# coding=utf-8
# Copyright 2019 The Open AI Team Authors and The HuggingFace Inc. team.
#
# 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.
"""Tokenization classes for XLM."""


import json
import logging
import os
import re
import sys
import unicodedata
from typing import List, Optional

import sacremoses as sm

from .tokenization_utils import PreTrainedTokenizer


logger = logging.getLogger(__name__)

VOCAB_FILES_NAMES = {
    "vocab_file": "vocab.json",
    "merges_file": "merges.txt",
}

PRETRAINED_VOCAB_FILES_MAP = {
    "vocab_file": {
        "xlm-mlm-en-2048": "https://s3.amazonaws.com/models.huggingface.co/bert/xlm-mlm-en-2048-vocab.json",
        "xlm-mlm-ende-1024": "https://s3.amazonaws.com/models.huggingface.co/bert/xlm-mlm-ende-1024-vocab.json",
        "xlm-mlm-enfr-1024": "https://s3.amazonaws.com/models.huggingface.co/bert/xlm-mlm-enfr-1024-vocab.json",
        "xlm-mlm-enro-1024": "https://s3.amazonaws.com/models.huggingface.co/bert/xlm-mlm-enro-1024-vocab.json",
        "xlm-mlm-tlm-xnli15-1024": "https://s3.amazonaws.com/models.huggingface.co/bert/xlm-mlm-tlm-xnli15-1024-vocab.json",
        "xlm-mlm-xnli15-1024": "https://s3.amazonaws.com/models.huggingface.co/bert/xlm-mlm-xnli15-1024-vocab.json",
        "xlm-clm-enfr-1024": "https://s3.amazonaws.com/models.huggingface.co/bert/xlm-clm-enfr-1024-vocab.json",
        "xlm-clm-ende-1024": "https://s3.amazonaws.com/models.huggingface.co/bert/xlm-clm-ende-1024-vocab.json",
        "xlm-mlm-17-1280": "https://s3.amazonaws.com/models.huggingface.co/bert/xlm-mlm-17-1280-vocab.json",
        "xlm-mlm-100-1280": "https://s3.amazonaws.com/models.huggingface.co/bert/xlm-mlm-100-1280-vocab.json",
    },
    "merges_file": {
        "xlm-mlm-en-2048": "https://s3.amazonaws.com/models.huggingface.co/bert/xlm-mlm-en-2048-merges.txt",
        "xlm-mlm-ende-1024": "https://s3.amazonaws.com/models.huggingface.co/bert/xlm-mlm-ende-1024-merges.txt",
        "xlm-mlm-enfr-1024": "https://s3.amazonaws.com/models.huggingface.co/bert/xlm-mlm-enfr-1024-merges.txt",
        "xlm-mlm-enro-1024": "https://s3.amazonaws.com/models.huggingface.co/bert/xlm-mlm-enro-1024-merges.txt",
        "xlm-mlm-tlm-xnli15-1024": "https://s3.amazonaws.com/models.huggingface.co/bert/xlm-mlm-tlm-xnli15-1024-merges.txt",
        "xlm-mlm-xnli15-1024": "https://s3.amazonaws.com/models.huggingface.co/bert/xlm-mlm-xnli15-1024-merges.txt",
        "xlm-clm-enfr-1024": "https://s3.amazonaws.com/models.huggingface.co/bert/xlm-mlm-enfr-1024-merges.txt",
        "xlm-clm-ende-1024": "https://s3.amazonaws.com/models.huggingface.co/bert/xlm-mlm-ende-1024-merges.txt",
        "xlm-mlm-17-1280": "https://s3.amazonaws.com/models.huggingface.co/bert/xlm-mlm-17-1280-merges.txt",
        "xlm-mlm-100-1280": "https://s3.amazonaws.com/models.huggingface.co/bert/xlm-mlm-100-1280-merges.txt",
    },
}

PRETRAINED_POSITIONAL_EMBEDDINGS_SIZES = {
    "xlm-mlm-en-2048": 512,
    "xlm-mlm-ende-1024": 512,
    "xlm-mlm-enfr-1024": 512,
    "xlm-mlm-enro-1024": 512,
    "xlm-mlm-tlm-xnli15-1024": 512,
    "xlm-mlm-xnli15-1024": 512,
    "xlm-clm-enfr-1024": 512,
    "xlm-clm-ende-1024": 512,
    "xlm-mlm-17-1280": 512,
    "xlm-mlm-100-1280": 512,
}

