content: package act.app;
  
  /*-
   * #%L
   * ACT Framework
   * %%
   * Copyright (C) 2014 - 2017 ActFramework
   * %%
   * 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.
   * #L%
   */
  
  import org.joda.time.DateTime;
  
  import java.util.Map;
  
  /**
   * A daemon encapsulate a long running logic that can be
   *
   * * {@link #start() started}
   * * {@link #stop() stopped}
   * * {@link #restart() restart}
   * * Check {@link #state() state}
   */
  public interface Daemon extends Runnable {
  
      enum State {
          STOPPING, STOPPED, STARTING, STARTED, ERROR, FATAL
      }
  
      /**
       * Start this daemon
       */
      void start();
  
      /**
       * Stop this daemon
       */
      void stop();
  
      /**
       * {@link #stop() stop} this daemon first and then {@link #start() start}
       */
      void restart();
  
      /**
       * Returns the {@link State state} of this daemon
       * @return the state
       */
      State state();
  
      /**
       * Returns the timestamp when last state transfer happening
       * @return the timestamp
       */
      DateTime timestamp();
  
      /**
       * Returns ID of the daemon logic
       * @return ID
       */
      String id();
  
      /**
       * Returns last error
       * @return the last error encountered
       */
      Exception lastError();
  
      /**
       * Returns the timestamp when last error happening
       * @return the timestamp
       */
      DateTime errorTimestamp();
  
      /**
       * Set an attribute to the daemon
       * @param key the attribute key
       * @param value attribute value
       */
      void setAttribute(String key, Object value);
  
      /**
       * Remove an attribute from a daemon
       * @param key the attribute key
       */
      void removeAttribute(String key);
  
      /**
       * Return the attribute set to the daemon
       * @param key the attribute key
       * @param <T> the gneric type of the attribute value
       * @return the attribute value
       */
      <T> T getAttribute(String key);
  
      /**
       * Returns all attributes set on this daemon
       * @return the attributes set on this daemon
       */
      Map<String, Object> getAttributes();
  }
  