using UnityEngine;
using System.Collections;
using UnityEngine.UI;
using System.Collections.Generic;


/// <summary>  
/// 设置Item内容的委托  
/// </summary>  
/// <param name="item">Item对象</param>  
/// <param name="wrapIndex">Item在Grid中的序号</param>  
/// <param name="realIndex">当前Item在List中的序号</param>  
public delegate void OnUpdateItem(GameObject item, int wrapIndex, int realIndex);

/// <summary>  
/// 已显示了所有item的委托
/// </summary>   
public delegate void OnEatUpItem();


///注意：当横排滚动时，不能使用横向拉伸布局，不然会有一些额外的多余尺寸问题
///      同理，当竖排滚动时，不能使用纵向拉伸布局


/// <summary>  
/// 排列方式枚举  
/// </summary>  
public enum ArrangeType
{
    Horizontal = 0,//水平排列  
    Vertical = 1,//垂直排列  
}

public class UIScrollScript : MonoBehaviour
{
    /// <summary>  
    /// Item的宽
    /// </summary>  
    public int cell_x = 100;
    /// <summary>
    /// Item的高
    /// </summary>
    public int cell_y = 100;

    /// <summary>  
    /// Item最小索引
    /// </summary>  
    public int minIndex = 0;

    /// <summary>  
    /// Item最大数量
    /// </summary>  
    public int maxCount = 0;

    /// <summary>  
    /// 排列方式  
    /// </summary>  
    public ArrangeType arrangeType = ArrangeType.Horizontal;

    /// <summary>  
    /// 行列的个数  
    /// </summary>  
    public int ConstraintCount = 0;

    /// <summary>  
    /// 当前RectTransform对象  
    /// </summary>  
    RectTransform mRTrans;

    /// <summary>  
    /// ScrollRect组件
    /// </summary>  
    public ScrollRect mScroll;

    /// <summary>
    /// Pivot为中心点的坐标
    /// </summary>
    Vector2 pivotChildFactor = new Vector2(0.5f, 0.5f);

    /// <summary>  
    /// 滚动方向  
    /// </summary>  
    bool mHorizontal;

    /// <summary>  
    /// 子物体集合
    /// </summary>  
    List<Transform> ChildList = new List<Transform>();

    /// <summary>  
    /// 初始化时区域的长度或者高度的一半
    /// </summary>  
    private float extents = 0;


    /// <summary>
    /// SrollRect的尺寸
    /// </summary>
    Vector2 SR_size = Vector2.zero;


    /// <summary>
    /// SrollRect的尺寸  
    /// </summary>
    Vector3[] conners = new Vector3[4];

    /// <summary>
    /// ScrollRect的初始位置
    /// </summary>
    Vector2 startPos;

    /// <summary>  
    /// 设置Item的委托  
    /// </summary>  
    public OnUpdateItem onUpdateItem;

    public OnEatUpItem onEatUpItem;


    private bool isHandEatup = false;


    [SerializeField] private float leftOffset = 0;
    [SerializeField] private float rightOffset = 0;
    [SerializeField] private float topOffset = 0;
    [SerializeField] private float bottomOffset = 0;

    /// <summary>
    /// 一行中元素的间距
    /// </summary>
    [SerializeField] private float XSpacing = 0;

    /// <summary>
    /// 一列中元素的间距
    /// </summary>
    [SerializeField] private float YSpacing = 0;



    /// <summary>
    /// 初始化赋值(目前只会执行一次)
    /// </summary>
    public void Init()
    {
        mRTrans = transform.GetComponent<RectTransform>();
        mHorizontal = mScroll.horizontal;

        SR_size = mScroll.transform.GetComponent<RectTransform>().rect.size;

        //四角坐标  横着数  
        conners[0] = new Vector3(-SR_size.x / 2f, SR_size.y / 2f, 0);
        conners[1] = new Vector3(SR_size.x / 2f, SR_size.y / 2f, 0);
        conners[2] = new Vector3(-SR_size.x / 2f, -SR_size.y / 2f, 0);
        conners[3] = new Vector3(SR_size.x / 2f, -SR_size.y / 2f, 0);


        //将四角坐标转化为绝对的坐标值
        for (int i = 0; i < 4; i++)
        {
            Vector3 temp = mScroll.transform.TransformPoint(conners[i]);
            conners[i].x = temp.x;
            conners[i].y = temp.y;
        }

        mRTrans.pivot = new Vector2(0, 1);//设置mRTrans的中心在左上角  
        mScroll.onValueChanged.AddListener(delegate { WrapContent(); });//添加滚动事件回调  
        startPos = this.transform.localPosition;
    }


