2026-01-29 18:35:51 +01:00

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TikTok Video Player - Implementation Guide

Overview

This document provides comprehensive TypeScript types, React components, and implementation details for replicating TikTok's video player and infinite scroll mechanism based on deobfuscated source code.

Core TypeScript Types

Video Player State

// Core video detail state management
interface VideoDetailState {
  currentIndex: number;                    // Current video index in the list
  itemListKey: ItemListKey;               // Key for the item list type
  subtitleContent: SubtitleCue[];         // Parsed subtitle/caption content
  ifShowSubtitle: boolean;                // Whether subtitles are visible
  subtitleStruct: SubtitleStruct | null;  // Structured subtitle data
  seekType: SeekType;                     // Type of seek operation
  playMode: PlayMode;                     // Current play mode
  isScrollGuideVisible: boolean;          // Scroll guide visibility
  isYmlRightPanelVisible: boolean;        // Right panel visibility
}

// Video item data structure
interface VideoItem {
  id: string;
  author: {
    nickname?: string;
    uniqueId?: string;
    id?: string;
    secUid?: string;
    avatarThumb?: string;
  };
  video: {
    width?: number;
    height?: number;
    duration?: number;
    ratio?: string;
    playAddr?: string;
  };
  stats: {
    diggCount?: number;
    playCount?: number;
    shareCount?: number;
    commentCount?: number;
    collectCount?: number;
  };
  createTime?: number;
  isPinnedItem?: boolean;
  imagePost?: {
    images: Array<{ url: string }>;
  };
  ad_info?: AdInfo;
  backendSourceEventTracking?: string;
}

// Subtitle/Caption types
interface SubtitleStruct {
  url: string;
  language: string;
  expire?: number;
}

interface SubtitleCue {
  start: number;      // Start time in seconds
  end: number;        // End time in seconds
  text: string;       // Subtitle text content
  startStr: string;   // Formatted start time string
}

interface SubtitleInfo {
  Version: string;
  Format: SubtitleFormat;
  Url: string;
  LanguageCodeName: string;
  UrlExpire?: number;
}

Enums and Constants

// Play modes for different viewing contexts
enum PlayMode {
  VideoDetail = "video_detail",
  OneColumn = "one_column", 
  MiniPlayer = "mini_player"
}

// Seek operation types
enum SeekType {
  None = "none",
  Forward = "forward",
  Backward = "backward",
  Scrub = "scrub"
}

// Enter methods for analytics tracking
enum EnterMethod {
  VideoDetailPage = "video_detail_page",
  VideoCoverClick = "video_cover_click",
  VideoCoverClickAIGCDesc = "video_cover_click_aigc_desc",
  VideoErrorAutoReload = "video_error_auto_reload",
  CreatorCard = "creator_card",
  ClickButton = "click_button"
}

// Subtitle formats
enum SubtitleFormat {
  WebVTT = "webvtt",
  CreatorCaption = "creator_caption"
}

// Item list keys for different content types
enum ItemListKey {
  Video = "video",
  SearchTop = "search_top",
  SearchVideo = "search_video",
  SearchPhoto = "search_photo"
}

// Status codes for API responses
enum StatusCode {
  Ok = 0,
  UnknownError = -1,
  NetworkError = -2
}

React Components with Tailwind CSS

Main Video Feed Container

import React, { useEffect, useRef, useState, useCallback } from 'react';
import { useVideoDetailService } from './hooks/useVideoDetail';

interface VideoFeedProps {
  videos: VideoItem[];
  onLoadMore: () => void;
  hasMore: boolean;
  loading: boolean;
}

export const VideoFeedContainer: React.FC<VideoFeedProps> = ({
  videos,
  onLoadMore,
  hasMore,
  loading
}) => {
  const containerRef = useRef<HTMLDivElement>(null);
  const [currentIndex, setCurrentIndex] = useState(0);
  const videoDetailService = useVideoDetailService();

  // Infinite scroll handler
  const handleScroll = useCallback(() => {
    if (!containerRef.current) return;

    const container = containerRef.current;
    const scrollTop = container.scrollTop;
    const containerHeight = container.clientHeight;
    const scrollHeight = container.scrollHeight;

    // Calculate current video index based on scroll position
    const videoHeight = containerHeight; // Assuming full-height videos
    const newIndex = Math.round(scrollTop / videoHeight);

    if (newIndex !== currentIndex && newIndex >= 0 && newIndex < videos.length) {
      setCurrentIndex(newIndex);
      videoDetailService.handleSwitchVideo({
        newIndex,
        enterMethod: EnterMethod.VideoDetailPage,
        playStatusUpdate: true
      });
    }

    // Load more content when near bottom
    const threshold = 0.8;
    if (scrollTop + containerHeight >= scrollHeight * threshold && hasMore && !loading) {
      onLoadMore();
    }
  }, [currentIndex, videos.length, hasMore, loading, onLoadMore, videoDetailService]);

  useEffect(() => {
    const container = containerRef.current;
    if (!container) return;

    container.addEventListener('scroll', handleScroll, { passive: true });
    return () => container.removeEventListener('scroll', handleScroll);
  }, [handleScroll]);

  return (
    <div 
      ref={containerRef}
      id="column-list-container"
      className="h-screen overflow-y-auto snap-y snap-mandatory"
      style={{ scrollBehavior: 'smooth' }}
    >
      {videos.map((video, index) => (
        <VideoItemContainer
          key={video.id}
          video={video}
          index={index}
          isActive={index === currentIndex}
          onSelect={() => videoDetailService.handleSelectVideo({
            newIndex: index,
            isAIGCDesc: false
          })}
        />
      ))}
      
      {/* Loading placeholder items */}
      {loading && Array.from({ length: 5 }).map((_, index) => (
        <VideoItemPlaceholder key={`placeholder-${index}`} index={videos.length + index} />
      ))}
    </div>
  );
};

Individual Video Item Component

interface VideoItemContainerProps {
  video: VideoItem;
  index: number;
  isActive: boolean;
  onSelect: () => void;
}

export const VideoItemContainer: React.FC<VideoItemContainerProps> = ({
  video,
  index,
  isActive,
  onSelect
}) => {
  const [isLoaded, setIsLoaded] = useState(false);

  return (
    <article
      data-scroll-index={index}
      shape="vertical"
      data-e2e="recommend-list-item-container"
      className={`
        h-screen snap-start flex flex-col transition-all duration-300
        ${isActive ? 'opacity-100' : 'opacity-70'}
        ${isLoaded ? '' : 'animate-pulse'}
      `}
      style={{ transitionDuration: '0ms' }}
    >
      <div className="flex-1 flex">
        <VideoMediaCard
          video={video}
          index={index}
          isActive={isActive}
          onSelect={onSelect}
          onLoad={() => setIsLoaded(true)}
        />
        <VideoActionBar video={video} />
      </div>
    </article>
  );
};

Video Media Card Component

interface VideoMediaCardProps {
  video: VideoItem;
  index: number;
  isActive: boolean;
  onSelect: () => void;
  onLoad: () => void;
}

export const VideoMediaCard: React.FC<VideoMediaCardProps> = ({
  video,
  index,
  isActive,
  onSelect,
  onLoad
}) => {
  const videoRef = useRef<HTMLVideoElement>(null);
  const [isPlaying, setIsPlaying] = useState(false);
  const [progress, setProgress] = useState(0);
  const [duration, setDuration] = useState(0);

  // Auto-play when video becomes active
  useEffect(() => {
    if (videoRef.current && isActive) {
      videoRef.current.play().catch(console.error);
      setIsPlaying(true);
    } else if (videoRef.current && !isActive) {
      videoRef.current.pause();
      setIsPlaying(false);
    }
  }, [isActive]);

  const handleTimeUpdate = useCallback(() => {
    if (videoRef.current) {
      const current = videoRef.current.currentTime;
      const total = videoRef.current.duration;
      setProgress(current / total);
    }
  }, []);

  const handleLoadedMetadata = useCallback(() => {
    if (videoRef.current) {
      setDuration(videoRef.current.duration);
      onLoad();
    }
  }, [onLoad]);

  return (
    <section
      id={`one-column-item-${index}`}
      shape="vertical"
      tabIndex={0}
      role="button"
      aria-label="Watch in full screen"
      data-e2e="feed-video"
      className="flex-1 relative cursor-pointer focus:outline-none focus:ring-2 focus:ring-white/20 rounded-2xl overflow-hidden"
      onClick={onSelect}
    >
      {/* Video placeholder canvas */}
      <canvas
        width="56.25"
        height="100"
        className="absolute inset-0 w-full h-full bg-gray-900"
      />

      {/* Main video container */}
      <div className="relative w-full h-full bg-black rounded-2xl overflow-hidden">
        {/* Video element */}
        <div className="relative w-full h-full">
          <video
            ref={videoRef}
            className="w-full h-full object-cover"
            crossOrigin="use-credentials"
            preload="metadata"
            playsInline
            muted={!isActive}
            onTimeUpdate={handleTimeUpdate}
            onLoadedMetadata={handleLoadedMetadata}
            src={video.video.playAddr}
          />
        </div>

        {/* Video controls overlay */}
        <VideoControlsOverlay
          video={video}
          isPlaying={isPlaying}
          progress={progress}
          duration={duration}
          onPlayPause={() => {
            if (videoRef.current) {
              if (isPlaying) {
                videoRef.current.pause();
              } else {
                videoRef.current.play();
              }
              setIsPlaying(!isPlaying);
            }
          }}
        />

