using System.Collections;
using System.Reflection;
using UnityEngine;
using UnityEngine.UI;
using UnityEngine.EventSystems;
using TMPro;

public class CustomTMPDropdown : TMP_Dropdown
{
    private FieldInfo dropdownField;
    private FieldInfo blockerField;
    private GameObject dropdownListGO;

    private int currentOptionIndex = 0; // 光标在 options 索引

    protected override void Awake()
    {
        base.Awake();

        dropdownField = typeof(TMP_Dropdown).GetField(
            "m_Dropdown",
            BindingFlags.NonPublic | BindingFlags.Instance
        );
        blockerField = typeof(TMP_Dropdown).GetField(
            "m_Blocker",
            BindingFlags.NonPublic | BindingFlags.Instance
        );
    }

    public override void OnPointerClick(PointerEventData eventData) { }
    public override void OnSubmit(BaseEventData eventData) { }
    public override void OnCancel(BaseEventData eventData) { }

    private GameObject GetDropdownGO() => dropdownField?.GetValue(this) as GameObject;
    private GameObject GetBlockerGO() => blockerField?.GetValue(this) as GameObject;

    // ---------------- 手动打开/关闭 ----------------
    public void OpenDropdown()
    {
        if (dropdownListGO != null && dropdownListGO.activeSelf) return;
        base.Show();
        StartCoroutine(FixAfterShow());
    }

    public void CloseDropdown()
    {
        if (dropdownListGO != null) Destroy(dropdownListGO);
        GameObject blocker = GetBlockerGO();
        if (blocker != null) Destroy(blocker);
        dropdownListGO = null;
    }

    public void ToggleDropdown()
    {
        var list = GetDropdownGO();
        if (list != null && list.activeSelf) CloseDropdown();
        else OpenDropdown();
    }

    // ---------------- 上下切换 ----------------
    public void SelectNext()
    {
        if (options.Count == 0) return;
        currentOptionIndex = (currentOptionIndex + 1) % options.Count;
        value = currentOptionIndex;
        RefreshShownValue();
        UpdateHighlight();
    }

    public void SelectPrevious()
    {
        if (options.Count == 0) return;
        currentOptionIndex = (currentOptionIndex - 1 + options.Count) % options.Count;
        value = currentOptionIndex;
        RefreshShownValue();
        UpdateHighlight();
    }

    // ---------------- 提交 ----------------
    public void SubmitSelection()
    {
        value = currentOptionIndex;
        RefreshShownValue();
        onValueChanged?.Invoke(value);
        CloseDropdown();
    }

    // ---------------- 初始化 Dropdown ----------------
    private IEnumerator FixAfterShow()
    {
        yield return null; // 等一帧

        dropdownListGO = GetDropdownGO();
        if (dropdownListGO == null) yield break;

        // 禁用 Blocker 射线拦截
        GameObject blocker = GetBlockerGO();
        if (blocker != null)
        {
            Button btn = blocker.GetComponent<Button>();
            if (btn != null) btn.onClick.RemoveAllListeners();
            btn.enabled = false;

            CanvasGroup cg = blocker.GetComponent<CanvasGroup>();
            if (cg == null) cg = blocker.AddComponent<CanvasGroup>();
            cg.blocksRaycasts = false;
        }

        // 清理 Dropdown List EventTrigger
        var et = dropdownListGO.GetComponent<EventTrigger>();
        if (et != null) et.triggers.Clear();

        // 遍历生成的选项，绑定点击事件
        Transform content = dropdownListGO.transform.Find("Viewport/Content");
        if (content != null)
        {
            for (int i = 1; i < content.childCount && i <= options.Count; i++) // i=1跳过模板
            {
                GameObject item = content.GetChild(i).gameObject;
                Toggle toggle = item.GetComponent<Toggle>();
                if (toggle != null)
                {
                    int optionIndex = i - 1; // Content索引->options索引
                    toggle.onValueChanged.RemoveAllListeners();
                    toggle.onValueChanged.AddListener((isOn) =>
                    {
                        if (isOn)
                        {
                            currentOptionIndex = optionIndex;
                            value = currentOptionIndex;
                            RefreshShownValue();
                            onValueChanged?.Invoke(value);
                            CloseDropdown();
                        }
                    });
                }
            }
        }

        // 初始化光标位置
        currentOptionIndex = value;
        UpdateHighlight();
    }

    // ---------------- 光标高亮 + 滚动 ----------------
    private void UpdateHighlight()
    {
        if (dropdownListGO == null) return;

        Transform content = dropdownListGO.transform.Find("Viewport/Content");
        if (content == null) return;

        ScrollRect scrollRect = dropdownListGO.GetComponentInChildren<ScrollRect>();

        for (int i = 1; i < content.childCount && i <= options.Count; i++) // i=1跳过模板
        {
            GameObject item = content.GetChild(i).gameObject;
            Toggle toggle = item.GetComponent<Toggle>();
            if (toggle != null)
            {
                toggle.SetIsOnWithoutNotify((i - 1) == currentOptionIndex);

                // 滚动到可见
                if ((i - 1) == currentOptionIndex && scrollRect != null)
                {
                    RectTransform itemRect = item.GetComponent<RectTransform>();
                    RectTransform contentRect = content.GetComponent<RectTransform>();

                    Vector2 localPos = contentRect.InverseTransformPoint(itemRect.position);
                    Vector2 viewportLocalPos = contentRect.InverseTransformPoint(scrollRect.viewport.position);

                    float offset = localPos.y - viewportLocalPos.y;
                    float normalized = 1 - Mathf.Clamp01((offset + itemRect.rect.height) / contentRect.rect.height);
                    scrollRect.verticalNormalizedPosition = normalized;
                }
            }
        }

        RefreshShownValue();
    }
}