"""
Provide authentication using Django Web Framework

:depends:   - Django Web Framework

Django authentication depends on the presence of the django framework in the
``PYTHONPATH``, the Django project's ``settings.py`` file being in the
``PYTHONPATH`` and accessible via the ``DJANGO_SETTINGS_MODULE`` environment
variable.

Django auth can be defined like any other eauth module:

.. code-block:: yaml

    external_auth:
      django:
        fred:
          - .*
          - '@runner'

This will authenticate Fred via Django and allow him to run any execution
module and all runners.

The authorization details can optionally be located inside the Django database.
The relevant entry in the ``models.py`` file would look like this:

.. code-block:: python

    class SaltExternalAuthModel(models.Model):
        user_fk = models.ForeignKey(User, on_delete=models.CASCADE)
        minion_or_fn_matcher = models.CharField(max_length=255)
        minion_fn = models.CharField(max_length=255)

The :conf_master:`external_auth` clause in the master config would then look
like this:

.. code-block:: yaml

    external_auth:
      django:
        ^model: <fully-qualified reference to model class>

When a user attempts to authenticate via Django, Salt will import the package
indicated via the keyword ``^model``.  That model must have the fields
indicated above, though the model DOES NOT have to be named
'SaltExternalAuthModel'.
"""

import logging
import os
import sys

# pylint: disable=import-error
try:
    import django
    from django.db import connection  # pylint: disable=no-name-in-module

    HAS_DJANGO = True
except Exception as exc:  # pylint: disable=broad-except
    # If Django is installed and is not detected, uncomment
    # the following line to display additional information
    # log.warning('Could not load Django auth module. Found exception: %s', exc)
    HAS_DJANGO = False
# pylint: enable=import-error

DJANGO_AUTH_CLASS = None

log = logging.getLogger(__name__)

__virtualname__ = "django"


def __virtual__():
    if HAS_DJANGO:
        return __virtualname__
    return False


def is_connection_usable():
    try:
        connection.connection.ping()
    except Exception:  # pylint: disable=broad-except
        return False
    else:
        return True


def __django_auth_setup():
    """
    Prepare the connection to the Django authentication framework
    """
    if django.VERSION >= (1, 7):
        django.setup()

    global DJANGO_AUTH_CLASS

    if DJANGO_AUTH_CLASS is not None:
        return

    # Versions 1.7 and later of Django don't pull models until
    # they are needed.  When using framework facilities outside the
    # web application container we need to run django.setup() to
    # get the model definitions cached.
    if "^model" in __opts__["external_auth"]["django"]:
        django_model_fullname = __opts__["external_auth"]["django"]["^model"]
        django_model_name = django_model_fullname.split(".")[-1]
        django_module_name = ".".join(django_model_fullname.split(".")[0:-1])

        # pylint: disable=possibly-unused-variable
        django_auth_module = __import__(
            django_module_name, globals(), locals(), "SaltExternalAuthModel"
        )
        # pylint: enable=possibly-unused-variable
        DJANGO_AUTH_CLASS_str = f"django_auth_module.{django_model_name}"
        DJANGO_AUTH_CLASS = eval(DJANGO_AUTH_CLASS_str)  # pylint: disable=W0123


def auth(username, password):
    """
    Simple Django auth
    """
    django_auth_path = __opts__["django_auth_path"]
    if django_auth_path not in sys.path:
        sys.path.append(django_auth_path)
    os.environ.setdefault("DJANGO_SETTINGS_MODULE", __opts__["django_auth_settings"])

    __django_auth_setup()

    if not is_connection_usable():
        connection.close()

    import django.contrib.auth  # pylint: disable=import-error,3rd-party-module-not-gated,no-name-in-module

    user = django.contrib.auth.authenticate(username=username, password=password)
    if user is not None:
        if user.is_active:
            log.debug("Django authentication successful")
            return True
        else:
            log.debug(
                "Django authentication: the password is valid but the account is disabled."
            )
    else:
        log.debug("Django authentication failed.")

    return False


def acl(username):
    """

    :param username: Username to filter for
    :return: Dictionary that can be slotted into the ``__opts__`` structure for
        eauth that designates the user associated ACL

    Database records such as:

    ===========  ====================     =========
    username     minion_or_fn_matcher     minion_fn
    ===========  ====================     =========
    fred                                  test.ping
    fred         server1                  network.interfaces
    fred         server1                  raid.list
    fred         server2                  .*
    guru         .*
    smartadmin   server1                  .*
    ===========  ====================     =========

    Should result in an eauth config such as:

    .. code-block:: yaml

        fred:
          - test.ping
          - server1:
              - network.interfaces
              - raid.list
          - server2:
              - .*
        guru:
          - .*
        smartadmin:
          - server1:
            - .*

    """
    __django_auth_setup()

    if username is None:
        db_records = DJANGO_AUTH_CLASS.objects.all()
    else:
        db_records = DJANGO_AUTH_CLASS.objects.filter(user_fk__username=username)
    auth_dict = {}

    for a in db_records:
        if a.user_fk.username not in auth_dict:
            auth_dict[a.user_fk.username] = []

        if not a.minion_or_fn_matcher and a.minion_fn:
            auth_dict[a.user_fk.username].append(a.minion_fn)
        elif a.minion_or_fn_matcher and not a.minion_fn:
            auth_dict[a.user_fk.username].append(a.minion_or_fn_matcher)
        else:
            found = False
            for d in auth_dict[a.user_fk.username]:
                if isinstance(d, dict):
                    if a.minion_or_fn_matcher in d:
                        auth_dict[a.user_fk.username][a.minion_or_fn_matcher].append(
                            a.minion_fn
                        )
                        found = True
            if not found:
                auth_dict[a.user_fk.username].append(
                    {a.minion_or_fn_matcher: [a.minion_fn]}
                )

    log.debug("django auth_dict is %s", auth_dict)
    return auth_dict
