using UnityEngine;

[DisallowMultipleComponent]
public class CoinVFXAdder : MonoBehaviour
{
    [Header("VFX Prefab (one-shot)")]
    public ParticleSystem vfxPrefab;

    [Header("Spawn Options")]
    public Vector3 spawnOffsetLocal;          // offset in source local space
    public bool inheritRotation = false;      // use source.rotation
    public Transform parentOverride;          // null = world

    [Header("Lifetime")]
    public bool autoDestroyIfNeeded = true;
    public float extraLifetime = 0.25f;

    /// <summary>Spawn at this component's transform (still supported).</summary>
    public void SpawnVFX()
    {
        SpawnAt(transform);
    }

    /// <summary>Spawn at a specific source (e.g., the coin), so this can sit on an ancestor.</summary>
    public void SpawnAt(Transform source)
    {
        if (!vfxPrefab || !source) return;

        Vector3 pos = source.TransformPoint(spawnOffsetLocal);
        Quaternion rot = inheritRotation ? source.rotation : Quaternion.identity;
        Transform parent = parentOverride ? parentOverride : null;

        var ps = Instantiate(vfxPrefab, pos, rot, parent);
        ps.Play(true);

        if (ps.main.stopAction == ParticleSystemStopAction.Destroy) return;

        if (autoDestroyIfNeeded)
        {
            Destroy(ps.gameObject, EstimateLifetime(ps) + extraLifetime);
        }
    }

    private static float EstimateLifetime(ParticleSystem ps)
    {
        var main = ps.main;
        float dur = main.duration;
        float lt = 0f;
        var c = main.startLifetime;

        switch (c.mode)
        {
            case ParticleSystemCurveMode.Constant:
                lt = c.constant; break;
            case ParticleSystemCurveMode.TwoConstants:
                lt = Mathf.Max(c.constantMin, c.constantMax); break;
            case ParticleSystemCurveMode.Curve:
                if (c.curve != null && c.curve.length > 0) lt = c.curve.keys[^1].time; break;
            case ParticleSystemCurveMode.TwoCurves:
                float a = (c.curveMin != null && c.curveMin.length > 0) ? c.curveMin.keys[^1].time : 0f;
                float b = (c.curveMax != null && c.curveMax.length > 0) ? c.curveMax.keys[^1].time : 0f;
                lt = Mathf.Max(a, b); break;
        }
        return dur + lt;
    }
}