Implement q priority of request headers (geopython#1952)

* Implement q priority sorting of requests

* Update l10n.py

Co-authored-by: Sander Schaminee <sander.schaminee@geocat.net>

---------

Co-authored-by: Sander Schaminee <sander.schaminee@geocat.net>

Author: webb-ben

pygeoapi/api/__init__.py

@@ -66,7 +66,8 @@
     CrsTransformSpec, TEMPLATES, UrlPrefetcher, dategetter,
     filter_dict_by_key_value, filter_providers_by_type, get_api_rules,
     get_base_url, get_provider_by_type, get_provider_default, get_typed_value,
-    get_crs_from_uri, get_supported_crs_list, render_j2_template, to_json
+    get_crs_from_uri, get_supported_crs_list, render_j2_template, to_json,
+    get_choice_from_headers, get_from_headers
 )
 
 LOGGER = logging.getLogger(__name__)
@@ -150,7 +151,8 @@ def apply_gzip(headers: dict, content: Union[str, bytes]) -> Union[str, bytes]:
     Compress content if requested in header.
     """
     charset = CHARSET[0]
-    if F_GZIP in headers.get('Content-Encoding', []):
+
+    if F_GZIP in get_from_headers(headers, 'content-encoding'):
         try:
             if isinstance(content, bytes):
                 # bytes means Content-Type needs to be set upstream
@@ -306,16 +308,18 @@ def _get_locale(self, headers, supported_locales):
             raise ValueError(f"{self.__class__.__name__} must be initialized"
                              f"with a list of valid supported locales")
 
-        for func, mapping in ((l10n.locale_from_params, self._args),
-                              (l10n.locale_from_headers, headers)):
-            loc_str = func(mapping)
-            if loc_str:
-                if not raw:
+        for field, mapping in ((l10n.QUERY_PARAM, self._args),
+                               ('accept-language', headers)):
+
+            loc_strs = get_choice_from_headers(mapping, field, all=True)
+            if loc_strs:
+                if raw is None:
                     # This is the first-found locale string: set as raw
-                    raw = loc_str
+                    raw = get_from_headers(mapping, field)
+
                 # Check if locale string is a good match for the UI
-                loc = l10n.best_match(loc_str, supported_locales)
-                is_override = func is l10n.locale_from_params
+                loc = l10n.best_match(loc_strs, supported_locales)
+                is_override = field is l10n.QUERY_PARAM
                 if loc != default_locale or is_override:
                     return raw, loc
 
@@ -336,17 +340,16 @@ def _get_format(self, headers) -> Union[str, None]:
             return format_
 
         # Format not specified: get from Accept headers (MIME types)
-        # e.g. format_ = 'text/html'
-        h = headers.get('accept', headers.get('Accept', '')).strip()  # noqa
+        # e.g. Accept: 'text/html;q=0.5,application/ld+json'
+        types_ = get_choice_from_headers(headers, 'accept', all=True)
+        if types_ is None:
+            return
+
         (fmts, mimes) = zip(*FORMAT_TYPES.items())
-        # basic support for complex types (i.e. with "q=0.x")
-        for type_ in (t.split(';')[0].strip() for t in h.split(',') if t):
+        for type_ in types_:
             if type_ in mimes:
                 idx_ = mimes.index(type_)
-                format_ = fmts[idx_]
-                break
-
-        return format_ or None
+                return fmts[idx_]
 
     @property
     def data(self) -> bytes:
@@ -504,7 +507,7 @@ def get_response_headers(self, force_lang: l10n.Locale = None,
         if F_GZIP in FORMAT_TYPES:
             if force_encoding:
                 headers['Content-Encoding'] = force_encoding
-            elif F_GZIP in self._headers.get('Accept-Encoding', ''):
+            elif F_GZIP in get_from_headers(self._headers, 'accept-encoding'):
                 headers['Content-Encoding'] = F_GZIP
 
         return headers

pygeoapi/l10n.py

@@ -113,7 +113,7 @@ def locale2str(value: Locale) -> str:
 
 def best_match(accept_languages, available_locales) -> Locale:
     """
-    Takes an Accept-Languages string (from header or request query params)
+    Takes an Accept-Languages sorted list (from header or request query params)
     and finds the best matching locale from a list of available locales.
 
     This function provides a framework-independent alternative to the
@@ -131,12 +131,12 @@ def best_match(accept_languages, available_locales) -> Locale:
                 or unknown locale is ignored. However, if no
                 `available_locales` are specified, a `LocaleError` is raised.
 
