using System.Collections.Generic;
using System.Threading;
using Cysharp.Threading.Tasks;
using SepCore.DataTable;
using SepCore.Definition;
using SepCore.Entity;
using GameFramework.Event;
using SepCore.AsyncTask;
using SepCore.CustomUtility;
using UnityEngine;
using UnityGameFramework.Runtime;

namespace SepCore.EnemyManager
{
    public class EnemyManagerComponent : GameFrameworkComponent
    {
        private const string EnemyGroupName = "Enemy";

        private EntityComponent _entity;
        private EnemyRegistry _enemyRegistry;
        private EnemySpawnScheduler _spawnScheduler;

        public IReadOnlyCollection<EntityBase> Enemies => _enemyRegistry?.Enemies;

        [SerializeField] private int _spawnEnemyMaxCount = 5000;
        [SerializeField] private int _spawnDistanceFromPlayer = 20;

        private int _currentSpawnEnemyId;
        private int _currentLevel;
        private float _duration;
        private float _baseDuration;

        private Transform _player;
        private ISpawnPositionStrategy _spawnPositionStrategy;
        private CancellationTokenSource _spawnCts;
        // 停战标志。OnReset 置 true，OnInit 置 false。
        // ShowEntity 请求一旦发出，取消 await 并不能阻止框架真正创建实体，
        // 这些在途敌人会在 OnReset 之后才出生（fire ShowEntitySuccess）。
        // 此时 _isStopped 为真，由 OnShowEntitySuccess 在出生瞬间兜底 Hide 掉。
        private bool _isStopped;

        public float SpawnRateScale => _spawnScheduler?.SpawnRateScale ?? 1f;
        public float BattleDuration => _duration;
        public float ElapsedBattleTime => _spawnScheduler?.ElapsedTime ?? 0f;
        public int CurrentEnemyCount => _enemyRegistry?.Count ?? 0;

        #region Lifecycle

        private void Start()
        {
            _entity = GameEntry.Entity;
            _enemyRegistry = new EnemyRegistry();
            _spawnScheduler = new EnemySpawnScheduler();
            _spawnCts = CancellationTokenSource.CreateLinkedTokenSource(destroyCancellationToken);

            GameEntry.Event.Subscribe(HideEntityCompleteEventArgs.EventId, OnHideEntityComplete);
            GameEntry.Event.Subscribe(ShowEntitySuccessEventArgs.EventId, OnShowEntitySuccess);
        }

        private void OnDestroy()
        {
            GameEntry.Event.Unsubscribe(HideEntityCompleteEventArgs.EventId, OnHideEntityComplete);
            GameEntry.Event.Unsubscribe(ShowEntitySuccessEventArgs.EventId, OnShowEntitySuccess);

            _spawnCts?.Dispose();
            _spawnCts = null;
            _enemyRegistry = null;
            _spawnScheduler?.Reset();
            _spawnScheduler = null;
            _entity = null;
        }

        public void OnInit(DRLevel level, Player player)
        {
            _isStopped = false;

            _player = player != null ? player.CachedTransform : null;
            _spawnPositionStrategy = new RandomCircleSpawnStrategy(_spawnDistanceFromPlayer);

            _baseDuration = level.Duration;
            _duration = _baseDuration;
            _currentLevel = level.Id;

            _spawnScheduler.Init(level, OnWaveSpawn);
            _enemyRegistry.Clear();
            _currentSpawnEnemyId = 0;
        }

        public void OnUpdate(float elapseSeconds, float realElapseSeconds)
        {
            _enemyRegistry.PruneInvalidEntries();
            _spawnScheduler.Tick(elapseSeconds);
        }

        private void OnWaveSpawn(EnemyType enemyType, int count)
        {
            for (int j = 0; j < count; j++)
            {
                SpawnEnemyAsync(enemyType).Forget();
            }
        }

        public void OnReset()
        {
            // 先置停战标志。Cancel() 会同步恢复在途的 SpawnEnemyAsync（enemy 拿不到引用，
            // 无法自行 hide），这些实体会延后出生，由 OnShowEntitySuccess 兜底。
            _isStopped = true;

            _spawnCts.Cancel();
            _spawnCts.Dispose();
            _spawnCts = CancellationTokenSource.CreateLinkedTokenSource(destroyCancellationToken);

            _spawnScheduler.Reset();

            ClearEnemies();
            _currentSpawnEnemyId = 0;
            _currentLevel = 0;
            _baseDuration = 0;
            _duration = 0;
        }

        #endregion

        private async UniTaskVoid SpawnEnemyAsync(EnemyType enemyType)
        {
            if (_player == null) return;

            if (_enemyRegistry.Count >= _spawnEnemyMaxCount) return;
            int entityId = _currentSpawnEnemyId++;

            var enemyData = EntityDataFactory.Create(entityId, enemyType, _currentLevel);
            enemyData.Position = _spawnPositionStrategy.GetSpawnPosition(_player);

            var ct = _spawnCts.Token;
            var (isCanceled, enemy) =
                await _entity.ShowEnemyAsync(enemyData, cancellationToken: ct).SuppressCancellationThrow();
            if (isCanceled || ct.IsCancellationRequested || enemy == null || !enemy.Available)
            {
                // 取消通常发生在 OnReset 期间，此时实体往往尚未出生，enemy 为 null 无法 hide。
                // 真正的兜底在 OnShowEntitySuccess：停战后出生的敌人会被立即 hide。
                if (enemy != null && enemy.Available)
                {
                    _entity.HideEntity(enemy);
                }

                return;
            }

            // await 恢复时若已停战，说明这是漏网的在途敌人，立即 hide，不注册。
            if (_isStopped)
            {
                _entity.HideEntity(enemy);
                return;
            }

            if (_player != null)
            {
                enemy.SetTarget(_player);
            }

            _enemyRegistry.Register(enemy);
        }

        private void ClearEnemies()
        {
            var enemies = new List<EntityBase>(_enemyRegistry.Enemies);
            foreach (var enemy in enemies)
            {
                if (enemy == null || !enemy.Available) continue;
                _entity.HideEntity(enemy);
            }

            _enemyRegistry.Clear();
        }

        public bool TryGetEnemy(int entityId, out EntityBase enemy)
        {
            return _enemyRegistry.TryGet(entityId, out enemy);
        }

        public void SetSpawnRateScale(float scale)
        {
            _spawnScheduler.SetSpawnRateScale(scale);
        }

        #region Event Handler

        private void OnHideEntityComplete(object sender, GameEventArgs e)
        {
            if (e is not HideEntityCompleteEventArgs ne) return;

            string entityGroupName = ne.EntityGroup.Name;
            if (entityGroupName == EnemyGroupName)
            {
                _enemyRegistry.Remove(ne.EntityId);
            }
        }

        private void OnShowEntitySuccess(object sender, GameEventArgs e)
        {
            if (e is not ShowEntitySuccessEventArgs ne) return;
            if (ne.Entity.EntityGroup?.Name != EnemyGroupName)
            {
                return;
            }

            // 停战窗口（Shop/LevelUp）期间不应存在任何敌人。OnReset 之前发出的在途
            // ShowEntity 请求会在此刻才真正出生，立即 hide 兜底。
            if (_isStopped)
            {
                _entity.HideEntity(ne.Entity.Id);
            }
        }

        #endregion
    }
}