PRETRAINED_INIT_CONFIGURATION = {
    "xlm-mlm-en-2048": {"do_lowercase_and_remove_accent": True},
    "xlm-mlm-ende-1024": {
        "do_lowercase_and_remove_accent": True,
        "id2lang": {"0": "de", "1": "en"},
        "lang2id": {"de": 0, "en": 1},
    },
    "xlm-mlm-enfr-1024": {
        "do_lowercase_and_remove_accent": True,
        "id2lang": {"0": "en", "1": "fr"},
        "lang2id": {"en": 0, "fr": 1},
    },
    "xlm-mlm-enro-1024": {
        "do_lowercase_and_remove_accent": True,
        "id2lang": {"0": "en", "1": "ro"},
        "lang2id": {"en": 0, "ro": 1},
    },
    "xlm-mlm-tlm-xnli15-1024": {
        "do_lowercase_and_remove_accent": True,
        "id2lang": {
            "0": "ar",
            "1": "bg",
            "2": "de",
            "3": "el",
            "4": "en",
            "5": "es",
            "6": "fr",
            "7": "hi",
            "8": "ru",
            "9": "sw",
            "10": "th",
            "11": "tr",
            "12": "ur",
            "13": "vi",
            "14": "zh",
        },
        "lang2id": {
            "ar": 0,
            "bg": 1,
            "de": 2,
            "el": 3,
            "en": 4,
            "es": 5,
            "fr": 6,
            "hi": 7,
            "ru": 8,
            "sw": 9,
            "th": 10,
            "tr": 11,
            "ur": 12,
            "vi": 13,
            "zh": 14,
        },
    },
    "xlm-mlm-xnli15-1024": {
        "do_lowercase_and_remove_accent": True,
        "id2lang": {
            "0": "ar",
            "1": "bg",
            "2": "de",
            "3": "el",
            "4": "en",
            "5": "es",
            "6": "fr",
            "7": "hi",
            "8": "ru",
            "9": "sw",
            "10": "th",
            "11": "tr",
            "12": "ur",
            "13": "vi",
            "14": "zh",
        },
        "lang2id": {
            "ar": 0,
            "bg": 1,
            "de": 2,
            "el": 3,
            "en": 4,
            "es": 5,
            "fr": 6,
            "hi": 7,
            "ru": 8,
            "sw": 9,
            "th": 10,
            "tr": 11,
            "ur": 12,
            "vi": 13,
            "zh": 14,
        },
    },
    "xlm-clm-enfr-1024": {
        "do_lowercase_and_remove_accent": True,
        "id2lang": {"0": "en", "1": "fr"},
        "lang2id": {"en": 0, "fr": 1},
    },
    "xlm-clm-ende-1024": {
        "do_lowercase_and_remove_accent": True,
        "id2lang": {"0": "de", "1": "en"},
        "lang2id": {"de": 0, "en": 1},
    },
    "xlm-mlm-17-1280": {
        "do_lowercase_and_remove_accent": False,
        "id2lang": {
            "0": "ar",
            "1": "de",
            "2": "en",
            "3": "es",
            "4": "fr",
            "5": "hi",
            "6": "it",
            "7": "ja",
            "8": "ko",
            "9": "nl",
            "10": "pl",
            "11": "pt",
            "12": "ru",
            "13": "sv",
            "14": "tr",
            "15": "vi",
            "16": "zh",
        },
        "lang2id": {
            "ar": 0,
            "de": 1,
            "en": 2,
            "es": 3,
            "fr": 4,
            "hi": 5,
            "it": 6,
            "ja": 7,
            "ko": 8,
            "nl": 9,
            "pl": 10,
            "pt": 11,
            "ru": 12,
            "sv": 13,
            "tr": 14,
            "vi": 15,
            "zh": 16,
        },
    },
    "xlm-mlm-100-1280": {
        "do_lowercase_and_remove_accent": False,
        "id2lang": {
            "0": "af",
            "1": "als",
            "2": "am",
            "3": "an",
            "4": "ang",
            "5": "ar",
            "6": "arz",
            "7": "ast",
            "8": "az",
            "9": "bar",
            "10": "be",
            "11": "bg",
            "12": "bn",
            "13": "br",
            "14": "bs",
            "15": "ca",
            "16": "ceb",
            "17": "ckb",
            "18": "cs",
            "19": "cy",
            "20": "da",
            "21": "de",
            "22": "el",
            "23": "en",
