# coding=utf-8
# Copyright (c) 2019 NVIDIA CORPORATION. All rights reserved.
# Copyright 2018 The Google AI Language Team Authors.
#
# 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.

"""Create masked LM/next sentence masked_lm TF examples for BERT."""

from __future__ import absolute_import, division, print_function, unicode_literals

import argparse
import logging
import os
import random
from io import open
import h5py
import tensorflow as tf
import numpy as np
from tqdm import tqdm, trange

from tokenization import BertTokenizer
import tokenization as tokenization

import random
import collections

class TrainingInstance(object):
  """A single training instance (sentence pair)."""

  def __init__(self, tokens, segment_ids, masked_lm_positions, masked_lm_labels,
               is_random_next):
    self.tokens = tokens
    self.segment_ids = segment_ids
    self.is_random_next = is_random_next
    self.masked_lm_positions = masked_lm_positions
    self.masked_lm_labels = masked_lm_labels

  def __str__(self):
    s = ""
    s += "tokens: %s\n" % (" ".join(
        [tokenization.printable_text(x) for x in self.tokens]))
    s += "segment_ids: %s\n" % (" ".join([str(x) for x in self.segment_ids]))
    s += "is_random_next: %s\n" % self.is_random_next
    s += "masked_lm_positions: %s\n" % (" ".join(
        [str(x) for x in self.masked_lm_positions]))
    s += "masked_lm_labels: %s\n" % (" ".join(
        [tokenization.printable_text(x) for x in self.masked_lm_labels]))
    s += "\n"
    return s

  def __repr__(self):
    return self.__str__()


def write_instance_to_example_files(instances, tokenizer, max_seq_length,
                                    max_predictions_per_seq, output_files, output_formats="tfrecord"):
  """Create TF example files from `TrainingInstance`s."""
  writers = []
  for output_file in output_files:
    writers.append(tf.python_io.TFRecordWriter(output_file))

  writer_index = 0

  total_written = 0
  if 'hdf5' in output_formats:
    features_hdf5 = collections.OrderedDict()
    num_instances = len(instances)
    features_hdf5["input_ids"] = np.zeros([num_instances, max_seq_length], dtype="int32")
    features_hdf5["input_mask"] = np.zeros([num_instances, max_seq_length], dtype="int32")
    features_hdf5["segment_ids"] = np.zeros([num_instances, max_seq_length], dtype="int32")
    features_hdf5["masked_lm_positions"] =  np.zeros([num_instances, max_predictions_per_seq], dtype="int32")
    features_hdf5["masked_lm_ids"] = np.zeros([num_instances, max_predictions_per_seq], dtype="int32")
    features_hdf5["next_sentence_labels"] = np.zeros(num_instances, dtype="int32")

  for (inst_index, instance) in enumerate(instances):
    input_ids = tokenizer.convert_tokens_to_ids(instance.tokens)
    input_mask = [1] * len(input_ids)
    segment_ids = list(instance.segment_ids)
    assert len(input_ids) <= max_seq_length

    while len(input_ids) < max_seq_length:
      input_ids.append(0)
      input_mask.append(0)
      segment_ids.append(0)

    assert len(input_ids) == max_seq_length
    assert len(input_mask) == max_seq_length
    assert len(segment_ids) == max_seq_length

    masked_lm_positions = list(instance.masked_lm_positions)
    masked_lm_ids = tokenizer.convert_tokens_to_ids(instance.masked_lm_labels)
    masked_lm_weights = [1.0] * len(masked_lm_ids)

    while len(masked_lm_positions) < max_predictions_per_seq:
      masked_lm_positions.append(0)
      masked_lm_ids.append(0)
      masked_lm_weights.append(0.0)

    next_sentence_label = 1 if instance.is_random_next else 0

    features = collections.OrderedDict()
    features["input_ids"] = create_int_feature(input_ids)
    features["input_mask"] = create_int_feature(input_mask)
    features["segment_ids"] = create_int_feature(segment_ids)
    features["masked_lm_positions"] = create_int_feature(masked_lm_positions)
    features["masked_lm_ids"] = create_int_feature(masked_lm_ids)
    features["masked_lm_weights"] = create_float_feature(masked_lm_weights)
    features["next_sentence_labels"] = create_int_feature([next_sentence_label])