    /// <summary>  
    /// ScrollRect复位（比如：重新进入该页面时）
    /// </summary>  
    public void ResetPosition()
    {
        this.transform.localPosition = startPos;
    }



    [ContextMenu("ResetToInit")]
    public void ResetToInit()
    {
        ResetPosition();
        Init();
        InitList(minIndex, maxCount);
    }



    /// <summary>  
    /// 初始化mChild链表  
    /// </summary>  
    /// 
    public void InitList(int minIndex, int maxIndex)
    {
        isHandEatup = false;
        this.minIndex = minIndex;
        this.maxCount = maxIndex;

        //如果横排数量为0，则设置默认为1，避免手误
        if (ConstraintCount <= 0)
        {
            ConstraintCount = 1;
        }

        //如果最小索引大于了最大索引，则让他俩相等，避免手误
        if (this.minIndex > this.maxCount)
        {
            this.minIndex = this.maxCount;
        }

        //Init();

        ChildList.Clear();
        for (int i = 0; i < transform.childCount; i++)
        {
            ChildList.Add(this.transform.GetChild(i));
        }

        for (int j = 0; j < ChildList.Count; j++)
        {
            Transform temp = ChildList[j];
            RectTransform trf = temp as RectTransform;
            trf.anchorMax = new Vector2(0, 1);
            trf.anchorMin = new Vector2(0, 1);
            trf.pivot = pivotChildFactor;
            trf.anchoredPosition3D = Vector3.zero;
        }
        ResetChildPosition();
    }


    /// <summary>
    /// 更新最大索引数
    /// </summary>
    /// <param name="minIndex"></param>
    /// <param name="maxIndex"></param>
    public void UpdateCount(int minIndex, int maxIndex)
    {
        this.minIndex = minIndex;
        this.maxCount = maxIndex;
        isHandEatup = false;
    }


    void ResetChildPosition()
    {
        ///行数       列数
        int rows = 1, cols = 1;

        //初始位置
        Vector2 startAxis = new Vector2((cell_x / 2f) + leftOffset, (-cell_y / 2f) - topOffset);

        if (arrangeType == ArrangeType.Horizontal)
        {
            rows = ConstraintCount;
            cols = (int)Mathf.Ceil((float)ChildList.Count / rows);
            //（所有子物体宽度的总和 + 所有间距的总和 + 左偏移量 + 右偏移量）/2
            extents = ((cols * cell_x) + (XSpacing * (cols - 1) + leftOffset + rightOffset)) * 0.5f;
        }
        else if (arrangeType == ArrangeType.Vertical)
        {
            cols = ConstraintCount;
            rows = (int)Mathf.Ceil((float)ChildList.Count / (float)cols);
            //（所有子物体高度的总和 + 所有间距的总和 + 上偏移量 + 下偏移量）/2
            extents = ((rows * cell_y) + (YSpacing * (rows - 1) + topOffset + bottomOffset)) * 0.5f;
        }


        ///初始为所有子物体排列布局
        for (int i = 0; i < ChildList.Count; i++)
        {
            Transform temp = ChildList[i];
            RectTransform trf = temp as RectTransform;
            trf.anchorMax = new Vector2(0, 1);
            trf.anchorMin = new Vector2(0, 1);
            trf.pivot = pivotChildFactor;
            trf.anchoredPosition3D = Vector3.zero;

            int x = 0, y = 0;//行列号  
            Vector2 pos = Vector2.zero;
            if (arrangeType == ArrangeType.Vertical)
            {
                x = i / cols; //(行号：0 -1 - 2 - 3 - 4...)
                y = i % cols;//(列号：0 - 1 - 0 - 1...)
                pos = new Vector2((startAxis.x + y * cell_x) + y * XSpacing, (startAxis.y - x * cell_y) - (x * YSpacing));
            }

            else if (arrangeType == ArrangeType.Horizontal)
            {
                x = i % rows;//行号：0 - 1 - 0 - 1...
                y = i / rows;//列号：0 -1 - 2 - 3 - 4...
                pos = new Vector2((startAxis.x + y * cell_x) + y * XSpacing, (startAxis.y - x * cell_y) - (x * YSpacing));
            }

            temp.localPosition = pos;
            if (minIndex == maxCount || (i >= minIndex && i < maxCount))
            {
                temp.gameObject.SetActive(true);
                UpdateRectsize(pos);//更新panel的尺寸  
                UpdateItem(temp, i, i);
                temp.name = i.ToString();
            }
            else
            {
                temp.gameObject.SetActive(false);
            }
        }
    }


