using System;
using System.Collections.Generic;
using System.Linq;
using SegmentedControlSample.Controls;
using Xamarin.Forms;

namespace SegmentedControlSample
{
    public class SegmentedBarControl: ContentView
    {
	public static readonly BindableProperty ItemSelectedProperty = BindableProperty.Create(nameof(ItemSelected), typeof(string), typeof(SegmentedBarControl), null);
	public static readonly BindableProperty ChildrenProperty = BindableProperty.Create(nameof(Children), typeof(List<string>), typeof(SegmentedBarControl), null);
        public static readonly BindableProperty TextColorProperty = BindableProperty.Create(nameof(TextColor), typeof(Color), typeof(SegmentedBarControl), Color.DarkGray);
        public static readonly BindableProperty SelectedLineColorProperty = BindableProperty.Create(nameof(SelectedLineColor), typeof(Color), typeof(SegmentedBarControl), Color.Black);
        public static readonly BindableProperty SelectedTextColorProperty = BindableProperty.Create(nameof(SelectedTextColor), typeof(Color), typeof(SegmentedBarControl), Color.Black);
        public static readonly BindableProperty AutoScrollProperty = BindableProperty.Create(nameof(AutoScroll), typeof(bool), typeof(SegmentedBarControl), true);
        public delegate void ValueChangedEventHandler(object sender, EventArgs e);
        public event ValueChangedEventHandler ValueChanged;
	public string ItemSelected { get { return (string)GetValue(ItemSelectedProperty);} set { SetValue(ItemSelectedProperty, value); ValueChanged(this, new EventArgs()); } }
	public List<string> Children { get { return (List<string>)GetValue(ChildrenProperty); } set { SetValue(ChildrenProperty, value);}}
        public Color TextColor { get { return (Color)GetValue(TextColorProperty); } set { SetValue(TextColorProperty, value); } }
        public Color SelectedTextColor { get { return (Color)GetValue(SelectedTextColorProperty); } set { SetValue(SelectedTextColorProperty, value); } }
	public Color SelectedLineColor { get { return (Color)GetValue(SelectedLineColorProperty); } set { SetValue(SelectedLineColorProperty, value); } }
        public bool AutoScroll { get { return (bool)GetValue(AutoScrollProperty); } set { SetValue(AutoScrollProperty, value); } }
        StackLayout _mainContentLayout = new StackLayout(){ Spacing = 10, Orientation = StackOrientation.Horizontal };
        StackLayout _lastElementSelected;
        ScrollViewWithNotBar _mainLayout = new ScrollViewWithNotBar() {VerticalOptions = LayoutOptions.Start, Orientation = ScrollOrientation.Horizontal };

        void LoadChildrens(){
            _mainContentLayout.Children.Clear();
            foreach (var item in Children)
            {
		var label = new Label()
				{
                   	          FontAttributes= FontAttributes.Bold,
				  Text = item,
                    		  TextColor=TextColor,
                                  Margin= new Thickness(10,0),
				  HorizontalOptions = LayoutOptions.CenterAndExpand
				};

                var boxview = new BoxView() { BackgroundColor = Color.Transparent, HeightRequest = 2, HorizontalOptions = LayoutOptions.FillAndExpand };
                var childrenLayout = new StackLayout(){Spacing=5};

                childrenLayout.Children.Add(label);
                childrenLayout.Children.Add(boxview);
                childrenLayout.ClassId = item;
		_mainContentLayout.Children.Add(childrenLayout);
		var tapGestureRecognizer = new TapGestureRecognizer();
		tapGestureRecognizer.Tapped += (s, e) => {
                    ItemSelected = ((StackLayout)s).ClassId;
		};
		childrenLayout.GestureRecognizers.Add(tapGestureRecognizer);
            }
            _mainLayout.Content = _mainContentLayout;
            var mainContentLayout = new StackLayout() { Spacing = 0 };
            mainContentLayout.Children.Add(_mainLayout);
            mainContentLayout.Children.Add(new BoxView() { HeightRequest = 0.5, HorizontalOptions = LayoutOptions.FillAndExpand, BackgroundColor = Color.Silver });

            this.Content = mainContentLayout;

        }

        void SelectElement(StackLayout itemSelected)
	{
            if (_lastElementSelected != null){
                (_lastElementSelected.Children.First(p => p is BoxView) as BoxView).BackgroundColor = Color.Transparent;
                (_lastElementSelected.Children.First(p => p is Label) as Label).TextColor = TextColor;
            }

            (itemSelected.Children.First(p => p is BoxView) as BoxView).BackgroundColor = SelectedLineColor;
            (itemSelected.Children.First(p => p is Label) as Label).TextColor = SelectedTextColor;
	    _lastElementSelected = itemSelected;
            if(AutoScroll)
                _mainLayout.ScrollToAsync(itemSelected, ScrollToPosition.MakeVisible, true);
        }

        protected override void OnPropertyChanged(string propertyName = null)
        {
            base.OnPropertyChanged(propertyName);

            if(propertyName == ItemSelectedProperty.PropertyName && Children != null && Children.Count > 0){
                SelectElement(_mainContentLayout.Children[Children.IndexOf(ItemSelected)] as StackLayout);
            } else  if (propertyName == ChildrenProperty.PropertyName && Children != null)
	    {
		LoadChildrens();
                if(string.IsNullOrEmpty(ItemSelected))
		{
	            ItemSelected = Children.First();
                }else{
		    SelectElement(_mainContentLayout.Children[Children.IndexOf(ItemSelected)] as StackLayout);
                }
	    }
        }
    }
}