/*

 * Copyright (c) 2016, 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

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 */

package jdk.internal.jrtfs;

import java.io.*;

import java.net.MalformedURLException;

import java.net.URL;

import java.net.URLClassLoader;

import java.nio.channels.*;

import java.nio.file.*;

import java.nio.file.DirectoryStream.Filter;

import java.nio.file.attribute.*;

import java.nio.file.spi.FileSystemProvider;

import java.net.URI;

import java.security.AccessController;

import java.security.PrivilegedAction;

import java.util.HashMap;

import java.util.Map;

import java.util.Objects;

import java.util.Set;

import java.util.concurrent.ExecutorService;

/**

 * File system provider for jrt file systems. Conditionally creates jrt fs on

 * .jimage file or exploded modules directory of underlying JDK.

 *

 * @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.

 */

public final class JrtFileSystemProvider extends FileSystemProvider {

    private volatile FileSystem theFileSystem;

    public JrtFileSystemProvider() {

    }

    @Override

    public String getScheme() {

        return "jrt";

    }

    /**

     * Need RuntimePermission "accessSystemModules" to create or get jrt:/

     */

    private void checkPermission() {

        @SuppressWarnings("removal")

        SecurityManager sm = System.getSecurityManager();

        if (sm != null) {

            RuntimePermission perm = new RuntimePermission("accessSystemModules");

            sm.checkPermission(perm);

        }

    }

    private void checkUri(URI uri) {

        if (!uri.getScheme().equalsIgnoreCase(getScheme())) {

            throw new IllegalArgumentException("URI does not match this provider");

        }

        if (uri.getAuthority() != null) {

            throw new IllegalArgumentException("Authority component present");

        }

        if (uri.getPath() == null) {

            throw new IllegalArgumentException("Path component is undefined");

        }

        if (!uri.getPath().equals("/")) {

            throw new IllegalArgumentException("Path component should be '/'");

        }

        if (uri.getQuery() != null) {

            throw new IllegalArgumentException("Query component present");

        }

        if (uri.getFragment() != null) {

            throw new IllegalArgumentException("Fragment component present");

        }

    }

    @Override

    public FileSystem newFileSystem(URI uri, Map<String, ?> env)

            throws IOException {

        Objects.requireNonNull(env);

        checkPermission();

        checkUri(uri);

        if (env.containsKey("java.home")) {

            return newFileSystem((String)env.get("java.home"), uri, env);

        } else {

            return new JrtFileSystem(this, env);

        }

    }

    private static final String JRT_FS_JAR = "jrt-fs.jar";

    private FileSystem newFileSystem(String targetHome, URI uri, Map<String, ?> env)

            throws IOException {

        Objects.requireNonNull(targetHome);

        Path jrtfs = FileSystems.getDefault().getPath(targetHome, "lib", JRT_FS_JAR);

        if (Files.notExists(jrtfs)) {

            throw new IOException(jrtfs.toString() + " not exist");

        }

        Map<String,?> newEnv = new HashMap<>(env);

        newEnv.remove("java.home");

        ClassLoader cl = newJrtFsLoader(jrtfs);

        try {

            Class<?> c = Class.forName(JrtFileSystemProvider.class.getName(), false, cl);

            @SuppressWarnings("deprecation")

            Object tmp = c.newInstance();

            return ((FileSystemProvider)tmp).newFileSystem(uri, newEnv);

        } catch (ClassNotFoundException |

                 IllegalAccessException |

                 InstantiationException e) {

            throw new IOException(e);

        }

    }

    private static class JrtFsLoader extends URLClassLoader {

        JrtFsLoader(URL[] urls) {

            super(urls);

        }

        @Override

        protected Class<?> loadClass(String cn, boolean resolve)

                throws ClassNotFoundException

        {

            Class<?> c = findLoadedClass(cn);

            if (c == null) {

                URL u = findResource(cn.replace('.', '/') + ".class");

                if (u != null) {

                    c = findClass(cn);

                } else {

                    return super.loadClass(cn, resolve);

                }

            }

            if (resolve)

                resolveClass(c);

            return c;

        }

    }

    @SuppressWarnings("removal")

    private static URLClassLoader newJrtFsLoader(Path jrtfs) {

        final URL url;

        try {

            url = jrtfs.toUri().toURL();

        } catch (MalformedURLException mue) {

            throw new IllegalArgumentException(mue);

        }

        final URL[] urls = new URL[] { url };

        return AccessController.doPrivileged(

                new PrivilegedAction<URLClassLoader>() {

                    @Override

                    public URLClassLoader run() {

                        return new JrtFsLoader(urls);

                    }

                }

        );

    }

    @Override

    public Path getPath(URI uri) {

        checkPermission();

        if (!uri.getScheme().equalsIgnoreCase(getScheme())) {

            throw new IllegalArgumentException("URI does not match this provider");

