import logging
import features

from collections import namedtuple

from data import model
from util.validation import generate_valid_usernames

logger = logging.getLogger(__name__)

UserInformation = namedtuple('UserInformation', ['username', 'email', 'id'])

class FederatedUsers(object):
  """ Base class for all federated users systems. """

  def __init__(self, federated_service, requires_email):
    self._federated_service = federated_service
    self._requires_email = requires_email

  @property
  def federated_service(self):
    return self._federated_service

  def get_user(self, username_or_email):
    """ Retrieves the user with the given username or email, returning a tuple containing
        a UserInformation (if success) and the error message (on failure).
    """
    raise NotImplementedError

  def verify_credentials(self, username_or_email, password):
    """ Verifies the given credentials against the backing federated service, returning
        a tuple containing a UserInformation (on success) and the error message (on failure).
    """
    raise NotImplementedError

  def query_users(self, query, limit=20):
    """ If implemented, get_user must be implemented as well. """
    return (None, 'Not supported')

  def _get_federated_user(self, username, email):
    db_user = model.user.verify_federated_login(self._federated_service, username)
    if not db_user:
      # We must create the user in our db
      valid_username = None
      for valid_username in generate_valid_usernames(username):
        if model.user.is_username_unique(valid_username):
          break

      if not valid_username:
        logger.error('Unable to pick a username for user: %s', username)
        return (None, 'Unable to pick a username. Please report this to your administrator.')

      prompts = model.user.get_default_user_prompts(features)
      db_user = model.user.create_federated_user(valid_username, email, self._federated_service,
                                                 username,
                                                 set_password_notification=False,
                                                 email_required=self._requires_email,
                                                 prompts=prompts)
    else:
      # Update the db attributes from the federated service.
      if email:
        db_user.email = email
        db_user.save()

    return (db_user, None)

  def link_user(self, username_or_email):
    (credentials, err_msg) = self.get_user(username_or_email)
    if credentials is None:
      return (None, err_msg)

    return self._get_federated_user(credentials.username, credentials.email)

  def verify_and_link_user(self, username_or_email, password):
    """ Verifies the given credentials and, if valid, creates/links a database user to the
        associated federated service.
    """
    (credentials, err_msg) = self.verify_credentials(username_or_email, password)
    if credentials is None:
      return (None, err_msg)

    return self._get_federated_user(credentials.username, credentials.email)

  def confirm_existing_user(self, username, password):
    """ Confirms that the given *database* username and service password are valid for the linked
        service. This method is used when the federated service's username is not known.
    """
    db_user = model.user.get_user(username)
    if not db_user:
      return (None, 'Invalid user')

    federated_login = model.user.lookup_federated_login(db_user, self._federated_service)
    if not federated_login:
      return (None, 'Invalid user')

    (credentials, err_msg) = self.verify_credentials(federated_login.service_ident, password)
    if credentials is None:
      return (None, err_msg)

    return (db_user, None)