# Copyright 2020 The HuggingFace Team. 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.

import json
import os, collections
import pickle
import logging

import numpy as np
import six



def whitespace_tokenize(text):
    """Runs basic whitespace cleaning and splitting on a piece of text."""
    text = text.strip()
    if not text:
        return []
    tokens = text.split()
    return tokens

class SquadExample(object):
    """A single training/test example for simple sequence classification.

         For examples without an answer, the start and end position are -1.
    """

    def __init__(self,
                qas_id,
                question_text,
                doc_tokens,
                orig_answer_text=None,
                start_position=None,
                end_position=None,
                is_impossible=False,
                answers=[]):
        self.qas_id = qas_id
        self.question_text = question_text
        self.doc_tokens = doc_tokens
        self.orig_answer_text = orig_answer_text
        self.start_position = start_position
        self.end_position = end_position
        self.is_impossible = is_impossible
        self.answers = answers

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

    def __repr__(self):
        s = ""
        s += "qas_id: %s" % (str(self.qas_id))
        s += ", question_text: %s" % (
                str(self.question_text))
        s += ", doc_tokens: [%s]" % (" ".join(self.doc_tokens))
        if self.start_position:
            s += ", start_position: %d" % (self.start_position)
        if self.start_position:
            s += ", end_position: %d" % (self.end_position)
        if self.start_position:
            s += ", is_impossible: %r" % (self.is_impossible)
        if self.orig_answer_text:
            s += ", ori_answer_text: %s" % (self.orig_answer_text)
            s += ", answer_text: %s" % (' '.join(self.doc_tokens[self.start_position: self.end_position + 1]))
        return s

class SquadFeature(object):
    """A single set of features of data."""

    def __init__(self,
                unique_id,
                example_index,
                doc_span_index,
                tokens,
                token_to_orig_map,
                token_is_max_context,
                input_ids,
                p_mask,
                doc_offset,
                start_position=None,
                end_position=None,
                is_impossible=None):
        self.unique_id = unique_id
        self.example_index = example_index
        self.doc_span_index = doc_span_index
        self.tokens = tokens
        self.p_mask = p_mask
        self.doc_offset = doc_offset
        self.token_to_orig_map = token_to_orig_map
        self.token_is_max_context = token_is_max_context
        self.input_ids = input_ids
        self.start_position = start_position
        self.end_position = end_position
        self.is_impossible = is_impossible


def read_squad_examples(input_file, is_training, version_2_with_negative):
    """Read a SQuAD json file into a list of SquadExample."""
    with open(input_file, "r") as reader:
        input_data = json.load(reader)["data"]

    def is_whitespace(c):
        if c == " " or c == "\t" or c == "\r" or c == "\n" or ord(c) == 0x202F:
            return True
        return False

    examples = []
    for entry in input_data:
        for paragraph in entry["paragraphs"]:
            paragraph_text = paragraph["context"]
            doc_tokens = []
            char_to_word_offset = []
            prev_is_whitespace = True
            for c in paragraph_text:
                if is_whitespace(c):
                    prev_is_whitespace = True
                else:
                    if prev_is_whitespace:
                        doc_tokens.append(c)
                    else:
                        doc_tokens[-1] += c
                    prev_is_whitespace = False
                char_to_word_offset.append(len(doc_tokens) - 1)

            for qa in paragraph["qas"]:
                qas_id = qa["id"]
                question_text = qa["question"]
                start_position = None
                end_position = None
                orig_answer_text = None
                is_impossible = qa.get("is_impossible", False)
                answers = []
                if is_training:
                    if (len(qa["answers"]) != 1) and (not is_impossible):
                        raise ValueError(
                                "For training, each question should have exactly 1 answer.")
                    if not is_impossible:
                        answer = qa["answers"][0]
                        orig_answer_text = answer["text"]
                        answer_offset = answer["answer_start"]
                        answer_length = len(orig_answer_text)
                        start_position = char_to_word_offset[answer_offset]
                        end_position = char_to_word_offset[answer_offset + answer_length - 1]
                        # Only add answers where the text can be exactly recovered from the
                        # document. If this CAN'T happen it's likely due to weird Unicode
                        # stuff so we will just skip the example.
                        #
                        # Note that this means for training mode, every example is NOT
                        # guaranteed to be preserved.
                        actual_text = " ".join(
                                doc_tokens[start_position:(end_position + 1)])
                        cleaned_answer_text = " ".join(
                                whitespace_tokenize(orig_answer_text))
                        if actual_text.find(cleaned_answer_text) == -1:
                            print("Could not find answer: '%s' vs. '%s'",
                                    actual_text, cleaned_answer_text)
                            continue
                    else:
                        start_position = -1
                        end_position = -1
                        orig_answer_text = ""
                elif not is_impossible:
                    answers = qa["answers"]

