introduce and use analyzer for postcodes

nominatim/tokenizer/token_analysis/postcodes.py

@@ -0,0 +1,54 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# This file is part of Nominatim. (https://nominatim.org)
+#
+# Copyright (C) 2022 by the Nominatim developer community.
+# For a full list of authors see the git log.
+"""
+Specialized processor for postcodes. Supports a 'lookup' variant of the
+token, which produces variants with optional spaces.
+"""
+
+from nominatim.tokenizer.token_analysis.generic_mutation import MutationVariantGenerator
+
+### Configuration section
+
+def configure(rules, normalization_rules): # pylint: disable=W0613
+    """ All behaviour is currently hard-coded.
+    """
+    return None
+
+### Analysis section
+
+def create(normalizer, transliterator, config): # pylint: disable=W0613
+    """ Create a new token analysis instance for this module.
+    """
+    return PostcodeTokenAnalysis(normalizer, transliterator)
+
+class PostcodeTokenAnalysis:
+    """ Detects common housenumber patterns and normalizes them.
+    """
+    def __init__(self, norm, trans):
+        self.norm = norm
+        self.trans = trans
+
+        self.mutator = MutationVariantGenerator(' ', (' ', ''))
+
+
+    def normalize(self, name):
+        """ Return the standard form of the postcode.
+        """
+        return name.strip().upper()
+
+
+    def get_variants_ascii(self, norm_name):
+        """ Compute the spelling variants for the given normalized postcode.
+
+            The official form creates one variant. If a 'lookup version' is
+            given, then it will create variants with optional spaces.
+        """
+        # Postcodes follow their own transliteration rules.
+        # Make sure at this point, that the terms are normalized in a way
+        # that they are searchable with the standard transliteration rules.
+        return [self.trans.transliterate(term) for term in
+                self.mutator.generate([self.norm.transliterate(norm_name)])]