// /***************************************************************************
// Aaru Data Preservation Suite
// ----------------------------------------------------------------------------
//
// Filename       : Squash.cs
// Author(s)      : Natalia Portillo <claunia@claunia.com>
//
// Component      : Squash file system plugin.
//
// --[ Description ] ----------------------------------------------------------
//
//     Identifies the Squash file system and shows information.
//
// --[ 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 © 2011-2023 Natalia Portillo
// ****************************************************************************/

using System;
using System.Runtime.InteropServices;
using System.Text;
using Aaru.CommonTypes;
using Aaru.CommonTypes.Interfaces;
using Aaru.Helpers;
using Schemas;
using Marshal = Aaru.Helpers.Marshal;

namespace Aaru.Filesystems
{
    /// <inheritdoc />
    /// <summary>Implements detection of the squash filesystem</summary>
    public sealed class Squash : IFilesystem
    {
        /// <summary>Identifier for Squash</summary>
        const uint SQUASH_MAGIC = 0x73717368;
        const uint SQUASH_CIGAM = 0x68737173;

        /// <inheritdoc />
        public FileSystemType XmlFsType { get; private set; }
        /// <inheritdoc />
        public Encoding Encoding { get; private set; }
        /// <inheritdoc />
        public string Name => "Squash filesystem";
        /// <inheritdoc />
        public Guid Id => new Guid("F8F6E46F-7A2A-48E3-9C0A-46AF4DC29E09");
        /// <inheritdoc />
        public string Author => "Natalia Portillo";

        /// <inheritdoc />
        public bool Identify(IMediaImage imagePlugin, Partition partition)
        {
            if(partition.Start >= partition.End)
                return false;

            byte[] sector = imagePlugin.ReadSector(partition.Start);

            uint magic = BitConverter.ToUInt32(sector, 0x00);

            return magic == SQUASH_MAGIC || magic == SQUASH_CIGAM;
        }

        /// <inheritdoc />
        public void GetInformation(IMediaImage imagePlugin, Partition partition, out string information,
                                   Encoding encoding)
        {
            Encoding = encoding ?? Encoding.UTF8;
            byte[] sector = imagePlugin.ReadSector(partition.Start);
            uint   magic  = BitConverter.ToUInt32(sector, 0x00);

            var  sqSb         = new SuperBlock();
            bool littleEndian = true;

            switch(magic)
            {
                case SQUASH_MAGIC:
                    sqSb = Marshal.ByteArrayToStructureLittleEndian<SuperBlock>(sector);

                    break;
                case SQUASH_CIGAM:
                    sqSb         = Marshal.ByteArrayToStructureBigEndian<SuperBlock>(sector);
                    littleEndian = false;

                    break;
            }

            var sbInformation = new StringBuilder();

            sbInformation.AppendLine("Squash file system");
            sbInformation.AppendLine(littleEndian ? "Little-endian" : "Big-endian");
            sbInformation.AppendFormat("Volume version {0}.{1}", sqSb.s_major, sqSb.s_minor).AppendLine();
            sbInformation.AppendFormat("Volume has {0} bytes", sqSb.bytes_used).AppendLine();
            sbInformation.AppendFormat("Volume has {0} bytes per block", sqSb.block_size).AppendLine();

            sbInformation.AppendFormat("Volume created on {0}", DateHandlers.UnixUnsignedToDateTime(sqSb.mkfs_time)).
                          AppendLine();

            sbInformation.AppendFormat("Volume has {0} inodes", sqSb.inodes).AppendLine();

            switch(sqSb.compression)
            {
                case (ushort)SquashCompression.Lz4:
                    sbInformation.AppendLine("Volume is compressed using LZ4");

                    break;
                case (ushort)SquashCompression.Lzo:
                    sbInformation.AppendLine("Volume is compressed using LZO");

                    break;
                case (ushort)SquashCompression.Lzma:
                    sbInformation.AppendLine("Volume is compressed using LZMA");

                    break;
                case (ushort)SquashCompression.Xz:
                    sbInformation.AppendLine("Volume is compressed using XZ");

                    break;
                case (ushort)SquashCompression.Zlib:
                    sbInformation.AppendLine("Volume is compressed using GZIP");

                    break;
                case (ushort)SquashCompression.Zstd:
                    sbInformation.AppendLine("Volume is compressed using Zstandard");

                    break;
                default:
                    sbInformation.AppendFormat("Volume is compressed using unknown algorithm {0}", sqSb.compression).
                                  AppendLine();

                    break;
            }

            information = sbInformation.ToString();

            XmlFsType = new FileSystemType
            {
                Type = "Squash file system",
                CreationDate = DateHandlers.UnixUnsignedToDateTime(sqSb.mkfs_time),
                CreationDateSpecified = true,
                Clusters = (partition.End - partition.Start + 1) * imagePlugin.Info.SectorSize / sqSb.block_size,
                ClusterSize = sqSb.block_size,
                Files = sqSb.inodes,
                FilesSpecified = true,
                FreeClusters = 0,
                FreeClustersSpecified = true
            };
        }

        enum SquashCompression : ushort
        {
            Zlib = 1, Lzma = 2, Lzo  = 3,
            Xz   = 4, Lz4  = 5, Zstd = 6
        }

        [StructLayout(LayoutKind.Sequential, Pack = 1)]
        readonly struct SuperBlock
        {
            public readonly uint   magic;
            public readonly uint   inodes;
            public readonly uint   mkfs_time;
            public readonly uint   block_size;
            public readonly uint   fragments;
            public readonly ushort compression;
            public readonly ushort block_log;
            public readonly ushort flags;
            public readonly ushort no_ids;
            public readonly ushort s_major;
            public readonly ushort s_minor;
            public readonly ulong  root_inode;
            public readonly ulong  bytes_used;
            public readonly ulong  id_table_start;
            public readonly ulong  xattr_id_table_start;
            public readonly ulong  inode_table_start;
            public readonly ulong  directory_table_start;
            public readonly ulong  fragment_table_start;
            public readonly ulong  lookup_table_start;
        }
    }
}