#30: Create order handler

common/database_helpers.py

@@ -195,6 +195,32 @@ def get_query_filter(filter):
             raise BadFilterError(f" Bad filter: {filter}")
 
 
+class FilterOrderHandler(object):
+    """
+    The FilterOrderHandler takes in filters, sorts them according to the order of operations, then applies them.
+    """
+    def __init__(self):
+        self.filters = []
+
+    def add_filter(self, filter):
+        self.filters.append(filter)
+
+    def sort_filters(self):
+        """
+        Sorts the filters according to the order of operations
+        """
+        self.filters.sort(key=lambda x: x.precedence)
+
+    def apply_filters(self, query):
+        """
+        Given a query apply the filters the handler has in the correct order.
+        :param query: The query to have filters applied to
+        """
+        self.sort_filters()
+        for filter in self.filters:
+            filter.apply_filter(query)
+
+
 def insert_row_into_table(table, row):
     """
     Insert the given row into its table