# This file is part of the django-environ.
#
# Copyright (c) 2021-2022, Serghei Iakovlev <egrep@protonmail.ch>
# Copyright (c) 2013-2021, Daniele Faraglia <daniele.faraglia@gmail.com>
#
# For the full copyright and license information, please view
# the LICENSE.txt file that was distributed with this source code.

"""
Django-environ allows you to utilize 12factor inspired environment
variables to configure your Django application.
"""

import ast
import itertools
import logging
import os
import re
import sys
import warnings
from urllib.parse import (
    parse_qs,
    ParseResult,
    unquote,
    unquote_plus,
    urlparse,
    urlunparse,
)

from .compat import (
    DJANGO_POSTGRES,
    ImproperlyConfigured,
    json,
    PYMEMCACHE_DRIVER,
    REDIS_DRIVER,
)
from .fileaware_mapping import FileAwareMapping

try:
    from os import PathLike
except ImportError:  # Python 3.5 support
    from pathlib import PurePath as PathLike

Openable = (str, PathLike)

logger = logging.getLogger(__name__)


def _cast(value):
    # Safely evaluate an expression node or a string containing a Python
    # literal or container display.
    # https://docs.python.org/3/library/ast.html#ast.literal_eval
    try:
        return ast.literal_eval(value)
    except (ValueError, SyntaxError):
        return value


def _cast_int(v):
    """Return int if possible."""
    return int(v) if hasattr(v, 'isdigit') and v.isdigit() else v


def _cast_urlstr(v):
    return unquote(v) if isinstance(v, str) else v


class NoValue:
    """Represent of no value object."""

    def __repr__(self):
        return '<{}>'.format(self.__class__.__name__)


class Env:
    """Provide scheme-based lookups of environment variables so that each
    caller doesn't have to pass in ``cast`` and ``default`` parameters.

    Usage:::

        import environ
        import os

        env = environ.Env(
            # set casting, default value
            MAIL_ENABLED=(bool, False),
            SMTP_LOGIN=(str, 'DEFAULT')
        )

        # Set the project base directory
        BASE_DIR = os.path.dirname(
            os.path.dirname(os.path.abspath(__file__))
        )

        # Take environment variables from .env file
        environ.Env.read_env(os.path.join(BASE_DIR, '.env'))

        # False if not in os.environ due to casting above
        MAIL_ENABLED = env('MAIL_ENABLED')

        # 'DEFAULT' if not in os.environ due to casting above
        SMTP_LOGIN = env('SMTP_LOGIN')
    """

    ENVIRON = os.environ
    NOTSET = NoValue()
    BOOLEAN_TRUE_STRINGS = ('true', 'on', 'ok', 'y', 'yes', '1')
    URL_CLASS = ParseResult

    POSTGRES_FAMILY = ['postgres', 'postgresql', 'psql', 'pgsql', 'postgis']
    ELASTICSEARCH_FAMILY = ['elasticsearch' + x for x in ['', '2', '5', '7']]

    DEFAULT_DATABASE_ENV = 'DATABASE_URL'
    DB_SCHEMES = {
        'postgres': DJANGO_POSTGRES,
        'postgresql': DJANGO_POSTGRES,
        'psql': DJANGO_POSTGRES,
        'pgsql': DJANGO_POSTGRES,
        'postgis': 'django.contrib.gis.db.backends.postgis',
        'mysql': 'django.db.backends.mysql',
        'mysql2': 'django.db.backends.mysql',
        'mysql-connector': 'mysql.connector.django',
        'mysqlgis': 'django.contrib.gis.db.backends.mysql',
        'mssql': 'sql_server.pyodbc',
        'oracle': 'django.db.backends.oracle',
        'pyodbc': 'sql_server.pyodbc',
        'redshift': 'django_redshift_backend',
        'spatialite': 'django.contrib.gis.db.backends.spatialite',
        'sqlite': 'django.db.backends.sqlite3',
        'ldap': 'ldapdb.backends.ldap',
    }
    _DB_BASE_OPTIONS = [
        'CONN_MAX_AGE',
        'ATOMIC_REQUESTS',
        'AUTOCOMMIT',
        'DISABLE_SERVER_SIDE_CURSORS',
        'CONN_HEALTH_CHECKS',
    ]

