using UnityEngine;
using UnityEngine.UI;

[ExecuteInEditMode]
public class ObjectUILinker : MonoBehaviour
{
    [Tooltip("需要连接的3D物体")]
    public Transform object3D;  // 3D物体a

    [Tooltip("2D UI提示牌")]
    public RectTransform uiElement;  // 2D UI提示牌b

    [Tooltip("连线的颜色")]
    public Color lineColor = Color.red;

    [Tooltip("连线的宽度")]
    public float lineWidth = 2f;

    [Tooltip("编辑模式下是否显示连线")]
    public bool showInEditMode = true;

    [Tooltip("连线的渲染层级，值越大越靠上")]
    public int sortingOrder = 30000;

    private Image lineImage;
    private RectTransform lineRect;
    private Canvas canvas;
    private Camera mainCamera;
    private Canvas lineCanvas;

    void Awake()
    {
        SetupLineCanvas();
        SetupLineImage();
    }

    void Start()
    {
        UpdateReferences();
    }

    // 创建专门用于连线的Canvas
    void SetupLineCanvas()
    {
        // 查找或创建连线专用Canvas
        lineCanvas = GetComponent<Canvas>();
        if (lineCanvas == null)
        {
            lineCanvas = gameObject.AddComponent<Canvas>();
        }

        // 关键设置：确保Canvas在最上层
        lineCanvas.renderMode = RenderMode.ScreenSpaceOverlay;
        lineCanvas.overrideSorting = true;
        lineCanvas.sortingOrder = sortingOrder;

        // 添加必要的Canvas组件
        if (GetComponent<CanvasScaler>() == null)
        {
            CanvasScaler scaler = gameObject.AddComponent<CanvasScaler>();
            scaler.uiScaleMode = CanvasScaler.ScaleMode.ScaleWithScreenSize;
            scaler.referenceResolution = new Vector2(1920, 1080);
        }

        if (GetComponent<GraphicRaycaster>() == null)
        {
            gameObject.AddComponent<GraphicRaycaster>();
        }
    }

    // 创建用于显示连线的Image
    void SetupLineImage()
    {
        // 查找或创建连线Image
        lineImage = GetComponent<Image>();
        if (lineImage == null)
        {
            lineImage = gameObject.AddComponent<Image>();
        }

        // 使用纯色纹理作为连线
        lineImage.color = lineColor;
        lineImage.raycastTarget = false; // 确保连线不阻挡UI交互

        // 获取或创建RectTransform
        lineRect = GetComponent<RectTransform>();
        if (lineRect == null)
        {
            lineRect = gameObject.AddComponent<RectTransform>();
        }

        // 设置锚点，使连线位置计算更简单
        lineRect.anchorMin = Vector2.zero;
        lineRect.anchorMax = Vector2.zero;
        lineRect.pivot = new Vector2(0, 0.5f);
    }

    void Update()
    {
        // 实时更新渲染层级
        if (lineCanvas != null && lineCanvas.sortingOrder != sortingOrder)
        {
            lineCanvas.sortingOrder = sortingOrder;
        }

        // 根据运行状态和设置决定是否更新连线
        if (Application.isPlaying)
        {
            if (mainCamera == null) UpdateReferences();
            UpdateLine();
        }
        else
        {
            if (showInEditMode)
            {
                UpdateReferences();
                UpdateLine();
            }
        }
    }

    // 更新必要的引用
    void UpdateReferences()
    {
        if (mainCamera == null)
            mainCamera = Camera.main;

        if (uiElement != null && canvas == null)
            canvas = uiElement.GetComponentInParent<Canvas>();
    }

    // 更新连线的位置、角度和长度
    void UpdateLine()
    {
        // 检查必要引用
        if (object3D == null || uiElement == null || canvas == null || mainCamera == null)
        {
            if (lineImage != null)
                lineImage.enabled = false;
            return;
        }

        lineImage.enabled = true;

        // 将3D物体位置转换为屏幕坐标
        Vector3 objectScreenPos = mainCamera.WorldToScreenPoint(object3D.position);
        // 转换屏幕坐标为UI坐标（针对UI所在的Canvas）
        Vector2 objectUIPos;
        RectTransformUtility.ScreenPointToLocalPointInRectangle(
            canvas.GetComponent<RectTransform>(),
            objectScreenPos,
            canvas.worldCamera,
            out objectUIPos
        );
        // 转换为世界空间位置
        Vector3 worldPosA = canvas.GetComponent<RectTransform>().TransformPoint(objectUIPos);

        // 获取UI元素的世界空间位置
        Vector3 worldPosB = uiElement.position;

        // 将两个点转换为连线Canvas的局部坐标
        Vector2 localPosA = lineCanvas.GetComponent<RectTransform>().InverseTransformPoint(worldPosA);
        Vector2 localPosB = lineCanvas.GetComponent<RectTransform>().InverseTransformPoint(worldPosB);

        // 计算连线长度
        float distance = Vector2.Distance(localPosA, localPosB);

        // 计算连线角度
        float angle = Mathf.Atan2(localPosB.y - localPosA.y, localPosB.x - localPosA.x) * Mathf.Rad2Deg;

        // 设置连线位置（起点）
        lineRect.anchoredPosition = localPosA;

        // 设置连线旋转
        lineRect.rotation = Quaternion.Euler(0, 0, angle);

        // 设置连线尺寸
        lineRect.sizeDelta = new Vector2(distance, lineWidth);
    }

    // 在场景视图中绘制辅助线
    void OnDrawGizmos()
    {
        if (!showInEditMode) return;

        if (object3D != null && uiElement != null)
        {
            UpdateReferences();
            if (mainCamera == null || canvas == null) return;

            Gizmos.color = lineColor;

            Vector3 objectScreenPos = mainCamera.WorldToScreenPoint(object3D.position);
            Vector2 objectUIPos;

            if (RectTransformUtility.ScreenPointToLocalPointInRectangle(
                canvas.GetComponent<RectTransform>(),
                objectScreenPos,
                canvas.worldCamera,
                out objectUIPos))
            {
                Vector3 worldPosA = canvas.GetComponent<RectTransform>().TransformPoint(objectUIPos);
                Vector3 worldPosB = uiElement.position;
                Gizmos.DrawLine(worldPosA, worldPosB);
            }
        }
    }

    // 当属性变化时更新
    void OnValidate()
    {
        if (lineCanvas != null)
        {
            lineCanvas.sortingOrder = sortingOrder;
        }

        if (lineImage != null)
        {
            lineImage.color = lineColor;
        }
    }
}