using System.Threading;
using Cysharp.Threading.Tasks;
using DanroJump.Gameplay;
using UnityEngine;
using UnityEngine.UIElements;
using Zenject;

namespace DanroJump.UI.Gameplay
{
    /// <summary>
    /// Отображает runtime-показатели игрового забега в UI Toolkit HUD.
    /// </summary>
    public sealed class GameplayHudController : MonoBehaviour
    {
        [SerializeField] private VisualTreeAsset visualTreeAsset;
        [SerializeField] private PanelSettings panelSettings;
        [SerializeField] private int sortingOrder = 10;
        [SerializeField] private string scoreLabelName = "ScoreValue";
        [SerializeField] private string heightLabelName = "HeightValue";
        [SerializeField] private string bestHeightLabelName = "BestHeightValue";
        [SerializeField] private string livesLabelName = "LivesValue";
        [SerializeField] private string coinsLabelName = "CoinsValue";
        [SerializeField] private string deathsLabelName = "DeathsValue";
        [SerializeField] private string stateLabelName = "StateValue";

        private UIDocument document;
        private GameplaySession session;
        private Label scoreLabel;
        private Label heightLabel;
        private Label bestHeightLabel;
        private Label livesLabel;
        private Label coinsLabel;
        private Label deathsLabel;
        private Label stateLabel;
        private CancellationTokenSource refreshCancellation;
        private bool isSubscribedToSession;

        /// <summary>
        /// Получает игровую сессию из DI-контейнера сцены.
        /// </summary>
        [Inject]
        public void Construct(GameplaySession injectedSession)
        {
            SetSession(injectedSession);
        }

        private void Start()
        {
            EnsureDocument();
            BindLabels();
            Refresh();
        }

        /// <summary>
        /// Подписывается на изменения сессии и запускает кадровую подстраховку обновления HUD.
        /// </summary>
        private void OnEnable()
        {
            SubscribeToSession();

            if (refreshCancellation == null)
            {
                refreshCancellation = new CancellationTokenSource();
                RefreshContinuouslyAsync(refreshCancellation.Token).Forget(Debug.LogException);
            }

            Refresh();
        }

        /// <summary>
        /// Останавливает обновление HUD и снимает подписку с игровой сессии.
        /// </summary>
        private void OnDisable()
        {
            if (refreshCancellation != null)
            {
                refreshCancellation.Cancel();
                refreshCancellation.Dispose();
                refreshCancellation = null;
            }

            UnsubscribeFromSession();
        }

        /// <summary>
        /// Создает или настраивает UIDocument, чтобы HUD мог жить на отдельном GameObject без ручной сборки.
        /// </summary>
        private void EnsureDocument()
        {
            if (document == null && !TryGetComponent(out document))
            {
                document = gameObject.AddComponent<UIDocument>();
            }

            if (document == null)
            {
                return;
            }

            document.visualTreeAsset = visualTreeAsset;
            document.panelSettings = panelSettings;
            document.sortingOrder = sortingOrder;
        }

        /// <summary>
        /// Находит текстовые поля в UXML по именам, заданным в инспекторе.
        /// </summary>
        private void BindLabels()
        {
            var root = document != null ? document.rootVisualElement : null;
            if (root == null)
            {
                return;
            }

            scoreLabel = FindLabel(root, scoreLabelName);
            heightLabel = FindLabel(root, heightLabelName);
            bestHeightLabel = FindLabel(root, bestHeightLabelName);
            livesLabel = FindLabel(root, livesLabelName);
            coinsLabel = FindLabel(root, coinsLabelName);
            deathsLabel = FindLabel(root, deathsLabelName);
            stateLabel = FindLabel(root, stateLabelName);
        }

        /// <summary>
        /// Обновляет все значения HUD из текущей игровой сессии.
        /// </summary>
        private void Refresh()
        {
            if (session == null)
            {
                SetLabel(stateLabel, "WAITING");
                return;
            }

            SetLabel(scoreLabel, session.Score.ToString());
            SetLabel(heightLabel, $"{session.MaxRunHeight:0} м");
            SetLabel(bestHeightLabel, $"{session.RecordHeight:0} м");
            SetLabel(livesLabel, session.RemainingLives.ToString());
            SetLabel(coinsLabel, session.Coins.ToString());
            SetLabel(deathsLabel, session.DeathCount.ToString());
            SetLabel(stateLabel, FormatState(session.State));
        }

        /// <summary>
        /// Безопасно обновляет текст label, если элемент найден в UXML.
        /// </summary>
        private static void SetLabel(Label label, string value)
        {
            if (label != null)
            {
                label.text = value;
            }
        }

        /// <summary>
        /// Ищет Label по имени, заданному в настройках контроллера.
        /// </summary>
        private static Label FindLabel(VisualElement root, string labelName)
        {
            return root != null && !string.IsNullOrEmpty(labelName)
                ? root.Q<Label>(labelName)
                : null;
        }

        /// <summary>
        /// Подстраховывает HUD от событий, которые могли прийти до подписки.
        /// </summary>
        private async UniTask RefreshContinuouslyAsync(CancellationToken cancellationToken)
        {
            try
            {
                while (enabled && !cancellationToken.IsCancellationRequested)
                {
                    Refresh();
                    await UniTask.Yield(PlayerLoopTiming.Update, cancellationToken);
                }
            }
            catch (System.OperationCanceledException)
            {
            }
        }

        /// <summary>
        /// Преобразует состояние сессии в короткий текст для HUD.
        /// </summary>
        private static string FormatState(GameplaySessionState state)
        {
            return state switch
            {
                GameplaySessionState.Running => "RUN",
                GameplaySessionState.Respawning => "RESPAWN",
                GameplaySessionState.GameOver => "GAME OVER",
                _ => "WAITING",
            };
        }

        private void SetSession(GameplaySession injectedSession)
        {
            if (session == injectedSession)
            {
                return;
            }

            UnsubscribeFromSession();
            session = injectedSession;
            SubscribeToSession();
            Refresh();
        }

        private void SubscribeToSession()
        {
            if (!isActiveAndEnabled || session == null || isSubscribedToSession)
            {
                return;
            }

            session.Changed += Refresh;
            isSubscribedToSession = true;
        }

        private void UnsubscribeFromSession()
        {
            if (session == null || !isSubscribedToSession)
            {
                return;
            }

            session.Changed -= Refresh;
            isSubscribedToSession = false;
        }
    }
}