refactor: move Postal::QueryString to app/util/query_string

app/util/query_string.rb

@@ -0,0 +1,36 @@
+# frozen_string_literal: true
+
+class QueryString
+
+  def initialize(string)
+    @string = string.strip + " "
+  end
+
+  def [](value)
+    hash[value.to_s]
+  end
+
+  delegate :empty?, to: :hash
+
+  def hash
+    @hash ||= @string.scan(/([a-z]+):\s*(?:(\d{2,4}-\d{2}-\d{2}\s\d{2}:\d{2})|"(.*?)"|(.*?))(\s|\z)/).each_with_object({}) do |(key, date, string_with_spaces, value), hash|
+      if date
+        actual_value = date
+      elsif string_with_spaces
+        actual_value = string_with_spaces
+      elsif value == "[blank]"
+        actual_value = nil
+      else
+        actual_value = value
+      end
+
+      if hash.keys.include?(key.to_s)
+        hash[key.to_s] = [hash[key.to_s]].flatten
+        hash[key.to_s] << actual_value
+      else
+        hash[key.to_s] = actual_value
+      end
+    end
+  end
+
+end