// /***************************************************************************
// Aaru Data Preservation Suite
// ----------------------------------------------------------------------------
//
// Filename       : Read.cs
// Author(s)      : Natalia Portillo <claunia@claunia.com>
//
// Component      : Disk image plugins.
//
// --[ Description ] ----------------------------------------------------------
//
//     Reads QEMU Copy-On-Write disk images.
//
// --[ License ] --------------------------------------------------------------
//
//     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, see <http://www.gnu.org/licenses/>.
//
// ----------------------------------------------------------------------------
// Copyright © 2011-2021 Natalia Portillo
// ****************************************************************************/

using System;
using System.Collections.Generic;
using System.IO;
using System.Runtime.InteropServices;
using Aaru.CommonTypes;
using Aaru.CommonTypes.Enums;
using Aaru.CommonTypes.Interfaces;
using Aaru.Console;
using Aaru.Helpers;
using SharpCompress.Compressors;
using SharpCompress.Compressors.Deflate;
using Marshal = Aaru.Helpers.Marshal;

namespace Aaru.DiscImages
{
    public sealed partial class Qcow
    {
        /// <inheritdoc />
        public ErrorNumber Open(IFilter imageFilter)
        {
            Stream stream = imageFilter.GetDataForkStream();
            stream.Seek(0, SeekOrigin.Begin);

            if(stream.Length < 512)
                return ErrorNumber.InvalidArgument;

            byte[] qHdrB = new byte[48];
            stream.Read(qHdrB, 0, 48);
            _qHdr = Marshal.SpanToStructureBigEndian<Header>(qHdrB);

            AaruConsole.DebugWriteLine("QCOW plugin", "qHdr.magic = 0x{0:X8}", _qHdr.magic);
            AaruConsole.DebugWriteLine("QCOW plugin", "qHdr.version = {0}", _qHdr.version);
            AaruConsole.DebugWriteLine("QCOW plugin", "qHdr.backing_file_offset = {0}", _qHdr.backing_file_offset);
            AaruConsole.DebugWriteLine("QCOW plugin", "qHdr.backing_file_size = {0}", _qHdr.backing_file_size);
            AaruConsole.DebugWriteLine("QCOW plugin", "qHdr.mtime = {0}", _qHdr.mtime);
            AaruConsole.DebugWriteLine("QCOW plugin", "qHdr.size = {0}", _qHdr.size);
            AaruConsole.DebugWriteLine("QCOW plugin", "qHdr.cluster_bits = {0}", _qHdr.cluster_bits);
            AaruConsole.DebugWriteLine("QCOW plugin", "qHdr.l2_bits = {0}", _qHdr.l2_bits);
            AaruConsole.DebugWriteLine("QCOW plugin", "qHdr.padding = {0}", _qHdr.padding);
            AaruConsole.DebugWriteLine("QCOW plugin", "qHdr.crypt_method = {0}", _qHdr.crypt_method);
            AaruConsole.DebugWriteLine("QCOW plugin", "qHdr.l1_table_offset = {0}", _qHdr.l1_table_offset);

            if(_qHdr.size <= 1)
            {
                AaruConsole.ErrorWriteLine("Image size is too small");

                return ErrorNumber.InvalidArgument;
            }

            if(_qHdr.cluster_bits < 9 ||
               _qHdr.cluster_bits > 16)
            {
                AaruConsole.ErrorWriteLine("Cluster size must be between 512 bytes and 64 Kbytes");

                return ErrorNumber.InvalidArgument;
            }

            if(_qHdr.l2_bits < 9  - 3 ||
               _qHdr.l2_bits > 16 - 3)
            {
                AaruConsole.ErrorWriteLine("L2 size must be between 512 bytes and 64 Kbytes");

                return ErrorNumber.InvalidArgument;
            }

            if(_qHdr.crypt_method > QCOW_ENCRYPTION_AES)
            {
                AaruConsole.ErrorWriteLine("Invalid encryption method");

                return ErrorNumber.InvalidArgument;
            }

            if(_qHdr.crypt_method > QCOW_ENCRYPTION_NONE)
            {
                AaruConsole.ErrorWriteLine("AES encrypted images not yet supported");

                return ErrorNumber.NotImplemented;
            }

            if(_qHdr.backing_file_offset != 0)
            {
                AaruConsole.ErrorWriteLine("Differencing images not yet supported");

                return ErrorNumber.NotImplemented;
            }

            int shift = _qHdr.cluster_bits + _qHdr.l2_bits;

            if(_qHdr.size > ulong.MaxValue - (ulong)(1 << shift))
            {
                AaruConsole.ErrorWriteLine("Image is too large");

                return ErrorNumber.InvalidArgument;
            }

            _clusterSize    = 1 << _qHdr.cluster_bits;
            _clusterSectors = 1 << (_qHdr.cluster_bits - 9);
            _l1Size         = (uint)((_qHdr.size + (ulong)(1 << shift) - 1) >> shift);
            _l2Size         = 1 << _qHdr.l2_bits;

