/*
 * Copyright (c) 2005, 2014, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package com.sun.tools.javac.file;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.List;
import java.util.Optional;
import java.util.concurrent.ConcurrentHashMap;

import com.sun.tools.javac.util.Context;
import com.sun.tools.javac.util.Context.Factory;

Caching implementation of FSInfo.
This is NOT part of any supported API.
If you write code that depends on this, you do so at your own risk.
This code and its internal interfaces are subject to change or
deletion without notice.
/**
 * Caching implementation of FSInfo.
 *
 * <p><b>This is NOT part of any supported API.
 * If you write code that depends on this, you do so at your own risk.
 * This code and its internal interfaces are subject to change or
 * deletion without notice.</b>
 */
public class CacheFSInfo extends FSInfo {

    protected final ConcurrentHashMap<Path, Path> canonicalPathCache = new ConcurrentHashMap<>();
    protected final ConcurrentHashMap<Path, Optional<BasicFileAttributes>> attributeCache =
            new ConcurrentHashMap<>();
    protected final ConcurrentHashMap<Path, List<Path>> jarClassPathCache =
            new ConcurrentHashMap<>();

    
Register a Context.Factory to create a CacheFSInfo.
/**
     * Register a Context.Factory to create a CacheFSInfo.
     */
    public static void preRegister(Context context) {
        context.put(FSInfo.class, (Factory<FSInfo>)c -> {
                FSInfo instance = new CacheFSInfo();
                c.put(FSInfo.class, instance);
                return instance;
            });
    }

    public void clearCache() {
        canonicalPathCache.clear();
        attributeCache.clear();
        jarClassPathCache.clear();
    }

    @Override
    public Path getCanonicalFile(Path file) {
        return canonicalPathCache.computeIfAbsent(file, super::getCanonicalFile);
    }

    @Override
    public boolean exists(Path file) {
        return getAttributes(file).isPresent();
    }

    @Override
    public boolean isDirectory(Path file) {
        return getAttributes(file).map(BasicFileAttributes::isDirectory).orElse(false);
    }

    @Override
    public boolean isFile(Path file) {
        return getAttributes(file).map(BasicFileAttributes::isRegularFile).orElse(false);
    }

    @Override
    public List<Path> getJarClassPath(Path file) throws IOException {
        synchronized (jarClassPathCache) {
            List<Path> jarClassPath = jarClassPathCache.get(file);
            if (jarClassPath == null) {
                jarClassPath = super.getJarClassPath(file);
                jarClassPathCache.put(file, jarClassPath);
            }
            return jarClassPath;
        }
    }

    protected Optional<BasicFileAttributes> getAttributes(Path file) {
        return attributeCache.computeIfAbsent(file, this::maybeReadAttributes);
    }

    protected Optional<BasicFileAttributes> maybeReadAttributes(Path file) {
        try {
            return Optional.of(Files.readAttributes(file, BasicFileAttributes.class));
        } catch (IOException e) {
            // Ignore; means file not found
            return Optional.empty();
        }
    }
}