using UnityEngine;
using UnityEngine.Rendering.Universal;

/// <summary>
/// Drifts the directional light's cookie so the caustic pattern it projects
/// onto the gravel, walls and fish wanders like light through a water surface.
/// </summary>
[RequireComponent(typeof(Light))]
public class CausticsScroll : MonoBehaviour
{
    public Vector2 drift = new Vector2(0.35f, 0.22f);
    [Tooltip("Slow wobble added to the drift so it never looks like a conveyor belt.")]
    public float wobble = 0.6f;
    UniversalAdditionalLightData data;
    Vector2 origin;

    void Start()
    {
        data = GetComponent<UniversalAdditionalLightData>();
        if (data != null) origin = data.lightCookieOffset;
    }

    void Update()
    {
        if (data == null) return;
        float t = Time.time;
        data.lightCookieOffset = origin + drift * t + new Vector2(Mathf.Sin(t * 0.37f), Mathf.Cos(t * 0.29f)) * wobble;
    }
}