                example = SquadExample(
                        qas_id=qas_id,
                        question_text=question_text,
                        doc_tokens=doc_tokens,
                        orig_answer_text=orig_answer_text,
                        start_position=start_position,
                        end_position=end_position,
                        is_impossible=is_impossible,
                        answers=answers)
                examples.append(example)
    return examples

def _improve_answer_span(doc_tokens, input_start, input_end, tokenizer,
                                                 orig_answer_text):
    """Returns tokenized answer spans that better match the annotated answer."""

    # The SQuAD annotations are character based. We first project them to
    # whitespace-tokenized words. But then after WordPiece tokenization, we can
    # often find a "better match". For example:
    #
    #   Question: What year was John Smith born?
    #   Context: The leader was John Smith (1895-1943).
    #   Answer: 1895
    #
    # The original whitespace-tokenized answer will be "(1895-1943).". However
    # after tokenization, our tokens will be "( 1895 - 1943 ) .". So we can match
    # the exact answer, 1895.
    #
    # However, this is not always possible. Consider the following:
    #
    #   Question: What country is the top exporter of electornics?
    #   Context: The Japanese electronics industry is the lagest in the world.
    #   Answer: Japan
    #
    # In this case, the annotator chose "Japan" as a character sub-span of
    # the word "Japanese". Since our WordPiece tokenizer does not split
    # "Japanese", we just use "Japanese" as the annotation. This is fairly rare
    # in SQuAD, but does happen.
    tok_answer_text = " ".join(tokenizer.tokenize(orig_answer_text))

    for new_start in range(input_start, input_end + 1):
        for new_end in range(input_end, new_start - 1, -1):
            text_span = " ".join(doc_tokens[new_start:(new_end + 1)])
            if text_span == tok_answer_text:
                return (new_start, new_end)

    return (input_start, input_end)


def _check_is_max_context(doc_spans, cur_span_index, position):
    """Check if this is the 'max context' doc span for the token."""

    # Because of the sliding window approach taken to scoring documents, a single
    # token can appear in multiple documents. E.g.
    #  Doc: the man went to the store and bought a gallon of milk
    #  Span A: the man went to the
    #  Span B: to the store and bought
    #  Span C: and bought a gallon of
    #  ...
    #
    # Now the word 'bought' will have two scores from spans B and C. We only
    # want to consider the score with "maximum context", which we define as
    # the *minimum* of its left and right context (the *sum* of left and
    # right context will always be the same, of course).
    #
    # In the example the maximum context for 'bought' would be span C since
    # it has 1 left context and 3 right context, while span B has 4 left context
    # and 0 right context.
    best_score = None
    best_span_index = None
    for (span_index, doc_span) in enumerate(doc_spans):
        end = doc_span.start + doc_span.length - 1
        if position < doc_span.start:
            continue
        if position > end:
            continue
        num_left_context = position - doc_span.start
        num_right_context = end - position
        score = min(num_left_context, num_right_context) + 0.01 * doc_span.length
        if best_score is None or score > best_score:
            best_score = score
            best_span_index = span_index

    return cur_span_index == best_span_index

def squad_convert_examples_to_features(examples, tokenizer, max_seq_length, doc_stride,
                                       max_query_length, is_training, 
                                       cls_token='[CLS]', sep_token='[SEP]', additional_seq=True):
    features = []
    unique_id = 1000000000
    for (example_index, example) in enumerate(examples):
        query_tokens = tokenizer.tokenize(example.question_text)
        if len(query_tokens) > max_query_length:
            query_tokens = query_tokens[0:max_query_length]

        tok_to_orig_index = []
        orig_to_tok_index = []
        all_doc_tokens = []
        for (i, token) in enumerate(example.doc_tokens):
            orig_to_tok_index.append(len(all_doc_tokens))
            sub_tokens = tokenizer.tokenize(token)
            for sub_token in sub_tokens:
                tok_to_orig_index.append(i)
                all_doc_tokens.append(sub_token)
        tok_start_position = None
        tok_end_position = None
        if is_training and example.is_impossible:
            tok_start_position = -1
            tok_end_position = -1
        if is_training and not example.is_impossible:
            tok_start_position = orig_to_tok_index[example.start_position]
            if example.end_position < len(example.doc_tokens) - 1:
                tok_end_position = orig_to_tok_index[example.end_position + 1] - 1
            else:
                tok_end_position = len(all_doc_tokens) - 1
            (tok_start_position, tok_end_position) = _improve_answer_span(
                    all_doc_tokens, tok_start_position, tok_end_position, tokenizer,
                    example.orig_answer_text)

