/*
 * Copyright (c) Contributors, http://opensimulator.org/
 * See CONTRIBUTORS.TXT for a full list of copyright holders.
 *
 * 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.
 *     * Neither the name of the OpenSim Project nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``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 CONTRIBUTORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

using System;
using System.Collections.Generic;
using System.IO;
using System.Text;
using System.Reflection;
using log4net;

namespace OpenSim.Region.Environment
{
    /// <summary>
    /// Temporary code to produce a tar archive in tar v7 format
    /// </summary>
    public class TarArchiveWriter
    {
        private static readonly ILog m_log = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);

        protected Dictionary<string, byte[]> m_files = new Dictionary<string, byte[]>();

        protected static System.Text.ASCIIEncoding m_asciiEncoding = new System.Text.ASCIIEncoding();

        /// <summary>
        /// Add a directory to the tar archive.  We can only handle one path level right now!
        /// </summary>
        /// <param name="dirName"></param>
        public void AddDir(string dirName)
        {
            // Directories are signalled by a final /
            if (!dirName.EndsWith("/"))
                dirName += "/";
            
            AddFile(dirName, new byte[0]);
        }
        
        /// <summary>
        /// Add a file to the tar archive
        /// </summary>
        /// <param name="filePath"></param>
        /// <param name="data"></param>
        public void AddFile(string filePath, string data)
        {
            AddFile(filePath, m_asciiEncoding.GetBytes(data));
        }

        /// <summary>
        /// Add a file to the tar archive
        /// </summary>
        /// <param name="filePath"></param>
        /// <param name="data"></param>
        public void AddFile(string filePath, byte[] data)
        {
            m_files[filePath] = data;
        }

        /// <summary>
        /// Write the raw tar archive data to a file
        /// </summary>
        /// <returns></returns>
        public void WriteTar(string archivePath)
        {
            BinaryWriter bw = new BinaryWriter(new FileStream(archivePath, FileMode.Create));

            foreach (string filePath in m_files.Keys)
            {
                byte[] header = new byte[512];
                byte[] data = m_files[filePath];

                //string filePath = "test.txt";
                //byte[] data = m_asciiEncoding.GetBytes("hello\n");

                // file path field (100)
                byte[] nameBytes = m_asciiEncoding.GetBytes(filePath);
                int nameSize = (nameBytes.Length >= 100) ? 100 : nameBytes.Length;
                Array.Copy(nameBytes, header, nameSize);

                // file mode (8)
                byte[] modeBytes = m_asciiEncoding.GetBytes("0000755");
                Array.Copy(modeBytes, 0, header, 100, 7);

                // owner user id (8)
                byte[] ownerIdBytes = m_asciiEncoding.GetBytes("0000764");
                Array.Copy(ownerIdBytes, 0, header, 108, 7);

                // group user id (8)
                byte[] groupIdBytes = m_asciiEncoding.GetBytes("0000764");
                Array.Copy(groupIdBytes, 0, header, 116, 7);

                // file size in bytes (12)
                int fileSize = data.Length;
                m_log.DebugFormat("[TAR ARCHIVE WRITER]: File size of {0} is {1}", filePath, fileSize);

                byte[] fileSizeBytes = ConvertDecimalToPaddedOctalBytes(fileSize, 11);

                Array.Copy(fileSizeBytes, 0, header, 124, 11);

                // last modification time (12)
                byte[] lastModTimeBytes = m_asciiEncoding.GetBytes("11017037332");
                Array.Copy(lastModTimeBytes, 0, header, 136, 11);

                // link indicator (1)
                //header[156] = m_asciiEncoding.GetBytes("0")[0];
                if (filePath.EndsWith("/"))
                {
                    header[156] = m_asciiEncoding.GetBytes("5")[0];
                }
                else
                {
                    header[156] = 0;
                }

                Array.Copy(m_asciiEncoding.GetBytes("0000000"), 0, header, 329, 7);
                Array.Copy(m_asciiEncoding.GetBytes("0000000"), 0, header, 337, 7);

                // check sum for header block (8) [calculated last]
                Array.Copy(m_asciiEncoding.GetBytes("        "), 0, header, 148, 8);

                int checksum = 0;
                foreach (byte b in header)
                {
                    checksum += b;
                }

                m_log.DebugFormat("[TAR ARCHIVE WRITER]: Decimal header checksum is {0}", checksum);

                byte[] checkSumBytes = ConvertDecimalToPaddedOctalBytes(checksum, 6);
                //byte[] checkSumBytes = m_asciiEncoding.GetBytes("007520");

                Array.Copy(checkSumBytes, 0, header, 148, 6);

                header[154] = 0;

                // Write out header
                bw.Write(header);

                // Write out data
                bw.Write(data);

                if (data.Length % 512 != 0)
                {
                    int paddingRequired = 512 - (data.Length % 512);
                    
                    m_log.DebugFormat("[TAR ARCHIVE WRITER]: Padding data with {0} bytes", paddingRequired);

                    byte[] padding = new byte[paddingRequired];
                    bw.Write(padding);
                }
            }

            // Write two consecutive 0 blocks to end the archive
            byte[] finalZeroPadding = new byte[1024];
            bw.Write(finalZeroPadding);

            bw.Close();
        }

        public static byte[] ConvertDecimalToPaddedOctalBytes(int d, int padding)
        {
            string oString = "";

            while (d > 0)
            {
                oString = Convert.ToString((byte)'0' + d & 7) + oString;
                d >>= 3;
            }

            while (oString.Length < padding)
            {
                oString = "0" + oString;
            }

            byte[] oBytes = m_asciiEncoding.GetBytes(oString);

            return oBytes;
        }
    }
}