from typing import List, Optional, Dict, Tuple
from pathlib import Path


class Formatter:
    """
    A formatter is bound to a specific input file with some
    building configuration.
    """
    def format(self, build_dir: Path) -> Optional[List[Tuple[str, Dict]]]:
        """
        :param build_dir: Directory where output files are written to
        :return: When configuration files are needed for a future
        build of the output files, a list of the file names and their
        needed configurations. Else None.
        """
        pass

    @property
    def output_files(self) -> List[str]:
        """

        :return: List of files that will be built when the formatter is invoked
        """
        pass

    def set_input_file(self, locate_config=True) -> None:
        raise NotImplementedError