/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 */

package org.apache.commons.compress.archivers.zip;

import java.io.File;
import java.io.IOException;
import java.io.Serializable;
import java.nio.ByteBuffer;
import java.nio.channels.SeekableByteChannel;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.StandardOpenOption;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
import java.util.Objects;
import java.util.regex.Pattern;
import java.util.stream.Collectors;
import java.util.stream.Stream;

import org.apache.commons.compress.archivers.ArchiveStreamFactory;
import org.apache.commons.compress.utils.FileNameUtils;
import org.apache.commons.compress.utils.MultiReadOnlySeekableByteChannel;

/**
 * {@link MultiReadOnlySeekableByteChannel} that knows what a split ZIP archive should look like.
 *
 * <p>If you want to read a split archive using {@link ZipFile} then create an instance of this class from the parts of
 * the archive.</p>
 *
 * @since 1.20
 */
public class ZipSplitReadOnlySeekableByteChannel extends MultiReadOnlySeekableByteChannel {

    private static final Path[] EMPTY_PATH_ARRAY = {};
    private static final int ZIP_SPLIT_SIGNATURE_LENGTH = 4;
    private final ByteBuffer zipSplitSignatureByteBuffer =
        ByteBuffer.allocate(ZIP_SPLIT_SIGNATURE_LENGTH);

    /**
     * Concatenates the given channels.
     *
     * <p>The channels should be add in ascending order, e.g. z01,
     * z02, ... z99, zip please note that the .zip file is the last
     * segment and should be added as the last one in the channels</p>
     *
     * @param channels the channels to concatenate
     * @throws NullPointerException if channels is null
     * @throws IOException if the first channel doesn't seem to hold
     * the beginning of a split archive
     */
    public ZipSplitReadOnlySeekableByteChannel(final List<SeekableByteChannel> channels)
        throws IOException {
        super(channels);

        // the first split zip segment should begin with zip split signature
        assertSplitSignature(channels);
    }

    /**
     * Based on the zip specification:
     *
     * <p>
     * 8.5.3 Spanned/Split archives created using PKZIP for Windows
     * (V2.50 or greater), PKZIP Command Line (V2.50 or greater),
     * or PKZIP Explorer will include a special spanning
     * signature as the first 4 bytes of the first segment of
     * the archive.  This signature (0x08074b50) will be
     * followed immediately by the local header signature for
     * the first file in the archive.
     *
     * <p>
     * the first 4 bytes of the first zip split segment should be the zip split signature(0x08074B50)
     *
     * @param channels channels to be validated
     * @throws IOException
     */
    private void assertSplitSignature(final List<SeekableByteChannel> channels)
        throws IOException {
        final SeekableByteChannel channel = channels.get(0);
        // the zip split file signature is at the beginning of the first split segment
        channel.position(0L);

        zipSplitSignatureByteBuffer.rewind();
        channel.read(zipSplitSignatureByteBuffer);
        final ZipLong signature = new ZipLong(zipSplitSignatureByteBuffer.array());
        if (!signature.equals(ZipLong.DD_SIG)) {
            channel.position(0L);
            throw new IOException("The first zip split segment does not begin with split zip file signature");
        }

        channel.position(0L);
    }

    /**
     * Concatenates the given channels.
     *
     * @param channels the channels to concatenate, note that the LAST CHANNEL of channels should be the LAST SEGMENT(.zip)
     *                 and theses channels should be added in correct order (e.g. .z01, .z02... .z99, .zip)
     * @return SeekableByteChannel that concatenates all provided channels
     * @throws NullPointerException if channels is null
     * @throws IOException if reading channels fails
     */
    public static SeekableByteChannel forOrderedSeekableByteChannels(final SeekableByteChannel... channels) throws IOException {
        if (Objects.requireNonNull(channels, "channels must not be null").length == 1) {
            return channels[0];
        }
        return new ZipSplitReadOnlySeekableByteChannel(Arrays.asList(channels));
    }