        {/* Video metadata overlay */}
        <VideoMetadataOverlay video={video} />
      </div>
    </section>
  );
};

Video Controls Overlay

interface VideoControlsOverlayProps {
  video: VideoItem;
  isPlaying: boolean;
  progress: number;
  duration: number;
  onPlayPause: () => void;
}

export const VideoControlsOverlay: React.FC<VideoControlsOverlayProps> = ({
  video,
  isPlaying,
  progress,
  duration,
  onPlayPause
}) => {
  const [showControls, setShowControls] = useState(false);
  const [volume, setVolume] = useState(1);
  const [isMuted, setIsMuted] = useState(false);

  const formatTime = (seconds: number) => {
    const mins = Math.floor(seconds / 60);
    const secs = Math.floor(seconds % 60);
    return `${mins.toString().padStart(2, '0')}:${secs.toString().padStart(2, '0')}`;
  };

  return (
    <>
      {/* Top controls */}
      <div className="absolute top-4 left-4 right-4 flex justify-between items-center z-10">
        <div className="flex items-center space-x-2">
          {/* Volume control */}
          <div className="flex items-center space-x-2 bg-black/20 backdrop-blur-sm rounded-full px-3 py-2">
            <button
              onClick={() => setIsMuted(!isMuted)}
              className="text-white hover:text-gray-300 transition-colors"
              aria-label="Volume"
            >
              <svg width="24" height="24" viewBox="0 0 48 48" fill="currentColor">
                <path fillRule="evenodd" clipRule="evenodd" d="M20.3359 8.37236C22.3296 7.04325 25 8.47242 25 10.8685V37.1315C25 39.5276 22.3296 40.9567 20.3359 39.6276L10.3944 33H6C4.34314 33 3 31.6568 3 30V18C3 16.3431 4.34315 15 6 15H10.3944L20.3359 8.37236ZM21 12.737L12.1094 18.6641C11.7809 18.8831 11.3948 19 11 19H7V29H11C11.3948 29 11.7809 29.1169 12.1094 29.3359L21 35.263V12.737Z"/>
              </svg>
            </button>
          </div>
        </div>

        <div className="flex items-center space-x-2">
          {/* More options menu */}
          <button
            className="bg-black/20 backdrop-blur-sm rounded-full p-2 text-white hover:text-gray-300 transition-colors"
            aria-label="More options"
          >
            <svg width="20" height="20" viewBox="0 0 48 48" fill="currentColor">
              <path d="M5 24a4 4 0 1 1 8 0 4 4 0 0 1-8 0Zm15 0a4 4 0 1 1 8 0 4 4 0 0 1-8 0Zm15 0a4 4 0 1 1 8 0 4 4 0 0 1-8 0Z"/>
            </svg>
          </button>
        </div>
      </div>

      {/* Center play/pause button */}
      <div className="absolute inset-0 flex items-center justify-center">
        <button
          onClick={onPlayPause}
          className={`
            bg-black/30 backdrop-blur-sm rounded-full p-4 text-white
            transition-all duration-200 hover:bg-black/40 hover:scale-110
            ${showControls ? 'opacity-100' : 'opacity-0'}
          `}
          aria-label={isPlaying ? "Pause" : "Play"}
        >
          {isPlaying ? (
            <svg width="24" height="24" viewBox="0 0 48 48" fill="currentColor">
              <path d="M16 10a2 2 0 0 0-2 2v24a2 2 0 0 0 2 2h4a2 2 0 0 0 2-2V12a2 2 0 0 0-2-2h-4ZM28 10a2 2 0 0 0-2 2v24a2 2 0 0 0 2 2h4a2 2 0 0 0 2-2V12a2 2 0 0 0-2-2h-4Z"/>
            </svg>
          ) : (
            <svg width="24" height="24" viewBox="0 0 48 48" fill="currentColor">
              <path fillRule="evenodd" clipRule="evenodd" d="M12 8.77702C12 6.43812 14.5577 4.99881 16.5569 6.21266L41.6301 21.4356C43.5542 22.6038 43.5542 25.3962 41.6301 26.5644L16.5569 41.7873C14.5577 43.0012 12 41.5619 12 39.223V8.77702Z"/>
            </svg>
          )}
        </button>
      </div>

      {/* Bottom progress bar and time display */}
      <div className="absolute bottom-4 left-4 right-4 z-10">
        <div className="mb-2">
          <p className="text-white text-2xl font-bold text-center">
            {formatTime(duration * progress)} / {formatTime(duration)}
          </p>
        </div>
        
        <div className="relative">
          <div className="w-full h-1 bg-white/20 rounded-full overflow-hidden">
            <div 
              className="h-full bg-white transition-all duration-100"
              style={{ width: `${progress * 100}%` }}
            />
          </div>
          
          {/* Scrub handle */}
          <div 
            className="absolute top-1/2 -translate-y-1/2 w-3 h-3 bg-white rounded-full shadow-lg"
            style={{ left: `${progress * 100}%`, marginLeft: '-6px' }}
          />
        </div>
      </div>
    </>
  );
};

Video Action Bar (Right Side)

interface VideoActionBarProps {
  video: VideoItem;
}

export const VideoActionBar: React.FC<VideoActionBarProps> = ({ video }) => {
  const [isFollowing, setIsFollowing] = useState(false);
  const [isLiked, setIsLiked] = useState(false);

  const formatCount = (count: number): string => {
    if (count >= 1000000) {
      return `${(count / 1000000).toFixed(1)}M`;
    } else if (count >= 1000) {
      return `${(count / 1000).toFixed(1)}K`;
    }
    return count.toString();
  };

  return (
    <section className="flex flex-col items-center justify-end space-y-4 p-4 min-w-[80px]">
      {/* Author avatar and follow button */}
      <div className="flex flex-col items-center space-y-2">
        <a
          href={`/@${video.author.uniqueId}`}
          className="relative block focus:outline-none focus:ring-2 focus:ring-white/20 rounded-full"
        >
          <div className="w-12 h-12 rounded-full overflow-hidden border-2 border-white/20">
            <img
              src={video.author.avatarThumb}
              alt={video.author.nickname}
              className="w-full h-full object-cover"
              loading="lazy"
            />
          </div>
        </a>
        
        <button
          onClick={() => setIsFollowing(!isFollowing)}
          className={`
            w-6 h-6 rounded-full flex items-center justify-center text-white
            transition-all duration-200 hover:scale-110
            ${isFollowing 
              ? 'bg-gray-600 hover:bg-gray-700' 
              : 'bg-red-500 hover:bg-red-600'
            }
          `}
          aria-label={isFollowing ? "Unfollow" : "Follow"}
        >
          {isFollowing ? (
            <svg width="16" height="16" viewBox="0 0 48 48" fill="currentColor">
              <path fillRule="evenodd" clipRule="evenodd" d="M43 6.08c.7.45 1.06.67 1.25.98.16.27.23.59.2.9-.03.36-.26.72-.7 1.43L23.06 42.14a3.5 3.5 0 0 1-5.63.39L4.89 27.62c-.54-.64-.81-.96-.9-1.32a1.5 1.5 0 0 1 .09-.92c.14-.33.46-.6 1.1-1.14l1.69-1.42c.64-.54.96-.81 1.31-.9.3-.06.63-.04.92.09.34.14.6.46 1.15 1.1l9.46 11.25 18.11-28.7c.45-.72.68-1.07.99-1.26.27-.16.59-.23.9-.2.36.03.71.25 1.43.7L43 6.08Z"/>
            </svg>
          ) : (
            <svg width="16" height="16" viewBox="0 0 48 48" fill="currentColor">
              <path d="M26 7a1 1 0 0 0-1-1h-2a1 1 0 0 0-1 1v15H7a1 1 0 0 0-1 1v2a1 1 0 0 0 1 1h15v15a1 1 0 0 0 1 1h2a1 1 0 0 0 1-1V26h15a1 1 0 0 0 1-1v-2a1 1 0 0 0-1-1H26V7Z"/>
            </svg>
          )}
        </button>
      </div>

      {/* Action buttons */}
      <div className="flex flex-col items-center space-y-6">
        {/* Like button */}
        <button
          onClick={() => setIsLiked(!isLiked)}
          className="flex flex-col items-center space-y-1 text-white hover:text-red-400 transition-colors group"
          aria-label={`${isLiked ? 'Unlike' : 'Like'} video`}
        >
          <div className={`p-2 rounded-full transition-all duration-200 group-hover:scale-110 ${isLiked ? 'text-red-500' : ''}`}>
            <svg width="24" height="24" viewBox="0 0 24 24" fill="currentColor">
              <path fillRule="evenodd" clipRule="evenodd" d="M7.5 2.25C10.5 2.25 12 4.25 12 4.25C12 4.25 13.5 2.25 16.5 2.25C20 2.25 22.5 4.99999 22.5 8.5C22.5 12.5 19.2311 16.0657 16.25 18.75C14.4095 20.4072 13 21.5 12 21.5C11 21.5 9.55051 20.3989 7.75 18.75C4.81949 16.0662 1.5 12.5 1.5 8.5C1.5 4.99999 4 2.25 7.5 2.25Z"/>
            </svg>
          </div>
          <span className="text-xs font-semibold">
            {formatCount(video.stats.diggCount || 0)}
          </span>
        </button>

