Event machine is a task or process that has both event-manager and state machine. It is for Unity.

EventMachine.cs

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

public class EventMachine {

    #region event manager
    protected EventManager m_evman;
    public EventManager    EventMan { get { return m_evman;  } }
    #endregion

    #region constructor
    public  StateManager m_sm { get; private set; }

    public EventMachine(Type t)
    {
        m_sm = (StateManager)Activator.CreateInstance(t);
        m_evman = new EventManager();
        m_sm.SetEventMan(m_evman);

    }
    #endregion

    #region Framework
    public void Start()
    {
        m_sm.Start();
    }
	public void Update () {
        m_evman.Update();
        m_sm.update();        	    	
	}
    public bool IsEnd()
    {
        return m_sm.IsEnd();
    }
    #endregion
}

EventManager.cs

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

public class EventManager {

    public Queue<object> m_eventlist { get; private set; }
    public object CUR { get; private set; }

    public bool existEvent { get { return m_eventlist!=null && m_eventlist.Count > 0; } }
    public int  countEvent { get { return m_eventlist!=null ? m_eventlist.Count : 0;  } }

    public EventManager()
    {
        m_eventlist = new Queue<object>();
        CUR = null;
    }

    public void Push(object @event)
    {
        if (m_eventlist==null) m_eventlist = new Queue<object>();
        m_eventlist.Enqueue(@event);
    }

    public void Update()
    {
        CUR = null;
        if (m_eventlist!=null && m_eventlist.Count>0)
        {
            CUR = m_eventlist.Dequeue();
        }
    }

}

StateManager.cs

using System;
using UnityEngine;
public class StateManager : StateManagerGetEventManInterface
{
    public EventManager m_eventman { get; private set; }

    Action<bool> m_curfunc;
    Action<bool> m_nextfunc;
    Action<bool> m_tempfunc;

    bool         m_noWait;
    
    public virtual void Start() { }
    public virtual bool IsEnd() {  return true; }

    public void SetEventMan(EventManager eventman) { m_eventman = eventman; }
    public EventManager GetEventMan() { return m_eventman; }

    public void update()
    {
        while(true)
        {
            var bFirst = false;
            if (m_nextfunc!=null)
            {
                m_curfunc = m_nextfunc;
                m_nextfunc = null;
                bFirst = true;

                Debug.Log("Into .. " + m_curfunc.Method.Name);
               
            }
            m_noWait = false;
            if (m_curfunc!=null)
            {   
                m_curfunc(bFirst);
            }
            if (!m_noWait) break;
        }
    }
    public void Goto(Action<bool> func)
    {
        m_nextfunc = func;
    }
    public bool CheckState(Action<bool> func)
    {
        return m_curfunc == func;
    }
    // for tempfunc
    public void SetNextState(Action<bool> func)
    {
        m_tempfunc = func;
    }
    public void GoNextState()
    {
        m_nextfunc = m_tempfunc;
        m_tempfunc = null;
    }
    public bool HasNextState()
    {
        return m_tempfunc != null;
    }
    public void NoWait()
    {
        m_noWait = true;
    }
}

StateManagerGetEventManInterface.cs

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

public interface StateManagerGetEventManInterface {
    EventManager GetEventMan();
}

Unity-Sample:Test.cs

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

public class Test : MonoBehaviour {

    EventMachine m_em;

	void Start () {
		m_em = new EventMachine(typeof(TestControl));
        m_em.Start();
	}
	
	void Update () {
		m_em.Update();
	}

    private void OnGUI()
    {
        if (GUILayout.Button("BUT A"))
        {
            m_em.EventMan.Push("BUT_A");
        }
        if (GUILayout.Button("BUT B"))
        {
            m_em.EventMan.Push("BUT_B");
        }
        if (GUILayout.Button("BUT C"))
        {
            m_em.EventMan.Push("BUT_C");
        }
    }
}

modified

add StateManagerGetEventManInterface.cs