Aaru/Aaru.Filters/PCExchange.cs

// /***************************************************************************
// Aaru Data Preservation Suite
// ----------------------------------------------------------------------------
//
// Filename       : PCExchange.cs
// Author(s)      : Natalia Portillo <claunia@claunia.com>
//
// Component      : Filters.
//
// --[ Description ] ----------------------------------------------------------
//
//     Provides a filter to open handle files written by PCExchange in FAT
//     volumes
//
// --[ 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 © 2011-2025 Natalia Portillo
// ****************************************************************************/

using System;
using System.Diagnostics.CodeAnalysis;
using System.Globalization;
using System.IO;
using System.Runtime.InteropServices;
using System.Text;
using Aaru.CommonTypes.Attributes;
using Aaru.CommonTypes.Enums;
using Aaru.CommonTypes.Interfaces;
using Aaru.Helpers;
using Marshal = System.Runtime.InteropServices.Marshal;

namespace Aaru.Filters;

/// <inheritdoc />
/// <summary>Decodes PCExchange files</summary>
[SuppressMessage("ReSharper", "UnusedMember.Local")]
public sealed partial class PcExchange : IFilter
{
    const string FILE_ID     = "FILEID.DAT";
    const string FINDER_INFO = "FINDER.DAT";
    const string RESOURCES   = "RESOURCE.FRK";
    string       _dataPath;
    string       _rsrcPath;

#region IFilter Members

    /// <inheritdoc />
    public string Name => Localization.PcExchange_Name;

    /// <inheritdoc />
    public Guid Id => new("9264EB9F-D634-4F9B-BE12-C24CD44988C6");

    /// <inheritdoc />
    public string Author => Authors.NataliaPortillo;

    /// <inheritdoc />
    public void Close() {}

    /// <inheritdoc />
    public string BasePath { get; private set; }

    /// <inheritdoc />
    public DateTime CreationTime { get; private set; }

    /// <inheritdoc />
    public long DataForkLength { get; private set; }

    /// <inheritdoc />
    public Stream GetDataForkStream() => new FileStream(_dataPath, FileMode.Open, FileAccess.Read);

    /// <inheritdoc />
    public string Filename => System.IO.Path.GetFileName(BasePath);

    /// <inheritdoc />
    public DateTime LastWriteTime { get; private set; }

    /// <inheritdoc />
    public long Length => DataForkLength + ResourceForkLength;

    /// <inheritdoc />
    public string ParentFolder => System.IO.Path.GetDirectoryName(BasePath);

    /// <inheritdoc />
    public string Path => BasePath;

    /// <inheritdoc />
    public long ResourceForkLength { get; private set; }

    /// <inheritdoc />
    public Stream GetResourceForkStream() => new FileStream(_rsrcPath, FileMode.Open, FileAccess.Read);

    /// <inheritdoc />
    public bool HasResourceFork => _rsrcPath != null;

    /// <inheritdoc />
    public bool Identify(byte[] buffer) => false;

    /// <inheritdoc />
    public bool Identify(Stream stream) => false;

    /// <inheritdoc />
    public bool Identify(string path)
    {
        string parentFolder = System.IO.Path.GetDirectoryName(path);

        parentFolder ??= "";

        if(!File.Exists(System.IO.Path.Combine(parentFolder, FINDER_INFO))) return false;

        if(!Directory.Exists(System.IO.Path.Combine(parentFolder, RESOURCES))) return false;

        string baseFilename = System.IO.Path.GetFileName(path);

        var dataFound = false;
        var rsrcFound = false;

        var finderDatStream = new FileStream(System.IO.Path.Combine(parentFolder, FINDER_INFO),
                                             FileMode.Open,
                                             FileAccess.Read);

        while(finderDatStream.Position + 0x5C <= finderDatStream.Length)
        {
            var datEntry  = new Entry();
            var datEntryB = new byte[Marshal.SizeOf(datEntry)];
            finderDatStream.EnsureRead(datEntryB, 0, Marshal.SizeOf(datEntry));
            datEntry = Helpers.Marshal.ByteArrayToStructureBigEndian<Entry>(datEntryB);

            // TODO: Add support for encoding on filters
            string macName = StringHandlers.PascalToString(datEntry.macName, Encoding.GetEncoding("macintosh"));

            var tmpDosNameB = new byte[8];
            var tmpDosExtB  = new byte[3];
            Array.Copy(datEntry.dosName, 0, tmpDosNameB, 0, 8);
            Array.Copy(datEntry.dosName, 8, tmpDosExtB,  0, 3);

            string dosName = Encoding.ASCII.GetString(tmpDosNameB).Trim() +
                             "."                                          +
                             Encoding.ASCII.GetString(tmpDosExtB).Trim();

            string dosNameLow = dosName.ToLower(CultureInfo.CurrentCulture);

            if(baseFilename != macName && baseFilename != dosName && baseFilename != dosNameLow) continue;

            dataFound |=
                File.Exists(System.IO.Path.Combine(parentFolder, macName ?? throw new InvalidOperationException())) ||
                File.Exists(System.IO.Path.Combine(parentFolder, dosName))                                          ||
                File.Exists(System.IO.Path.Combine(parentFolder, dosNameLow));

            rsrcFound |= File.Exists(System.IO.Path.Combine(parentFolder, RESOURCES, dosName)) ||
                         File.Exists(System.IO.Path.Combine(parentFolder, RESOURCES, dosNameLow));

            break;
        }

        finderDatStream.Close();

        return dataFound && rsrcFound;
    }

    /// <inheritdoc />
    public ErrorNumber Open(byte[] buffer) => ErrorNumber.NotSupported;

