const util = require('util');
const fs = require('fs');

// Convert callbacks to promises
const readFile = util.promisify(fs.readFile);

// Function with a nested chain of async operations
async function processUserData(userId) {
  try {
    console.log(`Processing data for user ${userId}...`);
    
    // Fetch user data
    const userData = await fetchUserData(userId);
    console.log(`User data retrieved: ${userData.name}`);

    // Get user posts
    const posts = await getUserPosts(userId);
    console.log(`Retrieved ${posts.length} posts for user`);

    // Process posts (this will cause an error for userId = 3)
    const processedPosts = posts.map(post => {
      return {
        id: post.id,
        title: post.title.toUpperCase(),
        contentLength: post.content.length, // Will fail if content is undefined
      };
    });
    return { user: userData, posts: processedPosts };
   } catch (error) {
    console.error('Error processing user data:', error);
    throw error;
  }
}

// Simulated API call
function fetchUserData(userId) {
  return new Promise((resolve, reject) => {
    setTimeout(() => {
      if (userId <= 0) {
        reject(new Error('Invalid user ID'));
      } else {
        resolve({ id: userId, name: `User ${userId}` });
      }
    }, 500);
  });
}

// Simulated database query
function getUserPosts(userId) {
  return new Promise((resolve) => {
    setTimeout(() => {
      // Bug: post with undefined content for userId 3
      if (userId === 3) {
        resolve([
          { id: 1, title: 'First Post', content: 'Content' },
          { id: 2, title: 'Second Post', content: undefined }
        ]);
      } else {
        resolve([
          { id: 1, title: 'First Post', content: 'Content' },
          { id: 2, title: 'Second Post', content: 'More content' }
        ]);
      }
    }, 300);
  });
}

// Usage
processUserData(3).catch(err => console.log('Caught at top level:', err.message));