using System;
using UnityEngine.Events;
using UnityEngine.EventSystems;

namespace UnityEngine.UI
{
	[AddComponentMenu("UI/BoxSlider", 35)]
	[RequireComponent(typeof(RectTransform))]
	public class BoxSlider : Selectable, IDragHandler, IInitializePotentialDragHandler, ICanvasElement
	{
		public enum Direction
		{
			LeftToRight,
			RightToLeft,
			BottomToTop,
			TopToBottom,
		}
		
		[Serializable]
		public class BoxSliderEvent : UnityEvent<float, float> { }

		[SerializeField]
		private RectTransform m_HandleRect;
		public RectTransform handleRect { get { return m_HandleRect; } set { if (SetClass(ref m_HandleRect, value)) { UpdateCachedReferences(); UpdateVisuals(); } } }
		
		[Space(6)]

		[SerializeField]
		private float m_MinValue = 0;
		public float minValue { get { return m_MinValue; } set { if (SetStruct(ref m_MinValue, value)) { Set(m_Value); SetY (m_ValueY); UpdateVisuals(); } } }
		
		[SerializeField]
		private float m_MaxValue = 1;
		public float maxValue { get { return m_MaxValue; } set { if (SetStruct(ref m_MaxValue, value)) { Set(m_Value); SetY (m_ValueY); UpdateVisuals(); } } }
		
		[SerializeField]
		private bool m_WholeNumbers = false;
		public bool wholeNumbers { get { return m_WholeNumbers; } set { if (SetStruct(ref m_WholeNumbers, value)) { Set(m_Value); SetY (m_ValueY); UpdateVisuals(); } } }
		
		[SerializeField]
		private float m_Value = 1f;
		public float value
		{
			get
			{
				if (wholeNumbers)
					return Mathf.Round(m_Value);
				return m_Value;
			}
			set
			{
				Set(value);
			}
		}
		
		public float normalizedValue
		{
			get
			{
				if (Mathf.Approximately(minValue, maxValue))
					return 0;
				return Mathf.InverseLerp(minValue, maxValue, value);
			}
			set
			{
				this.value = Mathf.Lerp(minValue, maxValue, value);
			}
		}

		[SerializeField]
		private float m_ValueY = 1f;
		public float valueY
		{
			get
			{
				if (wholeNumbers)
					return Mathf.Round(m_ValueY);
				return m_ValueY;
			}
			set
			{
				SetY(value);
			}
		}
		
		public float normalizedValueY
		{
			get
			{
				if (Mathf.Approximately(minValue, maxValue))
					return 0;
				return Mathf.InverseLerp(minValue, maxValue, valueY);
			}
			set
			{
				this.valueY = Mathf.Lerp(minValue, maxValue, value);
			}
		}
		
		[Space(6)]
		
		// Allow for delegate-based subscriptions for faster events than 'eventReceiver', and allowing for multiple receivers.
		[SerializeField]
		private BoxSliderEvent m_OnValueChanged = new BoxSliderEvent();
		public BoxSliderEvent onValueChanged { get { return m_OnValueChanged; } set { m_OnValueChanged = value; } }
		
		// Private fields
		
        //private Image m_FillImage;
        //private Transform m_FillTransform;
        //private RectTransform m_FillContainerRect;
		private Transform m_HandleTransform;
		private RectTransform m_HandleContainerRect;
		
		// The offset from handle position to mouse down position
		private Vector2 m_Offset = Vector2.zero;
		
		private DrivenRectTransformTracker m_Tracker;
		
		// Size of each step.
		float stepSize { get { return wholeNumbers ? 1 : (maxValue - minValue) * 0.1f; } }
		
		protected BoxSlider()
		{ }
		
		#if UNITY_EDITOR
		protected override void OnValidate()
		{
			base.OnValidate();
			
			if (wholeNumbers)
			{
				m_MinValue = Mathf.Round(m_MinValue);
				m_MaxValue = Mathf.Round(m_MaxValue);
			}
			//Onvalidate is called before OnEnabled. We need to make sure not to touch any other objects before OnEnable is run.
            if (IsActive())
            {
				UpdateCachedReferences();
				Set(m_Value, false);
				SetY(m_ValueY, false);
				// Update rects since other things might affect them even if value didn't change.
				UpdateVisuals();
			}

