/*

 * 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.module;

import java.io.IOException;

import java.io.OutputStream;

import java.lang.module.ModuleDescriptor;

import java.lang.module.ModuleDescriptor.Version;

import java.nio.ByteBuffer;

import java.util.Optional;

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

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

import static jdk.internal.module.ClassFileAttributes.*;

import static jdk.internal.module.ClassFileConstants.ACC_MODULE;

/**

 * Utility class to write a ModuleDescriptor as a module-info.class.

 */

public final class ModuleInfoWriter {

    private ModuleInfoWriter() { }

    /**

     * Writes the given module descriptor to a module-info.class file,

     * returning it in a byte array.

     */

    private static byte[] toModuleInfo(ModuleDescriptor md) {

        ClassWriter cw = new ClassWriter(0);

        String name = md.name().replace('.', '/') + "/module-info";

        cw.visit(Opcodes.V1_9, ACC_MODULE, name, null, null, null);

        cw.visitAttribute(new ModuleAttribute(md));

        md.version().ifPresent(v -> cw.visitAttribute(new VersionAttribute(v)));

        md.mainClass().ifPresent(mc -> cw.visitAttribute(new MainClassAttribute(mc)));

        // write the TargetPlatform attribute if have any of OS name/arch/version

        String osName = md.osName().orElse(null);

        String osArch = md.osArch().orElse(null);

        String osVersion = md.osVersion().orElse(null);

        if (osName != null || osArch != null || osVersion != null) {

            cw.visitAttribute(new TargetPlatformAttribute(osName,

                                                          osArch,

                                                          osVersion));

        }

        cw.visitEnd();

        return cw.toByteArray();

    }

    /**

     * Writes a module descriptor to the given output stream as a

     * module-info.class.

     */

    public static void write(ModuleDescriptor descriptor, OutputStream out)

        throws IOException

    {

        byte[] bytes = toModuleInfo(descriptor);

        out.write(bytes);

    }

    /**

     * Returns a {@code ByteBuffer} containing the given module descriptor

     * in module-info.class format.

     */

    public static ByteBuffer toByteBuffer(ModuleDescriptor descriptor) {

        byte[] bytes = toModuleInfo(descriptor);

        return ByteBuffer.wrap(bytes);

    }

}