        {/* Comment button */}
        <button className="flex flex-col items-center space-y-1 text-white hover:text-blue-400 transition-colors group">
          <div className="p-2 rounded-full transition-all duration-200 group-hover:scale-110">
            <svg width="24" height="24" viewBox="0 0 48 48" fill="currentColor">
              <path fillRule="evenodd" d="M2 21.5c0-10.22 9.88-18 22-18s22 7.78 22 18c0 5.63-3.19 10.74-7.32 14.8a43.6 43.6 0 0 1-14.14 9.1A1.5 1.5 0 0 1 22.5 44v-5.04C11.13 38.4 2 31.34 2 21.5M14 25a3 3 0 1 0 0-6 3 3 0 0 0 0 6m10 0a3 3 0 1 0 0-6 3 3 0 0 0 0 6m13-3a3 3 0 1 1-6 0 3 3 0 0 1 6 0" clipRule="evenodd"/>
            </svg>
          </div>
          <span className="text-xs font-semibold">
            {formatCount(video.stats.commentCount || 0)}
          </span>
        </button>

        {/* Bookmark button */}
        <button className="flex flex-col items-center space-y-1 text-white hover:text-yellow-400 transition-colors group">
          <div className="p-2 rounded-full transition-all duration-200 group-hover:scale-110">
            <svg width="24" height="24" viewBox="0 0 24 24" fill="currentColor">
              <path d="M4 4.5a2 2 0 0 1 2-2h12a2 2 0 0 1 2 2v15.13a1 1 0 0 1-1.555.831l-6.167-4.12a.5.5 0 0 0-.556 0l-6.167 4.12A1 1 0 0 1 4 19.63z"/>
            </svg>
          </div>
          <span className="text-xs font-semibold">
            {formatCount(video.stats.collectCount || 0)}
          </span>
        </button>

        {/* Share button */}
        <button className="flex flex-col items-center space-y-1 text-white hover:text-green-400 transition-colors group">
          <div className="p-2 rounded-full transition-all duration-200 group-hover:scale-110">
            <svg width="24" height="24" viewBox="0 0 20 20" fill="currentColor">
              <path fillRule="evenodd" d="M10.938 3.175a.674.674 0 0 1 1.138-.488l6.526 6.215c.574.547.554 1.47-.043 1.991l-6.505 5.676a.674.674 0 0 1-1.116-.508V13.49s-6.985-1.258-9.225 2.854c-.209.384-1.023.518-.857-1.395.692-3.52 2.106-9.017 10.082-9.017z" clipRule="evenodd"/>
            </svg>
          </div>
          <span className="text-xs font-semibold">
            {formatCount(video.stats.shareCount || 0)}
          </span>
        </button>

        {/* Music disc */}
        <a
          href={`/music/original-sound-${video.id}`}
          className="block focus:outline-none focus:ring-2 focus:ring-white/20 rounded-full"
        >
          <div 
            className="w-10 h-10 rounded-full bg-cover bg-center animate-spin-slow border-2 border-white/20"
            style={{ 
              backgroundImage: `url("${video.author.avatarThumb}")`,
              animationDuration: '3s'
            }}
          />
        </a>
      </div>
    </>
  );
};

Video Metadata Overlay

interface VideoMetadataOverlayProps {
  video: VideoItem;
}

export const VideoMetadataOverlay: React.FC<VideoMetadataOverlayProps> = ({ video }) => {
  const [isExpanded, setIsExpanded] = useState(false);

  return (
    <div className="absolute bottom-4 left-4 right-20 z-10">
      <div className="space-y-2">
        {/* Author name */}
        <div>
          <a
            href={`/@${video.author.uniqueId}`}
            className="text-white font-semibold hover:underline focus:outline-none focus:underline"
          >
            {video.author.nickname || video.author.uniqueId}
          </a>
        </div>

        {/* Video description */}
        <div className="text-white">
          <div 
            className={`
              text-sm leading-relaxed whitespace-pre-wrap
              ${isExpanded ? '' : 'line-clamp-2'}
            `}
          >
            {/* Parse description with hashtags */}
            <VideoDescription 
              description={video.description || ""}
              onHashtagClick={(hashtag) => {
                // Handle hashtag navigation
                window.location.href = `/tag/${hashtag}`;
              }}
            />
          </div>
          
          {!isExpanded && (
            <button
              onClick={() => setIsExpanded(true)}
              className="text-white/70 hover:text-white text-sm mt-1 transition-colors"
            >
              more
            </button>
          )}
        </div>

        {/* Effects and music info */}
        <div className="flex items-center space-x-2 text-white/80 text-xs">
          {/* Effect tag */}
          {video.effectInfo && (
            <div className="flex items-center space-x-1 bg-black/20 backdrop-blur-sm rounded px-2 py-1">
              <img 
                src={video.effectInfo.iconUrl} 
                alt="Effect"
                className="w-4 h-4"
              />
              <span>{video.effectInfo.name}</span>
            </div>
          )}
        </div>
      </div>
    </div>
  );
};

Video Description Parser

interface VideoDescriptionProps {
  description: string;
  onHashtagClick: (hashtag: string) => void;
}

export const VideoDescription: React.FC<VideoDescriptionProps> = ({
  description,
  onHashtagClick
}) => {
  const parseDescription = (text: string) => {
    const hashtagRegex = /#(\w+)/g;
    const parts = [];
    let lastIndex = 0;
    let match;

    while ((match = hashtagRegex.exec(text)) !== null) {
      // Add text before hashtag
      if (match.index > lastIndex) {
        parts.push({
          type: 'text',
          content: text.slice(lastIndex, match.index)
        });
      }

      // Add hashtag
      parts.push({
        type: 'hashtag',
        content: match[0],
        hashtag: match[1]
      });

      lastIndex = match.index + match[0].length;
    }

    // Add remaining text
    if (lastIndex < text.length) {
      parts.push({
        type: 'text',
        content: text.slice(lastIndex)
      });
    }

    return parts;
  };

  const parts = parseDescription(description);

  return (
    <>
      {parts.map((part, index) => (
        part.type === 'hashtag' ? (
          <button
            key={index}
            onClick={() => onHashtagClick(part.hashtag)}
            className="text-blue-300 hover:text-blue-200 font-semibold transition-colors"
          >
            {part.content}
          </button>
        ) : (
          <span key={index}>{part.content}</span>
        )
      ))}
    </>
  );
};

Video Item Placeholder

interface VideoItemPlaceholderProps {
  index: number;
}

export const VideoItemPlaceholder: React.FC<VideoItemPlaceholderProps> = ({ index }) => {
  return (
    <article
      data-scroll-index={index}
      className="h-screen snap-start flex animate-pulse"
    >
      <div className="flex-1 bg-gray-800 rounded-2xl m-4">
        <div className="relative w-full h-full">
          {/* Placeholder content */}
          <div className="absolute inset-0 bg-gradient-to-br from-gray-700 to-gray-900 rounded-2xl" />
          
          {/* Placeholder metadata */}
          <div className="absolute bottom-4 left-4 right-20 space-y-2">
            <div className="h-4 bg-gray-600 rounded w-24" />
            <div className="h-3 bg-gray-600 rounded w-full" />
            <div className="h-3 bg-gray-600 rounded w-3/4" />
          </div>
        </div>
      </div>
      
      {/* Placeholder action bar */}
      <div className="flex flex-col items-center justify-end space-y-4 p-4 min-w-[80px]">
        <div className="w-12 h-12 bg-gray-600 rounded-full" />
        <div className="w-6 h-6 bg-gray-600 rounded-full" />
        <div className="w-8 h-8 bg-gray-600 rounded-full" />
        <div className="w-8 h-8 bg-gray-600 rounded-full" />
        <div className="w-8 h-8 bg-gray-600 rounded-full" />
        <div className="w-10 h-10 bg-gray-600 rounded-full" />
      </div>
    </article>
  );
};

Infinite Scroll Implementation

Core Scrolling Logic

// Custom hook for infinite scroll video feed
export const useInfiniteVideoScroll = (
  videos: VideoItem[],
  onLoadMore: () => void,
  hasMore: boolean
) => {
  const [currentIndex, setCurrentIndex] = useState(0);
  const [isLoading, setIsLoading] = useState(false);
  const containerRef = useRef<HTMLDivElement>(null);

  // Scroll event handler with throttling
  const handleScroll = useCallback(
    throttle(() => {
      if (!containerRef.current) return;

      const container = containerRef.current;
      const scrollTop = container.scrollTop;
      const containerHeight = container.clientHeight;
      const scrollHeight = container.scrollHeight;

      // Calculate current video index based on scroll position
      const videoHeight = containerHeight;
      const newIndex = Math.round(scrollTop / videoHeight);

      // Update current index if changed
      if (newIndex !== currentIndex && newIndex >= 0 && newIndex < videos.length) {
        setCurrentIndex(newIndex);
        
        // Track video switch analytics
        trackVideoSwitch({
          fromIndex: currentIndex,
          toIndex: newIndex,
          scrollPosition: scrollTop,
          timestamp: Date.now()
        });
      }

      // Preload more content when approaching end
      const preloadThreshold = 0.8;
      const shouldLoadMore = scrollTop + containerHeight >= scrollHeight * preloadThreshold;
      
      if (shouldLoadMore && hasMore && !isLoading) {
        setIsLoading(true);
        onLoadMore();
      }

      // Preload next videos when within 6 items of current
      const preloadDistance = 6;
      if (videos.length - newIndex < preloadDistance && hasMore && !isLoading) {
        preloadNextVideos(newIndex, preloadDistance);
      }
    }, 100),
    [currentIndex, videos.length, hasMore, isLoading, onLoadMore]
  );

  return {
    containerRef,
    currentIndex,
    handleScroll,
    isLoading
  };
};

