OAuth permission decorator code snippet from WakaTime blog post

oauth_example_decorator.py

""" Example for Blog Post:
https://wakatime.com/blog/34-part-3-flask-api-decorators-and-helpers
"""

def oauth(required_scopes=[]):
    def wrapper(func):
        @wraps(func)
        def inner(*args, **kwargs):

            # don't check oauth tokens if user already logged in with session cookie
            if current_app.current_user.is_authenticated:
                return func(*args, **kwargs)

            grant = load_oauth_grant_from_request(request)
            if grant is None:
                return login_manager.unauthorized()

            missing = get_missing_scopes(grant=grant, required_scopes=required_scopes)
            if len(missing) > 0:
                return jsonify(error=u'This resource requires scopes: {0}.'.format(missing)), 403

            if not flask_login.login_user(grant.user):
                return login_manager.unauthorized()
            del session['user_id']

            return func(*args, **kwargs)
        return inner
    return wrapper