server.js

const express = require('express');
const multer = require('multer');
const pdf = require('pdf-parse');
const { OpenAI } = require('openai');
require('dotenv').config();
const path = require('path');
const session = require('express-session');

const app = express();
const upload = multer({ dest: 'uploads/' });

const openai = new OpenAI({
  apiKey: process.env.OPENAI_API_KEY
});

app.use(express.json());
app.use(express.static(path.join(__dirname, '/')));
app.use(session({
    secret: 'your-secret-key',
    resave: false,
    saveUninitialized: true
}));

app.get('/', (req, res) => {
    res.sendFile(path.join(__dirname, 'index.html'));
});

// Upload endpoint
app.post('/upload', upload.single('pdf'), async (req, res) => {
  try {
    const dataBuffer = fs.readFileSync(req.file.path);
    const data = await pdf(dataBuffer);
    
    // Store the PDF text in memory (or database for production)
    req.session.pdfText = data.text;
    
    res.json({ message: 'PDF uploaded and processed successfully' });
  } catch (error) {
    res.status(500).json({ error: error.message });
  }
});

// Question answering endpoint
app.post('/ask', async (req, res) => {
  try {
    const { question } = req.body;
    const pdfText = req.session.pdfText;
    
    if (!pdfText) {
      return res.status(400).json({ error: 'Please upload a PDF first' });
    }

    const completion = await openai.chat.completions.create({
      model: "gpt-3.5-turbo",
      messages: [
        {
          role: "system",
          content: "You are a helpful assistant that answers questions based on the provided PDF content."
        },
        {
          role: "user",
          content: `Context from PDF: ${pdfText}\n\nQuestion: ${question}`
        }
      ],
      max_tokens: 500
    });

    res.json({ answer: completion.choices[0].message.content });
  } catch (error) {
    res.status(500).json({ error: error.message });
  }
});

const PORT = process.env.PORT || 3000;
app.listen(PORT, () => {
  console.log(`Server running on port ${PORT}`);
});