// Throttle utility function
function throttle<T extends (...args: any[]) => any>(
  func: T,
  delay: number
): (...args: Parameters<T>) => void {
  let timeoutId: NodeJS.Timeout | null = null;
  let lastExecTime = 0;
  
  return (...args: Parameters<T>) => {
    const currentTime = Date.now();
    
    if (currentTime - lastExecTime > delay) {
      func(...args);
      lastExecTime = currentTime;
    } else {
      if (timeoutId) clearTimeout(timeoutId);
      timeoutId = setTimeout(() => {
        func(...args);
        lastExecTime = Date.now();
      }, delay - (currentTime - lastExecTime));
    }
  };
}

Video Preloading Strategy

// Video preloading service
export class VideoPreloadService {
  private preloadedVideos = new Map<string, HTMLVideoElement>();
  private preloadQueue: string[] = [];
  private maxPreloadCount = 3;

  /**
   * Preload videos ahead of current position
   */
  preloadNextVideos(currentIndex: number, videos: VideoItem[], preloadDistance: number = 3) {
    const startIndex = currentIndex + 1;
    const endIndex = Math.min(startIndex + preloadDistance, videos.length);

    for (let i = startIndex; i < endIndex; i++) {
      const video = videos[i];
      if (video && video.video.playAddr && !this.preloadedVideos.has(video.id)) {
        this.preloadVideo(video);
      }
    }

    // Clean up old preloaded videos
    this.cleanupOldPreloads(currentIndex, preloadDistance);
  }

  /**
   * Preload individual video
   */
  private preloadVideo(video: VideoItem) {
    if (this.preloadQueue.length >= this.maxPreloadCount) {
      return; // Queue is full
    }

    const videoElement = document.createElement('video');
    videoElement.preload = 'metadata';
    videoElement.crossOrigin = 'use-credentials';
    videoElement.src = video.video.playAddr || '';

    // Add to preload tracking
    this.preloadedVideos.set(video.id, videoElement);
    this.preloadQueue.push(video.id);

    // Handle preload completion
    videoElement.addEventListener('loadedmetadata', () => {
      console.log(`Preloaded video: ${video.id}`);
    });

    videoElement.addEventListener('error', () => {
      console.warn(`Failed to preload video: ${video.id}`);
      this.preloadedVideos.delete(video.id);
      this.preloadQueue = this.preloadQueue.filter(id => id !== video.id);
    });
  }

  /**
   * Clean up old preloaded videos to free memory
   */
  private cleanupOldPreloads(currentIndex: number, keepDistance: number) {
    const videosToKeep = new Set<string>();
    
    // Keep videos within distance of current index
    for (let i = Math.max(0, currentIndex - keepDistance); 
         i < currentIndex + keepDistance; i++) {
      if (this.preloadQueue[i]) {
        videosToKeep.add(this.preloadQueue[i]);
      }
    }

    // Remove videos outside keep range
    this.preloadedVideos.forEach((videoElement, videoId) => {
      if (!videosToKeep.has(videoId)) {
        videoElement.src = '';
        this.preloadedVideos.delete(videoId);
      }
    });

    this.preloadQueue = this.preloadQueue.filter(id => videosToKeep.has(id));
  }

  /**
   * Get preloaded video element
   */
  getPreloadedVideo(videoId: string): HTMLVideoElement | null {
    return this.preloadedVideos.get(videoId) || null;
  }
}

Infinite Scroll Mechanism Analysis

Key Insights from DOM Structure

Based on the provided DOM structure, TikTok's infinite scroll works as follows:

Container Structure:

<div id="column-list-container" class="css-1leh6wy-5e6d46e3--DivColumnListContainer">
  <article data-scroll-index="0">...</article>  <!-- Active video -->
  <article data-scroll-index="1">...</article>  <!-- Empty placeholder -->
  <article data-scroll-index="2">...</article>  <!-- Empty placeholder -->
  <!-- ... more empty placeholders ... -->
  <article data-scroll-index="32">...</article> <!-- Next loaded video -->
  <article data-scroll-index="33">...</article> <!-- Another loaded video -->
</div>

Loading Strategy:
- Sparse Loading: Only loads content for visible and near-visible videos
- Placeholder Articles: Creates empty <article> elements as placeholders
- Dynamic Content: Populates placeholders when they come into view
- Memory Management: Unloads content from videos far from current position
Scroll Detection:
- Uses data-scroll-index attributes for position tracking
- Calculates current video based on scroll position
- Triggers content loading when approaching new videos

Implementation Strategy

// Main video feed hook
export const useVideoFeed = () => {
  const [videos, setVideos] = useState<VideoItem[]>([]);
  const [currentIndex, setCurrentIndex] = useState(0);
  const [hasMore, setHasMore] = useState(true);
  const [loading, setLoading] = useState(false);

  // Create placeholder structure (similar to TikTok)
  const createPlaceholders = (count: number, startIndex: number = 0) => {
    return Array.from({ length: count }, (_, i) => ({
      id: `placeholder-${startIndex + i}`,
      isPlaceholder: true,
      index: startIndex + i
    }));
  };

  // Load more videos when needed
  const loadMoreVideos = useCallback(async () => {
    if (loading || !hasMore) return;

    setLoading(true);
    try {
      const newVideos = await fetchMoreVideos(videos.length);
      setVideos(prev => [...prev, ...newVideos]);
      setHasMore(newVideos.length > 0);
    } catch (error) {
      console.error('Failed to load more videos:', error);
    } finally {
      setLoading(false);
    }
  }, [videos.length, loading, hasMore]);

  // Populate placeholder with actual content
  const populateVideo = useCallback(async (index: number) => {
    if (videos[index] && !videos[index].isPlaceholder) return;

    try {
      const videoData = await fetchVideoAtIndex(index);
      setVideos(prev => {
        const newVideos = [...prev];
        newVideos[index] = videoData;
        return newVideos;
      });
    } catch (error) {
      console.error(`Failed to load video at index ${index}:`, error);
    }
  }, [videos]);

  return {
    videos,
    currentIndex,
    hasMore,
    loading,
    loadMoreVideos,
    populateVideo,
    setCurrentIndex
  };
};

WebVTT Subtitle System

Subtitle Parser Implementation

// WebVTT subtitle parser
export class WebVTTParser {
  static parse(vttContent: string, options: ParseOptions = {}): WebVTTResult {
    const { strict = true, includeMeta = false } = options;
    
    if (!vttContent || typeof vttContent !== 'string') {
      return { cues: [], valid: false, errors: [] };
    }

    try {
      // Normalize content
      const normalized = vttContent
        .trim()
        .replace(/\r\n/g, '\n')
        .replace(/\r/g, '\n');

      const blocks = normalized.split('\n\n');
      const header = blocks.shift();

      // Validate WebVTT header
      if (!header?.startsWith('WEBVTT')) {
        throw new Error('Invalid WebVTT format: must start with "WEBVTT"');
      }

      // Parse cues
      const cues: SubtitleCue[] = [];
      const errors: Error[] = [];

      blocks.forEach((block, index) => {
        try {
          const cue = this.parseCue(block, index, strict);
          if (cue) cues.push(cue);
        } catch (error) {
          errors.push(error as Error);
        }
      });

      if (strict && errors.length > 0) {
        throw errors[0];
      }

      return {
        valid: errors.length === 0,
        strict,
        cues,
        errors,
        meta: includeMeta ? this.parseMetadata(header) : undefined
      };
    } catch (error) {
      return {
        valid: false,
        strict,
        cues: [],
        errors: [error as Error]
      };
    }
  }

  private static parseCue(block: string, index: number, strict: boolean): SubtitleCue | null {
    const lines = block.split('\n').filter(Boolean);
    
    if (lines.length === 0) return null;
    
    // Skip NOTE blocks
    if (lines[0].trim().startsWith('NOTE')) return null;

    // Find timestamp line
    const timestampLineIndex = lines.findIndex(line => line.includes('-->'));
    if (timestampLineIndex === -1) {
      throw new Error(`No timestamp found in cue ${index}`);
    }

    const timestampLine = lines[timestampLineIndex];
    const [startStr, endStr] = timestampLine.split(' --> ');

    if (!startStr || !endStr) {
      throw new Error(`Invalid timestamp format in cue ${index}`);
    }

    const startTime = this.parseTimestamp(startStr);
    const endTime = this.parseTimestamp(endStr);

    // Validate timestamp order
    if (strict && startTime >= endTime) {
      throw new Error(`Invalid timestamp order in cue ${index}`);
    }

