using UnityEngine;

public class DistanceLOD : MonoBehaviour
{
    [SerializeField] private float updateDelay = 0.1f;
    [SerializeField] private float cullDistance = 10f;
    [SerializeField] private Renderer[] renderers;
    [SerializeField] private Vector3 center = Vector3.zero;
    [SerializeField] private Vector3 size = Vector3.one;
    private float distance;
    private Bounds bounds;
    private Camera mainCamera;

    private void Awake()
    {
        mainCamera = Camera.main;
    }

    private void OnEnable()
    {
        InvokeRepeating("OnUpdate", 0f, updateDelay);
    }

    private void OnDisable()
    {
        CancelInvoke("OnUpdate");
    }

    private void OnUpdate()
    {
        UpdateDistance();
        EnableRenderers(cullDistance > distance);
    }

    private void EnableRenderers(bool enable)
    {
        if (renderers == null)
        {
            return;
        }

        for (var i = 0; i < renderers.Length; ++i)
        {
            if (renderers[i] == null)
            {
                continue;
            }

            renderers[i].enabled = enable;
        }
    }

    private void UpdateDistance()
    {
        if (mainCamera == null)
        {
            return;
        }

        var camPosition = mainCamera.transform.position;

        if (bounds.Contains(camPosition))
        {
            distance = 0f;
        }
        else
        {
            var closestPoint = bounds.ClosestPoint(camPosition);
            distance = (closestPoint - camPosition).magnitude;
        }
    }

    private void UpdateBounds()
    {
        bounds = new Bounds(transform.TransformPoint(center), size);
    }

    private void OnDrawGizmos()
    {
        if (mainCamera == null)
        {
            mainCamera = Camera.main;
        }

        UpdateBounds();
        UpdateDistance();

        Gizmos.color = Color.cyan;
        Gizmos.DrawWireCube(bounds.center, bounds.size);

        if (mainCamera != null)
        {
            var camPosition = mainCamera.transform.position;
            var closestPoint = bounds.ClosestPoint(camPosition);
            Gizmos.DrawLine(camPosition, closestPoint);
        }
    }
}