# coding=utf-8
# Copyright 2018 Google AI, Google Brain and Carnegie Mellon University Authors and the HugginFace Inc. team.
# Copyright (c) 2018, NVIDIA CORPORATION.  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.
""" OpenAI GPT model fine-tuning script.
    Adapted from https://github.com/huggingface/pytorch-openai-transformer-lm/blob/master/train.py
    It self adapted from https://github.com/openai/finetune-transformer-lm/blob/master/train.py

    This script with default values fine-tunes and evaluate a pretrained OpenAI GPT on the RocStories dataset:
        python run_openai_gpt.py \
          --model_name openai-gpt \
          --do_train \
          --do_eval \
          --train_dataset $ROC_STORIES_DIR/cloze_test_val__spring2016\ -\ cloze_test_ALL_val.csv \
          --eval_dataset $ROC_STORIES_DIR/cloze_test_test__spring2016\ -\ cloze_test_ALL_test.csv \
          --output_dir ../log \
          --train_batch_size 16 \
"""
import argparse
import os
import csv
import random
import logging
from tqdm import tqdm, trange

import numpy as np
import torch
from torch.utils.data import (DataLoader, RandomSampler, SequentialSampler,
                              TensorDataset)

from pytorch_pretrained_bert import OpenAIGPTDoubleHeadsModel, OpenAIGPTTokenizer, OpenAIAdam, cached_path

ROCSTORIES_URL = "https://s3.amazonaws.com/datasets.huggingface.co/ROCStories.tar.gz"

logging.basicConfig(format = '%(asctime)s - %(levelname)s - %(name)s -   %(message)s',
                    datefmt = '%m/%d/%Y %H:%M:%S',
                    level = logging.INFO)
logger = logging.getLogger(__name__)

def accuracy(out, labels):
    outputs = np.argmax(out, axis=1)
    return np.sum(outputs == labels)

def load_rocstories_dataset(dataset_path):
    """ Output a list of tuples(story, 1st continuation, 2nd continuation, label) """
    with open(dataset_path, encoding='utf_8') as f:
        f = csv.reader(f)
        output = []
        next(f) # skip the first line
        for line in tqdm(f):
            output.append((' '.join(line[1:5]), line[5], line[6], int(line[-1])-1))
    return output

def pre_process_datasets(encoded_datasets, input_len, cap_length, start_token, delimiter_token, clf_token):
    """ Pre-process datasets containing lists of tuples(story, 1st continuation, 2nd continuation, label)

        To Transformer inputs of shape (n_batch, n_alternative, length) comprising for each batch, continuation:
        input_ids[batch, alternative, :] = [start_token] + story[:cap_length] + [delimiter_token] + cont1[:cap_length] + [clf_token]
    """
    tensor_datasets = []
    for dataset in encoded_datasets:
        n_batch = len(dataset)
        input_ids = np.zeros((n_batch, 2, input_len), dtype=np.int64)
        mc_token_ids = np.zeros((n_batch, 2), dtype=np.int64)
        lm_labels = np.full((n_batch, 2, input_len), fill_value=-1, dtype=np.int64)
        mc_labels = np.zeros((n_batch,), dtype=np.int64)
        for i, (story, cont1, cont2, mc_label), in enumerate(dataset):
            with_cont1 = [start_token] + story[:cap_length] + [delimiter_token] + cont1[:cap_length] + [clf_token]
            with_cont2 = [start_token] + story[:cap_length] + [delimiter_token] + cont2[:cap_length] + [clf_token]
            input_ids[i, 0, :len(with_cont1)] = with_cont1
            input_ids[i, 1, :len(with_cont2)] = with_cont2
            mc_token_ids[i, 0] = len(with_cont1) - 1
            mc_token_ids[i, 1] = len(with_cont2) - 1
            lm_labels[i, 0, :len(with_cont1)-1] = with_cont1[1:]
            lm_labels[i, 1, :len(with_cont2)-1] = with_cont2[1:]
            mc_labels[i] = mc_label
        all_inputs = (input_ids, mc_token_ids, lm_labels, mc_labels)
        tensor_datasets.append(tuple(torch.tensor(t) for t in all_inputs))
    return tensor_datasets

