using System;
using System.Collections.Generic;
using System.Threading;
using UnityEngine;

public class WaveManager : MonoBehaviour
{
    [Header("Waves")]
    [SerializeField] private List<WaveData> _waves = new();
    [SerializeField] private float _intermissionDuration = 2f;
    [SerializeField] private bool _startOnAwake = true;

    [Header("Spawn Position")]
    [SerializeField] private Transform[] _spawnPoints;
    [SerializeField] private float _spawnRadius = 0f;
    [SerializeField] private Transform _enemyParent;

    [Header("On Defeat")]
    [SerializeField] private bool _destroyAliveEnemiesOnDefeat = true;

    public event Action<int, WaveData> OnWaveStart;
    public event Action<int> OnWaveCleared;
    public event Action OnAllWavesCleared;
    public event Action<int> OnDefeat;

    public int CurrentWaveIndex { get; private set; }
    public int TotalWaveCount => _waves != null ? _waves.Count : 0;
    public WaveData CurrentWave =>
        _waves != null && CurrentWaveIndex >= 0 && CurrentWaveIndex < _waves.Count
            ? _waves[CurrentWaveIndex]
            : null;
    public float TimeRemaining { get; private set; }
    public int AliveCount => _aliveEnemies.Count;
    public int RemainingToSpawn { get; private set; }
    public bool IsRunning { get; private set; }
    public bool IsDefeated { get; private set; }
    public bool IsVictory { get; private set; }

    private readonly List<Enemy> _aliveEnemies = new();
    private CancellationTokenSource _waveCts;

    private void Start()
    {
        if (_startOnAwake) StartWaves();
    }

    private void OnDestroy()
    {
        _waveCts?.Cancel();
        _waveCts?.Dispose();
    }

    public void StartWaves()
    {
        if (_waves == null || _waves.Count == 0) return;
        RunAllWaves();
    }

    public void StopWaves()
    {
        _waveCts?.Cancel();
        IsRunning = false;
    }

    private async void RunAllWaves()
    {
        _waveCts?.Cancel();
        _waveCts?.Dispose();
        _waveCts = CancellationTokenSource.CreateLinkedTokenSource(destroyCancellationToken);
        CancellationToken token = _waveCts.Token;

        IsDefeated = false;
        IsVictory = false;

        try
        {
            for (CurrentWaveIndex = 0; CurrentWaveIndex < _waves.Count; CurrentWaveIndex++)
            {
                WaveData wave = _waves[CurrentWaveIndex];
                if (wave == null) continue;

                if (wave.StartDelay > 0f)
                    await Awaitable.WaitForSecondsAsync(wave.StartDelay, token);

                OnWaveStart?.Invoke(CurrentWaveIndex, wave);
                bool cleared = await RunWave(wave, token);

                if (!cleared)
                {
                    IsDefeated = true;
                    OnDefeat?.Invoke(CurrentWaveIndex);
                    if (_destroyAliveEnemiesOnDefeat)
                        DestroyAliveEnemies();
                    return;
                }

                OnWaveCleared?.Invoke(CurrentWaveIndex);

                if (CurrentWaveIndex < _waves.Count - 1 && _intermissionDuration > 0f)
                    await Awaitable.WaitForSecondsAsync(_intermissionDuration, token);
            }

            IsVictory = true;
            OnAllWavesCleared?.Invoke();
        }
        catch (OperationCanceledException) { }
    }

    private async Awaitable<bool> RunWave(WaveData wave, CancellationToken token)
    {
        IsRunning = true;
        TimeRemaining = wave.TimeLimit;
        _aliveEnemies.Clear();

        int totalToSpawn = 0;
        foreach (var entry in wave.Spawns)
            if (entry != null) totalToSpawn += Mathf.Max(entry.Count, 0);
        RemainingToSpawn = totalToSpawn;

        // 적 스폰은 백그라운드로 흘려보내고, 본 루프는 시간/클리어만 체크.
        SpawnWaveEnemiesAsync(wave, token);

        while (true)
        {
            token.ThrowIfCancellationRequested();
            _aliveEnemies.RemoveAll(e => e == null);

            if (RemainingToSpawn == 0 && _aliveEnemies.Count == 0)
            {
                IsRunning = false;
                return true;
            }

