require('dotenv').config();
const express = require('express');
const multer = require('multer');
const cors = require('cors');
const path = require('path');
const fs = require('fs');
const pdfParse = require('pdf-parse');
const pptxParser = require('pptx-parser');
const { GoogleGenerativeAI } = require('@google/generative-ai');

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

// Middleware
app.use(cors());
app.use(express.json());
app.use(express.static('public'));

// Configure multer for file upload
const storage = multer.diskStorage({
  destination: function (req, file, cb) {
    const uploadDir = 'uploads';
    if (!fs.existsSync(uploadDir)) {
      fs.mkdirSync(uploadDir);
    }
    cb(null, uploadDir);
  },
  filename: function (req, file, cb) {
    cb(null, Date.now() + path.extname(file.originalname));
  }
});

const upload = multer({
  storage: storage,
  fileFilter: function (req, file, cb) {
    const allowedTypes = ['.pdf', '.pptx'];
    const ext = path.extname(file.originalname).toLowerCase();
    if (allowedTypes.includes(ext)) {
      cb(null, true);
    } else {
      cb(new Error('Only PDF and PPTX files are allowed'));
    }
  }
});

// Initialize Gemini AI
const genAI = new GoogleGenerativeAI(process.env.GEMINI_API_KEY);

// Extract text from PDF
async function extractTextFromPDF(filePath) {
  const dataBuffer = fs.readFileSync(filePath);
  const data = await pdfParse(dataBuffer);
  return data.text;
}

// Extract text from PPTX
async function extractTextFromPPTX(filePath) {
  const result = await pptxParser.parseFile(filePath);
  let text = '';
  result.slides.forEach(slide => {
    text += slide.text + '\n';
  });
  return text;
}

// Generate notes using Gemini AI
async function generateNotes(text) {
  const model = genAI.getGenerativeModel({ model: 'gemini-pro' });
  const prompt = `Please create well-structured, comprehensive notes from the following content. Include main points, key concepts, and important details:\n\n${text}`;
  
  const result = await model.generateContent(prompt);
  const response = await result.response;
  return response.text();
}

// File upload and processing endpoint
app.post('/upload', upload.single('file'), async (req, res) => {
  try {
    if (!req.file) {
      return res.status(400).json({ error: 'No file uploaded' });
    }

    const filePath = req.file.path;
    const fileExt = path.extname(req.file.originalname).toLowerCase();
    
    let extractedText = '';
    if (fileExt === '.pdf') {
      extractedText = await extractTextFromPDF(filePath);
    } else if (fileExt === '.pptx') {
      extractedText = await extractTextFromPPTX(filePath);
    }

    const notes = await generateNotes(extractedText);

    // Clean up uploaded file
    fs.unlinkSync(filePath);

    res.json({ notes });
  } catch (error) {
    console.error('Error processing file:', error);
    res.status(500).json({ error: 'Error processing file' });
  }
});

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