    if 'tfrecord' in output_formats:
      tf_example = tf.train.Example(features=tf.train.Features(feature=features))
      writers[writer_index].write(tf_example.SerializeToString())
    if 'hdf5' in output_formats:
      features_hdf5["input_ids"][inst_index] = input_ids
      features_hdf5["input_mask"][inst_index] = input_mask
      features_hdf5["segment_ids"][inst_index] = segment_ids
      features_hdf5["masked_lm_positions"][inst_index] = masked_lm_positions
      features_hdf5["masked_lm_ids"][inst_index] = masked_lm_ids
      features_hdf5["next_sentence_labels"][inst_index] = next_sentence_label
    if 'tfrecord' not in output_formats and 'hdf5' not in output_formats:
      assert False, 'Either empty output_formats list or unsupported type specified. Try: tfrecord or hdf5'

    writer_index = (writer_index + 1) % len(writers)

    total_written += 1

    if inst_index < 20:
      tf.compat.v1.logging.info("*** Example ***")
      tf.compat.v1.logging.info("tokens: %s" % " ".join(
          [tokenization.printable_text(x) for x in instance.tokens]))

      for feature_name in features.keys():
        feature = features[feature_name]
        values = []
        if feature.int64_list.value:
          values = feature.int64_list.value
        elif feature.float_list.value:
          values = feature.float_list.value
        tf.compat.v1.logging.info(
            "%s: %s" % (feature_name, " ".join([str(x) for x in values])))

  for writer in writers:
    writer.close()

  if 'hdf5' in output_formats:
    f = h5py.File(output_file, 'w')
    f.create_dataset("input_ids", data=features_hdf5["input_ids"], dtype='i4', compression='gzip')
    f.create_dataset("input_mask", data=features_hdf5["input_mask"], dtype='i1', compression='gzip')
    f.create_dataset("segment_ids", data=features_hdf5["segment_ids"], dtype='i1', compression='gzip')
    f.create_dataset("masked_lm_positions", data=features_hdf5["masked_lm_positions"], dtype='i4', compression='gzip')
    f.create_dataset("masked_lm_ids", data=features_hdf5["masked_lm_ids"], dtype='i4', compression='gzip')
    f.create_dataset("next_sentence_labels", data=features_hdf5["next_sentence_labels"], dtype='i1', compression='gzip')
    f.flush()
    f.close()

  tf.compat.v1.logging.info("Wrote %d total instances", total_written)


def create_int_feature(values):
  feature = tf.train.Feature(int64_list=tf.train.Int64List(value=list(values)))
  return feature


def create_float_feature(values):
  feature = tf.train.Feature(float_list=tf.train.FloatList(value=list(values)))
  return feature


def create_training_instances(input_files, tokenizer, max_seq_length,
                              dupe_factor, short_seq_prob, masked_lm_prob,
                              max_predictions_per_seq, rng):
    """Create `TrainingInstance`s from raw text."""
    all_documents = [[]]

    # Input file format:
    # (1) One sentence per line. These should ideally be actual sentences, not
    # entire paragraphs or arbitrary spans of text. (Because we use the
    # sentence boundaries for the "next sentence prediction" task).
    # (2) Blank lines between documents. Document boundaries are needed so
    # that the "next sentence prediction" task doesn't span between documents.
    for input_file in input_files:
        print("creating instance from {}".format(input_file))
        with open(input_file, "r") as reader:
            while True:
                line = tokenization.convert_to_unicode(reader.readline())
                if not line:
                    break
                line = line.strip()

                # Empty lines are used as document delimiters
                if not line:
                    all_documents.append([])
                tokens = tokenizer.tokenize(line)
                if tokens:
                    all_documents[-1].append(tokens)

    # Remove empty documents
    all_documents = [x for x in all_documents if x]
    rng.shuffle(all_documents)

    vocab_words = list(tokenizer.vocab.keys())
    instances = []
    for _ in range(dupe_factor):
        for document_index in range(len(all_documents)):
            instances.extend(
                create_instances_from_document(
                    all_documents, document_index, max_seq_length, short_seq_prob,
                    masked_lm_prob, max_predictions_per_seq, vocab_words, rng))

    rng.shuffle(instances)
    return instances


def create_instances_from_document(
        all_documents, document_index, max_seq_length, short_seq_prob,
        masked_lm_prob, max_predictions_per_seq, vocab_words, rng):
    """Creates `TrainingInstance`s for a single document."""
    document = all_documents[document_index]

