import logging
import itertools
import json
import uuid

import features

from data import model
from data.users.database import DatabaseUsers
from data.users.externalldap import LDAPUsers
from data.users.externaljwt import ExternalJWTAuthN
from data.users.keystone import get_keystone_users
from util.security.aes import AESCipher

logger = logging.getLogger(__name__)

def get_federated_service_name(authentication_type):
  if authentication_type == 'LDAP':
    return 'ldap'

  if authentication_type == 'JWT':
    return 'jwtauthn'

  if authentication_type == 'Keystone':
    return 'keystone'

  raise Exception('Unknown auth type: %s' % authentication_type)


LDAP_CERT_FILENAME = 'ldap.crt'

def get_users_handler(config, _, override_config_dir):
  """ Returns a users handler for the authentication configured in the given config object. """
  authentication_type = config.get('AUTHENTICATION_TYPE', 'Database')

  if authentication_type == 'Database':
    return DatabaseUsers()

  if authentication_type == 'LDAP':
    ldap_uri = config.get('LDAP_URI', 'ldap://localhost')
    base_dn = config.get('LDAP_BASE_DN')
    admin_dn = config.get('LDAP_ADMIN_DN')
    admin_passwd = config.get('LDAP_ADMIN_PASSWD')
    user_rdn = config.get('LDAP_USER_RDN', [])
    uid_attr = config.get('LDAP_UID_ATTR', 'uid')
    email_attr = config.get('LDAP_EMAIL_ATTR', 'mail')
    secondary_user_rdns = config.get('LDAP_SECONDARY_USER_RDNS', [])
    timeout = config.get('LDAP_TIMEOUT')
    network_timeout = config.get('LDAP_NETWORK_TIMEOUT')

    allow_tls_fallback = config.get('LDAP_ALLOW_INSECURE_FALLBACK', False)
    return LDAPUsers(ldap_uri, base_dn, admin_dn, admin_passwd, user_rdn, uid_attr, email_attr,
                     allow_tls_fallback, secondary_user_rdns=secondary_user_rdns,
                     requires_email=features.MAILING, timeout=timeout,
                     network_timeout=network_timeout)

  if authentication_type == 'JWT':
    verify_url = config.get('JWT_VERIFY_ENDPOINT')
    issuer = config.get('JWT_AUTH_ISSUER')
    max_fresh_s = config.get('JWT_AUTH_MAX_FRESH_S', 300)

    query_url = config.get('JWT_QUERY_ENDPOINT', None)
    getuser_url = config.get('JWT_GETUSER_ENDPOINT', None)

    return ExternalJWTAuthN(verify_url, query_url, getuser_url, issuer, override_config_dir,
                            config['HTTPCLIENT'], max_fresh_s,
                            requires_email=features.MAILING)

  if authentication_type == 'Keystone':
    auth_url = config.get('KEYSTONE_AUTH_URL')
    auth_version = int(config.get('KEYSTONE_AUTH_VERSION', 2))
    timeout = config.get('KEYSTONE_AUTH_TIMEOUT')
    keystone_admin_username = config.get('KEYSTONE_ADMIN_USERNAME')
    keystone_admin_password = config.get('KEYSTONE_ADMIN_PASSWORD')
    keystone_admin_tenant = config.get('KEYSTONE_ADMIN_TENANT')
    return get_keystone_users(auth_version, auth_url, keystone_admin_username,
                             keystone_admin_password, keystone_admin_tenant, timeout,
                             requires_email=features.MAILING)

  raise RuntimeError('Unknown authentication type: %s' % authentication_type)

class UserAuthentication(object):
  def __init__(self, app=None, config_provider=None, override_config_dir=None):
    self.app_secret_key = None
    self.app = app
    if app is not None:
      self.state = self.init_app(app, config_provider, override_config_dir)
    else:
      self.state = None

  def init_app(self, app, config_provider, override_config_dir):
    self.app_secret_key = app.config['SECRET_KEY']
    users = get_users_handler(app.config, config_provider, override_config_dir)

    # register extension with app
    app.extensions = getattr(app, 'extensions', {})
    app.extensions['authentication'] = users

    return users

  def _get_secret_key(self):
    """ Returns the secret key to use for encrypting and decrypting. """
    secret_key = None

    # First try parsing the key as an int.
    try:
      big_int = int(self.app_secret_key)
      secret_key = str(bytearray.fromhex('{:02x}'.format(big_int)))
    except ValueError:
      pass

