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# MIT License
#
# Copyright (c) 2021 OpenAI
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# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
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# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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# SOFTWARE.
#
# Modified by Jiarui Xu
# -------------------------------------------------------------------------

import gzip
import html
import os
from functools import lru_cache

import ftfy
import regex as re
import torch


@lru_cache()
def default_bpe():
    return os.path.join(os.path.dirname(os.path.abspath(__file__)), 'bpe_simple_vocab_16e6.txt.gz')


@lru_cache()
def bytes_to_unicode():
    """Returns list of utf-8 byte and a corresponding list of unicode strings.

    The reversible bpe codes work on unicode strings. This means you need a large # of unicode characters in your vocab
    if you want to avoid UNKs. When you're at something like a 10B token dataset you end up needing around 5K for decent
    coverage. This is a significant percentage of your normal, say, 32K bpe vocab. To avoid that, we want lookup tables
    between utf-8 bytes and unicode strings. And avoids mapping to whitespace/control characters the bpe code barfs on.
    """
    bs = list(range(ord('!'), ord('~') + 1)) + list(range(ord('¡'), ord('¬') + 1)) + list(range(ord('®'), ord('ÿ') + 1))
    cs = bs[:]
    n = 0
    for b in range(2**8):
        if b not in bs:
            bs.append(b)
            cs.append(2**8 + n)
            n += 1
    cs = [chr(n) for n in cs]
    return dict(zip(bs, cs))


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 basic_clean(text):
    text = ftfy.fix_text(text)
    text = html.unescape(html.unescape(text))
    return text.strip()


def whitespace_clean(text):
    text = re.sub(r'\s+', ' ', text)
    text = text.strip()
    return text

class Tokenize:

    def __init__(self, tokenizer, max_seq_len=77, truncate=True):
        self.tokenizer = tokenizer
        self.max_seq_len = max_seq_len
        self.truncate = truncate

    def __call__(self, texts):
        expanded_dim = False
        if isinstance(texts, str):
            texts = [texts]
            expanded_dim = True

        sot_token = self.tokenizer.encoder['<|startoftext|>']
        eot_token = self.tokenizer.encoder['<|endoftext|>']
        all_tokens = [[sot_token] + self.tokenizer.encode(text) + [eot_token] for text in texts]
        result = torch.zeros(len(all_tokens), self.max_seq_len, dtype=torch.long)

        for i, tokens in enumerate(all_tokens):
            if len(tokens) > self.max_seq_len:
                if self.truncate:
                    tokens = tokens[:self.max_seq_len]
                    tokens[-1] = eot_token
                else:
                    raise RuntimeError(f'Input {texts[i]} is too long for context length {self.max_seq_len}')
            result[i, :len(tokens)] = torch.tensor(tokens)

        if expanded_dim:
            return result[0]

        return result


class SimpleTokenizer(object):

    def __init__(self, bpe_path: str = default_bpe()):
        self.byte_encoder = bytes_to_unicode()
        self.byte_decoder = {v: k for k, v in self.byte_encoder.items()}
        merges = gzip.open(bpe_path).read().decode('utf-8').split('\n')
        merges = merges[1:49152 - 256 - 2 + 1]
        merges = [tuple(merge.split()) for merge in merges]
        vocab = list(bytes_to_unicode().values())
        vocab = vocab + [v + '</w>' for v in vocab]
        for merge in merges:
            vocab.append(''.join(merge))
        vocab.extend(['<|startoftext|>', '<|endoftext|>'])
        self.encoder = dict(zip(vocab, range(len(vocab))))
        self.decoder = {v: k for k, v in self.encoder.items()}
        self.bpe_ranks = dict(zip(merges, range(len(merges))))
        self.cache = {'<|startoftext|>': '<|startoftext|>', '<|endoftext|>': '<|endoftext|>'}
        self.pat = re.compile(
            r"""<\|startoftext\|>|<\|endoftext\|>|'s|'t|'re|'ve|'m|'ll|'d|[\p{L}]+|[\p{N}]|[^\s\p{L}\p{N}]+""",
            re.IGNORECASE)

    def bpe(self, token):
        if token in self.cache:
            return self.cache[token]
        word = tuple(token[:-1]) + (token[-1] + '</w>', )
        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)
                    new_word.extend(word[i:j])
                    i = j
                except:  # noqa: E722
                    new_word.extend(word[i:])
                    break

                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)
        self.cache[token] = word
        return word

    def encode(self, text):
        bpe_tokens = []
        text = whitespace_clean(basic_clean(text)).lower()
        for token in re.findall(self.pat, text):
            token = ''.join(self.byte_encoder[b] for b in token.encode('utf-8'))
            bpe_tokens.extend(self.encoder[bpe_token] for bpe_token in self.bpe(token).split(' '))
        return bpe_tokens

    def decode(self, tokens):
        text = ''.join([self.decoder[token] for token in tokens])
        text = bytearray([self.byte_decoder[c] for c in text]).decode('utf-8', errors='replace').replace('</w>', ' ')
        return text