/*

 * 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.loader;

import java.io.IOException;

import java.io.InputStream;

import java.lang.module.ModuleReference;

import java.net.MalformedURLException;

import java.net.URI;

import java.net.URL;

import java.nio.file.Files;

import java.nio.file.Path;

import java.nio.file.Paths;

import java.security.AccessController;

import java.security.PrivilegedAction;

import java.util.Arrays;

import java.util.Enumeration;

import java.util.Optional;

import java.util.concurrent.ConcurrentHashMap;

import java.util.jar.JarInputStream;

import java.util.jar.Manifest;

import java.util.stream.Stream;

import jdk.internal.misc.JavaLangAccess;

import jdk.internal.misc.SharedSecrets;

import jdk.internal.module.ServicesCatalog;

/**

 * Find resources and packages in modules defined to the boot class loader or

 * resources and packages on the "boot class path" specified via -Xbootclasspath/a.

 */

public class BootLoader {

    private BootLoader() { }

    // The unnamed module for the boot loader

    private static final Module UNNAMED_MODULE;

    private static final String JAVA_HOME = System.getProperty("java.home");

    static {

        UNNAMED_MODULE = SharedSecrets.getJavaLangAccess().defineUnnamedModule(null);

        setBootLoaderUnnamedModule0(UNNAMED_MODULE);

    }

    // ServiceCatalog for the boot class loader

    private static final ServicesCatalog SERVICES_CATALOG = ServicesCatalog.create();

    // ClassLoaderValue map for boot class loader

    private static final ConcurrentHashMap<?, ?> CLASS_LOADER_VALUE_MAP

        = new ConcurrentHashMap<>();

    /**

     * Returns the unnamed module for the boot loader.

     */

    public static Module getUnnamedModule() {

        return UNNAMED_MODULE;

    }

    /**

     * Returns the ServiceCatalog for modules defined to the boot class loader.

     */

    public static ServicesCatalog getServicesCatalog() {

        return SERVICES_CATALOG;

    }

    /**

     * Returns the ClassLoaderValue map for the boot class loader.

     */

    public static ConcurrentHashMap<?, ?> getClassLoaderValueMap() {

        return CLASS_LOADER_VALUE_MAP;

    }

    /**

     * Returns {@code true} if there is a class path associated with the

     * BootLoader.

     */

    public static boolean hasClassPath() {

        return ClassLoaders.bootLoader().hasClassPath();

    }

    /**

     * Register a module with this class loader so that its classes (and

     * resources) become visible via this class loader.

     */

    public static void loadModule(ModuleReference mref) {

        ClassLoaders.bootLoader().loadModule(mref);

    }

    /**

     * Loads the Class object with the given name defined to the boot loader.

     */

    public static Class<?> loadClassOrNull(String name) {

        return ClassLoaders.bootLoader().loadClassOrNull(name);

    }

    /**

     * Loads the Class object with the given name in the given module

     * defined to the boot loader. Returns {@code null} if not found.

     */

    public static Class<?> loadClass(Module module, String name) {

        Class<?> c = loadClassOrNull(name);

        if (c != null && c.getModule() == module) {

            return c;

        } else {

            return null;

        }

    }

    /**

     * Returns a URL to a resource in a module defined to the boot loader.

     */

    public static URL findResource(String mn, String name) throws IOException {

        return ClassLoaders.bootLoader().findResource(mn, name);

    }

    /**

     * Returns an input stream to a resource in a module defined to the

     * boot loader.

     */

    public static InputStream findResourceAsStream(String mn, String name)

        throws IOException

    {

        return ClassLoaders.bootLoader().findResourceAsStream(mn, name);

    }

    /**

     * Returns the URL to the given resource in any of the modules

     * defined to the boot loader and the boot class path.

     */

    public static URL findResource(String name) {

        return ClassLoaders.bootLoader().findResource(name);

    }

    /**

     * Returns an Iterator to iterate over the resources of the given name

     * in any of the modules defined to the boot loader.

     */

    public static Enumeration<URL> findResources(String name) throws IOException {

        return ClassLoaders.bootLoader().findResources(name);

    }

    /**

     * Define a package for the given class to the boot loader, if not already

     * defined.

     */

    public static Package definePackage(Class<?> c) {

        return getDefinedPackage(c.getPackageName());

    }

    /**

     * Returns the Package of the given name defined to the boot loader or null

     * if the package has not been defined.

