index.js

const express = require("express");
const multer = require("multer");
const { GoogleGenerativeAI } = require("@google/generative-ai");
require("dotenv").config(); // For loading environment variables from a .env file

const app = express();
const port = process.env.PORT || 3000;

// Middleware to parse JSON bodies
app.use(express.json());

// Check if the API key is available
if (!process.env.GOOGLE_GENERATIVE_AI_KEY) {
  console.error("Google Generative AI API key is missing");
  process.exit(1);
}

// Initialize the Google Generative AI with the API key from environment variables
const genAI = new GoogleGenerativeAI(process.env.GOOGLE_GENERATIVE_AI_KEY);

// Configure multer for handling form-data (including file uploads)
const upload = multer({
  limits: { fileSize: 10 * 1024 * 1024 }, // 10 MB limit
  fileFilter: (req, file, cb) => {
    const allowedTypes = ['image/jpeg', 'image/png', 'application/pdf'];
    if (allowedTypes.includes(file.mimetype)) {
      cb(null, true);
    } else {
      cb(new Error('Invalid file type'), false);
    }
  }
});

// Converts file information to a GoogleGenerativeAI.Part object
function fileToGenerativePart(file) {
  return {
    inlineData: {
      data: file.buffer.toString("base64"),
      mimeType: file.mimetype,
    },
  };
}

// POST endpoint to read a file (image or PDF)
app.post("/read-file", upload.single("file"), async (req, res) => {
  try {
    const file = req.file;
    if (!file) {
      return res.status(400).json({ error: "File is required" });
    }

    const prompt = "What's in this file? Explain in 10 points.";
    const model = genAI.getGenerativeModel({ model: "gemini-1.5-flash" });

    const filePart = fileToGenerativePart(file);
    const result = await model.generateContent([prompt, filePart]);

    const response = await result.response;
    const text = await response.text();

    res.json({ generatedText: text });
  } catch (error) {
    console.error("Error generating content:", error);
    res.status(500).json({ error: "An error occurred while generating content", details: error.message });
  }
});

// Error handling middleware for Multer
app.use((err, req, res, next) => {
  if (err instanceof multer.MulterError) {
    return res.status(400).json({ error: err.message });
  }
  next(err);
});

app.listen(port, () => {
  console.log(`Server is running on port ${port}`);
});