//  Copyright (C) 2015, The Duplicati Team
//  http://www.duplicati.com, info@duplicati.com
//
//  This library is free software; you can redistribute it and/or modify
//  it under the terms of the GNU Lesser General Public License as
//  published by the Free Software Foundation; either version 2.1 of the
//  License, or (at your option) any later version.
//
//  This library 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
//  Lesser General Public License for more details.
//
//  You should have received a copy of the GNU Lesser General Public
//  License along with this library; if not, write to the Free Software
//  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
using System;
using System.IO;
using Duplicati.Library.Utility;
using System.Collections.Generic;
namespace Duplicati.Library.Main.Operation
{
    public class RestoreHandlerMetadataStorage : IDisposable
    {
        private TempFile m_temp;
        private FileStream m_stream;
        private long m_entries;

        private long m_filepos;
        public RestoreHandlerMetadataStorage()
        {
            m_temp = new TempFile();
            m_stream = File.Open(m_temp, FileMode.Truncate, FileAccess.ReadWrite, FileShare.None);
        }

        public void Add(string path, Stream data)
        {
            var datalen = data.Length;

            if (datalen > Int32.MaxValue)
                throw new ArgumentOutOfRangeException("Metadata is larger than int32");

            var pathbytes = System.Text.Encoding.UTF8.GetBytes(path);
            var pathlen = BitConverter.GetBytes(pathbytes.LongLength);
            var entrylen = BitConverter.GetBytes(datalen);

            var totalsize = pathbytes.Length + pathlen.Length + entrylen.Length + datalen;

            m_stream.Position = m_filepos;
            m_stream.Write(pathlen, 0, pathlen.Length);
            m_stream.Write(pathbytes, 0, pathbytes.Length);
            m_stream.Write(entrylen, 0, entrylen.Length);
            data.CopyTo(m_stream);


            if (m_stream.Position != m_filepos + totalsize)
                throw new Exception("Bad file write!");

            m_filepos += totalsize;
            m_entries++;
        }

        private void CheckedRead(byte[] buffer, int offset, int count)
        {
            int r;
            while (count > 0 && (r = m_stream.Read(buffer, offset, count)) > 0)
            {
                offset += r;
                count -= r;
            }

            if (count != 0)
                throw new Exception("Bad file read");
        }

        public IEnumerable<KeyValuePair<string, Stream>> Records
        {
            get
            {
                long pos = 0;
                var bf = BitConverter.GetBytes(0L);
                var buf = new byte[8 * 1024];

                Logging.Log.WriteMessage(string.Format("The metadata storage file has {0} entries and takes up {1}", m_entries, Library.Utility.Utility.FormatSizeString(m_stream.Length)), Duplicati.Library.Logging.LogMessageType.Profiling);

                using(new Logging.Timer("Read metadata from file"))
                    for(var e = 0L; e < m_entries; e++)
                    {
                        m_stream.Position = pos;
                        CheckedRead(bf, 0, bf.Length);
                        var stringlen = BitConverter.ToInt64(bf, 0);

                        var strbuf = stringlen > buf.Length ? new byte[stringlen] : buf;
                        CheckedRead(strbuf, 0, (int)stringlen);
                        var path = System.Text.Encoding.UTF8.GetString(strbuf, 0, (int)stringlen);

                        CheckedRead(bf, 0, bf.Length);
                        var datalen = BitConverter.ToInt64(bf, 0);
                        if (datalen > Int32.MaxValue)
                            throw new ArgumentOutOfRangeException("Metadata is larger than int32");

                        var databuf = datalen > buf.Length ? new byte[datalen] : buf;
                        CheckedRead(databuf, 0, (int)datalen);

                        pos += datalen + stringlen + bf.Length + bf.Length;

                        yield return new KeyValuePair<string, Stream>(path, new MemoryStream(databuf, 0, (int)datalen));

                    }
            }
        }

        #region IDisposable implementation

        public void Dispose()
        {
            if (m_stream != null)
                try { m_stream.Dispose(); }
                catch { }
                finally { m_stream = null; }

            if (m_temp != null)
                try { m_temp.Dispose(); }
                catch { }
                finally { m_temp = null; }

        }

        #endregion
    }
}