summaryrefslogtreecommitdiff
path: root/raphodo/utilities.py
blob: 838709cecda59fd65f153923996dac1da31df704 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
# Copyright (C) 2007-2017 Damon Lynch <damonlynch@gmail.com>

# This file is part of Rapid Photo Downloader.
#
# Rapid Photo Downloader is free software: you can redistribute it and/or
# modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# Rapid Photo Downloader is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with Rapid Photo Downloader.  If not,
# see <http://www.gnu.org/licenses/>.

__author__ = 'Damon Lynch'
__copyright__ = "Copyright 2007-2017, Damon Lynch"

import contextlib
import locale
import logging
import os
import random
import re
import string
import sys
import tempfile
import time
import tarfile
from collections import namedtuple, defaultdict
from datetime import datetime
from gettext import gettext as _
from itertools import groupby, zip_longest
from typing import Optional, List, Union, Any
import struct
import ctypes
import signal
import pkg_resources

import arrow
import psutil

import raphodo.__about__ as __about__


# Linux specific code to ensure child processes exit when parent dies
# See http://stackoverflow.com/questions/19447603/
# how-to-kill-a-python-child-process-created-with-subprocess-check-output-when-t/
libc = ctypes.CDLL("libc.so.6")
def set_pdeathsig(sig = signal.SIGTERM):
    def callable():
        return libc.prctl(1, sig)
    return callable


def available_cpu_count(physical_only=False) -> int:
    """
    Determine the number of CPUs available.

    A CPU is "available" if cpuset has not restricted the number of
    cpus. Portions of this code from
    http://stackoverflow.com/questions/1006289/how-to-find-out-the-number-of-
    cpus-using-python

    :return available CPU count, or 1 if cannot be determined.
     Value guaranteed to be >= 1.
    """

    # cpuset may restrict the number of *available* processors
    available = None
    if sys.platform.startswith('linux'):
        try:
            m = re.search(r'(?m)^Cpus_allowed:\s*(.*)$',
                          open('/proc/self/status').read())
            if m:
                available = bin(int(m.group(1).replace(',', ''), 16)).count('1')
                if available > 0 and not physical_only:
                    return available
        except IOError:
            pass

    if physical_only:
        physical = psutil.cpu_count(logical=False)
        if physical is not None:
            if available is not None:
                return min(available, physical)
            return physical

    c = os.cpu_count()
    if c is not None:
        return max(c, 1)
    c = psutil.cpu_count()
    if c is not None:
        return max(c, 1)
    else:
        return 1

def confirm(prompt: Optional[str]=None, resp: Optional[bool]=False) -> bool:
    r"""
    Prompts for yes or no response from the user.

    :param prompt: prompt displayed to user
    :param resp: the default value assumed by the caller when user
     simply types ENTER.
    :return: True for yes and False for no.
    """

    # >>> confirm(prompt='Create Directory?', resp=True)
    # Create Directory? [y]|n:
    # True
    # >>> confirm(prompt='Create Directory?', resp=False)
    # Create Directory? [n]|y:
    # False
    # >>> confirm(prompt='Create Directory?', resp=False)
    # Create Directory? [n]|y: y
    # True

    if prompt is None:
        prompt = 'Confirm'

    if resp:
        prompt = '%s [%s]|%s: ' % (prompt, 'y', 'n')
    else:
        prompt = '%s [%s]|%s: ' % (prompt, 'n', 'y')

    while True:
        ans = input(prompt)
        if not ans:
            return resp
        if ans not in ['y', 'Y', 'n', 'N']:
            print('please enter y or n.')
            continue
        return ans in ['y', 'Y']


@contextlib.contextmanager
def stdchannel_redirected(stdchannel, dest_filename):
    """
    A context manager to temporarily redirect stdout or stderr

    Usage:
    with stdchannel_redirected(sys.stderr, os.devnull):
       do_work()

    Source:
    http://marc-abramowitz.com/archives/2013/07/19/python-context-manager-for-redirected-stdout-and-stderr/
    """
    oldstdchannel = dest_file = None
    try:
        oldstdchannel = os.dup(stdchannel.fileno())
        dest_file = open(dest_filename, 'w')
        os.dup2(dest_file.fileno(), stdchannel.fileno())
        yield
    finally:
        if oldstdchannel is not None:
            os.dup2(oldstdchannel, stdchannel.fileno())
        if dest_file is not None:
            dest_file.close()

@contextlib.contextmanager
def show_errors():
    yield

# Translators: these values are file size suffixes like B representing bytes, KB representing
# kilobytes, etc.
suffixes = [_('B'), _('KB'), _('MB'), _('GB'), _('TB'), _('PB'), _('EB'), _('ZB'), _('YB')]

def format_size_for_user(size_in_bytes: int, 
                         zero_string: str='', 
                         no_decimals: int=2) -> str:
    r"""
    Humanize display of bytes.

