/*

 * Copyright (c) 2010, 2013, 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

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package jdk.nashorn.internal.runtime;

import static jdk.nashorn.internal.codegen.Compiler.SCRIPTS_PACKAGE;

import static jdk.nashorn.internal.codegen.Compiler.binaryName;

import static jdk.nashorn.internal.codegen.CompilerConstants.JS_OBJECT_DUAL_FIELD_PREFIX;

import static jdk.nashorn.internal.codegen.CompilerConstants.JS_OBJECT_SINGLE_FIELD_PREFIX;

import java.lang.module.ModuleDescriptor;

import java.lang.module.ModuleDescriptor.Modifier;

import java.security.ProtectionDomain;

import java.util.Set;

import jdk.nashorn.internal.codegen.ObjectClassGenerator;

/**

 * Responsible for on the fly construction of structure classes.

 */

final class StructureLoader extends NashornLoader {

    private static final String SINGLE_FIELD_PREFIX = binaryName(SCRIPTS_PACKAGE) + '.' + JS_OBJECT_SINGLE_FIELD_PREFIX.symbolName();

    private static final String DUAL_FIELD_PREFIX   = binaryName(SCRIPTS_PACKAGE) + '.' + JS_OBJECT_DUAL_FIELD_PREFIX.symbolName();

    private final Module structuresModule;

    /**

     * Constructor.

     */

    StructureLoader(final ClassLoader parent) {

        super(parent);

        // new structures module, it's exports, read edges

        structuresModule = createModule("jdk.scripting.nashorn.structures");

        // specific exports from nashorn to the structures module

        NASHORN_MODULE.addExports(SCRIPTS_PKG, structuresModule);

        NASHORN_MODULE.addExports(RUNTIME_PKG, structuresModule);

        // nashorn has to read fields from classes of the new module

        NASHORN_MODULE.addReads(structuresModule);

    }

    private Module createModule(final String moduleName) {

        final ModuleDescriptor descriptor =

            ModuleDescriptor.newModule(moduleName, Set.of(Modifier.SYNTHETIC))

                            .requires(NASHORN_MODULE.getName())

                            .packages(Set.of(SCRIPTS_PKG))

                            .build();

        final Module mod = Context.createModuleTrusted(descriptor, this);

        loadModuleManipulator();

        return mod;

    }

    /**

     * Returns true if the class name represents a structure object with dual primitive/object fields.

     * @param name a class name

     * @return true if a dual field structure class

     */

    private static boolean isDualFieldStructure(final String name) {

        return name.startsWith(DUAL_FIELD_PREFIX);

    }

    /**

     * Returns true if the class name represents a structure object with single object-only fields.

     * @param name a class name

     * @return true if a single field structure class

     */

    static boolean isSingleFieldStructure(final String name) {

        return name.startsWith(SINGLE_FIELD_PREFIX);

    }

    /**

     * Returns true if the class name represents a Nashorn structure object.

     * @param name a class name

     * @return true if a structure class

     */

    static boolean isStructureClass(final String name) {

        return isDualFieldStructure(name) || isSingleFieldStructure(name);

    }

    Module getModule() {

        return structuresModule;

    }

    @Override

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

        if (isDualFieldStructure(name)) {

            return generateClass(name, name.substring(DUAL_FIELD_PREFIX.length()), true);

        } else if (isSingleFieldStructure(name)) {

            return generateClass(name, name.substring(SINGLE_FIELD_PREFIX.length()), false);

        }

        return super.findClass(name);

    }

    /**

     * Generate a layout class.

     * @param name       Name of class.

     * @param descriptor Layout descriptor.

     * @return Generated class.

     */

    private Class<?> generateClass(final String name, final String descriptor, final boolean dualFields) {

        final Context context = Context.getContextTrusted();

        final byte[] code = new ObjectClassGenerator(context, dualFields).generate(descriptor);

        return defineClass(name, code, 0, code.length, new ProtectionDomain(null, getPermissions(null)));

    }

}