/*
    * 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.commons.vfs2.impl;
  
  import static org.junit.Assert.assertEquals;
  import static org.junit.Assert.assertTrue;
  
  import java.io.BufferedWriter;
  import java.io.File;
  import java.io.IOException;
  import java.nio.file.Files;
  import java.util.concurrent.atomic.AtomicLong;
  
  import org.apache.commons.vfs2.AbstractVfsTestCase;
  import org.apache.commons.vfs2.FileChangeEvent;
  import org.apache.commons.vfs2.FileListener;
  import org.apache.commons.vfs2.FileObject;
  import org.apache.commons.vfs2.FileSystemManager;
  import org.apache.commons.vfs2.VFS;
  import org.junit.After;
  import org.junit.Before;
  import org.junit.BeforeClass;
  import org.junit.Ignore;
  import org.junit.Test;
  
  /**
   * Tests {@link DefaultFileMonitor}.
   */
  public class DefaultFileMonitorTest {
  
      private static class CountingListener implements FileListener {
          private final AtomicLong created = new AtomicLong();
          private final AtomicLong changed = new AtomicLong();
          private final AtomicLong deleted = new AtomicLong();
  
          @Override
          public void fileChanged(final FileChangeEvent event) {
              changed.incrementAndGet();
          }
  
          @Override
          public void fileCreated(final FileChangeEvent event) {
              created.incrementAndGet();
          }
  
          @Override
          public void fileDeleted(final FileChangeEvent event) {
              deleted.incrementAndGet();
          }
      }
  
      private enum Status {
          CHANGED, DELETED, CREATED
      }
  
      private class TestFileListener implements FileListener {
          @Override
          public void fileChanged(final FileChangeEvent event) throws Exception {
              status = Status.CHANGED;
          }
  
          @Override
          public void fileCreated(final FileChangeEvent event) throws Exception {
              status = Status.CREATED;
          }
  
          @Override
          public void fileDeleted(final FileChangeEvent event) throws Exception {
              status = Status.DELETED;
          }
      }
  
      private static final int DELAY_MILLIS = 100;
  
      private FileSystemManager fileSystemManager;
  
      private File testDir;
  
      private volatile Status status;
  
      private File testFile;
  
      private void deleteTestFileIfPresent() {
          if (testFile != null && testFile.exists()) {
              final boolean deleted = testFile.delete();
             assertTrue(testFile.toString(), deleted);
         }
     }
 
     /**
      * VFS-299: Handlers are not removed. One instance is {@link DefaultFileMonitor#removeFile(FileObject)}.
      *
      * As a result, the file monitor will fire two created events.
      */
     @Ignore("VFS-299")
     @Test
     public void ignore_testAddRemove() throws Exception {
         try (final FileObject fileObject = fileSystemManager.resolveFile(testFile.toURI().toString())) {
             final CountingListener listener = new CountingListener();
             final DefaultFileMonitor monitor = new DefaultFileMonitor(listener);
             monitor.setDelay(DELAY_MILLIS);
             try {
                 monitor.addFile(fileObject);
                 monitor.removeFile(fileObject);
                 monitor.addFile(fileObject);
                 monitor.start();
                 writeToFile(testFile);
                 Thread.sleep(DELAY_MILLIS * 3);
                 assertEquals("Created event is only fired once", 1, listener.created.get());
             } finally {
                 monitor.stop();
             }
         }
     }
 
     /**
      * VFS-299: Handlers are not removed. There is no API for properly decommissioning a file monitor.
      *
      * As a result, listeners of stopped monitors still receive events.
      */
     @Ignore("VFS-299")
     @Test
     public void ignore_testStartStop() throws Exception {
         try (final FileObject fileObject = fileSystemManager.resolveFile(testFile.toURI().toString())) {
             final CountingListener stoppedListener = new CountingListener();
             final DefaultFileMonitor stoppedMonitor = new DefaultFileMonitor(stoppedListener);
             stoppedMonitor.start();
             try {
                 stoppedMonitor.addFile(fileObject);
             } finally {
                 stoppedMonitor.stop();
             }
 
             // Variant 1: it becomes documented behavior to manually remove all files after stop() such that all
             // listeners
             // are removed
             // This currently does not work, see DefaultFileMonitorTests#testAddRemove above.
             // stoppedMonitor.removeFile(file);
 
             // Variant 2: change behavior of stop(), which then removes all handlers.
             // This would remove the possibility to pause watching files. Resuming watching for the same files via
             // start();
             // stop(); start(); would not work.
 