    /**
     * Concatenates the given channels.
     *
     * @param lastSegmentChannel channel of the last segment of split zip segments, its extension should be .zip
     * @param channels           the channels to concatenate except for the last segment,
     *                           note theses channels should be added in correct order (e.g. .z01, .z02... .z99)
     * @return SeekableByteChannel that concatenates all provided channels
     * @throws NullPointerException if lastSegmentChannel or channels is null
     * @throws IOException if the first channel doesn't seem to hold
     * the beginning of a split archive
     */
    public static SeekableByteChannel forOrderedSeekableByteChannels(final SeekableByteChannel lastSegmentChannel,
        final Iterable<SeekableByteChannel> channels) throws IOException {
        Objects.requireNonNull(channels, "channels");
        Objects.requireNonNull(lastSegmentChannel, "lastSegmentChannel");

        final List<SeekableByteChannel> channelsList = new ArrayList<>();
        channels.forEach(channelsList::add);
        channelsList.add(lastSegmentChannel);

        return forOrderedSeekableByteChannels(channelsList.toArray(new SeekableByteChannel[0]));
    }

    /**
     * Concatenates zip split files from the last segment(the extension SHOULD be .zip)
     *
     * @param lastSegmentFile the last segment of zip split files, note that the extension SHOULD be .zip
     * @return SeekableByteChannel that concatenates all zip split files
     * @throws IllegalArgumentException if the lastSegmentFile's extension is NOT .zip
     * @throws IOException if the first channel doesn't seem to hold
     * the beginning of a split archive
     */
    public static SeekableByteChannel buildFromLastSplitSegment(final File lastSegmentFile) throws IOException {
        return buildFromLastSplitSegment(lastSegmentFile.toPath());
    }

    /**
     * Concatenates zip split files from the last segment (the extension MUST be .zip)
     * @param lastSegmentPath the last segment of zip split files, note that the extension MUST be .zip
     * @return SeekableByteChannel that concatenates all zip split files
     * @throws IllegalArgumentException if the lastSegmentPath's extension is NOT .zip
     * @throws IOException if the first channel doesn't seem to hold
     * the beginning of a split archive
     * @since 1.22
     */
    public static SeekableByteChannel buildFromLastSplitSegment(final Path lastSegmentPath) throws IOException {
        final String extension = FileNameUtils.getExtension(lastSegmentPath);
        if (!extension.equalsIgnoreCase(ArchiveStreamFactory.ZIP)) {
            throw new IllegalArgumentException("The extension of last zip split segment should be .zip");
        }

        final Path parent = Objects.nonNull(lastSegmentPath.getParent()) ? lastSegmentPath.getParent()
                : lastSegmentPath.getFileSystem().getPath(".");
        final String fileBaseName = FileNameUtils.getBaseName(lastSegmentPath);
        final ArrayList<Path> splitZipSegments;

        // zip split segments should be like z01,z02....z(n-1) based on the zip specification
        final Pattern pattern = Pattern.compile(Pattern.quote(fileBaseName) + ".[zZ][0-9]+");
        try (Stream<Path> walk = Files.walk(parent, 1)) {
            splitZipSegments = walk
                    .filter(Files::isRegularFile)
                    .filter(path -> pattern.matcher(path.getFileName().toString()).matches())
                    .sorted(new ZipSplitSegmentComparator())
                    .collect(Collectors.toCollection(ArrayList::new));
        }

        return forPaths(lastSegmentPath, splitZipSegments);
    }

    /**
     * Concatenates the given files.
     *
     * @param files the files to concatenate, note that the LAST FILE of files should be the LAST SEGMENT(.zip)
     *              and theses files should be added in correct order (e.g. .z01, .z02... .z99, .zip)
     * @return SeekableByteChannel that concatenates all provided files
     * @throws NullPointerException if files is null
     * @throws IOException          if opening a channel for one of the files fails
     * @throws IOException if the first channel doesn't seem to hold
     * the beginning of a split archive
     */
    public static SeekableByteChannel forFiles(final File... files) throws IOException {
        final List<Path> paths = new ArrayList<>();
        for (final File f : Objects.requireNonNull(files, "files must not be null")) {
            paths.add(f.toPath());
        }

