using UnityEngine;
using UnityEngine.UI;
using IndianOceanAssets.Engine2_5D;

namespace GameFramework
{
    /// <summary>
    /// 受击泛红特效 —— 玩家受伤时屏幕四周闪烁红色暗角。
    /// 
    /// 挂载到场景中任意物体上（或由 GameHUD 自动创建）。
    /// 运行时自动创建全屏暗角遮罩，监听 HealthSystem.onPlayerDamaged 事件。
    /// </summary>
    public class DamageFlashOverlay : MonoBehaviour
    {
        [Header("特效参数")]
        [Tooltip("受击时暗角最大透明度（0~1）")]
        [SerializeField] private float flashAlpha = 0.8f;

        [Tooltip("闪烁淡出时间（秒）")]
        [SerializeField] private float fadeDuration = 0.4f;

        [Tooltip("暗角内圈半径（0~1，0=全屏幕红色，1=只有最边缘）")]
        [SerializeField] private float innerRadius = 0.8f;

        private Canvas _canvas;
        private Image _overlayImage;
        private float _currentAlpha;
        private bool _isFlashing;

        private void Start()
        {
            CreateOverlay();
            HealthSystem.onPlayerDamaged += OnPlayerDamaged;
        }

        private void OnDestroy()
        {
            HealthSystem.onPlayerDamaged -= OnPlayerDamaged;
        }

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

            // 淡出
            _currentAlpha -= Time.unscaledDeltaTime / fadeDuration;
            if (_currentAlpha <= 0f)
            {
                _currentAlpha = 0f;
                _isFlashing = false;
                _overlayImage.gameObject.SetActive(false);
            }

            _overlayImage.color = new Color(1f, 0f, 0f, _currentAlpha);
        }

        private void OnPlayerDamaged()
        {
            // 重置闪烁
            _currentAlpha = flashAlpha;
            _isFlashing = true;
            _overlayImage.gameObject.SetActive(true);
            _overlayImage.color = new Color(1f, 0f, 0f, _currentAlpha);
        }

        /// <summary>
        /// 创建全屏暗角遮罩（运行时生成暗角纹理）。
        /// </summary>
        private void CreateOverlay()
        {
            // 创建 Canvas
            var canvasObj = new GameObject("DamageFlashCanvas");
            _canvas = canvasObj.AddComponent<Canvas>();
            _canvas.renderMode = RenderMode.ScreenSpaceOverlay;
            _canvas.sortingOrder = 10000; // 在 HUD 之上
            canvasObj.AddComponent<CanvasScaler>();

            // 创建全屏 Image
            var imageObj = new GameObject("DamageFlashImage");
            imageObj.transform.SetParent(canvasObj.transform, false);
            var rect = imageObj.AddComponent<RectTransform>();
            rect.anchorMin = Vector2.zero;
            rect.anchorMax = Vector2.one;
            rect.sizeDelta = Vector2.zero;

            _overlayImage = imageObj.AddComponent<Image>();
            _overlayImage.sprite = CreateVignetteSprite();
            _overlayImage.type = Image.Type.Simple;
            _overlayImage.raycastTarget = false; // 不阻挡点击
            imageObj.SetActive(false); // 初始隐藏
        }

        /// <summary>
        /// 运行时生成暗角纹理（中心透明，边缘红色）。
        /// </summary>
        private Sprite CreateVignetteSprite()
        {
            int size = 256;
            var texture = new Texture2D(size, size, TextureFormat.RGBA32, false);
            var pixels = new Color[size * size];

            float center = size * 0.5f;
            float maxDist = center; // 最大距离（角到中心）

            for (int y = 0; y < size; y++)
            {
                for (int x = 0; x < size; x++)
                {
                    // 计算到中心的归一化距离
                    float dx = (x - center) / center;
                    float dy = (y - center) / center;
                    float dist = Mathf.Sqrt(dx * dx + dy * dy);

                    // 暗角效果：内圈透明，外圈不透明
                    float alpha;
                    if (dist <= innerRadius)
                    {
                        alpha = 0f;
                    }
                    else
                    {
                        // 从内圈到边缘平滑过渡
                        float t = (dist - innerRadius) / (1.414f - innerRadius); // 1.414 = sqrt(2)
                        alpha = Mathf.SmoothStep(0f, 1f, t);
                    }

                    pixels[y * size + x] = new Color(1f, 0f, 0f, alpha);
                }
            }

            texture.SetPixels(pixels);
            texture.Apply();
            texture.filterMode = FilterMode.Bilinear;

            return Sprite.Create(texture, new Rect(0, 0, size, size), Vector2.one * 0.5f);
        }
    }
}