| commit | author | age | ||
| d579f2 | 1 | from hashlib import md5 |
| MM | 2 | from webob.acceptparse import Accept |
| 0c29cf | 3 | |
| d579f2 | 4 | from pyramid.compat import bytes_, is_nonstr_iter |
| MM | 5 | from pyramid.exceptions import ConfigurationError |
| 6 | from pyramid.interfaces import IPredicateList, PHASE1_CONFIG | |
| 7 | from pyramid.predicates import Notted | |
| 8 | from pyramid.registry import predvalseq | |
| 9 | from pyramid.util import TopologicalSorter | |
| 10 | ||
| 11 | ||
| 12 | MAX_ORDER = 1 << 30 | |
| 13 | DEFAULT_PHASH = md5().hexdigest() | |
| 14 | ||
| 15 | ||
| 16 | class PredicateConfiguratorMixin(object): | |
| 17 | def get_predlist(self, name): | |
| 18 | predlist = self.registry.queryUtility(IPredicateList, name=name) | |
| 19 | if predlist is None: | |
| 20 | predlist = PredicateList() | |
| 21 | self.registry.registerUtility(predlist, IPredicateList, name=name) | |
| 22 | return predlist | |
| 23 | ||
| 24 | def _add_predicate( | |
| 25 | self, type, name, factory, weighs_more_than=None, weighs_less_than=None | |
| 26 | ): | |
| 27 | factory = self.maybe_dotted(factory) | |
| 28 | discriminator = ('%s option' % type, name) | |
| 29 | intr = self.introspectable( | |
| 30 | '%s predicates' % type, | |
| 31 | discriminator, | |
| 32 | '%s predicate named %s' % (type, name), | |
| 33 | '%s predicate' % type, | |
| 34 | ) | |
| 35 | intr['name'] = name | |
| 36 | intr['factory'] = factory | |
| 37 | intr['weighs_more_than'] = weighs_more_than | |
| 38 | intr['weighs_less_than'] = weighs_less_than | |
| 39 | ||
| 40 | def register(): | |
| 41 | predlist = self.get_predlist(type) | |
| 42 | predlist.add( | |
| 43 | name, | |
| 44 | factory, | |
| 45 | weighs_more_than=weighs_more_than, | |
| 46 | weighs_less_than=weighs_less_than, | |
| 47 | ) | |
| 48 | ||
| 49 | self.action( | |
| 50 | discriminator, | |
| 51 | register, | |
| 52 | introspectables=(intr,), | |
| 53 | order=PHASE1_CONFIG, | |
| 54 | ) # must be registered early | |
| 55 | ||
| 56 | ||
| 57 | class not_(object): | |
| 58 | """ | |
| 59 | ||
| 60 | You can invert the meaning of any predicate value by wrapping it in a call | |
| 61 | to :class:`pyramid.config.not_`. | |
| 62 | ||
| 63 | .. code-block:: python | |
| 64 | :linenos: | |
| 65 | ||
| 66 | from pyramid.config import not_ | |
| 67 | ||
| 68 | config.add_view( | |
| 69 | 'mypackage.views.my_view', | |
| 70 | route_name='ok', | |
| 71 | request_method=not_('POST') | |
| 72 | ) | |
| 73 | ||
| 74 | The above example will ensure that the view is called if the request method | |
| 75 | is *not* ``POST``, at least if no other view is more specific. | |
| 76 | ||
| 77 | This technique of wrapping a predicate value in ``not_`` can be used | |
| 78 | anywhere predicate values are accepted: | |
| 79 | ||
| 80 | - :meth:`pyramid.config.Configurator.add_view` | |
| 81 | ||
| 82 | - :meth:`pyramid.config.Configurator.add_route` | |
| 83 | ||
| 84 | - :meth:`pyramid.config.Configurator.add_subscriber` | |
| 85 | ||
| 86 | - :meth:`pyramid.view.view_config` | |
| 87 | ||
| 88 | - :meth:`pyramid.events.subscriber` | |
| 89 | ||
| 90 | .. versionadded:: 1.5 | |
| 91 | """ | |
| 92 | ||
| 93 | def __init__(self, value): | |
| 94 | self.value = value | |
| 95 | ||
| 96 | ||
| 97 | # under = after | |
| 98 | # over = before | |
