import sys
import os

def get_basename(filepath):
    """Return the basename of given filepath.
    
    Args:
        filepath (str): path to a file
    
    Returns:
        str: basename

    >>> basename('~/an/interesting/file.txt')
    'file
    """
    return os.path.splitext(os.path.basename(filepath))[0]


def get_extension(filepath):
    """Get the extension of a filepath
    
    Args:
        filepath (str): path to a file
    
    Returns:
        str: extention of the file

    >>> extension('~/an/interesting/file.lp')
    'lp'
    >>> extension('nothing')
    ''
    >>> extension('nothing.important')
    'important'
    """
    return os.path.splitext(os.path.basename(filepath))[1][1:]


def is_valid_path(filepath):
    """Return True if filepath is valid
    
    Args:
        filepath (str): path to file
    
    Returns:
        bool: True if path exists, False otherwise
    """
    if filepath and not os.access(filepath, os.W_OK):
        try:
            open(filepath, 'w').close()
            os.unlink(filepath)
            return True
        except OSError:
            return False
    else:  # path is accessible
        return True


def is_valid_file(filepath):
    """Return True if filepath exists

    Args:
        filepath (str): path to file

    Returns:
        bool: True if path exists, False otherwise
    """
    try:
        open(filepath, 'r').close()
        return True
    except OSError:
        return False


def is_valid_dir(dirpath):
    """Return True if directory exists or can be created (then create it)
    
    Args:
        dirpath (str): path of directory

    Returns:
        bool: True if dir exists, False otherwise
    """
    if not os.path.isdir(dirpath):
        try:
            os.makedirs(dirpath)
            return True
        except OSError:
            return False
    else:
        return True

def check_program(program):
    """Check whether Pathway Tools is in the PATH

    Returns:
        bool: True if Pathway Tools is in the PATH, False otherwise
    """
    def is_exe(fpath):
        return os.path.isfile(fpath) and os.access(fpath, os.X_OK)

    if is_exe(program):
        return True
    else:
        for path in os.environ["PATH"].split(os.pathsep):
            exe_file = os.path.join(path, program)
            if is_exe(exe_file):
                return True

    return False