             // Variant 3: introduce new method DefaultFileMonitor#close which definitely removes all resources held by
             // DefaultFileMonitor.
 
             final CountingListener activeListener = new CountingListener();
             final DefaultFileMonitor activeMonitor = new DefaultFileMonitor(activeListener);
             activeMonitor.setDelay(DELAY_MILLIS);
             activeMonitor.addFile(fileObject);
             activeMonitor.start();
             try {
                 writeToFile(testFile);
                 Thread.sleep(DELAY_MILLIS * 10);
 
                 assertEquals("The listener of the active monitor received one created event", 1, activeListener.created.get());
                 assertEquals("The listener of the stopped monitor received no events", 0, stoppedListener.created.get());
             } finally {
                 activeMonitor.stop();
             }
         }
     }
 
     @Before
     public void setUp() throws Exception {
         fileSystemManager = VFS.getManager();
         testDir = AbstractVfsTestCase.getTestDirectoryFile();
         status = null;
         testFile = new File(testDir, "testReload.properties");
         deleteTestFileIfPresent();
     }
 
     @After
     public void tearDown() {
         // fileSystemManager.close();
         deleteTestFileIfPresent();
     }
 
     @Test
     public void testChildFileDeletedWithoutRecursiveChecking() throws Exception {
         writeToFile(testFile);
         try (final FileObject fileObject = fileSystemManager.resolveFile(testDir.toURI().toURL().toString())) {
             final DefaultFileMonitor monitor = new DefaultFileMonitor(new TestFileListener());
             monitor.setDelay(2000);
             monitor.setRecursive(false);
             monitor.addFile(fileObject);
             monitor.start();
             try {
                 status = null;
                 Thread.sleep(DELAY_MILLIS * 5);
                 testFile.delete();
                 Thread.sleep(DELAY_MILLIS * 30);
                 assertEquals("Event should not have occurred", null, status);
             } finally {
                 monitor.stop();
             }
         }
     }
 
     @Test
     public void testChildFileRecreated() throws Exception {
         writeToFile(testFile);
         try (final FileObject fileObj = fileSystemManager.resolveFile(testDir.toURI().toURL().toString())) {
             final DefaultFileMonitor monitor = new DefaultFileMonitor(new TestFileListener());
             monitor.setDelay(2000);
             monitor.setRecursive(true);
             monitor.addFile(fileObj);
             monitor.start();
             try {
                 status = null;
                 Thread.sleep(DELAY_MILLIS * 5);
                 testFile.delete();
                 waitFor(Status.DELETED, DELAY_MILLIS * 30);
                 status = null;
                 Thread.sleep(DELAY_MILLIS * 5);
                 writeToFile(testFile);
                 waitFor(Status.CREATED, DELAY_MILLIS * 30);
             } finally {
                 monitor.stop();
             }
         }
     }
 
     @Test
     public void testFileCreated() throws Exception {
         try (final FileObject fileObject = fileSystemManager.resolveFile(testFile.toURI().toURL().toString())) {
             final DefaultFileMonitor monitor = new DefaultFileMonitor(new TestFileListener());
             // TestFileListener manipulates status
             monitor.setDelay(DELAY_MILLIS);
             monitor.addFile(fileObject);
             monitor.start();
             try {
                 writeToFile(testFile);
                 Thread.sleep(DELAY_MILLIS * 5);
                 waitFor(Status.CREATED, DELAY_MILLIS * 5);
             } finally {
                 monitor.stop();
             }
         }
     }
 
