#!/usr/bin/env python
"""Filesystem Utilities

Convenience functions for dealing with paths and filesystem operations
that are somewhat complex and common to different utilities.
"""

import os

# Extra Path utilities

def normalize_path(path):
    """Takes a path, and returns a Unicode normalized path (env vars and ~ expanded)"""
    path = os.path.expandvars(path)
    path = os.path.expanduser(path)
    path = unicode(os.path.abspath(path))
    return path

def extension_of(path):
    """Returns the extension of the given path."""
    spl = path.split('.')
    if spl[-1] in ('gz', 'bz2'):
        if spl[-2] == 'tar':
            return '.'.join(spl[-2:])
    return spl[-1]

def paths_to_list(paths, recursive=False):
    """Turns a list of paths (each which can contain env vars, ~user, and
        directories) into a list of unicode absolute paths."""
    if not isinstance(paths, list): paths = [paths]
    l = []
    for path in paths:
        if os.path.isdir(path):
            l += directory_to_list(path, recursive)
        else:
            l.append(normalize_path(path))
    return l

def directory_to_list(path, recursive=False):
    """Takes a path that is a directory and returns the filenames in a list.

    If recursive is True, it returns a recursive list of _file_ paths
    """
    paths = []
    path = normalize_path(path)
    entries = os.listdir(path)
    opj = os.path.join
    files = [opj(path, entry) for entry in entries if os.path.isfile(opj(path, entry)) and not entry.startswith('.')]
    if recursive:
        directories = [opj(path, entry) for entry in entries if os.path.isdir(opj(path, entry)) and not entry.startswith('.')]
        for directory in directories:
            files += directory_to_list(opj(path, directory), recursive=True)
    return files

def filter_by_types(pathlist, types):
    """Takes a list of paths and filters out the extensions in 'types'"""
    return [path for path in pathlist if extension_of(path) in types]