# coding=utf-8
# Copyright 2018 Google AI, Google Brain and Carnegie Mellon University Authors and the HuggingFace Inc. team.
# Copyright (c) 2018, NVIDIA CORPORATION.  All rights reserved.
#
# 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 Transformer XL model.
    Adapted from https://github.com/kimiyoung/transformer-xl.
"""
from __future__ import (absolute_import, division, print_function,
                        unicode_literals)

import glob
import logging
import os
import sys
from collections import Counter, OrderedDict
from io import open

import torch
import numpy as np

from .file_utils import cached_path
from .tokenization_utils import PreTrainedTokenizer

if sys.version_info[0] == 2:
    import cPickle as pickle
else:
    import pickle


logger = logging.getLogger(__name__)

VOCAB_FILES_NAMES = {'pretrained_vocab_file': 'vocab.bin', 'vocab_file': 'vocab.txt'}

PRETRAINED_VOCAB_FILES_MAP = {
    'pretrained_vocab_file':
    {
        'transfo-xl-wt103': "https://s3.amazonaws.com/models.huggingface.co/bert/transfo-xl-wt103-vocab.bin",
    }
}

PRETRAINED_POSITIONAL_EMBEDDINGS_SIZES = {
    'transfo-xl-wt103': None,
}

PRETRAINED_CORPUS_ARCHIVE_MAP = {
    'transfo-xl-wt103': "https://s3.amazonaws.com/models.huggingface.co/bert/transfo-xl-wt103-corpus.bin",
}
CORPUS_NAME = 'corpus.bin'

class TransfoXLTokenizer(PreTrainedTokenizer):
    """
    Transformer-XL tokenizer adapted from Vocab class in https://github.com/kimiyoung/transformer-xl
    """
    vocab_files_names = VOCAB_FILES_NAMES
    pretrained_vocab_files_map = PRETRAINED_VOCAB_FILES_MAP
    max_model_input_sizes = PRETRAINED_POSITIONAL_EMBEDDINGS_SIZES

    def __init__(self, special=None, min_freq=0, max_size=None, lower_case=False,
                 delimiter=None, vocab_file=None, pretrained_vocab_file=None,
                 never_split=None, unk_token="<unk>", eos_token="<eos>",
                 additional_special_tokens=["<formula>"], **kwargs):
        super(TransfoXLTokenizer, self).__init__(unk_token=unk_token, eos_token=eos_token,
                                                 additional_special_tokens=additional_special_tokens,
                                                 **kwargs)
        if never_split is None:
            never_split = self.all_special_tokens
        if special is None:
            special = []
        self.counter = Counter()
        self.special = special
        self.min_freq = min_freq
        self.max_size = max_size
        self.lower_case = lower_case
        self.delimiter = delimiter
        self.vocab_file = vocab_file
        self.never_split = never_split

        if pretrained_vocab_file is not None:
            # Hack because, honestly this tokenizer was not made to be used
            # in a library like ours, at all.
            vocab_dict = torch.load(pretrained_vocab_file)
            for key, value in vocab_dict.items():
                self.__dict__[key] = value

        if vocab_file is not None:
            self.build_vocab()

    def count_file(self, path, verbose=False, add_eos=False):
        if verbose: logger.info('counting file {} ...'.format(path))
        assert os.path.exists(path)

        sents = []
        with open(path, 'r', encoding='utf-8') as f:
            for idx, line in enumerate(f):
                if verbose and idx > 0 and idx % 500000 == 0:
                    logger.info('    line {}'.format(idx))
                symbols = self.tokenize(line, add_eos=add_eos)
                self.counter.update(symbols)
                sents.append(symbols)

        return sents

    def count_sents(self, sents, verbose=False):
        """
            sents : a list of sentences, each a list of tokenized symbols
        """
        if verbose: logger.info('counting {} sents ...'.format(len(sents)))
        for idx, symbols in enumerate(sents):
            if verbose and idx > 0 and idx % 500000 == 0:
                logger.info('    line {}'.format(idx))
            self.counter.update(symbols)

    def _build_from_file(self, vocab_file):
        self.idx2sym = []
        self.sym2idx = OrderedDict()