| 99 | ||
| 100 | ||
| 101 | class PredicateList(object): | |
| 102 | def __init__(self): | |
| 103 | self.sorter = TopologicalSorter() | |
| 104 | self.last_added = None | |
| 105 | ||
| 106 | def add(self, name, factory, weighs_more_than=None, weighs_less_than=None): | |
| 107 | # Predicates should be added to a predicate list in (presumed) | |
| 108 | # computation expense order. | |
| 109 | # if weighs_more_than is None and weighs_less_than is None: | |
| 110 | # weighs_more_than = self.last_added or FIRST | |
| 111 | # weighs_less_than = LAST | |
| 112 | self.last_added = name | |
| 113 | self.sorter.add( | |
| 114 | name, factory, after=weighs_more_than, before=weighs_less_than | |
| 115 | ) | |
| 116 | ||
| 117 | def names(self): | |
| 118 | # Return the list of valid predicate names. | |
| 119 | return self.sorter.names | |
| 120 | ||
| 121 | def make(self, config, **kw): | |
| 122 | # Given a configurator and a list of keywords, a predicate list is | |
| 123 | # computed. Elsewhere in the code, we evaluate predicates using a | |
| 124 | # generator expression. All predicates associated with a view or | |
| 125 | # route must evaluate true for the view or route to "match" during a | |
| 126 | # request. The fastest predicate should be evaluated first, then the | |
| 127 | # next fastest, and so on, as if one returns false, the remainder of | |
| 128 | # the predicates won't need to be evaluated. | |
| 129 | # | |
| 130 | # While we compute predicates, we also compute a predicate hash (aka | |
| 131 | # phash) that can be used by a caller to identify identical predicate | |
| 132 | # lists. | |
| 133 | ordered = self.sorter.sorted() | |
| 134 | phash = md5() | |
| 135 | weights = [] | |
| 136 | preds = [] | |
| 137 | for n, (name, predicate_factory) in enumerate(ordered): | |
| 138 | vals = kw.pop(name, None) | |
| 139 | if vals is None: # XXX should this be a sentinel other than None? | |
| 140 | continue | |
| 141 | if not isinstance(vals, predvalseq): | |
| 142 | vals = (vals,) | |
| 143 | for val in vals: | |
| 144 | realval = val | |
| 145 | notted = False | |
| 146 | if isinstance(val, not_): | |
| 147 | realval = val.value | |
| 148 | notted = True | |
| 149 | pred = predicate_factory(realval, config) | |
| 150 | if notted: | |
| 151 | pred = Notted(pred) | |
| 152 | hashes = pred.phash() | |
| 153 | if not is_nonstr_iter(hashes): | |
| 154 | hashes = [hashes] | |
| 155 | for h in hashes: | |
| 156 | phash.update(bytes_(h)) | |
| 157 | weights.append(1 << n + 1) | |
| 158 | preds.append(pred) | |
| 159 | if kw: | |
| 160 | from difflib import get_close_matches | |
| 161 | ||
| 162 | closest = [] | |
| 163 | names = [name for name, _ in ordered] | |
| 164 | for name in kw: | |
| 165 | closest.extend(get_close_matches(name, names, 3)) | |
| 166 | ||
| 167 | raise ConfigurationError( | |
| 168 | 'Unknown predicate values: %r (did you mean %s)' | |
| 169 | % (kw, ','.join(closest)) | |
| 170 | ) | |
| 171 | # A "order" is computed for the predicate list. An order is | |
| 172 | # a scoring. | |
| 173 | # | |
| 174 | # Each predicate is associated with a weight value. The weight of a | |
| 175 | # predicate symbolizes the relative potential "importance" of the | |
| 176 | # predicate to all other predicates. A larger weight indicates | |
