using System.Collections;
using DG.Tweening;
using UnityEngine;
using UnityEngine.UI;

namespace AibisDream.UI
{
    /// <summary>
    /// 全局屏幕转场面板。In 决定遮罩颜色和盖入方式，Out 决定揭出方式。
    /// </summary>
    public class ScreenTransitionPanel : MonoBehaviour, IUIPanel
    {
        private enum TransitionVisual
        {
            None,
            Overlay,
            Shutter
        }

        private const float DefaultWipeDuration = 0.6f;
        private const float DefaultShutterDuration = 0.6f;

        [SerializeField] private GameObject transitionVisualRoot;
        [SerializeField] private Image overlayImage;
        [SerializeField] private RectTransform shutterRoot;
        [SerializeField] private Image shutterTop;
        [SerializeField] private Image shutterBottom;

        private Color _coverColor = Color.black;
        private TransitionVisual _currentVisual = TransitionVisual.None;
        private bool _isCovered;
        private int _transitionVersion;

        public bool IsOpen => gameObject.activeSelf;
        public bool IsCloseable => false;

        private RectTransform OverlayRect => overlayImage.rectTransform;

        private void Awake()
        {
            ResetVisualsImmediate();
        }

        private void OnDisable()
        {
            CancelActiveTransition();
        }

        public IEnumerator FadeInAsync(float duration = 1f, bool useUnscaledTime = false)
        {
            return FadeInInternal(Color.black, duration, useUnscaledTime);
        }

        public IEnumerator FadeInWhiteAsync(float duration = 1f, bool useUnscaledTime = false)
        {
            return FadeInInternal(Color.white, duration, useUnscaledTime);
        }

        public IEnumerator FadeOutAsync(float duration = 1f, bool useUnscaledTime = false)
        {
            var version = BeginTransition();
            PrepareOverlayForFadeOut();

            duration = Mathf.Max(0f, duration);
            if (duration <= 0f)
            {
                if (version == _transitionVersion)
                {
                    ResetVisualsImmediate();
                }

                yield break;
            }

            var tween = overlayImage.DOFade(0f, duration)
                .SetUpdate(useUnscaledTime)
                .SetTarget(this);
            yield return tween.WaitForCompletion();

            if (version == _transitionVersion)
            {
                ResetVisualsImmediate();
            }
        }

        public void FadeInSync(float duration = 1f)
        {
            StartCoroutine(FadeInAsync(duration));
        }

        public void FadeOutSync(float duration = 1f)
        {
            StartCoroutine(FadeOutAsync(duration));
        }

        public IEnumerator FlashWhite(float duration = 0.2f, bool useUnscaledTime = false)
        {
            var version = BeginTransition();
            PrepareVisibleOverlay(Color.white, 0f);
            _isCovered = false;

            duration = Mathf.Max(0f, duration);
            if (duration <= 0f)
            {
                if (version == _transitionVersion)
                {
                    ResetVisualsImmediate();
                }

                yield break;
            }

            var halfDuration = duration * 0.5f;
            var sequence = DOTween.Sequence()
                .Append(overlayImage.DOFade(1f, halfDuration))
                .Append(overlayImage.DOFade(0f, halfDuration))
                .SetUpdate(useUnscaledTime)
                .SetTarget(this);
            yield return sequence.WaitForCompletion();

            if (version == _transitionVersion)
            {
                ResetVisualsImmediate();
            }
        }

        public IEnumerator WipeInAsync(float duration = DefaultWipeDuration, bool useUnscaledTime = false)
        {
            var version = BeginTransition();
            PrepareVisibleOverlay(Color.black, 1f);
            _isCovered = false;

            var width = GetTransitionWidth();
            OverlayRect.anchoredPosition = new Vector2(-width, 0f);
            duration = Mathf.Max(0f, duration);
            if (duration <= 0f)
            {
                OverlayRect.anchoredPosition = Vector2.zero;
                CompleteCover(version);
                yield break;
            }

