using System.Collections.Generic;
using Unity.Entities;
using Unity.Sample.Core;

/// <summary>
/// Light weight state machine
/// </summary>
/// <typeparam name="T"></typeparam>

class StateMachine<T>
{
    public delegate void StateFunc();

    public void Add(T id, StateFunc enter, StateFunc update, StateFunc leave)
    {
        m_States.Add(id, new State(id, enter, update, leave));
    }

    public T CurrentState()
    {
        return m_CurrentState.Id;
    }

    public void Update()
    {
        m_CurrentState.Update();
    }

    public void Shutdown()
    {
        if (m_CurrentState != null && m_CurrentState.Leave != null)
            m_CurrentState.Leave();
        m_CurrentState = null;
    }

    public void SwitchTo(World world,T state)
    {
        GameDebug.Assert(m_States.ContainsKey(state), "Trying to switch to unknown state " + state.ToString());
        GameDebug.Assert(m_CurrentState == null || !m_CurrentState.Id.Equals(state), "Trying to switch to " + state.ToString() + " but that is already current state");

        var newState = m_States[state];
        GameDebug.Log(world, null, "Switching state: " + (m_CurrentState != null ? m_CurrentState.Id.ToString() : "null") + " -> " + state.ToString());

        if (m_CurrentState != null && m_CurrentState.Leave != null)
            m_CurrentState.Leave();
        if (newState.Enter != null)
            newState.Enter();
        m_CurrentState = newState;
    }

    class State
    {
        public State(T id, StateFunc enter, StateFunc update, StateFunc leave)
        {
            Id = id;
            Enter = enter;
            Update = update;
            Leave = leave;
        }

        public T Id;
        public StateFunc Enter;
        public StateFunc Update;
        public StateFunc Leave;
    }

    State m_CurrentState = null;
    Dictionary<T, State> m_States = new Dictionary<T, State>();
}