import logging
import etcd

logger = logging.getLogger(__name__)


class EtcdCanceller(object):
  """ A class that sends a message to etcd to cancel a build """

  def __init__(self, config):
    etcd_host = config.get('ETCD_HOST', '127.0.0.1')
    etcd_port = config.get('ETCD_PORT', 2379)
    etcd_ca_cert = config.get('ETCD_CA_CERT', None)
    etcd_auth = config.get('ETCD_CERT_AND_KEY', None)
    if etcd_auth is not None:
      etcd_auth = tuple(etcd_auth)

    etcd_protocol = 'http' if etcd_auth is None else 'https'
    logger.debug('Connecting to etcd on %s:%s', etcd_host, etcd_port)
    self._cancel_prefix = config.get('ETCD_CANCEL_PREFIX', 'cancel/')
    self._etcd_client = etcd.Client(
      host=etcd_host,
      port=etcd_port,
      cert=etcd_auth,
      ca_cert=etcd_ca_cert,
      protocol=etcd_protocol,
      read_timeout=5)

  def try_cancel_build(self, build_uuid):
    """ Writes etcd message to cancel build_uuid. """
    logger.info("Cancelling build %s".format(build_uuid))
    try:
      self._etcd_client.write("{}{}".format(self._cancel_prefix, build_uuid), build_uuid, ttl=0)
      return True
    except etcd.EtcdException:
      logger.exception("Failed to write to etcd client %s", build_uuid)
      return False