using Avalar.Services;
using Avalonia.Media.Imaging;
using ReactiveUI;
using System;
using System.ComponentModel;
using System.Threading;
using System.Threading.Tasks;

namespace Avalar.Models
{
    public class PipelineStep<T> : IPipelineStep where T : INotifyPropertyChanged, IProcessor
    {
        public PipelineStep(T processor)
        {
            m_Processor = processor ?? throw new ArgumentNullException(nameof(processor));
            m_Processor.PropertyChanged += OnPropertyChanged;
        }

        private void OnPropertyChanged(object sender, PropertyChangedEventArgs e)
        {
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(Result)));
        }

        public void InvalidateResult()
        {
            Result = null;
        }

        private T m_Processor;

        public event PropertyChangedEventHandler PropertyChanged;

        private IBitmap Result { get; set; }

        public Task<IBitmap> Run(IBitmap bitmap, CancellationToken token)
        {
            if (Result != null)
            {
                return Task.FromResult(Result);
            }
            else
            {
                return Task.Run(() =>
                {
                    Result = m_Processor.Process(bitmap, token);
                    token.ThrowIfCancellationRequested();
                    return Result;
                });
            }
        }
    }

    public static class PipelineStep
    {
        public static PipelineStep<T> Create<T>(T processor) where T : INotifyPropertyChanged, IProcessor
        {
            return new PipelineStep<T>(processor);
        }

        public static PipelineStep<T> AsPipelineStep<T>(this T processor) where T : INotifyPropertyChanged, IProcessor
        {
            return Create(processor);
        }
    }
}