using UnityEngine;
using BaseGames.Core.Events;
using BaseGames.Core.Save;

namespace BaseGames.Core
{
    /// <summary>
    /// 难度管理器（单例 MonoBehaviour）。
    /// 统一管理当前难度档位，并通过事件频道广播变化。
    /// 订阅者通过 <see cref="CurrentScaler"/> 获取具体缩放数值。
    /// </summary>
    [DefaultExecutionOrder(-900)]
    public class DifficultyManager : MonoBehaviour, ISaveable, IDifficultyService
    {
        [SerializeField] private DifficultyScalerSO[]           _allScalers;
        [SerializeField] private DifficultyChangedEventChannel  _onDifficultyChanged;

        public DifficultyLevel    CurrentLevel  { get; private set; } = DifficultyLevel.Normal;
        public DifficultyScalerSO CurrentScaler { get; private set; }

        private void Awake()
        {
            if (ServiceLocator.GetOrDefault<IDifficultyService>() != null) { Destroy(gameObject); return; }
            ServiceLocator.Register<IDifficultyService>(this);
            Apply(DifficultyLevel.Normal);
            ServiceLocator.GetOrDefault<ISaveableRegistry>()?.Register(this);
        }

        private void OnDestroy()
        {
            ServiceLocator.Unregister<IDifficultyService>(this);
            ServiceLocator.GetOrDefault<ISaveableRegistry>()?.Unregister(this);
        }

        /// <summary>
        /// 在游戏流程中切换难度。
        /// SteelSoul 模式一旦选定，中途无法降级。
        /// </summary>
        public void ChangeDifficulty(DifficultyLevel level)
        {
            if (CurrentLevel == DifficultyLevel.SteelSoul && level != DifficultyLevel.SteelSoul)
            {
                Debug.LogWarning("[DifficultyManager] SteelSoul 模式无法在游戏中途降级。");
                return;
            }
            Apply(level);
        }

        /// <summary>按档位查找对应的缩放器，未配置时返回 null。</summary>
        public DifficultyScalerSO GetScaler(DifficultyLevel level)
        {
            if (_allScalers == null) return null;
            foreach (var s in _allScalers)
                if (s != null && s.Level == level) return s;
            return null;
        }

        private void Apply(DifficultyLevel level)
        {
            CurrentLevel  = level;
            CurrentScaler = GetScaler(level);
            _onDifficultyChanged?.Raise(CurrentLevel);
        }

        // ── ISaveable ────────────────────────────────────────────────────────

        public void OnSave(SaveData saveData)
        {
            if (saveData?.Meta != null)
                saveData.Meta.IsSteelSoul = CurrentLevel == DifficultyLevel.SteelSoul;
        }

        public void OnLoad(SaveData saveData)
        {
            if (saveData?.Meta != null && saveData.Meta.IsSteelSoul)
                Apply(DifficultyLevel.SteelSoul);
        }
    }
}