using UnityEngine;
using UnityEngine.UI;
using UnityEngine.EventSystems;
using System.Collections;
using Logic.CrashSight;

namespace UI.Common
{
    [RequireComponent(typeof(ScrollRect))]
    public class ChooseUISnapScrollRect : MonoBehaviour, IEndDragHandler
    {
        public RectTransform content;       // 自动寻找 Viewport/List
        public float snapSpeed = 10f;       // 平滑速度
        public float snapThreshold = 0.1f;  // 靠近这个范围就停止
        public float itemHeight = 60f;      // 每项高度（固定）

        private ScrollRect scrollRect;
        private bool isSnapping = false;
        private int itemCount = 0;
        public int selectedIndex = -1;

        void Start()
        {
            scrollRect = GetComponent<ScrollRect>();
            scrollRect.horizontal = false;
            scrollRect.vertical = true;

            // 自动寻找 Viewport/List
            if (content == null)
            {
                Transform viewport = transform.Find("Viewport");
                if (viewport != null)
                {
                    Transform list = viewport.Find("List");
                    if (list != null)
                    {
                        content = list.GetComponent<RectTransform>();
                        scrollRect.content = content;
                    }
                    else
                    {
                        LogSystem.LogError($"{name}: 找不到 Viewport/List！");
                    }
                }
                else
                {
                    LogSystem.LogError($"{name}: 找不到 Viewport！");
                }
            }

            if (content != null)
            {
                itemCount = content.childCount;
            }
        }

        public void OnEndDrag(PointerEventData eventData)
        {
            if (!isSnapping && content != null)
            {
                StartCoroutine(SnapToClosestItem());
            }
        }

        IEnumerator SnapToClosestItem()
        {
            isSnapping = true;

            float currentY = content.anchoredPosition.y;
            int closestIndex = Mathf.RoundToInt(currentY / itemHeight);
            closestIndex = Mathf.Clamp(closestIndex, 0, itemCount - 1);

            selectedIndex = closestIndex;
            float targetY = closestIndex * itemHeight;

            while (Mathf.Abs(content.anchoredPosition.y - targetY) > snapThreshold)
            {
                float newY = Mathf.Lerp(content.anchoredPosition.y, targetY, Time.deltaTime * snapSpeed);
                content.anchoredPosition = new Vector2(content.anchoredPosition.x, newY);
                yield return null;
            }

            content.anchoredPosition = new Vector2(content.anchoredPosition.x, targetY);
            HighlightSelectedItem(closestIndex);
            isSnapping = false;
        }

        private void HighlightSelectedItem(int selected)
        {
            for (int i = 0; i < itemCount; i++)
            {
                var option = content.GetChild(i);

                var tmp = option.GetComponent<TMPro.TextMeshProUGUI>();
                if (tmp != null)
                {
                    tmp.color = (i == selected) 
                        ? new Color32(0xFF, 0xFF, 0xFF, 255)   // #FFFFFF
                        : new Color32(0x78, 0x78, 0x78, 255);  // #787878
                    continue;
                }

                var uiText = option.GetComponent<Text>();
                if (uiText != null)
                {
                    uiText.color = (i == selected) 
                        ? new Color32(0xFF, 0xFF, 0xFF, 255)
                        : new Color32(0x78, 0x78, 0x78, 255);
                }
            }
        }

        // 可手动吸附到某一项
        public void SnapToIndex(int index)
        {
            index = Mathf.Clamp(index, 0, itemCount - 1);
            float targetY = index * itemHeight;
            content.anchoredPosition = new Vector2(content.anchoredPosition.x, targetY);
            selectedIndex = index;
            HighlightSelectedItem(index);
        }
    }
}