    DEFAULT_CACHE_ENV = 'CACHE_URL'
    CACHE_SCHEMES = {
        'dbcache': 'django.core.cache.backends.db.DatabaseCache',
        'dummycache': 'django.core.cache.backends.dummy.DummyCache',
        'filecache': 'django.core.cache.backends.filebased.FileBasedCache',
        'locmemcache': 'django.core.cache.backends.locmem.LocMemCache',
        'memcache': 'django.core.cache.backends.memcached.MemcachedCache',
        'pymemcache': PYMEMCACHE_DRIVER,
        'pylibmc': 'django.core.cache.backends.memcached.PyLibMCCache',
        'rediscache': REDIS_DRIVER,
        'redis': REDIS_DRIVER,
        'rediss': REDIS_DRIVER,
    }
    _CACHE_BASE_OPTIONS = [
        'TIMEOUT',
        'KEY_PREFIX',
        'VERSION',
        'KEY_FUNCTION',
        'BINARY',
    ]

    DEFAULT_EMAIL_ENV = 'EMAIL_URL'
    EMAIL_SCHEMES = {
        'smtp': 'django.core.mail.backends.smtp.EmailBackend',
        'smtps': 'django.core.mail.backends.smtp.EmailBackend',
        'smtp+tls': 'django.core.mail.backends.smtp.EmailBackend',
        'smtp+ssl': 'django.core.mail.backends.smtp.EmailBackend',
        'consolemail': 'django.core.mail.backends.console.EmailBackend',
        'filemail': 'django.core.mail.backends.filebased.EmailBackend',
        'memorymail': 'django.core.mail.backends.locmem.EmailBackend',
        'dummymail': 'django.core.mail.backends.dummy.EmailBackend'
    }
    _EMAIL_BASE_OPTIONS = ['EMAIL_USE_TLS', 'EMAIL_USE_SSL']

    DEFAULT_SEARCH_ENV = 'SEARCH_URL'
    SEARCH_SCHEMES = {
        "elasticsearch": "haystack.backends.elasticsearch_backend."
                         "ElasticsearchSearchEngine",
        "elasticsearch2": "haystack.backends.elasticsearch2_backend."
                          "Elasticsearch2SearchEngine",
        "elasticsearch5": "haystack.backends.elasticsearch5_backend."
                          "Elasticsearch5SearchEngine",
        "elasticsearch7": "haystack.backends.elasticsearch7_backend."
                          "Elasticsearch7SearchEngine",
        "solr": "haystack.backends.solr_backend.SolrEngine",
        "whoosh": "haystack.backends.whoosh_backend.WhooshEngine",
        "xapian": "haystack.backends.xapian_backend.XapianEngine",
        "simple": "haystack.backends.simple_backend.SimpleEngine",
    }
    CLOUDSQL = 'cloudsql'

    def __init__(self, **scheme):
        self.smart_cast = True
        self.escape_proxy = False
        self.prefix = ""
        self.scheme = scheme

    def __call__(self, var, cast=None, default=NOTSET, parse_default=False):
        return self.get_value(
            var,
            cast=cast,
            default=default,
            parse_default=parse_default
        )

    def __contains__(self, var):
        return var in self.ENVIRON

    def str(self, var, default=NOTSET, multiline=False):
        """
        :rtype: str
        """
        value = self.get_value(var, cast=str, default=default)
        if multiline:
            return re.sub(r'(\\r)?\\n', r'\n', value)
        return value

    def bytes(self, var, default=NOTSET, encoding='utf8'):
        """
        :rtype: bytes
        """
        value = self.get_value(var, cast=str, default=default)
        if hasattr(value, 'encode'):
            return value.encode(encoding)
        return value

    def bool(self, var, default=NOTSET):
        """
        :rtype: bool
        """
        return self.get_value(var, cast=bool, default=default)

    def int(self, var, default=NOTSET):
        """
        :rtype: int
        """
        return self.get_value(var, cast=int, default=default)