        return forPaths(paths.toArray(EMPTY_PATH_ARRAY));
    }

    /**
     * Concatenates the given file paths.
     * @param paths the file paths to concatenate, note that the LAST FILE of files should be the LAST SEGMENT(.zip)
     * and these files should be added in correct order (e.g.: .z01, .z02... .z99, .zip)
     * @return SeekableByteChannel that concatenates all provided files
     * @throws NullPointerException if files is null
     * @throws IOException if opening a channel for one of the files fails
     * @throws IOException if the first channel doesn't seem to hold
     * the beginning of a split archive
     * @since 1.22
     */
    public static SeekableByteChannel forPaths(final Path... paths) throws IOException {
        final List<SeekableByteChannel> channels = new ArrayList<>();
        for (final Path path : Objects.requireNonNull(paths, "paths must not be null")) {
            channels.add(Files.newByteChannel(path, StandardOpenOption.READ));
        }
        if (channels.size() == 1) {
            return channels.get(0);
        }
        return new ZipSplitReadOnlySeekableByteChannel(channels);
    }

    /**
     * Concatenates the given files.
     *
     * @param lastSegmentFile the last segment of split zip segments, its extension should be .zip
     * @param files           the files to concatenate except for the last segment,
     *                        note theses files should be added in correct order (e.g. .z01, .z02... .z99)
     * @return SeekableByteChannel that concatenates all provided files
     * @throws IOException if the first channel doesn't seem to hold
     * the beginning of a split archive
     * @throws NullPointerException if files or lastSegmentFile is null
     */
    public static SeekableByteChannel forFiles(final File lastSegmentFile, final Iterable<File> files) throws IOException {
        Objects.requireNonNull(files, "files");
        Objects.requireNonNull(lastSegmentFile, "lastSegmentFile");

        final List<Path> filesList = new ArrayList<>();
        files.forEach(f -> filesList.add(f.toPath()));

        return forPaths(lastSegmentFile.toPath(), filesList);
    }

    /**
     * Concatenates the given file paths.
     * @param lastSegmentPath the last segment path of split zip segments, its extension must be .zip
     * @param paths the file paths to concatenate except for the last segment,
     * note these files should be added in correct order (e.g.: .z01, .z02... .z99)
     * @return SeekableByteChannel that concatenates all provided files
     * @throws IOException if the first channel doesn't seem to hold
     * the beginning of a split archive
     * @throws NullPointerException if files or lastSegmentPath is null
     * @since 1.22
     */
    public static SeekableByteChannel forPaths(final Path lastSegmentPath, final Iterable<Path> paths) throws IOException {
        Objects.requireNonNull(paths, "paths");
        Objects.requireNonNull(lastSegmentPath, "lastSegmentPath");

        final List<Path> filesList = new ArrayList<>();
        paths.forEach(filesList::add);
        filesList.add(lastSegmentPath);

        return forPaths(filesList.toArray(EMPTY_PATH_ARRAY));
    }

    private static class ZipSplitSegmentComparator implements Comparator<Path>, Serializable {
        private static final long serialVersionUID = 20200123L;

        @Override
        public int compare(final Path file1, final Path file2) {
            final String extension1 = FileNameUtils.getExtension(file1);
            final String extension2 = FileNameUtils.getExtension(file2);

            if (!extension1.startsWith("z")) {
                return -1;
            }

            if (!extension2.startsWith("z")) {
                return 1;
            }

            final Integer splitSegmentNumber1 = Integer.parseInt(extension1.substring(1));
            final Integer splitSegmentNumber2 = Integer.parseInt(extension2.substring(1));

            return splitSegmentNumber1.compareTo(splitSegmentNumber2);
        }
    }
}