using System;
using System.Collections.ObjectModel;
using System.Collections.Specialized;
using System.ComponentModel;
using Android.Content;
using Android.Support.V4.View;
using Android.Support.V7.Widget;
using Android.Views;
using AColor = Android.Graphics.Color;
using AView = Android.Views.View;

namespace Xamarin.Forms.Platform.Android.AppCompat
{
	public class FrameRenderer : CardView, IVisualElementRenderer, AView.IOnClickListener, AView.IOnTouchListener
	{
		readonly Lazy<GestureDetector> _gestureDetector;
		readonly PanGestureHandler _panGestureHandler;
		readonly PinchGestureHandler _pinchGestureHandler;
		readonly Lazy<ScaleGestureDetector> _scaleDetector;
		readonly TapGestureHandler _tapGestureHandler;

		float _defaultElevation = -1f;

		bool _clickable;
		bool _disposed;
		Frame _element;
		InnerGestureListener _gestureListener;
		VisualElementPackager _visualElementPackager;
		VisualElementTracker _visualElementTracker;
		NotifyCollectionChangedEventHandler _collectionChangeHandler;

		public FrameRenderer() : base(Forms.Context)
		{
			_tapGestureHandler = new TapGestureHandler(() => Element);
			_panGestureHandler = new PanGestureHandler(() => Element, Context.FromPixels);
			_pinchGestureHandler = new PinchGestureHandler(() => Element);

			_gestureDetector =
				new Lazy<GestureDetector>(
					() =>
					new GestureDetector(
						_gestureListener =
						new InnerGestureListener(_tapGestureHandler.OnTap, _tapGestureHandler.TapGestureRecognizers, _panGestureHandler.OnPan, _panGestureHandler.OnPanStarted, _panGestureHandler.OnPanComplete)));

			_scaleDetector =
				new Lazy<ScaleGestureDetector>(
					() => new ScaleGestureDetector(Context, new InnerScaleListener(_pinchGestureHandler.OnPinch, _pinchGestureHandler.OnPinchStarted, _pinchGestureHandler.OnPinchEnded), Handler));
		}

		protected CardView Control => this;

		protected Frame Element
		{
			get { return _element; }
			set
			{
				if (_element == value)
					return;

				Frame oldElement = _element;
				_element = value;

				OnElementChanged(new ElementChangedEventArgs<Frame>(oldElement, _element));

				if (_element != null)
					_element.SendViewInitialized(Control);
			}
		}

		void IOnClickListener.OnClick(AView v)
		{
			_tapGestureHandler.OnSingleClick();
		}

		bool IOnTouchListener.OnTouch(AView v, MotionEvent e)
		{
			var handled = false;
			if (_pinchGestureHandler.IsPinchSupported)
			{
				if (!_scaleDetector.IsValueCreated)
					ScaleGestureDetectorCompat.SetQuickScaleEnabled(_scaleDetector.Value, true);
				handled = _scaleDetector.Value.OnTouchEvent(e);
			}
			return _gestureDetector.Value.OnTouchEvent(e) || handled;
		}

		VisualElement IVisualElementRenderer.Element => Element;

		public event EventHandler<VisualElementChangedEventArgs> ElementChanged;

		SizeRequest IVisualElementRenderer.GetDesiredSize(int widthConstraint, int heightConstraint)
		{
			Context context = Context;
			return new SizeRequest(new Size(context.ToPixels(20), context.ToPixels(20)));
		}

		void IVisualElementRenderer.SetElement(VisualElement element)
		{
			var frame = element as Frame;
			if (frame == null)
				throw new ArgumentException("Element must be of type Frame");
			Element = frame;

			if (!string.IsNullOrEmpty(Element.AutomationId))
				ContentDescription = Element.AutomationId;
		}

		VisualElementTracker IVisualElementRenderer.Tracker => _visualElementTracker;

		void IVisualElementRenderer.UpdateLayout()
		{
			VisualElementTracker tracker = _visualElementTracker;
			tracker?.UpdateLayout();
		}