			#if UNITY_2018_3_OR_NEWER
			//handle new prefab API
			var prefabType = UnityEditor.PrefabUtility.GetPrefabAssetType(this);
			if (prefabType != UnityEditor.PrefabAssetType.Regular && !Application.isPlaying)
				CanvasUpdateRegistry.RegisterCanvasElementForLayoutRebuild(this);
			#else
			var prefabType = UnityEditor.PrefabUtility.GetPrefabType(this);
			if (prefabType != UnityEditor.PrefabType.Prefab && !Application.isPlaying)
				CanvasUpdateRegistry.RegisterCanvasElementForLayoutRebuild(this);
			#endif
		}
		
		#endif // if UNITY_EDITOR
		
		public virtual void Rebuild(CanvasUpdate executing)
		{
			#if UNITY_EDITOR
			if (executing == CanvasUpdate.Prelayout)
				onValueChanged.Invoke(value, valueY);
			#endif
		}

	    public void LayoutComplete()
	    {
	        
	    }

	    public void GraphicUpdateComplete()
	    {

	    }

	    public static bool SetClass<T>(ref T currentValue, T newValue) where T: class
		{
			if ((currentValue == null && newValue == null) || (currentValue != null && currentValue.Equals(newValue)))
				return false;
			
			currentValue = newValue;
			return true;
		}

		public static bool SetStruct<T>(ref T currentValue, T newValue) where T: struct
		{
			if (currentValue.Equals(newValue))
			return false;
			
			currentValue = newValue;
			return true;
		}
		
		protected override void OnEnable()
		{
			base.OnEnable();
			UpdateCachedReferences();
			Set(m_Value, false);
			SetY(m_ValueY, false);
			// Update rects since they need to be initialized correctly.
			UpdateVisuals();
		}
		
		protected override void OnDisable()
		{
			m_Tracker.Clear();
			base.OnDisable();
		}
		
		void UpdateCachedReferences()
		{
			
			if (m_HandleRect)
			{
				m_HandleTransform = m_HandleRect.transform;
				if (m_HandleTransform.parent != null)
					m_HandleContainerRect = m_HandleTransform.parent.GetComponent<RectTransform>();
			}
			else
			{
				m_HandleContainerRect = null;
			}
		}
		
		// Set the valueUpdate the visible Image.
		void Set(float input)
		{
			Set(input, true);
		}
		
		void Set(float input, bool sendCallback)
		{
			// Clamp the input
			float newValue = Mathf.Clamp(input, minValue, maxValue);
			if (wholeNumbers)
				newValue = Mathf.Round(newValue);
			
			// If the stepped value doesn't match the last one, it's time to update
			if (m_Value == newValue)
				return;
			
			m_Value = newValue;
			UpdateVisuals();
			if (sendCallback)
				m_OnValueChanged.Invoke(newValue, valueY);
		}

		void SetY(float input)
		{
			SetY(input, true);
		}
		
		void SetY(float input, bool sendCallback)
		{
			// Clamp the input
			float newValue = Mathf.Clamp(input, minValue, maxValue);
			if (wholeNumbers)
				newValue = Mathf.Round(newValue);
			
			// If the stepped value doesn't match the last one, it's time to update
			if (m_ValueY == newValue)
				return;
			
			m_ValueY = newValue;
			UpdateVisuals();
			if (sendCallback)
				m_OnValueChanged.Invoke(value, newValue);
		}

		
		protected override void OnRectTransformDimensionsChange()
		{
			base.OnRectTransformDimensionsChange();
			//This can be invoked before OnEnabled is called. So we shouldn't be accessing other objects, before OnEnable is called.
			if (!IsActive())
				return;
			UpdateVisuals();
		}
		
		enum Axis
		{
			Horizontal = 0,
			Vertical = 1
		}

		
		// Force-update the slider. Useful if you've changed the properties and want it to update visually.
		private void UpdateVisuals()
		{
			#if UNITY_EDITOR
			if (!Application.isPlaying)
				UpdateCachedReferences();
			#endif
			
			m_Tracker.Clear();
			

			//to business!
			if (m_HandleContainerRect != null)
			{
				m_Tracker.Add(this, m_HandleRect, DrivenTransformProperties.Anchors);
				Vector2 anchorMin = Vector2.zero;
				Vector2 anchorMax = Vector2.one;
				anchorMin[0] = anchorMax[0] = (normalizedValue);
				anchorMin[1] = anchorMax[1] = ( normalizedValueY);

				m_HandleRect.anchorMin = anchorMin;
				m_HandleRect.anchorMax = anchorMax;
			}
		}
		
