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

namespace BaseGames.Core.Save
{
    /// <summary>
    /// 存档管理器（Phase 0 骨架）。
    /// 完整序列化/反序列化由 Newtonsoft.Json 驱动。
    /// </summary>
    [DefaultExecutionOrder(-900)]
    public class SaveManager : MonoBehaviour
    {
        public static SaveManager Instance { get; private set; }

        public const string MinCompatibleVersion = "1.0";
        private const int   QuickSaveSlot        = 98;

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

        private ISaveStorage _storage;
        private readonly List<ISaveable> _saveables = new();

        private SaveData _current;
        private int      _currentSlot = 0;

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

        private void Awake()
        {
            if (Instance != null) { Destroy(gameObject); return; }
            Instance = 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)
        {
            int targetSlot = slot < 0 ? _currentSlot : slot;
            _current ??= new SaveData();

            _onSaveIndicatorVisible?.Raise(true);
            foreach (var s in _saveables) 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
            _current.Meta.Checksum = null;
            string jsonForChecksum = JsonConvert.SerializeObject(_current, Formatting.Indented);
            _current.Meta.Checksum = ComputeChecksum(jsonForChecksum);
            string finalJson = JsonConvert.SerializeObject(_current, Formatting.Indented);

            await _storage.WriteAsync(targetSlot, finalJson);

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

            _onSaveIndicatorVisible?.Raise(false);
        }

        // ── 读档 ──────────────────────────────────────────────────────────────
        public async Task<bool> LoadAsync(int slot)
        {
            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;

            foreach (var s in _saveables) s.OnLoad(_current);

            LastCheckpointScene   = _current.Player?.Scene;
            LastCheckpointSpawnId = _current.Meta?.SavePointId;
            return true;
        }

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

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

        // ── 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;
        }

        // ── 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()
        {
            string deviceId = SystemInfo.deviceUniqueIdentifier;
            const string salt = "ZelingV2SaveIntegrity_v1";
            return $"{deviceId}:{salt}";
        }

        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.Indented);
            data.Meta.Checksum = saved;
            return ComputeChecksum(jsonNoChecksum) == saved;
        }
    }
}