796ed0483627866631f763498bc30caee603cfcd
[wolnelektury.git] / src / catalogue / helpers.py
1 # This file is part of Wolnelektury, licensed under GNU Affero GPLv3 or later.
2 # Copyright © Fundacja Nowoczesna Polska. See NOTICE for more information.
3 #
4 from django.conf import settings
5 from django.contrib.contenttypes.models import ContentType
6 from django.core.cache import cache
7
8 from .models import Tag, Book
9 from os.path import getmtime
10 import pickle
11 from collections import defaultdict
12
13
14 BOOK_CATEGORIES = ('author', 'epoch', 'genre', 'kind')
15
16 _COUNTERS = None
17 _COUNTER_TIME = 0
18
19
20 def get_top_level_related_tags(tags, categories=None):
21     """
22     Finds tags related to given tags through books, and counts their usage.
23
24     Takes ancestry into account: if a tag is applied to a book, its
25     usage on the book's descendants is ignored.
26     """
27     global _COUNTERS, _COUNTER_TIME
28     # First, check that we have a valid and recent version of the counters.
29     if getmtime(settings.CATALOGUE_COUNTERS_FILE) > _COUNTER_TIME:
30         for i in range(10):
31             try:
32                 with open(settings.CATALOGUE_COUNTERS_FILE, 'rb') as f:
33                     _COUNTERS = pickle.load(f)
34             except (EOFError, ValueError):
35                 if i < 9:
36                     continue
37                 else:
38                     raise
39             else:
40                 break
41
42     tagids = tuple(sorted(t.pk for t in tags))
43     try:
44         related_ids = _COUNTERS['next'][tagids]
45     except KeyError:
46         return
47
48     related = Tag.objects.filter(pk__in=related_ids)
49
50     if categories is not None:
51         related = related.filter(category__in=categories)
52
53     for tag in related:
54         tag.count = _COUNTERS['count'][tuple(sorted(tagids + (tag.pk,)))]
55         yield tag
56
57
58 def update_counters():
59     def combinations(things):
60         if len(things):
61             for c in combinations(things[1:]):
62                 yield c
63                 yield (things[0],) + c
64         else:
65             yield ()
66
67     def count_for_book(book, count_by_combination=None, parent_combinations=None):
68         if not parent_combinations:
69             parent_combinations = set()
70         tags = sorted(book.tags.filter(category__in=('author', 'genre', 'epoch', 'kind')).values_list('pk', flat=True))
71         combs = list(combinations(tags))
72         for c in combs:
73             if c not in parent_combinations:
74                 count_by_combination[c] += 1
75         combs_for_child = set(list(parent_combinations) + combs)
76         for child in book.children.all():
77             count_for_book(child, count_by_combination, combs_for_child)
78
79     count_by_combination = defaultdict(lambda: 0)
80     for b in Book.objects.filter(parent=None):
81         count_for_book(b, count_by_combination)
82
83     next_combinations = defaultdict(set)
84     # Now build an index of all combinations.
85     for c in count_by_combination.keys():
86         if not c:
87             continue
88         for n in c:
89             rest = tuple(x for x in c if x != n)
90             next_combinations[rest].add(n)
91
92     counters = {
93         "count": dict(count_by_combination),
94         "next": dict(next_combinations),
95     }
96
97     with open(settings.CATALOGUE_COUNTERS_FILE, 'wb') as f:
98         pickle.dump(counters, f)
99
100
101 def get_audiobook_tags():
102     audiobook_tag_ids = cache.get('audiobook_tags')
103     if audiobook_tag_ids is None:
104         books_with_audiobook = Book.objects.filter(media__type__in=('mp3', 'ogg'))\
105             .distinct().values_list('pk', flat=True)
106         audiobook_tag_ids = Tag.objects.filter(
107             items__content_type=ContentType.objects.get_for_model(Book),
108             items__object_id__in=list(books_with_audiobook)).distinct().values_list('pk', flat=True)
109         audiobook_tag_ids = list(audiobook_tag_ids)
110         cache.set('audiobook_tags', audiobook_tag_ids)
111     return audiobook_tag_ids