-    :param accept_languages: A Locale or string with one or more languages.
+    :param accept_languages: A Locale or list of one or more languages.
                              This can be as simple as "de" for example,
                              but it's also possible to include a territory
                              (e.g. "en-US" or "fr_BE") or even a complex
-                             string with quality values, e.g.
-                             "fr-CH, fr;q=0.9, en;q=0.8, de;q=0.7, *;q=0.5".
+                             list sorted by quality values, e.g.
+                             ["fr-CH", "fr", "en", "de", "*"].
     :param available_locales: A list containing the available locales.
                               For example, a pygeoapi provider might only
                               support ["de", "en"].
@@ -170,49 +170,12 @@ def get_match(locale_, available_locales_):
 
     if isinstance(accept_languages, Locale):
         # If a Babel Locale was used as input, transform back into a string
-        accept_languages = locale2str(accept_languages)
+        accept_languages = [locale2str(accept_languages)]
 
-    if not isinstance(accept_languages, str):
+    if not isinstance(accept_languages, list):
         # If `accept_languages` is not a string, ignore it
         LOGGER.debug(f"ignoring invalid accept-languages '{accept_languages}'")
-        accept_languages = ''
-
-    tags = accept_languages.split(',')
-    num_tags = len(tags)
-    req_locales = {}
-    for i, lang in enumerate(tags):
-        q_raw = None
-        q_out = None
-        if not lang:
-            continue
-
-        # Check if complex (i.e. with quality weights)
-        try:
-            lang, q_raw = (v.strip() for v in lang.split(';'))
-        except ValueError:
-            # Tuple unpacking failed: tag is not complex (or too complex :))
-            pass
-
-        # Validate locale tag
-        loc = str2locale(lang, True)
-        if not loc:
-            LOGGER.debug(f"ignoring invalid accept-language '{lang}'")
-            continue
-
-        # Validate quality weight (e.g. "q=0.7")
-        if q_raw:
-            try:
-                q_out = float([v.strip() for v in q_raw.split('=')][1])
-            except (ValueError, IndexError):
-                # Tuple unpacking failed: not a valid q tag
-                pass
-
-        # If there's no actual q, set one based on the language order
-        if not q_out:
-            q_out = num_tags - i
-
-        # Store locale
-        req_locales[q_out] = loc
+        accept_languages = []
 
     # Process supported locales
     prv_locales = OrderedDict()
@@ -221,7 +184,11 @@ def get_match(locale_, available_locales_):
         prv_locales.setdefault(loc.language, []).append(loc.territory)
 
     # Return best match from accepted languages
-    for _, loc in sorted(req_locales.items(), reverse=True):
+    for lang in accept_languages:
+        loc = str2locale(lang, True)
+        if not loc:
+            LOGGER.debug(f"ignoring invalid accept-language '{lang}'")
+            continue
         match = get_match(loc, prv_locales)
         if match:
             LOGGER.debug(f"'{match}' matches requested '{accept_languages}'")
@@ -281,7 +248,7 @@ def translate(value, language: Union[Locale, str]):
         return value
 
     # Find best language match and return value by its key
-    out_locale = best_match(language, loc_items.keys())
+    out_locale = best_match([language], loc_items.keys())
     return value[loc_items[out_locale]]
 
 
@@ -340,42 +307,6 @@ def _translate_dict(obj, level: int = 0):
     return result
 
 
-def locale_from_headers(headers) -> str:
-    """
-    Gets a valid Locale from a request headers dictionary.
-    Supported are complex strings (e.g. "fr-CH, fr;q=0.9, en;q=0.8"),
-    web locales (e.g. "en-US") or basic language tags (e.g. "en").
-    A value of `None` is returned if the locale was not found or invalid.
-
-    :param headers: Mapping of request headers.
-
-    :returns: locale string or None
-    """
-
-    lang = {k.lower(): v for k, v in headers.items()}.get('accept-language')
-    if lang:
-        LOGGER.debug(f"Got locale '{lang}' from 'Accept-Language' header")
-    return lang
-
-
-def locale_from_params(params) -> str:
-    """
-    Gets a valid Locale from a request query parameters dictionary.
-    Supported are complex strings (e.g. "fr-CH, fr;q=0.9, en;q=0.8"),
-    web locales (e.g. "en-US") or basic language tags (e.g. "en").
-    A value of `None` is returned if the locale was not found or invalid.
-
-    :param params: Mapping of request query parameters.
-
-    :returns: locale string or None
-    """
-
-    lang = params.get(QUERY_PARAM)
-    if lang:
-        LOGGER.debug(f"Got locale '{lang}' from query parameter '{QUERY_PARAM}'")  # noqa
-    return lang
-
-
 def set_response_language(headers: dict, *locale_: Locale):
     """
     Sets the Content-Language on the given HTTP response headers dict.