            var tween = OverlayRect.DOAnchorPosX(0f, duration)
                .SetEase(Ease.InOutQuad)
                .SetUpdate(useUnscaledTime)
                .SetTarget(this);
            yield return tween.WaitForCompletion();
            CompleteCover(version);
        }

        public IEnumerator WipeOutAsync(float duration = DefaultWipeDuration, bool useUnscaledTime = false)
        {
            var version = BeginTransition();
            PrepareOverlayCovered();

            var width = GetTransitionWidth();
            duration = Mathf.Max(0f, duration);
            if (duration <= 0f)
            {
                OverlayRect.anchoredPosition = new Vector2(width, 0f);
                if (version == _transitionVersion)
                {
                    ResetVisualsImmediate();
                }

                yield break;
            }

            var tween = OverlayRect.DOAnchorPosX(width, duration)
                .SetEase(Ease.InOutQuad)
                .SetUpdate(useUnscaledTime)
                .SetTarget(this);
            yield return tween.WaitForCompletion();

            if (version == _transitionVersion)
            {
                ResetVisualsImmediate();
            }
        }

        public IEnumerator ShutterInAsync(float duration = DefaultShutterDuration, bool useUnscaledTime = false)
        {
            var version = BeginTransition();
            _coverColor = Color.black;
            PrepareShutter(_coverColor, 0f);
            _isCovered = false;

            duration = Mathf.Max(0f, duration);
            if (duration <= 0f)
            {
                SetShutterScale(1f);
                CompleteCover(version);
                yield break;
            }

            var sequence = DOTween.Sequence()
                .Join(shutterTop.rectTransform.DOScaleY(1f, duration))
                .Join(shutterBottom.rectTransform.DOScaleY(1f, duration))
                .SetEase(Ease.InOutQuad)
                .SetUpdate(useUnscaledTime)
                .SetTarget(this);
            yield return sequence.WaitForCompletion();
            CompleteCover(version);
        }

        public IEnumerator ShutterOutAsync(float duration = DefaultShutterDuration, bool useUnscaledTime = false)
        {
            var version = BeginTransition();
            if (!transitionVisualRoot.activeSelf)
            {
                _coverColor = Color.black;
            }

            PrepareShutter(_coverColor, 1f);
            duration = Mathf.Max(0f, duration);
            if (duration <= 0f)
            {
                SetShutterScale(0f);
                if (version == _transitionVersion)
                {
                    ResetVisualsImmediate();
                }

                yield break;
            }

            var sequence = DOTween.Sequence()
                .Join(shutterTop.rectTransform.DOScaleY(0f, duration))
                .Join(shutterBottom.rectTransform.DOScaleY(0f, duration))
                .SetEase(Ease.InOutQuad)
                .SetUpdate(useUnscaledTime)
                .SetTarget(this);
            yield return sequence.WaitForCompletion();

            if (version == _transitionVersion)
            {
                ResetVisualsImmediate();
            }
        }

        public bool CaptureScreenCovered()
        {
            return _isCovered;
        }

        public void ApplyScreenCovered(bool isCovered)
        {
            BeginTransition();
            if (!isCovered)
            {
                ResetVisualsImmediate();
                return;
            }

            PrepareVisibleOverlay(Color.black, 1f);
            _isCovered = true;
        }

        public void Show()
        {
            gameObject.SetActive(true);
        }

        public void Hide()
        {
            BeginTransition();
            ResetVisualsImmediate();
            gameObject.SetActive(false);
        }

        private IEnumerator FadeInInternal(Color color, float duration, bool useUnscaledTime)
        {
            var version = BeginTransition();
            var startAlpha = transitionVisualRoot.activeSelf && _currentVisual == TransitionVisual.Overlay
                ? overlayImage.color.a
                : 0f;
            PrepareVisibleOverlay(color, startAlpha);
            _isCovered = false;

            duration = Mathf.Max(0f, duration);
            if (duration <= 0f)
            {
                SetImageAlpha(overlayImage, 1f);
                CompleteCover(version);
                yield break;
            }

            var tween = overlayImage.DOFade(1f, duration)
                .SetUpdate(useUnscaledTime)
                .SetTarget(this);
            yield return tween.WaitForCompletion();
            CompleteCover(version);
        }

