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//
// Copyright 2017 Charles W. Rapp
//
// 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.sf.eBus.client;

/**
 * Provides a common view of single- and multi-subject reply
 * feeds, allowing such feeds to be referenced in a common way.
 *
 * @author Charles W. Rapp
 */

public interface IEReplyFeed
    extends IEFeed
{
//---------------------------------------------------------------
// Member methods.
//

    /**
     * Returns {@code true} if this reply feed is both open and
     * advertised; otherwise, returns {@code false}.
     * @return {@code true} if this reply feed is open and
     * advertised
     */
    boolean isAdvertised();

    /**
     * Advertises this replier fed to the associated request
     * subject. If this feed is currently advertised to the
     * subject, then does nothing.
     * @throws IllegalStateException
     * if this feed is closed or if the client did not override
     * {@link EReplier} methods nor put the required callbacks in
     * place.
     *
     * @see #unadvertise()
     * @see #updateFeedState(EFeedState)
     * @see EFeed#close()
     */
    void advertise();

    /**
     * Retracts this replier feed advertisement. Does nothing if
     * this feed is not currently advertised.
     * @throws IllegalStateException
     * if this reply feed is closed.
     *
     * @see #advertise()
     * @see #close()
     */
    public void unadvertise();

    /**
     * Updates the replier feed state to the given value. If
     * {@code update} equals the currently stored reply feed
     * state, nothing is done. Otherwise, the updated value is
     * stored. If this feed is advertised to the server and
     * the subscription feed is up, then this update is forwarded
     * to subscribed requestors.
     * @param update the new reply feed state.
     * @throws NullPointerException
     * if {@code update} is {@code null}.
     * @throws IllegalStateException
     * if this feed was closed and is inactive or is not
     * advertised.
     */
    public void updateFeedState(final EFeedState update);
} // end of interface IEReplyFeed