using System.Collections.Generic;
using UnityEngine;

public class GameManager : MonoBehaviour
{
    public static GameManager Instance { get; private set; }

    [Header("Level Flow")]
    [SerializeField] private GameObject winScreenPrefab;
    [SerializeField] private GameObject gameOverScreenPrefab;

    [Header("Ball Queue")]
    [SerializeField] private GameObject ballPrefab;
    [SerializeField] private int initialBallCount = 5;
    [SerializeField] private Vector3 ballSpawnOffset = new Vector3(0f, 0.7f, 0f);
    [SerializeField] private Transform reserveAnchor;
    [SerializeField] private float reserveBallSpacing = 0.5f;
    [SerializeField] private Vector2 reserveStartViewport = new Vector2(0.92f, 0.12f);

    [Header("Random Effects")]
    [SerializeField] private BallEffectDefinition[] randomEffectPool;

    private readonly Queue<BallScript> _reserveBalls = new Queue<BallScript>();
    private Transform _paddle;
    private Camera _gameCamera;
    private bool _gameWon;
    private bool _gameOver;
    private BallScript _currentQueueBall;
    private int _remainingBlockCount;
    private UpgradeState _upgrades;

    void Awake()
    {
        if (Instance != null && Instance != this)
        {
            Destroy(gameObject);
            return;
        }
        Instance = this;

        Time.timeScale = 1f;
        Time.fixedDeltaTime = 0.01f;
        _upgrades = new UpgradeState();
    }

    void Start()
    {
        ResolveSceneReferences();
        _remainingBlockCount = FindObjectsByType<blockScript>(FindObjectsSortMode.None).Length;
        InitializeBallQueue();
    }

    public void OnBallEnteredDeathZone(BallScript ball)
    {
        if (_gameWon || _gameOver || ball == null)
            return;

        bool wasCurrentQueueBall = ball == _currentQueueBall;
        Destroy(ball.gameObject);

        if (HasOtherBallsInPlay(ball))
            return;

        if (wasCurrentQueueBall)
            _currentQueueBall = null;

        if (_reserveBalls.Count > 0)
        {
            MoveNextQueuedBallToPaddle();
            return;
        }

        ShowGameOver();
    }

    private bool HasOtherBallsInPlay(BallScript excludedBall)
    {
        BallScript[] balls = FindObjectsByType<BallScript>(FindObjectsSortMode.None);
        for (int i = 0; i < balls.Length; i++)
        {
            BallScript otherBall = balls[i];
            if (otherBall == null || otherBall == excludedBall)
                continue;

            if (otherBall.IsInPlay)
                return true;
        }

        return false;
    }

    /// <summary>Called by BlockScript when a block is destroyed.</summary>
    public void OnBlockDestroyed()
    {
        if (_gameWon || _gameOver)
            return;

        _remainingBlockCount = Mathf.Max(0, _remainingBlockCount - 1);
        if (_remainingBlockCount == 0)
            WinGame();
    }

    private void InitializeBallQueue()
    {
        if (ballPrefab == null)
        {
            Debug.LogWarning("GameManager: ballPrefab is not assigned. Cannot create ball queue.");
            return;
        }

        if (_paddle == null)
        {
            Debug.LogWarning("GameManager: Paddle not found. Tag the paddle as 'Paddle' or ensure PaddleScript exists in scene.");
            return;
        }

        if (_gameCamera == null)
        {
            Debug.LogWarning("GameManager: No camera found for reserve-ball placement.");
            return;
        }

        if (initialBallCount <= 0)
        {
            Debug.LogWarning("GameManager: initialBallCount must be > 0.");
            return;
        }

        Debug.Log($"GameManager: Initializing {initialBallCount} balls. Random effect pool has {(randomEffectPool?.Length ?? 0)} effects.");

        for (int i = 0; i < initialBallCount; i++)
        {
            Vector3 reservePosition;
            if (reserveAnchor != null)
            {
                // Preferred placement: line reserve balls to the right from an explicit scene anchor.
                reservePosition = reserveAnchor.position + Vector3.right * (i * reserveBallSpacing);
            }
            else
            {
                // Fallback placement if no anchor is assigned.
                Vector3 reserveStartWorld = _gameCamera.ViewportToWorldPoint(
                    new Vector3(reserveStartViewport.x, reserveStartViewport.y, Mathf.Abs(_gameCamera.transform.position.z)));
                reservePosition = reserveStartWorld + Vector3.right * (i * reserveBallSpacing);
            }

            reservePosition.z = 0f;

            GameObject ballObject = Instantiate(ballPrefab, reservePosition, Quaternion.identity);
            BallScript ball = ballObject.GetComponent<BallScript>();
            if (ball == null)
            {
                Debug.LogWarning("GameManager: Spawned ballPrefab has no BallScript component.");
                Destroy(ballObject);
                continue;
            }

            ball.SetQueueManaged(true);
            ball.SetPaddleReference(_paddle, ballSpawnOffset);

            BallEffectDefinition effect = GetRandomEffect();
            Debug.Log($"GameManager: Ball {i} assigned effect: {(effect != null ? effect.EffectType.ToString() : "NULL")}");
            ball.SetEffectDefinition(effect);

            ball.ParkAtPosition(reservePosition);
            _reserveBalls.Enqueue(ball);
        }

