using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Newtonsoft.Json;
using UnityEngine;

namespace BaseGames.Core.Save
{
    /// <summary>
    /// 存档管理器。
    /// 完整序列化/反序列化由 Newtonsoft.Json 驱动。
    /// </summary>
    [DefaultExecutionOrder(-900)]
    public class SaveManager : MonoBehaviour, ISaveableRegistry
    {
        public const int QuickSaveSlot = 98;

        [Header("Event Channels - Raise")]
        [SerializeField] private BaseGames.Core.Events.BoolEventChannelSO _onSaveIndicatorVisible;

        private ISaveStorage _storage;
        private readonly HashSet<ISaveable> _saveables = new();
        private readonly SemaphoreSlim _saveLock = new SemaphoreSlim(1, 1);

        private SaveData _current;
        private int      _currentSlot = 0;
        public  int      CurrentSlot  => _currentSlot;

        public string LastCheckpointScene   { get; private set; }
        public string LastCheckpointSpawnId { get; private set; }

        private static SaveManager _instance;

        private void Awake()
        {
            if (_instance != null) { Destroy(gameObject); return; }
            _instance = this;
            ServiceLocator.Register<ISaveableRegistry>(this);

            _storage = new LocalFileStorage();
        }

        // ── ISaveable 注册 ────────────────────────────────────────────────────
        public void Register(ISaveable s)   => _saveables.Add(s);
        public void Unregister(ISaveable s) => _saveables.Remove(s);

        // ── 存档 ──────────────────────────────────────────────────────────────
        public async Task SaveAsync(int slot = -1)
        {
            await _saveLock.WaitAsync();
            try
            {
                int targetSlot = slot < 0 ? _currentSlot : slot;
                _current ??= new SaveData();

                _onSaveIndicatorVisible?.Raise(true);
                var snapshot = _saveables.ToList();
                foreach (var s in snapshot) s.OnSave(_current);

                _current.Meta.LastSaved = DateTime.UtcNow.ToString("o");
                _current.Meta.SlotIndex = targetSlot;
                _current.Meta.SaveCount++;

                // 先清空 checksum，序列化并计算，再序列化含 checksum 的最终版本
                // 使用 Formatting.None 减少序列化字符串体积和 GC 分配
                _current.Meta.Checksum = null;
                string jsonForChecksum = JsonConvert.SerializeObject(_current, Formatting.None);
                _current.Meta.Checksum = ComputeChecksum(jsonForChecksum);
                string finalJson = JsonConvert.SerializeObject(_current, Formatting.None);

                await _storage.WriteAsync(targetSlot, finalJson);

                LastCheckpointScene   = _current.Player?.Scene;
                LastCheckpointSpawnId = _current.Meta?.SavePointId;

                _onSaveIndicatorVisible?.Raise(false);
            }
            finally
            {
                _saveLock.Release();
            }
        }

        // ── 读档 ──────────────────────────────────────────────────────────────
        public async Task<bool> LoadAsync(int slot)
        {
            await _saveLock.WaitAsync();
            try
            {
                if (!_storage.Exists(slot)) return false;

                string json = await _storage.ReadAsync(slot);
                if (json == null) return false;

                SaveData loaded;
                try { loaded = JsonConvert.DeserializeObject<SaveData>(json); }
                catch (Exception e)
                {
                    Debug.LogError($"[SaveManager] 存档解析失败 slot={slot}: {e.Message}");
                    return false;
                }

                if (!ValidateChecksum(loaded, json))
                {
                    Debug.LogWarning("[SaveManager] 存档 checksum 校验失败。");
                    // 非 SteelSoul 模式仍允许加载（只是警告）
                }

                loaded = SaveMigrator.Migrate(loaded);
                _current     = loaded;
                _currentSlot = slot;

                var snapshot = _saveables.ToList();
                foreach (var s in snapshot) s.OnLoad(_current);

                LastCheckpointScene   = _current.Player?.Scene;
                LastCheckpointSpawnId = _current.Meta?.SavePointId;
                return true;
            }
            finally
            {
                _saveLock.Release();
            }
        }

        public bool SlotExists(int slot) => _storage.Exists(slot);
        public IEnumerable<int> GetExistingSlots() => _storage.GetExistingSlots();

        // ── 具名数据访问器（替代直接访问 Data 属性） ──────────────────────────────────
        /// <summary>判断指定收藏物 ID 是否已拾取。</summary>
        public bool IsWorldCollected(string id)
            => _current?.World.CollectedIds.Contains(id) == true;

        /// <summary>判断指定门 / 进程锁 ID 是否已开启。</summary>
        public bool IsDoorOpened(string id)
            => _current?.World.OpenedDoors.Contains(id) == true;

        /// <summary>返回当前存档中玩家最大 HP（存档未加载时返回 0）。</summary>
        public int GetPlayerMaxHP() => _current?.Player.MaxHP ?? 0;

