using System.Collections;
using UnityEngine;

namespace Streamingle.Contents.BossRaid
{
    /// <summary>
    /// 화면 전체 이펙트: 흔들림, 플래시, 히트스톱.
    /// 메인 카메라 기반으로 동작합니다.
    /// </summary>
    public class ScreenEffect : MonoBehaviour
    {
        #region Fields

        [Header("플래시 오버레이")]
        [SerializeField]
        [Tooltip("플래시용 CanvasGroup (ScreenSpace Overlay 하위). 없으면 자동 생성")]
        private CanvasGroup flashOverlay;

        private Coroutine _shakeCoroutine;
        private Coroutine _flashCoroutine;
        private Coroutine _hitStopCoroutine;

        private Camera _mainCamera;
        private Vector3 _cameraOriginalPos;
        private Transform _cameraTransform;

        #endregion

        #region Unity Messages

        private void Start()
        {
            _mainCamera = Camera.main;
            if (_mainCamera != null)
            {
                _cameraTransform = _mainCamera.transform;
                _cameraOriginalPos = _cameraTransform.localPosition;
            }

            EnsureFlashOverlay();
        }

        #endregion

        #region Public Methods

        /// <summary>
        /// 화면 흔들림
        /// </summary>
        public void PlayShake(float intensity, float duration)
        {
            if (_cameraTransform == null) return;

            if (_shakeCoroutine != null)
                StopCoroutine(_shakeCoroutine);
            _shakeCoroutine = StartCoroutine(ShakeCoroutine(intensity, duration));
        }

        /// <summary>
        /// 화면 플래시 (흰색/색상 오버레이)
        /// </summary>
        public void PlayFlash(Color color, float duration)
        {
            if (_flashCoroutine != null)
                StopCoroutine(_flashCoroutine);
            _flashCoroutine = StartCoroutine(FlashCoroutine(color, duration));
        }

        /// <summary>
        /// 히트스톱 (TimeScale 일시 정지)
        /// </summary>
        public void PlayHitStop(float duration)
        {
            if (duration <= 0f) return;

            if (_hitStopCoroutine != null)
                StopCoroutine(_hitStopCoroutine);
            _hitStopCoroutine = StartCoroutine(HitStopCoroutine(duration));
        }

        #endregion

        #region Private Methods

        private void EnsureFlashOverlay()
        {
            if (flashOverlay != null) return;

            var canvasObj = new GameObject("BossRaid_FlashOverlay");
            var canvas = canvasObj.AddComponent<Canvas>();
            canvas.renderMode = RenderMode.ScreenSpaceOverlay;
            canvas.sortingOrder = 999;

            var img = canvasObj.AddComponent<UnityEngine.UI.Image>();
            img.color = new Color(1f, 1f, 1f, 0f);
            img.raycastTarget = false;

            flashOverlay = canvasObj.AddComponent<CanvasGroup>();
            flashOverlay.alpha = 0f;
            flashOverlay.interactable = false;
            flashOverlay.blocksRaycasts = false;

            canvasObj.transform.SetParent(transform);
        }

        private IEnumerator ShakeCoroutine(float intensity, float duration)
        {
            _cameraOriginalPos = _cameraTransform.localPosition;
            float elapsed = 0f;

            while (elapsed < duration)
            {
                elapsed += Time.unscaledDeltaTime;
                float t = 1f - (elapsed / duration);
                float x = Random.Range(-intensity, intensity) * t;
                float y = Random.Range(-intensity, intensity) * t;
                _cameraTransform.localPosition = _cameraOriginalPos + new Vector3(x, y, 0f);
                yield return null;
            }

            _cameraTransform.localPosition = _cameraOriginalPos;
            _shakeCoroutine = null;
        }

        private IEnumerator FlashCoroutine(Color color, float duration)
        {
            if (flashOverlay == null) yield break;

            var img = flashOverlay.GetComponent<UnityEngine.UI.Image>();
            if (img != null) img.color = color;

            // 페이드 인 (빠르게)
            float fadeIn = duration * 0.2f;
            float fadeOut = duration * 0.8f;
            float elapsed = 0f;

            while (elapsed < fadeIn)
            {
                elapsed += Time.unscaledDeltaTime;
                flashOverlay.alpha = Mathf.Lerp(0f, 0.8f, elapsed / fadeIn);
                yield return null;
            }

            // 페이드 아웃
            elapsed = 0f;
            while (elapsed < fadeOut)
            {
                elapsed += Time.unscaledDeltaTime;
                flashOverlay.alpha = Mathf.Lerp(0.8f, 0f, elapsed / fadeOut);
                yield return null;
            }

            flashOverlay.alpha = 0f;
            _flashCoroutine = null;
        }

        private IEnumerator HitStopCoroutine(float duration)
        {
            float prevTimeScale = Time.timeScale;
            Time.timeScale = 0f;

            yield return new WaitForSecondsRealtime(duration);

            Time.timeScale = prevTimeScale;
            _hitStopCoroutine = null;
        }

        #endregion
    }
}