using System;
using System.Threading;
using System.Threading.Tasks;
using Windows.UI.Core;
using Windows.UI.Xaml.Media;

namespace MapControl
{
    public partial class TileImageLoader
    {
        private static async Task LoadTileImage(Tile tile, Func<Task<ImageSource>> loadImageFunc, CancellationToken cancellationToken)
        {
            var tcs = new TaskCompletionSource<object>();

            async void LoadTileImage()
            {
                try
                {
                    var image = await loadImageFunc();

                    if (cancellationToken.IsCancellationRequested)
                    {
                        tile.IsPending = true;
                        tcs.TrySetCanceled(cancellationToken);
                    }
                    else
                    {
                        tile.SetImageSource(image);
                        tcs.TrySetResult(null);
                    }
                }
                catch (Exception ex)
                {
                    tcs.TrySetException(ex);
                }
            }

            if (!await tile.Image.Dispatcher.TryRunAsync(CoreDispatcherPriority.Low, LoadTileImage))
            {
                tcs.TrySetCanceled(CancellationToken.None);
            }

            await tcs.Task;
        }
    }
}