Content Negotiation

# Content negotiation with Accept header
@app.route('/api/users')
def get_users():
    accept = request.headers.get('Accept', 'application/json')

    # Parse vendor media type
    version = '1'
    if 'vnd.api' in accept:
        # application/vnd.api.v2+json
        match = re.search(r'vnd\.api\.v(\d+)', accept)
        if match:
            version = match.group(1)

    if version == '1':
        data = [{"id": u.id, "name": u.name} for u in users]
        content_type = 'application/vnd.api.v1+json'
    elif version == '2':
        data = [{"id": u.id, "name": u.name, "email": u.email} for u in users]
        content_type = 'application/vnd.api.v2+json'
    else:
        return jsonify({"error": "Unsupported version"}), 400

    response = jsonify(data)
    response.headers['Content-Type'] = content_type
    return response

# Accept header parsing middleware
class ContentNegotiationMiddleware:
    VERSIONS = {
        'application/vnd.api.v1+json': 1,
        'application/vnd.api.v2+json': 2,
    }

    def __init__(self, app):
        self.app = app

    def __call__(self, environ, start_response):
        accept = environ.get('HTTP_ACCEPT', '')
        for media_type, version in self.VERSIONS.items():
            if media_type in accept:
                environ['api.version'] = version
                break
        else:
            environ['api.version'] = 1  # Default
        return self.app(environ, start_response)

// Express content negotiation
app.get('/api/users', (req, res) => {
  const accept = req.headers['accept'] || 'application/json';
  let version = 1;

  if (accept.includes('vnd.api.v2')) {
    version = 2;
  } else if (accept.includes('vnd.api.v1')) {
    version = 1;
  }

  const data = version === 2
    ? users.map(u => ({ id: u.id, name: u.name, email: u.email }))
    : users.map(u => ({ id: u.id, name: u.name }));

  res.set('Content-Type', `application/vnd.api.v${version}+json`);
  res.json(data);
});

# Client usage
curl -H "Accept: application/vnd.api.v1+json" https://api.example.com/users
curl -H "Accept: application/vnd.api.v2+json" https://api.example.com/users