/*

 * Copyright (c) 2015, 2016, 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.module;

import java.io.Closeable;

import java.io.File;

import java.io.IOError;

import java.io.IOException;

import java.io.InputStream;

import java.io.UncheckedIOException;

import java.lang.module.ModuleDescriptor;

import java.lang.module.ModuleReader;

import java.lang.module.ModuleReference;

import java.net.MalformedURLException;

import java.net.URI;

import java.net.URL;

import java.nio.ByteBuffer;

import java.nio.file.Files;

import java.nio.file.Path;

import java.nio.file.Paths;

import java.util.ArrayList;

import java.util.Collections;

import java.util.HashMap;

import java.util.HashSet;

import java.util.List;

import java.util.Map;

import java.util.Optional;

import java.util.Set;

import java.util.jar.JarEntry;

import java.util.jar.JarFile;

import jdk.internal.loader.Resource;

import jdk.internal.misc.JavaLangModuleAccess;

import jdk.internal.misc.SharedSecrets;

import sun.net.www.ParseUtil;

/**

 * Provides support for patching modules in the boot layer with -Xpatch.

 */

public final class ModulePatcher {

    private static final JavaLangModuleAccess JLMA

        = SharedSecrets.getJavaLangModuleAccess();

    // the prefix of the system properties that encode the value of -Xpatch

    private static final String PATCH_PROPERTY_PREFIX = "jdk.launcher.patch.";

    // module name -> sequence of patches (directories or JAR files)

    private static final Map<String, List<Path>> PATCH_MAP = decodeProperties();

    private ModulePatcher() { }

    /**

     * Decodes the values of -Xpatch options, returning a Map of module name to

     * list of file paths.

     *

     * @throws IllegalArgumentException if the the module name is missing or

     *         -Xpatch is used more than once to patch the same module

     */

    private static Map<String, List<Path>> decodeProperties() {

        int index = 0;

        String value = System.getProperty(PATCH_PROPERTY_PREFIX + index);

        if (value == null)

            return Collections.emptyMap();  // -Xpatch not specified

        Map<String, List<Path>> map = new HashMap<>();

        while (value != null) {

                throwIAE("Unable to parse: " + value);

            if (pos == 0)

                throwIAE("Missing module name: " + value);

                }

            }

            index++;

            value = System.getProperty(PATCH_PROPERTY_PREFIX + index);

        }

        return map;

    }

    /**

     * Returns a module reference that interposes on the given module if

     * needed. If there are no patches for the given module then the module

     * reference is simply returned. Otherwise the patches for the module

     * are scanned (to find any new concealed packages) and a new module

     * reference is returned.

     *

     * @throws UncheckedIOException if an I/O error is detected

     */

    public static ModuleReference interposeIfNeeded(ModuleReference mref) {

        ModuleDescriptor descriptor = mref.descriptor();

        String mn = descriptor.name();

        // if there are no patches for the module then nothing to do

        List<Path> paths = PATCH_MAP.get(mn);

        if (paths == null)

            return mref;

        // scan the JAR file or directory tree to get the set of packages

        Set<String> packages = new HashSet<>();

        try {

            for (Path file : paths) {

                if (Files.isRegularFile(file)) {

                    try (JarFile jf = new JarFile(file.toFile())) {

                        jf.stream()

                          .filter(e -> e.getName().endsWith(".class"))

                          .map(e -> toPackageName(file, e))

                          .filter(pn -> pn.length() > 0)

                          .forEach(packages::add);

                    }

                } else if (Files.isDirectory(file)) {

                    // exploded directory

                    Path top = file;

                    Files.find(top, Integer.MAX_VALUE,

                            ((path, attrs) -> attrs.isRegularFile() &&

                                    path.toString().endsWith(".class")))

                            .map(path -> toPackageName(top, path))

                            .filter(pn -> pn.length() > 0)

                            .forEach(packages::add);

                }

            }

        } catch (IOException ioe) {

            throw new UncheckedIOException(ioe);

        }

        // if there are new packages then we need a new ModuleDescriptor

        Set<String> original = descriptor.packages();

        packages.addAll(original);

        if (packages.size() > original.size()) {

            descriptor = JLMA.newModuleDescriptor(descriptor, packages);

        }

        URI location = mref.location().orElse(null);

    }

    /**

     * A ModuleReader that reads resources from a patched module.

