using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UIElements;
using System.Linq;

namespace UI
{
    public class UIManager : MonoBehaviour
    {
        public static UIManager Instance { get; private set; }

        [System.Serializable]
        public class ScreenData
        {
            public string screenName;
            public UIDocument document;
            public bool isOverlay;
            public bool isActive;
        }

        public List<ScreenData> screens = new List<ScreenData>();
        public string initialScreen = "MainMenu";
        
        [Header("Cursor Settings")]
        private VisualElement _customCursor;
        private List<VisualElement> _trailPool = new List<VisualElement>();
        private int _trailIndex = 0;
        public int trailCount = 15;
        public float focusRadius = 500f;

        [Header("Editor Preview")]
        [Range(0f, 1f)]
        public float globalOpacity = 1f;

        private Stack<string> _navigationStack = new Stack<string>();
        private string _currentScreenName;
        private VisualElement _lastHoveredElement;
        
        // Flags for MainMenu state
        public bool isMainMenuActive = false; 
        private bool _isSettingsOpen = false;

        private void Awake()
        {
            if (Instance == null) Instance = this;
            else { Destroy(gameObject); return; }

            SetupCursor();
            foreach (var s in screens) 
            {
                if (s.document != null) s.document.rootVisualElement.style.display = DisplayStyle.None;
            }
            ShowScreen(initialScreen);
        }

        private void SetupCursor()
        {
            UIDocument doc = GetComponent<UIDocument>();
            if (doc == null && screens.Count > 0) doc = screens[0].document;
            if (doc == null) return;
            
            var root = doc.rootVisualElement;

            _customCursor = new VisualElement();
            _customCursor.style.width = 25; _customCursor.style.height = 25;
            _customCursor.style.backgroundColor = Color.white;
            _customCursor.style.borderTopLeftRadius = 13; _customCursor.style.borderTopRightRadius = 13;
            _customCursor.style.borderBottomLeftRadius = 13; _customCursor.style.borderBottomRightRadius = 13;
            _customCursor.style.position = Position.Absolute;
            _customCursor.pickingMode = PickingMode.Ignore;
            root.Add(_customCursor);

            for (int i = 0; i < trailCount; i++)
            {
                var trail = new VisualElement();
                trail.style.width = 18; trail.style.height = 18;
                trail.style.backgroundColor = new Color(1, 1, 1, 0.4f);
                trail.style.borderTopLeftRadius = 9; trail.style.borderTopRightRadius = 9;
                trail.style.borderBottomLeftRadius = 9; trail.style.borderBottomRightRadius = 9;
                trail.style.position = Position.Absolute;
                trail.pickingMode = PickingMode.Ignore;
                root.Add(trail);
                _trailPool.Add(trail);
            }
            _customCursor.BringToFront();
        }

        private void Update()
        {
            Vector2 mousePos = Input.mousePosition;
            
            bool isMainMenu = (_currentScreenName == "MainMenu");
            bool restrictY = (isMainMenu && isMainMenuActive && !_isSettingsOpen);
            
            float targetY = restrictY ? Screen.height / 2f : mousePos.y;
            Vector2 uiPos = new Vector2(mousePos.x, Screen.height - targetY);

            bool showCursor = !isMainMenu || !isMainMenuActive || _isSettingsOpen;
            DisplayStyle cursorDisplay = showCursor ? DisplayStyle.Flex : DisplayStyle.None;

            if (_customCursor != null)
            {
                _customCursor.style.display = cursorDisplay;
                _customCursor.style.left = uiPos.x - 12.5f;
                _customCursor.style.top = uiPos.y - 12.5f;
            }

            if (_trailPool.Count > 0)
            {
                var currentTrail = _trailPool[_trailIndex];
                currentTrail.style.left = uiPos.x - 9;
                currentTrail.style.top = uiPos.y - 9;
                currentTrail.style.opacity = 0.5f;
                foreach(var t in _trailPool) 
                {
                    t.style.display = cursorDisplay;
                    t.style.opacity = Mathf.Max(0, t.style.opacity.value - Time.deltaTime * 4f);
                }
                _trailIndex = (_trailIndex + 1) % _trailPool.Count;
            }