            "24": "eo",
            "25": "es",
            "26": "et",
            "27": "eu",
            "28": "fa",
            "29": "fi",
            "30": "fr",
            "31": "fy",
            "32": "ga",
            "33": "gan",
            "34": "gl",
            "35": "gu",
            "36": "he",
            "37": "hi",
            "38": "hr",
            "39": "hu",
            "40": "hy",
            "41": "ia",
            "42": "id",
            "43": "is",
            "44": "it",
            "45": "ja",
            "46": "jv",
            "47": "ka",
            "48": "kk",
            "49": "kn",
            "50": "ko",
            "51": "ku",
            "52": "la",
            "53": "lb",
            "54": "lt",
            "55": "lv",
            "56": "mk",
            "57": "ml",
            "58": "mn",
            "59": "mr",
            "60": "ms",
            "61": "my",
            "62": "nds",
            "63": "ne",
            "64": "nl",
            "65": "nn",
            "66": "no",
            "67": "oc",
            "68": "pl",
            "69": "pt",
            "70": "ro",
            "71": "ru",
            "72": "scn",
            "73": "sco",
            "74": "sh",
            "75": "si",
            "76": "simple",
            "77": "sk",
            "78": "sl",
            "79": "sq",
            "80": "sr",
            "81": "sv",
            "82": "sw",
            "83": "ta",
            "84": "te",
            "85": "th",
            "86": "tl",
            "87": "tr",
            "88": "tt",
            "89": "uk",
            "90": "ur",
            "91": "uz",
            "92": "vi",
            "93": "war",
            "94": "wuu",
            "95": "yi",
            "96": "zh",
            "97": "zh_classical",
            "98": "zh_min_nan",
            "99": "zh_yue",
        },
        "lang2id": {
            "af": 0,
            "als": 1,
            "am": 2,
            "an": 3,
            "ang": 4,
            "ar": 5,
            "arz": 6,
            "ast": 7,
            "az": 8,
            "bar": 9,
            "be": 10,
            "bg": 11,
            "bn": 12,
            "br": 13,
            "bs": 14,
            "ca": 15,
            "ceb": 16,
            "ckb": 17,
            "cs": 18,
            "cy": 19,
            "da": 20,
            "de": 21,
            "el": 22,
            "en": 23,
            "eo": 24,
            "es": 25,
            "et": 26,
            "eu": 27,
            "fa": 28,
            "fi": 29,
            "fr": 30,
            "fy": 31,
            "ga": 32,
            "gan": 33,
            "gl": 34,
            "gu": 35,
            "he": 36,
            "hi": 37,
            "hr": 38,
            "hu": 39,
            "hy": 40,
            "ia": 41,
            "id": 42,
            "is": 43,
            "it": 44,
            "ja": 45,
            "jv": 46,
            "ka": 47,
            "kk": 48,
            "kn": 49,
            "ko": 50,
            "ku": 51,
            "la": 52,
            "lb": 53,
            "lt": 54,
            "lv": 55,
            "mk": 56,
            "ml": 57,
            "mn": 58,
            "mr": 59,
            "ms": 60,
            "my": 61,
            "nds": 62,
            "ne": 63,
            "nl": 64,
            "nn": 65,
            "no": 66,
            "oc": 67,
            "pl": 68,
            "pt": 69,
            "ro": 70,
            "ru": 71,
            "scn": 72,
            "sco": 73,
            "sh": 74,
            "si": 75,
            "simple": 76,
            "sk": 77,
            "sl": 78,
            "sq": 79,
            "sr": 80,
            "sv": 81,
            "sw": 82,
            "ta": 83,
            "te": 84,
            "th": 85,
            "tl": 86,
            "tr": 87,
            "tt": 88,
            "uk": 89,
            "ur": 90,
            "uz": 91,
            "vi": 92,
            "war": 93,
            "wuu": 94,
            "yi": 95,
            "zh": 96,
            "zh_classical": 97,
            "zh_min_nan": 98,
            "zh_yue": 99,
        },
    },
}


