WhiteMan_Unity2D/Assets/Hovl Studio/HSFiles/Scripts/HS_ParticleCollisionInstance.cs

using UnityEngine;
using System.Collections;
using System.Collections.Generic;

public class HS_ParticleCollisionInstance : MonoBehaviour
{
    public GameObject[] EffectsOnCollision;
    public float DestroyTimeDelay =5f;
    public bool UseWorldSpacePosition;
    public float Offset =0f;
    public Vector3 rotationOffset = new Vector3(0,0,0);
    public bool useOnlyRotationOffset = true;
    public bool UseFirePointRotation;
    public bool DestoyMainEffect = false;

    [Tooltip("Enable pooling to avoid Instantiate/Destroy spikes")]
    public bool UsePooling = true;

    [Tooltip("Maximum number of spawned effects processed per particle collision event (per OnParticleCollision call)")]
    public int MaxSpawnsPerCollisionCall =50;

    private ParticleSystem part;
    private List<ParticleCollisionEvent> collisionEvents = new List<ParticleCollisionEvent>();

    // Pooling
    private static Transform poolRoot;
    private Dictionary<GameObject, Queue<GameObject>> pools = new Dictionary<GameObject, Queue<GameObject>>();

    // Track instances that were spawned by this emitter and not yet returned to pool
    private HashSet<GameObject> activeInstances = new HashSet<GameObject>();

    void OnValidate()
    {
        if (DestroyTimeDelay <0f) DestroyTimeDelay =0f;
        if (MaxSpawnsPerCollisionCall <1) MaxSpawnsPerCollisionCall =1;
    }

    void Start()
    {
        part = GetComponent<ParticleSystem>();
        if (poolRoot == null)
        {
            var rootGO = GameObject.Find("[PS_Effect_Pool]");
            if (rootGO == null)
            {
                rootGO = new GameObject("[PS_Effect_Pool]");
                DontDestroyOnLoad(rootGO);
            }
            poolRoot = rootGO.transform;
        }
    }

    void OnParticleCollision(GameObject other)
    {
        if (part == null)
            part = GetComponent<ParticleSystem>();
        if (part == null)
            return; // nothing to do without particle system

        if (EffectsOnCollision == null || EffectsOnCollision.Length ==0)
            return;

        int numCollisionEvents = part.GetCollisionEvents(other, collisionEvents);
        int spawned =0;

        for (int i =0; i < numCollisionEvents; i++)
        {
            if (spawned >= MaxSpawnsPerCollisionCall)
                break; // throttle

            var hitPos = collisionEvents[i].intersection + collisionEvents[i].normal * Offset;

            foreach (var effect in EffectsOnCollision)
            {
                if (effect == null)
                    continue;

                if (spawned >= MaxSpawnsPerCollisionCall)
                    break;

                GameObject instance = null;
                if (UsePooling)
                    instance = GetPooledInstance(effect);
                else
                    instance = Instantiate(effect, hitPos, Quaternion.identity) as GameObject;

                if (instance == null)
                    continue;

                // Track as active so we can clean up if this emitter is destroyed
                activeInstances.Add(instance);

                // Position & rotation logic
                if (UseWorldSpacePosition)
                {
                    instance.transform.position = hitPos;
                }
                else
                {
                    // Keep world position consistent but do not parent to emitter to avoid accidental destruction.
                    // Compute local position relative to emitter and set world position accordingly.
                    var localPos = transform.InverseTransformPoint(hitPos);
                    instance.transform.position = transform.TransformPoint(localPos);
                }

                if (UseFirePointRotation)
                {
                    instance.transform.LookAt(transform.position);
                }
                else if (rotationOffset != Vector3.zero && useOnlyRotationOffset)
                {
                    instance.transform.rotation = Quaternion.Euler(rotationOffset);
                }
                else
                {
                    instance.transform.LookAt(collisionEvents[i].intersection + collisionEvents[i].normal);
                    instance.transform.rotation *= Quaternion.Euler(rotationOffset);
                }

                // Activate and play particle systems inside the effect
                instance.SetActive(true);
                PlayParticleSystemsRecursive(instance.transform);

                // Return to pool after a delay (or destroy if pooling disabled)
                if (UsePooling)
                    StartCoroutine(ReturnToPoolAfterDelay(effect, instance, DestroyTimeDelay));
                else
                    Destroy(instance, DestroyTimeDelay);

                spawned++;
            }
        }

        if (DestoyMainEffect == true)
        {
            Destroy(gameObject, DestroyTimeDelay +0.5f);
        }
    }

    // Play all particle systems in the spawned effect (in case of pooled ones they might be stopped)
    private void PlayParticleSystemsRecursive(Transform root)
    {
        var systems = root.GetComponentsInChildren<ParticleSystem>(true);
        foreach (var s in systems)
        {
            // Restart the system
            try
            {
                s.Clear();
                s.Play();
            }
            catch { }
        }
    }

    // Pool helpers
    private GameObject GetPooledInstance(GameObject prefab)
    {
        if (prefab == null)
            return null;

        Queue<GameObject> q;
        if (!pools.TryGetValue(prefab, out q) || q == null)
        {
            q = new Queue<GameObject>();
            pools[prefab] = q;
        }

        GameObject go = null;
        while (q.Count >0)
        {
            var candidate = q.Dequeue();
            if (candidate != null)
            {
                go = candidate;
                break;
            }
        }

        if (go == null)
        {
            go = Instantiate(prefab, poolRoot);
        }

        // ensure under pool root so it survives emitter destruction
        go.transform.SetParent(poolRoot, true);
        return go;
    }

    private IEnumerator ReturnToPoolAfterDelay(GameObject prefab, GameObject instance, float delay)
    {
        if (instance == null)
            yield break;

        // clamp delay
        if (delay <0f) delay =0f;
        yield return new WaitForSeconds(delay);

        if (instance == null)
            yield break;

        // stop particle systems
        var systems = instance.GetComponentsInChildren<ParticleSystem>(true);
        foreach (var s in systems)
        {
            try { s.Stop(true, ParticleSystemStopBehavior.StopEmittingAndClear); } catch { }
        }

        // deactivate and return to pool
        instance.SetActive(false);

        // Remove from active tracking for this emitter
        if (activeInstances.Contains(instance))
            activeInstances.Remove(instance);

        if (prefab == null)
        {
            Destroy(instance);
            yield break;
        }

        if (!pools.TryGetValue(prefab, out var q) || q == null)
            pools[prefab] = new Queue<GameObject>();

        pools[prefab].Enqueue(instance);
    }

    void OnDestroy()
    {
        // Destroy all active instances that were spawned by this emitter
        if (activeInstances != null)
        {
            foreach (var inst in activeInstances)
            {
                if (inst != null)
                    Destroy(inst);
            }
            activeInstances.Clear();
        }

        // Destroy all pooled objects created by this emitter
        if (pools != null)
        {
            foreach (var kv in pools)
            {
                var q = kv.Value;
                if (q == null) continue;
                while (q.Count >0)
                {
                    var go = q.Dequeue();
                    if (go != null)
                        Destroy(go);
                }
            }
            pools.Clear();
        }
    }
}