        MoveNextQueuedBallToPaddle();
    }

    private void ResolveSceneReferences()
    {
        _paddle = GameObject.FindGameObjectWithTag("Paddle")?.transform;
        if (_paddle == null)
        {
            PaddleScript paddleScript = FindFirstObjectByType<PaddleScript>();
            if (paddleScript != null)
                _paddle = paddleScript.transform;
        }

        if (_paddle == null)
        {
            GameObject paddleByName = GameObject.Find("Paddle");
            if (paddleByName != null)
                _paddle = paddleByName.transform;
        }

        _gameCamera = Camera.main;
        if (_gameCamera == null)
            _gameCamera = FindFirstObjectByType<Camera>();
    }

    private void MoveNextQueuedBallToPaddle()
    {
        while (_reserveBalls.Count > 0)
        {
            BallScript nextBall = _reserveBalls.Dequeue();
            if (nextBall == null)
                continue;

            _currentQueueBall = nextBall;
            _currentQueueBall.PrepareOnPaddle();
            return;
        }

        ShowGameOver();
    }

    private BallEffectDefinition GetRandomEffect()
    {
        if (randomEffectPool == null || randomEffectPool.Length == 0)
            return null;

        int idx = Random.Range(0, randomEffectPool.Length);
        BallEffectDefinition baseDefinition = randomEffectPool[idx];

        // Apply active upgrades to the definition
        return UpgradeManager.ApplyUpgrades(baseDefinition, _upgrades);
    }

    private void WinGame()
    {
        _gameWon = true;
        Time.timeScale = 0f;

        if (winScreenPrefab != null)
            Instantiate(winScreenPrefab);
        else
            Debug.Log("YOU WIN! All blocks destroyed!");
    }

    private void ShowGameOver()
    {
        if (_gameOver || _gameWon)
            return;

        _gameOver = true;
        Time.timeScale = 0f;

        if (gameOverScreenPrefab != null)
            Instantiate(gameOverScreenPrefab);
        else
            Debug.Log("GAME OVER! No balls remaining.");
    }

    #region Upgrade API

    /// <summary>Get the current upgrade state (for debugging or UI display).</summary>
    public UpgradeState GetUpgradeState() => _upgrades;

    /// <summary>Increase explosive effect radius.</summary>
    public void UpgradeExplosiveRadius(float radiusBonus)
    {
        _upgrades.ExplosiveRadiusBonus += radiusBonus;
        Debug.Log($"Upgraded Explosive Radius: +{radiusBonus} (Total: +{_upgrades.ExplosiveRadiusBonus})");
    }

    /// <summary>Increase explosive damage multiplier.</summary>
    public void UpgradeExplosiveDamage(float multiplier)
    {
        _upgrades.ExplosiveDamageMultiplier *= multiplier;
        Debug.Log($"Upgraded Explosive Damage: x{multiplier} (Total: x{_upgrades.ExplosiveDamageMultiplier:F2})");
    }

    /// <summary>Increase split angle diversity.</summary>
    public void UpgradeSplitAngle(float angleBonus)
    {
        _upgrades.SplitAngleBonus += angleBonus;
        Debug.Log($"Upgraded Split Angle: +{angleBonus} (Total: +{_upgrades.SplitAngleBonus})");
    }

    /// <summary>Increase split child projectile speed.</summary>
    public void UpgradeSplitSpeed(float multiplier)
    {
        _upgrades.SplitSpeedMultiplier *= multiplier;
        Debug.Log($"Upgraded Split Speed: x{multiplier} (Total: x{_upgrades.SplitSpeedMultiplier:F2})");
    }

    /// <summary>Increase split child projectile damage.</summary>
    public void UpgradeSplitDamage(float multiplier)
    {
        _upgrades.SplitDamageMultiplier *= multiplier;
        Debug.Log($"Upgraded Split Damage: x{multiplier} (Total: x{_upgrades.SplitDamageMultiplier:F2})");
    }

    /// <summary>Increase piercing hits capacity.</summary>
    public void UpgradePiercingHits(int hitBonus)
    {
        _upgrades.PiercingHitsBonus += hitBonus;
        Debug.Log($"Upgraded Piercing Hits: +{hitBonus} (Total: +{_upgrades.PiercingHitsBonus})");
    }

    /// <summary>Increase homing turn rate (aggressiveness).</summary>
    public void UpgradeHomingTurnRate(float multiplier)
    {
        _upgrades.HomingTurnRateMultiplier *= multiplier;
        Debug.Log($"Upgraded Homing Turn Rate: x{multiplier} (Total: x{_upgrades.HomingTurnRateMultiplier:F2})");
    }

    /// <summary>Increase teleport distance per jump.</summary>
    public void UpgradeTeleportDistance(float multiplier)
    {
        _upgrades.TeleportDistanceMultiplier *= multiplier;
        Debug.Log($"Upgraded Teleport Distance: x{multiplier} (Total: x{_upgrades.TeleportDistanceMultiplier:F2})");
    }

    /// <summary>Reset all upgrades to their default values.</summary>
    public void ResetAllUpgrades()
    {
        _upgrades.ResetAll();
        Debug.Log("All upgrades reset to default values.");
    }

    #endregion
}