ContentLoader.js

/**
 * ContentLoader.js - Progressive content loading system for enhanced NewsCards
 * Handles lazy loading, content caching, and progressive disclosure
 */

export class ContentLoader {
  constructor() {
    this.cache = new Map();
    this.loadingQueue = new Map();
    this.config = {
      cacheTimeout: 300000, // 5 minutes
      maxCacheSize: 100,
      loadTimeout: 10000, // 10 seconds
      retryAttempts: 3
    };
  }
  
  // Load enhanced content for a news item
  async loadEnhancedContent(newsData) {
    const cacheKey = this.generateCacheKey(newsData);
    
    // Check cache first
    if (this.cache.has(cacheKey)) {
      const cached = this.cache.get(cacheKey);
      if (Date.now() - cached.timestamp < this.config.cacheTimeout) {
        return cached.content;
      } else {
        this.cache.delete(cacheKey);
      }
    }
    
    // Check if already loading
    if (this.loadingQueue.has(cacheKey)) {
      return this.loadingQueue.get(cacheKey);
    }
    
    // Start loading
    const loadPromise = this.performContentLoad(newsData);
    this.loadingQueue.set(cacheKey, loadPromise);
    
    try {
      const content = await loadPromise;
      
      // Cache the result
      this.cacheContent(cacheKey, content);
      this.loadingQueue.delete(cacheKey);
      
      return content;
    } catch (error) {
      this.loadingQueue.delete(cacheKey);
      throw error;
    }
  }
  
  // Perform the actual content loading
  async performContentLoad(newsData) {
    const enhancedContent = {
      ...newsData,
      fullDescription: '',
      author: '',
      publishedDate: new Date(),
      readingTime: 0,
      tags: [],
      relatedArticles: [],
      socialMetrics: {
        shares: 0,
        likes: 0,
        comments: 0
      },
      mediaElements: {
        images: [],
        videos: [],
        audio: null
      },
      contentSummary: '',
      keyPoints: [],
      sources: []
    };
    
    // Simulate API calls for different content types
    try {
      // Load basic enhanced content
      const basicContent = await this.loadBasicContent(newsData);
      Object.assign(enhancedContent, basicContent);
      
      // Load media content
      const mediaContent = await this.loadMediaContent(newsData);
      enhancedContent.mediaElements = mediaContent;
      
      // Load social metrics
      const socialData = await this.loadSocialMetrics(newsData);
      enhancedContent.socialMetrics = socialData;
      
      // Load related content
      const relatedContent = await this.loadRelatedContent(newsData);
      enhancedContent.relatedArticles = relatedContent;
      
      return enhancedContent;
      
    } catch (error) {
      console.warn('Content loading failed, using fallback:', error);
      return this.getFallbackContent(newsData);
    }
  }
  
  // Load basic enhanced content
  async loadBasicContent(newsData) {
    return new Promise((resolve) => {
      // Simulate API delay
      setTimeout(() => {
        resolve({
          fullDescription: this.generateDescription(newsData.headline),
          author: this.generateAuthor(),
          publishedDate: new Date(Date.now() - Math.random() * 86400000 * 7), // Random date within week
          readingTime: Math.floor(Math.random() * 10) + 2,
          contentSummary: this.generateSummary(newsData.headline),
          keyPoints: this.generateKeyPoints(newsData.headline),
          sources: this.generateSources()
        });
      }, Math.random() * 500 + 200);
    });
  }
  
  // Load media content (images, videos)
  async loadMediaContent(newsData) {
    return new Promise((resolve) => {
      setTimeout(() => {
        const mediaElements = {
          images: this.generateImageGallery(newsData),
          videos: this.generateVideoContent(newsData),
          audio: null
        };
        resolve(mediaElements);
      }, Math.random() * 800 + 300);
    });
  }
  
  // Load social metrics
  async loadSocialMetrics(newsData) {
    return new Promise((resolve) => {
      setTimeout(() => {
        resolve({
          shares: Math.floor(Math.random() * 5000),
          likes: Math.floor(Math.random() * 15000),
          comments: Math.floor(Math.random() * 1000)
        });
      }, Math.random() * 400 + 100);
    });
  }
  
