#223: Implement DatabaseFilterUtilities into DatabaseWhereFilter

- Similar implemenation as DatabaseDistinctFieldFilter

datagateway_api/common/database/filters.py

@@ -61,9 +61,6 @@ def _extract_filter_fields(self, field):
         else:
             raise ValueError(f"Maximum related depth exceeded. {field}'s depth > 3")
 
-        # TODO - Remove if not needed
-        # return (field, related_field, related_related_field)
-
     def _add_query_join(self, query):
         """
         Fetches the appropriate entity model based on the contents of `self.field` and
@@ -97,58 +94,16 @@ def _add_query_join(self, query):
         return field
 
 
-class DatabaseWhereFilter(WhereFilter):
+class DatabaseWhereFilter(WhereFilter, DatabaseFilterUtilities):
     def __init__(self, field, value, operation):
-        super().__init__(field, value, operation)
+        # TODO - Apply any 'pythonic' solution here too
+        WhereFilter.__init__(self, field, value, operation)
+        DatabaseFilterUtilities.__init__(self)
 
-        self.included_field = None
-        self.included_included_field = None
         self._extract_filter_fields(field)
 
-    def _extract_filter_fields(self, field):
-        """
-        Extract the related fields names and put them into separate variables
-
-        :param field: ICAT field names, separated by dots
-        :type field: :class:`str`
-        """
-
-        fields = field.split(".")
-        include_depth = len(fields)
-
-        log.debug("Fields: %s, Include Depth: %d", fields, include_depth)
-
-        if include_depth == 1:
-            self.field = fields[0]
-        elif include_depth == 2:
-            self.field = fields[0]
-            self.included_field = fields[1]
-        elif include_depth == 3:
-            self.field = fields[0]
-            self.included_field = fields[1]
-            self.included_included_field = fields[2]
-        else:
-            raise ValueError(f"Maximum include depth exceeded. {field}'s depth > 3")
-
     def apply_filter(self, query):
-        try:
-            field = getattr(query.table, self.field)
-        except AttributeError:
-            raise FilterError(
-                f"Unknown attribute {self.field} on table {query.table.__name__}",
-            )
-
-        if self.included_included_field:
-            included_table = getattr(models, self.field)
-            included_included_table = getattr(models, self.included_field)
-            query.base_query = query.base_query.join(included_table).join(
-                included_included_table,
-            )
-            field = getattr(included_included_table, self.included_included_field)
-        elif self.included_field:
-            included_table = get_entity_object_from_name(self.field)
-            query.base_query = query.base_query.join(included_table)
-            field = getattr(included_table, self.included_field)
+        field = self._add_query_join(query)
 
         if self.operation == "eq":
             query.base_query = query.base_query.filter(field == self.value)