    /// <summary>  
    /// 更新Content的尺寸  
    /// </summary>  
    /// <param name="pos"></param>  
    void UpdateRectsize(Vector2 pos)
    {
        if (arrangeType == ArrangeType.Horizontal)
        {
            mRTrans.sizeDelta = new Vector2(pos.x + cell_x * 0.5f + rightOffset, ConstraintCount * cell_y + (ConstraintCount - 1) * YSpacing + topOffset + bottomOffset);
        }
        else
        {
            mRTrans.sizeDelta = new Vector2(ConstraintCount * cell_x + (ConstraintCount - 1) * XSpacing + leftOffset + rightOffset
                , -pos.y + cell_y * 0.5f + bottomOffset);
        }
    }




    /// <summary>
    /// ScrollRect的回调  
    /// </summary>
    public void WrapContent(bool isRefresh = false)
    {
        for (int i = 0; i < ChildList.Count; i++)
        {
            Transform temp = ChildList[i];
            bool isRefreshRect = false;
            Vector2 pos = GetChildPos(temp, out isRefreshRect);
            int realIndex = GetRealIndex(pos);

            if (minIndex == maxCount || (realIndex >= minIndex && realIndex < maxCount))
            {
                temp.gameObject.SetActive(true);
                if (isRefreshRect)
                {
                    //Debug.Log("是否需要刷新");
                    UpdateRectsize(pos);
                }

                temp.localPosition = pos;
                if (temp.name != realIndex.ToString())
                {
                    //设置Item内容  
                    UpdateItem(temp, i, realIndex);
                    temp.name = realIndex.ToString();
                }
                else if (temp.name == realIndex.ToString() && isRefresh)
                {
                    //设置Item内容  
                    UpdateItem(temp, i, realIndex);
                    temp.name = realIndex.ToString();
                }
            }
            else if (realIndex >= maxCount)
            {
                if (!isHandEatup)
                {
                    Debug.Log("WrapContent===>数据已用完");
                    //通知所有要显示的数据已用完
                    if (onEatUpItem != null)
                    {
                        onEatUpItem();
                    }
                    isHandEatup = true;
                }
                return;
            }
        }
    }



    /// <summary>
    /// 获取子物体的位置
    /// </summary>
    /// <param name="temp"></param>
    /// <param name="isRefreshRect"></param>
    /// <returns></returns>
    Vector2 GetChildPos(Transform temp, out bool isRefreshRect)
    {
        isRefreshRect = false;
        Vector3[] conner_local = new Vector3[4];
        for (int i = 0; i < 4; i++)
        {
            conner_local[i] = this.transform.InverseTransformPoint(conners[i]);
        }
        //计算ScrollRect的中心坐标 相对于this的坐标  
        Vector2 center = (conner_local[3] + conner_local[0]) / 2f;
        Vector2 pos = Vector2.zero;
        if (mHorizontal)
        {
            float distance = temp.localPosition.x - center.x;
            pos = temp.localPosition;
            if (distance < -extents)
            {
                isRefreshRect = true;
                pos.x += extents * 2f - leftOffset - rightOffset + XSpacing;
            }
            else if (distance > extents)
            {
                pos.x -= extents * 2f - leftOffset - rightOffset + XSpacing;
            }
        }
        else
        {
            if (temp != null)
            {
                float distance = temp.localPosition.y - center.y;
                pos = temp.localPosition;
                if (distance < -extents)
                {
                    pos.y += extents * 2f - bottomOffset - topOffset + YSpacing;
                }
                else if (distance > extents)
                {
                    isRefreshRect = true;
                    pos.y -= extents * 2f - bottomOffset - topOffset + YSpacing;
                }
            }
        }
        return pos;
    }



    /// <summary>
    /// 计算realIndex
    /// </summary>
    /// <param name="pos"></param>
    /// <returns></returns>
    private int GetRealIndex(Vector2 pos)
    {
        int x = (int)Mathf.Ceil((-pos.y - topOffset + YSpacing) / (cell_y + YSpacing)) - 1;
        int y = (int)Mathf.Ceil((pos.x - leftOffset + XSpacing) / (cell_x + XSpacing)) - 1;

        //int x = (int)Mathf.Ceil(-pos.y / cell_y) - 1;//行号  
        //int y = (int)Mathf.Ceil(pos.x / cell_x) - 1;//列号  
        int realIndex;
        if (arrangeType == ArrangeType.Vertical)
        {
            realIndex = x * ConstraintCount + y;
        }
        else
        {
            realIndex = x + ConstraintCount * y;
        }

        return realIndex;
    }


    /// <summary>
    /// 通知更新Item的数据
    /// </summary>
    /// <param name="item"></param>
    /// <param name="index"></param>
    /// <param name="realIndex"></param>
    void UpdateItem(Transform item, int index, int realIndex)
    {
        if (onUpdateItem != null)
        {
            onUpdateItem(item.gameObject, index, realIndex);
        }
    }
}