        max_tokens_for_doc = max_seq_length - len(query_tokens) - 3

        # We can have documents that are longer than the maximum sequence length.
        # To deal with this we do a sliding window approach, where we take chunks
        # of the up to our max length with a stride of `doc_stride`.
        _DocSpan = collections.namedtuple(  # pylint: disable=invalid-name
                "DocSpan", ["start", "length"])
        doc_spans = []
        start_offset = 0
        while start_offset < len(all_doc_tokens):
            length = len(all_doc_tokens) - start_offset
            if length > max_tokens_for_doc:
                length = max_tokens_for_doc
            doc_spans.append(_DocSpan(start=start_offset, length=length))
            if start_offset + length == len(all_doc_tokens):
                break
            start_offset += min(length, doc_stride)
        for (doc_span_index, doc_span) in enumerate(doc_spans):
            tokens = []
            p_mask = []
            token_to_orig_map = {}
            token_is_max_context = {}
            tokens.append(cls_token)
            p_mask.append(0)
            for token in query_tokens:
                tokens.append(token)
                p_mask.append(1)
            tokens.append(sep_token)
            p_mask.append(1)
            if additional_seq:
                tokens.append(sep_token)
                p_mask.append(1)
            doc_offset = len(tokens)
            for i in range(doc_span.length):
                split_token_index = doc_span.start + i
                token_to_orig_map[len(tokens)] = tok_to_orig_index[split_token_index]

                is_max_context = _check_is_max_context(doc_spans, doc_span_index, split_token_index)
                token_is_max_context[len(tokens)] = is_max_context
                tokens.append(all_doc_tokens[split_token_index])
                p_mask.append(0)
            tokens.append(sep_token)
            p_mask.append(1)
            input_ids = tokenizer.convert_tokens_to_ids(tokens)
            assert len(p_mask) == len(input_ids)
            start_position = None
            end_position = None
            if is_training and not example.is_impossible:
                # For training, if our document chunk does not contain an annotation
                # we throw it out, since there is nothing to predict.
                doc_start = doc_span.start
                doc_end = doc_span.start + doc_span.length - 1
                out_of_span = False
                if not (tok_start_position >= doc_start and tok_end_position <= doc_end):
                    out_of_span = True
                if out_of_span:
                    start_position = 0
                    end_position = 0
                else:
                    start_position = tok_start_position - doc_start + doc_offset
                    end_position = tok_end_position - doc_start + doc_offset

            if is_training and example.is_impossible:
                start_position = 0
                end_position = 0

            if example_index < 10:
                print("*** Example ***")
                print("unique_id: %s" % (unique_id))
                print("example_index: %s" % (example_index))
                print("doc_span_index: %s" % (doc_span_index))
                print("tokens: %s" % " ".join(
                        [x for x in tokens]))
                print("token_to_orig_map: %s" % " ".join(
                        ["%d:%d" % (x, y) for (x, y) in six.iteritems(token_to_orig_map)]))
                print("token_is_max_context: %s" % " ".join([
                        "%d:%s" % (x, y) for (x, y) in six.iteritems(token_is_max_context)
                ]))
                print("input_ids: %s" % " ".join([str(x) for x in input_ids]))
                if is_training and example.is_impossible:
                    print("impossible example")
                if is_training and not example.is_impossible:
                    answer_text = " ".join(tokens[start_position:(end_position + 1)])
                    print("start_position: %d" % (start_position))
                    print("end_position: %d" % (end_position))
                    print("answer: %s" % (answer_text))

            feature = SquadFeature(
                    unique_id=unique_id,
                    example_index=example_index,
                    doc_span_index=doc_span_index,
                    tokens=tokens,
                    token_to_orig_map=token_to_orig_map,
                    token_is_max_context=token_is_max_context,
                    input_ids=input_ids,
                    p_mask=p_mask,
                    doc_offset=doc_offset,
                    start_position=start_position,
                    end_position=end_position,
                    is_impossible=example.is_impossible)
            features.append(feature)
            unique_id += 1
    return features