    // Extract cue text (everything after timestamp line)
    const textLines = lines.slice(timestampLineIndex + 1);
    const text = textLines.join('\n').trim();

    if (!text) return null;

    return {
      start: startTime,
      end: endTime,
      text,
      startStr: this.formatTime(startTime)
    };
  }

  private static parseTimestamp(timeStr: string): number {
    const match = timeStr.match(/(?:(\d{1,2}):)?(\d{2}):(\d{2})\.(\d{3})/);
    if (!match) throw new Error(`Invalid timestamp format: ${timeStr}`);

    const [, hours = '0', minutes, seconds, milliseconds] = match;
    return (
      parseInt(hours) * 3600 +
      parseInt(minutes) * 60 +
      parseInt(seconds) +
      parseInt(milliseconds) / 1000
    );
  }

  private static formatTime(seconds: number): string {
    const hours = Math.floor(seconds / 3600);
    const mins = Math.floor((seconds % 3600) / 60);
    const secs = Math.floor(seconds % 60);

    if (hours > 0) {
      return `${hours}:${mins.toString().padStart(2, '0')}:${secs.toString().padStart(2, '0')}`;
    }
    return `${mins}:${secs.toString().padStart(2, '0')}`;
  }

  private static parseMetadata(header: string): Record<string, string> | undefined {
    const lines = header.split('\n').slice(1); // Skip WEBVTT line
    const metadata: Record<string, string> = {};

    lines.forEach(line => {
      const colonIndex = line.indexOf(':');
      if (colonIndex > 0) {
        const key = line.slice(0, colonIndex).trim();
        const value = line.slice(colonIndex + 1).trim();
        metadata[key] = value;
      }
    });

    return Object.keys(metadata).length > 0 ? metadata : undefined;
  }
}

interface ParseOptions {
  strict?: boolean;
  includeMeta?: boolean;
}

interface WebVTTResult {
  valid: boolean;
  strict: boolean;
  cues: SubtitleCue[];
  errors: Error[];
  meta?: Record<string, string>;
}

Usage Example

Complete Implementation

import React from 'react';
import { VideoFeedContainer } from './components/VideoFeedContainer';
import { useVideoFeed } from './hooks/useVideoFeed';
import { VideoPreloadService } from './services/VideoPreloadService';

const App: React.FC = () => {
  const {
    videos,
    currentIndex,
    hasMore,
    loading,
    loadMoreVideos,
    populateVideo
  } = useVideoFeed();

  const preloadService = new VideoPreloadService();

  // Handle video index changes for preloading
  useEffect(() => {
    preloadService.preloadNextVideos(currentIndex, videos);
  }, [currentIndex, videos]);

  return (
    <div className="h-screen bg-black">
      <VideoFeedContainer
        videos={videos}
        onLoadMore={loadMoreVideos}
        hasMore={hasMore}
        loading={loading}
      />
    </div>
  );
};

export default App;

Advanced Scrolling Mechanism (Updated)

Based on the additional deobfuscated file (89650.836eaa0d.js), TikTok uses a sophisticated Swiper Mode Module for video navigation:

// Enhanced swiper navigation system
interface SwiperModeState {
  currentIndex: Record<string, number>;    // Current indices by list type
  disabled: boolean;                       // Navigation disabled state
  itemListKey: ItemListKey;               // Current item list key
  onboardingShowing: boolean;             // Onboarding modal state
  loginCTAShowing: boolean;               // Login prompt state
  leavingModalShowing: boolean;           // Exit confirmation state
  playbackRate: number;                   // Video playback speed
  dimmer: boolean;                        // Screen dimmer state
  showBrowseMode: boolean;                // Browse mode state
  needLeavingModal: boolean;              // Exit modal requirement
  iconType: IconType;                     // Current control icon
  seekType: SeekType;                     // Seek operation type
}

enum IconType {
  None = "none",
  Mute = "mute", 
  Unmute = "unmute",
  Play = "play",
  Pause = "pause"
}

enum SeekType {
  Forward = "forward",
  BackWard = "backward", 
  None = "none"
}

// Enhanced navigation service
export class VideoNavigationService {
  /**
   * Navigate to next video with analytics tracking
   */
  async handleNextVideo(currentState: SwiperModeState): Promise<void> {
    // Report interaction start
    this.reportVideoInteraction({
      startTime: Date.now(),
      situation: 'SwiperSlideNext'
    });

    const { itemListKey, currentIndex } = currentState;
    const browserList = this.getBrowserList(itemListKey);
    const currentIdx = currentIndex[itemListKey] || 0;
    const nextIndex = Math.min(currentIdx + 1, browserList.length - 1);

    if (this.canNavigate(nextIndex, browserList)) {
      await this.updateVideoIndex({
        newIndex: nextIndex,
        newId: browserList[nextIndex],
        playMode: currentState.playMode,
        itemListKey
      });
    }
  }

  /**
   * Navigate to previous video with analytics tracking  
   */
  async handlePrevVideo(currentState: SwiperModeState): Promise<void> {
    // Report interaction start
    this.reportVideoInteraction({
      startTime: Date.now(),
      situation: 'SwiperSlidePrev'
    });

    const { itemListKey, currentIndex } = currentState;
    const browserList = this.getBrowserList(itemListKey);
    const currentIdx = currentIndex[itemListKey] || 0;
    const prevIndex = Math.max(currentIdx - 1, 0);

    if (this.canNavigate(prevIndex, browserList)) {
      await this.updateVideoIndex({
        newIndex: prevIndex,
        newId: browserList[prevIndex],
        playMode: currentState.playMode,
        itemListKey
      });
    }
  }

  /**
   * Core video index update with comprehensive state management
   */
  private async updateVideoIndex(params: {
    newIndex: number;
    newId: string;
    playMode: PlayMode;
    itemListKey: string;
  }): Promise<void> {
    const { newIndex, newId, playMode, itemListKey } = params;

    // Update video player state
    await this.videoPlayerService.updateVideo({
      currentVideo: {
        index: newIndex,
        id: newId,
        mode: playMode
      },
      playProgress: 0
    });

    // Update swiper current index
    this.setSwiperCurrentIndex({
      key: itemListKey,
      value: newIndex
    });

    // Trigger preloading if near end of list
    if (this.shouldPreload(newIndex, this.getBrowserList(itemListKey))) {
      await this.preloadMoreContent(newIndex, newId);
    }
  }
}

Comment System Integration

The scrolling system is tightly integrated with TikTok's comment system:

// Comment state management for video feed
interface CommentState {
  awemeId?: string;
  cursor: string;
  comments: CommentItem[];
  hasMore: boolean;
  loading: boolean;
  isFirstLoad: boolean;
  fetchType: 'load_by_current' | 'preload_by_ml';
  currentAspect: 'all' | string;
}

interface CommentItem {
  cid: string;
  user_digged: boolean;
  is_author_digged: boolean;
  digg_count: number;
  reply_comment_total: number;
  reply_comment?: CommentItem[];
  replyCache?: {
    comments: CommentItem[];
    cursor: string;
    hasMore: boolean;
    loading: boolean;
  };
}

// Comment preloading service
export class CommentPreloadService {
  /**
   * Preload comments for upcoming videos
   */
  async preloadComments(videoId: string, fetchType: string = 'preload_by_ml'): Promise<void> {
    try {
      const response = await this.fetchComments({
        aweme_id: videoId,
        cursor: '0',
        count: 20,
        fetch_type: fetchType
      });

      if (response.status_code === 0 && response.comments?.length) {
        // Process and cache comment data
        const processedData = this.processCommentData(response.comments);
        
        // Update comment state
        this.setCommentItem({
          item: {
            comments: processedData.comments,
            hasMore: !!response.has_more,
            cursor: response.cursor,
            loading: false,
            isFirstLoad: true,
            fetchType
          },
          itemId: videoId
        });

        // Update user data
        this.updateUserData(processedData.users);
      }
    } catch (error) {
      console.error('Comment preload failed:', error);
    }
  }
}

Key Implementation Notes

1. Sparse Loading Pattern

TikTok creates placeholder <article> elements for the entire scroll range
Only populates content when videos come into view
This prevents excessive DOM manipulation and memory usage

Uses data-scroll-index attributes for position tracking
Calculates current video based on scroll position relative to container height
Smooth transitions with CSS snap-scroll properties

3. Preloading Strategy

Preloads metadata for upcoming videos
Loads full video content when within 6 items of current position
Cleans up old preloaded content to manage memory

4. Analytics Integration

Tracks every video switch with detailed metrics
Records scroll patterns and engagement data
Integrates with TikTok's comprehensive analytics system

5. Performance Optimizations

Throttled scroll event handlers
Lazy loading of video content
Memory management for preloaded videos
CSS-based smooth scrolling with hardware acceleration

Swiper Mode Module: Dedicated service for next/prev navigation
Multi-List Support: Handles different content types (ForYou, Search, etc.)
State Validation: Comprehensive checks before navigation
Analytics Integration: Detailed tracking for every navigation event

7. Advanced Comment System

ML-Driven Preloading: Comments preloaded using machine learning predictions
Threaded Replies: Nested reply system with separate caching
Real-time Interactions: Instant like/unlike with optimistic updates
Translation Support: Multi-language comment translation
Topic Filtering: Comments can be filtered by topics and categories
Batch Operations: Efficient bulk comment operations

This implementation replicates TikTok's sophisticated video feed system while providing clean TypeScript interfaces and React components that can be styled with Tailwind CSS.

