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

// Parse JSON requests
app.use(express.json());

// Regular route
app.get('/', (req, res) => {
  res.send('Welcome to the error handling demo. Try visiting /error-demo to see error handling in action.');
});

// Route that deliberately throws an error
app.get('/error-demo', (req, res, next) => {
  try {
    // Simulate an error
    throw new Error('Something went wrong!');
  } catch (error) {
    next(error); // Pass error to the error handler
  }
});

// Route with async error
app.get('/async-error', async (req, res, next) => {
  try {
    // Simulate an async error
    await simulateAsyncError();
  } catch (error) {
    next(error);
  }
});

// Error-handling middleware (must have 4 parameters)
app.use((err, req, res, next) => {
  console.error('Error occurred:', err.stack);
  
  // Send a formatted error response
  res.status(500).json({
    message: 'An error occurred',
    error: process.env.NODE_ENV === 'production' ? {} : {
      name: err.name,
      message: err.message,
      stack: err.stack
    }
  });
});

// Helper function to simulate async error
async function simulateAsyncError() {
  return new Promise((resolve, reject) => {
    setTimeout(() => {
      reject(new Error('Async operation failed'));
    }, 100);
  });
}

// Start the server
const PORT = 8080;
app.listen(PORT, () => {
  console.log(`Server running on port ${PORT}`);
  
  // Simulate requests for demonstration
  console.log('Simulating requests:');
  
  // Simulate normal request
  console.log('\nRequest to home route:');
  console.log('GET /');
  console.log('Response: Welcome to the error handling demo. Try visiting /error-demo to see error handling in action.');
  
  // Simulate error request
  console.log('\nRequest to error route:');
  console.log('GET /error-demo');
  console.error('Error occurred: Error: Something went wrong!');
  console.log('Response:');
  console.log(JSON.stringify({
    message: 'An error occurred',
    error: {
      name: 'Error',
      message: 'Something went wrong!',
      stack: 'Error: Something went wrong! at ...'
    }
  }, null, 2));
});