        // ── 快速存档（挑战房间用）────────────────────────────────────────────
        public void QuickSave() => RunFireAndForget(SaveAsync(QuickSaveSlot), "QuickSave");
        public void QuickLoad() => RunFireAndForget(LoadAsync(QuickSaveSlot), "QuickLoad");

        /// <summary>
        /// 将 async Task 包裹为 async void，捕获所有异常并输出到 Log。
        /// 用于无法 await 的调用点（按钮回调、MonoBehaviour 方法等）。
        /// </summary>
        private static async void RunFireAndForget(Task task, string context)
        {
            try { await task; }
            catch (Exception e)
            {
                Debug.LogError($"[SaveManager] {context} 失败: {e.Message}\n{e.StackTrace}");
            }
        }

        // ── 世界标志 / EventChain ─────────────────────────────────────────────
        public bool   GetFlag(string flagId)
            => _current?.EventChains.WorldFlags.TryGetValue(flagId, out var v) == true && v;
        public void   SetFlag(string flagId, bool value)
        { _current ??= new SaveData(); _current.EventChains.WorldFlags[flagId] = value; }

        public void SetChainCompleted(string chainId)
        { _current ??= new SaveData(); _current.EventChains.ChainStates[chainId] = "Completed"; }
        public IEnumerable<string> GetCompletedChains()
            => _current?.EventChains.ChainStates.Keys ?? Enumerable.Empty<string>();

        public bool IsFirstClear(string challengeId)
        {
            if (_current == null) return false;
            if (_current.World.ChallengeFirstClears.Contains(challengeId)) return false;
            _current.World.ChallengeFirstClears.Add(challengeId);
            return true;
        }
        public bool IsBossDefeated(string bossId)
            => _current?.World.DefeatedBossIds.Contains(bossId) == true;

        // ── 存档槽摘要 ────────────────────────────────────────────────────────
        public async Task<SlotSummary> GetSlotSummaryAsync(int slotIndex)
        {
            if (!_storage.Exists(slotIndex)) return null;
            string json = await _storage.ReadAsync(slotIndex);
            if (json == null) return null;
            try
            {
                var data = JsonConvert.DeserializeObject<SaveData>(json);
                return new SlotSummary
                {
                    SlotIndex    = slotIndex,
                    Playtime     = data.Meta.Playtime,
                    LastSaved    = data.Meta.LastSaved,
                    SceneName    = data.Player?.Scene,
                    ActiveFormId = data.Player?.ActiveFormId,
                };
            }
            catch { return null; }
        }

        public void CreateSlot(int slotIndex)
        {
            _currentSlot = slotIndex;
            _current     = new SaveData();
            _current.Meta.SlotIndex = slotIndex;
        }

        public async Task DeleteSlotAsync(int slotIndex)
        {
            await _storage.DeleteAsync(slotIndex);
            if (_currentSlot == slotIndex) _current = null;
        }

        /// <summary>
        /// 将紧急存档槽的数据复制到目标槽，并删除紧急存档。
        /// 由 <see cref="EmergencySaveService"/> 调用，确保所有 IO 操作通过统一的 ISaveStorage 进行。
        /// </summary>
        public async Task PromoteEmergencyToSlotAsync(int targetSlot, int emergencySlot)
        {
            if (!_storage.Exists(emergencySlot)) return;
            string json = await _storage.ReadAsync(emergencySlot);
            if (json == null) return;
            await _storage.WriteAsync(targetSlot, json);
            await _storage.DeleteAsync(emergencySlot);
        }

        // ── 私有工具 ──────────────────────────────────────────────────────────
        private string ComputeChecksum(string json)
        {
            var keyBytes  = System.Text.Encoding.UTF8.GetBytes(GetHmacKey());
            using var hmac = new System.Security.Cryptography.HMACSHA256(keyBytes);
            var dataBytes = System.Text.Encoding.UTF8.GetBytes(json);
            return Convert.ToBase64String(hmac.ComputeHash(dataBytes));
        }

        private string GetHmacKey()
        {
            // ⚠️ 不使用 deviceUniqueIdentifier——设备唯一标识在玩家换设备时会改变，
            // 导致所有存档 checksum 永久失效。改用游戏固定密钥。
            const string gameSecret = "ZelingV2SaveIntegrity_v2_9a3f7c1b";
            return gameSecret;
        }

        private bool ValidateChecksum(SaveData data, string rawJson)
        {
            if (string.IsNullOrEmpty(data?.Meta?.Checksum)) return true;
            var saved = data.Meta.Checksum;
            data.Meta.Checksum = null;
            string jsonNoChecksum = JsonConvert.SerializeObject(data, Formatting.None);
            data.Meta.Checksum = saved;
            return ComputeChecksum(jsonNoChecksum) == saved;
        }

        private void OnDestroy()
        {
            if (_instance == this) _instance = null;
            ServiceLocator.Unregister<ISaveableRegistry>(this);
        }
    }
}