    # Next try parsing it as an UUID.
    if secret_key is None:
      try:
        secret_key = uuid.UUID(self.app_secret_key).bytes
      except ValueError:
        pass

    if secret_key is None:
      secret_key = str(bytearray(map(ord, self.app_secret_key)))

    # Otherwise, use the bytes directly.
    return ''.join(itertools.islice(itertools.cycle(secret_key), 32))

  def encrypt_user_password(self, password):
    """ Returns an encrypted version of the user's password. """
    data = {
      'password': password
    }

    message = json.dumps(data)
    cipher = AESCipher(self._get_secret_key())
    return cipher.encrypt(message)

  def _decrypt_user_password(self, encrypted):
    """ Attempts to decrypt the given password and returns it. """
    cipher = AESCipher(self._get_secret_key())

    try:
      message = cipher.decrypt(encrypted)
    except ValueError:
      return None
    except TypeError:
      return None

    try:
      data = json.loads(message)
    except ValueError:
      return None

    return data.get('password', encrypted)

  def ping(self):
    """ Returns whether the authentication engine is reachable and working. """
    return self.state.ping()

  @property
  def federated_service(self):
    """ Returns the name of the federated service for the auth system. If none, should return None.
    """
    return self.state.federated_service

  def query_users(self, query, limit=20):
    """ Performs a lookup against the user system for the specified query. The returned tuple
        will be of the form (results, federated_login_id, err_msg). If the method is unsupported,
        the results portion of the tuple will be None instead of empty list.

        Note that this method can and will return results for users not yet found within the
        database; it is the responsibility of the caller to call link_user if they need the
        database row for the user system record.

        Results will be in the form of objects's with username and email fields.
    """
    return self.state.query_users(query, limit)

  def link_user(self, username_or_email):
    """ Returns a tuple containing the database user record linked to the given username/email
        and any error that occurred when trying to link the user.
    """
    return self.state.link_user(username_or_email)

  def get_and_link_federated_user_info(self, user_info):
    """ Returns a tuple containing the database user record linked to the given UserInformation
        pair and any error that occurred when trying to link the user.
    """
    return self.state.get_and_link_federated_user_info(user_info)

  def confirm_existing_user(self, username, password):
    """ Verifies that the given password matches to the given DB username. Unlike
        verify_credentials, this call first translates the DB user via the FederatedLogin table
        (where applicable).
    """
    return self.state.confirm_existing_user(username, password)

  def verify_credentials(self, username_or_email, password):
    """ Verifies that the given username and password credentials are valid. """
    return self.state.verify_credentials(username_or_email, password)

  def check_group_lookup_args(self, group_lookup_args):
    """ Verifies that the given group lookup args point to a valid group. Returns a tuple consisting
        of a boolean status and an error message (if any).
    """
    return self.state.check_group_lookup_args(group_lookup_args)

  def service_metadata(self):
    """ Returns a dictionary of extra metadata to present to *superusers* about this auth engine.
        For example, LDAP returns the base DN so we can display to the user during sync setup.
    """
    return self.state.service_metadata()

  def iterate_group_members(self, group_lookup_args, page_size=None, disable_pagination=False):
    """ Returns a tuple of an iterator over all the members of the group matching the given lookup
        args dictionary, or the error that occurred if the initial call failed or is unsupported.
        The format of the lookup args dictionary is specific to the implementation.
        Each result in the iterator is a tuple of (UserInformation, error_message), and only
        one will be not-None.
    """
    return self.state.iterate_group_members(group_lookup_args, page_size=page_size,
                                            disable_pagination=disable_pagination)

  def verify_and_link_user(self, username_or_email, password, basic_auth=False):
    """ Verifies that the given username and password credentials are valid and, if so,
        creates or links the database user to the federated identity. """
    # First try to decode the password as a signed token.
    if basic_auth:
      decrypted = self._decrypt_user_password(password)
      if decrypted is None:
        # This is a normal password.
        if features.REQUIRE_ENCRYPTED_BASIC_AUTH:
          msg = ('Client login with unencrypted passwords is disabled. Please generate an ' +
                 'encrypted password in the user admin panel for use here.')
          return (None, msg)
      else:
        password = decrypted

    (result, err_msg) = self.state.verify_and_link_user(username_or_email, password)
    if not result:
      return (result, err_msg)

    if not result.enabled:
      return (None, 'This user has been disabled. Please contact your administrator.')

    return (result, err_msg)

  def __getattr__(self, name):
    return getattr(self.state, name, None)