# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.

import logging

import requests
import six
from six.moves import urllib

from keystoneclient import exceptions
from keystoneclient.openstack.common import jsonutils
from keystoneclient import utils


USER_AGENT = 'python-keystoneclient'

_logger = logging.getLogger(__name__)


def request(url, method='GET', **kwargs):
    return Session().request(url, method=method, **kwargs)


class _FakeRequestSession(object):
    """This object is a temporary hack that should be removed later.

    Keystoneclient has a cyclical dependency with its managers which is
    preventing it from being cleaned up correctly. This is always bad but when
    we switched to doing connection pooling this object wasn't getting cleaned
    either and so we had left over TCP connections hanging around.

    Until we can fix the client cleanup we rollback the use of a requests
    session and do individual connections like we used to.
    """

    def request(self, *args, **kwargs):
        return requests.request(*args, **kwargs)


class Session(object):

    user_agent = None

    REDIRECT_STATUSES = (301, 302, 303, 305, 307)
    DEFAULT_REDIRECT_LIMIT = 30

    @utils.positional(2, enforcement=utils.positional.WARN)
    def __init__(self, auth=None, session=None, original_ip=None, verify=True,
                 cert=None, timeout=None, user_agent=None,
                 redirect=DEFAULT_REDIRECT_LIMIT):
        """Maintains client communication state and common functionality.

        As much as possible the parameters to this class reflect and are passed
        directly to the requests library.

        :param auth: An authentication plugin to authenticate the session with.
                     (optional, defaults to None)
        :param requests.Session session: A requests session object that can be
                                         used for issuing requests. (optional)
        :param string original_ip: The original IP of the requesting user
                                   which will be sent to identity service in a
                                   'Forwarded' header. (optional)
        :param verify: The verification arguments to pass to requests. These
                       are of the same form as requests expects, so True or
                       False to verify (or not) against system certificates or
                       a path to a bundle or CA certs to check against or None
                       for requests to attempt to locate and use certificates.
                       (optional, defaults to True)
        :param cert: A client certificate to pass to requests. These are of the
                     same form as requests expects. Either a single filename
                     containing both the certificate and key or a tuple
                     containing the path to the certificate then a path to the
                     key. (optional)
        :param float timeout: A timeout to pass to requests. This should be a
                              numerical value indicating some amount
                              (or fraction) of seconds or 0 for no timeout.
                              (optional, defaults to 0)
        :param string user_agent: A User-Agent header string to use for the
                                  request. If not provided a default is used.
                                  (optional, defaults to
                                  'python-keystoneclient')
        :param int/bool redirect: Controls the maximum number of redirections
                                  that can be followed by a request. Either an
                                  integer for a specific count or True/False
                                  for forever/never. (optional, default to 30)
        """
        if not session:
            session = _FakeRequestSession()

        self.auth = auth
        self.session = session
        self.original_ip = original_ip
        self.verify = verify
        self.cert = cert
        self.timeout = None
        self.redirect = redirect

        if timeout is not None:
            self.timeout = float(timeout)

        # don't override the class variable if none provided
        if user_agent is not None:
            self.user_agent = user_agent

    @utils.positional(enforcement=utils.positional.WARN)
    def request(self, url, method, json=None, original_ip=None,
                user_agent=None, redirect=None, authenticated=None,
                endpoint_filter=None, **kwargs):
        """Send an HTTP request with the specified characteristics.

        Wrapper around `requests.Session.request` to handle tasks such as
        setting headers, JSON encoding/decoding, and error handling.

        Arguments that are not handled are passed through to the requests
        library.

