text: # Copyright (c) 2021, NVIDIA CORPORATION.  All rights reserved.
  # Copyright 2015 and onwards Google, Inc.
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #     http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  
  from inverse_text_normalization.mr.graph_utils import (
      NEMO_NOT_QUOTE,
      GraphFst,
      delete_extra_space,
      delete_space,
  )
  
  try:
      import pynini
      from pynini.lib import pynutil
  
      PYNINI_AVAILABLE = True
  except (ModuleNotFoundError, ImportError):
      PYNINI_AVAILABLE = False
  
  
  class DateFst(GraphFst):
      """
      Finite state transducer for verbalizing date
          e.g. tdate { month: "january" day: "5" year: "2012" preserve_order: true } -> february 5 2012
      """
  
      def __init__(self):
          super().__init__(name="date", kind="verbalize")
          month = (
              pynutil.delete("month:")
              + delete_space
              + pynutil.delete("\"")
              + pynini.closure(NEMO_NOT_QUOTE, 1)
              + pynutil.delete("\"")
          )
          day = (
              pynutil.delete("day:")
              + delete_space
              + pynutil.delete("\"")
              + pynini.closure(NEMO_NOT_QUOTE, 1)
              + pynutil.delete("\"")
          )
          year = (
              pynutil.delete("year:")
              + delete_space
              + pynutil.delete("\"")
              + pynini.closure(NEMO_NOT_QUOTE, 1)
              + delete_space
              + pynutil.delete("\"")
          )
  
          # month (day) year
          graph_mdy = (
              month + pynini.closure(delete_extra_space + day, 0, 1) + pynini.closure(delete_extra_space + year, 0, 1)
          )
  
          # (day) month year
          graph_dmy = (
              pynini.closure(day + delete_extra_space, 0, 1) + month + pynini.closure(delete_extra_space + year, 0, 1)
          )
  
          optional_preserve_order = pynini.closure(
              pynutil.delete("preserve_order:") + delete_space + pynutil.delete("true") + delete_space
              | pynutil.delete("field_order:")
              + delete_space
              + pynutil.delete("\"")
              + NEMO_NOT_QUOTE
              + pynutil.delete("\"")
              + delete_space
          )
  
          final_graph = (graph_mdy | year | graph_dmy) + delete_space + optional_preserve_order
  
          delete_tokens = self.delete_tokens(final_graph)
          self.fst = delete_tokens.optimize()
  