    def float(self, var, default=NOTSET):
        """
        :rtype: float
        """
        return self.get_value(var, cast=float, default=default)

    def json(self, var, default=NOTSET):
        """
        :returns: Json parsed
        """
        return self.get_value(var, cast=json.loads, default=default)

    def list(self, var, cast=None, default=NOTSET):
        """
        :rtype: list
        """
        return self.get_value(
            var,
            cast=list if not cast else [cast],
            default=default
        )

    def tuple(self, var, cast=None, default=NOTSET):
        """
        :rtype: tuple
        """
        return self.get_value(
            var,
            cast=tuple if not cast else (cast,),
            default=default
        )

    def dict(self, var, cast=dict, default=NOTSET):
        """
        :rtype: dict
        """
        return self.get_value(var, cast=cast, default=default)

    def url(self, var, default=NOTSET):
        """
        :rtype: urllib.parse.ParseResult
        """
        return self.get_value(
            var,
            cast=urlparse,
            default=default,
            parse_default=True
        )

    def db_url(self, var=DEFAULT_DATABASE_ENV, default=NOTSET, engine=None):
        """Returns a config dictionary, defaulting to DATABASE_URL.

        The db method is an alias for db_url.

        :rtype: dict
        """
        return self.db_url_config(
            self.get_value(var, default=default),
            engine=engine
        )

    db = db_url

    def cache_url(self, var=DEFAULT_CACHE_ENV, default=NOTSET, backend=None):
        """Returns a config dictionary, defaulting to CACHE_URL.

        The cache method is an alias for cache_url.

        :rtype: dict
        """
        return self.cache_url_config(
            self.url(var, default=default),
            backend=backend
        )

    cache = cache_url

    def email_url(self, var=DEFAULT_EMAIL_ENV, default=NOTSET, backend=None):
        """Returns a config dictionary, defaulting to EMAIL_URL.

        The email method is an alias for email_url.

        :rtype: dict
        """
        return self.email_url_config(
            self.url(var, default=default),
            backend=backend
        )

    email = email_url

    def search_url(self, var=DEFAULT_SEARCH_ENV, default=NOTSET, engine=None):
        """Returns a config dictionary, defaulting to SEARCH_URL.

        :rtype: dict
        """
        return self.search_url_config(
            self.url(var, default=default),
            engine=engine
        )

    def path(self, var, default=NOTSET, **kwargs):
        """
        :rtype: Path
        """
        return Path(self.get_value(var, default=default), **kwargs)

    def get_value(self, var, cast=None, default=NOTSET, parse_default=False):
        """Return value for given environment variable.

        :param str var:
            Name of variable.
        :param collections.abc.Callable or None cast:
            Type to cast return value as.
        :param default:
             If var not present in environ, return this instead.
        :param bool parse_default:
            Force to parse default.
        :returns: Value from environment or default (if set).
        :rtype: typing.IO[typing.Any]
        """

        logger.debug(
            "get '%s' casted as '%s' with default '%s'",
            var, cast, default)

        var_name = "{}{}".format(self.prefix, var)
        if var_name in self.scheme:
            var_info = self.scheme[var_name]

            try:
                has_default = len(var_info) == 2
            except TypeError:
                has_default = False

            if has_default:
                if not cast:
                    cast = var_info[0]

                if default is self.NOTSET:
                    try:
                        default = var_info[1]
                    except IndexError:
                        pass
            else:
                if not cast:
                    cast = var_info

        try:
            value = self.ENVIRON[var_name]
        except KeyError as exc:
            if default is self.NOTSET:
                error_msg = "Set the {} environment variable".format(var)
                raise ImproperlyConfigured(error_msg) from exc

            value = default

        # Resolve any proxied values
        prefix = b'$' if isinstance(value, bytes) else '$'
        escape = rb'\$' if isinstance(value, bytes) else r'\$'
        if hasattr(value, 'startswith') and value.startswith(prefix):
            value = value.lstrip(prefix)
            value = self.get_value(value, cast=cast, default=default)

        if self.escape_proxy and hasattr(value, 'replace'):
            value = value.replace(escape, prefix)

        # Smart casting
        if self.smart_cast:
            if cast is None and default is not None and \
                    not isinstance(default, NoValue):
                cast = type(default)

        value = None if default is None and value == '' else value

        if value != default or (parse_default and value is not None):
            value = self.parse_value(value, cast)

        return value

    @classmethod
    def parse_value(cls, value, cast):
        """Parse and cast provided value

        :param value: Stringed value.
        :param cast: Type to cast return value as.

