import boto.rds2
import logging

logger = logging.getLogger(__name__)

class HealthCheck(object):
  def __init__(self):
    pass

  def conduct_healthcheck(self, db_healthy, buildlogs_healthy, registry_healthy):
    """
    Conducts any custom healthcheck work, returning a dict representing the HealthCheck
    output and a boolean indicating whether the instance is healthy.
    """
    raise NotImplementedError

  @classmethod
  def get_check(cls, name, parameters):
    for subc in cls.__subclasses__():
      if subc.check_name() == name:
        return subc(**parameters)

    raise Exception('Unknown health check with name %s' % name)


class LocalHealthCheck(HealthCheck):
  def __init__(self):
    pass

  @classmethod
  def check_name(cls):
    return 'LocalHealthCheck'

  def conduct_healthcheck(self, db_healthy, buildlogs_healthy, registry_healthy):
    data = {
      'db_healthy': db_healthy,
      'buildlogs_healthy': buildlogs_healthy,
      'registry_healthy': registry_healthy
    }

    return (data, db_healthy and buildlogs_healthy)


class ProductionHealthCheck(HealthCheck):
  def __init__(self, access_key, secret_key):
    self.access_key = access_key
    self.secret_key = secret_key

  @classmethod
  def check_name(cls):
    return 'ProductionHealthCheck'

  def conduct_healthcheck(self, db_healthy, buildlogs_healthy, registry_healthy):
    data = {
      'db_healthy': db_healthy,
      'buildlogs_healthy': buildlogs_healthy,
      'registry_healthy': registry_healthy
    }

    # Only report unhealthy if the machine cannot connect to the DB. Redis isn't required for
    # mission critical/high avaliability operations.
    if not db_healthy:
      # If the database is marked as unhealthy, check the status of RDS directly. If RDS is
      # reporting as available, then the problem is with this instance. Otherwise, the problem is
      # with RDS, and we can keep this machine as 'healthy'.
      is_rds_working = False
      try:
        region = boto.rds2.connect_to_region('us-east-1',
          aws_access_key_id=self.access_key, aws_secret_access_key=self.secret_key)
        response = region.describe_db_instances()['DescribeDBInstancesResponse']
        result = response['DescribeDBInstancesResult']
        instances = result['DBInstances']
        status = instances[0]['DBInstanceStatus']
        is_rds_working = status == 'available'
      except:
        logger.exception("Exception while checking RDS status")
        pass

      data['db_available_checked'] = True
      data['db_available_status'] = is_rds_working

      # If RDS is down, then we still report the machine as healthy, so that it can handle
      # requests once RDS comes back up.
      return (data, not is_rds_working and registry_healthy)

    return (data, db_healthy and registry_healthy)