    Uses Microsoft style i.e. 1000 Bytes = 1 KB

    :param size: size in bytes
    :param zero_string: string to use if size == 0

    >>> locale.setlocale(locale.LC_ALL, ('en_US', 'utf-8'))
    'en_US.UTF-8'
    >>> format_size_for_user(0)
    ''
    >>> format_size_for_user(1)
    '1 B'
    >>> format_size_for_user(123)
    '123 B'
    >>> format_size_for_user(1000)
    '1 KB'
    >>> format_size_for_user(1024)
    '1.02 KB'
    >>> format_size_for_user(1024, no_decimals=0)
    '1 KB'
    >>> format_size_for_user(1100, no_decimals=2)
    '1.1 KB'
    >>> format_size_for_user(1000000, no_decimals=2)
    '1 MB'
    >>> format_size_for_user(1000001, no_decimals=2)
    '1 MB'
    >>> format_size_for_user(1020001, no_decimals=2)
    '1.02 MB'
    """

    if size_in_bytes == 0: return zero_string
    i = 0
    while size_in_bytes >= 1000 and i < len(suffixes)-1:
        size_in_bytes /= 1000
        i += 1

    if no_decimals:
        s = '{:.{prec}f}'.format(size_in_bytes, prec=no_decimals).rstrip('0').rstrip('.')
    else:
        s = '{:.0f}'.format(size_in_bytes)
    return s + ' ' + suffixes[i]

def divide_list(source: list, no_pieces: int) -> list:
    r"""
    Returns a list containing no_pieces lists, with the items
    of the original list evenly distributed
    :param source: the list to divide
    :param no_pieces: the nubmer of pieces the lists
    :return: the new list

    >>> divide_list(list(range(12)), 4)
    [[0, 1, 2], [3, 4, 5], [6, 7, 8], [9, 10, 11]]
    >>> divide_list(list(range(11)), 4)
    [[0, 1, 2], [3, 4, 5], [6, 7, 8], [9, 10]]
    """
    source_size = len(source)
    slice_size = source_size // no_pieces
    remainder = source_size % no_pieces
    result = []

    extra = 0
    for i in range(no_pieces):
        start = i * slice_size + extra
        source_slice = source[start:start + slice_size]
        if remainder:
            source_slice += [source[start + slice_size]]
            remainder -= 1
            extra += 1
        result.append(source_slice)
    return result

def divide_list_on_length(source: List, length: int) -> List:

    r"""
    Break a list into lists no longer than length.

    >>> l=list(range(11))
    >>> divide_list_on_length(l, 3)
    [[0, 1, 2], [3, 4, 5], [6, 7, 8], [9, 10]]
    >>> l=list(range(12))
    >>> divide_list_on_length(l, 3)
    [[0, 1, 2], [3, 4, 5], [6, 7, 8], [9, 10, 11]]
    """

    return [source[i:i+length] for i in range(0, len(source), length)]

def addPushButtonLabelSpacer(s: str) -> str:
    return ' ' + s


class GenerateRandomFileName:
    def __init__(self):
        # the characters used to generate temporary filenames
        self.filename_characters = list(string.ascii_letters + string.digits)

    def name(self, extension: str=None) -> str:
        """

        :return: filename 5 characters long without any extension
        """
        if extension is not None:
            return '{}.{}'.format(''.join(
                random.sample(self.filename_characters, 5)),
                extension)
        else:
            return ''.join(random.sample(self.filename_characters, 5))


