/*
 * 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.compressors.gzip;

import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.util.LinkedHashMap;
import java.util.Map;

import org.apache.commons.compress.compressors.FileNameUtil;

/**
 * Utility code for the gzip compression format.
 * @ThreadSafe
 */
public class GzipUtils {

    private static final FileNameUtil fileNameUtil;

    static {
        // using LinkedHashMap so .tgz is preferred over .taz as
        // compressed extension of .tar as FileNameUtil will use the
        // first one found
        final Map<String, String> uncompressSuffix =
            new LinkedHashMap<>();
        uncompressSuffix.put(".tgz", ".tar");
        uncompressSuffix.put(".taz", ".tar");
        uncompressSuffix.put(".svgz", ".svg");
        uncompressSuffix.put(".cpgz", ".cpio");
        uncompressSuffix.put(".wmz", ".wmf");
        uncompressSuffix.put(".emz", ".emf");
        uncompressSuffix.put(".gz", "");
        uncompressSuffix.put(".z", "");
        uncompressSuffix.put("-gz", "");
        uncompressSuffix.put("-z", "");
        uncompressSuffix.put("_z", "");
        fileNameUtil = new FileNameUtil(uncompressSuffix, ".gz");
    }

    /**
     * Encoding for file name and comments per the <a href="https://tools.ietf.org/html/rfc1952">GZIP File Format Specification</a>
     */
    static final Charset GZIP_ENCODING = StandardCharsets.ISO_8859_1;

    /**
     * Maps the given file name to the name that the file should have after
     * compression with gzip. Common file types with custom suffixes for
     * compressed versions are automatically detected and correctly mapped.
     * For example the name "package.tar" is mapped to "package.tgz". If no
     * custom mapping is applicable, then the default ".gz" suffix is appended
     * to the file name.
     *
     * @param fileName name of a file
     * @return name of the corresponding compressed file
     */
    public static String getCompressedFilename(final String fileName) {
        return fileNameUtil.getCompressedFilename(fileName);
    }

    /**
     * Maps the given name of a gzip-compressed file to the name that the
     * file should have after uncompression. Commonly used file type specific
     * suffixes like ".tgz" or ".svgz" are automatically detected and
     * correctly mapped. For example the name "package.tgz" is mapped to
     * "package.tar". And any file names with the generic ".gz" suffix
     * (or any other generic gzip suffix) is mapped to a name without that
     * suffix. If no gzip suffix is detected, then the file name is returned
     * unmapped.
     *
     * @param fileName name of a file
     * @return name of the corresponding uncompressed file
     */
    public static String getUncompressedFilename(final String fileName) {
        return fileNameUtil.getUncompressedFilename(fileName);
    }

    /**
     * Detects common gzip suffixes in the given file name.
     *
     * @param fileName name of a file
     * @return {@code true} if the file name has a common gzip suffix,
     *         {@code false} otherwise
     */
    public static boolean isCompressedFilename(final String fileName) {
        return fileNameUtil.isCompressedFilename(fileName);
    }

    /** Private constructor to prevent instantiation of this utility class. */
    private GzipUtils() {
    }

}
