using System.Collections.Generic;
using System.Linq;
using UIKit;
using Xamarin.Forms;

[assembly: ExportRenderer(typeof(Page), typeof(MyApp.iOS.Renderers.PageRenderer))]
namespace MyApp.iOS.Renderers
{

    public class PageRenderer : Xamarin.Forms.Platform.iOS.PageRenderer
    {
        public override void ViewDidLoad()
        {
            base.ViewDidLoad();

            if (NativeView == null) return;

            var existingRecognizer = NativeView.GestureRecognizers.OfType<UITapGestureRecognizer>().FirstOrDefault();
            if (existingRecognizer != null)
            {
                NativeView.RemoveGestureRecognizer(existingRecognizer);

                var uiTapGestureRecognizer = new UITapGestureRecognizer(a => NativeView?.EndEditing(true));

                uiTapGestureRecognizer.ShouldRecognizeSimultaneously = (recognizer, gestureRecognizer) => true;
                uiTapGestureRecognizer.ShouldReceiveTouch = OnShouldReceiveTouch;
                uiTapGestureRecognizer.DelaysTouchesBegan = uiTapGestureRecognizer.DelaysTouchesEnded = uiTapGestureRecognizer.CancelsTouchesInView = false;
                NativeView.AddGestureRecognizer(uiTapGestureRecognizer);
            }
        }

        bool OnShouldReceiveTouch(UIGestureRecognizer recognizer, UITouch touch)
        {
            foreach (UIView v in ViewAndSuperviewsOfView(touch.View))
            {
                if (v is UITableView || v is UITableViewCell || v.CanBecomeFirstResponder)
                    return false;
            }
            return true;
        }

        IEnumerable<UIView> ViewAndSuperviewsOfView(UIView view)
        {
            while (view != null)
            {
                yield return view;
                view = view.Superview;
            }
        }
    }
}