'''Base formatter class.'''

from abc import ABC, abstractmethod
from typing import Any, Optional, TextIO


class OutputFormatter(ABC):
    '''Abstract base class for output formatters.'''

    def __init__(self, output: Optional[TextIO] = None):
        self.output = output

    @abstractmethod
    def format(self, data: Any) -> str:
        '''Format data for output.'''
        pass

    def write(self, text: str) -> None:
        '''Write to output stream.'''
        if self.output:
            self.output.write(text)
        else:
            print(text, end="")

    def flush(self) -> None:
        '''Flush output stream.'''
        if self.output:
            self.output.flush()