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// Copyright 2015-2024 Nstream, inc.
//
// Licensed under the Redis Source Available License 2.0 (RSALv2) Agreement;
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://redis.com/legal/rsalv2-agreement/
//
// 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 nstream.adapter.common.egress;

import nstream.adapter.common.AdapterSettings;
import nstream.adapter.common.NstreamAgent;
import nstream.adapter.common.schedule.DeferrableException;
import swim.structure.Value;

/**
 * An abstract Web Agent that can push its state to an external process.
 * Requirements specific to the external process will be handled by the
 * implementing subclasses.
 * The {@link PublisherAgent} class encapsulates the settings object required to
 * configure publication and provides methods to load these settings.
 * 
 * Scheduling of asynchronous tasks can be achieved using the base
 * {@link NstreamAgent}.
 *
 * @param   the settings used to configure publication
 * @param   the type to be published externally
 */
public abstract class PublisherAgent extends NstreamAgent {

  protected S egressSettings;

  public PublisherAgent() {
  }

  /**
   * Get the settings agent property and load value as settings.
   *
   * @param propName agent property name of the settings
   * @see #loadSettings(Value)
   */
  protected final void loadSettings(String propName) {
    loadSettings(getProp(propName));
  }

  /**
   * Parse and set the settings {@link Value} from agent configuration.
   *
   * @param prop agent settings value to be loaded
   * @see #parseEgressSettings(Value)
   * @see #loadSettings(S)
   */
  protected final void loadSettings(Value prop) {
    loadSettings(parseEgressSettings(prop));
  }

  /**
   * Parse the agent settings {@link Value} and mold to a {@link S}
   * object.
   *
   * @param prop agent settings value to be parsed to {@link S}
   * @return settings object
   */
  protected abstract S parseEgressSettings(Value prop);

  /**
   * Set the settings that have been loaded from agent configuration.
   *
   * @param egressSettings settings loaded from agent configuration
   */
  protected void loadSettings(S egressSettings) {
    this.egressSettings = egressSettings;
  }

  /**
   * Publish a {@link Value} to an external process.
   * Will likely convert the {@link Value} object to {@link V} and
   * defer publishing to {@link PublisherAgent#publish(V)}.
   *
   * @param structure the state to be published
   * @throws DeferrableException an exception that will be handled without aborting publishing
   * @throws RuntimeException an exception that will abort publishing
   */
  protected abstract void publish(Value structure) throws DeferrableException;

  /**
   * Publish a {@link V} to an external process.
   *
   * @param publishable the state to be published
   * @throws DeferrableException an exception that will be handled without aborting publishing
   * @throws RuntimeException an exception that will abort publishing
   */
  protected abstract void publish(V publishable) throws DeferrableException;

  /**
   * Prepare the agent for publication.
   * Load settings object and schedule publishing as required.
   */
  protected abstract void stagePublication();

}