  // Load related articles
  async loadRelatedContent(newsData) {
    return new Promise((resolve) => {
      setTimeout(() => {
        const relatedCount = Math.floor(Math.random() * 5) + 2;
        const related = [];
        
        for (let i = 0; i < relatedCount; i++) {
          related.push({
            id: `related-${i}`,
            headline: this.generateRelatedHeadline(newsData.category),
            image: this.generateRelatedImage(),
            publishedDate: new Date(Date.now() - Math.random() * 86400000 * 3),
            source: this.generateSource()
          });
        }
        
        resolve(related);
      }, Math.random() * 600 + 200);
    });
  }
  
  // Generate content based on headline and category
  generateDescription(headline) {
    const templates = [
      `This breaking story about ${headline.toLowerCase()} has significant implications for the region. Local authorities are monitoring the situation closely as developments continue to unfold.`,
      `In a major development, ${headline.toLowerCase()} has captured international attention. Experts believe this could mark a turning point in ongoing discussions.`,
      `The situation regarding ${headline.toLowerCase()} continues to evolve rapidly. Stakeholders from multiple sectors are weighing in on the potential impacts.`,
      `Latest reports on ${headline.toLowerCase()} suggest broader implications than initially anticipated. Analysis from field experts provides crucial context.`
    ];
    
    return templates[Math.floor(Math.random() * templates.length)];
  }
  
  generateAuthor() {
    const authors = [
      'Sarah Chen', 'Michael Rodriguez', 'Emma Thompson', 'David Kim',
      'Lisa Anderson', 'James Wilson', 'Maria Garcia', 'Robert Taylor',
      'Jennifer Lee', 'Thomas Brown', 'Amanda Davis', 'Christopher Miller'
    ];
    
    return authors[Math.floor(Math.random() * authors.length)];
  }
  
  generateSummary(headline) {
    return `Key developments in ${headline.toLowerCase()} reveal important trends that could influence future decisions and policy directions.`;
  }
  
  generateKeyPoints(headline) {
    const basePoints = [
      'Situation developing rapidly',
      'Multiple stakeholders involved',
      'Regional impact expected',
      'Expert analysis pending'
    ];
    
    const categoryPoints = {
      'Technology': ['Innovation breakthrough', 'Market disruption potential', 'Industry adoption timeline'],
      'Science': ['Research methodology sound', 'Peer review process ongoing', 'Applications being explored'],
      'Politics': ['Policy implications significant', 'Bipartisan support questioned', 'Implementation timeline unclear'],
      'Environment': ['Environmental impact assessment', 'Sustainability concerns raised', 'Long-term monitoring planned'],
      'Business': ['Market reaction positive', 'Investor confidence stable', 'Competition response awaited'],
      'Culture': ['Community engagement high', 'Cultural significance recognized', 'Traditional values respected'],
      'Sports': ['Performance metrics impressive', 'Fan reaction enthusiastic', 'Season implications considered'],
      'Health': ['Clinical trials planned', 'Safety protocols established', 'Public health impact studied']
    };
    
    return basePoints.concat(categoryPoints[Math.random() > 0.5 ? 'Technology' : 'Science'] || []).slice(0, 4);
  }
  
  generateSources() {
    const sources = [
      'Reuters International', 'Associated Press', 'BBC News',
      'CNN World', 'The Guardian', 'Al Jazeera',
      'NPR News', 'Deutsche Welle', 'France24'
    ];
    
    return sources.slice(0, Math.floor(Math.random() * 3) + 1);
  }
  
  generateImageGallery(newsData) {
    const images = [];
    const imageCount = Math.floor(Math.random() * 4) + 2;
    
    for (let i = 0; i < imageCount; i++) {
      images.push({
        url: `data:image/svg+xml;base64,${this.generateImagePlaceholder(i)}`,
        caption: `Image ${i + 1} related to ${newsData.headline}`,
        credit: 'Stock Photography'
      });
    }
    
    return images;
  }
  
  generateVideoContent(newsData) {
    // For now, return placeholder video data
    // In production, this would fetch actual video URLs
    if (Math.random() > 0.7) { // 30% chance of having video
      return [{
        url: this.generateVideoPlaceholder(),
        thumbnail: newsData.image,
        duration: Math.floor(Math.random() * 180) + 30, // 30-210 seconds
        title: `Video: ${newsData.headline}`
      }];
    }
    return [];
  }
  
  generateRelatedHeadline(category) {
    const templates = {
      'Technology': ['AI Breakthrough Changes Industry', 'New Tech Startup Raises $50M', 'Cybersecurity Alert Issued'],
      'Science': ['Climate Study Reveals Findings', 'Medical Research Shows Promise', 'Space Mission Launches Successfully'],
      'Politics': ['Policy Changes Announced', 'Election Results Analyzed', 'International Summit Planned'],
      'Business': ['Market Trends Shift Direction', 'Company Reports Record Profits', 'Economic Indicators Rise'],
      'Environment': ['Conservation Efforts Expand', 'Renewable Energy Milestone', 'Climate Action Accelerates'],
      'Culture': ['Festival Celebrates Heritage', 'Art Exhibition Opens Doors', 'Cultural Exchange Program'],
      'Sports': ['Championship Game Tonight', 'Athlete Breaks World Record', 'Team Trades Star Player'],
      'Health': ['New Treatment Available', 'Health Study Published', 'Medical Device Approved']
    };
    