            AaruConsole.DebugWriteLine("QCOW plugin", "qHdr.clusterSize = {0}", _clusterSize);
            AaruConsole.DebugWriteLine("QCOW plugin", "qHdr.clusterSectors = {0}", _clusterSectors);
            AaruConsole.DebugWriteLine("QCOW plugin", "qHdr.l1Size = {0}", _l1Size);
            AaruConsole.DebugWriteLine("QCOW plugin", "qHdr.l2Size = {0}", _l2Size);
            AaruConsole.DebugWriteLine("QCOW plugin", "qHdr.sectors = {0}", _imageInfo.Sectors);

            byte[] l1TableB = new byte[_l1Size * 8];
            stream.Seek((long)_qHdr.l1_table_offset, SeekOrigin.Begin);
            stream.Read(l1TableB, 0, (int)_l1Size * 8);
            _l1Table = MemoryMarshal.Cast<byte, ulong>(l1TableB).ToArray();
            AaruConsole.DebugWriteLine("QCOW plugin", "Reading L1 table");

            for(long i = 0; i < _l1Table.LongLength; i++)
                _l1Table[i] = Swapping.Swap(_l1Table[i]);

            _l1Mask = 0;
            int c = 0;
            _l1Shift = _qHdr.l2_bits + _qHdr.cluster_bits;

            for(int i = 0; i < 64; i++)
            {
                _l1Mask <<= 1;

                if(c >= 64 - _l1Shift)
                    continue;

                _l1Mask += 1;
                c++;
            }

            _l2Mask = 0;

            for(int i = 0; i < _qHdr.l2_bits; i++)
                _l2Mask = (_l2Mask << 1) + 1;

            _l2Mask <<= _qHdr.cluster_bits;

            _sectorMask = 0;

            for(int i = 0; i < _qHdr.cluster_bits; i++)
                _sectorMask = (_sectorMask << 1) + 1;

            AaruConsole.DebugWriteLine("QCOW plugin", "qHdr.l1Mask = {0:X}", _l1Mask);
            AaruConsole.DebugWriteLine("QCOW plugin", "qHdr.l1Shift = {0}", _l1Shift);
            AaruConsole.DebugWriteLine("QCOW plugin", "qHdr.l2Mask = {0:X}", _l2Mask);
            AaruConsole.DebugWriteLine("QCOW plugin", "qHdr.sectorMask = {0:X}", _sectorMask);

            _maxL2TableCache = MAX_CACHE_SIZE / (_l2Size * 8);
            _maxClusterCache = MAX_CACHE_SIZE / _clusterSize;

            _imageStream = stream;

            _sectorCache  = new Dictionary<ulong, byte[]>();
            _l2TableCache = new Dictionary<ulong, ulong[]>();
            _clusterCache = new Dictionary<ulong, byte[]>();

            _imageInfo.CreationTime = imageFilter.CreationTime;

            _imageInfo.LastModificationTime = _qHdr.mtime > 0 ? DateHandlers.UnixUnsignedToDateTime(_qHdr.mtime)
                                                  : imageFilter.LastWriteTime;

            _imageInfo.MediaTitle   = Path.GetFileNameWithoutExtension(imageFilter.Filename);
            _imageInfo.Sectors      = _qHdr.size / 512;
            _imageInfo.SectorSize   = 512;
            _imageInfo.XmlMediaType = XmlMediaType.BlockMedia;
            _imageInfo.MediaType    = MediaType.GENERIC_HDD;
            _imageInfo.ImageSize    = _qHdr.size;

            _imageInfo.Cylinders       = (uint)(_imageInfo.Sectors / 16 / 63);
            _imageInfo.Heads           = 16;
            _imageInfo.SectorsPerTrack = 63;

            return ErrorNumber.NoError;
        }

        /// <inheritdoc />
        public ErrorNumber ReadSector(ulong sectorAddress, out byte[] buffer)
        {
            buffer = null;

            if(sectorAddress > _imageInfo.Sectors - 1)
                return ErrorNumber.OutOfRange;

