import {
  forwardRef,
  useCallback,
  useEffect,
  useMemo,
  useRef,
  useState,
} from "react";
import type { ImageData, LoopMode } from "../types.ts";

interface ImageCarouselProps {
  images: ImageData["images"];
  currentIndex: number;
  isPlaying: boolean;
  segmentProgress: number;
  mediaSyncToken: number;
  loopMode: LoopMode;
  onTogglePlay: () => void;
  onAnimatedDuration?: (imageId: string, durationMs: number) => void;
}

export const ImageCarousel = forwardRef<HTMLDivElement, ImageCarouselProps>(
  (
    {
      images,
      currentIndex,
      isPlaying,
      segmentProgress,
      mediaSyncToken,
      loopMode,
      onTogglePlay,
      onAnimatedDuration,
    },
    ref,
  ) => {
    const videoRefs = useRef<Map<string, HTMLVideoElement>>(new Map());
    const activeVideoIdRef = useRef<string | null>(null);
    const segmentProgressRef = useRef(segmentProgress);
    const [useLightweightMode, setUseLightweightMode] = useState(false);

    useEffect(() => {
      segmentProgressRef.current = segmentProgress;
    }, [segmentProgress]);

    const syncVideoToSegmentProgress = useCallback(
      (videoEl: HTMLVideoElement, progress: number, force = false) => {
        const duration = videoEl.duration;
        if (!Number.isFinite(duration) || duration <= 0) return;

        const clampedProgress = Math.max(0, Math.min(1, progress));
        const maxTime = Math.max(0, duration - 0.05);
        const targetTime = Math.min(maxTime, duration * clampedProgress);

        if (force || Math.abs(videoEl.currentTime - targetTime) > 0.12) {
          try {
            videoEl.currentTime = targetTime;
          } catch {}
        }
      },
      [],
    );

    useEffect(() => {
      const userAgent = navigator.userAgent;
      const isIOS =
        /iPad|iPhone|iPod/.test(userAgent) ||
        (navigator.platform === "MacIntel" && navigator.maxTouchPoints > 1);
      const isSafari =
        /Safari/.test(userAgent) && !/CriOS|FxiOS|EdgiOS/.test(userAgent);
      setUseLightweightMode(isIOS && isSafari);
    }, []);

    // 虚拟滚动：只渲染当前图片和前后各一张
    const visibleIndices = useMemo(() => {
      if (useLightweightMode) return [currentIndex];

      const indices: number[] = [];
      if (currentIndex > 0) indices.push(currentIndex - 1);
      indices.push(currentIndex);
      if (currentIndex < images.length - 1) indices.push(currentIndex + 1);
      return indices;
    }, [currentIndex, images.length, useLightweightMode]);

    // iOS Safari 对多个同屏 video 很敏感，这里只让当前动图持有 video 元素并跟随全局播放状态。
    useEffect(() => {
      const currentImage = images[currentIndex];
      if (!currentImage?.animated) {
        activeVideoIdRef.current = null;
        videoRefs.current.forEach((videoEl) => videoEl.pause());
        return;
      }

      const videoEl = videoRefs.current.get(currentImage.id);

      videoRefs.current.forEach((itemVideoEl, imageId) => {
        if (imageId !== currentImage.id || !isPlaying) {
          itemVideoEl.pause();
        }
      });

      if (videoEl) {
        if (activeVideoIdRef.current !== currentImage.id) {
          activeVideoIdRef.current = currentImage.id;
          syncVideoToSegmentProgress(videoEl, segmentProgressRef.current, true);
        }

        if (isPlaying) {
          videoEl.play().catch(() => {});
        } else {
          videoEl.pause();
        }
      }
    }, [currentIndex, images, isPlaying, loopMode, syncVideoToSegmentProgress]);

    useEffect(() => {
      const currentImage = images[currentIndex];
      if (!currentImage?.animated) return;

      const videoEl = videoRefs.current.get(currentImage.id);
      if (!videoEl) return;

      syncVideoToSegmentProgress(videoEl, segmentProgressRef.current, true);
      if (isPlaying) videoEl.play().catch(() => {});
    }, [
      currentIndex,
      images,
      isPlaying,
      loopMode,
      mediaSyncToken,
      syncVideoToSegmentProgress,
    ]);

    const handleVideoRef = (el: HTMLVideoElement | null, imageId: string) => {
      if (el) {
        videoRefs.current.set(imageId, el);
      } else {
        videoRefs.current.delete(imageId);
      }
    };

    return (
      <div ref={ref} className="relative h-full w-full overflow-hidden">
        <div className="relative h-full w-full">
          {visibleIndices.map((i) => {
            const img = images[i];
            const isCurrent = i === currentIndex;
            const animatedSrc = isCurrent ? img.animated : null;
            return (
              <div
                key={img.id}
                data-active={isCurrent ? "true" : undefined}
                className="absolute inset-0 h-full w-full flex items-center justify-center bg-black/70 cursor-pointer"
                style={{
                  transform: useLightweightMode
                    ? "translateX(0)"
                    : `translateX(${(i - currentIndex) * 100}%)`,
                  transition: useLightweightMode
                    ? "none"
                    : "transform 240ms ease-out",
                  zIndex: isCurrent ? 1 : 0,
                }}
                onClick={onTogglePlay}
              >
                {animatedSrc ? (
                  <video
                    ref={(el) => handleVideoRef(el, img.id)}
                    src={animatedSrc}
                    poster={img.url}
                    muted
                    playsInline
                    loop={loopMode === "single"}
                    preload={useLightweightMode ? "none" : "metadata"}
                    controls={false}
                    disablePictureInPicture
                    className="max-w-full max-h-full object-contain"
                    style={{
                      width: img.width ? `${img.width}px` : undefined,
                      height: img.height ? `${img.height}px` : undefined,
                    }}
                    onLoadedMetadata={(e) => {
                      const duration = e.currentTarget.duration;
                      if (Number.isFinite(duration) && duration > 0) {
                        onAnimatedDuration?.(
                          img.id,
                          Math.round(duration * 1000),
                        );
                        if (isCurrent) {
                          syncVideoToSegmentProgress(
                            e.currentTarget,
                            segmentProgressRef.current,
                            true,
                          );
                        }
                      }
                    }}
                    onCanPlay={(e) => {
                      if (isCurrent) {
                        syncVideoToSegmentProgress(
                          e.currentTarget,
                          segmentProgressRef.current,
                        );
                      }
                      if (isCurrent && isPlaying)
                        e.currentTarget.play().catch(() => {});
                    }}
                    onEnded={(e) => {
                      // 播放结束后停留在最后一帧
                      if (loopMode !== "single") e.currentTarget.pause();
                    }}
                  />
                ) : (
                  <img
                    src={img.url}
                    alt={`image-${i + 1}`}
                    loading={isCurrent ? "eager" : "lazy"}
                    decoding="async"
                    className="max-w-full max-h-full object-contain"
                    style={{
                      width: img.width ? `${img.width}px` : undefined,
                      height: img.height ? `${img.height}px` : undefined,
                    }}
                  />
                )}
              </div>
            );
          })}
        </div>
      </div>
    );
  },
);

ImageCarousel.displayName = "ImageCarousel";