Avalonia/src/Avalonia.Native/ClipboardReadSession.cs

using System;
using System.Runtime.InteropServices;
using Avalonia.Native.Interop;

namespace Avalonia.Native;

/// <summary>
/// Represents a single "session" inside a clipboard, defined by its current change count.
/// When the clipboard changes, this session becomes invalid and throws <see cref="ObjectDisposedException"/>.
/// </summary>
internal sealed class ClipboardReadSession(IAvnClipboard native, long changeCount, bool ownsNative) : IDisposable
{
    private const int COR_E_OBJECTDISPOSED = unchecked((int)0x80131622);

    private IAvnClipboard? _native = native;
    private readonly long _changeCount = changeCount;
    private readonly bool _ownsNative = ownsNative;

    public IAvnClipboard Native
        => _native ?? throw new ObjectDisposedException(nameof(ClipboardReadSession));

    public IAvnStringArray? GetFormats()
    {
        try
        {
            return Native.GetFormats(_changeCount);
        }
        catch (COMException ex) when (IsComObjectDisposedException(ex))
        {
            return null;
        }
    }

    public int GetItemCount()
    {
        try
        {
            return Native.GetItemCount(_changeCount);
        }
        catch (COMException ex) when (IsComObjectDisposedException(ex))
        {
            return 0;
        }
    }

    public IAvnStringArray? GetItemFormats(int index)
    {
        try
        {
            return Native.GetItemFormats(index, _changeCount);
        }
        catch (COMException ex) when (IsComObjectDisposedException(ex))
        {
            return null;
        }
    }

    public IAvnString? GetItemValueAsString(int index, string format)
    {
        try
        {
            return Native.GetItemValueAsString(index, _changeCount, format);
        }
        catch (COMException ex) when (IsComObjectDisposedException(ex))
        {
            return null;
        }
    }

    public IAvnString? GetItemValueAsBytes(int index, string format)
    {
        try
        {
            return Native.GetItemValueAsBytes(index, _changeCount, format);
        }
        catch (COMException ex) when (IsComObjectDisposedException(ex))
        {
            return null;
        }
    }

    public bool IsTextFormat(string format)
    {
        try
        {
            return Native.IsTextFormat(format) != 0;
        }
        catch (COMException)
        {
            return false;
        }
    }

    public static bool IsComObjectDisposedException(COMException exception)
        // The native side returns COR_E_OBJECTDISPOSED if the clipboard has changed (_changeCount doesn't match).
        => exception.HResult == COR_E_OBJECTDISPOSED;

    public void Dispose()
    {
        if (_ownsNative)
            _native?.Dispose();

        _native = null;
    }
}