// /***************************************************************************
// Aaru Data Preservation Suite
// ----------------------------------------------------------------------------
//
// Filename       : File.cs
// Author(s)      : Natalia Portillo <claunia@claunia.com>
//
// Component      : Microsoft FAT filesystem plugin.
//
// --[ 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 © 2011-2026 Natalia Portillo
// ****************************************************************************/

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using Aaru.CommonTypes.Enums;
using Aaru.CommonTypes.Interfaces;
using Aaru.CommonTypes.Structs;
using Aaru.Helpers;
using FileAttributes = Aaru.CommonTypes.Structs.FileAttributes;

namespace Aaru.Filesystems;

public sealed partial class FAT
{
    uint[] GetClusters(uint startCluster)
    {
        if(startCluster == 0) return [];

        if(startCluster >= Metadata.Clusters) return null;

        List<uint> clusters = [];

        uint nextCluster = startCluster;

        ulong nextSector = nextCluster / _fatEntriesPerSector + _fatFirstSector + (_useFirstFat ? 0 : _sectorsPerFat);

        var nextEntry = (int)(nextCluster % _fatEntriesPerSector);

        ulong       currentSector = nextSector;
        ErrorNumber errno         = _image.ReadSector(currentSector, false, out byte[] fatData, out _);

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

        if(_fat32)
        {
            while((nextCluster & FAT32_MASK) > 0 && (nextCluster & FAT32_MASK) <= FAT32_RESERVED)
            {
                clusters.Add(nextCluster);

                if(currentSector != nextSector)
                {
                    errno = _image.ReadSector(nextSector, false, out fatData, out _);

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

                    currentSector = nextSector;
                }

                nextCluster = BitConverter.ToUInt32(fatData, nextEntry * 4);

                nextSector = nextCluster / _fatEntriesPerSector + _fatFirstSector + (_useFirstFat ? 0 : _sectorsPerFat);

                nextEntry = (int)(nextCluster % _fatEntriesPerSector);
            }
        }
        else if(_fat16)
        {
            while(nextCluster is > 0 and <= FAT16_RESERVED)
            {
                if(nextCluster >= _fatEntries.Length) break;

                clusters.Add(nextCluster);
                nextCluster = _fatEntries[nextCluster];
            }
        }
        else
        {
            while(nextCluster is > 0 and <= FAT12_RESERVED)
            {
                if(nextCluster >= _fatEntries.Length) break;

                clusters.Add(nextCluster);
                nextCluster = _fatEntries[nextCluster];
            }
        }

        return clusters.ToArray();
    }

    ErrorNumber GetFileEntry(string path, out CompleteDirectoryEntry entry)
    {
        entry = null;

        string cutPath = path.StartsWith('/') ? path[1..].ToLower(_cultureInfo) : path.ToLower(_cultureInfo);

        string[] pieces = cutPath.Split(['/'], StringSplitOptions.RemoveEmptyEntries);

        if(pieces.Length == 0) return ErrorNumber.InvalidArgument;

        var parentPath = string.Join("/", pieces, 0, pieces.Length - 1);

        if(!_directoryCache.TryGetValue(parentPath, out _))
        {
            ErrorNumber err = OpenDir(parentPath, out IDirNode node);

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

            CloseDir(node);
        }

        Dictionary<string, CompleteDirectoryEntry> parent;

        if(pieces.Length == 1)
            parent = _rootDirectoryCache;
        else if(!_directoryCache.TryGetValue(parentPath, out parent)) return ErrorNumber.InvalidArgument;

        KeyValuePair<string, CompleteDirectoryEntry> dirent =
            parent.FirstOrDefault(t => t.Key.ToLower(_cultureInfo) == pieces[^1]);

        if(string.IsNullOrEmpty(dirent.Key)) return ErrorNumber.NoSuchFile;

        entry = dirent.Value;

        return ErrorNumber.NoError;
    }

    static byte LfnChecksum(byte[] name, byte[] extension)
    {
        byte sum = 0;

        for(var i = 0; i < 8; i++) sum = (byte)(((sum & 1) << 7) + (sum >> 1) + name[i]);

        for(var i = 0; i < 3; i++) sum = (byte)(((sum & 1) << 7) + (sum >> 1) + extension[i]);

        return sum;
    }

#region IReadOnlyFilesystem Members

    /// <inheritdoc />
    public ErrorNumber OpenFile(string path, out IFileNode node)
    {
        node = null;

        if(!_mounted) return ErrorNumber.AccessDenied;

        ErrorNumber err = Stat(path, out FileEntryInfo stat);