        :returns: Casted value
        """
        if cast is None:
            return value
        if cast is bool:
            try:
                value = int(value) != 0
            except ValueError:
                value = value.lower() in cls.BOOLEAN_TRUE_STRINGS
        elif isinstance(cast, list):
            value = list(map(cast[0], [x for x in value.split(',') if x]))
        elif isinstance(cast, tuple):
            val = value.strip('(').strip(')').split(',')
            value = tuple(map(cast[0], [x for x in val if x]))
        elif isinstance(cast, dict):
            key_cast = cast.get('key', str)
            value_cast = cast.get('value', str)
            value_cast_by_key = cast.get('cast', {})
            value = dict(map(
                lambda kv: (
                    key_cast(kv[0]),
                    cls.parse_value(
                        kv[1],
                        value_cast_by_key.get(kv[0], value_cast)
                    )
                ),
                [val.split('=') for val in value.split(';') if val]
            ))
        elif cast is dict:
            value = dict([v.split('=', 1) for v in value.split(',') if v])
        elif cast is list:
            value = [x for x in value.split(',') if x]
        elif cast is tuple:
            val = value.strip('(').strip(')').split(',')
            # pylint: disable=consider-using-generator
            value = tuple([x for x in val if x])
        elif cast is float:
            # clean string
            float_str = re.sub(r'[^\d,.-]', '', value)
            # split for avoid thousand separator and different
            # locale comma/dot symbol
            parts = re.split(r'[,.]', float_str)
            if len(parts) == 1:
                float_str = parts[0]
            else:
                float_str = "{}.{}".format(''.join(parts[0:-1]), parts[-1])
            value = float(float_str)
        else:
            value = cast(value)
        return value

    @classmethod
    def db_url_config(cls, url, engine=None):
        """Parse an arbitrary database URL.

        Supports the following URL schemas:

        * PostgreSQL: ``postgres[ql]?://`` or ``p[g]?sql://``
        * PostGIS: ``postgis://``
        * MySQL: ``mysql://`` or ``mysql2://``
        * MySQL (GIS): ``mysqlgis://``
        * MySQL Connector Python from Oracle: ``mysql-connector://``
        * SQLite: ``sqlite://``
        * SQLite with SpatiaLite for GeoDjango: ``spatialite://``
        * Oracle: ``oracle://``
        * Microsoft SQL Server: ``mssql://``
        * PyODBC: ``pyodbc://``
        * Amazon Redshift: ``redshift://``
        * LDAP: ``ldap://``

        :param urllib.parse.ParseResult or str url:
            Database URL to parse.
        :param str or None engine:
            If None, the database engine is evaluates from the ``url``.
        :return: Parsed database URL.
        :rtype: dict
        """
        if not isinstance(url, cls.URL_CLASS):
            if url == 'sqlite://:memory:':
                # this is a special case, because if we pass this URL into
                # urlparse, urlparse will choke trying to interpret "memory"
                # as a port number
                return {
                    'ENGINE': cls.DB_SCHEMES['sqlite'],
                    'NAME': ':memory:'
                }
                # note: no other settings are required for sqlite
            url = urlparse(url)

        config = {}

        # Remove query strings.
        path = url.path[1:]
        path = unquote_plus(path.split('?', 2)[0])

        if url.scheme == 'sqlite':
            if path == '':
                # if we are using sqlite and we have no path, then assume we
                # want an in-memory database (this is the behaviour of
                # sqlalchemy)
                path = ':memory:'
            if url.netloc:
                warnings.warn('SQLite URL contains host component %r, '
                              'it will be ignored' % url.netloc, stacklevel=3)
        if url.scheme == 'ldap':
            path = '{scheme}://{hostname}'.format(
                scheme=url.scheme,
                hostname=url.hostname,
            )
            if url.port:
                path += ':{port}'.format(port=url.port)

