import re

INVALID_PASSWORD_MESSAGE = 'Invalid password, password must be at least ' + \
                           '8 characters and contain no whitespace.'

def validate_email(email_address):
  if re.match(r'[^@]+@[^@]+\.[^@]+', email_address):
    return True
  return False


def validate_username(username):
  # Based off the restrictions defined in the Docker Registry API spec
  regex_match = (re.search(r'[^a-z0-9_]', username) is None)
  if not regex_match:
    return (False, 'Username must match expression [a-z0-9_]+')

  length_match = (len(username) >= 4 and len(username) <= 30)
  if not length_match:
    return (False, 'Username must be between 4 and 30 characters in length')

  return (True, '')


def validate_password(password):
  # No whitespace and minimum length of 8
  if re.search(r'\s', password):
    return False
  return len(password) > 7