    const categoryTemplates = templates[category] || templates['Technology'];
    return categoryTemplates[Math.floor(Math.random() * categoryTemplates.length)];
  }
  
  generateRelatedImage() {
    const colors = ['ff6b6b', '4ecdc4', '45b7d1', '96ceb4', 'ffeaa7', 'dda0dd', 'ff9ff3', 'b8860b'];
    const color = colors[Math.floor(Math.random() * colors.length)];
    
    return `data:image/svg+xml;base64,${btoa(`
      <svg width="200" height="150" xmlns="http://www.w3.org/2000/svg">
        <rect width="100%" height="100%" fill="#${color}"/>
        <text x="50%" y="50%" text-anchor="middle" dy=".3em" fill="white" font-family="Arial" font-size="12">Related</text>
      </svg>
    `)}`;
  }
  
  generateSource() {
    const sources = ['Reuters', 'AP', 'BBC', 'CNN', 'Guardian', 'Times', 'Post', 'Tribune'];
    return sources[Math.floor(Math.random() * sources.length)];
  }
  
  generateImagePlaceholder(index) {
    const colors = ['3498db', 'e74c3c', '2ecc71', 'f39c12', '9b59b6', '1abc9c', 'e67e22', '34495e'];
    const color = colors[index % colors.length];
    
    return btoa(`
      <svg width="400" height="300" xmlns="http://www.w3.org/2000/svg">
        <defs>
          <linearGradient id="grad${index}" x1="0%" y1="0%" x2="100%" y2="100%">
            <stop offset="0%" style="stop-color:#${color};stop-opacity:1" />
            <stop offset="100%" style="stop-color:#${color}88;stop-opacity:1" />
          </linearGradient>
        </defs>
        <rect width="100%" height="100%" fill="url(#grad${index})"/>
        <text x="50%" y="50%" text-anchor="middle" dy=".3em" fill="white" font-family="Arial, sans-serif" font-size="18">Gallery ${index + 1}</text>
      </svg>
    `);
  }
  
  generateVideoPlaceholder() {
    // Return a placeholder video URL - in production this would be real video content
    return 'data:video/mp4;base64,'; // Placeholder
  }
  
  // Get fallback content for failed loads
  getFallbackContent(newsData) {
    return {
      ...newsData,
      fullDescription: `More details about ${newsData.headline} are currently being gathered. Please check back later for updates.`,
      author: 'News Staff',
      publishedDate: new Date(),
      readingTime: 2,
      tags: [newsData.category || 'News'],
      relatedArticles: [],
      socialMetrics: { shares: 0, likes: 0, comments: 0 },
      mediaElements: { images: [], videos: [], audio: null },
      contentSummary: newsData.headline,
      keyPoints: ['Story developing', 'Updates coming'],
      sources: ['Local News']
    };
  }
  
  // Generate cache key for content
  generateCacheKey(newsData) {
    return `${newsData.id || newsData.headline}_${newsData.timestamp || Date.now()}`;
  }
  
  // Cache content with timestamp
  cacheContent(key, content) {
    // Implement LRU cache behavior
    if (this.cache.size >= this.config.maxCacheSize) {
      const firstKey = this.cache.keys().next().value;
      this.cache.delete(firstKey);
    }
    
    this.cache.set(key, {
      content,
      timestamp: Date.now()
    });
  }
  
  // Clear expired cache entries
  cleanupCache() {
    const now = Date.now();
    for (const [key, value] of this.cache.entries()) {
      if (now - value.timestamp > this.config.cacheTimeout) {
        this.cache.delete(key);
      }
    }
  }
  
  // Get cache statistics
  getCacheStats() {
    return {
      size: this.cache.size,
      maxSize: this.config.maxCacheSize,
      loadingQueueSize: this.loadingQueue.size
    };
  }
  
  // Clear all cache
  clearCache() {
    this.cache.clear();
    this.loadingQueue.clear();
  }
}

// Global content loader instance
export const globalContentLoader = new ContentLoader();

// Periodic cache cleanup
setInterval(() => {
  globalContentLoader.cleanupCache();
}, 60000); // Every minute