        }

        if (uri.getAuthority() != null) {

            throw new IllegalArgumentException("Authority component present");

        }

        if (uri.getQuery() != null) {

            throw new IllegalArgumentException("Query component present");

        }

        if (uri.getFragment() != null) {

            throw new IllegalArgumentException("Fragment component present");

        }

        String path = uri.getPath();

        if (path == null || path.charAt(0) != '/' || path.contains("..")) {

            throw new IllegalArgumentException("Invalid path component");

        }

        return getTheFileSystem().getPath("/modules" + path);

    }

    private FileSystem getTheFileSystem() {

        checkPermission();

        FileSystem fs = this.theFileSystem;

        if (fs == null) {

            synchronized (this) {

                fs = this.theFileSystem;

                if (fs == null) {

                    try {

                        this.theFileSystem = fs = new JrtFileSystem(this, null);

                    } catch (IOException ioe) {

                        throw new InternalError(ioe);

                    }

                }

            }

        }

        return fs;

    }

    @Override

    public FileSystem getFileSystem(URI uri) {

        checkPermission();

        checkUri(uri);

        return getTheFileSystem();

    }

    // Checks that the given file is a JrtPath

    static final JrtPath toJrtPath(Path path) {

        Objects.requireNonNull(path, "path");

        if (!(path instanceof JrtPath)) {

            throw new ProviderMismatchException();

        }

        return (JrtPath) path;

    }

    @Override

    public void checkAccess(Path path, AccessMode... modes) throws IOException {

        toJrtPath(path).checkAccess(modes);

    }

    @Override

    public Path readSymbolicLink(Path link) throws IOException {

        return toJrtPath(link).readSymbolicLink();

    }

    @Override

    public void copy(Path src, Path target, CopyOption... options)

            throws IOException {

        toJrtPath(src).copy(toJrtPath(target), options);

    }

    @Override

    public void createDirectory(Path path, FileAttribute<?>... attrs)

            throws IOException {

        toJrtPath(path).createDirectory(attrs);

    }

    @Override

    public final void delete(Path path) throws IOException {

        toJrtPath(path).delete();

    }

    @Override

    @SuppressWarnings("unchecked")

    public <V extends FileAttributeView> V

            getFileAttributeView(Path path, Class<V> type, LinkOption... options) {

        return JrtFileAttributeView.get(toJrtPath(path), type, options);

    }

    @Override

    public FileStore getFileStore(Path path) throws IOException {

        return toJrtPath(path).getFileStore();

    }

    @Override

    public boolean isHidden(Path path) {

        return toJrtPath(path).isHidden();

    }

    @Override

    public boolean isSameFile(Path path, Path other) throws IOException {

        return toJrtPath(path).isSameFile(other);

    }

    @Override

    public void move(Path src, Path target, CopyOption... options)

            throws IOException {

        toJrtPath(src).move(toJrtPath(target), options);

    }

    @Override

    public AsynchronousFileChannel newAsynchronousFileChannel(Path path,

            Set<? extends OpenOption> options,

            ExecutorService exec,

            FileAttribute<?>... attrs)

            throws IOException {

        throw new UnsupportedOperationException();

    }

    @Override

    public SeekableByteChannel newByteChannel(Path path,

            Set<? extends OpenOption> options,

            FileAttribute<?>... attrs)

            throws IOException {

        return toJrtPath(path).newByteChannel(options, attrs);

    }

    @Override

    public DirectoryStream<Path> newDirectoryStream(

            Path path, Filter<? super Path> filter) throws IOException {

        return toJrtPath(path).newDirectoryStream(filter);

    }

    @Override

    public FileChannel newFileChannel(Path path,

            Set<? extends OpenOption> options,

            FileAttribute<?>... attrs)

            throws IOException {

        return toJrtPath(path).newFileChannel(options, attrs);

    }

    @Override

    public InputStream newInputStream(Path path, OpenOption... options)

            throws IOException {

        return toJrtPath(path).newInputStream(options);

    }

    @Override

    public OutputStream newOutputStream(Path path, OpenOption... options)

            throws IOException {

        return toJrtPath(path).newOutputStream(options);

    }

    @Override

    @SuppressWarnings("unchecked") // Cast to A

    public <A extends BasicFileAttributes> A

            readAttributes(Path path, Class<A> type, LinkOption... options)

            throws IOException {

        if (type == BasicFileAttributes.class || type == JrtFileAttributes.class) {

            return (A) toJrtPath(path).getAttributes(options);

        }

        return null;

    }

    @Override

    public Map<String, Object>

            readAttributes(Path path, String attribute, LinkOption... options)

            throws IOException {

        return toJrtPath(path).readAttributes(attribute, options);

    }

    @Override

    public void setAttribute(Path path, String attribute,

            Object value, LinkOption... options)

            throws IOException {

        toJrtPath(path).setAttribute(attribute, value, options);

    }

}