// ## 生成滑动列表必须以下步骤：
// 1. 持有RecycleView对象rv，rv.Init(callBackFunc)
// 2. 刷新整个列表（首次调用和数量变化时调用）: ShowList(int count)
// 3. 回调: Func(GameObject cell, int index) 
// ----------
// 功能接口看代码，案例详见RecycleViewTest.cs
// 刷新单个项: UpdateCell(int index)
// 刷新列表数据(无数量变化时调用): UpdateList()
// 定位到索引所在当前列表的位置 GoToCellPos(int index)

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

public enum E_Direction
{
    Horizontal,
    Vertical
}


public class RecycleView : MonoBehaviour, IBeginDragHandler, IEndDragHandler, IDragHandler
{
    public GameObject firstArrow;
    public GameObject endArrow;
    public E_Direction dir = E_Direction.Vertical;
    public bool isShowArrow = false;

    public int lines = 1; // 默认显示1行
    public float squareSpacing = 2f; // 方阵间距
    public GameObject cell; //指定的cell
    public Vector2 Spacing = Vector2.zero;
    public float row = 0f; // 行间距
    public float col = 0f; // 列间距


    protected Action<GameObject, int> FuncCallBackFunc;
    protected Action<GameObject, int> FuncOnClickCallBack;
    protected Action<int, bool, GameObject> FuncOnButtonClickCallBack;

    protected float planeW;
    protected float planeH;
    protected float contentW;
    protected float contentH;
    protected float cellW;
    protected float cellH;

    private bool isInit = false;
    protected GameObject content;
    protected ScrollRect scrollRect;
    protected RectTransform rectTrans;
    protected RectTransform contentRectTrans;

    protected int maxCount = -1; //列表数量
    protected int minIndex = -1;
    protected int maxIndex = -1;

    //记录 物体的坐标 和 物体 
    protected struct CellInfo
    {
        public Vector3 pos;
        public GameObject obj;
    };

    protected CellInfo[] cellInfos;
    protected bool isClearList = false; //是否清空列表

    // 对象池
    protected Stack<GameObject> Pool = new Stack<GameObject>();
    protected bool isInited = false;


    public virtual void Init(Action<GameObject, int> callBack)
    {
        Init(callBack, null);
    }

    public virtual void Init(Action<GameObject, int> callBack, Action<GameObject, int> onClickCallBack,
        Action<int, bool, GameObject> onButtonClickCallBack)
    {
        if (onButtonClickCallBack != null)
        {
            FuncOnButtonClickCallBack = onButtonClickCallBack;
        }

        Init(callBack, onClickCallBack);
    }

    public virtual void Init(Action<GameObject, int> callBack, Action<GameObject, int> onClickCallBack)
    {
        DisposeAll();

        FuncCallBackFunc = callBack;

        if (onClickCallBack != null)
        {
            FuncOnClickCallBack = onClickCallBack;
        }

        if (isInit) return;

        content = this.GetComponent<ScrollRect>().content.gameObject;
        if (cell == null)
        {
            cell = content.transform.GetChild(0).gameObject;
        }

        // ////////////////////** Cell 处理 **////////////////////
        // m_CellGameObject.transform.SetParent(m_Content.transform.parent, false);
        SetPoolsObj(cell);

        RectTransform cellRectTrans = cell.GetComponent<RectTransform>();
        cellRectTrans.pivot = new Vector2(0f, 1f);
        CheckAnchor(cellRectTrans);
        cellRectTrans.anchoredPosition = Vector2.zero;

        // 记录 Cell 信息
        cellH = cellRectTrans.rect.height;
        cellW = cellRectTrans.rect.width;

        // 记录 Plane 信息
        rectTrans = GetComponent<RectTransform>();
        Rect planeRect = rectTrans.rect;
        planeH = planeRect.height;
        planeW = planeRect.width;

        // 记录 Content 信息
        contentRectTrans = content.GetComponent<RectTransform>();
        Rect contentRect = contentRectTrans.rect;
        contentH = contentRect.height;
        contentW = contentRect.width;

        // 记录间距信息 如果存在行列设置就引用，没有使用方阵间距
        row = Spacing.x;
        col = Spacing.y;
        if (row == 0 && col == 0) row = col = squareSpacing;
        else squareSpacing = 0;

        contentRectTrans.pivot = new Vector2(0f, 1f);
        //m_ContentRectTrans.sizeDelta = new Vector2 (planeRect.width, planeRect.height);
        //m_ContentRectTrans.anchoredPosition = Vector2.zero;

        CheckAnchor(contentRectTrans);
        scrollRect = this.GetComponent<ScrollRect>();
        scrollRect.onValueChanged.RemoveAllListeners();

