using System.Collections.Generic;
using GameFramework.Event;
using UnityEngine;
using UnityEngine.UI;
using UnityGameFramework.Runtime;

namespace GeometryTD.CustomComponent
{
    /// <summary>
    /// Keeps gameplay camera and UI in a fixed design aspect, then fills extra area with black masks.
    /// </summary>
    public class ResolutionAdapterComponent : GameFrameworkComponent
    {
        private const float DefaultCanvasPlaneDistance = 100f;

        [SerializeField] private Vector2 _referenceResolution = new Vector2(2560f, 1600f);
        [SerializeField] private bool _adaptUiCanvasToViewport = true;
        [SerializeField] private bool _enableBlackMask = true;
        [SerializeField] private List<Transform> _uiRoots = new List<Transform>();

        private readonly List<Canvas> _canvasBuffer = new List<Canvas>(32);
        private readonly List<Canvas> _trackedCanvases = new List<Canvas>(32);
        private readonly HashSet<Canvas> _trackedCanvasSet = new HashSet<Canvas>();

        private Camera _mainCamera;
        private Rect _targetViewport = new Rect(0f, 0f, 1f, 1f);
        private int _cachedScreenWidth = -1;
        private int _cachedScreenHeight = -1;

        private bool _canvasCacheDirty = true;
        private bool _uiEventSubscribed;
        private bool _missingRootWarned;

        private Canvas _maskCanvas;
        private RectTransform _leftMask;
        private RectTransform _rightMask;
        private RectTransform _topMask;
        private RectTransform _bottomMask;

        private void Start()
        {
            TryEnsureUiEventSubscribed();
            ApplyAdaptation(true);
        }

        private void Update()
        {
            TryEnsureUiEventSubscribed();
            ApplyAdaptation(false);
        }

        private void OnDestroy()
        {
            UnsubscribeUiEvents();

            if (_mainCamera != null)
            {
                _mainCamera.rect = new Rect(0f, 0f, 1f, 1f);
            }
        }

        private void ApplyAdaptation(bool force)
        {
            if (_referenceResolution.x <= 0f || _referenceResolution.y <= 0f)
            {
                return;
            }

            Camera resolvedCamera = ResolveMainCamera();
            bool cameraChanged = resolvedCamera != _mainCamera;
            bool screenChanged = Screen.width != _cachedScreenWidth || Screen.height != _cachedScreenHeight;
            bool needRecalculate = force || cameraChanged || screenChanged;

            if (needRecalculate)
            {
                Camera lastCamera = _mainCamera;
                if (lastCamera != null && lastCamera != resolvedCamera)
                {
                    lastCamera.rect = new Rect(0f, 0f, 1f, 1f);
                }

                _mainCamera = resolvedCamera;
                _cachedScreenWidth = Screen.width;
                _cachedScreenHeight = Screen.height;
                _targetViewport = CalculateViewport(_cachedScreenWidth, _cachedScreenHeight);

                ApplyCameraViewport();
                UpdateMaskLayout();
            }

            if (!_adaptUiCanvasToViewport)
            {
                return;
            }

            if (!needRecalculate && !_canvasCacheDirty)
            {
                return;
            }

            ApplyCanvasAdaptation();
        }

        private Camera ResolveMainCamera()
        {
            if (GameEntry.Scene != null && GameEntry.Scene.MainCamera != null)
            {
                return GameEntry.Scene.MainCamera;
            }

            if (Camera.main != null)
            {
                return Camera.main;
            }

            if (_mainCamera != null && _mainCamera.isActiveAndEnabled)
            {
                return _mainCamera;
            }

            return null;
        }

        private Rect CalculateViewport(int width, int height)
        {
            if (width <= 0 || height <= 0)
            {
                return new Rect(0f, 0f, 1f, 1f);
            }

            float referenceAspect = _referenceResolution.x / _referenceResolution.y;
            float screenAspect = (float)width / height;

            if (Mathf.Approximately(referenceAspect, screenAspect))
            {
                return new Rect(0f, 0f, 1f, 1f);
            }

            if (screenAspect > referenceAspect)
            {
                float viewportWidth = referenceAspect / screenAspect;
                return new Rect((1f - viewportWidth) * 0.5f, 0f, viewportWidth, 1f);
            }

            float viewportHeight = screenAspect / referenceAspect;
            return new Rect(0f, (1f - viewportHeight) * 0.5f, 1f, viewportHeight);
        }

        private void ApplyCameraViewport()
        {
            if (_mainCamera == null)
            {
                return;
            }

