using UnityEngine;

/// <summary>
/// Feeds fish-triggered ripple rings to the AFX/Water shader's _RippleData
/// array. A tiny fixed-size ring buffer of (worldX, worldZ, startTime,
/// strength); the shader ages and fades each slot itself, so this side just
/// records where and when a disturbance happened.
/// </summary>
[RequireComponent(typeof(Renderer))]
public class WaterRippleManager : MonoBehaviour
{
    public static WaterRippleManager Instance { get; private set; }

    const int Slots = 12;
    static readonly int RippleDataId = Shader.PropertyToID("_RippleData");

    Vector4[] data = new Vector4[Slots];
    int next;
    Material mat;
    bool dirty;

    void Awake()
    {
        Instance = this;
        mat = GetComponent<Renderer>().material;   // instance, since we mutate it every frame
    }

    void OnDestroy() { if (Instance == this) Instance = null; }

    /// <summary>Start a ripple ring expanding outward from this world position (Y ignored).</summary>
    public void Emit(Vector3 worldPos, float strength = 1f)
    {
        data[next] = new Vector4(worldPos.x, worldPos.z, Time.time, strength);
        next = (next + 1) % Slots;
        dirty = true;
    }

    void Update()
    {
        if (!dirty) return;
        mat.SetVectorArray(RippleDataId, data);
        // Cheap to just push every changed frame; ripples are infrequent (a few per second at most).
        dirty = false;
    }
}