/// <summary>
/// Created by SWAN DEV 2018
/// </summary>

using System;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.EventSystems;

/// Dynamic UI - Draggable UI script for UGUI RaycastTarget components(e.g. Image, RawImage, Text). Attach on the UGUI component, set 'RaycastTarget = True'.
/// (Draggable UI detect the drag area by checking the sizeDelta of the target UI rectTransform, make sure sizeDelta is correctly set. Especially for text.)
public class DDraggableUI : MonoBehaviour
{
	/// Indicates if any DDraggableUI object in the scene is being dragged.
	public static bool draggingGlobal{ get; private set; }

	/// The target draggable UGUI component(Image, RawImage, Text, etc).
	[Tooltip("The target draggable UGUI component(Image, RawImage, Text, etc).")]
	public GameObject m_TargetUIObject;

	/// Move this GameObject instead of the (dragged) TargetUIObject if this GameObject is assigned.
	[Tooltip("Move this GameObject instead of the (dragged) TargetUIObject if this GameObject is assigned.")]
	public GameObject m_MoveUIObject = null;

	/// Lock position change along X-axis.
	[Tooltip("Lock position change along X-axis.")]
	public bool m_LockX = false;

	/// Lock position change along Y-axis.
	[Tooltip("Lock position change along Y-axis.")]
	public bool m_LockY = false;

	/// Indicates if m_TargetUIObject is being dragged.
	public bool dragging{ get; private set; }

	private Action _onDragStart = null;
	public void SetOnDragStartCallback(Action onDragStartAction)
	{
		_onDragStart = onDragStartAction;
	}

	private Action _onDragComplete = null;
	public void SetOnDragCompleteCallback(Action onDragCompleteAction)
	{
		_onDragComplete = onDragCompleteAction;
	}

	bool isTouchDown = false;
	bool isTouchUp = true;
	float diffX = 0f, diffY = 0f;

	PointerEventData cursor = new PointerEventData(EventSystem.current);
	List<RaycastResult> objectsHit = new List<RaycastResult>();

	void OnEnable()
	{
		if(m_TargetUIObject == null) m_TargetUIObject = gameObject;
		if(m_MoveUIObject == null) m_MoveUIObject = m_TargetUIObject;
		dragging = false;
		isTouchUp = true;
	}

	void OnDisable()
	{
		draggingGlobal = false;
		dragging = false;
	}

	void Update() 
	{
		if(isTouchUp)
		{
            isTouchDown = SDev.Util.UnifyInputUtil.WasTouchOrMousePressed();

            if (isTouchDown)
			{
				//A mouse/touch down event detected.
				isTouchUp = false;
                
                cursor.position = SDev.Util.UnifyInputUtil.GetCursorPosition();

				EventSystem.current.RaycastAll(cursor, objectsHit);
				if(objectsHit.Count > 0)
				{
					if(objectsHit[0].gameObject.Equals(m_TargetUIObject))
					{
						dragging = true;
						diffX = m_MoveUIObject.transform.position.x - cursor.position.x;
						diffY = m_MoveUIObject.transform.position.y - cursor.position.y;
						if(_onDragStart != null) _onDragStart();
					}
				}
			}
		}
		else if(isTouchDown)
		{
            isTouchUp = SDev.Util.UnifyInputUtil.WasTouchOrMouseReleased();

            if (isTouchUp)
			{
				//A mouse/touch up event detected.
				isTouchDown = false;
				dragging = false;

				draggingGlobal = false;

				if(_onDragComplete != null) _onDragComplete();
			}
		}

		if(dragging)
		{
			draggingGlobal = true;

            cursor.position = SDev.Util.UnifyInputUtil.GetCursorPosition();

            m_MoveUIObject.transform.position = new Vector3((m_LockX? m_MoveUIObject.transform.position.x : cursor.position.x + diffX), 
				(m_LockY? m_MoveUIObject.transform.position.y : cursor.position.y + diffY), m_MoveUIObject.transform.position.z);
		}
	}

	public static void SetDraggable(GameObject targetUIObject, bool isDraggable)
	{
		if(isDraggable)
		{
			if(targetUIObject.GetComponent<DDraggableUI>() == null) 
			{
				targetUIObject.AddComponent<DDraggableUI>();
			}
		}
		else
		{
			if(targetUIObject.GetComponent<DDraggableUI>() != null) 
			{
				Destroy(targetUIObject.GetComponent<DDraggableUI>());
			}
		}
	}
}