            // Check cache
            if(_sectorCache.TryGetValue(sectorAddress, out buffer))
                return ErrorNumber.NoError;

            ulong byteAddress = sectorAddress * 512;

            ulong l1Off = (byteAddress & _l1Mask) >> _l1Shift;

            if((long)l1Off >= _l1Table.LongLength)
            {
                AaruConsole.DebugWriteLine("QCOW plugin",
                                           $"Trying to read past L1 table, position {l1Off} of a max {_l1Table.LongLength}");

                return ErrorNumber.InvalidArgument;
            }

            // TODO: Implement differential images
            if(_l1Table[l1Off] == 0)
            {
                buffer = new byte[512];

                return ErrorNumber.NoError;
            }

            if(!_l2TableCache.TryGetValue(l1Off, out ulong[] l2Table))
            {
                _imageStream.Seek((long)_l1Table[l1Off], SeekOrigin.Begin);
                byte[] l2TableB = new byte[_l2Size * 8];
                _imageStream.Read(l2TableB, 0, _l2Size * 8);
                AaruConsole.DebugWriteLine("QCOW plugin", "Reading L2 table #{0}", l1Off);
                l2Table = MemoryMarshal.Cast<byte, ulong>(l2TableB).ToArray();

                for(long i = 0; i < l2Table.LongLength; i++)
                    l2Table[i] = Swapping.Swap(l2Table[i]);

                if(_l2TableCache.Count >= _maxL2TableCache)
                    _l2TableCache.Clear();

                _l2TableCache.Add(l1Off, l2Table);
            }

            ulong l2Off = (byteAddress & _l2Mask) >> _qHdr.cluster_bits;

            ulong offset = l2Table[l2Off];

            buffer = new byte[512];

            if(offset != 0)
            {
                if(!_clusterCache.TryGetValue(offset, out byte[] cluster))
                {
                    if((offset & QCOW_COMPRESSED) == QCOW_COMPRESSED)
                    {
                        ulong compSizeMask = (ulong)(1 << _qHdr.cluster_bits) - 1;
                        compSizeMask <<= 63 - _qHdr.cluster_bits;
                        ulong offMask = ~compSizeMask ^ QCOW_COMPRESSED;

                        ulong realOff  = offset & offMask;
                        ulong compSize = (offset & compSizeMask) >> (63 - _qHdr.cluster_bits);

                        byte[] zCluster = new byte[compSize];
                        _imageStream.Seek((long)realOff, SeekOrigin.Begin);
                        _imageStream.Read(zCluster, 0, (int)compSize);

                        var zStream = new DeflateStream(new MemoryStream(zCluster), CompressionMode.Decompress);
                        cluster = new byte[_clusterSize];
                        int read = zStream.Read(cluster, 0, _clusterSize);

                        if(read != _clusterSize)
                            return ErrorNumber.InOutError;
                    }
                    else
                    {
                        cluster = new byte[_clusterSize];
                        _imageStream.Seek((long)offset, SeekOrigin.Begin);
                        _imageStream.Read(cluster, 0, _clusterSize);
                    }

                    if(_clusterCache.Count >= _maxClusterCache)
                        _clusterCache.Clear();

                    _clusterCache.Add(offset, cluster);
                }

                Array.Copy(cluster, (int)(byteAddress & _sectorMask), buffer, 0, 512);
            }

            if(_sectorCache.Count >= MAX_CACHED_SECTORS)
                _sectorCache.Clear();

            _sectorCache.Add(sectorAddress, buffer);

            return ErrorNumber.NoError;
        }

        /// <inheritdoc />
        public ErrorNumber ReadSectors(ulong sectorAddress, uint length, out byte[] buffer)
        {
            buffer = null;

            if(sectorAddress > _imageInfo.Sectors - 1)
                return ErrorNumber.OutOfRange;

            if(sectorAddress + length > _imageInfo.Sectors)
                return ErrorNumber.OutOfRange;

            var ms = new MemoryStream();

            for(uint i = 0; i < length; i++)
            {
                ErrorNumber errno = ReadSector(sectorAddress + i, out byte[] sector);

                if(errno != ErrorNumber.NoError)
                    return errno;

                ms.Write(sector, 0, sector.Length);
            }

            buffer = ms.ToArray();

            return ErrorNumber.NoError;
        }
    }
}