    # Account for [CLS], [SEP], [SEP]
    max_num_tokens = max_seq_length - 3

    # We *usually* want to fill up the entire sequence since we are padding
    # to `max_seq_length` anyways, so short sequences are generally wasted
    # computation. However, we *sometimes*
    # (i.e., short_seq_prob == 0.1 == 10% of the time) want to use shorter
    # sequences to minimize the mismatch between pre-training and fine-tuning.
    # The `target_seq_length` is just a rough target however, whereas
    # `max_seq_length` is a hard limit.
    target_seq_length = max_num_tokens
    if rng.random() < short_seq_prob:
        target_seq_length = rng.randint(2, max_num_tokens)

    # We DON'T just concatenate all of the tokens from a document into a long
    # sequence and choose an arbitrary split point because this would make the
    # next sentence prediction task too easy. Instead, we split the input into
    # segments "A" and "B" based on the actual "sentences" provided by the user
    # input.
    instances = []
    current_chunk = []
    current_length = 0
    i = 0
    while i < len(document):
        segment = document[i]
        current_chunk.append(segment)
        current_length += len(segment)
        if i == len(document) - 1 or current_length >= target_seq_length:
            if current_chunk:
                # `a_end` is how many segments from `current_chunk` go into the `A`
                # (first) sentence.
                a_end = 1
                if len(current_chunk) >= 2:
                    a_end = rng.randint(1, len(current_chunk) - 1)

                tokens_a = []
                for j in range(a_end):
                    tokens_a.extend(current_chunk[j])

                tokens_b = []
                # Random next
                is_random_next = False
                if len(current_chunk) == 1 or rng.random() < 0.5:
                    is_random_next = True
                    target_b_length = target_seq_length - len(tokens_a)

                    # This should rarely go for more than one iteration for large
                    # corpora. However, just to be careful, we try to make sure that
                    # the random document is not the same as the document
                    # we're processing.
                    for _ in range(10):
                        random_document_index = rng.randint(0, len(all_documents) - 1)
                        if random_document_index != document_index:
                            break

                    #If picked random document is the same as the current document
                    if random_document_index == document_index:
                        is_random_next = False
                            
                    random_document = all_documents[random_document_index]
                    random_start = rng.randint(0, len(random_document) - 1)
                    for j in range(random_start, len(random_document)):
                        tokens_b.extend(random_document[j])
                        if len(tokens_b) >= target_b_length:
                            break
                    # We didn't actually use these segments so we "put them back" so
                    # they don't go to waste.
                    num_unused_segments = len(current_chunk) - a_end
                    i -= num_unused_segments
                # Actual next
                else:
                    is_random_next = False
                    for j in range(a_end, len(current_chunk)):
                        tokens_b.extend(current_chunk[j])
                truncate_seq_pair(tokens_a, tokens_b, max_num_tokens, rng)

                assert len(tokens_a) >= 1
                assert len(tokens_b) >= 1

                tokens = []
                segment_ids = []
                tokens.append("[CLS]")
                segment_ids.append(0)
                for token in tokens_a:
                    tokens.append(token)
                    segment_ids.append(0)

                tokens.append("[SEP]")
                segment_ids.append(0)

                for token in tokens_b:
                    tokens.append(token)
                    segment_ids.append(1)
                tokens.append("[SEP]")
                segment_ids.append(1)

                (tokens, masked_lm_positions,
                 masked_lm_labels) = create_masked_lm_predictions(
                    tokens, masked_lm_prob, max_predictions_per_seq, vocab_words, rng)
                instance = TrainingInstance(
                    tokens=tokens,
                    segment_ids=segment_ids,
                    is_random_next=is_random_next,
                    masked_lm_positions=masked_lm_positions,
                    masked_lm_labels=masked_lm_labels)
                instances.append(instance)
            current_chunk = []
            current_length = 0
        i += 1

    return instances


MaskedLmInstance = collections.namedtuple("MaskedLmInstance",
                                          ["index", "label"])


def create_masked_lm_predictions(tokens, masked_lm_prob,
                                 max_predictions_per_seq, vocab_words, rng):
    """Creates the predictions for the masked LM objective."""

