using Unity.Collections;
using Unity.Mathematics;
using System.Collections.Generic;
using UnityEngine;

public class CollisionEventManager : MonoBehaviour
{

    private List<int> currentlyCollidingBodies;
    private Dictionary<int, bool> collisionSubscribers;
    public Rigidbody debugBody;

    private void Awake(){
        collisionSubscribers = new Dictionary<int, bool>();
        currentlyCollidingBodies = new List<int>();
    }

    void Start(){
        SubscribeToCollisionEvents(debugBody);
        Physics.ContactModifyEvent += ModificationCallback;
    }
    void FixedUpdate() => DetectCollisonExitsBasic();

    private void OnDisable() => Physics.ContactModifyEvent -= ModificationCallback;

    public void SubscribeToCollisionEvents(Rigidbody rigidbody)
    {
        collisionSubscribers.Add(rigidbody.GetInstanceID(), false);
        foreach (Collider col in rigidbody.GetComponentsInChildren<Collider>())
        {
            col.hasModifiableContacts = true;
        }
        foreach (Collider col in rigidbody.GetComponents<Collider>())
        {
            col.hasModifiableContacts = true;
        }
    }
    public void ModificationCallback(PhysicsScene scene, NativeArray<ModifiableContactPair> contactPairs)
    {
        foreach (var pair in contactPairs)
        {
            if (collisionSubscribers.ContainsKey(pair.bodyInstanceID))
                DetectCollisionEventBasic(pair, pair.bodyInstanceID);

            if (collisionSubscribers.ContainsKey(pair.otherBodyInstanceID))
                DetectCollisionEventBasic(pair, pair.otherBodyInstanceID);
        }
    }

    private void DetectCollisionEventBasic(ModifiableContactPair pair, int thisID)
    {
        float minSeparation = 1f;
        for (int i = 0; i < pair.contactCount; i++)
            minSeparation = math.min(pair.GetSeparation(i), minSeparation);
        // this conditional logic is about the simplest way to determine event triggers
        if (!currentlyCollidingBodies.Contains(thisID))
        {
            if (minSeparation <= 0.05f)
            {
                currentlyCollidingBodies.Add(thisID);
                collisionSubscribers[thisID] = true;
                Debug.Log("entered");
            }
        }
        else if (minSeparation <= 0.05f)
        {
            Debug.Log("stayed");
            collisionSubscribers[thisID] = true;
        }
    }
    public void DetectCollisonExitsBasic()
    {
        for (int i = 0; i < currentlyCollidingBodies.Count; i++)
        {
            if (!collisionSubscribers[currentlyCollidingBodies[i]])
            {
                collisionSubscribers[currentlyCollidingBodies[i]] = false;
                  Debug.Log("exited");
                currentlyCollidingBodies.RemoveAt(i);
            }
            else
            {
                collisionSubscribers[currentlyCollidingBodies[i]] = false;
            }
        }
    }
}