using BigSpace.XRCore.Base;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class LinerMgr : MonoSingleton<LinerMgr>
{
    public Transform m_target;
    public float height = 0.5f;
    public float arrowLength = 0.5f;
    public float speed = 1f;
    public float groundHeight = 0.25f; // 地面导航时的高度
    public float startDistance = 2f; // 箭头起始距离（相机前方）
    public float backStartDistance = 5f; // 目标在后方时，箭头起始距离（更远）

    public GameObject arrowPrefab;
    private Vector3 target;

    private List<Transform> arrowList = new List<Transform>();

    private bool start = false;
    // Start is called before the first frame update
    public void SetPositions(Vector3 pos)
    {
        target = pos;
        UpdateArrow();
    }


    public void ShowArrow(bool display, Transform target)
    {
        if (display)
        {
            Vector3 pos = target.position;
            this.target = pos;
        }
        else
            DeActiveArrow();
        start = display;
    }
    public void DeActiveArrow()
    {
        start = false;
        arrowList.ForEach(o => o.gameObject.SetActive(false));
    }
    void Update()
    {
        if (start)
        {
            UpdateArrow();
        }
    }

    void UpdateArrow()
    {
        Vector3 actualTarget = target;
        
        // 统一使用地面导航模式
        Camera mainCamera = Camera.main;
        if (mainCamera == null)
        {
            mainCamera = FindObjectOfType<Camera>();
        }
        
        if (mainCamera != null && m_target != null)
        {
            actualTarget = m_target.position;
            
            // 计算目标相对于相机的方向
            Vector3 cameraPos = mainCamera.transform.position;
            Vector3 cameraForward = mainCamera.transform.forward;
            Vector3 toTarget = actualTarget - cameraPos;
            float distanceToTarget = toTarget.magnitude;
            Vector3 toTargetDir = toTarget.normalized;
            
            // 判断目标是否在相机后方（点积小于0表示在后方）
            float dotProduct = Vector3.Dot(cameraForward, toTargetDir);
            bool isBehind = dotProduct < 0f;
            
            // 计算箭头起始位置 - 始终在相机前方，这样玩家才能看到
            Vector3 startPos;
            if (isBehind)
            {
                // 目标在后方：箭头起始点在相机前方，但箭头会向后指
                // 使用更远的距离，让箭头更明显
                startPos = cameraPos + cameraForward * backStartDistance;
            }
            else
            {
                // 目标在前方或侧面：从相机前方开始，稍微偏向目标方向
                Vector3 startDir = Vector3.Slerp(cameraForward, toTargetDir, 0.3f).normalized;
                startPos = cameraPos + startDir * startDistance;
            }
            
            // 设置高度为接近地面的高度（目标高度 + 地面高度偏移）
            startPos.y = actualTarget.y + groundHeight;
            transform.position = startPos;
        }
        else if (m_target != null)
        {
            // 没有相机，使用目标位置
            actualTarget = m_target.position;
        }
        
        float distance = Vector3.Distance(transform.position, actualTarget);
        float radius = groundHeight / 2f + distance * distance / (8f * groundHeight);
        float diff = radius - groundHeight;
        float angle = 2f * Mathf.Acos(diff / radius);
        float length = angle * radius;
        float segmentAngle = arrowLength / radius * Mathf.Rad2Deg;

        Vector3 center = new Vector3(0, -diff, distance / 2f);

        int segmentsCount = (int)(length / arrowLength) + 1;

        ArrowInit(segmentsCount);

        float offset = Time.time * speed * segmentAngle;
        Vector3 firstSegmentPos =
            Quaternion.Euler(Mathf.Repeat(offset, segmentAngle), 0f, 0f) * (Vector3.zero - center) + center;


        for (int i = 0; i < segmentsCount; i++)
        {
            Vector3 pos = Quaternion.Euler(segmentAngle * i, 0f, 0f) * (firstSegmentPos - center) + center;
            arrowList[i].localPosition = pos;
            arrowList[i].localRotation = Quaternion.FromToRotation(Vector3.up, pos - center);

        }
        
        if (m_target != null)
        {
            transform.LookAt(actualTarget);
        }
    }
    
    void ArrowInit(int listCount)
    {
        while (arrowList.Count < listCount)
        {
            GameObject arrow = Instantiate(arrowPrefab, transform);
            arrowList.Add(arrow.transform);
        }

        for (int i = 0; i < arrowList.Count; i++)
        {
            GameObject arrow = arrowList[i].gameObject;
            if (arrow.activeSelf != i < listCount)
                arrow.SetActive(i < listCount);
        }
    }
}