TempDirs = namedtuple('TempDirs', 'photo_temp_dir, video_temp_dir')
CacheDirs = namedtuple('CacheDirs', 'photo_cache_dir, video_cache_dir')


def create_temp_dir(folder: Optional[str]=None,
                    prefix: Optional[str]=None,
                    force_no_prefix: bool=False) -> str:
    """
    Creates a temporary director and logs errors
    :param folder: the folder in which the temporary directory should
     be created. If not specified, uses the tempfile.mkstemp default.
    :param prefix: any name the directory should start with. If None,
     default rpd-tmp will be used as prefix, unless force_no_prefix
     is True
    :param force_no_prefix: if True, a directory prefix will never
     be used
    :return: full path of the temporary directory
    """
    if prefix is None and not force_no_prefix:
        prefix = "rpd-tmp-"
    try:
        temp_dir = tempfile.mkdtemp(prefix=prefix, dir=folder)
    except OSError as inst:
        msg = "Failed to create temporary directory in %s: %s %s" % (
                      folder,
                      inst.errno,
                      inst.strerror)
        logging.critical(msg)
        temp_dir = None
    return temp_dir


def create_temp_dirs(photo_download_folder: str,
                     video_download_folder: str) -> TempDirs:
    """
    Create pair of temporary directories for photo and video download
    :param photo_download_folder: where photos will be downloaded to
    :param video_download_folder: where videos will be downloaded to
    :return: the directories
    """
    photo_temp_dir = video_temp_dir = None
    if photo_download_folder is not None:
        photo_temp_dir = create_temp_dir(photo_download_folder)
        logging.debug("Photo temporary directory: %s", photo_temp_dir)
    if video_download_folder is not None:
        video_temp_dir = create_temp_dir(video_download_folder)
        logging.debug("Video temporary directory: %s", video_temp_dir)
    return TempDirs(photo_temp_dir, video_temp_dir)


def same_device(file1: str, file2: str) -> bool:
    """
    Returns True if the files / directories are on the same device (partition).

    No error checking.

    :param file1: first file / directory to check
    :param file2: second file / directory to check
    :return: True if the same file system, else false
    """

    dev1 = os.stat(file1).st_dev
    dev2 = os.stat(file2).st_dev
    return dev1 == dev2


def find_mount_point(path: str) -> str:
    """
    Find the mount point of a path
    See:
    http://stackoverflow.com/questions/4453602/how-to-find-the-mountpoint-a-file-resides-on
    
    >>> print(find_mount_point('/crazy/path'))
    /
    
    :param path: 
    :return: 
    """
    path = os.path.realpath(path)
    while not os.path.ismount(path):
        path = os.path.dirname(path)
    return path


def make_internationalized_list(items: List[str]) -> str:
    r"""
    Makes a string of items conforming to i18n

    >>> print(make_internationalized_list([]))
    <BLANKLINE>
    >>> print(make_internationalized_list(['one']))
    one
    >>> print(make_internationalized_list(['one', 'two']))
    one and two
    >>> print(make_internationalized_list(['one', 'two', 'three']))
    one, two and three
    >>> print(make_internationalized_list(['one', 'two', 'three', 'four']))
    one, two, three and four

    Loosely follows the guideline here:
    http://cldr.unicode.org/translation/lists

    :param items: the list of items to make a string out of
    :return: internationalized string
    """
    if len(items) == 1:
        return items[0]
    if len(items) == 2:
        # two things in a list e.g. "device1 and device2"
        return _('%(first_item)s and %(last_item)s') % dict(
            first_item=items[0], last_item=items[1])
    if len(items) > 2:
        s = items[0]
        for item in items[1:-1]:
            # the middle of a list of things
            s =  '%(first_items)s, %(last_items)s'% dict(first_items=s,
                                                         last_items=item)
        # the end of a list of things
        s = '%(start_items)s and %(last_item)s' % dict(start_items=s,
                                                       last_item=items[-1])
        return s
    return ''


def thousands(i: int) -> str:
    """
    Add a thousands seperator (or its locale equivalent) to an
    integer. Assumes the module level locale setting has already been
    set.
    :param i: the integer e.g. 1000
    :return: string with seperators e.g. '1,000'
    """
    try:
        return locale.format("%d", i, grouping=True)
    except TypeError:
        return i


