/*

 * Copyright (c) 2014, 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.InputStream;

import java.io.OutputStream;

import java.lang.module.ModuleDescriptor.Version;

import java.util.ArrayList;

import java.util.Collections;

import java.util.HashMap;

import java.util.List;

import java.util.Map;

import java.util.Set;

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

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

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

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

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

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

/**

 * Utility class to extend a module-info.class with additional attributes.

 */

public final class ModuleInfoExtender {

    // the input stream to read the original module-info.class

    private final InputStream in;

    // the packages in the ModulePackages attribute

    private Set<String> packages;

    // the value for the module version in the Module attribute

    private Version version;

    // the value of the ModuleMainClass attribute

    private String mainClass;

    // the value for the ModuleTarget attribute

    private String targetPlatform;

    // the hashes for the ModuleHashes attribute

    private ModuleHashes hashes;

    // the value of the ModuleResolution attribute

    private ModuleResolution moduleResolution;

    private ModuleInfoExtender(InputStream in) {

        this.in = in;

    }

    /**

     * Sets the packages for the ModulePackages attribute

     *

     * @apiNote This method does not check that the package names are legal

     * package names or that the set of packages is a super set of the

     * packages in the module.

     */

    public ModuleInfoExtender packages(Set<String> packages) {

        this.packages = Collections.unmodifiableSet(packages);

        return this;

    }

    /**

     * Sets the value for the module version in the Module attribute

     */

    public ModuleInfoExtender version(Version version) {

        this.version = version;

        return this;

    }

    /**

     * Sets the value of the ModuleMainClass attribute.

     *

     * @apiNote This method does not check that the main class is a legal

     * class name in a named package.

     */

    public ModuleInfoExtender mainClass(String mainClass) {

        this.mainClass = mainClass;

        return this;

    }

    /**

     * Sets the value for the ModuleTarget attribute.

     */

    public ModuleInfoExtender targetPlatform(String targetPlatform) {

        this.targetPlatform = targetPlatform;

        return this;

    }

    /**

     * The ModuleHashes attribute will be emitted to the module-info with

     * the hashes encapsulated in the given {@code ModuleHashes}

     * object.

     */

    public ModuleInfoExtender hashes(ModuleHashes hashes) {

        this.hashes = hashes;

        return this;

    }

    /**

     * Sets the value for the ModuleResolution attribute.

     */

    public ModuleInfoExtender moduleResolution(ModuleResolution mres) {

        this.moduleResolution = mres;

        return this;

    }

    /**

     * A ClassVisitor that supports adding class file attributes. If an

     * attribute already exists then the first occurrence of the attribute

     * is replaced.

     */

    private static class AttributeAddingClassVisitor extends ClassVisitor {

        private Map<String, Attribute> attrs = new HashMap<>();

        AttributeAddingClassVisitor(int api, ClassVisitor cv) {

            super(api, cv);

        }

        void addAttribute(Attribute attr) {

            attrs.put(attr.type, attr);

        }

        @Override

        public void visitAttribute(Attribute attr) {

            String name = attr.type;

            Attribute replacement = attrs.get(name);

            if (replacement != null) {

                attr = replacement;

                attrs.remove(name);

            }

            super.visitAttribute(attr);

        }

        /**

         * Adds any remaining attributes that weren't replaced to the

         * class file.

         */

        void finish() {

            attrs.values().forEach(a -> super.visitAttribute(a));

            attrs.clear();

        }

    }

    /**

     * Outputs the modified module-info.class to the given output stream.

     * Once this method has been called then the Extender object should

     * be discarded.

     */

    public void write(OutputStream out) throws IOException {

        // emit to the output stream

        out.write(toByteArray());

    }

    /**

     * Returns the bytes of the modified module-info.class.

     * Once this method has been called then the Extender object should

     * be discarded.

     */

    public byte[] toByteArray() throws IOException {

        ClassWriter cw

            = new ClassWriter(ClassWriter.COMPUTE_MAXS + ClassWriter.COMPUTE_FRAMES);

        AttributeAddingClassVisitor cv

            = new AttributeAddingClassVisitor(Opcodes.ASM5, cw);

        ClassReader cr = new ClassReader(in);

        if (packages != null)

            cv.addAttribute(new ModulePackagesAttribute(packages));

        if (mainClass != null)

            cv.addAttribute(new ModuleMainClassAttribute(mainClass));

        if (targetPlatform != null)

            cv.addAttribute(new ModuleTargetAttribute(targetPlatform));

        if (hashes != null)

            cv.addAttribute(new ModuleHashesAttribute(hashes));

        if (moduleResolution != null)

            cv.addAttribute(new ModuleResolutionAttribute(moduleResolution.value()));

        List<Attribute> attrs = new ArrayList<>();

        // prototypes of attributes that should be parsed

        attrs.add(new ModuleAttribute(version));

        attrs.add(new ModulePackagesAttribute());

        attrs.add(new ModuleMainClassAttribute());

        attrs.add(new ModuleTargetAttribute());

        attrs.add(new ModuleHashesAttribute());

        cr.accept(cv, attrs.toArray(new Attribute[0]), 0);

        // add any attributes that didn't replace previous attributes

        cv.finish();

        return cw.toByteArray();

    }

    /**

     * Returns an {@code Extender} that may be used to add additional

     * attributes to the module-info.class read from the given input

     * stream.

     */

    public static ModuleInfoExtender newExtender(InputStream in) {

        return new ModuleInfoExtender(in);

    }

}