		ViewGroup IVisualElementRenderer.ViewGroup => this;

		protected override void Dispose(bool disposing)
		{
			if (disposing && !_disposed)
			{
				_disposed = true;

				if (_gestureListener != null)
				{
					_gestureListener.Dispose();
					_gestureListener = null;
				}

				if (_visualElementTracker != null)
				{
					_visualElementTracker.Dispose();
					_visualElementTracker = null;
				}

				if (_visualElementPackager != null)
				{
					_visualElementPackager.Dispose();
					_visualElementPackager = null;
				}
			
				int count = ChildCount;
				for (var i = 0; i < count; i++)
				{
					AView child = GetChildAt(i);
					child.Dispose();
				}

				if (Element != null)
				{
					Element.PropertyChanged -= OnElementPropertyChanged;
					UnsubscribeGestureRecognizers(Element);
				}
				
			}

			base.Dispose(disposing);
		}

		protected virtual void OnElementChanged(ElementChangedEventArgs<Frame> e)
		{
			ElementChanged?.Invoke(this, new VisualElementChangedEventArgs(e.OldElement, e.NewElement));

			if (e.OldElement != null)
			{
				e.OldElement.PropertyChanged -= OnElementPropertyChanged;
				UnsubscribeGestureRecognizers(e.OldElement);
			}

			if (e.NewElement != null)
			{
				if (_visualElementTracker == null)
				{
					SetOnClickListener(this);
					SetOnTouchListener(this);

					UpdateGestureRecognizers(true);

					_visualElementTracker = new VisualElementTracker(this);
					_visualElementPackager = new VisualElementPackager(this);
					_visualElementPackager.Load();
				}

				e.NewElement.PropertyChanged += OnElementPropertyChanged;
				UpdateShadow();
				UpdateBackgroundColor();
				SubscribeGestureRecognizers(e.NewElement);
			}
		}

		protected override void OnLayout(bool changed, int left, int top, int right, int bottom)
		{
			if (Element == null)
				return;

			var children = ((IElementController)Element).LogicalChildren;
			for (var i = 0; i < children.Count; i++)
			{
				var visualElement = children[i] as VisualElement;
				if (visualElement == null)
					continue;
				IVisualElementRenderer renderer = Android.Platform.GetRenderer(visualElement);
				renderer?.UpdateLayout();
			}
		}

		void HandleGestureRecognizerCollectionChanged(object sender, NotifyCollectionChangedEventArgs notifyCollectionChangedEventArgs)
		{
			UpdateGestureRecognizers();
		}

		void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e)
		{
			if (e.PropertyName == Frame.HasShadowProperty.PropertyName)
				UpdateShadow();
			else if (e.PropertyName == VisualElement.BackgroundColorProperty.PropertyName)
				UpdateBackgroundColor();
		}

		void SubscribeGestureRecognizers(VisualElement element)
		{
			var view = element as View;
			if (view == null)
				return;

			if (_collectionChangeHandler == null)
				_collectionChangeHandler = HandleGestureRecognizerCollectionChanged;

			var observableCollection = (ObservableCollection<IGestureRecognizer>)view.GestureRecognizers;
			if (observableCollection != null)
			{
				observableCollection.CollectionChanged += _collectionChangeHandler;
			}
		}

		void UnsubscribeGestureRecognizers(VisualElement element)
		{
			var view = element as View;
			if (view == null || _collectionChangeHandler == null)
				return;

			var observableCollection = (ObservableCollection<IGestureRecognizer>)view.GestureRecognizers;
			if (observableCollection != null)
			{
				observableCollection.CollectionChanged -= _collectionChangeHandler;
			}
		}

		void UpdateBackgroundColor()
		{
			Color bgColor = Element.BackgroundColor;
			SetCardBackgroundColor(bgColor.IsDefault ? AColor.White : bgColor.ToAndroid());
		}

		void UpdateClickable(bool force = false)
		{
			var view = Element as View;
			if (view == null)
				return;

			bool newValue = view.ShouldBeMadeClickable();
		    if (force || _clickable != newValue)
		    {
		        Clickable = newValue;
		        _clickable = newValue;
		    }
		}

		void UpdateGestureRecognizers(bool forceClick = false)
		{
			if (Element == null)
				return;

			UpdateClickable(forceClick);
		}

		void UpdateShadow()
		{
			float elevation = _defaultElevation;

			if (elevation == -1f)
				_defaultElevation = elevation = CardElevation;

			if (Element.HasShadow)
				CardElevation = elevation;
			else
				CardElevation = 0f;
		}
	}
}