using Newtonsoft.Json;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Threading;
using WeldingCommon.Data.Services.History;

namespace WeldingCommon.Data.History
{
    public class SavedHistoryService<TKey, TIn, TView> : HistoryService<TKey, TView>, IHistoryWriter<TKey, TIn>
    {
        private readonly Func<TIn, TView> _projector;

        private readonly string _filePath;
        private readonly Func<TKey, string> _keyToString;
        private readonly Func<string, TKey> _stringToKey;

        private readonly DispatcherTimer _saveTimer;
        private volatile bool _dirty;

        public SavedHistoryService(string filePath, Func<TIn, TView> projector, int maxCount = 50, int pumpMs = 100, int saveDebounceMs = 500, Func<TKey, string> keyToString = null, Func<string, TKey> stringToKey = null)
        : base(maxCount, pumpMs)
        {
            _filePath = filePath ?? throw new ArgumentNullException(nameof(filePath));
            _projector = projector ?? throw new ArgumentNullException(nameof(projector));

            _keyToString = keyToString ?? (k => k.ToString());
            _stringToKey = stringToKey ?? DefaultStringToKey;

            Directory.CreateDirectory(Path.GetDirectoryName(_filePath));

            LoadFromDisk(); // base.Seed 사용

            _saveTimer = new DispatcherTimer(DispatcherPriority.Background) {
                Interval = TimeSpan.FromMilliseconds(saveDebounceMs)
            };
            _saveTimer.Tick += SaveTimer_Tick;
        }
        public void Append(TKey key, TIn snapshot)
        {
            var view = _projector(snapshot);
            base.Append(key, view); // 큐에 들어감 → Pump 후 컬렉션 반영
        }
        // Clear는 base 구현 그대로 사용(= TView 기준)
        public override void Clear(TKey key)
        {
            base.Clear(key);
            MarkDirtyAndScheduleSave();
        }

        protected override void OnChanged()
        {
            MarkDirtyAndScheduleSave();
        }

        private void MarkDirtyAndScheduleSave()
        {
            _dirty = true;
            if (!_saveTimer.IsEnabled)
                _saveTimer.Start();
        }

        private void SaveTimer_Tick(object sender, EventArgs e)
        {
            if (!_dirty) {
                _saveTimer.Stop();
                return;
            }

            SaveToDisk();
            _dirty = false;
            _saveTimer.Stop();
        }

        private void LoadFromDisk()
        {
            if (!File.Exists(_filePath))
                return;

            try {
                var json = File.ReadAllText(_filePath, Encoding.UTF8);
                var data = JsonConvert.DeserializeObject<Dictionary<string, List<TView>>>(json);
                if (data == null) return;

                foreach (var kv in data) {
                    var key = _stringToKey(kv.Key);
                    var list = kv.Value ?? new List<TView>();

                    // 저장 포맷을 "최신이 앞"으로 가정
                    Seed(key, list);
                }
            } catch {
                // 파일 손상/버전 문제면 무시하고 시작
            }
        }

        private void SaveToDisk()
        {
            Dictionary<string, List<TView>> snapshot;

            lock (_lock) {
                snapshot = _collections.ToDictionary(
                    kv => _keyToString(kv.Key),
                    kv => kv.Value.Take(500000).ToList()); // 여기서 maxCount 대신 큰 수 쓰지 말고, RollingCollection이 max를 유지하면 그냥 ToList도 OK
            }

            var json = JsonConvert.SerializeObject(snapshot, Formatting.Indented);

            var temp = _filePath + ".tmp";
            File.WriteAllText(temp, json, Encoding.UTF8);

            if (File.Exists(_filePath)) {
                var backup = _filePath + ".bak";
                File.Replace(temp, _filePath, backup, ignoreMetadataErrors: true);
            }
            else {
                File.Move(temp, _filePath);
            }
        }

        private TKey DefaultStringToKey(string s)
        {
            var t = typeof(TKey);
            if (t.IsEnum) return (TKey)Enum.Parse(t, s);
            if (t == typeof(string)) return (TKey)(object)s;

            throw new InvalidOperationException(
                $"TKey가 enum/string이 아니면 stringToKey 델리게이트를 제공해야 합니다. TKey={t.FullName}");
        }

        public override void Dispose()
        {
            _saveTimer.Stop();
            _saveTimer.Tick -= SaveTimer_Tick;

            if (_dirty)
                SaveToDisk();

            base.Dispose();
        }
    }
}