        //添加滑动事件
        scrollRect.onValueChanged.AddListener(delegate (Vector2 value) { ScrollRectListener(value); });
        if (firstArrow != null || endArrow != null)
        {
            scrollRect.onValueChanged.AddListener(delegate (Vector2 value) { OnDragListener(value); });
            OnDragListener(Vector2.zero);
        }

        //InitScrollBarGameObject(); // 废弃
        isInit = true;
    }

    // 检查 Anchor 是否正确
    private void CheckAnchor(RectTransform rectTrans)
    {
        if (dir == E_Direction.Vertical)
        {
            if (!((rectTrans.anchorMin == new Vector2(0, 1) && rectTrans.anchorMax == new Vector2(0, 1)) ||
                  (rectTrans.anchorMin == new Vector2(0, 1) && rectTrans.anchorMax == new Vector2(1, 1))))
            {
                rectTrans.anchorMin = new Vector2(0, 1);
                rectTrans.anchorMax = new Vector2(1, 1);
            }
        }
        else
        {
            if (!((rectTrans.anchorMin == new Vector2(0, 1) && rectTrans.anchorMax == new Vector2(0, 1)) ||
                  (rectTrans.anchorMin == new Vector2(0, 0) && rectTrans.anchorMax == new Vector2(0, 1))))
            {
                rectTrans.anchorMin = new Vector2(0, 0);
                rectTrans.anchorMax = new Vector2(0, 1);
            }
        }
    }

    // 实时刷新列表时用
    public virtual void UpdateList()
    {
        for (int i = 0, length = cellInfos.Length; i < length; i++)
        {
            CellInfo cellInfo = cellInfos[i];
            if (cellInfo.obj != null)
            {
                float rangePos = dir == E_Direction.Vertical ? cellInfo.pos.y : cellInfo.pos.x;
                if (!IsOutRange(rangePos))
                {
                    Func(FuncCallBackFunc, cellInfo.obj, true);
                }
            }
        }
    }

    // 刷新某一项
    public void UpdateCell(int index)
    {
        CellInfo cellInfo = cellInfos[index - 1];
        if (cellInfo.obj != null)
        {
            float rangePos = dir == E_Direction.Vertical ? cellInfo.pos.y : cellInfo.pos.x;
            if (!IsOutRange(rangePos))
            {
                Func(FuncCallBackFunc, cellInfo.obj);
            }
        }
    }

    public virtual void ShowList(string numStr)
    {
    }

    public virtual void ShowList(int num)
    {
        minIndex = -1;
        maxIndex = -1;

        //-> 计算 Content 尺寸
        if (dir == E_Direction.Vertical)
        {
            float contentSize = (col + cellH) * Mathf.CeilToInt((float)num / lines);
            contentH = contentSize;
            contentW = contentRectTrans.sizeDelta.x;
            contentSize = contentSize < rectTrans.rect.height ? rectTrans.rect.height : contentSize;
            contentRectTrans.sizeDelta = new Vector2(contentW, contentSize);
            if (num != maxCount)
            {
                contentRectTrans.anchoredPosition = new Vector2(contentRectTrans.anchoredPosition.x, 0);
            }
        }
        else
        {
            float contentSize = (row + cellW) * Mathf.CeilToInt((float)num / lines);
            contentW = contentSize;
            contentH = contentRectTrans.sizeDelta.x;
            contentSize = contentSize < rectTrans.rect.width ? rectTrans.rect.width : contentSize;
            contentRectTrans.sizeDelta = new Vector2(contentSize, contentH);
            if (num != maxCount)
            {
                contentRectTrans.anchoredPosition = new Vector2(0, contentRectTrans.anchoredPosition.y);
            }
        }

        //-> 计算 开始索引
        int lastEndIndex = 0;

        //-> 过多的物体 扔到对象池 ( 首次调 ShowList函数时 则无效 )
        if (isInited)
        {
            lastEndIndex = num - maxCount > 0 ? maxCount : num;
            lastEndIndex = isClearList ? 0 : lastEndIndex;

            int count = isClearList ? cellInfos.Length : maxCount;
            for (int i = lastEndIndex; i < count; i++)
            {
                if (cellInfos[i].obj != null)
                {
                    SetPoolsObj(cellInfos[i].obj);
                    cellInfos[i].obj = null;
                }
            }
        }

        //-> 以下四行代码 在for循环所用
        CellInfo[] tempCellInfos = cellInfos;
        cellInfos = new CellInfo[num];

