/*
 * Copyright (c) 2015, 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 descriptor) {

        ClassWriter cw = new ClassWriter(0);

        String name = descriptor.name().replace('.', '/') + "/module-info";
        cw.visit(Opcodes.V1_8, ACC_MODULE, name, null, null, null);

        cw.visitAttribute(new ModuleAttribute(descriptor));
        cw.visitAttribute(new ConcealedPackagesAttribute(descriptor.conceals()));

        Optional<Version> oversion = descriptor.version();
        if (oversion.isPresent())
            cw.visitAttribute(new VersionAttribute(oversion.getWhenPresent()));

        Optional<String> omain = descriptor.mainClass();
        if (omain.isPresent())
            cw.visitAttribute(new MainClassAttribute(omain.getWhenPresent()));

        // write the TargetPlatform attribute if have any of OS name/arch/version
        String osName = descriptor.osName().orElse(null);
        String osArch = descriptor.osArch().orElse(null);
        String osVersion = descriptor.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);
    }

}