graph_utils.py

# Copyright (c) 2024, 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.

import logging
import os
import string
from pathlib import Path
from typing import Dict

import pynini
from pynini import Far
from pynini.export import export
from pynini.lib import byte, pynutil, utf8

NEMO_CHAR = utf8.VALID_UTF8_CHAR
NEMO_DIGIT = byte.DIGIT

NEMO_HI_DIGIT = pynini.union("०", "१", "२", "३", "४", "५", "६", "७", "८", "९").optimize()
NEMO_HI_NON_ZERO = pynini.union("१", "२", "३", "४", "५", "६", "७", "८", "९").optimize()
NEMO_HI_ZERO = "०"

HI_DEDH = "डेढ़"  # 1.5
HI_DHAI = "ढाई"  # 2.5
HI_SAVVA = "सवा"  # quarter more (1.25)
HI_SADHE = "साढ़े"  # half more (X.5)
HI_PAUNE = "पौने"  # quarter less (0.75)

# Hindi decimal representations
HI_POINT_FIVE = ".५"  # .5
HI_ONE_POINT_FIVE = "१.५"  # 1.5
HI_TWO_POINT_FIVE = "२.५"  # 2.5
HI_DECIMAL_25 = ".२५"  # .25
HI_DECIMAL_75 = ".७५"  # .75

# Symbol constants
HI_BY = "बाई"
LOWERCASE_X = "x"
UPPERCASE_X = "X"
ASTERISK = "*"
HYPHEN = "-"
SLASH = "/"
COMMA = ","
PERIOD = "."
HI_PERIOD = "।"

NEMO_LOWER = pynini.union(*string.ascii_lowercase).optimize()
NEMO_UPPER = pynini.union(*string.ascii_uppercase).optimize()
NEMO_ALPHA = pynini.union(NEMO_LOWER, NEMO_UPPER).optimize()
NEMO_HEX = pynini.union(*string.hexdigits).optimize()
NEMO_NON_BREAKING_SPACE = u"\u00a0"
NEMO_SPACE = " "
NEMO_WHITE_SPACE = pynini.union(" ", "\t", "\n", "\r", u"\u00a0").optimize()
NEMO_NOT_SPACE = pynini.difference(NEMO_CHAR, NEMO_WHITE_SPACE).optimize()
NEMO_NOT_QUOTE = pynini.difference(NEMO_CHAR, r'"').optimize()
TO_LOWER = pynini.union(*[pynini.cross(x, y) for x, y in zip(string.ascii_uppercase, string.ascii_lowercase)])
TO_UPPER = pynini.invert(TO_LOWER)
NEMO_SIGMA = pynini.closure(NEMO_CHAR)


delete_space = pynutil.delete(pynini.closure(NEMO_WHITE_SPACE))
delete_zero_or_one_space = pynutil.delete(pynini.closure(NEMO_WHITE_SPACE, 0, 1))
insert_space = pynutil.insert(" ")
delete_extra_space = pynini.cross(pynini.closure(NEMO_WHITE_SPACE, 1), " ")
delete_preserve_order = pynini.closure(
    pynutil.delete(" preserve_order: true")
    | (pynutil.delete(" field_order: \"") + NEMO_NOT_QUOTE + pynutil.delete("\""))
)


MIN_NEG_WEIGHT = -0.0001
MIN_POS_WEIGHT = 0.0001
INPUT_CASED = "cased"
INPUT_LOWER_CASED = "lower_cased"
MINUS = pynini.union(" ऋणात्मक ", " ऋणात्मक ").optimize()


def capitalized_input_graph(
    graph: 'pynini.FstLike', original_graph_weight: float = None, capitalized_graph_weight: float = None
) -> 'pynini.FstLike':
    """
    Allow graph input to be capitalized, e.g. for ITN)

    Args:
        graph: FstGraph
        original_graph_weight: weight to add to the original `graph`
        capitalized_graph_weight: weight to add to the capitalized graph
    """
    capitalized_graph = pynini.compose(TO_LOWER + NEMO_SIGMA, graph).optimize()

    if original_graph_weight is not None:
        graph = pynutil.add_weight(graph, weight=original_graph_weight)

    if capitalized_graph_weight is not None:
        capitalized_graph = pynutil.add_weight(capitalized_graph, weight=capitalized_graph_weight)

    graph |= capitalized_graph
    return graph


def generator_main(file_name: str, graphs: Dict[str, 'pynini.FstLike']):
    """
    Exports graph as OpenFst finite state archive (FAR) file with given file name and rule name.

    Args:
        file_name: exported file name
        graphs: Mapping of a rule name and Pynini WFST graph to be exported
    """
    exporter = export.Exporter(file_name)
    for rule, graph in graphs.items():
        exporter[rule] = graph.optimize()
    exporter.close()
    logging.info(f'Created {file_name}')


def convert_space(fst) -> 'pynini.FstLike':
    """
    Converts space to nonbreaking space.
    Used only in tagger grammars for transducing token values within quotes, e.g. name: "hello kitty"
    This is making transducer significantly slower, so only use when there could be potential spaces within quotes, otherwise leave it.

    Args:
        fst: input fst

    Returns output fst where breaking spaces are converted to non breaking spaces
    """
    return fst @ pynini.cdrewrite(pynini.cross(NEMO_SPACE, NEMO_NON_BREAKING_SPACE), "", "", NEMO_SIGMA)


class GraphFst:
    """
    Base class for all grammar fsts.

    Args:
        name: name of grammar class
        kind: either 'classify' or 'verbalize'
        deterministic: if True will provide a single transduction option,
            for False multiple transduction are generated (used for audio-based normalization)
    """

    def __init__(self, name: str, kind: str, deterministic: bool = True):
        self.name = name
        self.kind = kind
        self._fst = None
        self.deterministic = deterministic

        self.far_path = Path(os.path.dirname(__file__) + '/grammars/' + kind + '/' + name + '.far')
        if self.far_exist():
            self._fst = Far(self.far_path, mode="r", arc_type="standard", far_type="default").get_fst()

    def far_exist(self) -> bool:
        """
        Returns true if FAR can be loaded
        """
        return self.far_path.exists()

    @property
    def fst(self) -> 'pynini.FstLike':
        return self._fst

    @fst.setter
    def fst(self, fst):
        self._fst = fst

    def add_tokens(self, fst) -> 'pynini.FstLike':
        """
        Wraps class name around to given fst

        Args:
            fst: input fst

        Returns:
            Fst: fst
        """
        return pynutil.insert(f"{self.name} {{ ") + fst + pynutil.insert(" }")

    def delete_tokens(self, fst) -> 'pynini.FstLike':
        """
        Deletes class name wrap around output of given fst

        Args:
            fst: input fst

        Returns:
            Fst: fst
        """
        res = (
            pynutil.delete(f"{self.name}")
            + delete_space
            + pynutil.delete("{")
            + delete_space
            + fst
            + delete_space
            + pynutil.delete("}")
        )
        return res @ pynini.cdrewrite(pynini.cross(u"\u00a0", " "), "", "", NEMO_SIGMA)