content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you 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 org.apache.bookkeeper.common.component;
  
  /**
   * Lifecycle state. Allows the following transitions:
   *
   * <ul>
   * <li>INITIALIZED -&gt; STARTED, STOPPED, CLOSED</li>
   * <li>STARTED     -&gt; STOPPED</li>
   * <li>STOPPED     -&gt; STARTED, CLOSED</li>
   * <li>CLOSED      -&gt; </li>
   * </ul>
   *
   * <p>Also allows to stay in the same state. For example, when calling stop on a component, the
   * following logic can be applied:
   *
   * <pre>
   * public void stop() {
   *  if (!lifecycleState.moveToStopped()) {
   *      return;
   *  }
   * // continue with stop logic
   * }
   * </pre>
   *
   * <p>Note, closed is only allowed to be called when stopped, so make sure to stop the component first.
   * Here is how the logic can be applied:
   *
   * <pre>
   * public void close() {
   *  if (lifecycleState.started()) {
   *      stop();
   *  }
   *  if (!lifecycleState.moveToClosed()) {
   *      return;
   *  }
   *  // perform close logic here
   * }
   * </pre>
   */
  public class Lifecycle {
  
      /**
       * Lifecycle State.
       */
      public enum State {
          INITIALIZED,
          STOPPED,
          STARTED,
          CLOSED
      }
  
      private volatile State state = State.INITIALIZED;
  
      public State state() {
          return this.state;
      }
  
      /**
       * Returns <tt>true</tt> if the state is initialized.
       */
      public boolean initialized() {
          return state == State.INITIALIZED;
      }
  
      /**
       * Returns <tt>true</tt> if the state is started.
       */
      public boolean started() {
          return state == State.STARTED;
      }
  
      /**
       * Returns <tt>true</tt> if the state is stopped.
       */
      public boolean stopped() {
          return state == State.STOPPED;
      }
  
      /**
       * Returns <tt>true</tt> if the state is closed.
       */
      public boolean closed() {
          return state == State.CLOSED;
      }
  
      public boolean stoppedOrClosed() {
          Lifecycle.State state = this.state;
          return state == State.STOPPED || state == State.CLOSED;
      }
  
      public boolean canMoveToStarted() throws IllegalStateException {
          State localState = this.state;
          if (localState == State.INITIALIZED || localState == State.STOPPED) {
              return true;
          }
          if (localState == State.STARTED) {
              return false;
          }
          if (localState == State.CLOSED) {
              throw new IllegalStateException("Can't move to started state when closed");
          }
          throw new IllegalStateException("Can't move to started with unknown state");
      }
  
  
      public boolean moveToStarted() throws IllegalStateException {
          State localState = this.state;
          if (localState == State.INITIALIZED || localState == State.STOPPED) {
              state = State.STARTED;
              return true;
          }
          if (localState == State.STARTED) {
              return false;
          }
          if (localState == State.CLOSED) {
              throw new IllegalStateException("Can't move to started state when closed");
          }
          throw new IllegalStateException("Can't move to started with unknown state");
      }
  
      public boolean canMoveToStopped() throws IllegalStateException {
          State localState = state;
          if (localState == State.STARTED) {
              return true;
          }
          if (localState == State.INITIALIZED || localState == State.STOPPED) {
              return false;
          }
          if (localState == State.CLOSED) {
              throw new IllegalStateException("Can't move to stopped state when closed");
          }
          throw new IllegalStateException("Can't move to stopped with unknown state");
      }
  
      public boolean moveToStopped() throws IllegalStateException {
          State localState = state;
          if (localState == State.STARTED) {
              state = State.STOPPED;
              return true;
          }
          if (localState == State.INITIALIZED || localState == State.STOPPED) {
              return false;
          }
          if (localState == State.CLOSED) {
              throw new IllegalStateException("Can't move to stopped state when closed");
          }
          throw new IllegalStateException("Can't move to stopped with unknown state");
      }
  
      public boolean canMoveToClosed() throws IllegalStateException {
          State localState = state;
          if (localState == State.CLOSED) {
              return false;
          }
          if (localState == State.STARTED) {
              throw new IllegalStateException("Can't move to closed before moving to stopped mode");
          }
          return true;
      }
  
      public boolean moveToClosed() throws IllegalStateException {
          State localState = state;
          if (localState == State.CLOSED) {
              return false;
          }
          if (localState == State.STARTED) {
              throw new IllegalStateException("Can't move to closed before moving to stopped mode");
          }
          state = State.CLOSED;
          return true;
      }
  
      @Override
      public String toString() {
          return state.toString();
      }
  
  }
  