using System;
using System.Collections;

namespace AibisDream.Framework
{
    public class StateMachine<T> where T : Enum
    {
        public T CurState => _curState.GetState;
        public bool HasState => _curState != null;
        public IState<T> CurrentStateObj => _curState;
        public event Action<T> OnStateSwitch;

        private IState<T> _curState;
        private readonly Func<T, string, IState<T>> _createState;

        public StateMachine(Func<T, string, IState<T>> createState)
        {
            _createState  = createState;
        }

        public IEnumerator Init(T initState)
        {
            return SwitchState(initState);
        }

        public IEnumerator SwitchState(T nextState, string args = "")
        {
            if (_curState != null && CurState.Equals(nextState)) yield break;

            yield return _curState?.Exit();
            _curState = _createState.Invoke(nextState, args);
            OnStateSwitch?.Invoke(nextState);
            yield return _curState.Enter();
        }

        /// <summary>
        /// 强制设置内部状态对象，不触发 Exit / Enter / OnStateSwitch。
        /// 用于读档等需要绕过正常状态过渡的场景。
        /// </summary>
        public void SetStateImmediate(T state, string args = "")
        {
            _curState = _createState.Invoke(state, args);
        }

        /// <summary>
        /// 读档恢复：跳过前一状态的 Exit，直接进入目标状态的 EnterImmediate。
        /// </summary>
        public IEnumerator SwitchStateImmediate(T nextState, string args = "")
        {
            if (_curState != null && CurState.Equals(nextState)) yield break;

            _curState = _createState.Invoke(nextState, args);
            OnStateSwitch?.Invoke(nextState);
            yield return _curState.EnterImmediate();
        }

        public IEnumerator QuitState()
        {
            yield return _curState?.Exit();
            _curState = null;
        }
    }
    
    public interface IState<out T> where T : Enum
    {
        public T GetState { get; }
        public void SetArgs(string args) {}
        public IEnumerator Enter();

        /// <summary>读档恢复：跳过过渡动画，直接到达终态。</summary>
        public IEnumerator EnterImmediate()
        {
            yield break;
        }

        public IEnumerator Exit()
        {
            yield break;
        }
    }
}