Node.js Express API Proxy for External Services

const express = require('express');
const axios = require('axios'); // A promise-based HTTP client for the browser and node.js
const dotenv = require('dotenv');

dotenv.config(); // Load environment variables from .env file

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

// Middleware to parse JSON bodies
app.use(express.json());

// Example proxy endpoint for a public API (e.g., GitHub API)
// This endpoint fetches user data from GitHub
app.get('/api/github/user/:username', async (req, res) => {
  const { username } = req.params;
  try {
    const response = await axios.get(`https://api.github.com/users/${username}`, {
      headers: {
        // If GitHub required an API key, it would be passed here
        // Authorization: `token ${process.env.GITHUB_API_TOKEN}`
      }
    });
    res.json(response.data);
  } catch (error) {
    console.error('Error fetching GitHub user:', error.message);
    if (error.response) {
      res.status(error.response.status).json(error.response.data);
    } else {
      res.status(500).json({ message: 'Internal Server Error' });
    }
  }
});

// Example proxy endpoint requiring a secret API key (e.g., a hypothetical weather API)
app.get('/api/weather/:city', async (req, res) => {
  const { city } = req.params;
  const WEATHER_API_KEY = process.env.WEATHER_API_KEY; // Stored securely in .env

  if (!WEATHER_API_KEY) {
    return res.status(500).json({ message: 'Weather API key not configured.' });
  }

  try {
    const response = await axios.get(`https://api.example.com/weather?city=${city}&apiKey=${WEATHER_API_KEY}`);
    res.json(response.data);
  } catch (error) {
    console.error('Error fetching weather:', error.message);
    if (error.response) {
      res.status(error.response.status).json(error.response.data);
    } else {
      res.status(500).json({ message: 'Internal Server Error' });
    }
  }
});

app.listen(PORT, () => {
  console.log(`Proxy server listening on port ${PORT}`);
});