        with open(vocab_file, 'r', encoding='utf-8') as f:
            for line in f:
                symb = line.strip().split()[0]
                self.add_symbol(symb)
        if '<UNK>' in self.sym2idx:
            self.unk_idx = self.sym2idx['<UNK>']
        elif '<unk>' in self.sym2idx:
            self.unk_idx = self.sym2idx['<unk>']
        else:
            raise ValueError('No <unkown> token in vocabulary')

    def save_vocabulary(self, vocab_path):
        """Save the tokenizer vocabulary to a directory or file."""
        if os.path.isdir(vocab_path):
            vocab_file = os.path.join(vocab_path, VOCAB_FILES_NAMES['pretrained_vocab_file'])
        torch.save(self.__dict__, vocab_file)
        return (vocab_file,)

    def build_vocab(self):
        if self.vocab_file:
            logger.info('building vocab from {}'.format(self.vocab_file))
            self._build_from_file(self.vocab_file)
            logger.info('final vocab size {}'.format(len(self)))
        else:
            logger.info('building vocab with min_freq={}, max_size={}'.format(
                self.min_freq, self.max_size))
            self.idx2sym = []
            self.sym2idx = OrderedDict()

            for sym in self.special:
                self.add_special(sym)

            for sym, cnt in self.counter.most_common(self.max_size):
                if cnt < self.min_freq: break
                self.add_symbol(sym)

            logger.info('final vocab size {} from {} unique tokens'.format(
                len(self), len(self.counter)))

    def encode_file(self, path, ordered=False, verbose=False, add_eos=True,
            add_double_eos=False):
        if verbose: logger.info('encoding file {} ...'.format(path))
        assert os.path.exists(path)
        encoded = []
        with open(path, 'r', encoding='utf-8') as f:
            for idx, line in enumerate(f):
                if verbose and idx > 0 and idx % 500000 == 0:
                    logger.info('    line {}'.format(idx))
                symbols = self.tokenize(line, add_eos=add_eos,
                    add_double_eos=add_double_eos)
                encoded.append(self.convert_to_tensor(symbols))

        if ordered:
            encoded = torch.cat(encoded)

        return encoded

    def encode_sents(self, sents, ordered=False, verbose=False):
        if verbose: logger.info('encoding {} sents ...'.format(len(sents)))
        encoded = []
        for idx, symbols in enumerate(sents):
            if verbose and idx > 0 and idx % 500000 == 0:
                logger.info('    line {}'.format(idx))
            encoded.append(self.convert_to_tensor(symbols))

        if ordered:
            encoded = torch.cat(encoded)

        return encoded

    def add_special(self, sym):
        if sym not in self.sym2idx:
            self.idx2sym.append(sym)
            self.sym2idx[sym] = len(self.idx2sym) - 1
            setattr(self, '{}_idx'.format(sym.strip('<>')), self.sym2idx[sym])

    def add_symbol(self, sym):
        if sym not in self.sym2idx:
            self.idx2sym.append(sym)
            self.sym2idx[sym] = len(self.idx2sym) - 1

    def _convert_id_to_token(self, idx):
        """Converts an id in a token (BPE) using the vocab."""
        assert 0 <= idx < len(self), 'Index {} out of vocabulary range'.format(idx)
        return self.idx2sym[idx]

    def _convert_token_to_id(self, sym):
        """ Converts a token (str/unicode) in an id using the vocab. """
        if sym in self.sym2idx:
            return self.sym2idx[sym]
        else:
            # logger.info('encounter unk {}'.format(sym))
            # assert '<eos>' not in sym
            if hasattr(self, 'unk_idx'):
                return self.sym2idx.get(sym, self.unk_idx)
            # Backward compatibility with pre-trained models
            elif '<unk>' in self.sym2idx:
                return self.sym2idx['<unk>']
            elif '<UNK>' in self.sym2idx:
                return self.sym2idx['<UNK>']
            else:
                raise ValueError('Token not in vocabulary and no <unk> token in vocabulary for replacement')

    def convert_tokens_to_string(self, tokens):
        """ Converts a sequence of tokens (string) in a single string. """
        out_string = ' '.join(tokens).strip()
        return out_string

    def convert_to_tensor(self, symbols):
        return torch.LongTensor(self.convert_tokens_to_ids(symbols))