     *

     * This class is public so as to expose the findResource method to the

     * built-in class loaders and avoid locating the resource twice during

     * class loading (once to locate the resource, the second to gets the

     * URL for the CodeSource).

     */

    public static class PatchedModuleReader implements ModuleReader {

        private final List<ResourceFinder> finders;

        private final ModuleReference mref;

        private final URL delegateCodeSourceURL;

        private volatile ModuleReader delegate;

        /**

         * Creates the ModuleReader to reads resources a patched module.

         */

        PatchedModuleReader(List<Path> patches, ModuleReference mref) {

            List<ResourceFinder> finders = new ArrayList<>();

            boolean initialized = false;

            try {

                for (Path file : patches) {

                    if (Files.isRegularFile(file)) {

                        finders.add(new JarResourceFinder(file));

                    } else {

                        finders.add(new ExplodedResourceFinder(file));

                    }

                }

                initialized = true;

            } catch (IOException ioe) {

                throw new UncheckedIOException(ioe);

            } finally {

                // close all ResourceFinder in the event of an error

                if (!initialized) closeAll(finders);

            }

            this.finders = finders;

            this.mref = mref;

            this.delegateCodeSourceURL = codeSourceURL(mref);

        }

        /**

         * Closes all resource finders.

         */

        private static void closeAll(List<ResourceFinder> finders) {

            for (ResourceFinder finder : finders) {

                try { finder.close(); } catch (IOException ioe) { }

            }

        }

        /**

         * Returns the code source URL for the given module.

         */

        private static URL codeSourceURL(ModuleReference mref) {

            try {

                Optional<URI> ouri = mref.location();

                if (ouri.isPresent())

                    return ouri.get().toURL();

            } catch (MalformedURLException e) { }

            return null;

        }

        /**

         * Returns the ModuleReader to delegate to when the resource is not

         * found in a patch location.

         */

        private ModuleReader delegate() throws IOException {

            ModuleReader r = delegate;

            if (r == null) {

                synchronized (this) {

                    r = delegate;

                    if (r == null) {

                        delegate = r = mref.open();

                    }

                }

            }

            return r;

        }

        /**

         * Finds a resources in the patch locations. Returns null if not found.

         */

        private Resource findResourceInPatch(String name) throws IOException {

            for (ResourceFinder finder : finders) {

                Resource r = finder.find(name);

                if (r != null)

                    return r;

            }

            return null;

        }

        /**

         * Finds a resource of the given name in the patched module.

         */

        public Resource findResource(String name) throws IOException {

            // patch locations

            Resource r = findResourceInPatch(name);

            if (r != null)

                return r;

            // original module

            ByteBuffer bb = delegate().read(name).orElse(null);

            if (bb == null)

                return null;

            return new Resource() {

                private <T> T shouldNotGetHere(Class<T> type) {

                    throw new InternalError("should not get here");

                }

                @Override

                public String getName() {

                    return shouldNotGetHere(String.class);

                }

                @Override

                public URL getURL() {

                    return shouldNotGetHere(URL.class);

                }

                @Override

                public URL getCodeSourceURL() {

                    return delegateCodeSourceURL;

                }

                @Override

                public ByteBuffer getByteBuffer() throws IOException {

                    return bb;

                }

                @Override

                public InputStream getInputStream() throws IOException {

                    return shouldNotGetHere(InputStream.class);

                }

                @Override

                public int getContentLength() throws IOException {

                    return shouldNotGetHere(int.class);

                }

            };

        }

        @Override

        public Optional<URI> find(String name) throws IOException {

            Resource r = findResourceInPatch(name);

            if (r != null) {

                URI uri = URI.create(r.getURL().toString());

                return Optional.of(uri);

            } else {

                return delegate().find(name);

            }

        }

        @Override

        public Optional<InputStream> open(String name) throws IOException {

            Resource r = findResourceInPatch(name);

            if (r != null) {

                return Optional.of(r.getInputStream());

