using UnityEngine;

/// <summary>
/// Gentle underwater sway for a tank plant, pivoting at its base, plus a push from the wake of
/// passing fish: a fish swimming close by nudges the plant along its direction of travel, and the
/// plant springs back and wobbles out. Put this on a pivot object at the plant's base.
/// </summary>
public class PlantSway : MonoBehaviour
{
    [Tooltip("Idle sway, degrees.")] public float idleDegrees = 2.5f;
    public float idleSpeed = 0.6f;
    [Tooltip("How far a fish's wake reaches, in world units.")] public float wakeRadius = 5f;
    [Tooltip("Tilt (degrees) from a fish passing at full speed right next to the plant.")] public float wakeDegrees = 18f;
    [Tooltip("Spring stiffness and damping for the wobble after a push.")] public float stiffness = 9f, damping = 2.2f;

    Quaternion rest;
    Vector2 tilt, tiltVel;   // x = tilt about world X (toward/away from glass), y = tilt about world Z (left/right)
    float phase;

    void Start()
    {
        rest = transform.localRotation;
        phase = Random.value * 10f;
    }

    void Update()
    {
        float dt = Time.deltaTime;
        if (dt <= 0f) return;

        // Wake: fish moving past push the plant along their velocity, stronger the closer and faster they are
        Vector2 push = Vector2.zero;
        Vector3 top = transform.position + Vector3.up * wakeRadius * 0.3f;
        foreach (var f in PaperFishController.Swimmers)
        {
            Vector3 d = f.Position - top;
            float dist = d.magnitude;
            if (dist > wakeRadius) continue;
            float k = 1f - dist / wakeRadius;
            Vector3 v = f.Velocity;
            push += new Vector2(v.z, -v.x) * k * k;   // lean along the flow
        }

        // Spring toward idle sway + wake push
        float t = Time.time * idleSpeed + phase;
        Vector2 idle = new Vector2(Mathf.Sin(t), Mathf.Sin(t * 0.77f + 1.3f)) * idleDegrees;
        Vector2 target = idle + Vector2.ClampMagnitude(push * 1.2f, wakeDegrees);
        Vector2 accel = (target - tilt) * stiffness - tiltVel * damping;
        tiltVel += accel * dt;
        tilt += tiltVel * dt;

        transform.localRotation = Quaternion.Euler(tilt.x, 0f, tilt.y) * rest;
    }
}