		// Update the slider's position based on the mouse.
		void UpdateDrag(PointerEventData eventData, Camera cam)
		{
			RectTransform clickRect = m_HandleContainerRect;
			if (clickRect != null && clickRect.rect.size[0] > 0)
			{
				Vector2 localCursor;
				if (!RectTransformUtility.ScreenPointToLocalPointInRectangle(clickRect, eventData.position, cam, out localCursor))
					return;
				localCursor -= clickRect.rect.position;
				
				float val = Mathf.Clamp01((localCursor - m_Offset)[0] / clickRect.rect.size[0]);
				normalizedValue = (val);

				float valY = Mathf.Clamp01((localCursor - m_Offset)[1] / clickRect.rect.size[1]);
				normalizedValueY = ( valY);

			}
		}
		
		private bool MayDrag(PointerEventData eventData)
		{
			return IsActive() && IsInteractable() && eventData.button == PointerEventData.InputButton.Left;
		}
		
		public override void OnPointerDown(PointerEventData eventData)
		{
			if (!MayDrag(eventData))
				return;
			
			base.OnPointerDown(eventData);
			
			m_Offset = Vector2.zero;
			if (m_HandleContainerRect != null && RectTransformUtility.RectangleContainsScreenPoint(m_HandleRect, eventData.position, eventData.enterEventCamera))
			{
				Vector2 localMousePos;
				if (RectTransformUtility.ScreenPointToLocalPointInRectangle(m_HandleRect, eventData.position, eventData.pressEventCamera, out localMousePos))
					m_Offset = localMousePos;
				m_Offset.y = -m_Offset.y;
			}
			else
			{
				// Outside the slider handle - jump to this point instead
				UpdateDrag(eventData, eventData.pressEventCamera);
			}
		}
		
		public virtual void OnDrag(PointerEventData eventData)
		{
			if (!MayDrag(eventData))
				return;
			
			UpdateDrag(eventData, eventData.pressEventCamera);
		}
		
        //public override void OnMove(AxisEventData eventData)
        //{
        //    if (!IsActive() || !IsInteractable())
        //    {
        //        base.OnMove(eventData);
        //        return;
        //    }
			
        //    switch (eventData.moveDir)
        //    {
        //    case MoveDirection.Left:
        //        if (axis == Axis.Horizontal && FindSelectableOnLeft() == null) {
        //            Set(reverseValue ? value + stepSize : value - stepSize);
        //            SetY (reverseValue ? valueY + stepSize : valueY - stepSize);
        //        }
        //        else
        //            base.OnMove(eventData);
        //        break;
        //    case MoveDirection.Right:
        //        if (axis == Axis.Horizontal && FindSelectableOnRight() == null) {
        //            Set(reverseValue ? value - stepSize : value + stepSize);
        //            SetY(reverseValue ? valueY - stepSize : valueY + stepSize);
        //        }
        //        else
        //            base.OnMove(eventData);
        //        break;
        //    case MoveDirection.Up:
        //        if (axis == Axis.Vertical && FindSelectableOnUp() == null) {
        //            Set(reverseValue ? value - stepSize : value + stepSize);
        //            SetY(reverseValue ? valueY - stepSize : valueY + stepSize);
        //        }
        //        else
        //            base.OnMove(eventData);
        //        break;
        //    case MoveDirection.Down:
        //        if (axis == Axis.Vertical && FindSelectableOnDown() == null) {
        //            Set(reverseValue ? value + stepSize : value - stepSize);
        //            SetY(reverseValue ? valueY + stepSize : valueY - stepSize);
        //        }
        //        else
        //            base.OnMove(eventData);
        //        break;
        //    }
        //}
		
        //public override Selectable FindSelectableOnLeft()
        //{
        //    if (navigation.mode == Navigation.Mode.Automatic && axis == Axis.Horizontal)
        //        return null;
        //    return base.FindSelectableOnLeft();
        //}
		
        //public override Selectable FindSelectableOnRight()
        //{
        //    if (navigation.mode == Navigation.Mode.Automatic && axis == Axis.Horizontal)
        //        return null;
        //    return base.FindSelectableOnRight();
        //}
		
        //public override Selectable FindSelectableOnUp()
        //{
        //    if (navigation.mode == Navigation.Mode.Automatic && axis == Axis.Vertical)
        //        return null;
        //    return base.FindSelectableOnUp();
        //}
		
        //public override Selectable FindSelectableOnDown()
        //{
        //    if (navigation.mode == Navigation.Mode.Automatic && axis == Axis.Vertical)
        //        return null;
        //    return base.FindSelectableOnDown();
        //}
		
		public virtual void OnInitializePotentialDrag(PointerEventData eventData)
		{
			eventData.useDragThreshold = false;
		}

	}
}