     @Test
     public void testFileDeleted() throws Exception {
         writeToFile(testFile);
         try (final FileObject fileObject = fileSystemManager.resolveFile(testFile.toURI().toString())) {
             final DefaultFileMonitor monitor = new DefaultFileMonitor(new TestFileListener());
             // TestFileListener manipulates status
             monitor.setDelay(DELAY_MILLIS);
             monitor.addFile(fileObject);
             monitor.start();
             try {
                 testFile.delete();
                 waitFor(Status.DELETED, DELAY_MILLIS * 5);
             } finally {
                 monitor.stop();
             }
         }
     }
 
     @Test
     public void testFileModified() throws Exception {
         writeToFile(testFile);
         try (final FileObject fileObject = fileSystemManager.resolveFile(testFile.toURI().toURL().toString())) {
             final DefaultFileMonitor monitor = new DefaultFileMonitor(new TestFileListener());
             // TestFileListener manipulates status
             monitor.setDelay(DELAY_MILLIS);
             monitor.addFile(fileObject);
             monitor.start();
             try {
                 // Need a long delay to insure the new timestamp doesn't truncate to be the same as
                 // the current timestammp. Java only guarantees the timestamp will be to 1 second.
                 Thread.sleep(DELAY_MILLIS * 10);
                 final long valueMillis = System.currentTimeMillis();
                 final boolean rcMillis = testFile.setLastModified(valueMillis);
                 assertTrue("setLastModified succeeded", rcMillis);
                 waitFor(Status.CHANGED, DELAY_MILLIS * 5);
             } finally {
                 monitor.stop();
             }
         }
     }
 
     @Test
     public void testFileMonitorRestarted() throws Exception {
         try (final FileObject fileObject = fileSystemManager.resolveFile(testFile.toURI().toString())) {
             final DefaultFileMonitor monitor = new DefaultFileMonitor(new TestFileListener());
             // TestFileListener manipulates status
             monitor.setDelay(DELAY_MILLIS);
             monitor.addFile(fileObject);
 
             monitor.start();
             try {
                 writeToFile(testFile);
                 Thread.sleep(DELAY_MILLIS * 5);
             } finally {
                 monitor.stop();
             }
 
             monitor.start();
             try {
                 testFile.delete();
                 waitFor(Status.DELETED, DELAY_MILLIS * 5);
             } finally {
                 monitor.stop();
             }
         }
     }
 
     @Test
     public void testFileRecreated() throws Exception {
         try (final FileObject fileObject = fileSystemManager.resolveFile(testFile.toURI())) {
             final DefaultFileMonitor monitor = new DefaultFileMonitor(new TestFileListener());
             // TestFileListener manipulates status
             monitor.setDelay(DELAY_MILLIS);
             monitor.addFile(fileObject);
             monitor.start();
             try {
                 writeToFile(testFile);
                 waitFor(Status.CREATED, DELAY_MILLIS * 10);
                 status = null;
                 testFile.delete();
                 waitFor(Status.DELETED, DELAY_MILLIS * 10);
                 status = null;
                 Thread.sleep(DELAY_MILLIS * 5);
                 monitor.addFile(fileObject);
                 writeToFile(testFile);
                 waitFor(Status.CREATED, DELAY_MILLIS * 10);
             } finally {
                 monitor.stop();
             }
         }
     }
 
     private void waitFor(final Status expected, final long timeoutMillis) throws InterruptedException {
         if (expected == status) {
             return;
         }
         long remaining = timeoutMillis;
         final long interval = timeoutMillis / 10;
         while (remaining > 0) {
             Thread.sleep(interval);
             remaining -= interval;
             if (expected == status) {
                 return;
             }
         }
         assertTrue("No event occurred", status != null);
         assertEquals("Incorrect event " + status, expected, status);
     }
 
     private void writeToFile(final File file) throws IOException {
         // assertTrue(file.delete());
         try (final BufferedWriter out = Files.newBufferedWriter(file.toPath())) {
             out.write("string=value1");
         }
     }
 
 }