/*
    * Copyright (C) 2009 The Guava Authors
    *
    * 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 com.google.common.util.concurrent;
  
  import com.google.common.annotations.Beta;
  import com.google.common.base.Supplier;
  import com.google.common.base.Throwables;
  
  import java.util.concurrent.Executor;
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.TimeoutException;
  
  /**
   * Base class for services that do not need a thread while "running"
   * but may need one during startup and shutdown. Subclasses can
   * implement {@link #startUp} and {@link #shutDown} methods, each
   * which run in a executor which by default uses a separate thread
   * for each method.
   *
   * @author Chris Nokleberg
   * @since 1.0
   */
  @Beta
  public abstract class AbstractIdleService implements Service {
  
    /* Thread names will look like {@code "MyService STARTING"}. */
    private final Supplier<String> threadNameSupplier = new Supplier<String>() {
      @Override public String get() {
        return serviceName() + " " + state();
      }
    };
  
    /* use AbstractService for state management */
    private final Service delegate = new AbstractService() {
      @Override protected final void doStart() {
        MoreExecutors.renamingDecorator(executor(), threadNameSupplier)
            .execute(new Runnable() {
              @Override public void run() {
                try {
                  startUp();
                  notifyStarted();
                } catch (Throwable t) {
                  notifyFailed(t);
                  throw Throwables.propagate(t);
                }
              }
            });
      }
  
      @Override protected final void doStop() {
        MoreExecutors.renamingDecorator(executor(), threadNameSupplier)
            .execute(new Runnable() {
              @Override public void run() {
                try {
                  shutDown();
                  notifyStopped();
                } catch (Throwable t) {
                  notifyFailed(t);
                  throw Throwables.propagate(t);
                }
              }
            });
      }
    };
  
    /** Constructor for use by subclasses. */
    protected AbstractIdleService() {}
  
    /** Start the service. */
    protected abstract void startUp() throws Exception;
  
    /** Stop the service. */
    protected abstract void shutDown() throws Exception;
  
    /**
     * Returns the {@link Executor} that will be used to run this service.
     * Subclasses may override this method to use a custom {@link Executor}, which
     * may configure its worker thread with a specific name, thread group or
     * priority. The returned executor's {@link Executor#execute(Runnable)
     * execute()} method is called when this service is started and stopped,
     * and should return promptly.
     */
    protected Executor executor() {
      return new Executor() {
        @Override public void execute(Runnable command) {
         MoreExecutors.newThread(threadNameSupplier.get(), command).start();
       }
     };
   }
 
   @Override public String toString() {
     return serviceName() + " [" + state() + "]";
   }
 
   @Override public final boolean isRunning() {
     return delegate.isRunning();
   }
 
   @Override public final State state() {
     return delegate.state();
   }
 
   /**
    * @since 13.0
    */
   @Override public final void addListener(Listener listener, Executor executor) {
     delegate.addListener(listener, executor);
   }
   
   /**
    * @since 14.0
    */
   @Override public final Throwable failureCause() {
     return delegate.failureCause();
   }
   
   /**
    * @since 15.0
    */
   @Override public final Service startAsync() {
     delegate.startAsync();
     return this;
   }
   
   /**
    * @since 15.0
    */
   @Override public final Service stopAsync() {
     delegate.stopAsync();
     return this;
   }
   
   /**
    * @since 15.0
    */
   @Override public final void awaitRunning() {
     delegate.awaitRunning();
   }
   
   /**
    * @since 15.0
    */
   @Override public final void awaitRunning(long timeout, TimeUnit unit) throws TimeoutException {
     delegate.awaitRunning(timeout, unit);
   }
   
   /**
    * @since 15.0
    */
   @Override public final void awaitTerminated() {
     delegate.awaitTerminated();
   }
   
   /**
    * @since 15.0
    */
   @Override public final void awaitTerminated(long timeout, TimeUnit unit) throws TimeoutException {
     delegate.awaitTerminated(timeout, unit);
   }
   
   /**
    * Returns the name of this service. {@link AbstractIdleService} may include the name in debugging
    * output.
    *
    * @since 14.0
    */
   protected String serviceName() {
     return getClass().getSimpleName();
   }
 }