"""Base classes for formatters.
"""

import abc


class Formatter(object):
    __metaclass__ = abc.ABCMeta

    @abc.abstractmethod
    def add_argument_group(self, parser):
        """Add any options to the argument parser.

        Should use our own argument group.
        """


class ListFormatter(Formatter):
    """Base class for formatters that know how to deal with multiple objects.
    """
    __metaclass__ = abc.ABCMeta

    @abc.abstractmethod
    def emit_list(self, column_names, data, stdout, parsed_args):
        """Format and print the list from the iterable data source.

        :param column_names: names of the columns
        :param data: iterable data source, one tuple per object
                     with values in order of column names
        :param stdout: output stream where data should be written
        :param parsed_args: argparse namespace from our local options
        """


class SingleFormatter(Formatter):
    """Base class for formatters that work with single objects.
    """
    __metaclass__ = abc.ABCMeta

    @abc.abstractmethod
    def emit_one(self, column_names, data, stdout, parsed_args):
        """Format and print the values associated with the single object.

        :param column_names: names of the columns
        :param data: iterable data source with values in order of column names
        :param stdout: output stream where data should be written
        :param parsed_args: argparse namespace from our local options
        """