        //-> 1: 计算 每个Cell坐标并存储 2: 显示范围内的 Cell
        for (int i = 0; i < num; i++)
        {
            // * -> 存储 已有的数据 ( 首次调 ShowList函数时 则无效 )
            if (maxCount != -1 && i < lastEndIndex)
            {
                CellInfo tempCellInfo = tempCellInfos[i];
                //-> 计算是否超出范围
                float rPos = dir == E_Direction.Vertical ? tempCellInfo.pos.y : tempCellInfo.pos.x;
                if (!IsOutRange(rPos))
                {
                    //-> 记录显示范围中的 首位index 和 末尾index
                    minIndex = minIndex == -1 ? i : minIndex; //首位index
                    maxIndex = i; // 末尾index

                    if (tempCellInfo.obj == null)
                    {
                        tempCellInfo.obj = GetPoolsObj();
                    }

                    tempCellInfo.obj.transform.GetComponent<RectTransform>().anchoredPosition = tempCellInfo.pos;
                    tempCellInfo.obj.name = i.ToString();
                    tempCellInfo.obj.SetActive(true);

                    Func(FuncCallBackFunc, tempCellInfo.obj);
                }
                else
                {
                    SetPoolsObj(tempCellInfo.obj);
                    tempCellInfo.obj = null;
                }

                cellInfos[i] = tempCellInfo;
                continue;
            }

            CellInfo cellInfo = new CellInfo();

            float pos = 0; //坐标( isVertical ? 记录Y : 记录X )
            float rowPos = 0; //计算每排里面的cell 坐标

            // * -> 计算每个Cell坐标
            if (dir == E_Direction.Vertical)
            {
                pos = cellH * Mathf.FloorToInt(i / lines) +
                      col * Mathf.FloorToInt(i / lines);
                rowPos = cellW * (i % lines) + row * (i % lines);
                cellInfo.pos = new Vector3(rowPos, -pos, 0);
            }
            else
            {
                pos = cellW * Mathf.FloorToInt(i / lines) + row * Mathf.FloorToInt(i / lines);
                rowPos = cellH * (i % lines) + col * (i % lines);
                cellInfo.pos = new Vector3(pos, -rowPos, 0);
            }

            //-> 计算是否超出范围
            float cellPos = dir == E_Direction.Vertical ? cellInfo.pos.y : cellInfo.pos.x;
            if (IsOutRange(cellPos))
            {
                cellInfo.obj = null;
                cellInfos[i] = cellInfo;
                continue;
            }

            //-> 记录显示范围中的 首位index 和 末尾index
            minIndex = minIndex == -1 ? i : minIndex; //首位index
            maxIndex = i; // 末尾index

            //-> 取或创建 Cell
            GameObject cell = GetPoolsObj();
            cell.transform.GetComponent<RectTransform>().anchoredPosition = cellInfo.pos;
            cell.gameObject.name = i.ToString();
            
            //-> 存数据
            cellInfo.obj = cell;
            cellInfos[i] = cellInfo;

            //-> 回调  函数
            Func(FuncCallBackFunc, cell);
        }

        maxCount = num;
        isInited = true;

        OnDragListener(Vector2.zero);
    }

    /// <summary>
    /// 通过index定位到GameObject
    /// </summary>
    /// <param name="index"></param>
    public void GoToCellPos(int index)
    {
        // 当前索引所在行的第一个索引
        int theFirstIndex = index - index % lines;
        // 假设在第一行最大索引
        var tmpIndex = theFirstIndex + maxIndex;

        int theLastIndex = tmpIndex > maxCount - 1 ? maxCount - 1 : tmpIndex;

        // 如果最大索引就是边界的话，边界的
        if (theLastIndex == maxCount - 1)
        {
            // 余数不为0的情况下，第一个索引位置需要考虑最大数到最后显示位置的边距
            var shortOfNum = maxCount % lines == 0 ? 0 : lines - maxCount % lines;
            theFirstIndex = theLastIndex - maxIndex + shortOfNum;
        }

        Vector2 newPos = cellInfos[theFirstIndex].pos;
        if (dir == E_Direction.Vertical)
        {
            contentRectTrans.anchoredPosition = new Vector2(contentRectTrans.anchoredPosition.x, -newPos.y);
        }
        else
        {
            contentRectTrans.anchoredPosition = new Vector2(-newPos.x, contentRectTrans.anchoredPosition.y);
        }


        // print(string.Format("index: {0}, theFirstIndex: {1},maxIndex:{2} theLastIndex:{3}", index, theFirstIndex,
        //     maxIndex, theLastIndex));
    }


#if UNITY_EDITOR
    //public void LogRecycleView()
    //{
    //    // 拿到容器基础信息
    //    print("----------------------------------------------------------------------------");
    //    print("Direction: " + dir);
    //    print("Lines: " + lines);
    //    print(string.Format("minIndex: {0} , maxIndex: {1}", minIndex, maxIndex));
    //    print("Capacity: " + (maxIndex - minIndex + 1));
    //    print("----------------------------------------------------------------------------");
    //}
#endif

    // 更新滚动区域的大小
    public void UpdateSize()
    {
        Rect rect = GetComponent<RectTransform>().rect;
        planeH = rect.height;
        planeW = rect.width;
    }

