/*

 * 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.File;

import java.io.FilePermission;

import java.io.IOException;

import java.io.InputStream;

import java.lang.module.ModuleReference;

import java.lang.module.ModuleReader;

import java.net.MalformedURLException;

import java.net.URI;

import java.net.URL;

import java.nio.ByteBuffer;

import java.security.AccessController;

import java.security.CodeSigner;

import java.security.CodeSource;

import java.security.Permission;

import java.security.PermissionCollection;

import java.security.PrivilegedAction;

import java.security.PrivilegedActionException;

import java.security.PrivilegedExceptionAction;

import java.security.SecureClassLoader;

import java.util.ArrayList;

import java.util.Collections;

import java.util.Enumeration;

import java.util.List;

import java.util.Map;

import java.util.Optional;

import java.util.concurrent.ConcurrentHashMap;

import java.util.jar.Attributes;

import java.util.jar.Manifest;

import jdk.internal.module.ModulePatcher.PatchedModuleReader;

import jdk.internal.misc.VM;

/**

 * The platform or application class loader. Resources loaded from modules

 * defined to the boot class loader are also loaded via an instance of this

 * ClassLoader type.

 *

 * <p> This ClassLoader supports loading of classes and resources from modules.

 * Modules are defined to the ClassLoader by invoking the {@link #loadModule}

 * method. Defining a module to this ClassLoader has the effect of making the

 * types in the module visible. </p>

 *

 * <p> This ClassLoader also supports loading of classes and resources from a

 * class path of URLs that are specified to the ClassLoader at construction

 * time. The class path may expand at runtime (the Class-Path attribute in JAR

 * files or via instrumentation agents). </p>

 *

 * <p> The delegation model used by this ClassLoader differs to the regular

 * delegation model. When requested to load a class then this ClassLoader first

 * maps the class name to its package name. If there is a module defined to a

 * BuiltinClassLoader containing this package then the class loader delegates

 * directly to that class loader. If there isn't a module containing the

 * package then it delegates the search to the parent class loader and if not

 * found in the parent then it searches the class path. The main difference

 * between this and the usual delegation model is that it allows the platform

 * class loader to delegate to the application class loader, important with

 * upgraded modules defined to the platform class loader.

 */

public class BuiltinClassLoader

    extends SecureClassLoader

{

    static {

        if (!ClassLoader.registerAsParallelCapable())

            throw new InternalError();

    }

    // parent ClassLoader

    private final BuiltinClassLoader parent;

    // the URL class path or null if there is no class path

    private final URLClassPath ucp;

    /**

     * A module defined/loaded by a built-in class loader.

     *

     * A LoadedModule encapsulates a ModuleReference along with its CodeSource

     * URL to avoid needing to create this URL when define classes.

     */

    private static class LoadedModule {

        private final BuiltinClassLoader loader;

        private final ModuleReference mref;

        private final URL codeSourceURL;          // may be null

        LoadedModule(BuiltinClassLoader loader, ModuleReference mref) {

            URL url = null;

            if (mref.location().isPresent()) {

                try {

                    url = mref.location().get().toURL();

                } catch (MalformedURLException e) { }

            }

            this.loader = loader;

            this.mref = mref;

            this.codeSourceURL = url;

        }

        BuiltinClassLoader loader() { return loader; }

        ModuleReference mref() { return mref; }

        String name() { return mref.descriptor().name(); }

        URL codeSourceURL() { return codeSourceURL; }

    }

    // maps package name to loaded module for modules in the boot layer

    private static final Map<String, LoadedModule> packageToModule

        = new ConcurrentHashMap<>(1024);

    // maps a module name to a module reference

    private final Map<String, ModuleReference> nameToModule;

    // maps a module reference to a module reader

    private final Map<ModuleReference, ModuleReader> moduleToReader;

    /**

     * Create a new instance.

     */

    BuiltinClassLoader(BuiltinClassLoader parent, URLClassPath ucp) {

        // ensure getParent() returns null when the parent is the boot loader

        super(parent == null || parent == ClassLoaders.bootLoader() ? null : parent);

        this.parent = parent;

        this.ucp = ucp;

        this.nameToModule = new ConcurrentHashMap<>();

        this.moduleToReader = new ConcurrentHashMap<>();

    }

    /**

     * Register a module this this class loader. This has the effect of making

     * the types in the module visible.

