from datetime import datetime
from typing import Union


def parse_timestamp(timestamp: Union[int, str], fmt: str = '%Y-%m-%d %H:%M:%S') -> str:
    if isinstance(timestamp, str):
        timestamp = int(timestamp)
    return datetime.fromtimestamp(timestamp).strftime(fmt)


def format_size(bytes_size: int) -> str:
    for unit in ['B', 'KB', 'MB', 'GB']:
        if bytes_size < 1024.0:
            return f"{bytes_size:.2f} {unit}"
        bytes_size /= 1024.0
    return f"{bytes_size:.2f} TB"


def format_duration(seconds: int) -> str:
    hours, remainder = divmod(seconds, 3600)
    minutes, seconds = divmod(remainder, 60)
    if hours > 0:
        return f"{hours:02d}:{minutes:02d}:{seconds:02d}"
    return f"{minutes:02d}:{seconds:02d}"