def get_pairs(word):
    """
    Return set of symbol pairs in a word.
    word is represented as tuple of symbols (symbols being variable-length strings)
    """
    pairs = set()
    prev_char = word[0]
    for char in word[1:]:
        pairs.add((prev_char, char))
        prev_char = char
    return pairs


def lowercase_and_remove_accent(text):
    """
    Lowercase and strips accents from a piece of text based on
    https://github.com/facebookresearch/XLM/blob/master/tools/lowercase_and_remove_accent.py
    """
    text = " ".join(text)
    text = text.lower()
    text = unicodedata.normalize("NFD", text)
    output = []
    for char in text:
        cat = unicodedata.category(char)
        if cat == "Mn":
            continue
        output.append(char)
    return "".join(output).lower().split(" ")


def replace_unicode_punct(text):
    """
    Port of https://github.com/moses-smt/mosesdecoder/blob/master/scripts/tokenizer/replace-unicode-punctuation.perl
    """
    text = text.replace("，", ",")
    text = re.sub(r"。\s*", ". ", text)
    text = text.replace("、", ",")
    text = text.replace("”", '"')
    text = text.replace("“", '"')
    text = text.replace("∶", ":")
    text = text.replace("：", ":")
    text = text.replace("？", "?")
    text = text.replace("《", '"')
    text = text.replace("》", '"')
    text = text.replace("）", ")")
    text = text.replace("！", "!")
    text = text.replace("（", "(")
    text = text.replace("；", ";")
    text = text.replace("１", "1")
    text = text.replace("」", '"')
    text = text.replace("「", '"')
    text = text.replace("０", "0")
    text = text.replace("３", "3")
    text = text.replace("２", "2")
    text = text.replace("５", "5")
    text = text.replace("６", "6")
    text = text.replace("９", "9")
    text = text.replace("７", "7")
    text = text.replace("８", "8")
    text = text.replace("４", "4")
    text = re.sub(r"．\s*", ". ", text)
    text = text.replace("～", "~")
    text = text.replace("’", "'")
    text = text.replace("…", "...")
    text = text.replace("━", "-")
    text = text.replace("〈", "<")
    text = text.replace("〉", ">")
    text = text.replace("【", "[")
    text = text.replace("】", "]")
    text = text.replace("％", "%")
    return text


def remove_non_printing_char(text):
    """
    Port of https://github.com/moses-smt/mosesdecoder/blob/master/scripts/tokenizer/remove-non-printing-char.perl
    """
    output = []
    for char in text:
        cat = unicodedata.category(char)
        if cat.startswith("C"):
            continue
        output.append(char)
    return "".join(output)


def romanian_preprocessing(text):
    """Sennrich's WMT16 scripts for Romanian preprocessing, used by model `xlm-mlm-enro-1024`"""
    # https://github.com/rsennrich/wmt16-scripts/blob/master/preprocess/normalise-romanian.py
    text = text.replace("\u015e", "\u0218").replace("\u015f", "\u0219")
    text = text.replace("\u0162", "\u021a").replace("\u0163", "\u021b")
    # https://github.com/rsennrich/wmt16-scripts/blob/master/preprocess/remove-diacritics.py
    text = text.replace("\u0218", "S").replace("\u0219", "s")  # s-comma
    text = text.replace("\u021a", "T").replace("\u021b", "t")  # t-comma
    text = text.replace("\u0102", "A").replace("\u0103", "a")
    text = text.replace("\u00C2", "A").replace("\u00E2", "a")
    text = text.replace("\u00CE", "I").replace("\u00EE", "i")
    return text


class XLMTokenizer(PreTrainedTokenizer):
    """
    BPE tokenizer for XLM

    - Moses preprocessing & tokenization for most supported languages
    - Language specific tokenization for Chinese (Jieba), Japanese (KyTea) and Thai (PyThaiNLP)
    - (optionally) lower case & normalize all inputs text
    - argument ``special_tokens`` and function ``set_special_tokens``, can be used to add additional symbols \
      (ex: "__classify__") to a vocabulary
    - `lang2id` attribute maps the languages supported by the model with their ids if provided (automatically set for pretrained vocabularies)
    - `id2lang` attributes does reverse mapping if provided (automatically set for pretrained vocabularies)

    This tokenizer inherits from :class:`~transformers.PreTrainedTokenizer` which contains most of the methods. Users
    should refer to the superclass for more information regarding methods.