     */

    public void loadModule(ModuleReference mref) {

        String mn = mref.descriptor().name();

        if (nameToModule.putIfAbsent(mn, mref) != null) {

            throw new InternalError(mn + " already defined to this loader");

        }

        LoadedModule loadedModule = new LoadedModule(this, mref);

        for (String pn : mref.descriptor().packages()) {

            LoadedModule other = packageToModule.putIfAbsent(pn, loadedModule);

            if (other != null) {

                throw new InternalError(pn + " in modules " + mn + " and "

                                        + other.mref().descriptor().name());

            }

        }

    }

    /**

     * Returns the {@code ModuleReference} for the named module defined to

     * this class loader; or {@code null} if not defined.

     *

     * @param name The name of the module to find

     */

    protected ModuleReference findModule(String name) {

        return nameToModule.get(name);

    }

    // -- finding resources

    /**

     * Returns a URL to a resource of the given name in a module defined to

     * this class loader.

     */

    @Override

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

        ModuleReference mref = nameToModule.get(mn);

        if (mref == null)

            return null;   // not defined to this class loader

        URL url;

        try {

            url = AccessController.doPrivileged(

                new PrivilegedExceptionAction<URL>() {

                    @Override

                    public URL run() throws IOException {

                        URI u = moduleReaderFor(mref).find(name).orElse(null);

                        if (u != null) {

                            try {

                                return u.toURL();

                            } catch (MalformedURLException e) { }

                        }

                        return null;

                    }

                });

        } catch (PrivilegedActionException pae) {

            throw (IOException) pae.getCause();

        }

        // check access to the URL

        return checkURL(url);

    }

    /**

     * Returns an input stream to a resource of the given name in a module

     * defined to this class loader.

     */

    public InputStream findResourceAsStream(String mn, String name)

        throws IOException

    {

        // Need URL to resource when running with a security manager so that

        // the right permission check is done.

        SecurityManager sm = System.getSecurityManager();

        if (sm != null) {

            URL url = findResource(mn, name);

            return (url != null) ? url.openStream() : null;

        } else {

            ModuleReference mref = nameToModule.get(mn);

            if (mref == null)

                return null;   // not defined to this class loader

            try {

                return AccessController.doPrivileged(

                    new PrivilegedExceptionAction<InputStream>() {

                        @Override

                        public InputStream run() throws IOException {

                            return moduleReaderFor(mref).open(name).orElse(null);

                        }

                    });

            } catch (PrivilegedActionException pae) {

                throw (IOException) pae.getCause();

            }

        }

    }

    /**

     * Finds the resource with the given name on the class path of this class

     * loader.

     */

    @Override

    public URL findResource(String name) {

        if (ucp != null) {

            PrivilegedAction<URL> pa = () -> ucp.findResource(name, false);

            URL url = AccessController.doPrivileged(pa);

            return checkURL(url);

        } else {

            return null;

        }

    }

    /**

     * Returns an enumeration of URL objects to all the resources with the

     * given name on the class path of this class loader.

     */

    @Override

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

        if (ucp != null) {

            List<URL> result = new ArrayList<>();

            PrivilegedAction<Enumeration<URL>> pa = () -> ucp.findResources(name, false);

            Enumeration<URL> e = AccessController.doPrivileged(pa);

            while (e.hasMoreElements()) {

                URL url = checkURL(e.nextElement());

                if (url != null) {

                    result.add(url);

                }

            }

            return Collections.enumeration(result); // checked URLs

        } else {

            return Collections.emptyEnumeration();

        }

    }

    // -- finding/loading classes

    /**

     * Finds the class with the specified binary name.

     */

    @Override

    protected Class<?> findClass(String cn) throws ClassNotFoundException {

        // no class loading until VM is fully initialized

        if (!VM.isModuleSystemInited())

            throw new ClassNotFoundException(cn);

        // find the candidate module for this class

        LoadedModule loadedModule = findLoadedModule(cn);

        Class<?> c = null;

        if (loadedModule != null) {

            // attempt to load class in module defined to this loader

            if (loadedModule.loader() == this) {

                c = findClassInModuleOrNull(loadedModule, cn);

            }

        } else {

            // search class path

            if (ucp != null) {

                c = findClassOnClassPathOrNull(cn);

            }

        }

        // not found

        if (c == null)

            throw new ClassNotFoundException(cn);

        return c;

    }

    /**

     * Finds the class with the specified binary name in a given module.

     * This method returns {@code null} if the class cannot be found.

     */

    @Override

    protected Class<?> findClass(String mn, String cn) {

        ModuleReference mref = nameToModule.get(mn);

        if (mref == null)

            return null;   // not defined to this class loader

        // find the candidate module for this class

        LoadedModule loadedModule = findLoadedModule(cn);

        if (loadedModule == null || !loadedModule.name().equals(mn)) {

            return null;   // module name does not match

        }

        // attempt to load class in module defined to this loader

        assert loadedModule.loader() == this;

        return findClassInModuleOrNull(loadedModule, cn);

    }

    /**

     * Loads the class with the specified binary name.