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

        if(stat.Attributes.HasFlag(FileAttributes.Directory) && !_debug) return ErrorNumber.IsDirectory;

        uint[] clusters = GetClusters((uint)stat.Inode);

        if(clusters is null) return ErrorNumber.InvalidArgument;

        node = new FatFileNode
        {
            Path     = path,
            Length   = stat.Length,
            Offset   = 0,
            Clusters = clusters
        };

        return ErrorNumber.NoError;
    }

    /// <inheritdoc />
    public ErrorNumber CloseFile(IFileNode node)
    {
        if(!_mounted) return ErrorNumber.AccessDenied;

        if(node is not FatFileNode mynode) return ErrorNumber.InvalidArgument;

        mynode.Clusters = null;

        return ErrorNumber.NoError;
    }

    /// <inheritdoc />
    public ErrorNumber ReadFile(IFileNode node, long length, byte[] buffer, out long read)
    {
        read = 0;

        if(!_mounted) return ErrorNumber.AccessDenied;

        if(buffer is null || buffer.Length < length) return ErrorNumber.InvalidArgument;

        if(node is not FatFileNode mynode) return ErrorNumber.InvalidArgument;

        read = length;

        if(length + mynode.Offset >= mynode.Length) read = mynode.Length - mynode.Offset;

        long firstCluster    = mynode.Offset            / _bytesPerCluster;
        long offsetInCluster = mynode.Offset            % _bytesPerCluster;
        long sizeInClusters  = (read + offsetInCluster) / _bytesPerCluster;

        if((read + offsetInCluster) % _bytesPerCluster > 0) sizeInClusters++;

        var ms = new MemoryStream();

        for(var i = 0; i < sizeInClusters; i++)
        {
            if(i + firstCluster >= mynode.Clusters.Length) return ErrorNumber.InvalidArgument;

            ErrorNumber errno =
                _image.ReadSectors(_firstClusterSector + mynode.Clusters[i + firstCluster] * _sectorsPerCluster,
                                   false,
                                   _sectorsPerCluster,
                                   out byte[] buf,
                                   out _);

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

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

        ms.Position = offsetInCluster;
        ms.EnsureRead(buffer, 0, (int)read);
        mynode.Offset += read;

        return ErrorNumber.NoError;
    }

    /// <inheritdoc />
    public ErrorNumber Stat(string path, out FileEntryInfo stat)
    {
        stat = null;

        if(!_mounted) return ErrorNumber.AccessDenied;

        ErrorNumber err = GetFileEntry(path, out CompleteDirectoryEntry completeEntry);

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

        DirectoryEntry entry = completeEntry.Dirent;

        stat = new FileEntryInfo
        {
            Attributes = new FileAttributes(),
            Blocks     = entry.size / _bytesPerCluster,
            BlockSize  = _bytesPerCluster,
            Length     = entry.size,
            Inode      = (ulong)(_fat32 ? (entry.ea_handle << 16) + entry.start_cluster : entry.start_cluster),
            Links      = 1
        };

        if(entry.cdate > 0 || entry.ctime > 0) stat.CreationTime = DateHandlers.DosToDateTime(entry.cdate, entry.ctime);

        if(_namespace != Namespace.Human)
        {
            if(entry.mdate > 0 || entry.mtime > 0)
                stat.LastWriteTime = DateHandlers.DosToDateTime(entry.mdate, entry.mtime);

            if(entry.ctime_ms > 0) stat.CreationTime = stat.CreationTime?.AddMilliseconds(entry.ctime_ms * 10);
        }

        if(entry.size % _bytesPerCluster > 0) stat.Blocks++;

        if(entry.attributes.HasFlag(FatAttributes.Subdirectory))
        {
            stat.Attributes |= FileAttributes.Directory;

            if(_fat32 && entry.ea_handle << 16 > 0 || entry.start_cluster > 0)
            {
                stat.Blocks = _fat32
                                  ? GetClusters((uint)((entry.ea_handle << 16) + entry.start_cluster))?.Length ?? 0
                                  : GetClusters(entry.start_cluster)?.Length                                   ?? 0;
            }

            stat.Length = stat.Blocks * stat.BlockSize;
        }

        if(entry.attributes.HasFlag(FatAttributes.ReadOnly)) stat.Attributes |= FileAttributes.ReadOnly;

        if(entry.attributes.HasFlag(FatAttributes.Hidden)) stat.Attributes |= FileAttributes.Hidden;

        if(entry.attributes.HasFlag(FatAttributes.System)) stat.Attributes |= FileAttributes.System;

        if(entry.attributes.HasFlag(FatAttributes.Archive)) stat.Attributes |= FileAttributes.Archive;

        if(entry.attributes.HasFlag(FatAttributes.Device)) stat.Attributes |= FileAttributes.Device;

        return ErrorNumber.NoError;
    }

#endregion
}