Unity3D C# Event Manager

EventManager.cs

/*
* Copyright 2017 Ben D'Angelo
*
* MIT License
*
* Permission is hereby granted, free of charge, to any person obtaining a copy of this
* software and associated documentation files (the "Software"), to deal in the Software
* without restriction, including without limitation the rights to use, copy, modify, merge,
* publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
* to whom the Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all copies or
* substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED *AS IS*, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
* INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
* PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
* FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
* OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*/
using UnityEngine;
using System.Collections;
using System.Collections.Generic;

public class EventManager : MonoBehaviour {
    public bool LimitQueueProcesing = false;
    public float QueueProcessTime = 0.0f;
    private static EventManager s_Instance = null;
    private Queue m_eventQueue = new Queue();

    public delegate void EventDelegate<T> (T e) where T : GameEvent;
    private delegate void EventDelegate (GameEvent e);

    private Dictionary<System.Type, EventDelegate> delegates = new Dictionary<System.Type, EventDelegate>();
    private Dictionary<System.Delegate, EventDelegate> delegateLookup = new Dictionary<System.Delegate, EventDelegate>();
    private Dictionary<System.Delegate, System.Delegate> onceLookups = new Dictionary<System.Delegate, System.Delegate>();

    // override so we don't have the typecast the object
    public static EventManager Instance {
        get {
            if (s_Instance == null) {
                s_Instance = GameObject.FindObjectOfType (typeof(EventManager)) as EventManager;
            }
            return s_Instance;
        }
    }

    private EventDelegate AddDelegate<T>(EventDelegate<T> del) where T : GameEvent {
        // Early-out if we've already registered this delegate
        if (delegateLookup.ContainsKey(del))
            return null;

        // Create a new non-generic delegate which calls our generic one.
        // This is the delegate we actually invoke.
        EventDelegate internalDelegate = (e) => del((T)e);
        delegateLookup[del] = internalDelegate;

        EventDelegate tempDel;
        if (delegates.TryGetValue(typeof(T), out tempDel)) {
            delegates[typeof(T)] = tempDel += internalDelegate; 
        } else {
            delegates[typeof(T)] = internalDelegate;
        }

        return internalDelegate;
    }

    public void AddListener<T> (EventDelegate<T> del) where T : GameEvent {
        AddDelegate<T>(del);
    }

    public void AddListenerOnce<T> (EventDelegate<T> del) where T : GameEvent {
        EventDelegate result = AddDelegate<T>(del);

        if(result != null){
            // remember this is only called once
            onceLookups[result] = del;
        }
    }

    public void RemoveListener<T> (EventDelegate<T> del) where T : GameEvent {
        EventDelegate internalDelegate;
        if (delegateLookup.TryGetValue(del, out internalDelegate)) {
            EventDelegate tempDel;
            if (delegates.TryGetValue(typeof(T), out tempDel)){
                tempDel -= internalDelegate;
                if (tempDel == null){
                    delegates.Remove(typeof(T));
                } else {
                    delegates[typeof(T)] = tempDel;
                }
            }

            delegateLookup.Remove(del);
        }
    }

    public void RemoveAll(){
        delegates.Clear();
        delegateLookup.Clear();
        onceLookups.Clear();
    }

    public bool HasListener<T> (EventDelegate<T> del) where T : GameEvent {
        return delegateLookup.ContainsKey(del);
    }

    public void TriggerEvent (GameEvent e) {
        EventDelegate del;
        if (delegates.TryGetValue(e.GetType(), out del)) {
            del.Invoke(e);

            // remove listeners which should only be called once
            foreach(EventDelegate k in delegates[e.GetType()].GetInvocationList()){
                if(onceLookups.ContainsKey(k)){
                    delegates[e.GetType()] -= k;

                    if(delegates[e.GetType()] == null)
                    {
                        delegates.Remove(e.GetType());
                    }

                    delegateLookup.Remove(onceLookups[k]);
                    onceLookups.Remove(k);
                }
            }
        } else {
            Debug.LogWarning("Event: " + e.GetType() + " has no listeners");
        }
    }

    //Inserts the event into the current queue.
    public bool QueueEvent(GameEvent evt) {
        if (!delegates.ContainsKey(evt.GetType())) {
            Debug.LogWarning("EventManager: QueueEvent failed due to no listeners for event: " + evt.GetType());
            return false;
        }

        m_eventQueue.Enqueue(evt);
        return true;
    }

    //Every update cycle the queue is processed, if the queue processing is limited,
    //a maximum processing time per update can be set after which the events will have
    //to be processed next update loop.
    void Update() {
        float timer = 0.0f;
        while (m_eventQueue.Count > 0) {
            if (LimitQueueProcesing) {
                if (timer > QueueProcessTime)
                    return;
            }

            GameEvent evt = m_eventQueue.Dequeue() as GameEvent;
            TriggerEvent(evt);

            if (LimitQueueProcesing)
                timer += Time.deltaTime;
        }
    }

    public void OnApplicationQuit(){
        RemoveAll();
        m_eventQueue.Clear();
        s_Instance = null;
    }
}