    @property
    def vocab_size(self):
        return len(self.idx2sym)

    def _tokenize(self, line, add_eos=False, add_double_eos=False):
        line = line.strip()
        # convert to lower case
        if self.lower_case:
            line = line.lower()

        # empty delimiter '' will evaluate False
        if self.delimiter == '':
            symbols = line
        else:
            symbols = line.split(self.delimiter)

        if add_double_eos: # lm1b
            return ['<S>'] + symbols + ['<S>']
        elif add_eos:
            return symbols + ['<eos>']
        else:
            return symbols


class LMOrderedIterator(object):
    def __init__(self, data, bsz, bptt, device='cpu', ext_len=None):
        """
            data -- LongTensor -- the LongTensor is strictly ordered
        """
        self.bsz = bsz
        self.bptt = bptt
        self.ext_len = ext_len if ext_len is not None else 0

        self.device = device

        # Work out how cleanly we can divide the dataset into bsz parts.
        self.n_step = data.size(0) // bsz

        # Trim off any extra elements that wouldn't cleanly fit (remainders).
        data = data.narrow(0, 0, self.n_step * bsz)

        # Evenly divide the data across the bsz batches.
        self.data = data.view(bsz, -1).t().contiguous().to(device)

        # Number of mini-batches
        self.n_batch = (self.n_step + self.bptt - 1) // self.bptt

    def get_batch(self, i, bptt=None):
        if bptt is None: bptt = self.bptt
        seq_len = min(bptt, self.data.size(0) - 1 - i)

        end_idx = i + seq_len
        beg_idx = max(0, i - self.ext_len)

        data = self.data[beg_idx:end_idx]
        target = self.data[i+1:i+1+seq_len]

        data_out = data.transpose(0, 1).contiguous().to(self.device)
        target_out = target.transpose(0, 1).contiguous().to(self.device)

        return data_out, target_out, seq_len

    def get_fixlen_iter(self, start=0):
        for i in range(start, self.data.size(0) - 1, self.bptt):
            yield self.get_batch(i)

    def get_varlen_iter(self, start=0, std=5, min_len=5, max_deviation=3):
        max_len = self.bptt + max_deviation * std
        i = start
        while True:
            bptt = self.bptt if np.random.random() < 0.95 else self.bptt / 2.
            bptt = min(max_len, max(min_len, int(np.random.normal(bptt, std))))
            data, target, seq_len = self.get_batch(i, bptt)
            i += seq_len
            yield data, target, seq_len
            if i >= self.data.size(0) - 2:
                break

    def __iter__(self):
        return self.get_fixlen_iter()


class LMShuffledIterator(object):
    def __init__(self, data, bsz, bptt, device='cpu', ext_len=None, shuffle=False):
        """
            data -- list[LongTensor] -- there is no order among the LongTensors
        """
        self.data = data

        self.bsz = bsz
        self.bptt = bptt
        self.ext_len = ext_len if ext_len is not None else 0

        self.device = device
        self.shuffle = shuffle

    def get_sent_stream(self):
        # index iterator
        epoch_indices = np.random.permutation(len(self.data)) if self.shuffle \
            else np.array(range(len(self.data)))

        # sentence iterator
        for idx in epoch_indices:
            yield self.data[idx]

    def stream_iterator(self, sent_stream):
        # streams for each data in the batch
        streams = [None] * self.bsz

        data = torch.LongTensor(self.bptt, self.bsz)
        target = torch.LongTensor(self.bptt, self.bsz)

        n_retain = 0

        while True:
            # data   : [n_retain+bptt x bsz]
            # target : [bptt x bsz]
            data[n_retain:].fill_(-1)
            target.fill_(-1)

