# Copyright (c) 2021, NVIDIA CORPORATION.  All rights reserved.
#
# 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
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import pynini
from pynini.examples import plurals
from pynini.lib import pynutil

from nemo_text_processing.text_normalization.en.graph_utils import NEMO_NOT_QUOTE, NEMO_SIGMA, GraphFst, insert_space
from nemo_text_processing.text_normalization.en.verbalizers.ordinal import OrdinalFst


class FractionFst(GraphFst):
    """
    Finite state transducer for verbalizing fraction
        e.g. tokens { fraction { integer: "twenty three" numerator: "four" denominator: "five" } } ->
        twenty three and four fifth

    Args:
        deterministic: if True will provide a single transduction option,
            for False multiple transduction are generated (used for audio-based normalization)
    """

    def __init__(self, deterministic: bool = True, lm: bool = False):
        super().__init__(name="fraction", kind="verbalize", deterministic=deterministic)
        suffix = OrdinalFst().suffix

        integer = pynutil.delete("integer_part: \"") + pynini.closure(NEMO_NOT_QUOTE) + pynutil.delete("\" ")
        denominator_one = pynini.cross("denominator: \"one\"", "over one")
        denominator_half = pynini.cross("denominator: \"two\"", "half")
        denominator_quarter = pynini.cross("denominator: \"four\"", "quarter")

        denominator_rest = (
            pynutil.delete("denominator: \"") + pynini.closure(NEMO_NOT_QUOTE) @ suffix + pynutil.delete("\"")
        )

        denominators = plurals._priority_union(
            denominator_one,
            plurals._priority_union(
                denominator_half,
                plurals._priority_union(denominator_quarter, denominator_rest, NEMO_SIGMA),
                NEMO_SIGMA,
            ),
            NEMO_SIGMA,
        ).optimize()
        if not deterministic:
            denominators |= pynutil.delete("denominator: \"") + (pynini.accep("four") @ suffix) + pynutil.delete("\"")

        numerator_one = pynutil.delete("numerator: \"") + pynini.accep("one") + pynutil.delete("\" ")
        numerator_one = numerator_one + insert_space + denominators
        numerator_rest = (
            pynutil.delete("numerator: \"")
            + (pynini.closure(NEMO_NOT_QUOTE) - pynini.accep("one"))
            + pynutil.delete("\" ")
        )
        numerator_rest = numerator_rest + insert_space + denominators
        numerator_rest @= pynini.cdrewrite(
            plurals._priority_union(pynini.cross("half", "halves"), pynutil.insert("s"), NEMO_SIGMA),
            "",
            "[EOS]",
            NEMO_SIGMA,
        )

        graph = numerator_one | numerator_rest

        conjunction = pynutil.insert("and ")
        if not deterministic and not lm:
            conjunction = pynini.closure(conjunction, 0, 1)

        integer = pynini.closure(integer + insert_space + conjunction, 0, 1)

        graph = integer + graph
        graph @= pynini.cdrewrite(
            pynini.cross("and one half", "and a half") | pynini.cross("over ones", "over one"), "", "[EOS]", NEMO_SIGMA
        )

        self.graph = graph
        delete_tokens = self.delete_tokens(self.graph)
        self.fst = delete_tokens.optimize()