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.camel.component.stream;
  
  import java.io.File;
  import java.io.IOException;
  import java.nio.file.Path;
  import java.nio.file.WatchEvent;
  import java.nio.file.WatchKey;
  import java.nio.file.WatchService;
  import java.util.Locale;
  import java.util.concurrent.ExecutorService;
  import java.util.concurrent.TimeUnit;
  
  import org.apache.camel.CamelContext;
  import org.apache.camel.CamelContextAware;
  import org.apache.camel.RuntimeCamelException;
  import org.apache.camel.support.service.ServiceSupport;
  import org.apache.camel.util.IOHelper;
  import org.apache.camel.util.ObjectHelper;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import static java.nio.file.StandardWatchEventKinds.ENTRY_CREATE;
  import static java.nio.file.StandardWatchEventKinds.ENTRY_MODIFY;
  
  /**
   * To watch for file changes/rollover via JDK file watcher API. This is used to know for example of streaming from a
   * file, that gets rolled-over, so we know about this, and can begin reading the file again from the beginning.
   */
  public class FileWatcherStrategy extends ServiceSupport implements CamelContextAware {
  
      @FunctionalInterface
      public interface OnChangeEvent {
  
          void onChange(File file);
  
      }
  
      private static final Logger LOG = LoggerFactory.getLogger(FileWatcherStrategy.class);
      private CamelContext camelContext;
      private final String directory;
      private final OnChangeEvent onChangeEvent;
      private WatchService watcher;
      private ExecutorService executorService;
      private WatchFileChangesTask task;
      private long pollTimeout = 1000;
  
      public FileWatcherStrategy(String directory, OnChangeEvent onChangeEvent) {
          this.directory = directory;
          this.onChangeEvent = onChangeEvent;
      }
  
      @Override
      public CamelContext getCamelContext() {
          return camelContext;
      }
  
      @Override
      public void setCamelContext(CamelContext camelContext) {
          this.camelContext = camelContext;
      }
  
      public long getPollTimeout() {
          return pollTimeout;
      }
  
      /**
       * Sets the poll timeout in millis. The default value is 1000.
       */
      public void setPollTimeout(long pollTimeout) {
          this.pollTimeout = pollTimeout;
      }
  
      @Override
      protected void doStart() throws Exception {
          if (directory == null) {
              // no folder configured
              return;
          }
  
          File dir = new File(directory);
          if (dir.exists() && dir.isDirectory()) {
              LOG.info("Starting ReloadStrategy to watch directory: {}", dir);
  
              WatchEvent.Modifier modifier = null;
  
              // if its mac OSX then attempt to apply workaround or warn its slower
              String os = ObjectHelper.getSystemProperty("os.name", "");
              if (os.toLowerCase(Locale.US).startsWith("mac")) {
                  // this modifier can speedup the scanner on mac osx (as java on mac has no native file notification integration)
                  Class<WatchEvent.Modifier> clazz = getCamelContext().getClassResolver()
                          .resolveClass("com.sun.nio.file.SensitivityWatchEventModifier", WatchEvent.Modifier.class);
                  if (clazz != null) {
                      WatchEvent.Modifier[] modifiers = clazz.getEnumConstants();
                      for (WatchEvent.Modifier mod : modifiers) {
                          if ("HIGH".equals(mod.name())) {
                              modifier = mod;
                              break;
                          }
                      }
                  }
                  if (modifier != null) {
                      LOG.info(
                              "On Mac OS X the JDK WatchService is slow by default so enabling SensitivityWatchEventModifier.HIGH as workaround");
                  } else {
                      LOG.warn(
                              "On Mac OS X the JDK WatchService is slow and it may take up till 10 seconds to notice file changes");
                  }
              }
  
              try {
                  Path path = dir.toPath();
                  watcher = path.getFileSystem().newWatchService();
                  registerPathToWatcher(modifier, path, watcher);
  
                  task = new WatchFileChangesTask(watcher, path, onChangeEvent);
  
                  executorService
                          = getCamelContext().getExecutorServiceManager().newSingleThreadExecutor(this, "FileWatcherStrategy");
                  executorService.submit(task);
              } catch (IOException e) {
                  throw RuntimeCamelException.wrapRuntimeCamelException(e);
              }
          }
      }
  
      private WatchKey registerPathToWatcher(WatchEvent.Modifier modifier, Path path, WatchService watcher) throws IOException {
          WatchKey key;
          if (modifier != null) {
              key = path.register(watcher, new WatchEvent.Kind<?>[] { ENTRY_CREATE, ENTRY_MODIFY }, modifier);
          } else {
              key = path.register(watcher, ENTRY_CREATE, ENTRY_MODIFY);
          }
          return key;
      }
  
      @Override
      protected void doStop() throws Exception {
          if (executorService != null) {
              getCamelContext().getExecutorServiceManager().shutdownGraceful(executorService);
              executorService = null;
          }
          if (watcher != null) {
              IOHelper.close(watcher);
          }
      }
  
      /**
       * Background task which watches for file changes
       */
      protected class WatchFileChangesTask implements Runnable {
  
          private final WatchService watcher;
          private final Path folder;
          private volatile boolean running;
          private OnChangeEvent changeEvent;
  
          public WatchFileChangesTask(WatchService watcher, Path folder, OnChangeEvent changeEvent) {
              this.watcher = watcher;
              this.folder = folder;
              this.changeEvent = changeEvent;
          }
  
          public boolean isRunning() {
              return running;
          }
  
          @Override
          public void run() {
              LOG.debug("FileWatcherStrategy is starting watching folder: {}", folder);
  
              // allow to run while starting Camel
              while (isStarting() || isRunAllowed()) {
                  running = true;
  
                  WatchKey key;
                  try {
                      LOG.trace("FileWatcherStrategy is polling for file changes in directory: {}", folder);
                      // wait for a key to be available
                      key = watcher.poll(pollTimeout, TimeUnit.MILLISECONDS);
                  } catch (InterruptedException ex) {
                      Thread.currentThread().interrupt();
                      break;
                  }
  
                  if (key != null) {
  
                      for (WatchEvent<?> event : key.pollEvents()) {
                          WatchEvent<Path> we = (WatchEvent<Path>) event;
                          Path path = we.context();
                          File file = folder.resolve(path).toFile();
                          LOG.trace("Modified/Created/Deleted file: {}", file);
                          changeEvent.onChange(file);
                      }
  
                      // the key must be reset after processed
                      boolean valid = key.reset();
                      if (!valid) {
                          break;
                      }
                  }
              }
  
              running = false;
  
              LOG.info("FileWatcherStrategy is stopping watching folder: {}", folder);
          }
      }
  
  }
  