using System;
using System.Collections.Concurrent;
using System.IO;
using UnityEngine;

namespace ShrinkModFramework
{
    [DefaultExecutionOrder(-2099)]
    internal sealed class ShrinkModRuntimeDriver : MonoBehaviour
    {
        private static ShrinkModRuntimeDriver _instance;

        private readonly ConcurrentQueue<Action> _mainThreadActions = new();
        private readonly ShrinkModReloadDebouncer _externalReloadDebouncer = new();
        private FileSystemWatcher _watcher;
        private ShrinkModFrameworkSettings _settings;

        public static void EnsureCreated(ShrinkModFrameworkSettings settings)
        {
            if (_instance)
            {
                _instance.ApplySettings(settings);
                return;
            }

            var go = new GameObject("ShrinkModRuntimeDriver");
            if (Application.isPlaying)
                DontDestroyOnLoad(go);
            _instance = go.AddComponent<ShrinkModRuntimeDriver>();
            _instance.ApplySettings(settings);
        }

        public static void Enqueue(Action action)
        {
            if (action == null)
                return;

            if (_instance == null)
                throw new InvalidOperationException("ShrinkModRuntimeDriver 尚未创建。");

            _instance._mainThreadActions.Enqueue(action);
        }

        internal static ShrinkModRuntimeDriver InstanceForTesting => _instance;

        internal bool HasWatcherForTesting => _watcher != null;

        internal void PumpForTesting() => Update();

        private void Update()
        {
            while (_mainThreadActions.TryDequeue(out var action))
            {
                try
                {
                    action();
                }
                catch (Exception ex)
                {
                    Debug.LogException(ex);
                }
            }

            if (!_externalReloadDebouncer.TryConsume(Time.realtimeSinceStartup))
                return;

            try
            {
                ShrinkModLoader.LoadNewExternalMods(_settings);
            }
            catch (Exception ex)
            {
                Debug.LogException(ex);
                Debug.LogError($"[ShrinkModFramework] 自动热加载外部模组失败：{ex.Message}");
            }
        }

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

        private void ApplySettings(ShrinkModFrameworkSettings settings)
        {
            _settings = settings ?? ShrinkModFrameworkSettings.Instance;

            if (_settings == null || !_settings.enableExternalDllMods || !_settings.watchExternalModsDirectory)
            {
                DisposeWatcher();
                return;
            }

            TrySetupWatcher();
        }

        private void TrySetupWatcher()
        {
#if ENABLE_IL2CPP && !UNITY_EDITOR
            return;
#else
            var directory = ShrinkExternalModAssemblyLoader.GetExternalModsDirectory(_settings);
            if (_settings.autoCreateExternalModsDirectory)
                Directory.CreateDirectory(directory);

            if (!Directory.Exists(directory))
                return;

            if (_watcher != null && string.Equals(_watcher.Path, directory, StringComparison.OrdinalIgnoreCase))
                return;

            DisposeWatcher();

            try
            {
                _watcher = new FileSystemWatcher(directory, "*.dll")
                {
                    IncludeSubdirectories = true,
                    NotifyFilter = NotifyFilters.FileName | NotifyFilters.LastWrite | NotifyFilters.CreationTime
                };
                _watcher.Created += OnExternalModsChanged;
                _watcher.Changed += OnExternalModsChanged;
                _watcher.Deleted += OnExternalModsChanged;
                _watcher.Renamed += OnExternalModsRenamed;
                _watcher.EnableRaisingEvents = true;
            }
            catch (Exception ex)
            {
                Debug.LogWarning($"[ShrinkModFramework] 外部模组目录监听启动失败：{ex.Message}");
                DisposeWatcher();
            }
#endif
        }

        private void OnExternalModsChanged(object sender, FileSystemEventArgs args)
        {
            ScheduleExternalReload(args.FullPath);
        }

        private void OnExternalModsRenamed(object sender, RenamedEventArgs args)
        {
            ScheduleExternalReload(args.OldFullPath);
            ScheduleExternalReload(args.FullPath);
        }

        private void ScheduleExternalReload(string path)
        {
            if (string.IsNullOrWhiteSpace(path))
                return;

            _mainThreadActions.Enqueue(() =>
            {
                var delay = _settings ? Mathf.Max(0.05f, _settings.externalModsReloadDelaySeconds) : 0.5f;
                _externalReloadDebouncer.Schedule(Time.realtimeSinceStartup, delay);
            });
        }

        private void DisposeWatcher()
        {
            if (_watcher == null)
                return;

            _watcher.EnableRaisingEvents = false;
            _watcher.Created -= OnExternalModsChanged;
            _watcher.Changed -= OnExternalModsChanged;
            _watcher.Deleted -= OnExternalModsChanged;
            _watcher.Renamed -= OnExternalModsRenamed;
            _watcher.Dispose();
            _watcher = null;
        }
    }
}