import redis
import json


class BuildLogs(object):
  def __init__(self, redis_host):
    self._redis = redis.StrictRedis(host=redis_host)

  @staticmethod
  def _logs_key(build_id):
    return 'builds/%s/logs' % build_id

  def append_log_entry(self, build_id, log_obj):
    """
    Appends the serialized form of log_obj to the end of the log entry list
    and returns the new length of the list.
    """
    return self._redis.rpush(self._logs_key(build_id), json.dumps(log_obj))

  def append_log_message(self, build_id, log_message):
    """
    Wraps the message in an envelope and push it to the end of the log entry
    list and returns the new length of the list.
    """
    log_obj = {
      'message': log_message
    }
    return self._redis.rpush(self._logs_key(build_id), json.dumps(log_obj))

  def get_log_entries(self, build_id, start_index, end_index):
    """ 
    Returns a tuple of the current length of the list and an iterable of the
    requested log entries. End index is inclusive.
    """
    llen = self._redis.llen(self._logs_key(build_id))
    log_entries = self._redis.lrange(self._logs_key(build_id), start_index,
                                     end_index)
    return (llen, (json.loads(entry) for entry in log_entries))

  @staticmethod
  def _status_key(build_id):
    return 'builds/%s/status' % build_id

  def set_status(self, build_id, status_obj):
    """
    Sets the status key for this build to json serialized form of the supplied
    obj.
    """
    self._redis.set(self._status_key(build_id), json.dumps(status_obj))

  def get_status(self, build_id):
    """
    Loads the status information for the specified build id.
    """
    fetched = self._redis.get(self._status_key(build_id))
    return json.loads(fetched) if fetched else None