     */

    public static Package getDefinedPackage(String pn) {

        Package pkg = ClassLoaders.bootLoader().getDefinedPackage(pn);

        if (pkg == null) {

            String location = getSystemPackageLocation(pn.replace('.', '/'));

            if (location != null) {

                pkg = PackageHelper.definePackage(pn.intern(), location);

            }

        }

        return pkg;

    }

    /**

     * Returns a stream of the packages defined to the boot loader.

     */

    public static Stream<Package> packages() {

        return Arrays.stream(getSystemPackageNames())

                     .map(name -> getDefinedPackage(name.replace('/', '.')));

    }

    /**

     * Helper class to define {@code Package} objects for packages in modules

     * defined to the boot loader.

     */

    static class PackageHelper {

        private static final JavaLangAccess JLA = SharedSecrets.getJavaLangAccess();

        /**

         * Define the {@code Package} with the given name. The specified

         * location is a jrt URL to a named module in the run-time image,

         * a file URL to a module in an exploded run-time image, or a file

         * path to an entry on the boot class path (java agent Boot-Class-Path

         * or -Xbootclasspath/a.

         *

         * <p> If the given location is a JAR file containing a manifest,

         * the defined Package contains the versioning information from

         * the manifest, if present.

         *

         * @param name     package name

         * @param location location where the package is (jrt URL or file URL

         *                 for a named module in the run-time or exploded image;

         *                 a file path for a package from -Xbootclasspath/a)

         */

        static Package definePackage(String name, String location) {

            Module module = findModule(location);

            if (module != null) {

                // named module from runtime image or exploded module

                if (name.isEmpty())

                    throw new InternalError("empty package in " + location);

                return JLA.definePackage(ClassLoaders.bootLoader(), name, module);

            }

            // package in unnamed module (-Xbootclasspath/a)

            URL url = toFileURL(location);

            Manifest man = url != null ? getManifest(location) : null;

            return ClassLoaders.bootLoader().defineOrCheckPackage(name, man, url);

        }

        /**

         * Finds the module at the given location defined to the boot loader.

         * The module is either in runtime image or exploded image.

         * Otherwise this method returns null.

         */

        private static Module findModule(String location) {

            String mn = null;

            if (location.startsWith("jrt:/")) {

                // named module in runtime image ("jrt:/".length() == 5)

                mn = location.substring(5, location.length());

            } else if (location.startsWith("file:/")) {

                // named module in exploded image

                Path path = Paths.get(URI.create(location));

                Path modulesDir = Paths.get(JAVA_HOME, "modules");

                if (path.startsWith(modulesDir)) {

                    mn = path.getFileName().toString();

                }

            }

            if (mn != null) {

                // named module from runtime image or exploded module

                Optional<Module> om = ModuleLayer.boot().findModule(mn);

                if (!om.isPresent())

                    throw new InternalError(mn + " not in boot layer");

                return om.get();

            }

            return null;

        }

        /**

         * Returns URL if the given location is a regular file path.

         */

        private static URL toFileURL(String location) {

            return AccessController.doPrivileged(new PrivilegedAction<>() {

                public URL run() {

                    Path path = Paths.get(location);

                    if (Files.isRegularFile(path)) {

                        try {

                            return path.toUri().toURL();

                        } catch (MalformedURLException e) {}

                    }

                    return null;

                }

            });

        }

        /**

         * Returns the Manifest if the given location is a JAR file

         * containing a manifest.

         */

        private static Manifest getManifest(String location) {

            return AccessController.doPrivileged(new PrivilegedAction<>() {

                public Manifest run() {

                    Path jar = Paths.get(location);

                    try (InputStream in = Files.newInputStream(jar);

                         JarInputStream jis = new JarInputStream(in, false)) {

                        return jis.getManifest();

                    } catch (IOException e) {

                        return null;

                    }

                }

            });

        }

    }

    /**

     * Returns an array of the binary name of the packages defined by

     * the boot loader, in VM internal form (forward slashes instead of dot).

     */

    private static native String[] getSystemPackageNames();

    /**

     * Returns the location of the package of the given name, if

     * defined by the boot loader; otherwise {@code null} is returned.

     *

     * The location may be a module from the runtime image or exploded image,

     * or from the boot class append path (i.e. -Xbootclasspath/a or

     * BOOT-CLASS-PATH attribute specified in java agent).

     */

    private static native String getSystemPackageLocation(String name);

    private static native void setBootLoaderUnnamedModule0(Module module);

}