/*

 * Copyright (c) 2014, 2021, 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 jdk.internal.jrtfs;

import java.io.IOException;

import java.net.URISyntaxException;

import java.net.URL;

import java.nio.file.Files;

import java.nio.file.FileSystem;

import java.nio.file.FileSystems;

import java.nio.file.FileSystemNotFoundException;

import java.nio.file.Path;

import java.nio.file.Paths;

import java.security.AccessController;

import java.security.CodeSource;

import java.security.PrivilegedAction;

import jdk.internal.jimage.ImageReader;

import jdk.internal.jimage.ImageReader.Node;

/**

 * @implNote This class needs to maintain JDK 8 source compatibility.

 *

 * It is used internally in the JDK to implement jimage/jrtfs access,

 * but also compiled and delivered as part of the jrtfs.jar to support access

 * to the jimage file provided by the shipped JDK by tools running on JDK 8.

 */

@SuppressWarnings("removal")

abstract class SystemImage {

    abstract Node findNode(String path) throws IOException;

    abstract byte[] getResource(Node node) throws IOException;

    abstract void close() throws IOException;

    static SystemImage open() throws IOException {

        if (modulesImageExists) {

            // open a .jimage and build directory structure

            final ImageReader image = ImageReader.open(moduleImageFile);

            image.getRootDirectory();

            return new SystemImage() {

                @Override

                Node findNode(String path) throws IOException {

                    return image.findNode(path);

                }

                @Override

                byte[] getResource(Node node) throws IOException {

                    return image.getResource(node);

                }

                @Override

                void close() throws IOException {

                    image.close();

                }

            };

        }

        if (Files.notExists(explodedModulesDir))

            throw new FileSystemNotFoundException(explodedModulesDir.toString());

        return new ExplodedImage(explodedModulesDir);

    }

    static final String RUNTIME_HOME;

    // "modules" jimage file Path

    static final Path moduleImageFile;

    // "modules" jimage exists or not?

    static final boolean modulesImageExists;

    // <JAVA_HOME>/modules directory Path

    static final Path explodedModulesDir;

    static {

        PrivilegedAction<String> pa = SystemImage::findHome;

        RUNTIME_HOME = AccessController.doPrivileged(pa);

        FileSystem fs = FileSystems.getDefault();

        moduleImageFile = fs.getPath(RUNTIME_HOME, "lib", "modules");

        explodedModulesDir = fs.getPath(RUNTIME_HOME, "modules");

        modulesImageExists = AccessController.doPrivileged(

            new PrivilegedAction<Boolean>() {

                @Override

                public Boolean run() {

                    return Files.isRegularFile(moduleImageFile);

                }

            });

    }

    /**

     * Returns the appropriate JDK home for this usage of the FileSystemProvider.

     * When the CodeSource is null (null loader) then jrt:/ is the current runtime,

     * otherwise the JDK home is located relative to jrt-fs.jar.

     */

    private static String findHome() {

        CodeSource cs = SystemImage.class.getProtectionDomain().getCodeSource();

        if (cs == null)

            return System.getProperty("java.home");

        // assume loaded from $TARGETJDK/lib/jrt-fs.jar

        URL url = cs.getLocation();

        if (!url.getProtocol().equalsIgnoreCase("file"))

            throw new InternalError(url + " loaded in unexpected way");

        try {

            Path lib = Paths.get(url.toURI()).getParent();

            if (!lib.getFileName().toString().equals("lib"))

                throw new InternalError(url + " unexpected path");

            return lib.getParent().toString();

        } catch (URISyntaxException e) {

            throw new InternalError(e);

        }

    }

}