// /***************************************************************************
// The Disc Image Chef
// ----------------------------------------------------------------------------
//
// Filename       : AODOS.cs
// Author(s)      : Natalia Portillo <claunia@claunia.com>
//
// Component      : Commodore file system plugin.
//
// --[ Description ] ----------------------------------------------------------
//
//     Identifies the AO-DOS 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 © 2011-2019 Natalia Portillo
// ****************************************************************************/

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

namespace DiscImageChef.Filesystems
{
    // Information has been extracted looking at available disk images
    // This may be missing fields, or not, I don't know russian so any help is appreciated
    public class AODOS : IFilesystem
    {
        readonly byte[]         AODOSIdentifier = {0x20, 0x41, 0x4F, 0x2D, 0x44, 0x4F, 0x53, 0x20};
        public   FileSystemType XmlFsType { get; private set; }
        public   string         Name      => "Alexander Osipov DOS file system";
        public   Guid           Id        => new Guid("668E5039-9DDD-442A-BE1B-A315D6E38E26");
        public   Encoding       Encoding  { get; private set; }
        public   string         Author    => "Natalia Portillo";

        public bool Identify(IMediaImage imagePlugin, Partition partition)
        {
            // Does AO-DOS support hard disks?
            if(partition.Start > 0) return false;

            // How is it really?
            if(imagePlugin.Info.SectorSize != 512) return false;

            // Does AO-DOS support any other kind of disk?
            if(imagePlugin.Info.Sectors != 800 && imagePlugin.Info.Sectors != 1600) return false;

            byte[]          sector = imagePlugin.ReadSector(0);
            AODOS_BootBlock bb     = Marshal.ByteArrayToStructureLittleEndian<AODOS_BootBlock>(sector);

            return bb.identifier.SequenceEqual(AODOSIdentifier);
        }

        public void GetInformation(IMediaImage imagePlugin, Partition partition, out string information,
                                   Encoding    encoding)
        {
            Encoding = Encoding.GetEncoding("koi8-r");
            byte[]          sector = imagePlugin.ReadSector(0);
            AODOS_BootBlock bb     = Marshal.ByteArrayToStructureLittleEndian<AODOS_BootBlock>(sector);

            StringBuilder sbInformation = new StringBuilder();

            sbInformation.AppendLine("Alexander Osipov DOS file system");

            XmlFsType = new FileSystemType
            {
                Type                  = "Alexander Osipov DOS file system",
                Clusters              = imagePlugin.Info.Sectors,
                ClusterSize           = imagePlugin.Info.SectorSize,
                Files                 = bb.files,
                FilesSpecified        = true,
                FreeClusters          = imagePlugin.Info.Sectors - bb.usedSectors,
                FreeClustersSpecified = true,
                VolumeName            = StringHandlers.SpacePaddedToString(bb.volumeLabel, Encoding),
                Bootable              = true
            };

            sbInformation.AppendFormat("{0} files on volume", bb.files).AppendLine();
            sbInformation.AppendFormat("{0} used sectors on volume", bb.usedSectors).AppendLine();
            sbInformation.AppendFormat("Disk name: {0}", StringHandlers.CToString(bb.volumeLabel, Encoding))
                         .AppendLine();

            information = sbInformation.ToString();
        }

        [StructLayout(LayoutKind.Sequential, Pack = 1)]
        struct AODOS_BootBlock
        {
            /// <summary>
            ///     A NOP opcode
            /// </summary>
            public readonly byte nop;
            /// <summary>
            ///     A branch to real bootloader
            /// </summary>
            public readonly ushort branch;
            /// <summary>
            ///     Unused
            /// </summary>
            public readonly byte unused;
            /// <summary>
            ///     " AO-DOS "
            /// </summary>
            [MarshalAs(UnmanagedType.ByValArray, SizeConst = 8)]
            public readonly byte[] identifier;
            /// <summary>
            ///     Volume label
            /// </summary>
            [MarshalAs(UnmanagedType.ByValArray, SizeConst = 12)]
            public readonly byte[] volumeLabel;
            /// <summary>
            ///     How many files are present in disk
            /// </summary>
            public readonly ushort files;
            /// <summary>
            ///     How many sectors are used
            /// </summary>
            public readonly ushort usedSectors;
        }
    }
}