/*

 * Copyright (c) 2014, 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 java.lang.reflect;

import java.io.IOException;

import java.io.InputStream;

import java.lang.annotation.Annotation;

import java.lang.module.Configuration;

import java.lang.module.ModuleReference;

import java.lang.module.ModuleDescriptor;

import java.lang.module.ModuleDescriptor.Exports;

import java.lang.module.ModuleDescriptor.Opens;

import java.lang.module.ModuleDescriptor.Version;

import java.lang.module.ResolvedModule;

import java.net.URI;

import java.net.URL;

import java.security.AccessController;

import java.security.PrivilegedAction;

import java.util.Collections;

import java.util.HashMap;

import java.util.HashSet;

import java.util.Map;

import java.util.Objects;

import java.util.Optional;

import java.util.Set;

import java.util.concurrent.ConcurrentHashMap;

import java.util.function.Function;

import java.util.stream.Stream;

import jdk.internal.loader.BuiltinClassLoader;

import jdk.internal.loader.BootLoader;

import jdk.internal.loader.ResourceHelper;

import jdk.internal.misc.JavaLangAccess;

import jdk.internal.misc.JavaLangReflectModuleAccess;

import jdk.internal.misc.SharedSecrets;

import jdk.internal.module.ServicesCatalog;

import jdk.internal.org.objectweb.asm.AnnotationVisitor;

import jdk.internal.org.objectweb.asm.Attribute;

import jdk.internal.org.objectweb.asm.ClassReader;

import jdk.internal.org.objectweb.asm.ClassVisitor;

import jdk.internal.org.objectweb.asm.ClassWriter;

import jdk.internal.org.objectweb.asm.Opcodes;

import jdk.internal.reflect.CallerSensitive;

import jdk.internal.reflect.Reflection;

import sun.security.util.SecurityConstants;

/**

 * Represents a run-time module, either {@link #isNamed() named} or unnamed.

 *

 * <p> Named modules have a {@link #getName() name} and are constructed by the

 * Java Virtual Machine when a graph of modules is defined to the Java virtual

 * machine to create a module {@link Layer Layer}. </p>

 *

 * <p> An unnamed module does not have a name. There is an unnamed module

 * per {@link ClassLoader ClassLoader} that is obtained by invoking the class

 * loader's {@link ClassLoader#getUnnamedModule() getUnnamedModule} method. The

 * {@link Class#getModule() getModule} method of all types defined by a class

 * loader that are not in a named module return the class loader's unnamed

 * module. </p>

 *

 * <p> The package names that are parameters or returned by methods defined in

 * this class are the fully-qualified names of the packages as defined in

 * section 6.5.3 of <cite>The Java&trade; Language Specification </cite>, for

 * example, {@code "java.lang"}. </p>

 *

 * <p> Unless otherwise specified, passing a {@code null} argument to a method

 * in this class causes a {@link NullPointerException NullPointerException} to

 * be thrown. </p>

 *

 * @since 9

 * @see java.lang.Class#getModule

 */

public final class Module implements AnnotatedElement {

    // the layer that contains this module, can be null

    private final Layer layer;

    // module name and loader, these fields are read by VM

    private final String name;

    private final ClassLoader loader;

    // the module descriptor

    private final ModuleDescriptor descriptor;

    /**

     * Creates a new named Module. The resulting Module will be defined to the

     * VM but will not read any other modules, will not have any exports setup

     * and will not be registered in the service catalog.

     */

    private Module(Layer layer,

                   ClassLoader loader,

                   ModuleDescriptor descriptor,

                   URI uri)

    {

        this.layer = layer;

        this.name = descriptor.name();

        this.loader = loader;

        this.descriptor = descriptor;

        // define module to VM

        boolean isOpen = descriptor.isOpen();

        Version version = descriptor.version().orElse(null);

        String vs = Objects.toString(version, null);

        String loc = Objects.toString(uri, null);

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

        int n = packages.size();

        String[] array = new String[n];

        int i = 0;

        for (String pn : packages) {

            array[i++] = pn.replace('.', '/');

        }

        defineModule0(this, isOpen, vs, loc, array);

    }

    /**

     * Create the unnamed Module for the given ClassLoader.

     *

     * @see ClassLoader#getUnnamedModule

     */

    private Module(ClassLoader loader) {

        this.layer = null;

        this.name = null;

        this.loader = loader;

        this.descriptor = null;

    }

    /**

     * Creates a named module but without defining the module to the VM.

     *

     * @apiNote This constructor is for VM white-box testing.

     */

    Module(ClassLoader loader, ModuleDescriptor descriptor) {

        this.layer = null;

        this.name = descriptor.name();

        this.loader = loader;

        this.descriptor = descriptor;

    }

    /**

     * Returns {@code true} if this module is a named module.

