split code into submodules

src/nominatim_api/localization.py

@@ -0,0 +1,97 @@
+# SPDX-License-Identifier: GPL-3.0-or-later
+#
+# This file is part of Nominatim. (https://nominatim.org)
+#
+# Copyright (C) 2024 by the Nominatim developer community.
+# For a full list of authors see the git log.
+"""
+Helper functions for localizing names of results.
+"""
+from typing import Mapping, List, Optional
+
+import re
+
+class Locales:
+    """ Helper class for localization of names.
+
+        It takes a list of language prefixes in their order of preferred
+        usage.
+    """
+
+    def __init__(self, langs: Optional[List[str]] = None):
+        self.languages = langs or []
+        self.name_tags: List[str] = []
+
+        # Build the list of supported tags. It is currently hard-coded.
+        self._add_lang_tags('name')
+        self._add_tags('name', 'brand')
+        self._add_lang_tags('official_name', 'short_name')
+        self._add_tags('official_name', 'short_name', 'ref')
+
+
+    def __bool__(self) -> bool:
+        return len(self.languages) > 0
+
+
+    def _add_tags(self, *tags: str) -> None:
+        for tag in tags:
+            self.name_tags.append(tag)
+            self.name_tags.append(f"_place_{tag}")
+
+
+    def _add_lang_tags(self, *tags: str) -> None:
+        for tag in tags:
+            for lang in self.languages:
+                self.name_tags.append(f"{tag}:{lang}")
+                self.name_tags.append(f"_place_{tag}:{lang}")
+
+
+    def display_name(self, names: Optional[Mapping[str, str]]) -> str:
+        """ Return the best matching name from a dictionary of names
+            containing different name variants.
+
+            If 'names' is null or empty, an empty string is returned. If no
+            appropriate localization is found, the first name is returned.
+        """
+        if not names:
+            return ''
+
+        if len(names) > 1:
+            for tag in self.name_tags:
+                if tag in names:
+                    return names[tag]
+
+        # Nothing? Return any of the other names as a default.
+        return next(iter(names.values()))
+
+
+    @staticmethod
+    def from_accept_languages(langstr: str) -> 'Locales':
+        """ Create a localization object from a language list in the
+            format of HTTP accept-languages header.
+
+            The functions tries to be forgiving of format errors by first splitting
+            the string into comma-separated parts and then parsing each
+            description separately. Badly formatted parts are then ignored.
+        """
+        # split string into languages
+        candidates = []
+        for desc in langstr.split(','):
+            m = re.fullmatch(r'\s*([a-z_-]+)(?:;\s*q\s*=\s*([01](?:\.\d+)?))?\s*',
+                             desc, flags=re.I)
+            if m:
+                candidates.append((m[1], float(m[2] or 1.0)))
+
+        # sort the results by the weight of each language (preserving order).
+        candidates.sort(reverse=True, key=lambda e: e[1])
+
+        # If a language has a region variant, also add the language without
+        # variant but only if it isn't already in the list to not mess up the weight.
+        languages = []
+        for lid, _ in candidates:
+            languages.append(lid)
+            parts = lid.split('-', 1)
+            if len(parts) > 1 and all(c[0] != parts[0] for c in candidates):
+                languages.append(parts[0])
+
+        return Locales(languages)