"""
This examples trains BERT (or any other transformer model like RoBERTa, DistilBERT etc.) for the STSbenchmark from scratch. It generates sentence embeddings
that can be compared using cosine-similarity to measure the similarity.
"""

import math
import sys
import os
import gzip
import csv
import logging
import argparse

from datetime import datetime
from torch.utils.data import DataLoader
from sentence_transformers import SentenceTransformer,  SentencesDataset, LoggingHandler, losses, models, util
from sentence_transformers.evaluation import EmbeddingSimilarityEvaluator
from sentence_transformers.readers import STSBenchmarkDataReader, InputExample

#### Just some code to print debug information to stdout
logging.basicConfig(format='%(asctime)s - %(message)s',
                    datefmt='%Y-%m-%d %H:%M:%S',
                    level=logging.INFO,
                    handlers=[LoggingHandler()])

#### params
parser = argparse.ArgumentParser()
parser.add_argument('--data_path', type=str, default='datasets/stsbenchmark.tsv.gz', help='Input txt path')
parser.add_argument('--train_batch_size', type=int, default=16)
parser.add_argument('--num_epochs', type=int, default=10)
parser.add_argument('--model_name_or_path', type=str, default="bert-base-uncased")
parser.add_argument('--save_root_path', type=str, default="output", help='Model output folder')
parser.add_argument('--lr', default=2e-05)
args = parser.parse_args()

# Check if dataset exsist. If not, download and extract  it
sts_dataset_path = args.data_path

if not os.path.exists(sts_dataset_path):
    util.http_get('https://public.ukp.informatik.tu-darmstadt.de/reimers/sentence-transformers/datasets/stsbenchmark.tsv.gz', sts_dataset_path)

#You can specify any huggingface/transformers pre-trained model here, for example, bert-base-uncased, roberta-base, xlm-roberta-base
model_name = args.model_name_or_path

# Read the dataset
train_batch_size = args.train_batch_size
num_epochs = args.num_epochs
model_save_path = args.save_root_path + "/training_stsbenchmark_" + model_name.replace("/", "-") + '-'+datetime.now().strftime("%Y-%m-%d_%H-%M-%S")

# Use Huggingface/transformers model (like BERT, RoBERTa, XLNet, XLM-R) for mapping tokens to embeddings
word_embedding_model = models.Transformer(model_name)

# Apply mean pooling to get one fixed sized sentence vector
pooling_model = models.Pooling(word_embedding_model.get_word_embedding_dimension(),
                               pooling_mode_mean_tokens=True,
                               pooling_mode_cls_token=False,
                               pooling_mode_max_tokens=False)

model = SentenceTransformer(modules=[word_embedding_model, pooling_model])

# Convert the dataset to a DataLoader ready for training
logging.info("Read STSbenchmark train dataset")

train_samples = []
dev_samples = []
test_samples = []
with gzip.open(sts_dataset_path, 'rt', encoding='utf8') as fIn:
    reader = csv.DictReader(fIn, delimiter='\t', quoting=csv.QUOTE_NONE)
    for row in reader:
        score = float(row['score']) / 5.0  # Normalize score to range 0 ... 1
        inp_example = InputExample(texts=[row['sentence1'], row['sentence2']], label=score)
        if row['split'] == 'dev':
            dev_samples.append(inp_example)
        elif row['split'] == 'test':
            test_samples.append(inp_example)
        else:
            train_samples.append(inp_example)

train_dataset = SentencesDataset(train_samples, model)
train_dataloader = DataLoader(train_dataset, shuffle=True, batch_size=train_batch_size)
train_loss = losses.CosineSimilarityLoss(model=model)

logging.info("Read STSbenchmark dev dataset")
evaluator = EmbeddingSimilarityEvaluator.from_input_examples(dev_samples, name='sts-dev')

# Configure the training. We skip evaluation in this example
warmup_steps = math.ceil(len(train_dataset) * num_epochs / train_batch_size * 0.1) #10% of train data for warm-up
logging.info("Warmup-steps: {}".format(warmup_steps))

# Train the model
model.fit(train_objectives=[(train_dataloader, train_loss)],
          evaluator=evaluator,
          epochs=num_epochs,
          evaluation_steps=1000,
          warmup_steps=warmup_steps,
          output_path=model_save_path)

##############################################################################
#
# Load the stored model and evaluate its performance on STS benchmark dataset
#
##############################################################################

model = SentenceTransformer(model_save_path)
test_evaluator = EmbeddingSimilarityEvaluator.from_input_examples(test_samples, name='sts-test')
test_evaluator(model, output_path=model_save_path)