"""
Word Swap by Random Character Substitution
------------------------------------------------
"""
import numpy as np

# from textattack.shared import utils
from .word_swap import WordSwap


class WordSwapRandomCharacterSubstitution(WordSwap):
    """Transforms an input by replacing one character in a word with a random
    new character.

    Args:
        random_one (bool): Whether to return a single word with a random
            character deleted. If not set, returns all possible options.
    >>> from textattack.transformations import WordSwapRandomCharacterSubstitution
    >>> from textattack.augmentation import Augmenter

    >>> transformation = WordSwapRandomCharacterSubstitution()
    >>> augmenter = Augmenter(transformation=transformation)
    >>> s = 'I am fabulous.'
    >>> augmenter.augment(s)
    """

    def __init__(self, random_one=True, **kwargs):
        super().__init__(**kwargs)
        self.random_one = random_one

    def _get_replacement_words(self, word):
        """Returns returns a list containing all possible words with 1 letter
        substituted for a random letter."""
        if len(word) <= 1:
            return []

        candidate_words = []

        if self.random_one:
            i = np.random.randint(0, len(word))
            candidate_word = word[:i] + self._get_random_letter() + word[i + 1 :]
            candidate_words.append(candidate_word)
        else:
            for i in range(len(word)):
                candidate_word = word[:i] + self._get_random_letter() + word[i + 1 :]
                candidate_words.append(candidate_word)

        return candidate_words

    @property
    def deterministic(self):
        return not self.random_one

    def extra_repr_keys(self):
        return super().extra_repr_keys() + ["random_one"]
