using System.Runtime.InteropServices;

namespace ProtonVPN.OperatingSystems.WebAuthn.Interop.Marshalers;

[StructLayout(LayoutKind.Sequential)]
public abstract class SafeStructArrayOut<T>
{
    protected int _length;
    protected nint _nativeArray = nint.Zero;

    protected SafeStructArrayOut()
    {
    }

    public T[] Items
    {
        get
        {
            if (_nativeArray == nint.Zero || _length <= 0)
            {
                return null;
            }

            // Allocate a managed array
            T[] managedArray = new T[_length];

            // Marshal items one-by-one
            int itemSize = Marshal.SizeOf<T>();
            for (int i = 0; i < _length; i++)
            {
                managedArray[i] = Marshal.PtrToStructure<T>(_nativeArray + itemSize * i);
            }

            return managedArray;
        }
    }
}


[StructLayout(LayoutKind.Sequential)]
public abstract class SafeStructArrayIn<T> : IDisposable
{
    protected int _length;
    protected nint _nativeArray = nint.Zero;

    public SafeStructArrayIn(T[] items)
    {
        if ((items?.Length ?? 0) <= 0)
        {
            return;
        }

        _length = items.Length;

        // Allocate memory
        int itemSize = Marshal.SizeOf<T>();
        int arraySize = _length * itemSize;
        _nativeArray = Marshal.AllocHGlobal(arraySize);

        // Copy items
        for (int i = 0; i < _length; i++)
        {
            Marshal.StructureToPtr(items[i], _nativeArray + itemSize * i, false);
        }
    }

    public void Dispose()
    {
        _length = 0;

        if (_nativeArray != nint.Zero)
        {
            Marshal.FreeHGlobal(_nativeArray);
            _nativeArray = nint.Zero;
        }
    }
}