Tailwind CSS Configuration

Add these custom utilities to your tailwind.config.js:

module.exports = {
  theme: {
    extend: {
      animation: {
        'spin-slow': 'spin 3s linear infinite',
      },
      backdropBlur: {
        'xs': '2px',
      }
    }
  },
  plugins: [
    require('@tailwindcss/line-clamp'),
  ]
}

Enhanced React Hook Implementation

import { useCallback, useEffect, useRef, useState } from 'react';

interface UseSwiperNavigationProps {
  videos: VideoItem[];
  onVideoChange: (index: number) => void;
  onLoadMore: () => void;
  hasMore: boolean;
}

export const useSwiperNavigation = ({
  videos,
  onVideoChange,
  onLoadMore,
  hasMore
}: UseSwiperNavigationProps) => {
  const [currentIndex, setCurrentIndex] = useState(0);
  const [isNavigating, setIsNavigating] = useState(false);
  const [swiperState, setSwiperState] = useState<SwiperModeState>({
    currentIndex: { video: 0 },
    disabled: false,
    itemListKey: ItemListKey.Video,
    onboardingShowing: false,
    loginCTAShowing: false,
    leavingModalShowing: false,
    playbackRate: 1,
    dimmer: false,
    showBrowseMode: false,
    needLeavingModal: false,
    iconType: IconType.None,
    seekType: SeekType.None
  });

  // Navigation service instance
  const navigationService = useRef(new VideoNavigationService());

  /**
   * Handle next video navigation
   */
  const handleNextVideo = useCallback(async () => {
    if (isNavigating || swiperState.disabled) return;
    
    setIsNavigating(true);
    
    try {
      await navigationService.current.handleNextVideo(swiperState);
      
      const nextIndex = Math.min(currentIndex + 1, videos.length - 1);
      setCurrentIndex(nextIndex);
      onVideoChange(nextIndex);
      
      // Trigger load more if near end
      if (videos.length - nextIndex < 6 && hasMore) {
        onLoadMore();
      }
    } catch (error) {
      console.error('Navigation to next video failed:', error);
    } finally {
      setIsNavigating(false);
    }
  }, [currentIndex, videos.length, isNavigating, swiperState, onVideoChange, onLoadMore, hasMore]);

  /**
   * Handle previous video navigation
   */
  const handlePrevVideo = useCallback(async () => {
    if (isNavigating || swiperState.disabled) return;
    
    setIsNavigating(true);
    
    try {
      await navigationService.current.handlePrevVideo(swiperState);
      
      const prevIndex = Math.max(currentIndex - 1, 0);
      setCurrentIndex(prevIndex);
      onVideoChange(prevIndex);
    } catch (error) {
      console.error('Navigation to previous video failed:', error);
    } finally {
      setIsNavigating(false);
    }
  }, [currentIndex, isNavigating, swiperState, onVideoChange]);

  /**
   * Handle keyboard navigation
   */
  useEffect(() => {
    const handleKeyDown = (event: KeyboardEvent) => {
      switch (event.key) {
        case 'ArrowUp':
          event.preventDefault();
          handlePrevVideo();
          break;
        case 'ArrowDown':
          event.preventDefault();
          handleNextVideo();
          break;
        case ' ':
          event.preventDefault();
          // Handle play/pause
          setSwiperState(prev => ({
            ...prev,
            iconType: prev.iconType === IconType.Play ? IconType.Pause : IconType.Play
          }));
          break;
      }
    };

    window.addEventListener('keydown', handleKeyDown);
    return () => window.removeEventListener('keydown', handleKeyDown);
  }, [handleNextVideo, handlePrevVideo]);

  return {
    currentIndex,
    swiperState,
    setSwiperState,
    handleNextVideo,
    handlePrevVideo,
    isNavigating
  };
};

export const EnhancedVideoFeedContainer: React.FC<VideoFeedProps> = ({
  videos,
  onLoadMore,
  hasMore,
  loading
}) => {
  const {
    currentIndex,
    swiperState,
    handleNextVideo,
    handlePrevVideo,
    isNavigating
  } = useSwiperNavigation({
    videos,
    onVideoChange: (index) => {
      // Handle video change analytics
      trackVideoSwitch({
        fromIndex: currentIndex,
        toIndex: index,
        method: 'swiper_navigation'
      });
    },
    onLoadMore,
    hasMore
  });

  return (
    <div className="relative h-screen overflow-hidden">
      {/* Navigation overlay */}
      <div className="absolute inset-0 z-10 pointer-events-none">
        {/* Previous video trigger area */}
        <button
          className="absolute top-0 left-0 w-full h-1/3 pointer-events-auto opacity-0 hover:opacity-10 bg-gradient-to-b from-black/20 to-transparent transition-opacity"
          onClick={handlePrevVideo}
          disabled={currentIndex === 0 || isNavigating}
          aria-label="Previous video"
        />
        
        {/* Next video trigger area */}
        <button
          className="absolute bottom-0 left-0 w-full h-1/3 pointer-events-auto opacity-0 hover:opacity-10 bg-gradient-to-t from-black/20 to-transparent transition-opacity"
          onClick={handleNextVideo}
          disabled={currentIndex >= videos.length - 1 || isNavigating}
          aria-label="Next video"
        />
      </div>

      {/* Video container with snap scrolling */}
      <div 
        className="h-full overflow-y-auto snap-y snap-mandatory"
        style={{ 
          scrollBehavior: 'smooth',
          scrollSnapType: 'y mandatory'
        }}
      >
        {videos.map((video, index) => (
          <VideoItemContainer
            key={video.id}
            video={video}
            index={index}
            isActive={index === currentIndex}
            swiperState={swiperState}
            onSelect={() => {
              // Handle direct video selection
              if (index !== currentIndex) {
                if (index > currentIndex) {
                  handleNextVideo();
                } else {
                  handlePrevVideo();
                }
              }
            }}
          />
        ))}
      </div>

      {/* Navigation indicators */}
      <div className="absolute right-4 top-1/2 -translate-y-1/2 z-20 flex flex-col space-y-2">
        {videos.slice(Math.max(0, currentIndex - 2), currentIndex + 3).map((_, relativeIndex) => {
          const actualIndex = Math.max(0, currentIndex - 2) + relativeIndex;
          const isActive = actualIndex === currentIndex;
          
          return (
            <div
              key={actualIndex}
              className={`
                w-1 h-8 rounded-full transition-all duration-200
                ${isActive 
                  ? 'bg-white' 
                  : 'bg-white/30 hover:bg-white/50'
                }
              `}
            />
          );
        })}
      </div>
    </div>
  );
};

Complete Comment System Implementation

Enhanced Comment Types

// Complete comment system types
interface CommentSystemState {
  // Video-level comment state
  videoComments: Record<string, VideoCommentState>;
  // Individual comment items
  commentItems: Record<string, CommentItem>;
}

interface VideoCommentState {
  awemeId?: string;
  cursor: string;
  comments: CommentItem[];
  hasMore: boolean;
  loading: boolean;
  isFirstLoad: boolean;
  fetchType: 'load_by_current' | 'preload_by_ml';
  currentAspect: 'all' | string; // Can be topic-specific like 'topic_123'
}

interface CommentItem {
  cid: string;                           // Comment ID
  user: string;                          // User ID who posted
  user_digged: boolean;                  // Whether current user liked this comment
  is_author_digged: boolean;             // Whether video author liked this comment
  digg_count: number;                    // Total likes on this comment
  reply_comment_total: number;           // Total replies count
  reply_comment?: CommentItem[];         // Loaded reply comments
  replyCache?: {                         // Reply pagination cache
    comments: CommentItem[];
    cursor: string;
    hasMore: boolean;
    loading: boolean;
  };
  comment_language?: string;             // Language code for translation
}

// Comment interaction analytics
interface CommentAnalytics {
  comment_id: string;
  group_id: string;                      // Video ID
  comment_user_id: string;               // Comment author ID
  author_id: string;                     // Video author ID
  enter_method: string;                  // How user entered comment section
  parent_comment_id?: string;            // For reply analytics
}

Comment System React Components

// Enhanced comment system with all discovered features
export const CommentSystem: React.FC<{ videoId: string }> = ({ videoId }) => {
  const [commentState, setCommentState] = useState<VideoCommentState>();
  const [selectedAspect, setSelectedAspect] = useState<string>('all');
  const commentService = useCommentService();

  // Load comments when video changes
  useEffect(() => {
    commentService.fetchComment({
      aweme_id: videoId,
      cursor: '0',
      fetch_type: 'load_by_current',
      commentAspect: selectedAspect
    });
  }, [videoId, selectedAspect]);

  return (
    <div className="comment-system">
      {/* Comment aspect filter */}
      <CommentAspectFilter
        currentAspect={selectedAspect}
        onAspectChange={setSelectedAspect}
      />
      
      {/* Comment list */}
      <CommentList
        videoId={videoId}
        comments={commentState?.comments || []}
        onLoadMore={() => commentService.fetchComment({
          aweme_id: videoId,
          cursor: commentState?.cursor || '0'
        })}
      />
    </div>
  );
};

// Individual comment component with reply threading
export const CommentItem: React.FC<{
  comment: CommentItem;
  videoId: string;
  onReply: (commentId: string) => void;
}> = ({ comment, videoId, onReply }) => {
  const [showReplies, setShowReplies] = useState(false);
  const [isLiking, setIsLiking] = useState(false);
  const commentService = useCommentService();

  const handleLike = async () => {
    if (isLiking) return;
    setIsLiking(true);

    try {
      await commentService.handleCommentLike({
        cid: comment.cid,
        itemId: videoId,
        teaAuthorId: comment.user,
        enterMethod: 'comment_panel'
      });
    } finally {
      setIsLiking(false);
    }
  };

  const handleShowMoreReplies = async () => {
    await commentService.handleShowMoreReply({
      itemId: videoId,
      cid: comment.cid
    });
  };

  return (
    <div className="comment-item p-4 border-b border-gray-800">
      {/* Comment header */}
      <div className="flex items-start space-x-3">
        <UserAvatar userId={comment.user} size="sm" />
        
        <div className="flex-1 min-w-0">
          {/* Comment content */}
          <div className="text-white text-sm">
            {comment.text}
          </div>
          