            } else {

                return delegate().open(name);

            }

        }

        @Override

        public Optional<ByteBuffer> read(String name) throws IOException {

            Resource r = findResourceInPatch(name);

            if (r != null) {

                ByteBuffer bb = r.getByteBuffer();

                assert !bb.isDirect();

                return Optional.of(bb);

            } else {

                return delegate().read(name);

            }

        }

        @Override

        public void release(ByteBuffer bb) {

            if (bb.isDirect()) {

                try {

                    delegate().release(bb);

                } catch (IOException ioe) {

                    throw new InternalError(ioe);

                }

            }

        }

        @Override

        public void close() throws IOException {

            closeAll(finders);

            delegate().close();

        }

    }

    /**

     * A resource finder that find resources in a patch location.

     */

    private static interface ResourceFinder extends Closeable {

        Resource find(String name) throws IOException;

    }

    /**

     * A ResourceFinder that finds resources in a JAR file.

     */

    private static class JarResourceFinder implements ResourceFinder {

        private final JarFile jf;

        private final URL csURL;

        JarResourceFinder(Path path) throws IOException {

            this.jf = new JarFile(path.toFile());

            this.csURL = path.toUri().toURL();

        }

        @Override

        public void close() throws IOException {

            jf.close();

        }

        @Override

        public Resource find(String name) throws IOException {

            JarEntry entry = jf.getJarEntry(name);

            if (entry == null)

                return null;

            return new Resource() {

                @Override

                public String getName() {

                    return name;

                }

                @Override

                public URL getURL() {

                    String encodedPath = ParseUtil.encodePath(name, false);

                    try {

                        return new URL("jar:" + csURL + "!/" + encodedPath);

                    } catch (MalformedURLException e) {

                        return null;

                    }

                }

                @Override

                public URL getCodeSourceURL() {

                    return csURL;

                }

                @Override

                public ByteBuffer getByteBuffer() throws IOException {

                    byte[] bytes = getInputStream().readAllBytes();

                    return ByteBuffer.wrap(bytes);

                }

                @Override

                public InputStream getInputStream() throws IOException {

                    return jf.getInputStream(entry);

                }

                @Override

                public int getContentLength() throws IOException {

                    long size = entry.getSize();

                    return (size > Integer.MAX_VALUE) ? -1 : (int) size;

                }

            };

        }

    }

    /**

     * A ResourceFinder that finds resources on the file system.

     */

    private static class ExplodedResourceFinder implements ResourceFinder {

        private final Path dir;

        ExplodedResourceFinder(Path dir) {

            this.dir = dir;

        }

        @Override

        public void close() { }

        @Override

        public Resource find(String name) throws IOException {

            Path file = Paths.get(name.replace('/', File.separatorChar));

            if (file.getRoot() == null) {

                file = dir.resolve(file);

            } else {

                // drop the root component so that the resource is

                // located relative to the module directory

                int n = file.getNameCount();

                if (n == 0)

                    return null;

                file = dir.resolve(file.subpath(0, n));

            }

            if (Files.isRegularFile(file)) {

                return newResource(name, dir, file);

            } else {

                return null;

            }

        }

        private Resource newResource(String name, Path top, Path file) {

            return new Resource() {

                @Override

                public String getName() {

                    return name;

                }

                @Override

                public URL getURL() {

                    try {

                        return file.toUri().toURL();

                    } catch (IOException | IOError e) {

                        return null;

                    }

                }

                @Override

                public URL getCodeSourceURL() {

                    try {

                        return top.toUri().toURL();

                    } catch (IOException | IOError e) {

                        return null;

                    }

                }

                @Override

                public ByteBuffer getByteBuffer() throws IOException {

                    return ByteBuffer.wrap(Files.readAllBytes(file));

                }

                @Override

                public InputStream getInputStream() throws IOException {

                    return Files.newInputStream(file);

                }

                @Override

                public int getContentLength() throws IOException {

                    long size = Files.size(file);

                    return (size > Integer.MAX_VALUE) ? -1 : (int)size;

                }

            };

        }

    }

    /**