using Avalonia.Media.Imaging;
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;

namespace Avalar.Models
{
    public class AvalarPipeline
    {
        private readonly IEnumerable<IPipelineStep> m_steps;

        public AvalarPipeline(IEnumerable<IPipelineStep> steps)
        {
            m_steps = steps ?? throw new ArgumentNullException(nameof(steps));
            foreach (var step in m_steps)
            {
                step.PropertyChanged += OnPipelineComponentChanged;
            }
        }

        private void OnPipelineComponentChanged(object sender, PropertyChangedEventArgs e)
        {
            foreach (var step in m_steps.SkipWhile(step => step != sender))
            {
                step.InvalidateResult();
            }

            PipelineChanged?.Invoke(this, EventArgs.Empty);
        }

        public event EventHandler PipelineChanged;

        public async Task<IBitmap> Run(IBitmap bitmap, CancellationToken token)
        {
            var input = bitmap;
            foreach(var step in m_steps)
            {
                token.ThrowIfCancellationRequested();
                input = await step.Run(input, token).ConfigureAwait(false);
            }
            return input;
        }
    }
}