    Args:
        vocab_file (:obj:`string`):
            Vocabulary file.
        merges_file (:obj:`string`):
            Merges file.
        do_lower_case (:obj:`bool`, `optional`, defaults to :obj:`True`):
            Whether to lowercase the input when tokenizing.
        remove_space (:obj:`bool`, `optional`, defaults to :obj:`True`):
            Whether to strip the text when tokenizing (removing excess spaces before and after the string).
        keep_accents (:obj:`bool`, `optional`, defaults to :obj:`False`):
            Whether to keep accents when tokenizing.
        unk_token (:obj:`string`, `optional`, defaults to "<unk>"):
            The unknown token. A token that is not in the vocabulary cannot be converted to an ID and is set to be this
            token instead.
        bos_token (:obj:`string`, `optional`, defaults to "<s>"):
            The beginning of sequence token that was used during pre-training. Can be used a sequence classifier token.

            .. note::

                When building a sequence using special tokens, this is not the token that is used for the beginning
                of sequence. The token used is the :obj:`cls_token`.
        sep_token (:obj:`string`, `optional`, defaults to "</s>"):
            The separator token, which is used when building a sequence from multiple sequences, e.g. two sequences
            for sequence classification or for a text and a question for question answering.
            It is also used as the last token of a sequence built with special tokens.
        pad_token (:obj:`string`, `optional`, defaults to "<pad>"):
            The token used for padding, for example when batching sequences of different lengths.
        cls_token (:obj:`string`, `optional`, defaults to "</s>"):
            The classifier token which is used when doing sequence classification (classification of the whole
            sequence instead of per-token classification). It is the first token of the sequence when built with
            special tokens.
        mask_token (:obj:`string`, `optional`, defaults to "<special1>"):
            The token used for masking values. This is the token used when training this model with masked language
            modeling. This is the token which the model will try to predict.
        additional_special_tokens (:obj:`List[str]`, `optional`, defaults to :obj:`["<special0>","<special1>","<special2>","<special3>","<special4>","<special5>","<special6>","<special7>","<special8>","<special9>"]`):
            List of additional special tokens.
        lang2id (:obj:`Dict[str, int]`, `optional`, defaults to :obj:`None`):
            Dictionary mapping languages string identifiers to their IDs.
        id2lang (:obj:`Dict[int, str`, `optional`, defaults to :obj:`None`):
            Dictionary mapping language IDs to their string identifiers.
        do_lowercase_and_remove_accent (:obj:`bool`, `optional`, defaults to :obj:`True`):
            Whether to lowercase and remove accents when tokenizing.
    """

    vocab_files_names = VOCAB_FILES_NAMES
    pretrained_vocab_files_map = PRETRAINED_VOCAB_FILES_MAP
    pretrained_init_configuration = PRETRAINED_INIT_CONFIGURATION
    max_model_input_sizes = PRETRAINED_POSITIONAL_EMBEDDINGS_SIZES

    def __init__(
        self,
        vocab_file,
        merges_file,
        unk_token="<unk>",
        bos_token="<s>",
        sep_token="</s>",
        pad_token="<pad>",
        cls_token="</s>",
        mask_token="<special1>",
        additional_special_tokens=[
            "<special0>",
            "<special1>",
            "<special2>",
            "<special3>",
            "<special4>",
            "<special5>",
            "<special6>",
            "<special7>",
            "<special8>",
            "<special9>",
        ],
        lang2id=None,
        id2lang=None,
        do_lowercase_and_remove_accent=True,
        **kwargs
    ):
        super().__init__(
            unk_token=unk_token,
            bos_token=bos_token,
            sep_token=sep_token,
            pad_token=pad_token,
            cls_token=cls_token,
            mask_token=mask_token,
            additional_special_tokens=additional_special_tokens,
            **kwargs,
        )

        self.max_len_single_sentence = self.max_len - 2  # take into account special tokens
        self.max_len_sentences_pair = self.max_len - 3  # take into account special tokens

