from itertools import islice
import regex as re
import sys
from torchtext.vocab import build_vocab_from_iterator
from torch import nn
import torch
from torch.utils.data import IterableDataset
import itertools
import pandas as pd
from torch.utils.data import DataLoader
import csv
import os

def data_preprocessing(text):
    return re.sub(r'\p{P}', '', text.lower().replace('-\\n', '').replace('\\n', ' ').replace("'ll", " will").replace("-", "").replace("'ve", " have").replace("'s", " is"))

def get_words_from_line(line, s = True):
  line = line.rstrip()
  if s:
    yield '<s>'
  for m in re.finditer(r'[\p{L}0-9\*]+|\p{P}+', line):
     yield m.group(0).lower()
  if s:
    yield '</s>'


def get_word_lines_from_file(data):
  for line in data:
        yield get_words_from_line(line)


class SimpleBigramNeuralLanguageModel(nn.Module):
  def __init__(self, vocabulary_size, embedding_size):
      super(SimpleBigramNeuralLanguageModel, self).__init__()
      self.model = nn.Sequential(
          nn.Embedding(vocabulary_size, embedding_size),
          nn.Linear(embedding_size, vocabulary_size),
          nn.Softmax()
      )

  def forward(self, x):
      return self.model(x)


def look_ahead_iterator(gen):
   prev = None
   for item in gen:
      if prev is not None:
         yield (prev, item)
      prev = item

class Bigrams(IterableDataset):
  def __init__(self, text_file, vocabulary_size):
      self.vocab = build_vocab_from_iterator(
         get_word_lines_from_file(text_file),
         max_tokens = vocabulary_size,
         specials = ['<unk>'])
      self.vocab.set_default_index(self.vocab['<unk>'])
      self.vocabulary_size = vocabulary_size
      self.text_file = text_file

  def __iter__(self):
     return look_ahead_iterator(
         (self.vocab[t] for t in itertools.chain.from_iterable(get_word_lines_from_file(self.text_file))))

in_file = 'train/in.tsv.xz'
out_file = 'train/expected.tsv'

train_set = pd.read_csv(
    'train/in.tsv.xz',
    sep='\t',
    header=None,
    quoting=csv.QUOTE_NONE,
    nrows=35000)

train_labels = pd.read_csv(
    'train/expected.tsv',
    sep='\t',
    header=None,
    quoting=csv.QUOTE_NONE,
    nrows=35000)

data = pd.concat([train_set, train_labels], axis=1)
data = train_set[6] + train_set[0] + train_set[7]
data = data.apply(data_preprocessing)

vocab_size = 30000
embed_size = 150


bigram_data = Bigrams(data, vocab_size)

device = 'cpu'
model = SimpleBigramNeuralLanguageModel(vocab_size, embed_size).to(device)

if(not os.path.exists('model1.bin')):
    data = DataLoader(bigram_data, batch_size=5000)
    optimizer = torch.optim.Adam(model.parameters())
    criterion = torch.nn.NLLLoss()

    model.train()
    step = 0
    for x, y in data:
        x = x.to(device)
        y = y.to(device)
        optimizer.zero_grad()
        ypredicted = model(x)
        loss = criterion(torch.log(ypredicted), y)
        if step % 100 == 0:
            print(step, loss)
        step += 1
        loss.backward()
        optimizer.step()

    torch.save(model.state_dict(), 'model1.bin')
else:
    model.load_state_dict(torch.load('model1.bin')) 

vocab = bigram_data.vocab
prediction = 'the:0.03 be:0.03 to:0.03 of:0.025 and:0.025 a:0.025 in:0.020 that:0.020 have:0.015 I:0.010 it:0.010 for:0.010 not:0.010 on:0.010 with:0.010 he:0.010 as:0.010 you:0.010 do:0.010 at:0.010 :0.77'

def predict_word(w):
    ixs = torch.tensor(vocab.forward(w)).to(device)
    out = model(ixs)
    top = torch.topk(out[0], 8)
    top_indices = top.indices.tolist()
    top_probs = top.values.tolist()
    top_words = vocab.lookup_tokens(top_indices)
    pred_str = ""
    for word, prob in list(zip(top_words, top_probs)):
                pred_str += f"{word}:{prob} "
    return pred_str


def predict(f):
    x = pd.read_csv(f'{f}/in.tsv.xz', sep='\t', header=None, quoting=csv.QUOTE_NONE,  on_bad_lines='skip', encoding="UTF-8")[6]
    x = x.apply(data_preprocessing)

    with open(f'{f}/out.tsv', "w+", encoding="UTF-8") as f:
        for row in x:
            before = None
            for before in get_words_from_line(data_preprocessing(str(row)), False):
                pass
            before = [before]
            if(len(before) < 1):
                pred_str = prediction
            else:
                pred_str = predict_word(before)

            pred_str = pred_str.strip()
            f.write(pred_str + "\n")

predict("dev-0/")
predict("test-A/")