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 nemo_text_processing.inverse_text_normalization.vi.graph_utils import GraphFst, delete_space
  from nemo_text_processing.inverse_text_normalization.vi.utils import get_abs_path
  
  try:
      import pynini
      from pynini.lib import pynutil
  
      PYNINI_AVAILABLE = True
  except (ModuleNotFoundError, ImportError):
      PYNINI_AVAILABLE = False
  
  
  class TelephoneFst(GraphFst):
      """
      Finite state transducer for classifying telephone numbers, e.g.
          một hai ba một hai ba năm sáu bảy tám -> { number_part: "1231235678" }
      """
  
      def __init__(self):
          super().__init__(name="telephone", kind="classify")
          graph_zero = pynini.string_file(get_abs_path("data/numbers/zero.tsv"))
          graph_digit = pynini.string_file(get_abs_path("data/numbers/digit.tsv"))
          digit = graph_digit | graph_zero
          last_digit = digit | pynini.cross("mốt", "1") | pynini.cross("tư", "4") | pynini.cross("lăm", "5")
  
          graph_number_part = pynini.closure(digit + delete_space, 2) + last_digit
          number_part = pynutil.insert("number_part: \"") + graph_number_part + pynutil.insert("\"")
  
          graph = number_part
          final_graph = self.add_tokens(graph)
          self.fst = final_graph.optimize()
  