## django

from django.contrib.auth.models import User
from django.core.validators import email_re

class BasicBackend:
    def get_user(self, user_id):
        try:
            return User.objects.get(pk=user_id)
        except User.DoesNotExist:
            return None

class EmailBackend(BasicBackend):
    def authenticate(self, username=None, password=None):
        #If username is an email address, then try to pull it up
        if email_re.search(username):
            try:
                user = User.objects.get(email=username)
            except User.DoesNotExist:
                return None
        else:
            #We have a non-email address username we should try username
            try:
                user = User.objects.get(username=username)
            except User.DoesNotExist:
                return None
        if user.check_password(password):
            return user

## ruby

class User < ActiveRecord::Base
  EMAIL_REGEX = /..../

  def self.authenticate(username, password)
    user = EMAIL_REGEX.match(username) ? User.find_by_email(username) : User.find_by_username(username)
    return user if user and user.check_password(password) # return user if user exists and user.check_password.. or return nil
  end
end