/*

 * 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 com.sun.tools.javac.util;

import java.lang.reflect.InvocationTargetException;

import java.lang.reflect.Method;

import java.nio.file.Path;

import java.util.Collection;

import java.util.ServiceLoader;

/**

 *  This class provides wrappers for classes and methods that are new in JDK 9, and which are not

 *  available on older versions of the platform on which javac may be compiled and run.

 *  In future releases, when javac is always compiled on JDK 9 or later, the use of these wrappers

 *  can be replaced by use of the real underlying classes.

 *

 *  <p>Wrapper classes provide a subset of the API of the wrapped classes, as needed for use

 *  in javac. Wrapper objects contain an {@code Object} reference to the underlying runtime object,

 *  and {@code Class} and {@code Method} objects for obtaining or using such instances via

 *  runtime reflection.  The {@code Class} and {@code Method} objects are set up on a per-class

 *  basis, by an {@code init} method, which is called from static methods on the wrapper class,

 *  or in the constructor, when instances are created.

 *  <p>

 *

 *  <p><b>This is NOT part of any supported API.

 *  If you write code that depends on this, you do so at your own risk.

 *  This code and its internal interfaces are subject to change or

 *  deletion without notice.</b>

 */

public class JDK9Wrappers {

    /**

     * Helper class for new method in java.util.ServiceLoader.

     */

    public static final class ServiceLoaderHelper {

        @SuppressWarnings("unchecked")

        public static <S> ServiceLoader<S> load(Layer layer, Class<S> service) {

            try {

                init();

                Object result = loadMethod.invoke(null, layer.theRealLayer, service);

                return (ServiceLoader<S>)result;

            } catch (IllegalAccessException | IllegalArgumentException | InvocationTargetException

                    | SecurityException ex) {

                throw new Abort(ex);

            }

        }

        // -----------------------------------------------------------------------------------------

        private static Method loadMethod = null;

        private static void init() {

            if (loadMethod == null) {

                try {

                    Class<?> layerClass = Layer.layerClass;

                    loadMethod = ServiceLoader.class.getDeclaredMethod("load", layerClass, Class.class);

                } catch (NoSuchMethodException | SecurityException ex) {

                    throw new Abort(ex);

                }

            }

        }

    }

    /**

     * Wrapper class for java.lang.module.ModuleFinder.

     */

    public static class ModuleFinder {

        private final Object theRealModuleFinder;

        private ModuleFinder(Object moduleFinder) {

            this.theRealModuleFinder = moduleFinder;

            init();

        }

        public static ModuleFinder of(Path... dirs) {

            try {

                init();

                Object result = ofMethod.invoke(null, (Object)dirs);

                ModuleFinder mFinder = new ModuleFinder(result);

                return mFinder;

            } catch (IllegalAccessException | IllegalArgumentException | InvocationTargetException

                    | SecurityException ex) {

                throw new Abort(ex);

            }

        }

        // -----------------------------------------------------------------------------------------

        private static Class<?> moduleFinderClass = null;

        private static Method ofMethod;

        static final Class<?> getModuleFinderClass() {

            init();

            return moduleFinderClass;

        }

        private static void init() {

            if (moduleFinderClass == null) {

                try {

                    moduleFinderClass = Class.forName("java.lang.module.ModuleFinder", false, null);

                    ofMethod = moduleFinderClass.getDeclaredMethod("of", Path[].class);

                } catch (ClassNotFoundException | NoSuchMethodException | SecurityException ex) {

                    throw new Abort(ex);

                }

            }

        }

    }

    /**

     * Wrapper class for java.lang.module.Configuration.

     */

    public static final class Configuration {

        private final Object theRealConfiguration;

        private Configuration(Object configuration) {

            this.theRealConfiguration = configuration;

            init();

        }

        public Configuration resolveRequiresAndUses(

                ModuleFinder beforeFinder,

                ModuleFinder afterFinder,

                Collection<String> roots) {

            try {

                Object result = resolveRequiresAndUsesMethod.invoke(theRealConfiguration,

                                    beforeFinder.theRealModuleFinder,

                                    afterFinder.theRealModuleFinder,

                                    roots

                                );

                Configuration configuration = new Configuration(result);

                return configuration;

            } catch (IllegalAccessException | IllegalArgumentException | InvocationTargetException

                    | SecurityException ex) {

                throw new Abort(ex);

            }

        }

        // -----------------------------------------------------------------------------------------

        private static Class<?> configurationClass = null;

        private static Method resolveRequiresAndUsesMethod;

        static final Class<?> getConfigurationClass() {

            init();

            return configurationClass;

        }

        private static void init() {

            if (configurationClass == null) {

                try {

                    configurationClass = Class.forName("java.lang.module.Configuration", false, null);

                    Class<?> moduleFinderInterface = ModuleFinder.getModuleFinderClass();

                    resolveRequiresAndUsesMethod = configurationClass.getDeclaredMethod("resolveRequiresAndUses",

                                moduleFinderInterface,

                                moduleFinderInterface,

                                Collection.class

                    );

                } catch (ClassNotFoundException | NoSuchMethodException | SecurityException ex) {

                    throw new Abort(ex);

                }

            }

        }

    }

    /**

     * Wrapper class for java.lang.module.Layer.

     */

    public static final class Layer {

        private final Object theRealLayer;

        private Layer(Object layer) {

            this.theRealLayer = layer;

        }

        public static Layer boot() {

            try {

                init();

                Object result = bootMethod.invoke(null);

                Layer layer = new Layer(result);

                return layer;

            } catch (IllegalAccessException | IllegalArgumentException | InvocationTargetException

                    | SecurityException ex) {

                throw new Abort(ex);

            }

        }

        public Configuration configuration() {

            try {

                Object result = configurationMethod.invoke(theRealLayer);

                Configuration configuration = new Configuration(result);

                return configuration;

            } catch (IllegalAccessException | IllegalArgumentException | InvocationTargetException

                    | SecurityException ex) {

                throw new Abort(ex);

            }

        }

        public Layer defineModulesWithOneLoader(Configuration configuration, ClassLoader parentClassLoader) {

            try {

                Object result = defineModulesWithOneLoaderMethod.invoke(

                        theRealLayer, configuration.theRealConfiguration, parentClassLoader);

                Layer layer = new Layer(result);

                return layer;

            } catch (IllegalAccessException | IllegalArgumentException | InvocationTargetException

                    | SecurityException ex) {

                throw new Abort(ex);

            }

        }

        // -----------------------------------------------------------------------------------------

        private static Class<?> layerClass = null;

        private static Method bootMethod;

        private static Method defineModulesWithOneLoaderMethod;

        private static Method configurationMethod;

        private static void init() {

            if (layerClass == null) {

                try {

                    layerClass = Class.forName("java.lang.reflect.Layer", false, null);

                    bootMethod = layerClass.getDeclaredMethod("boot");

                    defineModulesWithOneLoaderMethod = layerClass.getDeclaredMethod("defineModulesWithOneLoader",

                                Configuration.getConfigurationClass(),

                                ClassLoader.class);

                    configurationMethod = layerClass.getDeclaredMethod("configuration");

                } catch (ClassNotFoundException | NoSuchMethodException | SecurityException ex) {

                    throw new Abort(ex);

                }

            }

        }

    }

}