     *

     * @return {@code true} if this is a named module

     *

     * @see ClassLoader#getUnnamedModule()

     */

    public boolean isNamed() {

        return name != null;

    }

    /**

     * Returns the module name or {@code null} if this module is an unnamed

     * module.

     *

     * @return The module name

     */

    public String getName() {

        return name;

    }

    /**

     * Returns the {@code ClassLoader} for this module.

     *

     * <p> If there is a security manager then its {@code checkPermission}

     * method if first called with a {@code RuntimePermission("getClassLoader")}

     * permission to check that the caller is allowed to get access to the

     * class loader. </p>

     *

     * @return The class loader for this module

     *

     * @throws SecurityException

     *         If denied by the security manager

     */

    public ClassLoader getClassLoader() {

        SecurityManager sm = System.getSecurityManager();

        if (sm != null) {

            sm.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION);

        }

        return loader;

    }

    /**

     * Returns the module descriptor for this module or {@code null} if this

     * module is an unnamed module.

     *

     * @return The module descriptor for this module

     */

    public ModuleDescriptor getDescriptor() {

        return descriptor;

    }

    /**

     * Returns the layer that contains this module or {@code null} if this

     * module is not in a layer.

     *

     * A module {@code Layer} contains named modules and therefore this

     * method always returns {@code null} when invoked on an unnamed module.

     *

     * <p> <a href="Proxy.html#dynamicmodule">Dynamic modules</a> are named

     * modules that are generated at runtime. A dynamic module may or may

     * not be in a module Layer. </p>

     *

     * @return The layer that contains this module

     *

     * @see Proxy

     */

    public Layer getLayer() {

        if (isNamed()) {

            Layer layer = this.layer;

            if (layer != null)

                return layer;

            // special-case java.base as it is created before the boot Layer

            if (loader == null && name.equals("java.base")) {

                return SharedSecrets.getJavaLangAccess().getBootLayer();

            }

        }

        return null;

    }

    // --

    // special Module to mean "all unnamed modules"

    private static final Module ALL_UNNAMED_MODULE = new Module(null);

    // special Module to mean "everyone"

    private static final Module EVERYONE_MODULE = new Module(null);

    // set contains EVERYONE_MODULE, used when a package is opened or

    // exported unconditionally

    private static final Set<Module> EVERYONE_SET = Set.of(EVERYONE_MODULE);

    // -- readability --

    // the modules that this module reads

    private volatile Set<Module> reads;

    // additional module (2nd key) that some module (1st key) reflectively reads

    private static final WeakPairMap<Module, Module, Boolean> reflectivelyReads

        = new WeakPairMap<>();

    /**

     * Indicates if this module reads the given module. This method returns

     * {@code true} if invoked to test if this module reads itself. It also

     * returns {@code true} if invoked on an unnamed module (as unnamed

     * modules read all modules).

     *

     * @param  other

     *         The other module

     *

     * @return {@code true} if this module reads {@code other}

     *

     * @see #addReads(Module)

     */

    public boolean canRead(Module other) {

        Objects.requireNonNull(other);

        // an unnamed module reads all modules

        if (!this.isNamed())

            return true;

        // all modules read themselves

        if (other == this)

            return true;

        // check if this module reads other

        if (other.isNamed()) {

            Set<Module> reads = this.reads; // volatile read

            if (reads != null && reads.contains(other))

                return true;

        }

        // check if this module reads the other module reflectively

        if (reflectivelyReads.containsKeyPair(this, other))

            return true;

        // if other is an unnamed module then check if this module reads

        // all unnamed modules

        if (!other.isNamed()

            && reflectivelyReads.containsKeyPair(this, ALL_UNNAMED_MODULE))

            return true;

        return false;

    }

    /**

     * If the caller's module is this module then update this module to read

     * the given module.

     *

     * This method is a no-op if {@code other} is this module (all modules read

     * themselves), this module is an unnamed module (as unnamed modules read

     * all modules), or this module already reads {@code other}.

     *

     * @implNote <em>Read edges</em> added by this method are <em>weak</em> and

     * do not prevent {@code other} from being GC'ed when this module is

     * strongly reachable.

     *

     * @param  other

     *         The other module

     *

     * @return this module

     *

     * @throws IllegalStateException

     *         If this is a named module and the caller is not this module

     *

     * @see #canRead

     */

    @CallerSensitive

    public Module addReads(Module other) {

        Objects.requireNonNull(other);

        if (this.isNamed()) {

            Module caller = Reflection.getCallerClass().getModule();

            if (caller != this) {

                throw new IllegalStateException(caller + " != " + this);

            }

            implAddReads(other, true);

        }

        return this;

    }

    /**

     * Updates this module to read another module.

     *

     * @apiNote This method is for Proxy use and white-box testing.

