import os
import logging

from abc import ABCMeta, abstractmethod
from six import add_metaclass
import requests
from util.abchelpers import nooper
from util.repomirror.validator import RepoMirrorConfigValidator

from _init import CONF_DIR
TOKEN_VALIDITY_LIFETIME_S = 60  # Amount of time the repo mirror has to call the skopeo URL

MITM_CERT_PATH = os.path.join(CONF_DIR, 'mitm.cert')

DEFAULT_HTTP_HEADERS = {'Connection': 'close'}

logger = logging.getLogger(__name__)


class RepoMirrorException(Exception):
  """ Exception raised when a layer fails to analyze due to a request issue. """

class RepoMirrorRetryException(Exception):
  """ Exception raised when a layer fails to analyze due to a request issue, and the request should
      be retried.
  """

class APIRequestFailure(Exception):
  """ Exception raised when there is a failure to conduct an API request. """

class Non200ResponseException(Exception):
  """ Exception raised when the upstream API returns a non-200 HTTP status code. """
  def __init__(self, response):
    super(Non200ResponseException, self).__init__()
    self.response = response


_API_METHOD_GET_REPOSITORY = 'repository/%s'
_API_METHOD_PING = 'metrics'


class RepoMirrorAPI(object):
  """ Helper class for talking to the Repository Mirror service (usually Skopeo). """
  def __init__(self, config, server_hostname=None, skip_validation=False, instance_keys=None):
    feature_enabled = config.get('FEATURE_REPO_MIRROR', False)
    has_valid_config = skip_validation

    if not skip_validation and feature_enabled:
      config_validator = RepoMirrorConfigValidator(feature_enabled)
      has_valid_config = config_validator.valid()

    self.state = NoopRepoMirrorAPI()
    if feature_enabled and has_valid_config:
      self.state = ImplementedRepoMirrorAPI(config, server_hostname, instance_keys=instance_keys)

  def __getattr__(self, name):
    return getattr(self.state, name, None)


@add_metaclass(ABCMeta)
class RepoMirrorAPIInterface(object):
  """ Helper class for talking to the Repository Mirror service (usually Skopeo Worker). """

  @abstractmethod
  def ping(self):
    """ Calls GET on the metrics endpoint of the repo mirror to ensure it is running
        and properly configured. Returns the HTTP response.
    """
    pass

  @abstractmethod
  def repository_mirror(self, repository):
    """ Posts the given repository to the repo mirror for processing, blocking until complete.
        Returns the analysis version on success or raises an exception deriving from
        AnalyzeLayerException on failure. Callers should handle all cases of AnalyzeLayerException.
    """
    pass

  @abstractmethod
  def get_repository_data(self, repository):
    """ Returns the layer data for the specified layer. On error, returns None. """
    pass


@nooper
class NoopRepoMirrorAPI(RepoMirrorAPIInterface):
  """ No-op version of the repo mirror API. """
  pass


class ImplementedRepoMirrorAPI(RepoMirrorAPIInterface):
  """ Helper class for talking to the repo mirror service. """
  def __init__(self, config, server_hostname, client=None, instance_keys=None):
    self._config = config
    self._instance_keys = instance_keys
    self._client = client
    self._server_hostname = server_hostname

  def repository_mirror(self, repository):
    """ Posts the given repository and config information to the mirror endpoint, blocking until complete.
        Returns the results on success or raises an exception.
    """
    def _response_json(request, response):
      try:
        return response.json()
      except ValueError:
        logger.exception('Failed to decode JSON when analyzing layer %s', request['Layer']['Name'])
        raise RepoMirrorException

    return

  def get_repository_data(self, repository):
    """ Returns the layer data for the specified layer. On error, returns None. """
    return None

  def ping(self):
    """ Calls GET on the metrics endpoint of the repository mirror to ensure it is running
        and properly configured. Returns the HTTP response.
    """
    try:
      return self._call('GET', _API_METHOD_PING)
    except requests.exceptions.Timeout as tie:
      logger.exception('Timeout when trying to connect to repository mirror endpoint')
      msg = 'Timeout when trying to connect to repository mirror endpoint: %s' % tie.message
      raise Exception(msg)
    except requests.exceptions.ConnectionError as ce:
      logger.exception('Connection error when trying to connect to repository mirror endpoint')
      msg = 'Connection error when trying to connect to repository mirror endpoint: %s' % ce.message
      raise Exception(msg)
    except (requests.exceptions.RequestException, ValueError) as ve:
      logger.exception('Exception when trying to connect to repository mirror endpoint')
      msg = 'Exception when trying to connect to repository mirror endpoint: %s' % ve
      raise Exception(msg)