from functools import wraps
from werkzeug import check_password
# A bunch of your Flask app's code here
# . . .

proxy_user = None

def check_auth(user_id, user_pass):
    """
        Checks database via SQLAlchemy to check if credentials
        are valid. If valid, returns a tuple containing (True,
        User). Otherwise, returns tuple (False, None).
    """
    try:
        user_id = int(user_id)
        user_pass = str(user_pass)
    except:
        return False, None
    loaded_user = User.query.filter_by(id=user_id).first()
    if loaded_user is None:
        return False, None
    # Assuming you use werkzeug to hash your passwords
    ret_boolean = check_password(str(loaded_user.pwdhash), user_pass)
    return ret_boolean, loaded_user

def requires_auth(f):
    """
        Decorator for methods to enforce authorization before
        proceding to the wrapped function. Sets a global
        proxy_user object to the current authorized user.
    """
    # Wrapped function has access to proxy_user
    @wraps(f)
    def decorated(*args, **kwargs):
        global proxy_user #declaration required to look up to global scope
        auth = request.authorization
        if not auth:
            return needAuthentication()
        authenticated, proxy_user = check_auth(auth.username, auth.password)
        if not authenticated:
            return needAuthentication(msg='Authentication failed.')
        return f(*args, **kwargs)
    return decorated

@app.route("/greet")
@requires_auth
def greet():
    global proxy_user
    return "Hello, %r" % proxy_user.name