        :param string url: Path or fully qualified URL of HTTP request. If only
                           a path is provided then endpoint_filter must also be
                           provided such that the base URL can be determined.
                           If a fully qualified URL is provided then
                           endpoint_filter will be ignored.
        :param string method: The http method to use. (eg. 'GET', 'POST')
        :param string original_ip: Mark this request as forwarded for this ip.
                                   (optional)
        :param dict headers: Headers to be included in the request. (optional)
        :param json: Some data to be represented as JSON. (optional)
        :param string user_agent: A user_agent to use for the request. If
                                  present will override one present in headers.
                                  (optional)
        :param int/bool redirect: the maximum number of redirections that
                                  can be followed by a request. Either an
                                  integer for a specific count or True/False
                                  for forever/never. (optional)
        :param bool authenticated: True if a token should be attached to this
                                   request, False if not or None for attach if
                                   an auth_plugin is available.
                                   (optional, defaults to None)
        :param dict endpoint_filter: Data to be provided to an auth plugin with
                                     which it should be able to determine an
                                     endpoint to use for this request. If not
                                     provided then URL is expected to be a
                                     fully qualified URL. (optional)
        :param kwargs: any other parameter that can be passed to
                       requests.Session.request (such as `headers`). Except:
                       'data' will be overwritten by the data in 'json' param.
                       'allow_redirects' is ignored as redirects are handled
                       by the session.

        :raises exceptions.ClientException: For connection failure, or to
                                            indicate an error response code.

        :returns: The response to the request.
        """

        headers = kwargs.setdefault('headers', dict())

        if authenticated is None:
            authenticated = self.auth is not None

        if authenticated:
            token = self.get_token()

            if not token:
                raise exceptions.AuthorizationFailure("No token Available")

            headers['X-Auth-Token'] = token

        # if we are passed a fully qualified URL and a endpoint_filter we
        # should ignore the filter. This will make it easier for clients who
        # want to overrule the default endpoint_filter data added to all client
        # requests. We check fully qualified here by the presence of a host.
        url_data = urllib.parse.urlparse(url)
        if endpoint_filter and not url_data.netloc:
            base_url = self.get_endpoint(**endpoint_filter)

            if not base_url:
                raise exceptions.EndpointNotFound()

            url = '%s/%s' % (base_url.rstrip('/'), url.lstrip('/'))

        if self.cert:
            kwargs.setdefault('cert', self.cert)

        if self.timeout is not None:
            kwargs.setdefault('timeout', self.timeout)

        if user_agent:
            headers['User-Agent'] = user_agent
        elif self.user_agent:
            user_agent = headers.setdefault('User-Agent', self.user_agent)
        else:
            user_agent = headers.setdefault('User-Agent', USER_AGENT)

        if self.original_ip:
            headers.setdefault('Forwarded',
                               'for=%s;by=%s' % (self.original_ip, user_agent))

        if json is not None:
            headers['Content-Type'] = 'application/json'
            kwargs['data'] = jsonutils.dumps(json)

        kwargs.setdefault('verify', self.verify)

        string_parts = ['curl -i']

        # NOTE(jamielennox): None means let requests do its default validation
        # so we need to actually check that this is False.
        if self.verify is False:
            string_parts.append('--insecure')

        if method:
            string_parts.extend(['-X', method])

        string_parts.append(url)

        if headers:
            for header in six.iteritems(headers):
                string_parts.append('-H "%s: %s"' % header)

        try:
            string_parts.append("-d '%s'" % kwargs['data'])
        except KeyError:
            pass

        _logger.debug('REQ: %s', ' '.join(string_parts))

        # Force disable requests redirect handling. We will manage this below.
        kwargs['allow_redirects'] = False

        if redirect is None:
            redirect = self.redirect

        resp = self._send_request(url, method, redirect, **kwargs)