            valid_batch = True

            for i in range(self.bsz):
                n_filled = 0
                try:
                    while n_filled < self.bptt:
                        if streams[i] is None or len(streams[i]) <= 1:
                            streams[i] = next(sent_stream)
                        # number of new tokens to fill in
                        n_new = min(len(streams[i]) - 1, self.bptt - n_filled)
                        # first n_retain tokens are retained from last batch
                        data[n_retain+n_filled:n_retain+n_filled+n_new, i] = \
                            streams[i][:n_new]
                        target[n_filled:n_filled+n_new, i] = \
                            streams[i][1:n_new+1]
                        streams[i] = streams[i][n_new:]
                        n_filled += n_new
                except StopIteration:
                    valid_batch = False
                    break

            if not valid_batch:
                return

            data_out = data.transpose(0, 1).contiguous().to(self.device)
            target_out = target.transpose(0, 1).contiguous().to(self.device)

            yield data_out, target_out, self.bptt

            n_retain = min(data.size(0), self.ext_len)
            if n_retain > 0:
                data[:n_retain] = data[-n_retain:]
            data.resize_(n_retain + self.bptt, data.size(1))

    def __iter__(self):
        # sent_stream is an iterator
        sent_stream = self.get_sent_stream()

        for batch in self.stream_iterator(sent_stream):
            yield batch


class LMMultiFileIterator(LMShuffledIterator):
    def __init__(self, paths, vocab, bsz, bptt, device='cpu', ext_len=None,
        shuffle=False):

        self.paths = paths
        self.vocab = vocab

        self.bsz = bsz
        self.bptt = bptt
        self.ext_len = ext_len if ext_len is not None else 0

        self.device = device
        self.shuffle = shuffle

    def get_sent_stream(self, path):
        sents = self.vocab.encode_file(path, add_double_eos=True)
        if self.shuffle:
            np.random.shuffle(sents)
        sent_stream = iter(sents)

        return sent_stream

    def __iter__(self):
        if self.shuffle:
            np.random.shuffle(self.paths)

        for path in self.paths:
            # sent_stream is an iterator
            sent_stream = self.get_sent_stream(path)
            for batch in self.stream_iterator(sent_stream):
                yield batch


class TransfoXLCorpus(object):
    @classmethod
    def from_pretrained(cls, pretrained_model_name_or_path, cache_dir=None, *inputs, **kwargs):
        """
        Instantiate a pre-processed corpus.
        """
        vocab = TransfoXLTokenizer.from_pretrained(pretrained_model_name_or_path, *inputs, **kwargs)
        if pretrained_model_name_or_path in PRETRAINED_CORPUS_ARCHIVE_MAP:
            corpus_file = PRETRAINED_CORPUS_ARCHIVE_MAP[pretrained_model_name_or_path]
        else:
            corpus_file = os.path.join(pretrained_model_name_or_path, CORPUS_NAME)
        # redirect to the cache, if necessary
        try:
            resolved_corpus_file = cached_path(corpus_file, cache_dir=cache_dir)
        except EnvironmentError:
            logger.error(
                "Corpus '{}' was not found in corpus list ({}). "
                "We assumed '{}' was a path or url but couldn't find files {} "
                "at this path or url.".format(
                    pretrained_model_name_or_path,
                    ', '.join(PRETRAINED_CORPUS_ARCHIVE_MAP.keys()),
                    pretrained_model_name_or_path,
                    corpus_file))
            return None
        if resolved_corpus_file == corpus_file:
            logger.info("loading corpus file {}".format(corpus_file))
        else:
            logger.info("loading corpus file {} from cache at {}".format(
                corpus_file, resolved_corpus_file))

        # Instantiate tokenizer.
        corpus = cls(*inputs, **kwargs)
        corpus_dict = torch.load(resolved_corpus_file)
        for key, value in corpus_dict.items():
            corpus.__dict__[key] = value
        corpus.vocab = vocab
        if corpus.train is not None:
            corpus.train = torch.tensor(corpus.train, dtype=torch.long)
        if corpus.valid is not None:
            corpus.valid = torch.tensor(corpus.valid, dtype=torch.long)
        if corpus.test is not None:
            corpus.test = torch.tensor(corpus.test, dtype=torch.long)
        return corpus

