import fs from 'fs';
import path from 'path';
import matter from 'gray-matter';

export interface PostFrontmatter {
  title: string;
  date: string;
  excerpt?: string;
  featuredImage?: string | null;
  category?: string;
  locale: string;
}

export interface PostMdx {
  slug: string;
  frontmatter: PostFrontmatter;
  content: string;
}

export async function getPostBySlug(slug: string, locale: string): Promise<PostMdx | null> {
  const postsDir = path.join(process.cwd(), 'data', 'blog', locale);
  const filePath = path.join(postsDir, `${slug}.mdx`);

  if (!fs.existsSync(filePath)) {
    return null;
  }

  const fileContent = fs.readFileSync(filePath, 'utf8');
  const { data, content } = matter(fileContent);

  return {
    slug,
    frontmatter: data as PostFrontmatter,
    content,
  };
}

export async function getAllPosts(locale: string): Promise<PostMdx[]> {
  const postsDir = path.join(process.cwd(), 'data', 'blog', locale);
  if (!fs.existsSync(postsDir)) return [];
  
  const files = fs.readdirSync(postsDir);
  const posts = files
    .filter(file => file.endsWith('.mdx'))
    .map(file => {
      const filePath = path.join(postsDir, file);
      const fileContent = fs.readFileSync(filePath, 'utf8');
      const { data, content } = matter(fileContent);
      return {
        slug: file.replace(/\.mdx$/, ''),
        frontmatter: data as PostFrontmatter,
        content,
      };
    })
    .sort((a, b) => new Date(b.frontmatter.date).getTime() - new Date(a.frontmatter.date).getTime());

  return posts;
}

export async function getAdjacentPosts(slug: string, locale: string): Promise<{ prev: PostMdx | null; next: PostMdx | null }> {
  const posts = await getAllPosts(locale);
  const currentIndex = posts.findIndex(post => post.slug === slug);

  if (currentIndex === -1) {
    return { prev: null, next: null };
  }

  // Posts are sorted by date descending (newest first)
  // So "next" post (newer) is at index - 1
  // And "previous" post (older) is at index + 1
  const next = currentIndex > 0 ? posts[currentIndex - 1] : null;
  const prev = currentIndex < posts.length - 1 ? posts[currentIndex + 1] : null;

  return { prev, next };
}