mkdir contract-extractor && cd contract-extractor
npm init -y
npm install express multer pdf-parse openai dotenv

# .env
OPENAI_API_KEY=sk-your-key-here
PORT=3000

// src/services/contractService.js
import pdfParse from 'pdf-parse';
import OpenAI from 'openai';

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

const CLAUSE_SCHEMA = `{
  "contractType": "string (e.g. NDA, SaaS Agreement, Employment Contract)",
  "parties": [{ "name": "string", "role": "string (e.g. Vendor, Client)" }],
  "effectiveDate": "string or null",
  "expirationDate": "string or null",
  "autoRenewal": {
    "found": true/false,
    "terms": "string or null",
    "noticePeriod": "string or null"
  },
  "paymentTerms": {
    "found": true/false,
    "amount": "string or null",
    "schedule": "string or null",
    "latePenalty": "string or null"
  },
  "terminationRights": {
    "found": true/false,
    "forCause": "string or null",
    "forConvenience": "string or null",
    "noticePeriod": "string or null"
  },
  "limitationOfLiability": {
    "found": true/false,
    "cap": "string or null",
    "exclusions": ["string"]
  },
  "confidentiality": {
    "found": true/false,
    "duration": "string or null",
    "scope": "string or null"
  },
  "intellectualProperty": {
    "found": true/false,
    "ownership": "string or null"
  },
  "disputeResolution": {
    "found": true/false,
    "method": "string (e.g. arbitration, litigation)",
    "jurisdiction": "string or null"
  },
  "indemnification": {
    "found": true/false,
    "scope": "string or null"
  },
  "riskFlags": [
    {
      "severity": "high/medium/low",
      "clause": "string",
      "description": "string"
    }
  ],
  "missingClauses": ["list of standard clauses not found in this contract"],
  "plainEnglishSummary": "string — 3-4 sentence plain-English summary of key obligations and risks"
}`;

export async function analyzeContract(buffer) {
  const { text } = await pdfParse(buffer);

  if (!text?.trim()) throw new Error('No extractable text in PDF');

  // For long contracts, split and analyze in chunks then synthesize
  const MAX_CHARS = 80_000; // ~20k tokens
  const truncated = text.length > MAX_CHARS ? text.slice(0, MAX_CHARS) + '\n[Document truncated for analysis]' : text;

  const response = await openai.chat.completions.create({
    model: 'gpt-4o',
    messages: [
      {
        role: 'system',
        content: `You are a senior contract attorney with expertise in commercial agreements. 
Analyze the contract below and extract all key clauses.
Return ONLY a JSON object matching this exact schema — no markdown, no explanation:
${CLAUSE_SCHEMA}
Be thorough. Flag any unusual, one-sided, or missing clauses as risk flags.`,
      },
      { role: 'user', content: truncated },
    ],
    temperature: 0.1,
    response_format: { type: 'json_object' },
  });

  return JSON.parse(response.choices[0].message.content);
}

// src/routes/analyze.js
import { Router } from 'express';
import multer from 'multer';
import { analyzeContract } from '../services/contractService.js';

const router = Router();
const upload = multer({ storage: multer.memoryStorage(), limits: { fileSize: 20 * 1024 * 1024 } });

router.post('/', upload.single('contract'), async (req, res, next) => {
  try {
    if (!req.file) return res.status(400).json({ error: 'No contract PDF uploaded' });
    const analysis = await analyzeContract(req.file.buffer);
    res.json({ success: true, filename: req.file.originalname, analysis });
  } catch (err) { next(err); }
});

export default router;

// src/server.js
import 'dotenv/config';
import express from 'express';
import analyzeRouter from './routes/analyze.js';

const app = express();
app.use(express.json());
app.use('/analyze', analyzeRouter);
app.use((err, _req, res, _next) => res.status(500).json({ error: err.message }));
app.listen(process.env.PORT ?? 3000, () => console.log('Contract Extractor running'));

curl -X POST http://localhost:3000/analyze \
  -F "contract=@vendor-agreement.pdf"

{
  "contractType": "SaaS Vendor Agreement",
  "parties": [
    { "name": "Acme Corp", "role": "Vendor" },
    { "name": "Client Inc", "role": "Client" }
  ],
  "autoRenewal": {
    "found": true,
    "terms": "Automatically renews for successive 12-month periods",
    "noticePeriod": "60 days written notice required to cancel"
  },
  "limitationOfLiability": {
    "found": true,
    "cap": "Capped at fees paid in the preceding 3 months",
    "exclusions": ["gross negligence", "wilful misconduct"]
  },
  "riskFlags": [
    {
      "severity": "high",
      "clause": "Limitation of Liability",
      "description": "3-month fee cap is unusually low for a multi-year agreement. Consider negotiating to 12 months."
    },
    {
      "severity": "medium",
      "clause": "Auto-Renewal",
      "description": "60-day cancellation notice required. Calendar a reminder 90 days before renewal date."
    }
  ],
  "missingClauses": ["Force Majeure", "Data Processing Agreement"],
  "plainEnglishSummary": "This is a standard SaaS agreement with an automatic annual renewal. The vendor's liability is capped at just 3 months of fees, which is below industry standard. A Data Processing Agreement (DPA) is missing — required if processing personal data under GDPR."
}

export function generateRiskReport(analysis) {
  const highRisks = analysis.riskFlags.filter(f => f.severity === 'high');
  const html = `
<html><body>
<h1>Contract Risk Report: ${analysis.contractType}</h1>
<h2>High Risk Flags (${highRisks.length})</h2>
${highRisks.map(f => `<div class="risk"><strong>${f.clause}</strong>: ${f.description}</div>`).join('')}
<h2>Missing Clauses</h2>
<ul>${analysis.missingClauses.map(c => `<li>${c}</li>`).join('')}</ul>
<h2>Summary</h2>
<p>${analysis.plainEnglishSummary}</p>
</body></html>`;
  return html;
}