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

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

/// <summary>
/// Dynamic UI - Canvas Layer Handler script for handling UGUI canvas sorting layer: place the last clicked canvas on top layer. 
/// </summary>
public class DCanvasLayerHandler : MonoBehaviour
{
	/// <summary> The base sorting order of handled canvases. Canvas with larger sorting order will show on top. </summary>
	public static int baseLayer = 100;

	/// <summary> A list of Canvases to be handled by this script. </summary>
	private static List<Canvas> handledCanvasList = new List<Canvas>();

	private static DCanvasLayerHandler _instance = null;

	public enum SortLayerEventType
	{
		OnTouchUp = 0,
		OnTouchDown,
		OnTap,
	}
	public SortLayerEventType sortLayerEventType = SortLayerEventType.OnTouchDown;

	float onTouchDownTime = 0f;
	float onTapInterval = 0.3f;

	bool isTouchDown = false;
	bool isTouchUp = true;
	GameObject touchedObject;

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

	/// Set the target canvas to be managed by this handler, 
	/// for automatically handle the canvas layers when the user drag/tap on the UI.
	public static void iAddCanvas(Canvas canvas, bool createCanvasLayerHandlerIfNotExist = true)
	{
		if(canvas == null) return;

        if (_instance == null && createCanvasLayerHandlerIfNotExist)
        {
            _instance = new GameObject("[DCanvasLayerHandler]").AddComponent<DCanvasLayerHandler>();
        }
        
		if(_instance && !handledCanvasList.Contains(canvas))
		{
			canvas.sortingOrder = baseLayer + handledCanvasList.Count;
			handledCanvasList.Add(canvas);
		}
	}

	/// Set the target canvas to be managed by this handler, 
	/// for automatically handle the canvas layers when the user drag/tap on the UI.
	public void AddCanvas(Canvas canvas)
	{
		iAddCanvas(canvas);
	}

	void Awake()
	{
		if(_instance == null)
		{
			_instance = this;
		}
		else
		{
			Debug.LogWarning("Duplicated DCanvasLayerHandler removed in gameObject: " + this.name);
			Destroy(this);
		}
	}

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

			if(isTouchDown)
			{
				//A mouse/touch down event detected.
				isTouchUp = false;
				onTouchDownTime = Time.time;

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

				EventSystem.current.RaycastAll(cursor, objectsHit);
				if(objectsHit.Count > 0)
				{
					touchedObject = objectsHit[0].gameObject;
				}

				if(sortLayerEventType == SortLayerEventType.OnTouchDown) _SortLayer();
			}
		}
		else if(isTouchDown)
		{
            isTouchUp = SDev.Util.UnifyInputUtil.WasTouchOrMouseReleased();

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

				if(sortLayerEventType == SortLayerEventType.OnTouchUp) 
				{
					_SortLayer();
				}
				else if(sortLayerEventType == SortLayerEventType.OnTap)
				{
					if(onTouchDownTime + onTapInterval > Time.time)
					{
						_SortLayer();
					}
				}
			}
		}
	}

	private void _SortLayer()
	{
        cursor.position = SDev.Util.UnifyInputUtil.GetCursorPosition();

		EventSystem.current.RaycastAll(cursor, objectsHit);
		if(objectsHit.Count > 0)
		{
			if(touchedObject != null && touchedObject == objectsHit[0].gameObject)
			{
				for(int i=0; i<handledCanvasList.Count; i++)
				{
					if(handledCanvasList[i] == null)
					{
						handledCanvasList.RemoveAt(i);
					}
					handledCanvasList.TrimExcess();
				}

				Transform tf = objectsHit[0].gameObject.transform;
				Transform root = tf.root;
				Canvas getCanvas = null;

				do{
					tf = tf.parent;
					if(tf.gameObject.GetComponent<Canvas>() != null) 
					{
						getCanvas = tf.gameObject.GetComponent<Canvas>();
					}
				}
				while(tf != root && getCanvas == null);

				if(getCanvas != null && handledCanvasList.Contains(getCanvas))
				{
					handledCanvasList.Remove(getCanvas);
					handledCanvasList.Add(getCanvas);

					for(int i=0; i<handledCanvasList.Count; i++)
					{
						if(handledCanvasList[i] != null) handledCanvasList[i].sortingOrder = baseLayer + i;
					}
				}
			}
		}
	}
}