            _mainCamera.rect = _targetViewport;
        }

        private void ApplyCanvasAdaptation()
        {
            if (_mainCamera == null)
            {
                return;
            }

            if (_uiRoots == null || _uiRoots.Count == 0)
            {
                if (!_missingRootWarned)
                {
                    _missingRootWarned = true;
                    Log.Warning(
                        "ResolutionAdapterComponent missing injected roots. Assign UI/HPBar root transforms in scene.");
                }

                return;
            }

            if (_canvasCacheDirty)
            {
                RebuildCanvasCache();
            }

            for (int i = _trackedCanvases.Count - 1; i >= 0; i--)
            {
                Canvas canvas = _trackedCanvases[i];
                if (canvas == null)
                {
                    _trackedCanvases.RemoveAt(i);
                    _canvasCacheDirty = true;
                    continue;
                }

                ApplyCanvasSettings(canvas);
            }
        }

        private void RebuildCanvasCache()
        {
            _canvasCacheDirty = false;
            _trackedCanvases.Clear();
            _trackedCanvasSet.Clear();

            foreach (var root in _uiRoots)
            {
                CollectCanvases(root);
            }
        }

        private void CollectCanvases(Transform root)
        {
            if (root == null)
            {
                return;
            }

            root.GetComponentsInChildren(true, _canvasBuffer);
            foreach (Canvas canvas in _canvasBuffer)
            {
                if (canvas == null || canvas == _maskCanvas || canvas.renderMode == RenderMode.WorldSpace)
                {
                    continue;
                }

                if (_trackedCanvasSet.Add(canvas))
                {
                    _trackedCanvases.Add(canvas);
                }
            }

            _canvasBuffer.Clear();
        }

        private void ApplyCanvasSettings(Canvas canvas)
        {
            if (canvas == _maskCanvas || canvas.renderMode == RenderMode.WorldSpace)
            {
                return;
            }

            canvas.renderMode = RenderMode.ScreenSpaceCamera;
            canvas.worldCamera = _mainCamera;
            canvas.planeDistance = ResolveCanvasPlaneDistance(_mainCamera);

            CanvasScaler scaler = canvas.GetComponent<CanvasScaler>();
            if (scaler != null)
            {
                scaler.uiScaleMode = CanvasScaler.ScaleMode.ScaleWithScreenSize;
                scaler.referenceResolution = _referenceResolution;
                scaler.screenMatchMode = CanvasScaler.ScreenMatchMode.MatchWidthOrHeight;
                scaler.matchWidthOrHeight = 0f;
            }
        }

        private static float ResolveCanvasPlaneDistance(Camera camera)
        {
            if (camera == null)
            {
                return DefaultCanvasPlaneDistance;
            }

            float minDistance = camera.nearClipPlane + 0.05f;
            float maxDistance = camera.farClipPlane - 0.05f;
            if (maxDistance <= minDistance)
            {
                return minDistance;
            }

            return Mathf.Clamp(DefaultCanvasPlaneDistance, minDistance, maxDistance);
        }

        private void TryEnsureUiEventSubscribed()
        {
            if (_uiEventSubscribed || GameEntry.Event == null)
            {
                return;
            }

            GameEntry.Event.Subscribe(OpenUIFormSuccessEventArgs.EventId, OnUIFormChanged);
            GameEntry.Event.Subscribe(CloseUIFormCompleteEventArgs.EventId, OnUIFormChanged);
            _uiEventSubscribed = true;
            _canvasCacheDirty = true;
        }

        private void UnsubscribeUiEvents()
        {
            if (!_uiEventSubscribed || GameEntry.Event == null)
            {
                return;
            }

            GameEntry.Event.Unsubscribe(OpenUIFormSuccessEventArgs.EventId, OnUIFormChanged);
            GameEntry.Event.Unsubscribe(CloseUIFormCompleteEventArgs.EventId, OnUIFormChanged);
            _uiEventSubscribed = false;
        }

        private void OnUIFormChanged(object sender, GameEventArgs e)
        {
            _canvasCacheDirty = true;
        }

        private void UpdateMaskLayout()
        {
            if (!_enableBlackMask)
            {
                SetMaskVisible(false, false);
                return;
            }

            EnsureMaskObjects();
            if (_maskCanvas == null)
            {
                return;
            }

            float horizontalPadding = Mathf.Max(0f, (1f - _targetViewport.width) * 0.5f * _cachedScreenWidth);
            float verticalPadding = Mathf.Max(0f, (1f - _targetViewport.height) * 0.5f * _cachedScreenHeight);

            bool showVerticalMask = horizontalPadding > 0.5f;
            bool showHorizontalMask = verticalPadding > 0.5f;