    /// <inheritdoc />
    public ErrorNumber Open(Stream stream) => ErrorNumber.NotSupported;

    /// <inheritdoc />
    public ErrorNumber Open(string path)
    {
        string parentFolder = System.IO.Path.GetDirectoryName(path);
        string baseFilename = System.IO.Path.GetFileName(path);

        parentFolder ??= "";

        var finderDatStream = new FileStream(System.IO.Path.Combine(parentFolder, FINDER_INFO),
                                             FileMode.Open,
                                             FileAccess.Read);

        while(finderDatStream.Position + 0x5C <= finderDatStream.Length)
        {
            var datEntry  = new Entry();
            var datEntryB = new byte[Marshal.SizeOf(datEntry)];
            finderDatStream.EnsureRead(datEntryB, 0, Marshal.SizeOf(datEntry));
            datEntry = Helpers.Marshal.ByteArrayToStructureBigEndian<Entry>(datEntryB);

            string macName = StringHandlers.PascalToString(datEntry.macName, Encoding.GetEncoding("macintosh"));

            var tmpDosNameB = new byte[8];
            var tmpDosExtB  = new byte[3];
            Array.Copy(datEntry.dosName, 0, tmpDosNameB, 0, 8);
            Array.Copy(datEntry.dosName, 8, tmpDosExtB,  0, 3);

            string dosName = Encoding.ASCII.GetString(tmpDosNameB).Trim() +
                             "."                                          +
                             Encoding.ASCII.GetString(tmpDosExtB).Trim();

            string dosNameLow = dosName.ToLower(CultureInfo.CurrentCulture);

            if(baseFilename != macName && baseFilename != dosName && baseFilename != dosNameLow) continue;

            if(File.Exists(System.IO.Path.Combine(parentFolder, macName ?? throw new InvalidOperationException())))
                _dataPath = System.IO.Path.Combine(parentFolder, macName);
            else if(File.Exists(System.IO.Path.Combine(parentFolder, dosName)))
                _dataPath = System.IO.Path.Combine(parentFolder, dosName);
            else if(File.Exists(System.IO.Path.Combine(parentFolder, dosNameLow)))
                _dataPath = System.IO.Path.Combine(parentFolder, dosNameLow);
            else
                _dataPath = null;

            if(File.Exists(System.IO.Path.Combine(parentFolder, RESOURCES, dosName)))
                _rsrcPath = System.IO.Path.Combine(parentFolder, RESOURCES, dosName);
            else if(File.Exists(System.IO.Path.Combine(parentFolder, RESOURCES, dosNameLow)))
                _rsrcPath = System.IO.Path.Combine(parentFolder, RESOURCES, dosNameLow);
            else
                _rsrcPath = null;

            LastWriteTime = DateHandlers.MacToDateTime(datEntry.modificationDate);
            CreationTime  = DateHandlers.MacToDateTime(datEntry.creationDate);

            break;
        }

        DataForkLength     = new FileInfo(_dataPath ?? throw new InvalidOperationException()).Length;
        ResourceForkLength = new FileInfo(_rsrcPath ?? throw new InvalidOperationException()).Length;

        BasePath = path;

        finderDatStream.Close();

        return ErrorNumber.NoError;
    }

#endregion

#region Nested type: Entry

    [StructLayout(LayoutKind.Sequential, Pack = 1)]
    [SwapEndian]
    partial struct Entry
    {
        /// <summary>
        ///     Name in Macintosh. If PCExchange version supports FAT's LFN they are the same. Illegal characters for FAT get
        ///     substituted with '_' both here and in FAT's LFN entry.
        /// </summary>
        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 32)]
        public byte[] macName;
        /// <summary>File type</summary>
        public uint type;
        /// <summary>File creator</summary>
        public uint creator;
        /// <summary>Finder flags</summary>
        public ushort fdFlags;
        /// <summary>File's icon vertical position within its window</summary>
        public ushort verticalPosition;
        /// <summary>File's icon horizontal position within its window</summary>
        public ushort horizontalPosition;
        /// <summary>Unknown, all bytes are empty but last, except in volume's label entry</summary>
        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 18)]
        public byte[] unknown1;
        /// <summary>File's creation date</summary>
        public uint creationDate;
        /// <summary>File's modification date</summary>
        public uint modificationDate;
        /// <summary>File's last backup date</summary>
        public uint backupDate;
        /// <summary>Unknown, but is unique, starts 0x7FFFFFFF and counts in reverse. Probably file ID for alias look up?</summary>
        public uint unknown2;
        /// <summary>Name as in FAT entry (not LFN). Resource fork file is always using this name, never LFN.</summary>
        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 11)]
        public byte[] dosName;
        /// <summary>Unknown, flags?</summary>
        public byte unknown3;
    }

#endregion
}