        user_host = url.netloc.rsplit('@', 1)
        if url.scheme in cls.POSTGRES_FAMILY and ',' in user_host[-1]:
            # Parsing postgres cluster dsn
            hinfo = list(
                itertools.zip_longest(
                    *(
                        host.rsplit(':', 1)
                        for host in user_host[-1].split(',')
                    )
                )
            )
            hostname = ','.join(hinfo[0])
            port = ','.join(filter(None, hinfo[1])) if len(hinfo) == 2 else ''
        else:
            hostname = url.hostname
            port = url.port

        # Update with environment configuration.
        config.update({
            'NAME': path or '',
            'USER': _cast_urlstr(url.username) or '',
            'PASSWORD': _cast_urlstr(url.password) or '',
            'HOST': hostname or '',
            'PORT': _cast_int(port) or '',
        })

        if (
                url.scheme in cls.POSTGRES_FAMILY and path.startswith('/')
                or cls.CLOUDSQL in path and path.startswith('/')
        ):
            config['HOST'], config['NAME'] = path.rsplit('/', 1)

        if url.scheme == 'oracle' and path == '':
            config['NAME'] = config['HOST']
            config['HOST'] = ''

        if url.scheme == 'oracle':
            # Django oracle/base.py strips port and fails on non-string value
            if not config['PORT']:
                del config['PORT']
            else:
                config['PORT'] = str(config['PORT'])

        if url.query:
            config_options = {}
            for k, v in parse_qs(url.query).items():
                if k.upper() in cls._DB_BASE_OPTIONS:
                    config.update({k.upper(): _cast(v[0])})
                else:
                    config_options.update({k: _cast_int(v[0])})
            config['OPTIONS'] = config_options

        if engine:
            config['ENGINE'] = engine
        else:
            config['ENGINE'] = url.scheme

        if config['ENGINE'] in cls.DB_SCHEMES:
            config['ENGINE'] = cls.DB_SCHEMES[config['ENGINE']]

        if not config.get('ENGINE', False):
            warnings.warn("Engine not recognized from url: {}".format(config))
            return {}

        return config

    @classmethod
    def cache_url_config(cls, url, backend=None):
        """Parse an arbitrary cache URL.

        :param urllib.parse.ParseResult or str url:
            Cache URL to parse.
        :param str or None backend:
            If None, the backend is evaluates from the ``url``.
        :return: Parsed cache URL.
        :rtype: dict
        """
        if not isinstance(url, cls.URL_CLASS):
            if not url:
                return {}
            url = urlparse(url)

        if url.scheme not in cls.CACHE_SCHEMES:
            raise ImproperlyConfigured(
                'Invalid cache schema {}'.format(url.scheme)
            )

        location = url.netloc.split(',')
        if len(location) == 1:
            location = location[0]

        config = {
            'BACKEND': cls.CACHE_SCHEMES[url.scheme],
            'LOCATION': location,
        }

        # Add the drive to LOCATION
        if url.scheme == 'filecache':
            config.update({
                'LOCATION': url.netloc + url.path,
            })

        # urlparse('pymemcache://127.0.0.1:11211')
        # => netloc='127.0.0.1:11211', path=''
        #
        # urlparse('pymemcache://memcached:11211/?key_prefix=ci')
        # => netloc='memcached:11211', path='/'
        #
        # urlparse('memcache:///tmp/memcached.sock')
        # => netloc='', path='/tmp/memcached.sock'
        if not url.netloc and url.scheme in ['memcache', 'pymemcache']:
            config.update({
                'LOCATION': 'unix:' + url.path,
            })
        elif url.scheme.startswith('redis'):
            if url.hostname:
                scheme = url.scheme.replace('cache', '')
            else:
                scheme = 'unix'
            locations = [scheme + '://' + loc + url.path
                         for loc in url.netloc.split(',')]
            if len(locations) == 1:
                config['LOCATION'] = locations[0]
            else:
                config['LOCATION'] = locations

        if url.query:
            config_options = {}
            for k, v in parse_qs(url.query).items():
                opt = {k.upper(): _cast(v[0])}
                if k.upper() in cls._CACHE_BASE_OPTIONS:
                    config.update(opt)
                else:
                    config_options.update(opt)
            config['OPTIONS'] = config_options

        if backend:
            config['BACKEND'] = backend

        return config

    @classmethod
    def email_url_config(cls, url, backend=None):
        """Parse an arbitrary email URL.