        # cache of sm.MosesPunctNormalizer instance
        self.cache_moses_punct_normalizer = dict()
        # cache of sm.MosesTokenizer instance
        self.cache_moses_tokenizer = dict()
        self.lang_with_custom_tokenizer = set(["zh", "th", "ja"])
        # True for current supported model (v1.2.0), False for XLM-17 & 100
        self.do_lowercase_and_remove_accent = do_lowercase_and_remove_accent
        self.lang2id = lang2id
        self.id2lang = id2lang
        if lang2id is not None and id2lang is not None:
            assert len(lang2id) == len(id2lang)

        self.ja_word_tokenizer = None
        self.zh_word_tokenizer = None

        with open(vocab_file, encoding="utf-8") as vocab_handle:
            self.encoder = json.load(vocab_handle)
        self.decoder = {v: k for k, v in self.encoder.items()}
        with open(merges_file, encoding="utf-8") as merges_handle:
            merges = merges_handle.read().split("\n")[:-1]
        merges = [tuple(merge.split()[:2]) for merge in merges]
        self.bpe_ranks = dict(zip(merges, range(len(merges))))
        self.cache = {}

    def moses_punct_norm(self, text, lang):
        if lang not in self.cache_moses_punct_normalizer:
            punct_normalizer = sm.MosesPunctNormalizer(lang=lang)
            self.cache_moses_punct_normalizer[lang] = punct_normalizer
        else:
            punct_normalizer = self.cache_moses_punct_normalizer[lang]
        return punct_normalizer.normalize(text)

    def moses_tokenize(self, text, lang):
        if lang not in self.cache_moses_tokenizer:
            moses_tokenizer = sm.MosesTokenizer(lang=lang)
            self.cache_moses_tokenizer[lang] = moses_tokenizer
        else:
            moses_tokenizer = self.cache_moses_tokenizer[lang]
        return moses_tokenizer.tokenize(text, return_str=False, escape=False)

    def moses_pipeline(self, text, lang):
        text = replace_unicode_punct(text)
        text = self.moses_punct_norm(text, lang)
        text = remove_non_printing_char(text)
        return text

    def ja_tokenize(self, text):
        if self.ja_word_tokenizer is None:
            try:
                import Mykytea

                self.ja_word_tokenizer = Mykytea.Mykytea(
                    "-model %s/local/share/kytea/model.bin" % os.path.expanduser("~")
                )
            except (AttributeError, ImportError):
                logger.error(
                    "Make sure you install KyTea (https://github.com/neubig/kytea) and it's python wrapper (https://github.com/chezou/Mykytea-python) with the following steps"
                )
                logger.error("1. git clone git@github.com:neubig/kytea.git && cd kytea")
                logger.error("2. autoreconf -i")
                logger.error("3. ./configure --prefix=$HOME/local")
                logger.error("4. make && make install")
                logger.error("5. pip install kytea")
                raise
        return list(self.ja_word_tokenizer.getWS(text))

    @property
    def vocab_size(self):
        return len(self.encoder)

    def get_vocab(self):
        return dict(self.encoder, **self.added_tokens_encoder)

    def bpe(self, token):
        word = tuple(token[:-1]) + (token[-1] + "</w>",)
        if token in self.cache:
            return self.cache[token]
        pairs = get_pairs(word)

        if not pairs:
            return token + "</w>"

        while True:
            bigram = min(pairs, key=lambda pair: self.bpe_ranks.get(pair, float("inf")))
            if bigram not in self.bpe_ranks:
                break
            first, second = bigram
            new_word = []
            i = 0
            while i < len(word):
                try:
                    j = word.index(first, i)
                except ValueError:
                    new_word.extend(word[i:])
                    break
                else:
                    new_word.extend(word[i:j])
                    i = j

                if word[i] == first and i < len(word) - 1 and word[i + 1] == second:
                    new_word.append(first + second)
                    i += 2
                else:
                    new_word.append(word[i])
                    i += 1
            new_word = tuple(new_word)
            word = new_word
            if len(word) == 1:
                break
            else:
                pairs = get_pairs(word)
        word = " ".join(word)
        if word == "\n  </w>":
            word = "\n</w>"
        self.cache[token] = word
        return word

    def _tokenize(self, text, lang="en", bypass_tokenizer=False):
        """
        Tokenize a string given language code. For Chinese, Japanese and Thai, we use a language specific tokenizerself. Otherwise, we use Moses.