     */

    @Override

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

        throws ClassNotFoundException

    {

        Class<?> c = loadClassOrNull(cn, resolve);

        if (c == null)

            throw new ClassNotFoundException(cn);

        return c;

    }

    /**

     * A variation of {@code loadCass} to load a class with the specified

     * binary name. This method returns {@code null} when the class is not

     * found.

     */

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

        synchronized (getClassLoadingLock(cn)) {

            // check if already loaded

            Class<?> c = findLoadedClass(cn);

            if (c == null) {

                // find the candidate module for this class

                LoadedModule loadedModule = findLoadedModule(cn);

                if (loadedModule != null) {

                    // package is in a module

                    BuiltinClassLoader loader = loadedModule.loader();

                    if (loader == this) {

                        if (VM.isModuleSystemInited()) {

                            c = findClassInModuleOrNull(loadedModule, cn);

                        }

                    } else {

                        // delegate to the other loader

                        c = loader.loadClassOrNull(cn);

                    }

                } else {

                    // check parent

                    if (parent != null) {

                        c = parent.loadClassOrNull(cn);

                    }

                    // check class path

                    if (c == null && ucp != null && VM.isModuleSystemInited()) {

                        c = findClassOnClassPathOrNull(cn);

                    }

                }

            }

            if (resolve && c != null)

                resolveClass(c);

            return c;

        }

    }

    /**

     * A variation of {@code loadCass} to load a class with the specified

     * binary name. This method returns {@code null} when the class is not

     * found.

     */

    protected  Class<?> loadClassOrNull(String cn) {

        return loadClassOrNull(cn, false);

    }

    /**

     * Find the candidate loaded module for the given class name.

     * Returns {@code null} if none of the modules defined to this

     * class loader contain the API package for the class.

     */

    private LoadedModule findLoadedModule(String cn) {

        int pos = cn.lastIndexOf('.');

        if (pos < 0)

            return null; // unnamed package

        String pn = cn.substring(0, pos);

        return packageToModule.get(pn);

    }

    /**

     * Finds the class with the specified binary name if in a module

     * defined to this ClassLoader.

     *

     * @return the resulting Class or {@code null} if not found

     */

    private Class<?> findClassInModuleOrNull(LoadedModule loadedModule, String cn) {

        PrivilegedAction<Class<?>> pa = () -> defineClass(cn, loadedModule);

        return AccessController.doPrivileged(pa);

    }

    /**

     * Finds the class with the specified binary name on the class path.

     *

     * @return the resulting Class or {@code null} if not found

     */

    private Class<?> findClassOnClassPathOrNull(String cn) {

        return AccessController.doPrivileged(

            new PrivilegedAction<Class<?>>() {

                public Class<?> run() {

                    String path = cn.replace('.', '/').concat(".class");

                    Resource res = ucp.getResource(path, false);

                    if (res != null) {

                        try {

                            return defineClass(cn, res);

                        } catch (IOException ioe) {

                            // TBD on how I/O errors should be propagated

                        }

                    }

                    return null;

                }

            });

    }

    /**

     * Defines the given binary class name to the VM, loading the class

     * bytes from the given module.

     *

     * @return the resulting Class or {@code null} if an I/O error occurs

     */

    private Class<?> defineClass(String cn, LoadedModule loadedModule) {

        ModuleReference mref = loadedModule.mref();

        ModuleReader reader = moduleReaderFor(mref);

        try {

            ByteBuffer bb = null;

            URL csURL = null;

            // locate class file, special handling for patched modules to

            // avoid locating the resource twice

            String rn = cn.replace('.', '/').concat(".class");

            if (reader instanceof PatchedModuleReader) {

                Resource r = ((PatchedModuleReader)reader).findResource(rn);

                if (r != null) {

                    bb = r.getByteBuffer();

                    csURL = r.getCodeSourceURL();

                }

            } else {

                bb = reader.read(rn).orElse(null);

                csURL = loadedModule.codeSourceURL();

            }

            if (bb == null) {

                // class not found

                return null;

            }

            CodeSource cs = new CodeSource(csURL, (CodeSigner[]) null);

            try {

                // define class to VM

                return defineClass(cn, bb, cs);

            } finally {

                reader.release(bb);

            }

        } catch (IOException ioe) {

            // TBD on how I/O errors should be propagated

            return null;

        }

    }

    /**

     * Defines the given binary class name to the VM, loading the class

     * bytes via the given Resource object.

     *

     * @return the resulting Class