        :param urllib.parse.ParseResult or str url:
            Email URL to parse.
        :param str or None backend:
            If None, the backend is evaluates from the ``url``.
        :return: Parsed email URL.
        :rtype: dict
        """

        config = {}

        url = urlparse(url) if not isinstance(url, cls.URL_CLASS) else url

        # Remove query strings
        path = url.path[1:]
        path = unquote_plus(path.split('?', 2)[0])

        # Update with environment configuration
        config.update({
            'EMAIL_FILE_PATH': path,
            'EMAIL_HOST_USER': _cast_urlstr(url.username),
            'EMAIL_HOST_PASSWORD': _cast_urlstr(url.password),
            'EMAIL_HOST': url.hostname,
            'EMAIL_PORT': _cast_int(url.port),
        })

        if backend:
            config['EMAIL_BACKEND'] = backend
        elif url.scheme not in cls.EMAIL_SCHEMES:
            raise ImproperlyConfigured('Invalid email schema %s' % url.scheme)
        elif url.scheme in cls.EMAIL_SCHEMES:
            config['EMAIL_BACKEND'] = cls.EMAIL_SCHEMES[url.scheme]

        if url.scheme in ('smtps', 'smtp+tls'):
            config['EMAIL_USE_TLS'] = True
        elif url.scheme == 'smtp+ssl':
            config['EMAIL_USE_SSL'] = True

        if url.query:
            config_options = {}
            for k, v in parse_qs(url.query).items():
                opt = {k.upper(): _cast_int(v[0])}
                if k.upper() in cls._EMAIL_BASE_OPTIONS:
                    config.update(opt)
                else:
                    config_options.update(opt)
            config['OPTIONS'] = config_options

        return config

    @classmethod
    def search_url_config(cls, url, engine=None):
        """Parse an arbitrary search URL.

        :param urllib.parse.ParseResult or str url:
            Search URL to parse.
        :param str or None engine:
            If None, the engine is evaluates from the ``url``.
        :return: Parsed search URL.
        :rtype: dict
        """

        config = {}

        url = urlparse(url) if not isinstance(url, cls.URL_CLASS) else url

        # Remove query strings.
        path = url.path[1:]
        path = unquote_plus(path.split('?', 2)[0])

        if url.scheme not in cls.SEARCH_SCHEMES:
            raise ImproperlyConfigured(
                'Invalid search schema %s' % url.scheme
            )
        config["ENGINE"] = cls.SEARCH_SCHEMES[url.scheme]

        # check commons params
        params = {}  # type: dict
        if url.query:
            params = parse_qs(url.query)
            if 'EXCLUDED_INDEXES' in params:
                config['EXCLUDED_INDEXES'] \
                    = params['EXCLUDED_INDEXES'][0].split(',')
            if 'INCLUDE_SPELLING' in params:
                config['INCLUDE_SPELLING'] = cls.parse_value(
                    params['INCLUDE_SPELLING'][0],
                    bool
                )
            if 'BATCH_SIZE' in params:
                config['BATCH_SIZE'] = cls.parse_value(
                    params['BATCH_SIZE'][0],
                    int
                )

        if url.scheme == 'simple':
            return config
        if url.scheme in ['solr'] + cls.ELASTICSEARCH_FAMILY:
            if 'KWARGS' in params:
                config['KWARGS'] = params['KWARGS'][0]

