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	/*
	* Copyright (c) 2015, 2020, 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.nio.ByteBuffer;
	import java.util.Map;
	import java.util.stream.Stream;

	import jdk.internal.org.objectweb.asm.ClassWriter;
	import jdk.internal.org.objectweb.asm.ModuleVisitor;
	import jdk.internal.org.objectweb.asm.Opcodes;
	import jdk.internal.org.objectweb.asm.commons.ModuleResolutionAttribute;
	import jdk.internal.org.objectweb.asm.commons.ModuleTargetAttribute;
	import static jdk.internal.org.objectweb.asm.Opcodes.*;

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

	public final class ModuleInfoWriter {

	private static final Map<ModuleDescriptor.Modifier, Integer>
	MODULE_MODS_TO_FLAGS = Map.of(
	ModuleDescriptor.Modifier.OPEN, ACC_OPEN,
	ModuleDescriptor.Modifier.SYNTHETIC, ACC_SYNTHETIC,
	ModuleDescriptor.Modifier.MANDATED, ACC_MANDATED
	);

	private static final Map<ModuleDescriptor.Requires.Modifier, Integer>
	REQUIRES_MODS_TO_FLAGS = Map.of(
	ModuleDescriptor.Requires.Modifier.TRANSITIVE, ACC_TRANSITIVE,
	ModuleDescriptor.Requires.Modifier.STATIC, ACC_STATIC_PHASE,
	ModuleDescriptor.Requires.Modifier.SYNTHETIC, ACC_SYNTHETIC,
	ModuleDescriptor.Requires.Modifier.MANDATED, ACC_MANDATED
	);

	private static final Map<ModuleDescriptor.Exports.Modifier, Integer>
	EXPORTS_MODS_TO_FLAGS = Map.of(
	ModuleDescriptor.Exports.Modifier.SYNTHETIC, ACC_SYNTHETIC,
	ModuleDescriptor.Exports.Modifier.MANDATED, ACC_MANDATED
	);

	private static final Map<ModuleDescriptor.Opens.Modifier, Integer>
	OPENS_MODS_TO_FLAGS = Map.of(
	ModuleDescriptor.Opens.Modifier.SYNTHETIC, ACC_SYNTHETIC,
	ModuleDescriptor.Opens.Modifier.MANDATED, ACC_MANDATED
	);

	private static final String[] EMPTY_STRING_ARRAY = new String[0];

	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,
	ModuleResolution mres,
	ModuleTarget target) {
	ClassWriter cw = new ClassWriter(0);
	cw.visit(Opcodes.V10, ACC_MODULE, "module-info", null, null, null);

	int moduleFlags = md.modifiers().stream()
	.map(MODULE_MODS_TO_FLAGS::get)
	.reduce(0, (x, y) -> (x \| y));
	String vs = md.rawVersion().orElse(null);
	ModuleVisitor mv = cw.visitModule(md.name(), moduleFlags, vs);

	// requires
	for (ModuleDescriptor.Requires r : md.requires()) {
	int flags = r.modifiers().stream()
	.map(REQUIRES_MODS_TO_FLAGS::get)
	.reduce(0, (x, y) -> (x \| y));
	vs = r.rawCompiledVersion().orElse(null);
	mv.visitRequire(r.name(), flags, vs);
	}

	// exports
	for (ModuleDescriptor.Exports e : md.exports()) {
	int flags = e.modifiers().stream()
	.map(EXPORTS_MODS_TO_FLAGS::get)
	.reduce(0, (x, y) -> (x \| y));
	String[] targets = e.targets().toArray(EMPTY_STRING_ARRAY);
	mv.visitExport(e.source().replace('.', '/'), flags, targets);
	}

	// opens
	for (ModuleDescriptor.Opens opens : md.opens()) {
	int flags = opens.modifiers().stream()
	.map(OPENS_MODS_TO_FLAGS::get)
	.reduce(0, (x, y) -> (x \| y));
	String[] targets = opens.targets().toArray(EMPTY_STRING_ARRAY);
	mv.visitOpen(opens.source().replace('.', '/'), flags, targets);
	}

	// uses
	md.uses().stream().map(sn -> sn.replace('.', '/')).forEach(mv::visitUse);

	// provides
	for (ModuleDescriptor.Provides p : md.provides()) {
	mv.visitProvide(p.service().replace('.', '/'),
	p.providers()
	.stream()
	.map(pn -> pn.replace('.', '/'))
	.toArray(String[]::new));
	}

	// add the ModulePackages attribute when there are packages that aren't
	// exported or open
	Stream<String> exported = md.exports().stream()
	.map(ModuleDescriptor.Exports::source);
	Stream<String> open = md.opens().stream()
	.map(ModuleDescriptor.Opens::source);
	long exportedOrOpen = Stream.concat(exported, open).distinct().count();
	if (md.packages().size() > exportedOrOpen) {
	md.packages().stream()
	.map(pn -> pn.replace('.', '/'))
	.forEach(mv::visitPackage);
	}

	// ModuleMainClass attribute
	md.mainClass()
	.map(mc -> mc.replace('.', '/'))
	.ifPresent(mv::visitMainClass);

	mv.visitEnd();

	// write ModuleResolution attribute if specified
	if (mres != null) {
	cw.visitAttribute(new ModuleResolutionAttribute(mres.value()));
	}

	// write ModuleTarget attribute if there is a target platform
	if (target != null && target.targetPlatform().length() > 0) {
	cw.visitAttribute(new ModuleTargetAttribute(target.targetPlatform()));
	}

	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,
	ModuleResolution mres,
	ModuleTarget target,
	OutputStream out)
	throws IOException
	{
	byte[] bytes = toModuleInfo(descriptor, mres, target);
	out.write(bytes);
	}

	/**
	* Writes a module descriptor to the given output stream as a
	* module-info.class.
	*/
	public static void write(ModuleDescriptor descriptor,
	ModuleResolution mres,
	OutputStream out)
	throws IOException
	{
	write(descriptor, mres, null, out);
	}

	/**
	* Writes a module descriptor to the given output stream as a
	* module-info.class.
	*/
	public static void write(ModuleDescriptor descriptor,
	ModuleTarget target,
	OutputStream out)
	throws IOException
	{
	write(descriptor, null, target, out);
	}

	/**
	* Writes a module descriptor to the given output stream as a
	* module-info.class.
	*/
	public static void write(ModuleDescriptor descriptor, OutputStream out)
	throws IOException
	{
	write(descriptor, null, null, out);
	}

	/**
	* Returns a byte array containing the given module descriptor in
	* module-info.class format.
	*/
	public static byte[] toBytes(ModuleDescriptor descriptor) {
	return toModuleInfo(descriptor, null, null);
	}

	/**
	* Returns a {@code ByteBuffer} containing the given module descriptor
	* in module-info.class format.
	*/
	public static ByteBuffer toByteBuffer(ModuleDescriptor descriptor) {
	byte[] bytes = toModuleInfo(descriptor, null, null);
	return ByteBuffer.wrap(bytes);
	}
	}

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