namespace NucleicProtocol.Interop;

/// Managed ownership wrapper for the shared Swift transcript projector.
public interface ITranscriptProjector : IDisposable
{
    ProjectionDiff Apply(string hostMessageJson);
}

public sealed class ProtocolProjection : ITranscriptProjector
{
    private readonly object gate = new();
    private readonly INativeProtocol native;
    private nint handle;

    public ProtocolProjection(INativeProtocol? native = null)
    {
        this.native = native ?? PInvokeNativeProtocol.Instance;
        handle = this.native.ProjectionCreate();
        if (handle == 0) throw new InvalidOperationException("could not create transcript projection");
    }

    public ProjectionDiff Apply(string hostMessageJson)
    {
        lock (gate)
        {
            ObjectDisposedException.ThrowIf(handle == 0, this);
            var value = native.ProjectionApply(handle, hostMessageJson);
            return ProjectionDiff.Parse(native.CopyAndFreeString(value));
        }
    }

    public void Dispose()
    {
        lock (gate)
        {
            if (handle == 0) return;
            native.ProjectionFree(handle);
            handle = 0;
        }
    }
}