/*

 * Copyright (c) 2015, 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.

 *

 * 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.

 */

import java.io.IOException;

import java.io.OutputStream;

import java.nio.file.Files;

import java.nio.file.Paths;

import java.util.ArrayList;

import java.util.List;

import java.util.jar.Attributes;

import java.util.jar.JarEntry;

import java.util.jar.JarOutputStream;

import java.util.jar.Manifest;

public class JarBuilder {

    final private String name;

    final private Attributes attributes = new Attributes();

    final private List<Entry> entries = new ArrayList<>();

    public JarBuilder(String name) {

        this.name = name;

        attributes.putValue("Manifest-Version", "1.0");

        attributes.putValue("Created-By", "1.9.0-internal (Oracle Corporation)");

    }

    public JarBuilder addAttribute(String name, String value) {

        attributes.putValue(name, value);

        return this;

    }

    public JarBuilder addEntry(String name, byte[] bytes) {

        entries.add(new Entry(name, bytes));

        return this;

    }

    public void build() throws IOException {

        try (OutputStream os = Files.newOutputStream(Paths.get(name));

             JarOutputStream jos = new JarOutputStream(os)) {

            JarEntry me = new JarEntry("META-INF/MANIFEST.MF");

            jos.putNextEntry(me);

            Manifest manifest = new Manifest();

            manifest.getMainAttributes().putAll(attributes);

            manifest.write(jos);

            jos.closeEntry();

            entries.forEach(e -> {

                JarEntry je = new JarEntry(e.name);

                try {

                    jos.putNextEntry(je);

                    jos.write(e.bytes);

                    jos.closeEntry();

                } catch (IOException iox) {

                    throw new RuntimeException(iox);

                }

            });

        } catch (RuntimeException x) {

            Throwable t = x.getCause();

            if (t instanceof IOException) {

                IOException iox = (IOException)t;

                throw iox;

            }

            throw x;

        }

    }

    private static class Entry {

        String name;

        byte[] bytes;

        Entry(String name, byte[] bytes) {

            this.name = name;

            this.bytes = bytes;

        }

    }

    public static void main(String[] args) throws IOException {

        JarBuilder jb = new JarBuilder("version.jar");

        jb.addAttribute("Multi-Release", "true");

        String s = "something to say";

        byte[] bytes = s.getBytes();

        jb.addEntry("version/Version.class", bytes);

        jb.addEntry("README", bytes);

        jb.addEntry("version/Version.java", bytes);

        jb.build();

    }

}