import fs from 'fs';
import path from 'path';
import { cache } from '@/utils/cache';

export interface BlogPost {
  slug: string;
  title: string;
  date: string;
  excerpt: string;
  coverImage: string;
  category?: string;
  tags?: string[];
  content?: string;
}

const BLOG_POSTS_DIR = path.join(process.cwd(), 'blog-posts');

// Category mapping based on filename patterns
const categoryMap: Record<string, string> = {
  'agentic': 'KI-Agenten',
  'ai-agent': 'KI-Agenten',
  'deepseek': 'KI-Entwicklung',
  'openai': 'KI-Entwicklung',
  'gpt': 'KI-Entwicklung',
  'claude': 'KI-Entwicklung',
  'langchain': 'KI-Entwicklung',
  'langgraph': 'KI-Entwicklung',
  'rag': 'KI-Entwicklung',
  'llm': 'KI-Entwicklung',
  'voice': 'Voice AI',
  'vapi': 'Voice AI',
  'speech': 'Voice AI',
  'elevenlabs': 'Voice AI',
  'whisper': 'Voice AI',
  'n8n': 'Automatisierung',
  'make': 'Automatisierung',
  'zapier': 'Automatisierung',
  'automation': 'Automatisierung',
  'workflow': 'Automatisierung',
  'scraping': 'Web Scraping',
  'playwright': 'Web Scraping',
  'puppeteer': 'Web Scraping',
  'nextjs': 'Web Development',
  'react': 'Web Development',
  'typescript': 'Web Development',
  'api': 'Backend',
  'database': 'Backend',
  'postgres': 'Backend',
  'prisma': 'Backend',
  'supabase': 'Backend',
  'saas': 'SaaS',
  'stripe': 'SaaS',
  'subscription': 'SaaS',
  'seo': 'SEO',
  'performance': 'Performance',
  'iot': 'IoT',
  'raspberry': 'IoT',
  'mqtt': 'IoT',
  'home-assistant': 'Smart Home',
};

function detectCategory(filename: string, content: string): string {
  const lowerFilename = filename.toLowerCase();
  const lowerContent = content.toLowerCase().slice(0, 500);

  for (const [keyword, category] of Object.entries(categoryMap)) {
    if (lowerFilename.includes(keyword) || lowerContent.includes(keyword)) {
      return category;
    }
  }
  return 'Technologie';
}

function parseMarkdownPost(filename: string, content: string): BlogPost | null {
  try {
    // Extract title from first H1
    const titleMatch = content.match(/^#\s+(.+)$/m);
    const title = titleMatch ? titleMatch[1].trim() : filename.replace(/\.md$/, '');

    // Extract meta description
    const metaMatch = content.match(/\*\*Meta-Description:\*\*\s*(.+)/i);
    const metaDescription = metaMatch ? metaMatch[1].trim() : '';

    // Extract keywords
    const keywordsMatch = content.match(/\*\*Keywords?:\*\*\s*(.+)/i);
    const keywordsStr = keywordsMatch ? keywordsMatch[1].trim() : '';
    const tags = keywordsStr ? keywordsStr.split(',').map(k => k.trim()).slice(0, 6) : [];

    // Extract excerpt from introduction or meta description
    let excerpt = metaDescription;
    if (!excerpt) {
      const introMatch = content.match(/## Einführung\s*\n\n([\s\S]+?)(?:\n\n|$)/);
      if (introMatch) {
        excerpt = introMatch[1].trim().slice(0, 200) + '...';
      }
    }

    // Generate slug from filename (remove number prefix)
    const slug = filename
      .replace(/\.md$/, '')
      .replace(/^\d+-/, '');

    // Extract date from filename number (approximate)
    const numMatch = filename.match(/^(\d+)-/);
    const postNum = numMatch ? parseInt(numMatch[1], 10) : 1;
    // Generate dates starting from 2026-01-19 going backwards
    const baseDate = new Date('2026-01-19');
    baseDate.setDate(baseDate.getDate() - (postNum - 1));
    const date = baseDate.toISOString().split('T')[0];

    // Detect category
    const category = detectCategory(filename, content);

    // Cover image path
    const coverImage = `/images/posts/${slug}/cover.jpg`;

    return {
      slug,
      title,
      date,
      excerpt: excerpt || title,
      coverImage,
      category,
      tags,
      content,
    };
  } catch (error) {
    console.error(`Error parsing ${filename}:`, error);
    return null;
  }
}

export function getAllBlogPosts(): BlogPost[] {
  const cacheKey = 'blog:all-posts';

  // Check cache first
  const cachedPosts = cache.get<BlogPost[]>(cacheKey);
  if (cachedPosts) {
    return cachedPosts;
  }

  if (!fs.existsSync(BLOG_POSTS_DIR)) {
    console.warn('Blog posts directory not found:', BLOG_POSTS_DIR);
    return [];
  }

  const files = fs.readdirSync(BLOG_POSTS_DIR)
    .filter(file => file.endsWith('.md'))
    .sort();

  const posts: BlogPost[] = [];

  for (const file of files) {
    try {
      const filePath = path.join(BLOG_POSTS_DIR, file);
      const content = fs.readFileSync(filePath, 'utf-8');
      const post = parseMarkdownPost(file, content);
      if (post) {
        posts.push(post);
      }
    } catch (error) {
      // Skip files that fail to parse
      console.warn(`Failed to parse blog post: ${file}`, error);
      continue;
    }
  }

  // Sort by date descending (newest first)
  const sortedPosts = posts.sort((a, b) => new Date(b.date).getTime() - new Date(a.date).getTime());

  // Cache the results
  cache.set(cacheKey, sortedPosts);

  return sortedPosts;
}

export function getBlogPostBySlug(slug: string): BlogPost | null {
  const posts = getAllBlogPosts();
  return posts.find(post => post.slug === slug) || null;
}

export function getBlogPostSlugs(): string[] {
  return getAllBlogPosts().map(post => post.slug);
}