          {/* Comment actions */}
          <div className="flex items-center space-x-4 mt-2 text-gray-400 text-xs">
            <button
              onClick={handleLike}
              disabled={isLiking}
              className={`
                flex items-center space-x-1 hover:text-red-400 transition-colors
                ${comment.user_digged ? 'text-red-500' : ''}
                ${isLiking ? 'opacity-50' : ''}
              `}
            >
              <HeartIcon filled={comment.user_digged} />
              <span>{formatCount(comment.digg_count)}</span>
            </button>

            <button
              onClick={() => onReply(comment.cid)}
              className="hover:text-blue-400 transition-colors"
            >
              Reply
            </button>

            {comment.reply_comment_total > 0 && (
              <button
                onClick={() => setShowReplies(!showReplies)}
                className="hover:text-gray-300 transition-colors"
              >
                {showReplies ? 'Hide' : 'Show'} {comment.reply_comment_total} replies
              </button>
            )}
          </div>
        </div>
      </div>

      {/* Reply thread */}
      {showReplies && (
        <div className="ml-12 mt-4 space-y-3">
          {comment.reply_comment?.map((reply, index) => (
            <CommentReply
              key={reply.cid}
              reply={reply}
              parentId={comment.cid}
              videoId={videoId}
            />
          ))}
          
          {/* Load more replies button */}
          {comment.replyCache?.hasMore && (
            <button
              onClick={handleShowMoreReplies}
              className="text-blue-400 hover:text-blue-300 text-xs transition-colors"
              disabled={comment.replyCache?.loading}
            >
              {comment.replyCache?.loading ? 'Loading...' : 'Show more replies'}
            </button>
          )}
        </div>
      )}
    </div>
  );
};

// Comment aspect filter component
export const CommentAspectFilter: React.FC<{
  currentAspect: string;
  onAspectChange: (aspect: string) => void;
}> = ({ currentAspect, onAspectChange }) => {
  const aspects = [
    { id: 'all', label: 'All Comments' },
    { id: 'topic_trending', label: 'Trending' },
    { id: 'topic_recent', label: 'Recent' }
  ];

  return (
    <div className="flex space-x-2 p-4 border-b border-gray-800">
      {aspects.map(aspect => (
        <button
          key={aspect.id}
          onClick={() => onAspectChange(aspect.id)}
          className={`
            px-3 py-1 rounded-full text-sm transition-colors
            ${currentAspect === aspect.id
              ? 'bg-blue-600 text-white'
              : 'bg-gray-700 text-gray-300 hover:bg-gray-600'
            }
          `}
        >
          {aspect.label}
        </button>
      ))}
    </div>
  );
};

Comment Preloading Service

// ML-driven comment preloading system
export class CommentPreloadService {
  private preloadedComments = new Map<string, VideoCommentState>();
  private preloadQueue: string[] = [];

  /**
   * Preload comments for upcoming videos using ML predictions
   */
  async preloadCommentsForVideo(
    videoId: string, 
    fetchType: 'preload_by_ml' | 'load_by_current' = 'preload_by_ml'
  ): Promise<void> {
    if (this.preloadedComments.has(videoId)) return;

    try {
      const response = await this.fetchComments({
        aweme_id: videoId,
        cursor: '0',
        count: 20,
        fetch_type: fetchType
      });

      if (response.status_code === 0 && response.comments?.length) {
        const processedData = this.processCommentData(response.comments);
        
        const commentState: VideoCommentState = {
          awemeId: videoId,
          cursor: response.cursor || '0',
          comments: processedData.comments,
          hasMore: !!response.has_more,
          loading: false,
          isFirstLoad: true,
          fetchType,
          currentAspect: 'all'
        };

        // Cache preloaded comments
        this.preloadedComments.set(videoId, commentState);
        this.preloadQueue.push(videoId);

        // Update global state
        this.updateCommentState(videoId, commentState);
        this.updateUserData(processedData.users);

        // Track preload analytics
        this.trackCommentPreload({
          group_id: videoId,
          comment_count: processedData.comments.length,
          fetch_type: fetchType
        });
      }
    } catch (error) {
      console.error(`Failed to preload comments for video ${videoId}:`, error);
    }
  }

  /**
   * Get preloaded comments for a video
   */
  getPreloadedComments(videoId: string): VideoCommentState | null {
    return this.preloadedComments.get(videoId) || null;
  }

  /**
   * Clean up old preloaded comments
   */
  cleanupOldPreloads(currentVideoIndex: number, keepDistance: number = 10) {
    const videosToKeep = new Set<string>();
    
    // Keep comments for videos within distance
    for (let i = Math.max(0, currentVideoIndex - keepDistance); 
         i < currentVideoIndex + keepDistance; i++) {
      if (this.preloadQueue[i]) {
        videosToKeep.add(this.preloadQueue[i]);
      }
    }

    // Remove comments outside keep range
    this.preloadedComments.forEach((_, videoId) => {
      if (!videosToKeep.has(videoId)) {
        this.preloadedComments.delete(videoId);
      }
    });

    this.preloadQueue = this.preloadQueue.filter(id => videosToKeep.has(id));
  }
}

Core Utility System

Utility Bundle Analysis (`3813.1e571ef0.js`)

The utility bundle provides essential infrastructure for TikTok's web application:

1. Invariant Error Handling

// Core error checking utility used throughout TikTok's codebase
interface InvariantFunction {
  (condition: boolean, message?: string, ...args: any[]): void;
}

// Usage in TikTok's code
invariant(videoId, 'Video ID is required for playback');
invariant(userPermissions.canView, 'User %s does not have permission to view video %s', userId, videoId);

2. Dynamic Script Loading

// Advanced script loading with comprehensive options
interface ScriptLoadOptions {
  type?: string;           // Script type (default: 'text/javascript')
  charset?: string;        // Character encoding (default: 'utf8')
  async?: boolean;         // Async loading (default: true)
  attrs?: Record<string, string>; // Custom attributes
  text?: string;           // Inline script content
}

interface ScriptLoader {
  (src: string, options?: ScriptLoadOptions, callback?: (error: Error | null, element: HTMLScriptElement) => void): void;
}

// TikTok uses this for:
// - Loading video player chunks on demand
// - Dynamic feature loading based on user interactions
// - A/B testing script injection
// - Analytics and tracking script management

3. PropTypes Validation System

// React component validation (development mode)
interface PropTypesSystem {
  array: PropTypeValidator;
  bool: PropTypeValidator;
  func: PropTypeValidator;
  number: PropTypeValidator;
  object: PropTypeValidator;
  string: PropTypeValidator;
  symbol: PropTypeValidator;
  any: PropTypeValidator;
  arrayOf: (validator: PropTypeValidator) => PropTypeValidator;
  element: PropTypeValidator;
  instanceOf: (constructor: Function) => PropTypeValidator;
  node: PropTypeValidator;
  objectOf: (validator: PropTypeValidator) => PropTypeValidator;
  oneOf: (values: any[]) => PropTypeValidator;
  oneOfType: (validators: PropTypeValidator[]) => PropTypeValidator;
  shape: (shape: Record<string, PropTypeValidator>) => PropTypeValidator;
  exact: (shape: Record<string, PropTypeValidator>) => PropTypeValidator;
}

Utility Integration in Video Player

// Example of how utilities integrate with video player components
import { invariant } from './utils/invariant';
import { loadScript } from './utils/scriptLoader';

export const VideoPlayerWithUtilities: React.FC<VideoPlayerProps> = ({ videoId, onLoad }) => {
  const [playerReady, setPlayerReady] = useState(false);
  
  useEffect(() => {
    // Validate required props
    invariant(videoId, 'VideoPlayer requires a valid videoId');
    
    // Dynamically load video player engine
    loadScript('/static/js/video-engine.js', {
      async: true,
      attrs: { 'data-video-id': videoId }
    }, (error, script) => {
      if (error) {
        console.error('Failed to load video engine:', error);
        return;
      }
      
      setPlayerReady(true);
      onLoad?.(videoId);
    });
  }, [videoId, onLoad]);

  return (
    <div className="video-player-container">
      {playerReady ? (
        <VideoEngine videoId={videoId} />
      ) : (
        <VideoPlayerSkeleton />
      )}
    </div>
  );
};

// PropTypes validation for development
VideoPlayerWithUtilities.propTypes = {
  videoId: PropTypes.string.isRequired,
  onLoad: PropTypes.func,
  autoplay: PropTypes.bool,
  controls: PropTypes.bool,
  muted: PropTypes.bool
};

Error Handling Strategy

// TikTok's comprehensive error handling approach
class VideoPlayerErrorHandler {
  /**
   * Handle video loading errors with graceful degradation
   */
  static handleVideoError(error: Error, videoId: string, retryCount: number = 0): void {
    // Use invariant for critical errors
    invariant(retryCount < 3, 'Video loading failed after %s retries for video %s', retryCount, videoId);
    
    // Log error for analytics
    this.logError({
      type: 'video_load_error',
      videoId,
      error: error.message,
      retryCount,
      timestamp: Date.now()
    });
    
    // Attempt recovery strategies
    if (retryCount < 2) {
      // Try alternative video source
      this.loadAlternativeSource(videoId, retryCount + 1);
    } else {
      // Show error state to user
      this.showErrorState(videoId, error);
    }
  }
  
  /**
   * Dynamic loading of error recovery modules
   */
  static async loadErrorRecovery(): Promise<void> {
    return new Promise((resolve, reject) => {
      loadScript('/static/js/error-recovery.js', {
        async: true,
        attrs: { 'data-module': 'error-recovery' }
      }, (error) => {
        if (error) {
          reject(error);
        } else {
          resolve();
        }
      });
    });
  }
}

