/*

 * Copyright (c) 2019, 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.tools.jlink.internal.plugins;

import java.io.*;

import java.nio.charset.*;

import java.util.*;

import java.util.function.*;

import java.util.stream.*;

import jdk.tools.jlink.plugin.*;

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

import static java.lang.System.out;

/**

 * Base plugin to update a static field in java.lang.VersionProps

 */

abstract class VersionPropsPlugin implements Plugin {

    private static final String VERSION_PROPS_CLASS

        = "/java.base/java/lang/VersionProps.class";

    private final String name;

    private final String field;

    private String value;

    /**

     * @param field The name of the java.lang.VersionProps field to be redefined

     * @param option The option name

     */

    protected VersionPropsPlugin(String field, String option) {

        this.field = field;

        this.name = option;

    }

    /**

     * Shorthand constructor for when the option name can be derived from the

     * name of the field.

     *

     * @param field The name of the java.lang.VersionProps field to be redefined

     */

    protected VersionPropsPlugin(String field) {

        this(field, field.toLowerCase().replace('_', '-'));

    }

    @Override

    public String getName() {

        return name;

    }

    @Override

    public String getDescription() {

        return PluginsResourceBundle.getDescription(name);

    }

    @Override

    public Category getType() {

        return Category.TRANSFORMER;

    }

    @Override

    public boolean hasArguments() {

        return true;

    }

    @Override

    public boolean hasRawArgument() {

        return true;

    }

    @Override

    public String getArgumentsDescription() {

       return PluginsResourceBundle.getArgument(name);

    }

    @Override

    public void configure(Map<String, String> config) {

        var v = config.get(name);

        if (v == null)

            throw new AssertionError();

        value = v;

    }

    private boolean redefined = false;

    private byte[] redefine(byte[] classFile) {

        var cr = new ClassReader(classFile);

        var cw = new ClassWriter(0);

        cr.accept(new ClassVisitor(Opcodes.ASM7, cw) {

                public MethodVisitor visitMethod(int access,

                                                 String name,

                                                 String desc,

                                                 String sig,

                                                 String[] xs)

                {

                    if (name.equals("<clinit>"))

                        return new MethodVisitor(Opcodes.ASM7,

                                                 super.visitMethod(access,

                                                                   name,

                                                                   desc,

                                                                   sig,

                                                                   xs))

                            {

                                public void visitFieldInsn(int opcode,

                                                           String owner,

                                                           String name,

                                                           String desc)

                                {

                                    if (opcode == Opcodes.PUTSTATIC

                                        && name.equals(field))

                                    {

                                        // Discard the original value

                                        super.visitInsn(Opcodes.POP);

                                        // Load the value that we want

                                        super.visitLdcInsn(value);

                                        redefined = true;

                                    }

                                    super.visitFieldInsn(opcode, owner,

                                                         name, desc);

                                }

                        };

                    else

                        return super.visitMethod(access, name, desc, sig, xs);

                }

            }, 0);

        return cw.toByteArray();

    }

    @Override

    public ResourcePool transform(ResourcePool in, ResourcePoolBuilder out) {

        in.transformAndCopy(res -> {

                if (res.type().equals(ResourcePoolEntry.Type.CLASS_OR_RESOURCE)) {

                    if (res.path().equals(VERSION_PROPS_CLASS)) {

                        return res.copyWithContent(redefine(res.contentBytes()));

                    }

                }

                return res;

            }, out);

        if (!redefined)

            throw new AssertionError(field);

        return out.build();

    }

}