/*
 * 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);
    }

}