        # NOTE(jamielennox): we create a tuple here to be the same as what is
        # returned by the requests library.
        resp.history = tuple(resp.history)

        if resp.status_code >= 400:
            _logger.debug('Request returned failure status: %s',
                          resp.status_code)
            raise exceptions.from_response(resp, method, url)

        return resp

    def _send_request(self, url, method, redirect, **kwargs):
        # NOTE(jamielennox): We handle redirection manually because the
        # requests lib follows some browser patterns where it will redirect
        # POSTs as GETs for certain statuses which is not want we want for an
        # API. See: https://en.wikipedia.org/wiki/Post/Redirect/Get

        try:
            resp = self.session.request(method, url, **kwargs)
        except requests.exceptions.SSLError:
            msg = 'SSL exception connecting to %s' % url
            raise exceptions.SSLError(msg)
        except requests.exceptions.Timeout:
            msg = 'Request to %s timed out' % url
            raise exceptions.Timeout(msg)
        except requests.exceptions.ConnectionError:
            msg = 'Unable to establish connection to %s' % url
            raise exceptions.ConnectionError(msg)

        _logger.debug('RESP: [%s] %s\nRESP BODY: %s\n',
                      resp.status_code, resp.headers, resp.text)

        if resp.status_code in self.REDIRECT_STATUSES:
            # be careful here in python True == 1 and False == 0
            if isinstance(redirect, bool):
                redirect_allowed = redirect
            else:
                redirect -= 1
                redirect_allowed = redirect >= 0

            if not redirect_allowed:
                return resp

            try:
                location = resp.headers['location']
            except KeyError:
                _logger.warn("Failed to redirect request to %s as new "
                             "location was not provided.", resp.url)
            else:
                new_resp = self._send_request(location, method, redirect,
                                              **kwargs)

                if not isinstance(new_resp.history, list):
                    new_resp.history = list(new_resp.history)
                new_resp.history.insert(0, resp)
                resp = new_resp

        return resp

    def head(self, url, **kwargs):
        return self.request(url, 'HEAD', **kwargs)

    def get(self, url, **kwargs):
        return self.request(url, 'GET', **kwargs)

    def post(self, url, **kwargs):
        return self.request(url, 'POST', **kwargs)

    def put(self, url, **kwargs):
        return self.request(url, 'PUT', **kwargs)

    def delete(self, url, **kwargs):
        return self.request(url, 'DELETE', **kwargs)

    def patch(self, url, **kwargs):
        return self.request(url, 'PATCH', **kwargs)

    @classmethod
    def construct(cls, kwargs):
        """Handles constructing a session from the older HTTPClient args as
        well as the new request style arguments.

        *DEPRECATED*: This function is purely for bridging the gap between
        older client arguments and the session arguments that they relate to.
        It is not intended to be used as a generic Session Factory.

        This function purposefully modifies the input kwargs dictionary so that
        the remaining kwargs dict can be reused and passed on to other
        functionswithout session arguments.

        """
        verify = kwargs.pop('verify', None)
        cacert = kwargs.pop('cacert', None)
        cert = kwargs.pop('cert', None)
        key = kwargs.pop('key', None)
        insecure = kwargs.pop('insecure', False)

        if verify is None:
            if insecure:
                verify = False
            else:
                verify = cacert or True

        if cert and key:
            # passing cert and key together is deprecated in favour of the
            # requests lib form of having the cert and key as a tuple
            cert = (cert, key)

        return cls(verify=verify, cert=cert,
                   timeout=kwargs.pop('timeout', None),
                   session=kwargs.pop('session', None),
                   original_ip=kwargs.pop('original_ip', None),
                   user_agent=kwargs.pop('user_agent', None))

    def get_token(self):
        """Return a token as provided by the auth plugin.

        :raises AuthorizationFailure: if a new token fetch fails.

        :returns string: A valid token.
        """
        if not self.auth:
            raise exceptions.MissingAuthPlugin("Token Required")

        try:
            return self.auth.get_token(self)
        except exceptions.HTTPError as exc:
            raise exceptions.AuthorizationFailure("Authentication failure: "
                                                  "%s" % exc)

    def get_endpoint(self, **kwargs):
        """Get an endpoint as provided by the auth plugin."""
        if not self.auth:
            raise exceptions.MissingAuthPlugin('An auth plugin is required to '
                                               'determine the endpoint URL.')

        return self.auth.get_endpoint(self, **kwargs)
