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/*
 * Copyright (c) 2017, 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.javafx.application;

import java.lang.module.ModuleDescriptor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Optional;

public final class ModuleAccess {

    private final Object module;
    private ModuleAccess(Object m) {
        this.module = m;
    }

    ModuleDescriptor getDescriptor() {
        try {
            return (ModuleDescriptor) getDescriptorMethod.invoke(module);
        } catch (IllegalAccessException | InvocationTargetException e) {
            throw new InternalError(e);
        }
    }

    String getName() {
        try {
            return (String) getModuleNameMethod.invoke(module);
        } catch (IllegalAccessException | InvocationTargetException e) {
            throw new InternalError(e);
        }
    }

    Class classForName(String name) {
        try {
            return (Class) classForNameMethod.invoke(null, module, name);
        } catch (IllegalAccessException | InvocationTargetException e) {
            throw new InternalError(e);
        }
    }

    static ModuleAccess load(String moduleName) {
        // main module is in the boot layer
        try {
            Object layer = bootLayerMethod.invoke(null);

            Optional om =
                (Optional)findModuleMethod.invoke(layer, moduleName);
            if (!om.isPresent()) {
                // should not happen
                throw new
                   InternalError("Module " + moduleName + " not in boot Layer");
            }
            return new ModuleAccess(om.get());
        } catch (IllegalAccessException | InvocationTargetException e) {
            throw new InternalError(e);
        }
    }

    private static final Method bootLayerMethod;
    private static final Method getModuleNameMethod;
    private static final Method findModuleMethod;
    private static final Method getDescriptorMethod;
    private static final Method classForNameMethod;

    static {
        Class cModuleClass = null;
        Method mGetModule = null;
        Method mGetLayer = null;
        Method mGetDescriptor = null;
        Method mGetName = null;
        Method mBootLayers = null;
        Method mfindModule = null;
        Method mClassForName = null;

        try {
            mGetModule = Class.class.getMethod("getModule");
            cModuleClass = mGetModule.getReturnType();
            mGetLayer = cModuleClass.getMethod("getLayer");
            mGetDescriptor = cModuleClass.getMethod("getDescriptor");
            mGetName = cModuleClass.getMethod("getName");

            Class layerClass = mGetLayer.getReturnType();
            mBootLayers = layerClass.getMethod("boot");
            mfindModule = layerClass.getMethod("findModule", String.class);

            mClassForName =
                Class.class.getMethod("forName", cModuleClass, String.class);

        } catch (NoSuchMethodException e) {
            throw new InternalError("Module reflection failed", e);
        }

        bootLayerMethod = mBootLayers;
        getModuleNameMethod = mGetName;
        getDescriptorMethod = mGetDescriptor;
        findModuleMethod = mfindModule;
        classForNameMethod = mClassForName;
    }
}