        private int BeginTransition()
        {
            _transitionVersion++;
            CancelActiveTransition();
            return _transitionVersion;
        }

        private void CancelActiveTransition()
        {
            DOTween.Kill(this, false);
            overlayImage?.DOKill(false);
            if (overlayImage != null)
            {
                overlayImage.rectTransform.DOKill(false);
            }

            shutterTop?.rectTransform.DOKill(false);
            shutterBottom?.rectTransform.DOKill(false);
        }

        private void PrepareVisibleOverlay(Color color, float alpha)
        {
            transitionVisualRoot.SetActive(true);
            _coverColor = Opaque(color);
            _currentVisual = TransitionVisual.Overlay;

            shutterRoot.gameObject.SetActive(false);
            overlayImage.gameObject.SetActive(true);
            OverlayRect.anchoredPosition = Vector2.zero;
            overlayImage.color = WithAlpha(_coverColor, alpha);
        }

        private void PrepareOverlayForFadeOut()
        {
            if (!transitionVisualRoot.activeSelf)
            {
                PrepareVisibleOverlay(Color.black, 1f);
                return;
            }

            if (_currentVisual == TransitionVisual.Shutter)
            {
                PrepareVisibleOverlay(_coverColor, 1f);
                return;
            }

            var alpha = overlayImage.gameObject.activeSelf ? overlayImage.color.a : 1f;
            PrepareVisibleOverlay(_coverColor, alpha);
        }

        private void PrepareOverlayCovered()
        {
            if (!transitionVisualRoot.activeSelf)
            {
                _coverColor = Color.black;
            }

            PrepareVisibleOverlay(_coverColor, 1f);
        }

        private void PrepareShutter(Color color, float scaleY)
        {
            transitionVisualRoot.SetActive(true);
            _coverColor = Opaque(color);
            _currentVisual = TransitionVisual.Shutter;

            shutterRoot.gameObject.SetActive(true);
            shutterTop.gameObject.SetActive(true);
            shutterBottom.gameObject.SetActive(true);
            shutterTop.color = _coverColor;
            shutterBottom.color = _coverColor;
            SetShutterScale(scaleY);

            // 完全覆盖帧先准备目标节点，再关闭来源节点，避免跨模式切换时漏出背景。
            overlayImage.gameObject.SetActive(false);
        }

        private void CompleteCover(int version)
        {
            if (version != _transitionVersion)
            {
                return;
            }

            _isCovered = true;
        }

        private float GetTransitionWidth()
        {
            Canvas.ForceUpdateCanvases();
            var rectTransform = transitionVisualRoot.transform as RectTransform;
            return Mathf.Max(1f, rectTransform != null ? rectTransform.rect.width : Screen.width);
        }

        private void SetShutterScale(float scaleY)
        {
            var topScale = shutterTop.rectTransform.localScale;
            topScale.y = scaleY;
            shutterTop.rectTransform.localScale = topScale;

            var bottomScale = shutterBottom.rectTransform.localScale;
            bottomScale.y = scaleY;
            shutterBottom.rectTransform.localScale = bottomScale;
        }

        private void ResetVisualsImmediate()
        {
            CancelActiveTransition();

            if (overlayImage != null)
            {
                overlayImage.gameObject.SetActive(true);
                OverlayRect.anchoredPosition = Vector2.zero;
                overlayImage.color = Color.clear;
            }

            if (shutterRoot != null)
            {
                SetShutterScale(0f);
                shutterRoot.gameObject.SetActive(false);
            }

            _coverColor = Color.black;
            _currentVisual = TransitionVisual.None;
            _isCovered = false;
            transitionVisualRoot?.SetActive(false);
        }

        private static Color Opaque(Color color)
        {
            color.a = 1f;
            return color;
        }

        private static Color WithAlpha(Color color, float alpha)
        {
            color.a = alpha;
            return color;
        }

        private static void SetImageAlpha(Graphic graphic, float alpha)
        {
            var color = graphic.color;
            color.a = alpha;
            graphic.color = color;
        }
    }
}