            HandleVirtualInput(uiPos);

            if ((Input.GetKey(KeyCode.LeftControl) || Input.GetKey(KeyCode.RightControl)) && Input.GetKeyDown(KeyCode.O))
                ToggleSettings();
        }

        private void HandleVirtualInput(Vector2 uiPos)
        {
            UIDocument activeDoc = null;
            var settings = screens.Find(s => s.screenName == "Settings");
            if (_isSettingsOpen) activeDoc = settings.document;
            else activeDoc = screens.Find(s => s.screenName == _currentScreenName)?.document;

            if (activeDoc == null) return;

            VisualElement bestElement = null;
            float minDistance = float.MaxValue;

            var interactables = activeDoc.rootVisualElement.Query<VisualElement>()
                .Where(e => e.focusable && e.pickingMode != PickingMode.Ignore).ToList();

            foreach (var element in interactables)
            {
                Rect worldBounds = element.worldBound;
                float dist = Vector2.Distance(uiPos, worldBounds.center);
                if (dist < minDistance && dist < focusRadius) {
                    minDistance = dist;
                    bestElement = element;
                }
            }

            if (bestElement != _lastHoveredElement)
            {
                _lastHoveredElement?.RemoveFromClassList("hover");
                bestElement?.AddToClassList("hover");
                _lastHoveredElement = bestElement;
            }

            if (Input.GetMouseButtonDown(0) && _lastHoveredElement != null)
            {
                using (var clickEvent = ClickEvent.GetPooled()) {
                    clickEvent.target = _lastHoveredElement;
                    _lastHoveredElement.SendEvent(clickEvent);
                }
            }
        }

        // --- Editor Support Methods (Restored) ---

        public void SyncScreens()
        {
            foreach (var screen in screens)
            {
                if (screen.document != null && screen.document.rootVisualElement != null)
                {
                    screen.document.rootVisualElement.style.display = 
                        screen.isActive ? DisplayStyle.Flex : DisplayStyle.None;
                    screen.document.rootVisualElement.style.opacity = globalOpacity;
                }
            }
        }

        public void ShowOnly(string name)
        {
            foreach (var screen in screens)
            {
                screen.isActive = (screen.screenName == name);
            }
            SyncScreens();
        }

        // --- Runtime Logic ---

        public void ShowScreen(string name)
        {
            var screen = screens.Find(s => s.screenName == name);
            if (screen == null) return;

            if (!screen.isOverlay)
            {
                foreach(var s in screens) if(!s.isOverlay && s.document != null) s.document.rootVisualElement.style.display = DisplayStyle.None;
                _navigationStack.Push(name);
                _currentScreenName = name;
            }

            screen.document.rootVisualElement.style.display = DisplayStyle.Flex;
            screen.isActive = true;
            UnityEngine.Cursor.visible = false;
        }

        public void GoBack()
        {
            if (_navigationStack.Count <= 1) return;
            string current = _navigationStack.Pop();
            var currentData = screens.Find(s => s.screenName == current);
            if (currentData != null) currentData.document.rootVisualElement.style.display = DisplayStyle.None;

            _currentScreenName = _navigationStack.Peek();
            var prevData = screens.Find(s => s.screenName == _currentScreenName);
            if (prevData != null) 
            {
                prevData.document.rootVisualElement.style.display = DisplayStyle.Flex;
                prevData.isActive = true;
            }
        }

        public void ToggleSettings()
        {
            var settings = screens.Find(s => s.screenName == "Settings");
            if (settings == null) return;
            _isSettingsOpen = settings.document.rootVisualElement.style.display == DisplayStyle.None;
            settings.document.rootVisualElement.style.display = _isSettingsOpen ? DisplayStyle.Flex : DisplayStyle.None;
            settings.isActive = _isSettingsOpen;
            
            if (_isSettingsOpen) settings.document.sortingOrder = 999;
        }
    }
}