import logging
import datetime
import json
import hydra.settings.config

log = logging.getLogger()


def get_dynamodb_connection(region=None):
    """
    :return Connection to DynamoDB for specified region
    """

    from boto import dynamodb2, connect_dynamodb

    if region:
        return dynamodb2.connect_to_region(region)
    else:
        return connect_dynamodb()


def get_dynamodb_table_name(table_name):
    """ construct the DynamoDB table name from prefix and with time suffixes
    :param table_name: table name prefix
    :return: constructed table name, ie stage_metrics_apilog_2015_04_11_00
    """
    ref_date = datetime.datetime.utcnow().strftime("%Y_%m_%d_%H")
    complete_name = '{0}_{1}_{2}'.format(hydra.settings.config.AWS_DYNAMODB_TABLE_PREFIX,
                                         table_name,
                                         ref_date)
    return complete_name


def get_dynamodb_table(table_name, conn, region=None):
    """ construct the DynamoDB table name from prefix and with time suffixes """

    from boto.exception import JSONResponseError
    from boto.dynamodb2.table import Table

    # We had to use different type of connections here due some issues
    # https://github.com/boto/boto/issues/2762
    # with the atomic counter for the dynamodb2 classes
    try:
        if region:
            table = Table(table_name, connection=conn)
            table.describe()
        else:
            table = conn.get_table(table_name)
    except JSONResponseError, e:
        log.error("Unable to lookup DynamoDB table [%s]: %s", table_name, e)
        return None
    return table


class DatetimeEncoder(json.JSONEncoder):
    """
    Alternate handler that can serialize dates
    """
    def default(self, obj):
        if hasattr(obj, 'isoformat'):
            return obj.isoformat()
        # Let the base class default method raise the TypeError
        return json.JSONEncoder.default(self, obj)