Copyright (c) 2017 Google, Inc and others.
This program and the accompanying materials
are made available under the terms of the Eclipse Public License 2.0
which accompanies this distribution, and is available at
https://www.eclipse.org/legal/epl-2.0/
SPDX-License-Identifier: EPL-2.0
Contributors:
  Stefan Xenos (Google) - Initial implementation
/*******************************************************************************
 * Copyright (c) 2017 Google, Inc and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *   Stefan Xenos (Google) - Initial implementation
 *******************************************************************************/
package org.eclipse.jdt.internal.core.nd.indexer;

import java.util.HashMap;
import java.util.Map;

import org.eclipse.jdt.internal.core.nd.Nd;

Holds a cache that maps filenames (absolute paths on the local filesystem) to "up to date" states.
A file is "up to date" if its content is known to be in sync with the index. A file
is not up to date if there is any possibility that its content might be out of sync with the
index.
/**
 * Holds a cache that maps filenames (absolute paths on the local filesystem) to "up to date" states.
 * A file is "up to date" if its content is known to be in sync with the index. A file
 * is not up to date if there is any possibility that its content might be out of sync with the
 * index.
 */
public class FileStateCache {
	private final Map<String, Boolean> fileStateCache = new HashMap<>();

	
Returns true if the file at the given path is in sync with the index. Returns false if the file has already
been tested and might be out-of-sync. Returns null if its status is unknown and needs to be tested.
Params:
location – an absolute path on the filesystem/**
	 * Returns true if the file at the given path is in sync with the index. Returns false if the file has already
	 * been tested and might be out-of-sync. Returns null if its status is unknown and needs to be tested.
	 *
	 * @param location an absolute path on the filesystem
	 */
	public Boolean isUpToDate(String location) {
		synchronized (this.fileStateCache) {
			return this.fileStateCache.get(location);
		}
	}

	
Returns the cache for the given Nd instance. 
Returns:
the cache for the given Nd. Creates one if it doesn't exist yet./**
	 * Returns the cache for the given {@link Nd} instance.
	 *
	 * @return the cache for the given {@link Nd}. Creates one if it doesn't exist yet.
	 */
	public static FileStateCache getCache(Nd nd) {
		return nd.getData(FileStateCache.class, FileStateCache::create);
	}

	
Creates a new instance of FileStateCache. /**
	 * Creates a new instance of {@link FileStateCache}.
	 */
	private static FileStateCache create() {
		return new FileStateCache();
	}

	
Inserts a new entry into the cache.
Params:
location – absolute filesystem path to the file
result – true if the file is definitely in sync with the index, false if there is any possibility of it
being out of sync./**
	 * Inserts a new entry into the cache.
	 * 
	 * @param location absolute filesystem path to the file
	 * @param result true if the file is definitely in sync with the index, false if there is any possibility of it
	 * being out of sync.
	 */
	public void put(String location, boolean result) {
		synchronized (this.fileStateCache) {
			this.fileStateCache.put(location, result);
		}
	}

	
Clears the entire cache.
/**
	 * Clears the entire cache.
	 */
	public void clear() {
		synchronized (this.fileStateCache) {
			this.fileStateCache.clear();
		}
	}

	
Removes a single entry from the cache.
Params:
location – absolute filesystem path to the file./**
	 * Removes a single entry from the cache.
	 * 
	 * @param location absolute filesystem path to the file.
	 */
	public void remove(String location) {
		synchronized (this.fileStateCache) {
			this.fileStateCache.remove(location);
		}
	}
}