refactor: move get_icat_mapping() into PaNOSCMappings #261

- I've moved the code which deals with the parameter value field name list away from this function to make the function more generic/reusable. That code has been moved to applying the WHERE filter, where it'll be used. The mapping will not be reached by an include filter (under a valid API request) because the parameter values are for a field name/attribute, not a related entity

datagateway_api/src/search_api/filters.py

@@ -42,9 +42,28 @@ def apply_filter(self, query):
 
         # Convert PaNOSC field names to ICAT field names
         for field_name in panosc_field_names:
-            panosc_mapping_name, icat_field_name = self.get_icat_mapping(
+            panosc_mapping_name, icat_field_name = mappings.get_icat_mapping(
                 panosc_mapping_name, field_name,
             )
+
+            # An edge case for ICAT has been somewhat hardcoded here, to deal with
+            # ICAT's different parameter value field names. The following mapping is
+            # assumed (where order matters):
+            # {"Parameter": {"value": ["numericValue", "stringValue", "dateTimeValue"]}}
+            if isinstance(icat_field_name, list):
+                if isinstance(self.value, int) or isinstance(self.value, float):
+                    icat_field_name = icat_field_name[0]
+                elif isinstance(self.value, datetime):
+                    icat_field_name = icat_field_name[2]
+                elif isinstance(self.value, str):
+                    if DateHandler.is_str_a_date(self.value):
+                        icat_field_name = icat_field_name[2]
+                    else:
+                        icat_field_name = icat_field_name[1]
+                else:
+                    self.value = str(self.value)
+                    icat_field_name = icat_field_name[1]
+
             icat_field_names.append(icat_field_name)
 
         log.debug(
@@ -60,68 +79,6 @@ def apply_filter(self, query):
 
         return super().apply_filter(query.icat_query.query)
 
-    def get_icat_mapping(self, panosc_entity_name, field_name):
-        """
-        This function searches the PaNOSC mappings (from `search_api_mapping.json`,
-        maintained/stored by :class:`PaNOSCMappings`) and retrieves the ICAT translation
-        from the PaNOSC input. Fields in the same entity can be found, as well as fields
-        from related entities (e.g. Dataset.files.path) via recursion inside this
-        function.
-
-        An edge case for ICAT has been somewhat hardcoded into this function to dea
-        with ICAT's different parameter value field names. The following mapping is
-        assumed (where order matters):
-        {"Parameter": {"value": ["numericValue", "stringValue", "dateTimeValue"]}}
-
-        :param panosc_entity_name: A PaNOSC entity name e.g. "Dataset"
-        :type panosc_entity_name: :class:`str`
-        :param field_name: PaNOSC field name to fetch the ICAT version of e.g. "name"
-        :type field_name: :class:`str`
-        :return: Tuple containing the PaNOSC entity name (which will change from the
-            input if a related entity is found) and the ICAT field name
-            mapping/translation from the PaNOSC data model
-        :raises FilterError: If a valid mapping cannot be found
-        """
-
-        log.info(
-            "Searching mapping file to find ICAT translation for %s",
-            f"{panosc_entity_name}.{field_name}",
-        )
-
-        try:
-            icat_mapping = mappings.mappings[panosc_entity_name][field_name]
-            log.debug("ICAT mapping/translation found: %s", icat_mapping)
-        except KeyError as e:
-            raise FilterError(f"Bad PaNOSC to ICAT mapping: {e.args}")
-
-        if isinstance(icat_mapping, str):
-            # Field name
-            icat_field_name = icat_mapping
-        elif isinstance(icat_mapping, dict):
-            # Relation - JSON format: {PaNOSC entity name: ICAT related field name}
-            panosc_entity_name = list(icat_mapping.keys())[0]
-            icat_field_name = icat_mapping[panosc_entity_name]
-        elif isinstance(icat_mapping, list):
-            # Edge case for ICAT's different parameter value field names
-            if isinstance(self.value, int) or isinstance(self.value, float):
-                icat_field_name = icat_mapping[0]
-            elif isinstance(self.value, datetime):
-                icat_field_name = icat_mapping[2]
-            elif isinstance(self.value, str):
-                if DateHandler.is_str_a_date(self.value):
-                    icat_field_name = icat_mapping[2]
-                else:
-                    icat_field_name = icat_mapping[1]
-            else:
-                self.value = str(self.value)
-                icat_field_name = icat_mapping[1]
-
-        log.debug(
-            "Output of get_icat_mapping(): %s, %s", panosc_entity_name, icat_field_name,
-        )
-
-        return (panosc_entity_name, icat_field_name)
-
     def __str__(self):
         """
         String representation which is also used to apply WHERE filters that are inside

datagateway_api/src/search_api/panosc_mappings.py

@@ -2,7 +2,7 @@
 import logging
 from pathlib import Path
 
-from datagateway_api.src.common.exceptions import SearchAPIError
+from datagateway_api.src.common.exceptions import FilterError, SearchAPIError
 
 log = logging.getLogger()
 
@@ -19,6 +19,50 @@ def __init__(
         except IOError as e:
             raise SearchAPIError(e)
 
+    def get_icat_mapping(self, panosc_entity_name, field_name):
+        """
+        This function searches the PaNOSC mappings and retrieves the ICAT translation
+        from the PaNOSC input. Fields in the same entity can be found, as well as fields
+        from related entities (e.g. Dataset.files.path) via recursion inside this
+        function.
+
+        :param panosc_entity_name: A PaNOSC entity name e.g. "Dataset"
+        :type panosc_entity_name: :class:`str`
+        :param field_name: PaNOSC field name to fetch the ICAT version of e.g. "name"
+        :type field_name: :class:`str`
+        :return: Tuple containing the PaNOSC entity name (which will change from the
+            input if a related entity is found) and the ICAT field name
+            mapping/translation from the PaNOSC data model
+        :raises FilterError: If a valid mapping cannot be found
+        """
+
+        log.info(
+            "Searching mapping file to find ICAT translation for %s",
+            f"{panosc_entity_name}.{field_name}",
+        )
+
+        try:
+            icat_mapping = mappings.mappings[panosc_entity_name][field_name]
+            log.debug("ICAT mapping/translation found: %s", icat_mapping)
+        except KeyError as e:
+            # TODO - do we want to change the exception?
+            raise FilterError(f"Bad PaNOSC to ICAT mapping: {e.args}")
+
+        if isinstance(icat_mapping, str):
+            # Field name
+            icat_field_name = icat_mapping
+        elif isinstance(icat_mapping, dict):
+            # Relation - JSON format: {PaNOSC entity name: ICAT related field name}
+            panosc_entity_name = list(icat_mapping.keys())[0]
+            icat_field_name = icat_mapping[panosc_entity_name]
+        elif isinstance(icat_mapping, list):
+            # If a list of ICAT field names are found, this is likely to be a specific
+            # need for that entity (e.g. parameter values). Dealing with this should be
+            # delegated to other code in this repo so the entire list is returned here
+            icat_field_name = icat_mapping
+
+        return (panosc_entity_name, icat_field_name)
+
     def get_panosc_related_entity_name(
         self, panosc_entity_name, panosc_related_field_name,
     ):