def map_v2_event_into_v1(event):
    '''
    Helper method to convert Sensu 2.x event into Sensu 1.x event.
    '''
    if "v2_event_mapped_into_v1" in event:
        return event
    if not bool(event.get('client')) and "entity" in event:
        event['client'] = event['entity']
        if "name" not in event['client']:
            event['client']['name'] = event['entity']['id']
        if "subscribers" not in event['client']:
            event['client']['subscribers'] = event['entity']['subscriptions']
        if "subscribers" not in event['check']:
            event['check']['subscribers'] = event['check']['subscriptions']
        if "source" not in event['check']:
            event['check']['source'] = event['check']['proxy_entity_id']
        action_state_mapping = {'flapping': 'flapping', 'passing': 'resolve',
                                'failing': 'create'}
        if "state" in event['check']:
            state = event['check']['state']
        else:
            state = "unknown::2.0_event"
        if "action" not in event and state.lower() in action_state_mapping:
            event['action'] = action_state_mapping[state.lower()]
        else:
            event['action'] = state
        if "history" in event['check']:
            event['check']['history_v2'] = deepcopy(event['check']['history'])
            legacy_history = []
            for history in event['check']['history']:
                if isinstance(history['status'], int):
                    legacy_history.append(str(history['status']))
                else:
                    legacy_history.append("3")
            event['check']['history'] = legacy_history
        event['v2_event_mapped_into_v1'] = True
    return event