using System.Collections;
using UnityEngine;

namespace YKMoon
{

    public static partial class YKRectTransformUtility
    {
        /// <summary>
        /// Set Pivot without change position.
        /// </summary>
        /// <param name="target"></param>
        /// <param name="pivot"></param>
        public static void SetPivot(this RectTransform target, Vector2 pivot)
        {
            var offset = pivot - target.pivot;
            offset.Scale(target.rect.size);
            var wordlPos = target.position + target.TransformVector(offset);

            target.pivot = pivot;
            target.position = wordlPos;
        }
        public static void SetAnchor(this RectTransform rectTransform, TextAnchor anchor)
        {
            switch(anchor) {
                case TextAnchor.UpperLeft:
                    rectTransform.anchorMin = new Vector2(0, 1f);
                    rectTransform.anchorMax = new Vector2(0, 1f);
                    rectTransform.pivot = new Vector2(0, 1f);
                    break;
                case TextAnchor.UpperCenter:
                    rectTransform.anchorMin = new Vector2(0.5f, 1f);
                    rectTransform.anchorMax = new Vector2(0.5f, 1f);
                    rectTransform.pivot = new Vector2(0.5f, 1f);
                    break;
                case TextAnchor.UpperRight:
                    rectTransform.anchorMin = new Vector2(1f, 1f);
                    rectTransform.anchorMax = new Vector2(1f, 1f);
                    rectTransform.pivot = new Vector2(1f, 1f);
                    break;
                case TextAnchor.MiddleLeft:
                    rectTransform.anchorMin = new Vector2(0f, 0.5f);
                    rectTransform.anchorMax = new Vector2(0f, 0.5f);
                    rectTransform.pivot = new Vector2(0f, 0.5f);
                    break;
                case TextAnchor.MiddleCenter:
                    rectTransform.anchorMin = new Vector2(0.5f, 0.5f);
                    rectTransform.anchorMax = new Vector2(0.5f, 0.5f);
                    rectTransform.pivot = new Vector2(0.5f, 0.5f);
                    break;
                case TextAnchor.MiddleRight:
                    rectTransform.anchorMin = new Vector2(1f, 0.5f);
                    rectTransform.anchorMax = new Vector2(1f, 0.5f);
                    rectTransform.pivot = new Vector2(1f, 0.5f);
                    break;
                case TextAnchor.LowerLeft:
                    rectTransform.anchorMin = new Vector2(0f, 0f);
                    rectTransform.anchorMax = new Vector2(0f, 0f);
                    rectTransform.pivot = new Vector2(0f, 0f);
                    break;
                case TextAnchor.LowerCenter:
                    rectTransform.anchorMin = new Vector2(0.5f, 0f);
                    rectTransform.anchorMax = new Vector2(0.5f, 0f);
                    rectTransform.pivot = new Vector2(0.5f, 0f);
                    break;
                case TextAnchor.LowerRight:
                    rectTransform.anchorMin = new Vector2(1f, 0f);
                    rectTransform.anchorMax = new Vector2(1f, 0f);
                    rectTransform.pivot = new Vector2(1f, 0f);
                    break;
            }
        }
        /// <summary>
        /// Add child(RectTransform) to this RectTransform.
        /// </summary>
        /// <param name="child">a child typeof RectTransform.</param>
        public static void AddChild(this RectTransform rectTransform, RectTransform child)
        {
            rectTransform.AddChild(child);
            child.anchoredPosition = Vector2.zero;
        }
        /// <summary>
        /// 用来重置ScrollView的滚动位置
        /// </summary>
        /// <param name="content">对应ScrollView的content</param>
        public static void ResetScroll(this RectTransform content)
        {
            content.anchoredPosition = Vector2.zero;
        }
        /// <summary>
        /// World position to ugui position.
        /// </summary>
        /// <param name="canvasRectTransform"></param>
        /// <param name="camera"></param>
        /// <param name="worldPosition"></param>
        /// <returns></returns>
        public static Vector2 WorldToUGUIPosition(RectTransform canvasRectTransform, Camera camera, Vector3 worldPosition)
        {
            //世界坐标-〉ViewPort坐标 
            Vector2 viewPos = camera.WorldToViewportPoint(worldPosition);
            //ViewPort坐标-〉UGUI坐标   
            return new Vector2(canvasRectTransform.rect.width * viewPos.x, canvasRectTransform.rect.height * viewPos.y);
        }
        /// <summary>
        /// World deltasize to ugui size.
        /// </summary>
        /// <param name="canvasRectTransform"></param>
        /// <param name="camera"></param>
        /// <param name="delta"></param>
        /// <returns></returns>
        public static Vector2 WorldDeltaToUGUISize(RectTransform canvasRectTransform, Camera camera, Vector3 delta)
        {
            var posA = WorldToUGUIPosition(canvasRectTransform, camera, Vector3.zero);
            var posB = WorldToUGUIPosition(canvasRectTransform, camera, delta);
            return posB - posA;
        }
        /// <summary>
        /// Relative anchord pos between to rect transform.
        /// </summary>
        /// <param name="from"></param>
        /// <param name="to"></param>
        /// <returns></returns>
        public static Vector2 GetRelativeAnchoredPos(RectTransform from, RectTransform to)
        {
            Vector2 localPoint;
            Vector2 fromPivotDerivedOffset = new Vector2(from.rect.width * from.pivot.x + from.rect.xMin, from.rect.height * from.pivot.y + from.rect.yMin);
            Vector2 screenP = RectTransformUtility.WorldToScreenPoint(null, from.position);
            screenP += fromPivotDerivedOffset;
            RectTransformUtility.ScreenPointToLocalPointInRectangle(to, screenP, null, out localPoint);
            Vector2 pivotDerivedOffset = new Vector2(to.rect.width * to.pivot.x + to.rect.xMin, to.rect.height * to.pivot.y + to.rect.yMin);
            return to.anchoredPosition + localPoint - pivotDerivedOffset;
        }
    }
}