# Copyright 2020 Huawei Technologies Co., Ltd
#
# 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.
# ============================================================================
"""
imdb dataset parser.
"""
import os
from itertools import chain

import numpy as np
import gensim


class ImdbParser():
    """
    parse aclImdb data to features and labels.
    sentence->tokenized->encoded->padding->features
    """

    def __init__(self, imdb_path, glove_path, embed_size=300):
        self.__segs = ['train', 'test']
        self.__label_dic = {'pos': 1, 'neg': 0}
        self.__imdb_path = imdb_path
        self.__glove_dim = embed_size
        self.__glove_file = os.path.join(glove_path, 'glove.6B.' + str(self.__glove_dim) + 'd.txt')

        # properties
        self.__imdb_datas = {}
        self.__features = {}
        self.__labels = {}
        self.__vacab = {}
        self.__word2idx = {}
        self.__weight_np = {}
        self.__wvmodel = None

    def parse(self):
        """
        parse imdb data to memory
        """
        self.__wvmodel = gensim.models.KeyedVectors.load_word2vec_format(self.__glove_file)

        for seg in self.__segs:
            self.__parse_imdb_datas(seg)
            self.__parse_features_and_labels(seg)
            self.__gen_weight_np(seg)

    def __parse_imdb_datas(self, seg):
        """
        load data from txt
        """
        data_lists = []
        for label_name, label_id in self.__label_dic.items():
            sentence_dir = os.path.join(self.__imdb_path, seg, label_name)
            for file in os.listdir(sentence_dir):
                with open(os.path.join(sentence_dir, file), mode='r', encoding='utf8') as f:
                    sentence = f.read().replace('\n', '')
                    data_lists.append([sentence, label_id])
        self.__imdb_datas[seg] = data_lists

    def __parse_features_and_labels(self, seg):
        """
        parse features and labels
        """
        features = []
        labels = []
        for sentence, label in self.__imdb_datas[seg]:
            features.append(sentence)
            labels.append(label)

        self.__features[seg] = features
        self.__labels[seg] = labels

        # update feature to tokenized
        self.__updata_features_to_tokenized(seg)
        # parse vacab
        self.__parse_vacab(seg)
        # encode feature
        self.__encode_features(seg)
        # padding feature
        self.__padding_features(seg)

    def __updata_features_to_tokenized(self, seg):
        tokenized_features = []
        for sentence in self.__features[seg]:
            tokenized_sentence = [word.lower() for word in sentence.split(" ")]
            tokenized_features.append(tokenized_sentence)
        self.__features[seg] = tokenized_features

    def __parse_vacab(self, seg):
        # vocab
        tokenized_features = self.__features[seg]
        vocab = set(chain(*tokenized_features))
        self.__vacab[seg] = vocab

        # word_to_idx: {'hello': 1, 'world':111, ... '<unk>': 0}
        word_to_idx = {word: i + 1 for i, word in enumerate(vocab)}
        word_to_idx['<unk>'] = 0
        self.__word2idx[seg] = word_to_idx

    def __encode_features(self, seg):
        """ encode word to index """
        word_to_idx = self.__word2idx['train']
        encoded_features = []
        for tokenized_sentence in self.__features[seg]:
            encoded_sentence = []
            for word in tokenized_sentence:
                encoded_sentence.append(word_to_idx.get(word, 0))
            encoded_features.append(encoded_sentence)
        self.__features[seg] = encoded_features

    def __padding_features(self, seg, maxlen=500, pad=0):
        """ pad all features to the same length """
        padded_features = []
        for feature in self.__features[seg]:
            if len(feature) >= maxlen:
                padded_feature = feature[:maxlen]
            else:
                padded_feature = feature
                while len(padded_feature) < maxlen:
                    padded_feature.append(pad)
            padded_features.append(padded_feature)
        self.__features[seg] = padded_features

    def __gen_weight_np(self, seg):
        """
        generate weight by gensim
        """
        weight_np = np.zeros((len(self.__word2idx[seg]), self.__glove_dim), dtype=np.float32)
        for word, idx in self.__word2idx[seg].items():
            if word not in self.__wvmodel:
                continue
            word_vector = self.__wvmodel.get_vector(word)
            weight_np[idx, :] = word_vector

        self.__weight_np[seg] = weight_np

    def get_datas(self, seg):
        """
        return features, labels, and weight
        """
        features = np.array(self.__features[seg]).astype(np.int32)
        labels = np.array(self.__labels[seg]).astype(np.int32)
        weight = np.array(self.__weight_np[seg])
        return features, labels, weight