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#
# 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
#
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# distributed under the License is distributed on an "AS IS" BASIS,
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import importlib
from abc import ABC, abstractmethod
from typing import Any, Literal, Union

from nemo_curator.filters.bitext_filter import BitextFilter


class DocumentFilter(ABC):
    """
    An abstract base class for text-based document filters.

    This class serves as a template for creating specific document filters
    in the library. Subclasses should implement the abstract methods to
    define custom filtering behavior.
    """

    def __init__(self):
        super().__init__()
        self._name = self.__class__.__name__
        self._sentences = None
        self._paragraphs = None
        self._ngrams = None

    @abstractmethod
    def score_document(self, text: str) -> Any:
        """
        Calculate a score for the given document text.

        This method should be implemented by subclasses to define how
        a document's text is evaluated and scored.

        Args:
            text (str): The text content of the document to be scored.

        Returns:
            Any: A score or set of scores representing the document's
            relevance or quality. The type and structure of the
            return value should be consistent for each subclass.

        Raises:
            NotImplementedError: If the method is not implemented in a subclass.
        """
        raise NotImplementedError(
            "score_document method must be implemented by subclasses"
        )

    @abstractmethod
    def keep_document(self, scores: Any) -> bool:
        """
        Determine whether to keep a document based on its scores.

        This method should be implemented by subclasses to define the
        criteria for keeping or discarding a document based on the
        scores calculated by score_document().

        Args:
            scores (Any): The score or set of scores returned by score_document().
                          The type should match what is returned by score_document().

        Returns:
            bool: True if the document should be kept, False otherwise.

        Raises:
            NotImplementedError: If the method is not implemented in a subclass.
        """
        raise NotImplementedError(
            "keep_document method must be implemented by subclasses"
        )

    @property
    def backend(self) -> Literal["pandas", "cudf", "any"]:
        """
        The dataframe backend the filter operates on.
        Can be 'pandas', 'cudf', or 'any'. Defaults to 'pandas'.
        Returns:
            str: A string representing the dataframe backend the filter needs as input
        """
        return "pandas"

    @property
    def name(self):
        return self._name

    @property
    def sentences(self):
        return self._sentences

    @sentences.setter
    def sentences(self, sentences):
        self._sentences = sentences

    @property
    def paragraphs(self):
        return self._paragraphs

    @paragraphs.setter
    def paragraphs(self, paragraphs):
        self._paragraphs = paragraphs

    @property
    def ngrams(self):
        return self._ngrams

    @ngrams.setter
    def ngrams(self, ngrams):
        self._ngrams = ngrams


def import_filter(filter_path: str) -> Union[DocumentFilter, BitextFilter]:
    """
    Imports a filter under nemo_curator.filters given the module path

    Args:
        filter_path (str): The path to the filter in the form of "nemo_curator.filters.filter_name"

    Returns:
        DocumentFilter: The filter that is at the given path

    Raises:
        ValueError: If the filter_path does not point to a DocumentFilter
    """
    module_path, filter_name = filter_path.rsplit(".", 1)
    filter_module = importlib.import_module(module_path)
    filter_class = getattr(filter_module, filter_name)
    if not issubclass(filter_class, DocumentFilter) and not issubclass(
        filter_class, BitextFilter
    ):
        raise ValueError(
            f"Input filter {filter_class.__name__} must be derived "
            "from DocumentFilter defined in nemo_curator.filters.doc_filter or"
            "from BitextFilter defined in nemo_curator.filters.bitext_filter"
        )
    return filter_class
