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

public class TargetIndicator : MonoBehaviour
{
    public Camera mainCamera;              // 玩家摄像机
    public Transform target;               // 目标点
    public RectTransform uiCanvas;         // UI Canvas 的 RectTransform
    public RectTransform targetIcon;       // 目标图标的 UI
    public Text distanceText;              // 屏幕内显示的距离文本
    public RectTransform arrowIcon;        // 屏幕外箭头图标
    public Text arrowDistanceText;         // 屏幕外箭头后面的距离文本

    public float edgePadding = 50f;        // 箭头距离屏幕边缘的间距
    public Vector2 textOffset = new Vector2(0, -30); // 文本相对箭头的偏移

    void Update()
    {
        // 将目标点从世界坐标转换到屏幕坐标
        Vector3 screenPoint = mainCamera.WorldToScreenPoint(target.position);

        // 检查目标是否在屏幕内
        if (screenPoint.z > 0 && screenPoint.x > 0 && screenPoint.x < Screen.width && screenPoint.y > 0 && screenPoint.y < Screen.height)
        {
            // 目标在屏幕内，显示目标图标
            targetIcon.gameObject.SetActive(true);
            arrowIcon.gameObject.SetActive(false); // 隐藏箭头
            arrowDistanceText.gameObject.SetActive(false); // 隐藏箭头距离文本

            // 更新图标位置
            targetIcon.position = screenPoint;

            // 更新屏幕内距离文本
            float distance = Vector3.Distance(mainCamera.transform.position, target.position);
            distanceText.text = $"{distance:F1}m";
        }
        else
        {
            // 目标在屏幕外，显示箭头
            targetIcon.gameObject.SetActive(false);
            arrowIcon.gameObject.SetActive(true); // 显示箭头
            arrowDistanceText.gameObject.SetActive(true); // 显示箭头距离文本

            // 如果目标在玩家后方，翻转方向
            if (screenPoint.z < 0)
            {
                screenPoint.x = Screen.width - screenPoint.x; // 水平翻转
                screenPoint.y = Screen.height - screenPoint.y; // 垂直翻转
            }

            // 计算目标点相对于屏幕中心的方向
            Vector3 direction = (screenPoint - new Vector3(Screen.width / 2, Screen.height / 2, 0)).normalized;

            // 计算箭头在屏幕边界的位置
            Vector3 edgePosition = GetScreenEdgePosition(direction);

            // 设置箭头位置
            arrowIcon.position = edgePosition;

            // 设置距离文本位置（在箭头下方或后面）
            Vector3 textPosition = edgePosition + (Vector3)textOffset;
            textPosition = ClampToScreenBounds(textPosition); // 限制文本在屏幕范围内
            arrowDistanceText.transform.position = textPosition;

            // 保持距离文本水平显示
            arrowDistanceText.transform.rotation = Quaternion.identity;

            // 更新距离文本内容
            float distance = Vector3.Distance(mainCamera.transform.position, target.position);
            arrowDistanceText.text = $"{distance:F1}m";

            // 旋转箭头使其指向目标方向
            float angle = Mathf.Atan2(direction.y, direction.x) * Mathf.Rad2Deg;
            arrowIcon.rotation = Quaternion.Euler(0, 0, angle);
        }
    }

    // 计算箭头在屏幕边界的位置
    private Vector3 GetScreenEdgePosition(Vector3 direction)
    {
        // 计算屏幕宽高
        float halfScreenWidth = Screen.width / 2 - edgePadding;
        float halfScreenHeight = Screen.height / 2 - edgePadding;

        // 判断箭头是否应该在屏幕的上下边缘
        float slope = direction.y / direction.x;
        if (Mathf.Abs(slope) > halfScreenHeight / halfScreenWidth)
        {
            // 在上下边缘
            float edgeY = Mathf.Sign(direction.y) * halfScreenHeight + Screen.height / 2;
            float edgeX = (edgeY - Screen.height / 2) / slope + Screen.width / 2;
            return new Vector3(edgeX, edgeY, 0);
        }
        else
        {
            // 在左右边缘
            float edgeX = Mathf.Sign(direction.x) * halfScreenWidth + Screen.width / 2;
            float edgeY = slope * (edgeX - Screen.width / 2) + Screen.height / 2;
            return new Vector3(edgeX, edgeY, 0);
        }
    }

    // 限制文本在屏幕范围内
    private Vector3 ClampToScreenBounds(Vector3 position)
    {
        position.x = Mathf.Clamp(position.x, edgePadding, Screen.width - edgePadding);
        position.y = Mathf.Clamp(position.y, edgePadding, Screen.height - edgePadding);
        return position;
    }
}