        Details of tokenization:
        - [sacremoses](https://github.com/alvations/sacremoses): port of Moses
            - Install with `pip install sacremoses`
        - [pythainlp](https://github.com/PyThaiNLP/pythainlp): Thai tokenizer
            - Install with `pip install pythainlp`
        - [kytea](https://github.com/chezou/Mykytea-python): Japanese tokenizer, wrapper of [KyTea](https://github.com/neubig/kytea)
            - Install with the following steps:
            ```
            git clone git@github.com:neubig/kytea.git && cd kytea
            autoreconf -i
            ./configure --prefix=$HOME/local
            make && make install
            pip install kytea
            ```
        - [jieba](https://github.com/fxsjy/jieba): Chinese tokenizer (*)
            - Install with `pip install jieba`

        (*) The original XLM used [Stanford Segmenter](https://nlp.stanford.edu/software/stanford-segmenter-2018-10-16.zip).
        However, the wrapper (`nltk.tokenize.stanford_segmenter`) is slow due to JVM overhead, and it will be deprecated.
        Jieba is a lot faster and pip-installable. Note there is some mismatch with the Stanford Segmenter. It should be fine
        if you fine-tune the model with Chinese supervisionself. If you want the same exact behaviour, use the original XLM
        [preprocessing script](https://github.com/facebookresearch/XLM/tree/master/tools) to tokenize the sentence externally,
        and set `bypass_tokenizer=True` to bypass the tokenizer.

        Args:
            - lang: ISO language code (default = 'en') (string). Languages should belong of the model supported languages. However, we don't enforce it.
            - bypass_tokenizer: Allow users to preprocess and tokenize the sentences externally (default = False)  (bool). If True, we only apply BPE.

        Returns:
            List of tokens.
        """
        if lang and self.lang2id and lang not in self.lang2id:
            logger.error(
                "Supplied language code not found in lang2id mapping. Please check that your language is supported by the loaded pretrained model."
            )
        if bypass_tokenizer:
            text = text.split()
        elif lang not in self.lang_with_custom_tokenizer:
            text = self.moses_pipeline(text, lang=lang)
            # TODO: make sure we are using `xlm-mlm-enro-1024`, since XLM-100 doesn't have this step
            if lang == "ro":
                text = romanian_preprocessing(text)
            text = self.moses_tokenize(text, lang=lang)
        elif lang == "th":
            text = self.moses_pipeline(text, lang=lang)
            try:
                if "pythainlp" not in sys.modules:
                    from pythainlp.tokenize import word_tokenize as th_word_tokenize
                else:
                    th_word_tokenize = sys.modules["pythainlp"].word_tokenize
            except (AttributeError, ImportError):
                logger.error(
                    "Make sure you install PyThaiNLP (https://github.com/PyThaiNLP/pythainlp) with the following steps"
                )
                logger.error("1. pip install pythainlp")
                raise
            text = th_word_tokenize(text)
        elif lang == "zh":
            try:
                if "jieba" not in sys.modules:
                    import jieba
                else:
                    jieba = sys.modules["jieba"]
            except (AttributeError, ImportError):
                logger.error("Make sure you install Jieba (https://github.com/fxsjy/jieba) with the following steps")
                logger.error("1. pip install jieba")
                raise
            text = " ".join(jieba.cut(text))
            text = self.moses_pipeline(text, lang=lang)
            text = text.split()
        elif lang == "ja":
            text = self.moses_pipeline(text, lang=lang)
            text = self.ja_tokenize(text)
        else:
            raise ValueError("It should not reach here")

        if self.do_lowercase_and_remove_accent and not bypass_tokenizer:
            text = lowercase_and_remove_accent(text)

        split_tokens = []
        for token in text:
            if token:
                split_tokens.extend([t for t in self.bpe(token).split(" ")])

        return split_tokens

    def _convert_token_to_id(self, token):
        """ Converts a token (str) in an id using the vocab. """
        return self.encoder.get(token, self.encoder.get(self.unk_token))

    def _convert_id_to_token(self, index):
        """Converts an index (integer) in a token (str) using the vocab."""
        return self.decoder.get(index, self.unk_token)

    def convert_tokens_to_string(self, tokens):
        """ Converts a sequence of tokens (string) in a single string. """
        out_string = "".join(tokens).replace("</w>", " ").strip()
        return out_string

    def build_inputs_with_special_tokens(
        self, token_ids_0: List[int], token_ids_1: Optional[List[int]] = None
    ) -> List[int]:
        """
        Build model inputs from a sequence or a pair of sequence for sequence classification tasks
        by concatenating and adding special tokens.
        A XLM sequence has the following format:

        - single sequence: ``<s> X </s>``
        - pair of sequences: ``<s> A </s> B </s>``

        Args:
            token_ids_0 (:obj:`List[int]`):
                List of IDs to which the special tokens will be added
            token_ids_1 (:obj:`List[int]`, `optional`, defaults to :obj:`None`):
                Optional second list of IDs for sequence pairs.