# Source of class AdjacentKey, first_and_last and runs:
# http://stupidpythonideas.blogspot.com/2014/01/grouping-into-runs-of-adjacent-values.html
class AdjacentKey:
    r"""
    >>> [list(g) for k, g in groupby([0, 1, 2, 3, 5, 6, 7, 10, 11, 13, 16], AdjacentKey)]
    [[0, 1, 2, 3], [5, 6, 7], [10, 11], [13], [16]]
    """
    __slots__ = ['obj']

    def __init__(self, obj) -> None:
        self.obj = obj

    def __eq__(self, other) -> bool:
        ret = self.obj - 1 <= other.obj <= self.obj + 1
        if ret:
            self.obj = other.obj
        return ret


def first_and_last(iterable):
    start = end = next(iterable)
    for end in iterable: pass
    return start, end


def runs(iterable):
    r"""
    identify adjacent elements in pre-sorted data

    :param iterable: sorted data

    >>> list(runs([0, 1, 2, 3, 5, 6, 7, 10, 11, 13, 16]))
    [(0, 3), (5, 7), (10, 11), (13, 13), (16, 16)]
    >>> list(runs([0]))
    [(0, 0)]
    >>> list(runs([0, 1, 10, 100, 101]))
    [(0, 1), (10, 10), (100, 101)]
    """

    for k, g in groupby(iterable, AdjacentKey):
        yield first_and_last(g)

numbers = namedtuple('numbers', 'number, plural')

long_numbers = {
    1: _('one'),
    2: _('two'),
    3: _('three'),
    4: _('four'),
    5: _('five'),
    6: _('six'),
    7: _('seven'),
    8: _('eight'),
    9: _('nine'),
    10: _('ten'),
    11: _('eleven'),
    12: _('twelve'),
    13: _('thirteen'),
    14: _('fourteen'),
    15: _('fifteen'),
    16: _('sixteen'),
    17: _('seventeen'),
    18: _('eighteen'),
    19: _('ninenteen'),
    20: _('twenty')
}


def number(value: int) -> numbers:
    r"""
    Convert integer to written form, e.g. one, two, etc.

    Will propagate TypeError or KeyError on
    failure.

    >>> number(1)
    numbers(number='one', plural=False)
    >>> number(2)
    numbers(number='two', plural=True)
    >>> number(10)
    numbers(number='ten', plural=True)
    >>> number(20)
    numbers(number='twenty', plural=True)
    >>>

    :param value: int between 1 and 20
    :return: tuple of str and whether it is plural
    """

    plural = value > 1
    text = long_numbers[value]
    return numbers(text, plural)


def datetime_roughly_equal(dt1: Union[datetime, float], dt2: Union[datetime, float],
                           seconds: int=120) -> bool:
    r"""
    Check to see if date times are equal, give or take n seconds
    :param dt1: python datetime, or timestamp, to check
    :param dt2:python datetime, or timestamp to check
    :param seconds: number of seconds leeway
    :return: True if "equal", False otherwise

    >>> dt1 = datetime.now()
    >>> time.sleep(.1)
    >>> dt2 = datetime.now()
    >>> datetime_roughly_equal(dt1, dt2, 1)
    True
    >>> dt1 = 1458561776.0
    >>> dt2 = 1458561776.0
    >>> datetime_roughly_equal(dt1, dt2, 120)
    True
    >>> dt2 += 450
    >>> datetime_roughly_equal(dt1, dt2, 120)
    False
    >>> datetime_roughly_equal(dt1, dt2, 500)
    True
    """

    at1 = arrow.get(dt1)
    at2 = arrow.get(dt2)
    return at1.replace(seconds=-seconds) < at2 < at1.replace(seconds=+seconds)


def process_running(process_name: str, partial_name: bool=True) -> bool:
    """
    Search the list of the system's running processes to see if a process with this
    name is running

    :param process_name: the name of the process to search for
    :param partial_name: if True, the process_name argument can be a
     partial match
    :return: True if found, else False
    """

    for proc in psutil.process_iter():
        try:
            name = proc.name()
        except psutil.NoSuchProcess:
            pass
        else:
            if partial_name:
                if name.find(process_name) >= 0:
                    return True
            else:
                if name == process_name:
                    return True
    return False

def make_html_path_non_breaking(path: str) -> str:
    """
    When /some/path is displayed in rich text, it will be word-wrapped on the
    slashes. Inhibit that using a special unicode character.

    :param path: the path
    :return: the path containing the special characters
    """

    return path.replace(os.sep, '{}&#8288;'.format(os.sep))


def prefs_list_from_gconftool2_string(value: str) -> List[str]:
    r"""
    Take a raw string preference value as returned by gconftool-2
    and convert it to a list of strings.

