// /***************************************************************************
// Aaru Data Preservation Suite
// ----------------------------------------------------------------------------
//
// Filename       : Atheos.cs
// Author(s)      : Natalia Portillo <claunia@claunia.com>
//
// Component      : Atheos filesystem plugin.
//
// --[ Description ] ----------------------------------------------------------
//
//     Identifies the Atheos filesystem 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.Diagnostics.CodeAnalysis;
using System.Runtime.InteropServices;
using System.Text;
using Aaru.CommonTypes;
using Aaru.CommonTypes.Enums;
using Aaru.CommonTypes.Interfaces;
using Aaru.Helpers;
using Schemas;
using Marshal = Aaru.Helpers.Marshal;

namespace Aaru.Filesystems;

/// <inheritdoc />
/// <summary>Implements detection for the AtheOS filesystem</summary>
[SuppressMessage("ReSharper", "UnusedMember.Local")]
public sealed class AtheOS : IFilesystem
{
    // Little endian constants (that is, as read by .NET :p)
    const uint AFS_MAGIC1 = 0x41465331;
    const uint AFS_MAGIC2 = 0xDD121031;
    const uint AFS_MAGIC3 = 0x15B6830E;

    // Common constants
    const uint AFS_SUPERBLOCK_SIZE = 1024;
    const uint AFS_BOOTBLOCK_SIZE  = AFS_SUPERBLOCK_SIZE;

    /// <inheritdoc />
    public FileSystemType XmlFsType { get; private set; }
    /// <inheritdoc />
    public Encoding Encoding { get; private set; }
    /// <inheritdoc />
    public string Name => Localization.AtheOS_Name;
    /// <inheritdoc />
    public Guid Id => new("AAB2C4F1-DC07-49EE-A948-576CC51B58C5");
    /// <inheritdoc />
    public string Author => Authors.NataliaPortillo;

    /// <inheritdoc />
    public bool Identify(IMediaImage imagePlugin, Partition partition)
    {
        ulong sector = AFS_BOOTBLOCK_SIZE / imagePlugin.Info.SectorSize;
        uint  offset = AFS_BOOTBLOCK_SIZE % imagePlugin.Info.SectorSize;
        uint  run    = 1;

        if(imagePlugin.Info.SectorSize < AFS_SUPERBLOCK_SIZE)
            run = AFS_SUPERBLOCK_SIZE / imagePlugin.Info.SectorSize;

        if(sector + partition.Start >= partition.End)
            return false;

        ErrorNumber errno = imagePlugin.ReadSectors(sector + partition.Start, run, out byte[] tmp);

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

        byte[] sbSector = new byte[AFS_SUPERBLOCK_SIZE];

        if(offset + AFS_SUPERBLOCK_SIZE > tmp.Length)
            return false;

        Array.Copy(tmp, offset, sbSector, 0, AFS_SUPERBLOCK_SIZE);

        uint magic = BitConverter.ToUInt32(sbSector, 0x20);

        return magic == AFS_MAGIC1;
    }

    /// <inheritdoc />
    public void GetInformation(IMediaImage imagePlugin, Partition partition, out string information, Encoding encoding)
    {
        Encoding    = encoding ?? Encoding.GetEncoding("iso-8859-15");
        information = "";

        var sb = new StringBuilder();

        ulong sector = AFS_BOOTBLOCK_SIZE / imagePlugin.Info.SectorSize;
        uint  offset = AFS_BOOTBLOCK_SIZE % imagePlugin.Info.SectorSize;
        uint  run    = 1;

        if(imagePlugin.Info.SectorSize < AFS_SUPERBLOCK_SIZE)
            run = AFS_SUPERBLOCK_SIZE / imagePlugin.Info.SectorSize;

        ErrorNumber errno = imagePlugin.ReadSectors(sector + partition.Start, run, out byte[] tmp);

        if(errno != ErrorNumber.NoError)
            return;

        byte[] sbSector = new byte[AFS_SUPERBLOCK_SIZE];
        Array.Copy(tmp, offset, sbSector, 0, AFS_SUPERBLOCK_SIZE);

        SuperBlock afsSb = Marshal.ByteArrayToStructureLittleEndian<SuperBlock>(sbSector);

        sb.AppendLine(Localization.Atheos_filesystem);

        if(afsSb.flags == 1)
            sb.AppendLine(Localization.Filesystem_is_read_only);

        sb.AppendFormat(Localization.Volume_name_0, StringHandlers.CToString(afsSb.name, Encoding)).AppendLine();
        sb.AppendFormat(Localization._0_bytes_per_block, afsSb.block_size).AppendLine();

        sb.AppendFormat(Localization._0_blocks_in_volume_1_bytes, afsSb.num_blocks,
                        afsSb.num_blocks * afsSb.block_size).AppendLine();

        sb.AppendFormat(Localization._0_used_blocks_1_bytes, afsSb.used_blocks, afsSb.used_blocks * afsSb.block_size).
           AppendLine();

        sb.AppendFormat(Localization._0_bytes_per_i_node, afsSb.inode_size).AppendLine();

        sb.AppendFormat(Localization._0_blocks_per_allocation_group_1_bytes, afsSb.blocks_per_ag,
                        afsSb.blocks_per_ag * afsSb.block_size).AppendLine();

        sb.AppendFormat(Localization._0_allocation_groups_in_volume, afsSb.num_ags).AppendLine();

