using UnityEngine;
using UnityEngine.UIElements;

namespace Hallucinate.UI
{
    public class PerformanceOverlay : MonoBehaviour
    {
        private static PerformanceOverlay _instance;
        private Label _fpsLabel;
        private UIDocument _uiDocument;
        private VisualElement _root;

        private float _deltaTime = 0f;
        private bool _isVisible = false;

        public static void SetVisible(bool visible)
        {
            if (_instance == null && visible)
            {
                var go = new GameObject("PerformanceOverlay");
                _instance = go.AddComponent<PerformanceOverlay>();
                DontDestroyOnLoad(go);
            }

            if (_instance != null)
            {
                _instance._isVisible = visible;
                if (_instance._root != null)
                {
                    _instance._root.style.display = visible ? DisplayStyle.Flex : DisplayStyle.None;
                }
            }
        }

        private void Awake()
        {
            _uiDocument = gameObject.AddComponent<UIDocument>();
            // Use same panel settings as UIManager if possible, or default
            _uiDocument.panelSettings = Resources.Load<PanelSettings>("UI/PerformancePanelSettings");
            
            _root = new VisualElement();
            _root.style.position = Position.Absolute;
            _root.style.bottom = 10;
            _root.style.left = 10;
            _root.pickingMode = PickingMode.Ignore;

            _fpsLabel = new Label("0 FPS (0.0ms)");
            _fpsLabel.style.color = Color.white;
            _fpsLabel.style.fontSize = 14;
            _fpsLabel.style.unityFontStyleAndWeight = FontStyle.Bold;
            // Shadow effect
            _fpsLabel.style.textShadow = new TextShadow { offset = new Vector2(1, 1), blurRadius = 1, color = Color.black };

            _root.Add(_fpsLabel);
            _uiDocument.rootVisualElement.Add(_root);
            
            _root.style.display = _isVisible ? DisplayStyle.Flex : DisplayStyle.None;
        }

        private void Update()
        {
            if (!_isVisible) return;

            _deltaTime += (Time.unscaledDeltaTime - _deltaTime) * 0.1f;
            float fps = 1.0f / _deltaTime;
            float ms = _deltaTime * 1000.0f;

            _fpsLabel.text = $"{Mathf.Ceil(fps)} FPS ({ms:F1}ms)";
            
            // Color coding based on performance
            if (fps < 30) _fpsLabel.style.color = Color.red;
            else if (fps < 55) _fpsLabel.style.color = Color.yellow;
            else _fpsLabel.style.color = Color.green;
        }
    }
}