using UnityEngine;
using UnityEngine.UI;

namespace Streamingle
{
    /// <summary>
    /// 카메라 블렌딩용 UI 오버레이
    /// RawImage 하나로 이전 카메라 화면을 표시하고 서서히 사라지게 함
    /// </summary>
    public class CameraBlendOverlay : MonoBehaviour
    {
        private static CameraBlendOverlay instance;
        public static CameraBlendOverlay Instance => instance;

        private Canvas canvas;
        private RawImage rawImage;
        private CanvasGroup canvasGroup;

        private void Awake()
        {
            if (instance != null && instance != this)
            {
                Destroy(gameObject);
                return;
            }
            instance = this;
            DontDestroyOnLoad(gameObject);

            SetupUI();
        }

        private void SetupUI()
        {
            // Canvas 설정
            canvas = gameObject.AddComponent<Canvas>();
            canvas.renderMode = RenderMode.ScreenSpaceOverlay;
            canvas.sortingOrder = 9999; // 최상단에 표시

            // CanvasScaler 추가 (화면 크기 맞춤)
            var scaler = gameObject.AddComponent<CanvasScaler>();
            scaler.uiScaleMode = CanvasScaler.ScaleMode.ScaleWithScreenSize;
            scaler.referenceResolution = new Vector2(1920, 1080);
            scaler.screenMatchMode = CanvasScaler.ScreenMatchMode.MatchWidthOrHeight;
            scaler.matchWidthOrHeight = 0.5f;

            // GraphicRaycaster는 추가하지 않음 (클릭 방해 안함)

            // RawImage 생성
            GameObject imageObj = new GameObject("BlendImage");
            imageObj.transform.SetParent(transform, false);

            rawImage = imageObj.AddComponent<RawImage>();
            rawImage.raycastTarget = false; // 레이캐스트 비활성화

            // 화면 전체를 덮도록 설정
            RectTransform rectTransform = rawImage.rectTransform;
            rectTransform.anchorMin = Vector2.zero;
            rectTransform.anchorMax = Vector2.one;
            rectTransform.offsetMin = Vector2.zero;
            rectTransform.offsetMax = Vector2.zero;

            // CanvasGroup 추가 (알파 조절용)
            canvasGroup = imageObj.AddComponent<CanvasGroup>();
            canvasGroup.blocksRaycasts = false;
            canvasGroup.interactable = false;

            // 초기에는 숨김
            Hide();
        }

        /// <summary>
        /// 오버레이 표시 및 텍스처 설정
        /// </summary>
        public void Show(RenderTexture texture)
        {
            if (rawImage == null) return;

            rawImage.texture = texture;
            rawImage.enabled = true;
            canvasGroup.alpha = 1f;
        }

        /// <summary>
        /// 알파값 설정 (0 = 투명, 1 = 불투명)
        /// </summary>
        public void SetAlpha(float alpha)
        {
            if (canvasGroup == null) return;
            canvasGroup.alpha = alpha;
        }

        /// <summary>
        /// 오버레이 숨김
        /// </summary>
        public void Hide()
        {
            if (rawImage == null) return;

            rawImage.enabled = false;
            rawImage.texture = null;
            if (canvasGroup != null)
            {
                canvasGroup.alpha = 0f;
            }
        }

        /// <summary>
        /// 싱글톤 인스턴스 생성 (없으면 자동 생성)
        /// </summary>
        public static CameraBlendOverlay GetOrCreate()
        {
            if (instance != null) return instance;

            GameObject obj = new GameObject("CameraBlendOverlay");
            return obj.AddComponent<CameraBlendOverlay>();
        }

        private void OnDestroy()
        {
            if (instance == this)
            {
                instance = null;
            }
        }
    }
}