    Handles escaped characters

    :param value: the raw value as returned by gconftool-2
    :return: the list of strings

    >>> prefs_list_from_gconftool2_string( # doctest: +ELLIPSIS
    ... '[Text,IMG_,,Sequences,Stored number,Four digits,Filename,Extension,UPPERCASE]')
    ... # doctest: +NORMALIZE_WHITESPACE
    ['Text', 'IMG_', '', 'Sequences', 'Stored number', 'Four digits', 'Filename', 'Extension',
    'UPPERCASE']
    >>> prefs_list_from_gconftool2_string('[Text,IMG_\,\\;+=|!@\,#^&*()$%/",,]')
    ['Text', 'IMG_,\\;+=|!@,#^&*()$%/"', '', '']
    >>> prefs_list_from_gconftool2_string('[Manila,Dubai,London]')
    ['Manila', 'Dubai', 'London']
    """
    # Trim the left and right square brackets
    value = value[1:-1]

    # Split on the comma, but not commas that were escaped.
    # Use a regex with a negative lookbehind assertion
    splits = re.split(r'(?<!\\),', value)
    # Replace the escaped commas with just plain commas
    return [s.replace('\\,', ',') for s in splits]


def pref_bool_from_gconftool2_string(value: str) -> bool:
    if value == 'true':
        return True
    elif value == 'false':
        return False
    raise ValueError


def remove_last_char_from_list_str(items: List[str]) -> List[str]:
    r"""
    Remove the last character from a list of strings, modifying the list in place,
    such that the last item is never empty

    :param items: the list to modify
    :return: in place copy

    >>> remove_last_char_from_list_str([' abc', 'def', 'ghi'])
    [' abc', 'def', 'gh']
    >>> remove_last_char_from_list_str([' abc', 'def', 'gh'] )
    [' abc', 'def', 'g']
    >>> remove_last_char_from_list_str([' abc', 'def', 'g'] )
    [' abc', 'def']
    >>> remove_last_char_from_list_str([' a'])
    [' ']
    >>> remove_last_char_from_list_str([' '])
    []
    >>> remove_last_char_from_list_str([])
    []
    """
    if items:
        if not items[-1]:
            items = items[:-1]
        else:
            items[-1] = items[-1][:-1]
            if items and not items[-1]:
                items = items[:-1]
    return items


def platform_c_maxint() -> int:
    """
    See http://stackoverflow.com/questions/13795758/what-is-sys-maxint-in-python-3

    :return: the maximum size of an int in C when compiled the same way Python was
    """
    return 2 ** (struct.Struct('i').size * 8 - 1) - 1


def commonprefix(*paths) -> str:
    """
    Python 3.4 compatible.

    Remove when Python 3.5 becomes the minimum.
    """

    return os.path.dirname(os.path.commonprefix(paths))


def _recursive_identify_depth(*paths, depth) -> int:
    basenames = [os.path.basename(path) for path in paths]
    if len(basenames) != len(set(basenames)):
        duplicates = _collect_duplicates(basenames, paths)

        for basename in duplicates:
            chop = len(basename) + 1
            chopped = (path[:-chop] for path in duplicates[basename])
            depth = max(depth, _recursive_identify_depth(*chopped, depth=depth + 1))
    return depth


def _collect_duplicates(basenames, paths):
    duplicates = defaultdict(list)
    for basename, path in zip(basenames, paths):
        duplicates[basename].append(path)
    return {basename: paths for basename, paths in duplicates.items() if len(paths) > 1}


def make_path_end_snippets_unique(*paths) -> List[str]:
    r"""
    Make list of path ends unique given possible common path endings.  
    
    A snippet starts from the end of the path, in extreme cases possibly up the path start. 

    :param paths: sequence of paths to generate unique end snippets for
    :return: list of unique snippets
    
