using UnityEngine;
using UnityEngine.Events;
using UnityEngine.Serialization;

namespace R0bbie.Timeline.Events
{
    /// <summary>
    /// Register to the linked GameEvent scriptable object, and trigger any function assign to the unity event
    /// </summary>
    [AddComponentMenu("Timeline/Game Events/Event Listener")]
    public class GameEventListener : MonoBehaviour, IGameEventListener
    {
        // Exposed Variables
        
        [Header("Event Listener")]
        public bool registerAutomatically = true;
        public bool triggerOnce;
        
        [Space(10)]
        [FormerlySerializedAs("animationStateEvent")] 
        public GameEvent gameEvent;
        public UnityEvent response = new UnityEvent();
        
        // Private Variables
        
        bool registered;
        bool triggered;
        
        
        void OnEnable()
        {
            if (!gameEvent)
                return;

            // If is not set to registered automatically, and haven't been registered yet, do nothing
            if (!registerAutomatically && !registered)
                return;

            // If already triggered, do nothing
            if (triggerOnce && triggered)
                return;
            
            Register();
        }

        
        void OnDisable()
        {
            // If there is no game event attached at the moment the object is disabled, do nothing
            if (!gameEvent)
                return;
            
            // Unregister listener but remember status
            gameEvent.UnregisterListener(this);
        }

        
        public void OnEventRaised()
        {
            // If for some reason the event is still registered when it shouldn't, do nothing
            if (triggerOnce && triggered)
                return;
            
            triggered = true;
            
            response?.Invoke();

            // Unregister and disable to avoid calling onDisable when unloading the level
            if (triggerOnce)
                Unregister();
        }
        

        public void Register()
        {
            gameEvent.RegisterListener(this);
            registered = true;
        }

        
        public void Unregister()
        {
            gameEvent.UnregisterListener(this);
            registered = false;
        }
        
        
    }
}