            SetMaskVisible(showVerticalMask, showHorizontalMask);
            if (showVerticalMask)
            {
                SetVerticalMaskRect(_leftMask, true, horizontalPadding);
                SetVerticalMaskRect(_rightMask, false, horizontalPadding);
            }

            if (showHorizontalMask)
            {
                SetHorizontalMaskRect(_topMask, true, verticalPadding);
                SetHorizontalMaskRect(_bottomMask, false, verticalPadding);
            }
        }

        private void EnsureMaskObjects()
        {
            if (_maskCanvas != null)
            {
                return;
            }

            GameObject maskRoot = new GameObject(
                "ResolutionMask",
                typeof(RectTransform),
                typeof(Canvas),
                typeof(CanvasScaler),
                typeof(GraphicRaycaster));
            maskRoot.transform.SetParent(transform, false);

            _maskCanvas = maskRoot.GetComponent<Canvas>();
            _maskCanvas.renderMode = RenderMode.ScreenSpaceOverlay;
            _maskCanvas.overrideSorting = true;
            _maskCanvas.sortingOrder = short.MaxValue;

            CanvasScaler scaler = maskRoot.GetComponent<CanvasScaler>();
            scaler.uiScaleMode = CanvasScaler.ScaleMode.ConstantPixelSize;
            scaler.scaleFactor = 1f;

            GraphicRaycaster raycaster = maskRoot.GetComponent<GraphicRaycaster>();
            raycaster.enabled = false;

            RectTransform rootRect = maskRoot.GetComponent<RectTransform>();
            rootRect.anchorMin = Vector2.zero;
            rootRect.anchorMax = Vector2.one;
            rootRect.anchoredPosition = Vector2.zero;
            rootRect.sizeDelta = Vector2.zero;

            _leftMask = CreateMaskRect("LeftMask", rootRect);
            _rightMask = CreateMaskRect("RightMask", rootRect);
            _topMask = CreateMaskRect("TopMask", rootRect);
            _bottomMask = CreateMaskRect("BottomMask", rootRect);
        }

        private static RectTransform CreateMaskRect(string maskName, Transform parent)
        {
            GameObject maskObject = new GameObject(maskName, typeof(RectTransform), typeof(Image));
            maskObject.transform.SetParent(parent, false);

            Image image = maskObject.GetComponent<Image>();
            image.color = Color.black;
            image.raycastTarget = false;

            return maskObject.GetComponent<RectTransform>();
        }

        private void SetMaskVisible(bool showVerticalMask, bool showHorizontalMask)
        {
            if (_maskCanvas == null)
            {
                return;
            }

            bool visible = showVerticalMask || showHorizontalMask;
            _maskCanvas.enabled = visible;

            if (_leftMask != null)
            {
                _leftMask.gameObject.SetActive(showVerticalMask);
            }

            if (_rightMask != null)
            {
                _rightMask.gameObject.SetActive(showVerticalMask);
            }

            if (_topMask != null)
            {
                _topMask.gameObject.SetActive(showHorizontalMask);
            }

            if (_bottomMask != null)
            {
                _bottomMask.gameObject.SetActive(showHorizontalMask);
            }
        }

        private static void SetVerticalMaskRect(RectTransform maskRect, bool isLeft, float width)
        {
            if (maskRect == null)
            {
                return;
            }

            maskRect.anchorMin = new Vector2(isLeft ? 0f : 1f, 0f);
            maskRect.anchorMax = new Vector2(isLeft ? 0f : 1f, 1f);
            maskRect.pivot = new Vector2(isLeft ? 0f : 1f, 0.5f);
            maskRect.anchoredPosition = Vector2.zero;
            maskRect.sizeDelta = new Vector2(width, 0f);
        }

        private static void SetHorizontalMaskRect(RectTransform maskRect, bool isTop, float height)
        {
            if (maskRect == null)
            {
                return;
            }

            maskRect.anchorMin = new Vector2(0f, isTop ? 1f : 0f);
            maskRect.anchorMax = new Vector2(1f, isTop ? 1f : 0f);
            maskRect.pivot = new Vector2(0.5f, isTop ? 1f : 0f);
            maskRect.anchoredPosition = Vector2.zero;
            maskRect.sizeDelta = new Vector2(0f, height);
        }
    }
}