    // 滑动事件
    protected virtual void ScrollRectListener(Vector2 value)
    {
        UpdateCheck();
    }

    private void UpdateCheck()
    {
        if (cellInfos == null) return;

        // 检查超出范围
        for (int i = 0, length = cellInfos.Length; i < length; i++)
        {
            CellInfo cellInfo = cellInfos[i];
            GameObject obj = cellInfo.obj;
            Vector3 pos = cellInfo.pos;

            float rangePos = dir == E_Direction.Vertical ? pos.y : pos.x;
            // 判断是否超出显示范围
            if (IsOutRange(rangePos))
            {
                // 把超出范围的cell 扔进 poolsObj里
                if (obj != null)
                {
                    SetPoolsObj(obj);
                    cellInfos[i].obj = null;
                }
            }
            else
            {
                if (obj == null)
                {
                    // 优先从 poolsObj中 取出 （poolsObj为空则返回 实例化的cell）
                    GameObject cell = GetPoolsObj();
                    cell.transform.localPosition = pos;
                    cell.gameObject.name = i.ToString();
                    cellInfos[i].obj = cell;
                    Func(FuncCallBackFunc, cell);
                }
            }
        }
    }

    // 判断是否超出显示范围
    protected bool IsOutRange(float pos)
    {
        Vector3 listP = contentRectTrans.anchoredPosition;
        if (dir == E_Direction.Vertical)
        {
            if (pos + listP.y > cellH || pos + listP.y < -rectTrans.rect.height)
            {
                return true;
            }
        }
        else
        {
            if (pos + listP.x < -cellW || pos + listP.x > rectTrans.rect.width)
            {
                return true;
            }
        }

        return false;
    }


    //取出 cell
    protected virtual GameObject GetPoolsObj()
    {
        GameObject cell = null;
        if (Pool.Count > 0) cell = Pool.Pop();
        if (cell == null) cell = Instantiate(this.cell) as GameObject;

        cell.transform.SetParent(content.transform);
        cell.transform.localScale = Vector3.one;
        SetActive(cell, true);

        return cell;
    }

    //存入 cell
    protected virtual void SetPoolsObj(GameObject cell)
    {
        if (cell != null)
        {
            Pool.Push(cell);
            SetActive(cell, false);
        }
    }

    //回调
    protected void Func(Action<GameObject, int> func, GameObject selectObject, bool isUpdate = false)
    {
        int index = int.Parse(selectObject.name);
        if (func != null)
        {
            func(selectObject, index);
        }
    }

    public void DisposeAll()
    {
        if (FuncCallBackFunc != null) FuncCallBackFunc = null;
        if (FuncOnClickCallBack != null) FuncOnClickCallBack = null;
        if (FuncOnButtonClickCallBack != null) FuncOnButtonClickCallBack = null;
    }

    protected void OnDestroy()
    {
        DisposeAll();
    }

    public virtual void OnClickCell(GameObject cell)
    {
    }

    //-> ExpandCircularScrollView 函数
    public virtual void OnClickExpand(int index)
    {
    }

    //-> FlipCircularScrollView 函数
    public virtual void SetToPageIndex(int index)
    {
    }

    public virtual void OnBeginDrag(PointerEventData eventData)
    {
    }

    public void OnDrag(PointerEventData eventData)
    {
    }

    public virtual void OnEndDrag(PointerEventData eventData)
    {
    }

    protected void OnDragListener(Vector2 value)
    {
        float normalizedPos = dir == E_Direction.Vertical
            ? scrollRect.verticalNormalizedPosition
            : scrollRect.horizontalNormalizedPosition;

        if (dir == E_Direction.Vertical)
        {
            if (contentH - rectTrans.rect.height < 10)
            {
                SetActive(firstArrow, false);
                SetActive(endArrow, false);
                return;
            }
        }
        else
        {
            if (contentW - rectTrans.rect.width < 10)
            {
                SetActive(firstArrow, false);
                SetActive(endArrow, false);
                return;
            }
        }

        if (normalizedPos >= 0.9)
        {
            SetActive(firstArrow, false);
            SetActive(endArrow, true);
        }
        else if (normalizedPos <= 0.1)
        {
            SetActive(firstArrow, true);
            SetActive(endArrow, false);
        }
        else
        {
            SetActive(firstArrow, true);
            SetActive(endArrow, true);
        }
    }


    public GameObject GetCellGameObject(int index)
    {
        // 为了保证拿到正确数据，根据index应该-1拿到正确数据
        return cellInfos[--index].obj;
    }

    public int GetCellIndex(GameObject obj)
    {
        // 第0号是模板，所以列表中索引应该-1
        return Convert.ToInt32(obj.name) - 1;
    }


    private static void SetActive(GameObject obj, bool isActive)
    {
        if (obj != null)
        {
            obj.SetActive(isActive);
        }
    }
}