    cand_indexes = []
    for (i, token) in enumerate(tokens):
        if token == "[CLS]" or token == "[SEP]":
            continue
        cand_indexes.append(i)

    rng.shuffle(cand_indexes)

    output_tokens = list(tokens)

    num_to_predict = min(max_predictions_per_seq,
                         max(1, int(round(len(tokens) * masked_lm_prob))))

    masked_lms = []
    covered_indexes = set()
    for index in cand_indexes:
        if len(masked_lms) >= num_to_predict:
            break
        if index in covered_indexes:
            continue
        covered_indexes.add(index)

        masked_token = None
        # 80% of the time, replace with [MASK]
        if rng.random() < 0.8:
            masked_token = "[MASK]"
        else:
            # 10% of the time, keep original
            if rng.random() < 0.5:
                masked_token = tokens[index]
            # 10% of the time, replace with random word
            else:
                masked_token = vocab_words[rng.randint(0, len(vocab_words) - 1)]

        output_tokens[index] = masked_token

        masked_lms.append(MaskedLmInstance(index=index, label=tokens[index]))

    masked_lms = sorted(masked_lms, key=lambda x: x.index)

    masked_lm_positions = []
    masked_lm_labels = []
    for p in masked_lms:
        masked_lm_positions.append(p.index)
        masked_lm_labels.append(p.label)

    return (output_tokens, masked_lm_positions, masked_lm_labels)


def truncate_seq_pair(tokens_a, tokens_b, max_num_tokens, rng):
    """Truncates a pair of sequences to a maximum sequence length."""
    while True:
        total_length = len(tokens_a) + len(tokens_b)
        if total_length <= max_num_tokens:
            break

        trunc_tokens = tokens_a if len(tokens_a) > len(tokens_b) else tokens_b
        assert len(trunc_tokens) >= 1

        # We want to sometimes truncate from the front and sometimes from the
        # back to add more randomness and avoid biases.
        if rng.random() < 0.5:
            del trunc_tokens[0]
        else:
            trunc_tokens.pop()


def main():
    parser = argparse.ArgumentParser()
    ## Required parameters
    parser.add_argument("--vocab_file",
                        default=None,
                        type=str,
                        required=True,
                        help="The vocabulary the BERT model will train on.")
    parser.add_argument("--input_file",
                        default=None,
                        type=str,
                        required=True,
                        help="The input train corpus. can be directory with .txt files or a path to a single file")
    parser.add_argument("--output_file",
                        default=None,
                        type=str,
                        required=True,
                        help="The output file where the model checkpoints will be written.")

    ## Other parameters
    # int
    parser.add_argument("--max_seq_length",
                        default=128,
                        type=int,
                        help="The maximum total input sequence length after WordPiece tokenization. \n"
                             "Sequences longer than this will be truncated, and sequences shorter \n"
                             "than this will be padded.")
    parser.add_argument("--dupe_factor",
                        default=10,
                        type=int,
                        help="Number of times to duplicate the input data (with different masks).")
    parser.add_argument("--max_predictions_per_seq",
                        default=20,
                        type=int,
                        help="Maximum sequence length.")

    # floats

    parser.add_argument("--masked_lm_prob",
                        default=0.15,
                        type=float,
                        help="Masked LM probability.")

    parser.add_argument("--short_seq_prob",
                        default=0.1,
                        type=float,
                        help="Probability to create a sequence shorter than maximum sequence length")

    parser.add_argument("--do_lower_case",
                        action='store_true',
                        default=True,
                        help="Whether to lower case the input text. True for uncased models, False for cased models.")
    parser.add_argument('--random_seed',
                        type=int,
                        default=12345,
                        help="random seed for initialization")

    args = parser.parse_args()

    tokenizer = BertTokenizer(args.vocab_file, do_lower_case=args.do_lower_case)

    input_files = []
    if os.path.isfile(args.input_file):
        input_files.append(args.input_file)
    elif os.path.isdir(args.input_file):
        input_files = [os.path.join(args.input_file, f) for f in os.listdir(args.input_file) if
                       (os.path.isfile(os.path.join(args.input_file, f)) and f.endswith('.txt'))]
    else:
        raise ValueError("{} is not a valid path".format(args.input_file))

    rng = random.Random(args.random_seed)
    instances = create_training_instances(
        input_files, tokenizer, args.max_seq_length, args.dupe_factor,
        args.short_seq_prob, args.masked_lm_prob, args.max_predictions_per_seq,
        rng)

    output_files = args.output_file.split(",")
    print("*** Writing to output files ***")
    for output_file in output_files:
        print(output_file)


    write_instance_to_example_files(instances, tokenizer, args.max_seq_length,
                                       args.max_predictions_per_seq, output_files)


if __name__ == "__main__":
    main()
