feat: add function to get PaNOSC to ICAT mapping for where filter #260

datagateway_api/src/search_api/filters.py

@@ -30,6 +30,58 @@ def apply_filter(self, query):
         # function signature
         return super().apply_filter(query.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
+        """
+
+        try:
+            icat_mapping = mappings.mappings[panosc_entity_name][field_name]
+        except KeyError as e:
+            raise FilterError(f"Bad PaNOSC to ICAT mapping: {e.args}")
+
+        print(f"ICAT Mapping: {icat_mapping}, Type: {type(icat_mapping)}")
+        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]
+
+        return (panosc_entity_name, icat_field_name)
+
     def __str__(self):
         # TODO - can't just hardcode investigation entity. Might need `icat_entity_name`
         # to be passed into init