            TimeRemaining -= Time.deltaTime;
            if (TimeRemaining <= 0f)
            {
                IsRunning = false;
                return false;
            }

            await Awaitable.NextFrameAsync(token);
        }
    }

    private async void SpawnWaveEnemiesAsync(WaveData wave, CancellationToken token)
    {
        try
        {
            foreach (var entry in wave.Spawns)
            {
                if (entry == null || entry.EnemyPrefab == null)
                {
                    RemainingToSpawn -= entry != null ? entry.Count : 0;
                    continue;
                }

                for (int i = 0; i < entry.Count; i++)
                {
                    token.ThrowIfCancellationRequested();
                    SpawnEnemy(entry.EnemyPrefab);
                    RemainingToSpawn--;

                    if (wave.SpawnInterval > 0f)
                        await Awaitable.WaitForSecondsAsync(wave.SpawnInterval, token);
                }
            }
        }
        catch (OperationCanceledException) { }
    }

    private void SpawnEnemy(Enemy prefab)
    {
        Vector3 position = GetSpawnPosition();
        Enemy enemy = Instantiate(prefab, position, Quaternion.identity, _enemyParent);
        _aliveEnemies.Add(enemy);
    }

    private Vector3 GetSpawnPosition()
    {
        Vector3 basePos;
        if (_spawnPoints != null && _spawnPoints.Length > 0)
        {
            Transform pick = _spawnPoints[UnityEngine.Random.Range(0, _spawnPoints.Length)];
            basePos = pick != null ? pick.position : transform.position;
        }
        else
        {
            basePos = transform.position;
        }

        if (_spawnRadius > 0f)
        {
            Vector2 offset = UnityEngine.Random.insideUnitCircle * _spawnRadius;
            basePos.x += offset.x;
            basePos.y += offset.y;
        }

        return basePos;
    }

    private void DestroyAliveEnemies()
    {
        for (int i = _aliveEnemies.Count - 1; i >= 0; i--)
        {
            if (_aliveEnemies[i] != null)
                Destroy(_aliveEnemies[i].gameObject);
        }
        _aliveEnemies.Clear();
    }

    private void OnGUI()
    {
        GUIStyle style = new GUIStyle(GUI.skin.box)
        {
            fontSize = 22,
            alignment = TextAnchor.MiddleCenter,
            richText = true,
            normal = { textColor = Color.white }
        };

        string text;
        if (IsVictory)
        {
            text = "<color=#88ff88><b>VICTORY</b></color>";
        }
        else if (IsDefeated)
        {
            text = $"<color=#ff8888><b>DEFEAT</b></color>\nWave {CurrentWaveIndex + 1} timed out";
        }
        else if (IsRunning && CurrentWave != null)
        {
            string name = string.IsNullOrEmpty(CurrentWave.WaveName)
                ? $"Wave {CurrentWaveIndex + 1}/{TotalWaveCount}"
                : CurrentWave.WaveName;

            text = $"<b>{name}</b>\nTime: {TimeRemaining:F1}s\nEnemies: {AliveCount} (+{RemainingToSpawn} 대기)";
        }
        else
        {
            return;
        }

        GUI.Box(new Rect(Screen.width / 2f - 180f, 20f, 360f, 110f), text, style);
    }

    private void OnDrawGizmosSelected()
    {
        Color pointColor = Color.cyan;
        Color radiusColor = new Color(0f, 1f, 1f, 0.25f);

        if (_spawnPoints != null && _spawnPoints.Length > 0)
        {
            foreach (var p in _spawnPoints)
            {
                if (p == null) continue;
                Gizmos.color = pointColor;
                Gizmos.DrawWireSphere(p.position, 0.3f);
                if (_spawnRadius > 0f)
                {
                    Gizmos.color = radiusColor;
                    Gizmos.DrawWireSphere(p.position, _spawnRadius);
                }
            }
        }
        else
        {
            Gizmos.color = pointColor;
            Gizmos.DrawWireSphere(transform.position, 0.3f);
            if (_spawnRadius > 0f)
            {
                Gizmos.color = radiusColor;
                Gizmos.DrawWireSphere(transform.position, _spawnRadius);
            }
        }
    }
}