petrsvihlik/WopiHost

using System.Diagnostics;
using System.Globalization;
using System.Runtime.Versioning;
using System.Security.Principal;
using WopiHost.Abstractions;

namespace WopiHost.FileSystemProvider;

/// <inheritdoc/>
/// <summary>
/// Creates an instance of <see cref="WopiFile"/>.
/// </summary>
/// <param name="filePath">Path on the file system the file is located in.</param>
/// <param name="fileIdentifier">Identifier of a file.</param>
public class WopiFile(string filePath, string fileIdentifier) : IWopiFile
{
    private FileInfo _fileInfo;

    private FileVersionInfo _fileVersionInfo;

    private string FilePath { get; set; } = filePath;

    private FileInfo FileInfo => _fileInfo ??= new FileInfo(FilePath);

    private FileVersionInfo FileVersionInfo => _fileVersionInfo ??= FileVersionInfo.GetVersionInfo(FilePath);

    /// <inheritdoc/>
    public string Identifier { get; } = fileIdentifier;

    /// <inheritdoc />
    public bool Exists => FileInfo.Exists;

    /// <inheritdoc/>
    public string Extension
    {
        get
        {
            var ext = FileInfo.Extension;
            if (ext.StartsWith('.'))
            {
                ext = ext[1..];
            }
            return ext;
        }
    }

    /// <inheritdoc/>
    public string Version => FileVersionInfo.FileVersion ?? FileInfo.LastWriteTimeUtc.ToString(CultureInfo.InvariantCulture);

    /// <inheritdoc/>
    public long Size => FileInfo.Length;

    /// <inheritdoc/>
    public long Length => FileInfo.Length;

    /// <inheritdoc/>
    public string Name => FileInfo.Name;

    /// <inheritdoc/>
    public DateTime LastWriteTimeUtc => FileInfo.LastWriteTimeUtc;

    /// <inheritdoc/>
    public Stream GetReadStream() => FileInfo.OpenRead();

    /// <inheritdoc/>
    public Stream GetWriteStream() => FileInfo.Open(FileMode.Truncate);

    /// <summary>
    /// A string that uniquely identifies the owner of the file.
    /// Supported only on Windows and Linux.
    /// https://docs.microsoft.com/en-us/dotnet/fundamentals/code-analysis/quality-rules/ca1416
    /// </summary>
    [SupportedOSPlatform("linux")]
    [SupportedOSPlatform("windows")]
    public string Owner
    {
        get
        {
            if (OperatingSystem.IsWindows())
            {
                return FileInfo.GetAccessControl().GetOwner(typeof(NTAccount)).ToString();
            }
            //else if (OperatingSystem.IsLinux())
            //{
            //    return Mono.Unix.UnixFileSystemInfo.GetFileSystemEntry(FilePath).OwnerUser.UserName; //TODO: test
            //}
            else
            {
                return "UNSUPPORTED_PLATFORM";
            }
        }
    }
}