import bcfetch from 'bandcamp-fetch';
import fs from 'fs/promises'; // Using the promise-based version of fs for clean async/await

const username = 'noschxl';

async function fetchEntireWishlist() {
  let previousWishlist = [];
  
  // 1. Try to load the previous wishlist to compare against
  try {
    const fileData = await fs.readFile('wishlist.json', 'utf8');
    previousWishlist = JSON.parse(fileData);
    console.log(`Loaded ${previousWishlist.length} previous items from wishlist.json for comparison.`);
  } catch (error) {
    if (error.code === 'ENOENT') {
      console.log('No existing wishlist.json found. This must be the first run!');
    } else {
      console.error('Error reading wishlist.json:', error);
    }
  }

  let allWishlistItems = [];
  let currentParams = {
    target: username,
    imageFormat: 'art_app_large'
  };

  let hasMorePages = true;
  let pageCount = 1;

  console.log(`\nStarting wishlist scrape for user: ${username}...`);

  // 2. Scrape the current wishlist
  while (hasMorePages) {
    console.log(`Fetching page ${pageCount}...`);
    
    try {
      const result = await bcfetch.fan.getWishlist(currentParams);

      if (result && result.items) {
        allWishlistItems.push(...result.items);
      }

      if (result.continuation) {
        currentParams.target = result.continuation;
        pageCount++;
      } else {
        hasMorePages = false;
      }
    } catch (error) {
      console.error(`Error fetching page ${pageCount}:`, error);
      break; 
    }
  }

  console.log(`\nDone! Successfully scraped ${allWishlistItems.length} items from your wishlist.`);
  
  // 3. Compare the old list against the new list
  if (previousWishlist.length > 0) {
    // Create a Set of all the current IDs for fast, easy lookup
    const currentIds = new Set(allWishlistItems.map(item => item.id));

    // Filter the previous list to find items whose IDs are missing from the current scrape
    const missingItems = previousWishlist.filter(item => !currentIds.has(item.id));

    if (missingItems.length > 0) {
      console.log(`\nWARNING: ${missingItems.length} item(s) have disappeared since the last run!`);
      
      missingItems.forEach(item => {
        console.log(`- ${item.artist.name} : ${item.name}`);
        console.log(`  Old URL: ${item.url}\n`);
      });

      // Optional: Save the missing items to a separate file so you don't lose their metadata
      await fs.writeFile('missing_items.json', JSON.stringify(missingItems, null, 2));
      console.log('Saved missing items to missing_items.json');
    } else {
      console.log('\nAll good! No items have disappeared since your last run.');
    }
  }

  // 4. Overwrite wishlist.json with the new, up-to-date data for the next run
  try {
    await fs.writeFile('wishlist.json', JSON.stringify(allWishlistItems, null, 2));
    console.log('Successfully updated wishlist.json with current data.');
  } catch (error) {
    console.error('Error writing to wishlist.json:', error);
  }
}

fetchEntireWishlist();