split code into submodules

src/nominatim_db/tokenizer/token_analysis/generic.py

@@ -0,0 +1,150 @@
+# 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.
+"""
+Generic processor for names that creates abbreviation variants.
+"""
+from typing import Mapping, Dict, Any, Iterable, Iterator, Optional, List, cast
+import itertools
+
+import datrie
+
+from nominatim_core.errors import UsageError
+from ...data.place_name import PlaceName
+from .config_variants import get_variant_config
+from .generic_mutation import MutationVariantGenerator
+
+### Configuration section
+
+def configure(rules: Mapping[str, Any], normalizer: Any, _: Any) -> Dict[str, Any]:
+    """ Extract and preprocess the configuration for this module.
+    """
+    config: Dict[str, Any] = {}
+
+    config['replacements'], config['chars'] = get_variant_config(rules.get('variants'),
+                                                                 normalizer)
+    config['variant_only'] = rules.get('mode', '') == 'variant-only'
+
+    # parse mutation rules
+    config['mutations'] = []
+    for rule in rules.get('mutations', []):
+        if 'pattern' not in rule:
+            raise UsageError("Missing field 'pattern' in mutation configuration.")
+        if not isinstance(rule['pattern'], str):
+            raise UsageError("Field 'pattern' in mutation configuration "
+                             "must be a simple text field.")
+        if 'replacements' not in rule:
+            raise UsageError("Missing field 'replacements' in mutation configuration.")
+        if not isinstance(rule['replacements'], list):
+            raise UsageError("Field 'replacements' in mutation configuration "
+                             "must be a list of texts.")
+
+        config['mutations'].append((rule['pattern'], rule['replacements']))
+
+    return config
+
+
+### Analysis section
+
+def create(normalizer: Any, transliterator: Any,
+           config: Mapping[str, Any]) -> 'GenericTokenAnalysis':
+    """ Create a new token analysis instance for this module.
+    """
+    return GenericTokenAnalysis(normalizer, transliterator, config)
+
+
+class GenericTokenAnalysis:
+    """ Collects the different transformation rules for normalisation of names
+        and provides the functions to apply the transformations.
+    """
+
+    def __init__(self, norm: Any, to_ascii: Any, config: Mapping[str, Any]) -> None:
+        self.norm = norm
+        self.to_ascii = to_ascii
+        self.variant_only = config['variant_only']
+
+        # Set up datrie
+        if config['replacements']:
+            self.replacements = datrie.Trie(config['chars'])
+            for src, repllist in config['replacements']:
+                self.replacements[src] = repllist
+        else:
+            self.replacements = None
+
+        # set up mutation rules
+        self.mutations = [MutationVariantGenerator(*cfg) for cfg in config['mutations']]
+
+
+    def get_canonical_id(self, name: PlaceName) -> str:
+        """ Return the normalized form of the name. This is the standard form
+            from which possible variants for the name can be derived.
+        """
+        return cast(str, self.norm.transliterate(name.name)).strip()
+
+
+    def compute_variants(self, norm_name: str) -> List[str]:
+        """ Compute the spelling variants for the given normalized name
+            and transliterate the result.
+        """
+        variants = self._generate_word_variants(norm_name)
+
+        for mutation in self.mutations:
+            variants = mutation.generate(variants)
+
+        return [name for name in self._transliterate_unique_list(norm_name, variants) if name]
+
+
+    def _transliterate_unique_list(self, norm_name: str,
+                                   iterable: Iterable[str]) -> Iterator[Optional[str]]:
+        seen = set()
+        if self.variant_only:
+            seen.add(norm_name)
+
+        for variant in map(str.strip, iterable):
+            if variant not in seen:
+                seen.add(variant)
+                yield self.to_ascii.transliterate(variant).strip()
+
+
+    def _generate_word_variants(self, norm_name: str) -> Iterable[str]:
+        baseform = '^ ' + norm_name + ' ^'
+        baselen = len(baseform)
+        partials = ['']
+
+        startpos = 0
+        if self.replacements is not None:
+            pos = 0
+            force_space = False
+            while pos < baselen:
+                full, repl = self.replacements.longest_prefix_item(baseform[pos:],
+                                                                   (None, None))
+                if full is not None:
+                    done = baseform[startpos:pos]
+                    partials = [v + done + r
+                                for v, r in itertools.product(partials, repl)
+                                if not force_space or r.startswith(' ')]
+                    if len(partials) > 128:
+                        # If too many variants are produced, they are unlikely
+                        # to be helpful. Only use the original term.
+                        startpos = 0
+                        break
+                    startpos = pos + len(full)
+                    if full[-1] == ' ':
+                        startpos -= 1
+                        force_space = True
+                    pos = startpos
+                else:
+                    pos += 1
+                    force_space = False
+
+        # No variants detected? Fast return.
+        if startpos == 0:
+            return (norm_name, )
+
+        if startpos < baselen:
+            return (part[1:] + baseform[startpos:-1] for part in partials)
+
+        return (part[1:-1] for part in partials)