     */

    void implAddReads(Module other) {

        implAddReads(other, true);

    }

    /**

     * Updates this module to read another module without notifying the VM.

     *

     * @apiNote This method is for VM white-box testing.

     */

    void implAddReadsNoSync(Module other) {

        implAddReads(other, false);

    }

    /**

     * Makes the given {@code Module} readable to this module.

     *

     * If {@code syncVM} is {@code true} then the VM is notified.

     */

    private void implAddReads(Module other, boolean syncVM) {

        Objects.requireNonNull(other);

        // nothing to do

        if (other == this || !this.isNamed())

            return;

        // check if we already read this module

        Set<Module> reads = this.reads;

        if (reads != null && reads.contains(other))

            return;

        // update VM first, just in case it fails

        if (syncVM) {

            if (other == ALL_UNNAMED_MODULE) {

                addReads0(this, null);

            } else {

                addReads0(this, other);

            }

        }

        // add reflective read

        reflectivelyReads.putIfAbsent(this, other, Boolean.TRUE);

    }

    // -- exported and open packages --

    // the packages are open to other modules, can be null

    // if the value contains EVERYONE_MODULE then the package is open to all

    private volatile Map<String, Set<Module>> openPackages;

    // the packages that are exported, can be null

    // if the value contains EVERYONE_MODULE then the package is exported to all

    private volatile Map<String, Set<Module>> exportedPackages;

    // additional exports or opens added at run-time

    // this module (1st key), other module (2nd key)

    // (package name, open?) (value)

    private static final WeakPairMap<Module, Module, Map<String, Boolean>>

        reflectivelyExports = new WeakPairMap<>();

    /**

     * Returns {@code true} if this module exports the given package to at

     * least the given module.

     *

     * <p> This method returns {@code true} if invoked to test if a package in

     * this module is exported to itself. It always returns {@code true} when

     * invoked on an unnamed module. A package that is {@link #isOpen open} to

     * the given module is considered exported to that module at run-time and

     * so this method returns {@code true} if the package is open to the given

     * module. </p>

     *

     * <p> This method does not check if the given module reads this module. </p>

     *

     * @param  pn

     *         The package name

     * @param  other

     *         The other module

     *

     * @return {@code true} if this module exports the package to at least the

     *         given module

     *

     * @see ModuleDescriptor#exports()

     * @see #addExports(String,Module)

     */

    public boolean isExported(String pn, Module other) {

        Objects.requireNonNull(pn);

        Objects.requireNonNull(other);

        return implIsExportedOrOpen(pn, other, /*open*/false);

    }

    /**

     * Returns {@code true} if this module has <em>opened</em> a package to at

     * least the given module.

     *

     * <p> This method returns {@code true} if invoked to test if a package in

     * this module is open to itself. It returns {@code true} when invoked on an

     * {@link ModuleDescriptor#isOpen open} module with a package in the module.

     * It always returns {@code true} when invoked on an unnamed module. </p>

     *

     * <p> This method does not check if the given module reads this module. </p>

     *

     * @param  pn

     *         The package name

     * @param  other

     *         The other module

     *

     * @return {@code true} if this module has <em>opened</em> the package

     *         to at least the given module

     *

     * @see ModuleDescriptor#opens()

     * @see #addOpens(String,Module)

     * @see AccessibleObject#setAccessible(boolean)

     * @see java.lang.invoke.MethodHandles#privateLookupIn

     */

    public boolean isOpen(String pn, Module other) {

        Objects.requireNonNull(pn);

        Objects.requireNonNull(other);

        return implIsExportedOrOpen(pn, other, /*open*/true);

    }

    /**

     * Returns {@code true} if this module exports the given package

     * unconditionally.

     *

     * <p> This method always returns {@code true} when invoked on an unnamed

     * module. A package that is {@link #isOpen(String) opened} unconditionally

     * is considered exported unconditionally at run-time and so this method

     * returns {@code true} if the package is opened unconditionally. </p>

     *

     * <p> This method does not check if the given module reads this module. </p>

     *

     * @param  pn

     *         The package name

     *

     * @return {@code true} if this module exports the package unconditionally

     *

     * @see ModuleDescriptor#exports()

     */

    public boolean isExported(String pn) {

        Objects.requireNonNull(pn);

        return implIsExportedOrOpen(pn, EVERYONE_MODULE, /*open*/false);

    }

    /**

     * Returns {@code true} if this module has <em>opened</em> a package

     * unconditionally.

     *

     * <p> This method always returns {@code true} when invoked on an unnamed

     * module. Additionally, it always returns {@code true} when invoked on an

     * {@link ModuleDescriptor#isOpen open} module with a package in the

     * module. </p>

     *

     * <p> This method does not check if the given module reads this module. </p>

     *

     * @param  pn

     *         The package name