    def __init__(self, *args, **kwargs):
        self.vocab = TransfoXLTokenizer(*args, **kwargs)
        self.dataset = None
        self.train = None
        self.valid = None
        self.test = None

    def build_corpus(self, path, dataset):
        self.dataset = dataset

        if self.dataset in ['ptb', 'wt2', 'enwik8', 'text8']:
            self.vocab.count_file(os.path.join(path, 'train.txt'))
            self.vocab.count_file(os.path.join(path, 'valid.txt'))
            self.vocab.count_file(os.path.join(path, 'test.txt'))
        elif self.dataset == 'wt103':
            self.vocab.count_file(os.path.join(path, 'train.txt'))
        elif self.dataset == 'lm1b':
            train_path_pattern = os.path.join(
                path, '1-billion-word-language-modeling-benchmark-r13output',
                'training-monolingual.tokenized.shuffled', 'news.en-*')
            train_paths = glob.glob(train_path_pattern)
            # the vocab will load from file when build_vocab() is called

        self.vocab.build_vocab()

        if self.dataset in ['ptb', 'wt2', 'wt103']:
            self.train = self.vocab.encode_file(
                os.path.join(path, 'train.txt'), ordered=True)
            self.valid = self.vocab.encode_file(
                os.path.join(path, 'valid.txt'), ordered=True)
            self.test = self.vocab.encode_file(
                os.path.join(path, 'test.txt'), ordered=True)
        elif self.dataset in ['enwik8', 'text8']:
            self.train = self.vocab.encode_file(
                os.path.join(path, 'train.txt'), ordered=True, add_eos=False)
            self.valid = self.vocab.encode_file(
                os.path.join(path, 'valid.txt'), ordered=True, add_eos=False)
            self.test = self.vocab.encode_file(
                os.path.join(path, 'test.txt'), ordered=True, add_eos=False)
        elif self.dataset == 'lm1b':
            self.train = train_paths
            self.valid = self.vocab.encode_file(
                os.path.join(path, 'valid.txt'), ordered=False, add_double_eos=True)
            self.test = self.vocab.encode_file(
                os.path.join(path, 'test.txt'), ordered=False, add_double_eos=True)

    def get_iterator(self, split, *args, **kwargs):
        if split == 'train':
            if self.dataset in ['ptb', 'wt2', 'wt103', 'enwik8', 'text8']:
                data_iter = LMOrderedIterator(self.train, *args, **kwargs)
            elif self.dataset == 'lm1b':
                kwargs['shuffle'] = True
                data_iter = LMMultiFileIterator(self.train, self.vocab, *args, **kwargs)
        elif split in ['valid', 'test']:
            data = self.valid if split == 'valid' else self.test
            if self.dataset in ['ptb', 'wt2', 'wt103', 'enwik8', 'text8']:
                data_iter = LMOrderedIterator(data, *args, **kwargs)
            elif self.dataset == 'lm1b':
                data_iter = LMShuffledIterator(data, *args, **kwargs)

        return data_iter


def get_lm_corpus(datadir, dataset):
    fn = os.path.join(datadir, 'cache.pt')
    fn_pickle = os.path.join(datadir, 'cache.pkl')
    if os.path.exists(fn):
        logger.info('Loading cached dataset...')
        corpus = torch.load(fn_pickle)
    elif os.path.exists(fn):
        logger.info('Loading cached dataset from pickle...')
        with open(fn, "rb") as fp:
            corpus = pickle.load(fp)
    else:
        logger.info('Producing dataset {}...'.format(dataset))
        kwargs = {}
        if dataset in ['wt103', 'wt2']:
            kwargs['special'] = ['<eos>']
            kwargs['lower_case'] = False
        elif dataset == 'ptb':
            kwargs['special'] = ['<eos>']
            kwargs['lower_case'] = True
        elif dataset == 'lm1b':
            kwargs['special'] = []
            kwargs['lower_case'] = False
            kwargs['vocab_file'] = os.path.join(datadir, '1b_word_vocab.txt')
        elif dataset in ['enwik8', 'text8']:
            pass

        corpus = TransfoXLCorpus(datadir, dataset, **kwargs)
        torch.save(corpus, fn)

    return corpus
