using System.Collections;
using UnityEngine;
using BaseGames.Core.Events;
using BaseGames.Core.States;

namespace BaseGames.Core
{
    /// <summary>
    /// 全局游戏管理器。
    /// 生命周期：Persistent → 第一个执行（DefaultExecutionOrder(-1000)）。
    /// 持有 <see cref="GameStateMachine"/> 并协调所有顶层服务。
    /// </summary>
    [DefaultExecutionOrder(-1000)]
    public class GameManager : MonoBehaviour
    {
        // ── Inspector 引用 ────────────────────────────────────────────────
        [Header("Managers")]
        [SerializeField] private SettingsManager    _settingsManager;

        [Header("Event Channels - Listen")]
        [SerializeField] private VoidEventChannelSO   _onPlayerDied;
        [SerializeField] private VoidEventChannelSO   _onPauseRequested;
        [SerializeField] private VoidEventChannelSO   _onResumeRequested;
        [SerializeField] private StringEventChannelSO _onBossFightStarted;
        [SerializeField] private BoolEventChannelSO   _onBossFightEnded;
        [SerializeField] private VoidEventChannelSO   _onDeathScreenConfirmed;

        [Header("Event Channels - Raise")]
        [SerializeField] private BaseEventChannelSO<GameStateId> _onGameStateChanged;
        [SerializeField] private VoidEventChannelSO   _onPlayerRespawned;

        // ── 状态机 ────────────────────────────────────────────────────────
        private readonly GameStateMachine      _fsm  = new GameStateMachine();
        private readonly CompositeDisposable   _subs = new();
        public GameStateId CurrentState => _fsm.CurrentStateId;

        private static GameManager _instance;

        // ──────────────────────────────────────────────────────────────────
        private void Awake()
        {
            if (_instance != null) { Destroy(gameObject); return; }
            _instance = this;
            DontDestroyOnLoad(transform.root.gameObject);

            RegisterStates();
            _settingsManager?.Initialize();

            _fsm.TransitionTo(GameStates.Initializing, out _);
        }

        private void Start()
        {
            // 在 Start 广播初始状态，确保其他组件已在 OnEnable 中完成订阅。
            _onGameStateChanged?.Raise(new Events.GameStateId(GameStates.Initializing.Id));
        }

        private void OnEnable()
        {
            _onPlayerDied?          .Subscribe(HandlePlayerDied).AddTo(_subs);
            _onPauseRequested?      .Subscribe(HandlePauseRequested).AddTo(_subs);
            _onResumeRequested?     .Subscribe(HandleResumeRequested).AddTo(_subs);
            _onBossFightStarted?    .Subscribe(HandleBossFightStarted).AddTo(_subs);
            _onBossFightEnded?      .Subscribe(HandleBossFightEnded).AddTo(_subs);
            _onDeathScreenConfirmed?.Subscribe(HandleDeathScreenConfirmed).AddTo(_subs);
        }

        private void OnDisable() => _subs.Clear();

        private void OnDestroy()
        {
            if (_instance == this) _instance = null;
        }

        private void Update() => _fsm.Tick(Time.deltaTime);

        // ── 初始化 ────────────────────────────────────────────────────────
        private void RegisterStates()
        {
            _fsm.Register(new InitializingState());
            _fsm.Register(new MainMenuState());
            _fsm.Register(new LoadingSceneState());
            _fsm.Register(new GameplayState());
            _fsm.Register(new BossFightState());
            _fsm.Register(new PausedState());
            _fsm.Register(new DeadState());
            _fsm.Register(new CutsceneState());
            _fsm.Register(new GameOverState());
        }

        // ── 状态转换公共 API ──────────────────────────────────────────────
        public bool RequestTransition(GameStateId nextState)
        {
            if (_fsm.TransitionTo(nextState, out string error))
            {
                // 通知 UI 等监听者（GameStateId in Core.Events 是 string-based）
                _onGameStateChanged?.Raise(new Events.GameStateId(nextState.Id));
                return true;
            }
            Debug.LogWarning($"[GameManager] {error}");
            return false;
        }

        // ── 事件处理 ──────────────────────────────────────────────────────
        private void HandlePlayerDied()       => StartCoroutine(DeathFlow());
        private void HandlePauseRequested()
        {
            _prePauseState = _fsm.CurrentStateId;
            RequestTransition(GameStates.Paused);
        }

        private void HandleResumeRequested() => RequestTransition(_prePauseState);

        private void HandleBossFightStarted(string bossId)
            => RequestTransition(GameStates.BossFight);

        private void HandleBossFightEnded(bool victory)
        {
            if (victory) RequestTransition(GameStates.Gameplay);
            else         RequestTransition(GameStates.GameOver);
        }

        private bool        _deathScreenConfirmed;
        private GameStateId _prePauseState = GameStates.Gameplay;
        private void HandleDeathScreenConfirmed() => _deathScreenConfirmed = true;

        private IEnumerator DeathFlow()
        {
            RequestTransition(GameStates.Dead);
            var deathService = ServiceLocator.Get<IDeathRespawnService>();

            // SteelSoul 模式：清档后返回主菜单（架构 19 §6）
            var scaler = ServiceLocator.GetOrDefault<IDifficultyService>()?.CurrentScaler;
            if (scaler != null && scaler.InstantDeathOnZeroHP)
            {
                yield return deathService.StartGameOverCoroutine();
                yield break;
            }

            yield return deathService.StartDeathSequenceCoroutine();

            // 等待玩家在死亡画面点击重试
            _deathScreenConfirmed = false;
            yield return new WaitUntil(() => _deathScreenConfirmed);

            yield return deathService.StartRespawnCoroutine();
            RequestTransition(GameStates.LoadingScene);
            _onPlayerRespawned?.Raise();
        }
    }
}