/*

 * 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.List;

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.ModuleVisitor;

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

import jdk.internal.org.objectweb.asm.commons.ModuleHashesAttribute;

import jdk.internal.org.objectweb.asm.commons.ModuleResolutionAttribute;

import jdk.internal.org.objectweb.asm.commons.ModuleTargetAttribute;

/**

 * 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;

    }

    /**

     * 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);

        ClassReader cr = new ClassReader(in);

        ClassVisitor cv = new ClassVisitor(Opcodes.ASM6, cw) {

            @Override

            public ModuleVisitor visitModule(String name, int flags, String version) {

                Version v = ModuleInfoExtender.this.version;

                String vs = (v != null) ? v.toString() : version;

                ModuleVisitor mv = super.visitModule(name, flags, vs);

                // ModuleMainClass attribute

                if (mainClass != null) {

                    mv.visitMainClass(mainClass.replace('.', '/'));

                }

                // ModulePackages attribute

                if (packages != null) {

                    packages.forEach(pn -> mv.visitPackage(pn.replace('.', '/')));

                }

                return new ModuleVisitor(Opcodes.ASM6, mv) {

                    public void visitMainClass(String existingMainClass) {

                        // skip main class if there is a new value

                        if (mainClass == null) {

                            super.visitMainClass(existingMainClass);

                        }

                    }

                    public void visitPackage(String existingPackage) {

                        // skip packages if there is a new set of packages

                        if (packages == null) {

                            super.visitPackage(existingPackage);

                        }

                    }

                };

            }

            @Override

            public void visitAttribute(Attribute attr) {

                String name = attr.type;

                // drop existing attributes if there are replacements

                if (name.equals(ClassFileConstants.MODULE_TARGET)

                    && targetPlatform != null)

                    return;

                if (name.equals(ClassFileConstants.MODULE_RESOLUTION)

                    && moduleResolution != null)

                    return;

                if (name.equals(ClassFileConstants.MODULE_HASHES)

                    && hashes != null)

                    return;

                super.visitAttribute(attr);

            }

        };

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

        attrs.add(new ModuleTargetAttribute());

        attrs.add(new ModuleResolutionAttribute());

        attrs.add(new ModuleHashesAttribute());

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

        // add ModuleTarget, ModuleResolution and ModuleHashes attributes

        if (targetPlatform != null) {

            cw.visitAttribute(new ModuleTargetAttribute(targetPlatform));

        }

        if (moduleResolution != null) {

            int flags = moduleResolution.value();

            cw.visitAttribute(new ModuleResolutionAttribute(flags));

        }

        if (hashes != null) {

            String algorithm = hashes.algorithm();

            List<String> names = new ArrayList<>();

            List<byte[]> values = new ArrayList<>();

            for (String name : hashes.names()) {

                names.add(name);

                values.add(hashes.hashFor(name));

            }

            cw.visitAttribute(new ModuleHashesAttribute(algorithm, names, values));

        }

        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);

    }

}