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

namespace JC.Unity.Picker {
    /// <summary>
    /// 日期选择器
    /// </summary>
    public class DatePicker : MonoBehaviour, IDragHandler, IEndDragHandler
    {
        public enum DateType {
            Year, Month, Day, Hour, Minute, Second
        }
        /// <summary>
        /// 日期类型 （年月日时分秒）
        /// </summary>
        public DateType dateType;
        /// <summary>
        /// 子节点预制体
        /// </summary>
        public GameObject _itemObj;
        /// <summary>
        /// 子节点容器对象
        /// </summary>
        public Transform _itemParent;
        /// <summary>
        /// 我属于的日期选择组
        /// </summary>
        [HideInInspector]
        public DatePickerGroup myGroup;
        /// <summary>
        /// 最少节点数量
        /// </summary>
        void Awake()
        {
            _itemObj.SetActive(false);
        }
        public void Init() {
            InitItems();
        }
        void InitItems() {
            DateTime dt = myGroup.selectDate;
            ItemData itemData = SpawnItem(GetTopPosY(), dt, GetDateValue(dt).ToString());
            itemList.Add(itemData);
            MoveItems(0);
            CheckSelect();
        }
        public void Refresh() {
            foreach (var item in itemList) {
                Destroy(item.obj);
            }
            itemList.Clear();
            InitItems();
        }
        float GetTopPosY() {
            return 0;
        }
        float GetBottomPosY() {
            return -myGroup.GetHeight();
        }
        float _cellHeight = -1;
        float GetCellHeight() {
            if (_cellHeight == -1) _cellHeight = _itemObj.GetComponent<RectTransform>().rect.height;
            return _cellHeight;
        }
        public void OnDrag(PointerEventData eventData) {
            MoveItems(eventData.delta.y);
        }
        void MoveItems(float dy) {
            foreach (var item in itemList) {
                item.SetY(dy, true);
            }
            while (itemList[0].GetY() < GetTopPosY()) {
                ItemData compareItemData = itemList[0];
                DateTime dt = ChangeDateTime(compareItemData.dateTime, -1);
                if (!IsInDate(dt, myGroup.minDate, myGroup.maxDate)) {
                    break;
                }
                ItemData itemData = SpawnItem(compareItemData.GetY() + GetCellHeight(), dt, GetDateValue(dt).ToString());
                itemList.Insert(0, itemData);
            }
            while (itemList.Count > 1 && itemList[0].GetY() > GetTopPosY() + GetCellHeight()) {
                Destroy(itemList[0].obj);
                itemList.RemoveAt(0);
            }
            while (itemList[itemList.Count - 1].GetY() > GetBottomPosY()) {
                ItemData compareItemData = itemList[itemList.Count - 1];
                DateTime dt = ChangeDateTime(compareItemData.dateTime, +1);
                if (!IsInDate(dt, myGroup.minDate, myGroup.maxDate)) {
                    break;
                }
                ItemData itemData = SpawnItem(compareItemData.GetY() - GetCellHeight(), dt, GetDateValue(dt).ToString());
                itemList.Add(itemData);
            }
            while (itemList.Count > 1 && itemList[itemList.Count - 1].GetY() < GetBottomPosY()) {
                Destroy(itemList[itemList.Count - 1].obj);
                itemList.RemoveAt(itemList.Count - 1);
            }
        }
        public void OnEndDrag(PointerEventData eventData)
        {
            CheckSelect();
            myGroup.onDateUpdate();
        }
        void CheckSelect() {
            float dy = 0;
            float minDist = float.MaxValue;
            ItemData targetItem = null;
            foreach (var item in itemList) {
                item.SetSelected(false);
                float val = item.GetY() - 0;
                float absVal = Mathf.Abs(val);
                if (absVal < minDist) { //选中最符合的节点
                    minDist = absVal;
                    targetItem = item;
                    dy = val;
                }
            }
            if (dy != 0) {
                MoveItems(-dy);
            }
            targetItem.SetSelected(true);
            myGroup.selectDate = targetItem.dateTime;
        } 
        DateTime ChangeDateTime(DateTime dateTime, int num) {
            switch (dateType) {
                case DateType.Year:
                    dateTime = dateTime.AddYears(num);
                    break;
                case DateType.Month:
                    dateTime = dateTime.AddMonths(num);
                    break;
                case DateType.Day:
                    dateTime = dateTime.AddDays(num);
                    break;
                case DateType.Hour:
                    dateTime = dateTime.AddHours(num);
                    break;
                case DateType.Minute:
                    dateTime = dateTime.AddMinutes(num);
                    break;
                case DateType.Second:
                    dateTime = dateTime.AddSeconds(num);
                    break;
            }
            return dateTime;
        }
        int GetDateValue(DateTime dateTime) {
            switch (dateType) {
                case DateType.Year:
                    return dateTime.Year;
                case DateType.Month:
                    return dateTime.Month;
                case DateType.Day:
                    return dateTime.Day;
                case DateType.Hour:
                    return dateTime.Hour;
                case DateType.Minute:
                    return dateTime.Minute;
                case DateType.Second:
                    return dateTime.Second;
            }
            return 0;
        }
        bool IsInDate(DateTime dt, DateTime dt_min, DateTime dt_max) {
            return dt.CompareTo(dt_min) >= 0 && dt.CompareTo(dt_max) <= 0;
        }
        public class ItemData {
            public GameObject obj;
            public DateTime dateTime;
            public bool selected = false;
            public float GetY() {
                return obj.GetComponent<RectTransform>().localPosition.y;
            }
            public void SetY(float y, bool plus = false) {
                RectTransform rectTF = obj.GetComponent<RectTransform>();
                Vector3 pos = rectTF.localPosition;
                if (plus) {
                    pos.y += y;
                } else {
                    pos.y = y;
                }
                rectTF.localPosition = pos;
            }
            public void SetText(string text) {
                obj.GetComponent<Text>().text = text;
            }
            public void SetColor(Color color) {
                obj.GetComponent<Text>().color = color;
            }
            public void SetSelected(bool val) {
                selected = val;
                SetColor(selected ? Color.green : Color.grey);
            }
        }
        List<ItemData> itemList = new List<ItemData>();
        ItemData SpawnItem(float y, DateTime dateTime, string text) {
            ItemData itemData = new ItemData();
            itemData.dateTime = dateTime;
            itemData.obj = Instantiate(_itemObj, _itemParent);
            itemData.SetY(y);
            itemData.SetText(text);
            itemData.SetSelected(false);
            itemData.obj.SetActive(true);
            return itemData;
        }
    }
}