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rxjava2-backport developed by David Karnok
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/**
 * Copyright 2015 David Karnok and Netflix, Inc.
 * 
 * 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 hu.akarnokd.rxjava2.observables;

import org.reactivestreams.*;

import hu.akarnokd.rxjava2.Observable;
import hu.akarnokd.rxjava2.disposables.Disposable;
import hu.akarnokd.rxjava2.functions.Consumer;
import hu.akarnokd.rxjava2.internal.functions.Functions;
import hu.akarnokd.rxjava2.internal.operators.*;

/**
 * A {@code ConnectableObservable} resembles an ordinary {@link Observable}, except that it does not begin
 * emitting items when it is subscribed to, but only when its {@link #connect} method is called. In this way you
 * can wait for all intended {@link Subscriber}s to {@link Observable#subscribe} to the {@code Observable}
 * before the {@code Observable} begins emitting items.
 * 
 * 
 * 
 * @see RxJava Wiki:
 *      Connectable Observable Operators
 * @param 
 *          the type of items emitted by the {@code ConnectableObservable}
 */
public abstract class ConnectableObservable extends Observable {
    
    protected ConnectableObservable(Publisher onSubscribe) {
        super(onSubscribe);
    }
    
    /**
     * Instructs the {@code ConnectableObservable} to begin emitting the items from its underlying
     * {@link Observable} to its {@link Subscriber}s.
     *
     * @param connection
     *          the action that receives the connection subscription before the subscription to source happens
     *          allowing the caller to synchronously disconnect a synchronous source
     * @see ReactiveX documentation: Connect
     */
    public abstract void connect(Consumer connection);
    
    /**
     * Instructs the {@code ConnectableObservable} to begin emitting the items from its underlying
     * {@link Observable} to its {@link Subscriber}s.
     * 
     * To disconnect from a synchronous source, use the {@link #connect(hu.akarnokd.rxjava2.functions.Consumer)} method.
     *
     * @return the subscription representing the connection
     * @see ReactiveX documentation: Connect
     */
    public final Disposable connect() {
        final Disposable[] connection = new Disposable[1];
        connect(new Consumer() {
            @Override
            public void accept(Disposable d) {
                connection[0] = d;
            }
        });
        return connection[0];
    }

    /**
     * Returns an {@code Observable} that stays connected to this {@code ConnectableObservable} as long as there
     * is at least one subscription to this {@code ConnectableObservable}.
     * 
     * @return a {@link Observable}
     * @see ReactiveX documentation: RefCount
     */
    public Observable refCount() {
        return create(new PublisherRefCount(this));
    }

    /**
     * Returns an Observable that automatically connects to this ConnectableObservable
     * when the first Subscriber subscribes.
     * 
     * @return an Observable that automatically connects to this ConnectableObservable
     *         when the first Subscriber subscribes
     */
    public Observable autoConnect() {
        return autoConnect(1);
    }
    /**
     * Returns an Observable that automatically connects to this ConnectableObservable
     * when the specified number of Subscribers subscribe to it.
     * 
     * @param numberOfSubscribers the number of subscribers to await before calling connect
     *                            on the ConnectableObservable. A non-positive value indicates
     *                            an immediate connection.
     * @return an Observable that automatically connects to this ConnectableObservable
     *         when the specified number of Subscribers subscribe to it
     */
    public Observable autoConnect(int numberOfSubscribers) {
        return autoConnect(numberOfSubscribers, Functions.emptyConsumer());
    }
    
    /**
     * Returns an Observable that automatically connects to this ConnectableObservable
     * when the specified number of Subscribers subscribe to it and calls the 
     * specified callback with the Subscription associated with the established connection.
     * 
     * @param numberOfSubscribers the number of subscribers to await before calling connect
     *                            on the ConnectableObservable. A non-positive value indicates
     *                            an immediate connection.
     * @param connection the callback Action1 that will receive the Subscription representing the
     *                   established connection
     * @return an Observable that automatically connects to this ConnectableObservable
     *         when the specified number of Subscribers subscribe to it and calls the 
     *         specified callback with the Subscription associated with the established connection
     */
    public Observable autoConnect(int numberOfSubscribers, Consumer connection) {
        if (numberOfSubscribers <= 0) {
            this.connect(connection);
            return this;
        }
        return create(new PublisherAutoConnect(this, numberOfSubscribers, connection));
    }
}