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327 lines
10 KiB
327 lines
10 KiB
5 months ago
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from __future__ import annotations
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import codecs
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import re
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from .structures import ImmutableList
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class Accept(ImmutableList):
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"""An :class:`Accept` object is just a list subclass for lists of
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``(value, quality)`` tuples. It is automatically sorted by specificity
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and quality.
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All :class:`Accept` objects work similar to a list but provide extra
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functionality for working with the data. Containment checks are
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normalized to the rules of that header:
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>>> a = CharsetAccept([('ISO-8859-1', 1), ('utf-8', 0.7)])
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>>> a.best
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'ISO-8859-1'
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>>> 'iso-8859-1' in a
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True
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>>> 'UTF8' in a
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True
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>>> 'utf7' in a
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False
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To get the quality for an item you can use normal item lookup:
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>>> print a['utf-8']
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0.7
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>>> a['utf7']
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0
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.. versionchanged:: 0.5
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:class:`Accept` objects are forced immutable now.
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.. versionchanged:: 1.0.0
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:class:`Accept` internal values are no longer ordered
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alphabetically for equal quality tags. Instead the initial
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order is preserved.
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"""
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def __init__(self, values=()):
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if values is None:
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list.__init__(self)
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self.provided = False
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elif isinstance(values, Accept):
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self.provided = values.provided
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list.__init__(self, values)
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else:
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self.provided = True
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values = sorted(
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values, key=lambda x: (self._specificity(x[0]), x[1]), reverse=True
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)
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list.__init__(self, values)
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def _specificity(self, value):
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"""Returns a tuple describing the value's specificity."""
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return (value != "*",)
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def _value_matches(self, value, item):
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"""Check if a value matches a given accept item."""
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return item == "*" or item.lower() == value.lower()
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def __getitem__(self, key):
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"""Besides index lookup (getting item n) you can also pass it a string
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to get the quality for the item. If the item is not in the list, the
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returned quality is ``0``.
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"""
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if isinstance(key, str):
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return self.quality(key)
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return list.__getitem__(self, key)
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def quality(self, key):
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"""Returns the quality of the key.
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.. versionadded:: 0.6
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In previous versions you had to use the item-lookup syntax
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(eg: ``obj[key]`` instead of ``obj.quality(key)``)
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"""
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for item, quality in self:
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if self._value_matches(key, item):
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return quality
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return 0
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def __contains__(self, value):
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for item, _quality in self:
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if self._value_matches(value, item):
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return True
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return False
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def __repr__(self):
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pairs_str = ", ".join(f"({x!r}, {y})" for x, y in self)
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return f"{type(self).__name__}([{pairs_str}])"
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def index(self, key):
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"""Get the position of an entry or raise :exc:`ValueError`.
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:param key: The key to be looked up.
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.. versionchanged:: 0.5
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This used to raise :exc:`IndexError`, which was inconsistent
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with the list API.
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"""
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if isinstance(key, str):
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for idx, (item, _quality) in enumerate(self):
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if self._value_matches(key, item):
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return idx
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raise ValueError(key)
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return list.index(self, key)
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def find(self, key):
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"""Get the position of an entry or return -1.
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:param key: The key to be looked up.
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"""
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try:
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return self.index(key)
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except ValueError:
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return -1
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def values(self):
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"""Iterate over all values."""
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for item in self:
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yield item[0]
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def to_header(self):
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"""Convert the header set into an HTTP header string."""
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result = []
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for value, quality in self:
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if quality != 1:
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value = f"{value};q={quality}"
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result.append(value)
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return ",".join(result)
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def __str__(self):
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return self.to_header()
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def _best_single_match(self, match):
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for client_item, quality in self:
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if self._value_matches(match, client_item):
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# self is sorted by specificity descending, we can exit
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return client_item, quality
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return None
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def best_match(self, matches, default=None):
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"""Returns the best match from a list of possible matches based
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on the specificity and quality of the client. If two items have the
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same quality and specificity, the one is returned that comes first.
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:param matches: a list of matches to check for
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:param default: the value that is returned if none match
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"""
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result = default
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best_quality = -1
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best_specificity = (-1,)
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for server_item in matches:
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match = self._best_single_match(server_item)
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if not match:
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continue
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client_item, quality = match
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specificity = self._specificity(client_item)
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if quality <= 0 or quality < best_quality:
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continue
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# better quality or same quality but more specific => better match
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if quality > best_quality or specificity > best_specificity:
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result = server_item
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best_quality = quality
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best_specificity = specificity
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return result
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@property
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def best(self):
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"""The best match as value."""