Performance Optimization Utilities

// Advanced performance utilities discovered in the bundle
interface PerformanceUtils {
  // Throttle function calls for scroll events
  throttle: <T extends (...args: any[]) => any>(func: T, delay: number) => T;
  
  // Debounce function calls for search inputs
  debounce: <T extends (...args: any[]) => any>(func: T, delay: number) => T;
  
  // Lazy loading with intersection observer
  lazyLoad: (element: HTMLElement, callback: () => void) => void;
  
  // Memory management for large lists
  virtualizeList: (items: any[], containerHeight: number, itemHeight: number) => any[];
}

// Implementation examples
export const usePerformanceOptimizedScroll = (onScroll: () => void) => {
  const throttledScroll = useMemo(
    () => throttle(onScroll, 16), // 60fps
    [onScroll]
  );
  
  useEffect(() => {
    window.addEventListener('scroll', throttledScroll, { passive: true });
    return () => window.removeEventListener('scroll', throttledScroll);
  }, [throttledScroll]);
};

Privacy and Network Security (PNS) System

Core Security Architecture (`index.js`)

The index.js file reveals TikTok's comprehensive Privacy and Network Security (PNS) system - a sophisticated privacy compliance and security framework:

1. Privacy Compliance Engine

// Cookie consent management with domain-based blocking
interface CookieConsentManager {
  blockedCookies: string[];           // Cookies to block based on domain
  hookCookieSetter: () => void;       // Intercept document.cookie operations
  processCookieSet: (value: string) => CookieData;
}

interface CookieData {
  rawValue: string;
  name: string;
  _time: number;
  _blocked: boolean;
  _sample_rate: number;
  _stack_rate: number;
  _rule_names: string[];
}

// Usage in TikTok's privacy system
const cookieManager = new CookieConsentManager({
  blockers: [{
    domains: ["tiktok.com", "tiktokv.com"],
    cookies: ["MONITOR_WEB_ID", "MONITOR_DEVICE_ID", "ktlvDW7IG5ClOcxYTbmY"]
  }],
  sampleRate: 0.07
});

2. Network Request Interception

// Comprehensive network security with request/response monitoring
interface NetworkInterceptor {
  originalFetch: typeof fetch;
  originalXHR: typeof XMLHttpRequest;
  
  hookFetch: () => void;              // Intercept fetch API
  hookXMLHttpRequest: () => void;     // Intercept XHR requests
  applySecurityRules: (data: RequestData) => ProcessedRequestData;
}

interface RequestData {
  request_url: string;
  request_host: string;
  request_path: string;
  method: string;
  headers: Record<string, string>;
  _request_time: number;
  _blocked: boolean;
  _sample_rate: number;
}

// Security rules applied to every request
interface SecurityRule {
  conditions: Array<{
    type: 'url' | 'host' | 'path' | 'header' | 'method';
    pattern: {
      $eq?: string;
      $prefix?: string;
      $regex?: string;
      $in?: string[];
    };
  }>;
  handlers: Array<{
    handler: 'block' | 'report' | 'replace';
    type: 'self' | 'url' | 'header';
    value?: any;
  }>;
  priority: number;
  ruleName: string;
}

3. Web API Monitoring

// Monitor sensitive API usage for privacy compliance
interface WebAPIMonitor {
  hookSensitiveAPIs: () => void;
  hookAPI: (config: APIConfig) => void;
}

interface APIConfig {
  apiName: string;                    // API method name
  apiObj: string;                     // Object path (e.g., "navigator.geolocation")
  apiType: 'method' | 'constructor' | 'attribute_get' | 'attribute_set';
  block: boolean;                     // Whether to block the API
  sampleRate: number;                 // Sampling rate for reporting
  stackRate: number;                  // Stack trace collection rate
  withRawArguments: boolean[];        // Which arguments to log
  withStack: boolean;                 // Whether to collect stack traces
}

// Examples of monitored APIs
const monitoredAPIs = [
  {
    apiName: "getUserMedia",
    apiObj: "navigator.mediaDevices",
    apiType: "method",
    sampleRate: 1.0,
    stackRate: 1.0,
    block: false
  },
  {
    apiName: "getCurrentPosition", 
    apiObj: "navigator.geolocation",
    apiType: "method",
    sampleRate: 1.0,
    stackRate: 1.0,
    block: false
  },
  {
    apiName: "cookie",
    apiObj: "document",
    apiType: "attribute_get",
    sampleRate: 0.00005,
    stackRate: 0.001,
    block: false
  }
];

4. Page Context Management

// Track navigation and page context changes
interface PageContextManager {
  observers: Array<{
    func: (context: PageContext) => void;
    fields?: string[];
  }>;
  context: PageContext;
  
  buildInitialContext: () => PageContext;
  setupNavigationTracking: () => void;
  updateContext: (newContext: PageContext) => void;
}

interface PageContext {
  url: string;
  host: string;
  path: string;
  search: string;
  hash: string;
  region: string;                     // Geographic region
  business: string;                   // Business context
  env: 'prod' | 'dev' | 'staging';   // Environment
  gtm?: string;                       // Google Tag Manager status
  ftc?: string;                       // FTC compliance status
  login?: string;                     // Login status
}

5. Service Worker Communication

// Secure communication with service worker for enhanced privacy
interface ServiceWorkerCommunication {
  SW_EVENTS: {
    RUNTIME_SW_EVENT: "__PNS_RUNTIME_SW_EVENT__";
    RUNTIME_SE_ERROR: "__PNS_RUNTIME_SE_ERROR__";
    RUNTIME: "__PNS_RUNTIME__";
  };
  
  setupCommunication: (runtime: PNSRuntime) => void;
  sendConfigToSW: (config: PNSConfig) => void;
  handleSWMessages: (event: MessageEvent) => void;
}

Integration with Video Player System

The PNS system directly impacts video player functionality:

// Enhanced video player with PNS integration
export const PrivacyAwareVideoPlayer: React.FC<VideoPlayerProps> = ({ 
  videoId, 
  onLoad,
  requiresConsent = true 
}) => {
  const [consentGranted, setConsentGranted] = useState(false);
  const [pnsBlocked, setPnsBlocked] = useState(false);
  
  useEffect(() => {
    // Check PNS consent status
    const runtime = window.__PNS_RUNTIME__;
    if (runtime) {
      // Monitor for privacy-related blocks
      runtime.addObserver((context) => {
        if (context.cookie_ga !== true && requiresConsent) {
          setPnsBlocked(true);
        }
      }, ['cookie_ga', 'cookie_fbp', 'cookie_optional']);
    }
  }, [requiresConsent]);

  // Handle video loading with privacy compliance
  const loadVideo = useCallback(async () => {
    if (pnsBlocked) {
      console.warn('Video loading blocked by privacy policy');
      return;
    }
    
    try {
      // Video loading with PNS monitoring
      const response = await fetch(`/api/video/${videoId}`, {
        headers: {
          'X-Privacy-Consent': consentGranted ? '1' : '0'
        }
      });
      
      if (response.status === 410) {
        // Request blocked by PNS
        setPnsBlocked(true);
        return;
      }
      
      const videoData = await response.json();
      onLoad?.(videoData);
      
    } catch (error) {
      console.error('Video loading failed:', error);
    }
  }, [videoId, consentGranted, pnsBlocked, onLoad]);

  if (pnsBlocked) {
    return (
      <div className="video-blocked-notice">
        <p>Video unavailable due to privacy settings</p>
        <button onClick={() => setConsentGranted(true)}>
          Grant Consent
        </button>
      </div>
    );
  }

  return (
    <VideoPlayer 
      videoId={videoId}
      onLoad={loadVideo}
      privacyCompliant={true}
    />
  );
};

PNS Configuration Example

// Complete PNS configuration as used by TikTok
const pnsConfig: PNSConfig = {
  cookie: {
    enabled: true,
    sampleRate: 0.07,
    stackSampleRate: 0.07,
    blockers: [{
      domains: ["tiktok.com", "tiktokv.com"],
      cookies: ["MONITOR_WEB_ID", "MONITOR_DEVICE_ID", "ktlvDW7IG5ClOcxYTbmY"]
    }]
  },
  
  network: {
    sampleRate: 0.03,
    intercept: [
      {
        // Force HTTPS
        conditions: [{ 
          type: "url", 
          pattern: { $prefix: "http://" } 
        }],
        handlers: [{ 
          handler: "replace", 
          type: "url", 
          pattern: { $prefix: "http://" },
          value: "https://" 
        }],
        priority: -1000,
        ruleName: "force_https"
      },
      {
        // Block YouTube API on TikTok
        conditions: [
          { type: "url", pattern: { $prefix: "https://www.youtube.com/iframe_api" } },
          { type: "context", field: "host", pattern: { $eq: "www.tiktok.com" } }
        ],
        handlers: [{ handler: "block", type: "self" }],
        priority: 22,
        ruleName: "youtube_cutoff"
      }
    ]
  },
  
  webapi: {
    enabled: true,
    apis: [
      {
        apiName: "getUserMedia",
        apiObj: "navigator.mediaDevices", 
        apiType: "method",
        sampleRate: 1.0,
        stackRate: 1.0,
        withRawArguments: [true],
        withStack: true
      }
    ]
  }
};

This enhanced implementation now includes TikTok's complete privacy and security infrastructure alongside the sophisticated video player system, providing comprehensive replication of their privacy-compliant video feed mechanics.

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