    >>> p0 = '/home/damon/photos'
    >>> p1 = '/media/damon/backup1/photos'
    >>> p2 = '/media/damon/backup2/photos'
    >>> p3 = '/home/damon/videos'
    >>> p4 = '/media/damon/backup1/videos'
    >>> p5 = '/media/damon/backup2/videos'
    >>> p6 = '/media/damon/drive1/home/damon/photos'
    >>> s0 = make_path_end_snippets_unique(p0, p3)
    >>> print(s0)
    ['photos', 'videos']
    >>> s1 = make_path_end_snippets_unique(p0, p1, p2)
    >>> print(s1)
    ['damon/photos', 'backup1/photos', 'backup2/photos']
    >>> s2 = make_path_end_snippets_unique(p0, p1, p2, p3)
    >>> print(s2)
    ['damon/photos', 'backup1/photos', 'backup2/photos', 'videos']
    >>> s3 = make_path_end_snippets_unique(p3, p4, p5)
    >>> print(s3)
    ['damon/videos', 'backup1/videos', 'backup2/videos']
    >>> s4 = make_path_end_snippets_unique(p0, p1, p2, p3, p6)
    >>> print(s4) #doctest: +NORMALIZE_WHITESPACE
    ['/home/damon/photos', '/media/damon/backup1/photos', '/media/damon/backup2/photos', 'videos',
     'drive1/home/damon/photos']
    >>> s5 = make_path_end_snippets_unique(p1, p2, p3, p6)
    >>> print(s5)
    ['backup1/photos', 'backup2/photos', 'videos', 'damon/photos']
    """

    basenames = [os.path.basename(path) for path in paths]

    if len(basenames) != len(set(basenames)):
        names = []
        depths = defaultdict(int)
        duplicates = _collect_duplicates(basenames, paths)

        for basename, path in zip(basenames, paths):
            if basename in duplicates:
                depths[basename] = _recursive_identify_depth(*duplicates[basename], depth=0)

        for basename, path in zip(basenames, paths):
            depth = depths[basename]
            if depth:
                dirs = path.split(os.sep)
                index = len(dirs) - depth - 1
                name = (os.sep.join(dirs[max(index, 0): ]))
                if index > 1:
                    pass
                    # name = '...' + name
                elif index == 1:
                    name = os.sep + name
            else:
                name = basename
            names.append(name)
        return names
    else:
        return basenames

have_logged_os_release = False


def log_os_release() -> None:
    """
    Log the entired contents of /etc/os-release, but only if
    we didn't do so already.
    """

    global have_logged_os_release

    if not have_logged_os_release:
        try:
            with open('/etc/os-release', 'r') as f:
                for line in f:
                    logging.debug(line.rstrip('\n'))
        except:
            pass
        have_logged_os_release = True


def extract_file_from_tar(full_tar_path, member_filename) -> bool:
    """
    Extracts a file from a tar.gz and places it beside the tar file
    :param full_tar_path: path and filename of the tar.gz file
    :param member_filename: file wanted
    :return: True if successful, False otherwise
    """

    tar_dir, tar_name = os.path.split(full_tar_path)
    tar_name = tar_name[:len('.tar.gz') * -1]
    member = os.path.join(tar_name, member_filename)
    try:
        with tarfile.open(full_tar_path) as tar:
            tar.extractall(members=(tar.getmember(member),), path=tar_dir)
    except Exception:
        logging.error('Unable to extract %s from tarfile', member_filename)
        return False
    else:
        try:
            src = os.path.join(tar_dir, tar_name, member_filename)
            dst = os.path.join(tar_dir, member_filename)
            os.rename(src, dst)
            os.rmdir(os.path.join(tar_dir, tar_name))
            return True
        except OSError:
            logging.error('Unable to move %s to new location', member_filename)
            return False


def current_version_is_dev_version(current_version=None) -> bool:
    if current_version is None:
        current_version = pkg_resources.parse_version(__about__.__version__)
    return current_version.is_prerelease


def remove_topmost_directory_from_path(path: str) -> str:
    if os.sep not in path:
        return path
    return path[path[1:].find(os.sep) + 1:]


def arrow_locale() -> str:
    """
    Test if locale is suitable for use with Arrow.
    :return: Return user locale if it works with Arrow, else Arrow default ('en_us')
    """

    default = 'en_us'
    try:
        lang = locale.getdefaultlocale()[0]
    except Exception:
        return default

    try:
        arrow.locales.get_locale(lang)
        return lang
    except (ValueError, AttributeError):
        return default


def letters(x: int) -> str:
    """
    Return a letter representation of a positive number.

    Adapted from algorithm at
    http://en.wikipedia.org/wiki/Hexavigesimal

    >>> letters(0)
    'a'
    >>> letters(1)
    'b'
    >>> letters(2)
    'c'
    >>> letters(25)
    'z'
    >>> letters(26)
    'aa'
    >>> letters(27)
    'ab'
    >>> letters(28)
    'ac'
    """

    v = ''
    while x > 25:
        r = x % 26
        x = x // 26 - 1
        v = string.ascii_lowercase[r] + v
    v = string.ascii_lowercase[x] + v

    return v