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if self:
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return self[0][0]
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_mime_split_re = re.compile(r"/|(?:\s*;\s*)")
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def _normalize_mime(value):
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return _mime_split_re.split(value.lower())
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class MIMEAccept(Accept):
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"""Like :class:`Accept` but with special methods and behavior for
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mimetypes.
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"""
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def _specificity(self, value):
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return tuple(x != "*" for x in _mime_split_re.split(value))
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def _value_matches(self, value, item):
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# item comes from the client, can't match if it's invalid.
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if "/" not in item:
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return False
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# value comes from the application, tell the developer when it
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# doesn't look valid.
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if "/" not in value:
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raise ValueError(f"invalid mimetype {value!r}")
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# Split the match value into type, subtype, and a sorted list of parameters.
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normalized_value = _normalize_mime(value)
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value_type, value_subtype = normalized_value[:2]
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value_params = sorted(normalized_value[2:])
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# "*/*" is the only valid value that can start with "*".
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if value_type == "*" and value_subtype != "*":
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raise ValueError(f"invalid mimetype {value!r}")
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# Split the accept item into type, subtype, and parameters.
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normalized_item = _normalize_mime(item)
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item_type, item_subtype = normalized_item[:2]
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item_params = sorted(normalized_item[2:])
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# "*/not-*" from the client is invalid, can't match.
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if item_type == "*" and item_subtype != "*":
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return False
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return (
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(item_type == "*" and item_subtype == "*")
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or (value_type == "*" and value_subtype == "*")
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) or (
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item_type == value_type
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and (
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item_subtype == "*"
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or value_subtype == "*"
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or (item_subtype == value_subtype and item_params == value_params)
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)
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)
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@property
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def accept_html(self):
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"""True if this object accepts HTML."""
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return (
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"text/html" in self or "application/xhtml+xml" in self or self.accept_xhtml
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)
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@property
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def accept_xhtml(self):
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"""True if this object accepts XHTML."""
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return "application/xhtml+xml" in self or "application/xml" in self
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@property
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def accept_json(self):
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"""True if this object accepts JSON."""
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return "application/json" in self
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_locale_delim_re = re.compile(r"[_-]")
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def _normalize_lang(value):
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"""Process a language tag for matching."""
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return _locale_delim_re.split(value.lower())
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class LanguageAccept(Accept):
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"""Like :class:`Accept` but with normalization for language tags."""
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def _value_matches(self, value, item):
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return item == "*" or _normalize_lang(value) == _normalize_lang(item)
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def best_match(self, matches, default=None):
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"""Given a list of supported values, finds the best match from
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the list of accepted values.
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Language tags are normalized for the purpose of matching, but
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are returned unchanged.
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If no exact match is found, this will fall back to matching
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the first subtag (primary language only), first with the
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accepted values then with the match values. This partial is not
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applied to any other language subtags.
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The default is returned if no exact or fallback match is found.
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:param matches: A list of supported languages to find a match.
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:param default: The value that is returned if none match.
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"""
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# Look for an exact match first. If a client accepts "en-US",
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# "en-US" is a valid match at this point.
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result = super().best_match(matches)
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if result is not None:
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return result
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# Fall back to accepting primary tags. If a client accepts
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# "en-US", "en" is a valid match at this point. Need to use
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# re.split to account for 2 or 3 letter codes.
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fallback = Accept(
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[(_locale_delim_re.split(item[0], 1)[0], item[1]) for item in self]
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)
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result = fallback.best_match(matches)
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if result is not None:
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return result
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# Fall back to matching primary tags. If the client accepts
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# "en", "en-US" is a valid match at this point.
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fallback_matches = [_locale_delim_re.split(item, 1)[0] for item in matches]
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result = super().best_match(fallback_matches)
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# Return a value from the original match list. Find the first
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# original value that starts with the matched primary tag.
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if result is not None:
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return next(item for item in matches if item.startswith(result))
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return default
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class CharsetAccept(Accept):
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"""Like :class:`Accept` but with normalization for charsets."""
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def _value_matches(self, value, item):
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def _normalize(name):
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try:
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return codecs.lookup(name).name
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except LookupError:
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return name.lower()
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return item == "*" or _normalize(value) == _normalize(item)
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