        sb.AppendFormat(Localization.Journal_resides_in_block_0_of_allocation_group_1_and_runs_for_2_blocks_3_bytes,
                        afsSb.log_blocks_start, afsSb.log_blocks_ag, afsSb.log_blocks_len,
                        afsSb.log_blocks_len * afsSb.block_size).AppendLine();

        sb.AppendFormat(Localization.Journal_starts_in_byte_0_and_has_1_bytes_in_2_blocks, afsSb.log_start,
                        afsSb.log_size, afsSb.log_valid_blocks).AppendLine();

        sb.
            AppendFormat(Localization.Root_folder_s_i_node_resides_in_block_0_of_allocation_group_1_and_runs_for_2_blocks_3_bytes,
                         afsSb.root_dir_start, afsSb.root_dir_ag, afsSb.root_dir_len,
                         afsSb.root_dir_len * afsSb.block_size).AppendLine();

        sb.
            AppendFormat(Localization.Directory_containing_files_scheduled_for_deletion_i_node_resides_in_block_0_of_allocation_group_1_and_runs_for_2_blocks_3_bytes,
                         afsSb.deleted_start, afsSb.deleted_ag, afsSb.deleted_len,
                         afsSb.deleted_len * afsSb.block_size).AppendLine();

        sb.
            AppendFormat(Localization.Indices_i_node_resides_in_block_0_of_allocation_group_1_and_runs_for_2_blocks_3_bytes,
                         afsSb.indices_start, afsSb.indices_ag, afsSb.indices_len,
                         afsSb.indices_len * afsSb.block_size).AppendLine();

        sb.AppendFormat(Localization._0_blocks_for_bootloader_1_bytes, afsSb.boot_size,
                        afsSb.boot_size * afsSb.block_size).AppendLine();

        information = sb.ToString();

        XmlFsType = new FileSystemType
        {
            Clusters              = (ulong)afsSb.num_blocks,
            ClusterSize           = afsSb.block_size,
            Dirty                 = false,
            FreeClusters          = (ulong)(afsSb.num_blocks - afsSb.used_blocks),
            FreeClustersSpecified = true,
            Type                  = FS_TYPE,
            VolumeName            = StringHandlers.CToString(afsSb.name, Encoding)
        };
    }

    const string FS_TYPE = "atheos";

    /// <summary>Be superblock</summary>
    [StructLayout(LayoutKind.Sequential, Pack = 1)]
    readonly struct SuperBlock
    {
        /// <summary>0x000, Volume name, 32 bytes</summary>
        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 32)]
        public readonly byte[] name;
        /// <summary>0x020, "AFS1", 0x41465331</summary>
        public readonly uint magic1;
        /// <summary>0x024, "BIGE", 0x42494745</summary>
        public readonly uint fs_byte_order;
        /// <summary>0x028, Bytes per block</summary>
        public readonly uint block_size;
        /// <summary>0x02C, 1 &lt;&lt; block_shift == block_size</summary>
        public readonly uint block_shift;
        /// <summary>0x030, Blocks in volume</summary>
        public readonly long num_blocks;
        /// <summary>0x038, Used blocks in volume</summary>
        public readonly long used_blocks;
        /// <summary>0x040, Bytes per inode</summary>
        public readonly int inode_size;
        /// <summary>0x044, 0xDD121031</summary>
        public readonly uint magic2;
        /// <summary>0x048, Blocks per allocation group</summary>
        public readonly int blocks_per_ag;
        /// <summary>0x04C, 1 &lt;&lt; ag_shift == blocks_per_ag</summary>
        public readonly int ag_shift;
        /// <summary>0x050, Allocation groups in volume</summary>
        public readonly int num_ags;
        /// <summary>0x054, 0x434c454e if clean, 0x44495254 if dirty</summary>
        public readonly uint flags;
        /// <summary>0x058, Allocation group of journal</summary>
        public readonly int log_blocks_ag;
        /// <summary>0x05C, Start block of journal, inside ag</summary>
        public readonly ushort log_blocks_start;
        /// <summary>0x05E, Length in blocks of journal, inside ag</summary>
        public readonly ushort log_blocks_len;
        /// <summary>0x060, Start of journal</summary>
        public readonly long log_start;
        /// <summary>0x068, Valid block logs</summary>
        public readonly int log_valid_blocks;
        /// <summary>0x06C, Log size</summary>
        public readonly int log_size;
        /// <summary>0x070, 0x15B6830E</summary>
        public readonly uint magic3;
        /// <summary>0x074, Allocation group where root folder's i-node resides</summary>
        public readonly int root_dir_ag;
        /// <summary>0x078, Start in ag of root folder's i-node</summary>
        public readonly ushort root_dir_start;
        /// <summary>0x07A, As this is part of inode_addr, this is 1</summary>
        public readonly ushort root_dir_len;
        /// <summary>0x07C, Allocation group where pending-delete-files' i-node resides</summary>
        public readonly int deleted_ag;
        /// <summary>0x080, Start in ag of pending-delete-files' i-node</summary>
        public readonly ushort deleted_start;
        /// <summary>0x082, As this is part of inode_addr, this is 1</summary>
        public readonly ushort deleted_len;
        /// <summary>0x084, Allocation group where indices' i-node resides</summary>
        public readonly int indices_ag;
        /// <summary>0x088, Start in ag of indices' i-node</summary>
        public readonly ushort indices_start;
        /// <summary>0x08A, As this is part of inode_addr, this is 1</summary>
        public readonly ushort indices_len;
        /// <summary>0x08C, Size of bootloader</summary>
        public readonly int boot_size;
    }
}