"""A class that performs TLS-SNI-01 challenges for Nginx"""

import itertools
import logging
import os

from letsencrypt import errors
from letsencrypt.plugins import common

from letsencrypt_nginx import obj
from letsencrypt_nginx import nginxparser


logger = logging.getLogger(__name__)


class NginxTlsSni01(common.TLSSNI01):
    """TLS-SNI-01 authenticator for Nginx

    :ivar configurator: NginxConfigurator object
    :type configurator: :class:`~nginx.configurator.NginxConfigurator`

    :ivar list achalls: Annotated
        class:`~letsencrypt.achallenges.KeyAuthorizationAnnotatedChallenge`
        challenges

    :param list indices: Meant to hold indices of challenges in a
        larger array. NginxTlsSni01 is capable of solving many challenges
        at once which causes an indexing issue within NginxConfigurator
        who must return all responses in order.  Imagine NginxConfigurator
        maintaining state about where all of the http-01 Challenges,
        TLS-SNI-01 Challenges belong in the response array.  This is an
        optional utility.

    :param str challenge_conf: location of the challenge config file

    """

    def perform(self):
        """Perform a challenge on Nginx.

        :returns: list of :class:`letsencrypt.acme.challenges.TLSSNI01Response`
        :rtype: list

        """
        if not self.achalls:
            return []

        self.configurator.save()

        addresses = []
        default_addr = "{0} default_server ssl".format(
            self.configurator.config.tls_sni_01_port)

        for achall in self.achalls:
            vhost = self.configurator.choose_vhost(achall.domain)
            if vhost is None:
                logger.error(
                    "No nginx vhost exists with server_name matching: %s. "
                    "Please specify server_names in the Nginx config.",
                    achall.domain)
                return None

            for addr in vhost.addrs:
                if addr.default:
                    addresses.append([obj.Addr.fromstring(default_addr)])
                    break
            else:
                addresses.append(list(vhost.addrs))

        # Create challenge certs
        responses = [self._setup_challenge_cert(x) for x in self.achalls]

        # Set up the configuration
        self._mod_config(addresses)

        # Save reversible changes
        self.configurator.save("SNI Challenge", True)

        return responses

    def _mod_config(self, ll_addrs):
        """Modifies Nginx config to include challenge server blocks.

        :param list ll_addrs: list of lists of
            :class:`letsencrypt_nginx.obj.Addr` to apply

        :raises .MisconfigurationError:
            Unable to find a suitable HTTP block in which to include
            authenticator hosts.

        """
        # Add the 'include' statement for the challenges if it doesn't exist
        # already in the main config
        included = False
        include_directive = ['include', self.challenge_conf]
        root = self.configurator.parser.loc["root"]

        bucket_directive = ['server_names_hash_bucket_size', '128']

        main = self.configurator.parser.parsed[root]
        for key, body in main:
            if key == ['http']:
                found_bucket = False
                for k, _ in body:
                    if k == bucket_directive[0]:
                        found_bucket = True
                if not found_bucket:
                    body.insert(0, bucket_directive)
                if include_directive not in body:
                    body.insert(0, include_directive)
                included = True
                break
        if not included:
            raise errors.MisconfigurationError(
                'LetsEncrypt could not find an HTTP block to include '
                'TLS-SNI-01 challenges in %s.' % root)

        config = [self._make_server_block(pair[0], pair[1])
                  for pair in itertools.izip(self.achalls, ll_addrs)]

        self.configurator.reverter.register_file_creation(
            True, self.challenge_conf)

        with open(self.challenge_conf, "w") as new_conf:
            nginxparser.dump(config, new_conf)

    def _make_server_block(self, achall, addrs):
        """Creates a server block for a challenge.

        :param achall: Annotated TLS-SNI-01 challenge
        :type achall:
            :class:`letsencrypt.achallenges.KeyAuthorizationAnnotatedChallenge`

        :param list addrs: addresses of challenged domain
            :class:`list` of type :class:`~nginx.obj.Addr`

        :returns: server block for the challenge host
        :rtype: list

        """
        document_root = os.path.join(
            self.configurator.config.work_dir, "tls_sni_01_page")

        block = [['listen', str(addr)] for addr in addrs]

        block.extend([['server_name',
                       achall.response(achall.account_key).z_domain],
                      ['include', self.configurator.parser.loc["ssl_options"]],
                      # access and error logs necessary for
                      # integration testing (non-root)
                      ['access_log', os.path.join(
                          self.configurator.config.work_dir, 'access.log')],
                      ['error_log', os.path.join(
                          self.configurator.config.work_dir, 'error.log')],
                      ['ssl_certificate', self.get_cert_path(achall)],
                      ['ssl_certificate_key', self.get_key_path(achall)],
                      [['location', '/'], [['root', document_root]]]])

        return [['server'], block]
