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 * 
 * Redistribution and use in source and binary forms, 
 * with or without modification, are permitted provided 
 * that the following conditions are met: 
 * 
 * *   Redistributions of source code must retain the above 
 *     copyright notice, this list of conditions and the 
 *     following disclaimer. 
 * *   Redistributions in binary form must reproduce the above 
 *     copyright notice, this list of conditions and the 
 *     following disclaimer in the documentation and/or other 
 *     materials provided with the distribution. 
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND 
 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, 
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR 
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 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 
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 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 
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 */

using System.IO;
using System;

namespace XenCenterLib.Compression
{
    /// <summary>
    /// A static factory to create an object that will allow the archiving of data
    /// </summary>
    public static class CompressionFactory
    {
        /// <summary>
        /// Type of compressed stream
        /// </summary>
        public enum Type
        {
            Gz
        }

        public static string StringOf(this Type t)
        {
            switch (t)
            {
                case Type.Gz:
                    return "Gzip";
                default:
                    throw new ArgumentOutOfRangeException(nameof(t), t, null);
            }
        }

        public static string FileExtension(this Type t)
        {
            switch (t)
            {
                case Type.Gz:
                    return ".gz";
                default:
                    throw new ArgumentOutOfRangeException(nameof(t), t, null);
            }
        }

        /// <summary>
        /// Instantiate a class that can decompress a data stream type
        /// </summary>
        /// <param name="compressionType">Type of compressed stream to read</param>
        /// <param name="compressedDataSource">The contents of compressed data</param>
        /// <exception cref="NotSupportedException">If there is not a compressor for a specified archive type</exception>
        /// <returns>CompressionStream to allow an read as a stream</returns>
        public static CompressionStream Reader(Type compressionType, Stream compressedDataSource)
        {
            if (compressionType == Type.Gz)
                return new GZipInputStream(compressedDataSource);

            throw new NotSupportedException(String.Format("Type: {0} is not supported by CompressionStream Reader", compressionType));
        }

        /// <summary>
        /// Instantiate a class that can compress a data stream type
        /// </summary>
        /// <param name="compressionType">Type of compressed stream to write</param>
        /// <param name="compressedDataTarget">The place where the compressed data will be put</param>
        /// <exception cref="NotSupportedException"> if there is not a compressor for a specified archive type</exception>
        /// <returns>CompressionStream to allow an write as a stream</returns>
        public static CompressionStream Writer(Type compressionType, Stream compressedDataTarget)
        {
            if (compressionType == Type.Gz)
                return new GZipOutputStream(compressedDataTarget);

            throw new NotSupportedException(String.Format("Type: {0} is not supported by CompressionStream Writer", compressionType));
        }

        public static void UncompressFile(string inputFile, string outputFile, Type method, Action cancellingDelegate = null)
        {
            using (var inputStream = new FileStream(inputFile, FileMode.Open, FileAccess.ReadWrite, FileShare.None))
            using (var outputStream = new FileStream(outputFile, FileMode.CreateNew, FileAccess.ReadWrite, FileShare.None))
            {
                using (var uncompressedStream = Reader(method, inputStream))
                    StreamCopy(uncompressedStream, outputStream, cancellingDelegate);
            }
        }

        public static void CompressFile(string inputFile, string outputFile, Type method, Action cancellingDelegate = null)
        {
            using (var inputStream = new FileStream(inputFile, FileMode.Open, FileAccess.ReadWrite, FileShare.None))
            using (var outputStream = new FileStream(outputFile, FileMode.CreateNew, FileAccess.ReadWrite, FileShare.None))
            {
                using (var compressedStream = Writer(method, outputStream))
                    StreamCopy(inputStream, compressedStream, cancellingDelegate);
            }
        }

        private static void StreamCopy(Stream input, Stream output, Action cancellingDelegate = null)
        {
            byte[] block = new byte[2 * 1024 * 1024];

            int n;
            while ((n = input.Read(block, 0, block.Length)) > 0)
            {
                cancellingDelegate?.Invoke();
                output.Write(block, 0, n);
            }

            output.Flush();
        }
    }
}