index.js

const functions = require('@google-cloud/functions-framework');
const { Storage } = require('@google-cloud/storage');
const sharp = require('sharp');
const path = require('path');

const storage = new Storage();

// Register a CloudEvent callback
functions.cloudEvent('generateThumbnail', async (cloudEvent) => {
  try {
    // Extract file data from the CloudEvent
    const fileData = cloudEvent.data;
    
    const bucketName = fileData.bucket;
    const filePath = fileData.name; // e.g., "images/photo.jpg"

    console.log("file data:",fileData);
    // 1. Exit if it's not an image
    if (!filePath.startsWith('images/')) {
      console.log(`Skipping non-image file: ${filePath}`);
      return;
    }

    // 2. Exit if it's already a thumbnail (Avoid Infinite Loop!)
    if (path.basename(filePath).startsWith('thumbnails')) {
      console.log('Already a thumbnail, skipping.');
      return;
    }

    console.log(`Processing file: ${filePath} from bucket: ${bucketName}`);

    // Download, resize, and upload logic goes here...
    const bucket = storage.bucket(bucketName);
    const [content] = await bucket.file(filePath).download();
    
    const fileName = path.basename(filePath);

    const [thumbnail, optimised] = await Promise.all([
      sharp(content).resize(400, null).toBuffer(),
      sharp(content).resize(800, null).toBuffer(),
    ]);

    const thumbPath = `thumbnails/${fileName}`;
    const optimisedPath = `optimised/${fileName}`;

    await Promise.all([
      bucket.file(thumbPath).save(thumbnail),
      bucket.file(optimisedPath).save(optimised),
    ]);
    
    console.log(`Thumbnail uploaded to ${thumbPath}`);
    console.log(`Optimised image uploaded to ${optimisedPath}`);
  } catch (error) {
    console.error(`Error processing file: ${error.message}`, error);
    // Don't rethrow - this tells Cloud Run the event was processed
    // preventing automatic retries
  }
});