pygeoapi/util.py

@@ -38,6 +38,7 @@
 from datetime import date, datetime, time, timezone
 from decimal import Decimal
 from enum import Enum
+from heapq import heappush
 import json
 import logging
 import mimetypes
@@ -1054,3 +1055,58 @@ def _inplace_replace_geometry_filter_name(
             else:
                 _inplace_replace_geometry_filter_name(
                     sub_node, geometry_column_name)
+
+
+def get_from_headers(headers: dict, header_name: str) -> str:
+    """
+    Gets case insensitive value from dictionary.
+    This is particularly useful when trying to get
+    headers from Starlette and Flask without issue
+
+    :param headers: `dict` of request headers.
+    :param header_name: Name of request header.
+
+    :returns: `str` value of header
+    """
+
+    cleaned_headers = {k.strip().lower(): v for k, v in headers.items()}
+    return cleaned_headers.get(header_name.lower(), '')
+
+
+def get_choice_from_headers(headers: dict,
+                            header_name: str,
+                            all: bool = False) -> Union[str, List[str]]:
+    """
+    Gets choices from a request dictionary,
+    considering numerical ordering of preferences.
+    Supported are complex preference strings (e.g. "fr-CH, fr;q=0.9, en;q=0.8")
+
+    :param headers: `dict` of request headers.
+    :param header_name: Name of request header.
+    :param all: bool to return one or all header values.
+
+    :returns: Sorted choice or choices from header
+    """
+
+    # Select header of interest
+    header = get_from_headers(headers=headers, header_name=header_name)
+    if header == '':
+        return
+
+    # Parse choices, extracting optional q values (defaults to 1.0)
+    choices = []
+    for i, part in enumerate(header.split(',')):
+        match = re.match(r'^([^;]+)(?:;q=([\d.]+))?$', part.strip())
+        if match:
+            value, q_value = match.groups()
+            q_value = float(q_value) if q_value else 1.0
+
+            # Sort choices by q value and index
+            if 0 <= q_value <= 1:
+                heappush(choices, (1 / q_value, i, value))
+
+    # Drop q value
+    sorted_choices = [choice[-1] for choice in choices]
+
+    # Return one or all choices
+    return sorted_choices if all else sorted_choices[0]

tests/test_util.py

@@ -549,3 +549,32 @@ def test_modify_pygeofilter(
         geometry_column_name=geometry_colum_name
     )
     assert result == expected
+
+
+def test_get_choice_from_headers():
+    _headers = {
+        'accept': 'text/html;q=0.5,application/ld+json',
+        'accept-encoding': 'deflate;q=0.5,gzip'
+    }
+
+    # Test various capitalizations
+    assert util.get_choice_from_headers(_headers, 'accept-language') is None
+    assert util.get_choice_from_headers(
+        {**_headers, 'accept-language': 'en;q=0.8,de;q=0.6,fr;q=0.4'},
+        'accept-language') == 'en'
+    assert util.get_choice_from_headers(
+        {**_headers, 'Accept-Language': 'en;q=0.8,de'},
+        'accept-language') == 'de'
+    assert util.get_choice_from_headers(
+        {**_headers, 'Accept-Language': 'en,de'}, 'accept-language') == 'en'
+    assert util.get_choice_from_headers(
+        {**_headers, 'ACCEPT-LANGUAGE': 'en;q=0.8,de;q=0.2,fr'},
+        'accept-language') == 'fr'
+    assert util.get_choice_from_headers(
+        {**_headers, 'accept-language': 'en_US'}, 'accept-language') == 'en_US'
+
+    assert util.get_choice_from_headers(_headers, 'accept-encoding') == 'gzip'
+    assert util.get_choice_from_headers(_headers,
+                                        'accept') == 'application/ld+json'
+    assert util.get_choice_from_headers(
+        {'accept-language': 'en_US', 'accept': '*/*'}, 'accept') == '*/*'