        # remove trailing slash
        if path.endswith("/"):
            path = path[:-1]

        if url.scheme == 'solr':
            config['URL'] = urlunparse(
                ('http',) + url[1:2] + (path,) + ('', '', '')
            )
            if 'TIMEOUT' in params:
                config['TIMEOUT'] = cls.parse_value(params['TIMEOUT'][0], int)
            return config

        if url.scheme in cls.ELASTICSEARCH_FAMILY:
            split = path.rsplit("/", 1)

            if len(split) > 1:
                path = "/".join(split[:-1])
                index = split[-1]
            else:
                path = ""
                index = split[0]

            config['URL'] = urlunparse(
                ('http',) + url[1:2] + (path,) + ('', '', '')
            )
            if 'TIMEOUT' in params:
                config['TIMEOUT'] = cls.parse_value(params['TIMEOUT'][0], int)
            config['INDEX_NAME'] = index
            return config

        config['PATH'] = '/' + path

        if url.scheme == 'whoosh':
            if 'STORAGE' in params:
                config['STORAGE'] = params['STORAGE'][0]
            if 'POST_LIMIT' in params:
                config['POST_LIMIT'] = cls.parse_value(
                    params['POST_LIMIT'][0],
                    int
                )
        elif url.scheme == 'xapian':
            if 'FLAGS' in params:
                config['FLAGS'] = params['FLAGS'][0]

        if engine:
            config['ENGINE'] = engine

        return config

    @classmethod
    def read_env(cls, env_file=None, overwrite=False, encoding='utf8',
                 **overrides):
        r"""Read a .env file into os.environ.

        If not given a path to a dotenv path, does filthy magic stack
        backtracking to find the dotenv in the same directory as the file that
        called ``read_env``.

        Existing environment variables take precedent and are NOT overwritten
        by the file content. ``overwrite=True`` will force an overwrite of
        existing environment variables.

        Refs:

        * https://wellfire.co/learn/easier-12-factor-django

        :param env_file: The path to the ``.env`` file your application should
            use. If a path is not provided, `read_env` will attempt to import
            the Django settings module from the Django project root.
        :param overwrite: ``overwrite=True`` will force an overwrite of
            existing environment variables.
        :param encoding: The encoding to use when reading the environment file.
        :param \**overrides: Any additional keyword arguments provided directly
            to read_env will be added to the environment. If the key matches an
            existing environment variable, the value will be overridden.
        """
        if env_file is None:
            # pylint: disable=protected-access
            frame = sys._getframe()
            env_file = os.path.join(
                os.path.dirname(frame.f_back.f_code.co_filename),
                '.env'
            )
            if not os.path.exists(env_file):
                logger.info(
                    "%s doesn't exist - if you're not configuring your "
                    "environment separately, create one.", env_file)
                return

        try:
            if isinstance(env_file, Openable):
                # Python 3.5 support (wrap path with str).
                with open(str(env_file), encoding=encoding) as f:
                    content = f.read()
            else:
                with env_file as f:
                    content = f.read()
        except OSError:
            logger.info(
                "%s not found - if you're not configuring your "
                "environment separately, check this.", env_file)
            return

        logger.debug('Read environment variables from: %s', env_file)

        def _keep_escaped_format_characters(match):
            """Keep escaped newline/tabs in quoted strings"""
            escaped_char = match.group(1)
            if escaped_char in 'rnt':
                return '\\' + escaped_char
            return escaped_char

        for line in content.splitlines():
            m1 = re.match(r'\A(?:export )?([A-Za-z_0-9]+)=(.*)\Z', line)
            if m1:
                key, val = m1.group(1), m1.group(2)
                m2 = re.match(r"\A'(.*)'\Z", val)
                if m2:
                    val = m2.group(1)
                m3 = re.match(r'\A"(.*)"\Z', val)
                if m3:
                    val = re.sub(r'\\(.)', _keep_escaped_format_characters,
                                 m3.group(1))
                overrides[key] = str(val)
            elif not line or line.startswith('#'):
                # ignore warnings for empty line-breaks or comments
                pass
            else:
                logger.warning('Invalid line: %s', line)

        def set_environ(envval):
            """Return lambda to set environ.

