        }
    }

    void notifyNewEvent() {
        for (ListIterator> it = waiting.listIterator(); it.hasNext(); ) {
            FilterTask filter = it.next();
            for (IndexedEvent event : events) {
                filter.propose(event);
            }
            if (filter.trigger()) {
                it.remove();
            }
        }
    }

    static class FilterTask extends Promise>> {

        final Long lastEventSeen;
        final List> newEvents = new ArrayList>();

        public FilterTask(Long lastEventSeen) {
            this.lastEventSeen = lastEventSeen;
        }

        public void propose(IndexedEvent event) {
            if (event.id > lastEventSeen) {
                newEvents.add(event);
            }
        }

        public boolean trigger() {
            if (newEvents.isEmpty()) {
                return false;
            }
            invoke(newEvents);
            return true;
        }
    }
}