using UnityEngine;

namespace Ragdoll
{
    // 单例的状态机
    public abstract class RdSingletonStateMachine<T, K> : RdStateMachine<T> where T : RdState where K : new()
    {
        private static K _instance;

        private static readonly object Lock = new object();

        public static K Instance
        {
            get
            {
                if (_instance == null)
                    // 上锁，防止重复实例化
                    lock (Lock)
                    {
                        _instance ??= new K();
                    }

                return _instance;
            }
        }
    }

    public abstract class RdStateMachine<T> where T : RdState
    {
        protected T currentState;

        protected abstract void Start();

        public virtual T GetCurState()
        {
            return currentState;
        }

        public virtual void TransitionToState(T nextState)
        {   
            Debug.Log("change state ->" + nextState.ToString());
            // 退出当前状态
            if (currentState != null)
            {
                currentState.ExitState();
            }

            // 切换到下一个状态
            currentState = nextState;

            // 进入下一个状态
            if (currentState != null)
            {
                currentState.EnterState();
            }
        }
    }

    public interface RdState
    {
        public abstract void EnterState();

        public abstract void ExitState();
    }
}