             Use setdefault unless overwrite is specified.
             """
            if overwrite:
                return lambda k, v: envval.update({k: str(v)})
            return lambda k, v: envval.setdefault(k, str(v))

        setenv = set_environ(cls.ENVIRON)

        for key, value in overrides.items():
            setenv(key, value)


class FileAwareEnv(Env):
    """
    First look for environment variables with ``_FILE`` appended. If found,
    their contents will be read from the file system and used instead.

    Use as a drop-in replacement for the standard ``environ.Env``:

    .. code-block:: python

        python env = environ.FileAwareEnv()

    For example, if a ``SECRET_KEY_FILE`` environment variable was set,
    ``env("SECRET_KEY")`` would find the related variable, returning the file
    contents rather than ever looking up a ``SECRET_KEY`` environment variable.
    """
    ENVIRON = FileAwareMapping()


class Path:
    """Inspired to Django Two-scoops, handling File Paths in Settings."""

    def path(self, *paths, **kwargs):
        """Create new Path based on self.root and provided paths.

        :param paths: List of sub paths
        :param kwargs: required=False
        :rtype: Path
        """
        return self.__class__(self.__root__, *paths, **kwargs)

    def file(self, name, *args, **kwargs):
        r"""Open a file.

        :param str name: Filename appended to :py:attr:`~root`
        :param \*args: ``*args`` passed to :py:func:`open`
        :param \**kwargs: ``**kwargs`` passed to :py:func:`open`
        :rtype: typing.IO[typing.Any]
        """
        # pylint: disable=unspecified-encoding
        return open(self(name), *args, **kwargs)

    @property
    def root(self):
        """Current directory for this Path"""
        return self.__root__

    # pylint: disable=keyword-arg-before-vararg
    def __init__(self, start='', *paths, **kwargs):

        super().__init__()

        if kwargs.get('is_file', False):
            start = os.path.dirname(start)

        self.__root__ = self._absolute_join(start, *paths, **kwargs)

    def __call__(self, *paths, **kwargs):
        """Retrieve the absolute path, with appended paths

        :param paths: List of sub path of self.root
        :param kwargs: required=False
        """
        return self._absolute_join(self.__root__, *paths, **kwargs)

    def __eq__(self, other):
        if isinstance(other, Path):
            return self.__root__ == other.__root__
        return self.__root__ == other

    def __ne__(self, other):
        return not self.__eq__(other)

    def __add__(self, other):
        if not isinstance(other, Path):
            return Path(self.__root__, other)
        return Path(self.__root__, other.__root__)

    def __sub__(self, other):
        if isinstance(other, int):
            return self.path('../' * other)
        if isinstance(other, str) and self.__root__.endswith(other):
            return Path(self.__root__.rstrip(other))

        raise TypeError(
            "unsupported operand type(s) for -: '{self}' and '{other}' "
            "unless value of {self} ends with value of {other}".format(
                self=type(self), other=type(other)
            )
        )

    def __invert__(self):
        return self.path('..')

    def __contains__(self, item):
        base_path = self.__root__
        if len(base_path) > 1:
            base_path = os.path.join(base_path, '')
        return item.__root__.startswith(base_path)

    def __repr__(self):
        return "<Path:{}>".format(self.__root__)

    def __str__(self):
        return self.__root__

    def __unicode__(self):
        return self.__str__()

    def __getitem__(self, *args, **kwargs):
        return self.__str__().__getitem__(*args, **kwargs)

    def __fspath__(self):
        return self.__str__()

    def rfind(self, *args, **kwargs):
        """Proxy method to :py:func:`str.rfind`"""
        return str(self).rfind(*args, **kwargs)

    def find(self, *args, **kwargs):
        """Proxy method to :py:func:`str.find`"""
        return str(self).find(*args, **kwargs)

    @staticmethod
    def _absolute_join(base, *paths, **kwargs):
        absolute_path = os.path.abspath(os.path.join(base, *paths))
        if kwargs.get('required', False) and not os.path.exists(absolute_path):
            raise ImproperlyConfigured(
                "Create required path: {}".format(absolute_path))
        return absolute_path
