using System;

using System.Collections.Specialized;

using System.ComponentModel;
using PanCardView.Extensions;

using PanCardView.Processors;
using Xamarin.Forms;

using static System.Math;

namespace PanCardView
{
    public class CoverFlowView : CarouselView
    {
        public static readonly BindableProperty PositionShiftPercentageProperty = BindableProperty.Create(nameof(PositionShiftPercentage), typeof(double), typeof(CoverFlowView), .0, propertyChanged: (bindable, oldValue, newValue) =>
        {
            bindable.AsCardsView().ForceRedrawViews();
        });

        public static readonly BindableProperty PositionShiftValueProperty = BindableProperty.Create(nameof(PositionShiftValue), typeof(double), typeof(CoverFlowView), .0, propertyChanged: (bindable, oldValue, newValue) =>
        {
            bindable.AsCardsView().ForceRedrawViews();
        });



        private bool _shouldForceHardSetCurrentView;

        public CoverFlowView() : this(new CoverFlowProcessor())
        {
        }

        public CoverFlowView(IProcessor processor) : base(processor)
        {
        }

        /// <summary>

        /// Shift to current view percentage (percengate of CoverFlowView Size)

        /// </summary>

        /// <value>The position shift value.</value>
        public double PositionShiftPercentage
        {
            get => (double)GetValue(PositionShiftPercentageProperty);
            set => SetValue(PositionShiftPercentageProperty, value);
        }


        /// <summary>

        /// Shift to current view in absolute points

        /// </summary>

        /// <value>The position shift value.</value>
        public double PositionShiftValue
        {
            get => (double)GetValue(PositionShiftValueProperty);
            set => SetValue(PositionShiftValueProperty, value);
        }

        [EditorBrowsable(EditorBrowsableState.Never)]

        public new static void Preserve()

        {

        }

        protected override int DefaultBackViewsDepth => 2;



        protected override int DefaultMaxChildrenCount => 17;



        protected override int DefaultDesiredMaxChildrenCount => 12;



        protected override void OnObservableCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
        {

            if (sender != null)
            {

                _shouldForceHardSetCurrentView = true;
            }
            base.OnObservableCollectionChanged(sender, e);
        }



        protected override bool CheckIsHardSetCurrentView()
        {

            if (_shouldForceHardSetCurrentView)
            {

                _shouldForceHardSetCurrentView = false;
                return true;
            }


            var oldIndex = OldIndex;
            var index = SelectedIndex;
            var isCyclical = IsCyclical;

            if (isCyclical)
            {
                oldIndex = oldIndex.ToCyclicalIndex(ItemsCount);
                index = index.ToCyclicalIndex(ItemsCount);
            }


            var hasFirstElement = Min(oldIndex, index) == 0;

            var hasLastElement = Max(oldIndex, index) == ItemsCount - 1;


            return Abs(index - oldIndex) > 1 && (!isCyclical || !hasFirstElement || !hasLastElement);
        }
    }
}