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 KeystoneUsers

from util.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)


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

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

    authentication_type = app.config.get('AUTHENTICATION_TYPE', 'Database')

    if authentication_type == 'Database':
      users = DatabaseUsers()
    elif authentication_type == 'LDAP':
      ldap_uri = app.config.get('LDAP_URI', 'ldap://localhost')
      base_dn = app.config.get('LDAP_BASE_DN')
      admin_dn = app.config.get('LDAP_ADMIN_DN')
      admin_passwd = app.config.get('LDAP_ADMIN_PASSWD')
      user_rdn = app.config.get('LDAP_USER_RDN', [])
      uid_attr = app.config.get('LDAP_UID_ATTR', 'uid')
      email_attr = app.config.get('LDAP_EMAIL_ATTR', 'mail')

      users = LDAPUsers(ldap_uri, base_dn, admin_dn, admin_passwd, user_rdn, uid_attr, email_attr)
    elif authentication_type == 'JWT':
      verify_url = app.config.get('JWT_VERIFY_ENDPOINT')
      issuer = app.config.get('JWT_AUTH_ISSUER')
      max_fresh_s = app.config.get('JWT_AUTH_MAX_FRESH_S', 300)
      users = ExternalJWTAuthN(verify_url, issuer, override_config_dir,
                               app.config['HTTPCLIENT'], max_fresh_s)
    elif authentication_type == 'Keystone':
      auth_url = app.config.get('KEYSTONE_AUTH_URL')
      keystone_admin_username = app.config.get('KEYSTONE_ADMIN_USERNAME')
      keystone_admin_password = app.config.get('KEYSTONE_ADMIN_PASSWORD')
      keystone_admin_tenant = app.config.get('KEYSTONE_ADMIN_TENANT')
      users = KeystoneUsers(auth_url, keystone_admin_username, keystone_admin_password,
                            keystone_admin_tenant)
    else:
      raise RuntimeError('Unknown authentication type: %s' % authentication_type)

    # 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 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 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)