minimum counts for tokens should always be 1

[nominatim.git] / nominatim / tokenizer / token_analysis / base.py

diff --git a/nominatim/tokenizer/token_analysis/base.py b/nominatim/tokenizer/token_analysis/base.py
index b55b4f7c2f6837bc7f30fc1ac538143aa483a0f5..c7ec61c9fd683c7b105b2ccb3c750995dd435e09 100644 (file)
--- a/nominatim/tokenizer/token_analysis/base.py
+++ b/nominatim/tokenizer/token_analysis/base.py
@@ -7,39 +7,90 @@
 """
 Common data types and protocols for analysers.
 """
-from typing import TypeVar, Mapping, List, Any
+from typing import Mapping, List, Any
 
-from typing_extensions import Protocol
+from nominatim.typing import Protocol
+from nominatim.data.place_name import PlaceName
 
+class Analyzer(Protocol):
+    """ The `create()` function of an analysis module needs to return an
+        object that implements the following functions.
+    """
 
-T_config = TypeVar('T_config') # pylint: disable=invalid-name
+    def get_canonical_id(self, name: PlaceName) -> str:
+        """ Return the canonical form of the given name. The canonical ID must
+            be unique (the same ID must always yield the same variants) and
+            must be a form from which the variants can be derived.
 
-class Analyser(Protocol):
-    """ Instance of the token analyser.
-    """
+            Arguments:
+                name: Extended place name description as prepared by
+                      the sanitizers.
 
-    def normalize(self, name: str) -> str:
-        """ Return the normalized form of the name. This is the standard form
-            from which possible variants for the name can be derived.
+            Returns:
+                ID string with a canonical form of the name. The string may
+                    be empty, when the analyzer cannot analyze the name at all,
+                    for example because the character set in use does not match.
         """
 
-    def get_variants_ascii(self, norm_name: str) -> List[str]:
-        """ Compute the spelling variants for the given normalized name
-            and transliterate the result.
+    def compute_variants(self, canonical_id: str) -> List[str]:
+        """ Compute the transliterated spelling variants for the given
+            canonical ID.
+
+            Arguments:
+                canonical_id: ID string previously computed with
+                              `get_canonical_id()`.
+
+            Returns:
+                A list of possible spelling variants. All strings must have
+                    been transformed with the global normalizer and
+                    transliterator ICU rules. Otherwise they cannot be matched
+                    against the input by the query frontend.
+                    The list may be empty, when there are no useful
+                    spelling variants. This may happen when an analyzer only
+                    usually outputs additional variants to the canonical spelling
+                    and there are no such variants.
         """
 
-class AnalysisModule(Protocol[T_config]):
-    """ Protocol for analysis modules.
+
+class AnalysisModule(Protocol):
+    """ The setup of the token analysis is split into two parts:
+        configuration and analyser factory. A token analysis module must
+        therefore implement the two functions here described.
     """
 
-    def configure(self, rules: Mapping[str, Any], normalization_rules: str) -> T_config:
+    def configure(self, rules: Mapping[str, Any],
+                  normalizer: Any, transliterator: Any) -> Any:
         """ Prepare the configuration of the analysis module.
             This function should prepare all data that can be shared
             between instances of this analyser.
+
+            Arguments:
+                rules: A dictionary with the additional configuration options
+                       as specified in the tokenizer configuration.
+                normalizer: an ICU Transliterator with the compiled
+                            global normalization rules.
+                transliterator: an ICU Transliterator with the compiled
+                                global transliteration rules.
+
+            Returns:
+                A data object with configuration data. This will be handed
+                    as is into the `create()` function and may be
+                    used freely by the analysis module as needed.
         """
 
-    def create(self, normalizer: Any, transliterator: Any, config: T_config) -> Analyser:
+    def create(self, normalizer: Any, transliterator: Any, config: Any) -> Analyzer:
         """ Create a new instance of the analyser.
             A separate instance of the analyser is created for each thread
             when used in multi-threading context.
+
+            Arguments:
+                normalizer: an ICU Transliterator with the compiled normalization
+                            rules.
+                transliterator: an ICU Transliterator with the compiled
+                                transliteration rules.
+                config: The object that was returned by the call to configure().
+
+            Returns:
+                A new analyzer instance. This must be an object that implements
+                    the Analyzer protocol.
         """