/**
* 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.jooby.internal.assets;
import static java.nio.file.LinkOption.NOFOLLOW_LINKS;
import static java.nio.file.StandardWatchEventKinds.ENTRY_CREATE;
import static java.nio.file.StandardWatchEventKinds.ENTRY_DELETE;
import static java.nio.file.StandardWatchEventKinds.ENTRY_MODIFY;
import static java.nio.file.StandardWatchEventKinds.OVERFLOW;
import java.io.File;
import java.io.IOException;
import java.nio.file.ClosedWatchServiceException;
import java.nio.file.FileSystems;
import java.nio.file.FileVisitResult;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.SimpleFileVisitor;
import java.nio.file.WatchEvent;
import java.nio.file.WatchEvent.Kind;
import java.nio.file.WatchKey;
import java.nio.file.WatchService;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.HashMap;
import java.util.Map;
import java.util.function.BiConsumer;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import com.sun.nio.file.SensitivityWatchEventModifier;
class Watcher {
/** The logging system. */
private final Logger log = LoggerFactory.getLogger(getClass());
private final WatchService watcher;
private volatile Map<WatchKey, Path> keys;
private BiConsumer<Kind<?>, Path> listener;
private Thread scanner;
@SuppressWarnings("unchecked")
static <T> WatchEvent<T> cast(final WatchEvent<?> event) {
return (WatchEvent<T>) event;
}
public void start() {
scanner.start();
}
public void stop() throws IOException {
watcher.close();
}
/**
* Register the given directory with the WatchService
*/
private void register(final Path dir) throws IOException {
WatchKey key = dir.register(watcher, new Kind[]{ENTRY_CREATE, ENTRY_DELETE, ENTRY_MODIFY },
SensitivityWatchEventModifier.HIGH);
keys.put(key, dir);
}
/**
* Register the given directory, and all its sub-directories, with the
* WatchService.
*/
private void registerAll(final Path start) throws IOException {
// register directory and sub-directories
Files.walkFileTree(start, new SimpleFileVisitor<Path>() {
@Override
public FileVisitResult preVisitDirectory(final Path dir, final BasicFileAttributes attrs)
throws IOException {
register(dir);
return FileVisitResult.CONTINUE;
}
});
}
public Watcher(final BiConsumer<Kind<?>, Path> listener, final Path... dirs)
throws IOException {
this.watcher = FileSystems.getDefault().newWatchService();
this.keys = new HashMap<WatchKey, Path>();
this.listener = listener;
for (Path dir : dirs) {
registerAll(dir);
}
this.scanner = new Thread(() -> {
boolean process = true;
listener.accept(ENTRY_MODIFY, dirs[0]);
try {
while (process) {
process = processEvents();
}
} catch (ClosedWatchServiceException ex) {
log.trace("watch service closed", ex);
}
}, "asset-compiler");
scanner.setDaemon(true);
}
private boolean processEvents() {
// wait for key to be signalled
WatchKey key;
try {
key = watcher.take();
} catch (InterruptedException x) {
return false;
}
Path dir = keys.get(key);
if (dir == null) {
return true;
}
for (WatchEvent<?> event : key.pollEvents()) {
Kind<?> kind = event.kind();
// TBD - provide example of how OVERFLOW event is handled
if (kind == OVERFLOW) {
continue;
}
// Context for directory entry event is the file name of entry
WatchEvent<Path> ev = cast(event);
Path name = ev.context();
Path child = dir.resolve(name);
File file = child.toFile();
if (file.isFile() || kind == ENTRY_DELETE) {
listener.accept(kind, dir.resolve(name));
}
// if directory is created, and watching recursively, then
// register it and its sub-directories
if (kind == ENTRY_CREATE) {
try {
if (Files.isDirectory(child, NOFOLLOW_LINKS)) {
registerAll(child);
}
} catch (IOException x) {
// ignore to keep sample readbale
}
}
}
// reset key and remove from set if directory no longer accessible
boolean valid = key.reset();
if (!valid) {
keys.remove(key);
// all directories are inaccessible
if (keys.isEmpty()) {
return false;
}
}
return true;
}
}