        Returns:
            :obj:`List[int]`: list of `input IDs <../glossary.html#input-ids>`__ with the appropriate special tokens.

        """
        if token_ids_1 is None:
            return [self.cls_token_id] + token_ids_0 + [self.sep_token_id]
        sep = [self.sep_token_id]
        cls = [self.cls_token_id]
        return cls + token_ids_0 + sep + token_ids_1 + sep

    def get_special_tokens_mask(
        self, token_ids_0: List[int], token_ids_1: Optional[List[int]] = None, already_has_special_tokens: bool = False
    ) -> List[int]:
        """
        Retrieves sequence ids from a token list that has no special tokens added. This method is called when adding
        special tokens using the tokenizer ``prepare_for_model`` or ``encode_plus`` methods.

        Args:
            token_ids_0 (:obj:`List[int]`):
                List of ids.
            token_ids_1 (:obj:`List[int]`, `optional`, defaults to :obj:`None`):
                Optional second list of IDs for sequence pairs.
            already_has_special_tokens (:obj:`bool`, `optional`, defaults to :obj:`False`):
                Set to True if the token list is already formatted with special tokens for the model

        Returns:
            :obj:`List[int]`: A list of integers in the range [0, 1]: 0 for a special token, 1 for a sequence token.
        """

        if already_has_special_tokens:
            if token_ids_1 is not None:
                raise ValueError(
                    "You should not supply a second sequence if the provided sequence of "
                    "ids is already formated with special tokens for the model."
                )
            return list(map(lambda x: 1 if x in [self.sep_token_id, self.cls_token_id] else 0, token_ids_0,))

        if token_ids_1 is not None:
            return [1] + ([0] * len(token_ids_0)) + [1] + ([0] * len(token_ids_1)) + [1]
        return [1] + ([0] * len(token_ids_0)) + [1]

    def create_token_type_ids_from_sequences(
        self, token_ids_0: List[int], token_ids_1: Optional[List[int]] = None
    ) -> List[int]:
        """
        Creates a mask from the two sequences passed to be used in a sequence-pair classification task.
        An XLM sequence pair mask has the following format:

        ::

            0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1
            | first sequence    | second sequence |

        if token_ids_1 is None, only returns the first portion of the mask (0s).

        Args:
            token_ids_0 (:obj:`List[int]`):
                List of ids.
            token_ids_1 (:obj:`List[int]`, `optional`, defaults to :obj:`None`):
                Optional second list of IDs for sequence pairs.

        Returns:
            :obj:`List[int]`: List of `token type IDs <../glossary.html#token-type-ids>`_ according to the given
            sequence(s).
        """
        sep = [self.sep_token_id]
        cls = [self.cls_token_id]
        if token_ids_1 is None:
            return len(cls + token_ids_0 + sep) * [0]
        return len(cls + token_ids_0 + sep) * [0] + len(token_ids_1 + sep) * [1]

    def save_vocabulary(self, save_directory):
        """
        Save the vocabulary and special tokens file to a directory.

        Args:
            save_directory (:obj:`str`):
                The directory in which to save the vocabulary.

        Returns:
            :obj:`Tuple(str)`: Paths to the files saved.
        """
        if not os.path.isdir(save_directory):
            logger.error("Vocabulary path ({}) should be a directory".format(save_directory))
            return
        vocab_file = os.path.join(save_directory, VOCAB_FILES_NAMES["vocab_file"])
        merge_file = os.path.join(save_directory, VOCAB_FILES_NAMES["merges_file"])

        with open(vocab_file, "w", encoding="utf-8") as f:
            f.write(json.dumps(self.encoder, ensure_ascii=False))

        index = 0
        with open(merge_file, "w", encoding="utf-8") as writer:
            for bpe_tokens, token_index in sorted(self.bpe_ranks.items(), key=lambda kv: kv[1]):
                if index != token_index:
                    logger.warning(
                        "Saving vocabulary to {}: BPE merge indices are not consecutive."
                        " Please check that the tokenizer is not corrupted!".format(merge_file)
                    )
                    index = token_index
                writer.write(" ".join(bpe_tokens) + "\n")
                index += 1

        return vocab_file, merge_file