| 177 | # greater importance. | |
| 178 | # | |
| 179 | # All weights for a given predicate list are bitwise ORed together | |
| 180 | # to create a "score"; this score is then subtracted from | |
| 181 | # MAX_ORDER and divided by an integer representing the number of | |
| 182 | # predicates+1 to determine the order. | |
| 183 | # | |
| 184 | # For views, the order represents the ordering in which a "multiview" | |
| 185 | # ( a collection of views that share the same context/request/name | |
| 186 | # triad but differ in other ways via predicates) will attempt to call | |
| 187 | # its set of views. Views with lower orders will be tried first. | |
| 188 | # The intent is to a) ensure that views with more predicates are | |
| 189 | # always evaluated before views with fewer predicates and b) to | |
| 190 | # ensure a stable call ordering of views that share the same number | |
| 191 | # of predicates. Views which do not have any predicates get an order | |
| 192 | # of MAX_ORDER, meaning that they will be tried very last. | |
| 193 | score = 0 | |
| 194 | for bit in weights: | |
| 195 | score = score | bit | |
| 196 | order = (MAX_ORDER - score) / (len(preds) + 1) | |
| 197 | return order, preds, phash.hexdigest() | |
| 198 | ||
| 199 | ||
| 200 | def normalize_accept_offer(offer, allow_range=False): | |
| 201 | if allow_range and '*' in offer: | |
| 202 | return offer.lower() | |
| 203 | return str(Accept.parse_offer(offer)) | |
| 204 | ||
| 205 | ||
| 206 | def sort_accept_offers(offers, order=None): | |
| 207 | """ | |
| 208 | Sort a list of offers by preference. | |
| 209 | ||
| 210 | For a given ``type/subtype`` category of offers, this algorithm will | |
| 211 | always sort offers with params higher than the bare offer. | |
| 212 | ||
| 213 | :param offers: A list of offers to be sorted. | |
| 214 | :param order: A weighted list of offers where items closer to the start of | |
| 215 | the list will be a preferred over items closer to the end. | |
| 216 | :return: A list of offers sorted first by specificity (higher to lower) | |
| 217 | then by ``order``. | |
| 218 | ||
| 219 | """ | |
| 220 | if order is None: | |
| 221 | order = [] | |
| 222 | ||
| 223 | max_weight = len(offers) | |
| 224 | ||
| 225 | def find_order_index(value, default=None): | |
| 226 | return next((i for i, x in enumerate(order) if x == value), default) | |
| 227 | ||
| 228 | def offer_sort_key(value): | |
| 229 | """ | |
| 230 | (type_weight, params_weight) | |
| 231 | ||
| 232 | type_weight: | |
| 233 | - index of specific ``type/subtype`` in order list | |
| 234 | - ``max_weight * 2`` if no match is found | |
| 235 | ||
| 236 | params_weight: | |
| 237 | - index of specific ``type/subtype;params`` in order list | |
| 238 | - ``max_weight`` if not found | |
| 239 | - ``max_weight + 1`` if no params at all | |
| 240 | ||
| 241 | """ | |
| 242 | parsed = Accept.parse_offer(value) | |
| 243 | ||
| 244 | type_w = find_order_index( | |
| 245 | parsed.type + '/' + parsed.subtype, max_weight | |
| 246 | ) | |
| 247 | ||
| 248 | if parsed.params: | |
| 249 | param_w = find_order_index(value, max_weight) | |
| 250 | ||
| 251 | else: | |
| 252 | param_w = max_weight + 1 | |
| 253 | ||
| 254 | return (type_w, param_w) | |
| 255 | ||
| 256 | return sorted(offers, key=offer_sort_key) | |