def main():
    parser = argparse.ArgumentParser()
    parser.add_argument('--model_name', type=str, default='openai-gpt',
                        help='pretrained model name')
    parser.add_argument("--do_train", action='store_true', help="Whether to run training.")
    parser.add_argument("--do_eval", action='store_true', help="Whether to run eval on the dev set.")
    parser.add_argument("--output_dir", default=None, type=str, required=True,
                        help="The output directory where the model predictions and checkpoints will be written.")
    parser.add_argument('--train_dataset', type=str, default='')
    parser.add_argument('--eval_dataset', type=str, default='')
    parser.add_argument('--seed', type=int, default=42)
    parser.add_argument('--num_train_epochs', type=int, default=3)
    parser.add_argument('--train_batch_size', type=int, default=8)
    parser.add_argument('--eval_batch_size', type=int, default=16)
    parser.add_argument('--max_grad_norm', type=int, default=1)
    parser.add_argument('--learning_rate', type=float, default=6.25e-5)
    parser.add_argument('--warmup_proportion', type=float, default=0.002)
    parser.add_argument('--lr_schedule', type=str, default='warmup_linear')
    parser.add_argument('--weight_decay', type=float, default=0.01)
    parser.add_argument('--lm_coef', type=float, default=0.9)
    parser.add_argument('--n_valid', type=int, default=374)

    parser.add_argument('--server_ip', type=str, default='', help="Can be used for distant debugging.")
    parser.add_argument('--server_port', type=str, default='', help="Can be used for distant debugging.")
    args = parser.parse_args()
    print(args)

    if args.server_ip and args.server_port:
        # Distant debugging - see https://code.visualstudio.com/docs/python/debugging#_attach-to-a-local-script
        import ptvsd
        print("Waiting for debugger attach")
        ptvsd.enable_attach(address=(args.server_ip, args.server_port), redirect_output=True)
        ptvsd.wait_for_attach()

    random.seed(args.seed)
    np.random.seed(args.seed)
    torch.manual_seed(args.seed)
    torch.cuda.manual_seed_all(args.seed)

    device = torch.device("cuda" if torch.cuda.is_available() else "cpu")
    n_gpu = torch.cuda.device_count()
    logger.info("device: {}, n_gpu {}".format(device, n_gpu))

    if not args.do_train and not args.do_eval:
        raise ValueError("At least one of `do_train` or `do_eval` must be True.")

    if not os.path.exists(args.output_dir):
        os.makedirs(args.output_dir)

    # Load tokenizer and model
    # This loading functions also add new tokens and embeddings called `special tokens`
    # These new embeddings will be fine-tuned on the RocStories dataset
    special_tokens = ['_start_', '_delimiter_', '_classify_']
    tokenizer = OpenAIGPTTokenizer.from_pretrained(args.model_name, special_tokens=special_tokens)
    special_tokens_ids = list(tokenizer.convert_tokens_to_ids(token) for token in special_tokens)
    model = OpenAIGPTDoubleHeadsModel.from_pretrained(args.model_name, num_special_tokens=len(special_tokens))
    model.to(device)

    # Load and encode the datasets
    if not args.train_dataset and not args.eval_dataset:
        roc_stories = cached_path(ROCSTORIES_URL)
    def tokenize_and_encode(obj):
        """ Tokenize and encode a nested object """
        if isinstance(obj, str):
            return tokenizer.convert_tokens_to_ids(tokenizer.tokenize(obj))
        elif isinstance(obj, int):
            return obj
        return list(tokenize_and_encode(o) for o in obj)
    logger.info("Encoding dataset...")
    train_dataset = load_rocstories_dataset(args.train_dataset)
    eval_dataset = load_rocstories_dataset(args.eval_dataset)
    datasets = (train_dataset, eval_dataset)
    encoded_datasets = tokenize_and_encode(datasets)

    # Compute the max input length for the Transformer
    max_length = model.config.n_positions // 2 - 2
    input_length = max(len(story[:max_length]) + max(len(cont1[:max_length]), len(cont2[:max_length])) + 3  \
                           for dataset in encoded_datasets for story, cont1, cont2, _ in dataset)
    input_length = min(input_length, model.config.n_positions)  # Max size of input for the pre-trained model

    # Prepare inputs tensors and dataloaders
    tensor_datasets = pre_process_datasets(encoded_datasets, input_length, max_length, *special_tokens_ids)
    train_tensor_dataset, eval_tensor_dataset = tensor_datasets[0], tensor_datasets[1]

    train_data = TensorDataset(*train_tensor_dataset)
    train_sampler = RandomSampler(train_data)
    train_dataloader = DataLoader(train_data, sampler=train_sampler, batch_size=args.train_batch_size)

    eval_data = TensorDataset(*eval_tensor_dataset)
    eval_sampler = SequentialSampler(eval_data)
    eval_dataloader = DataLoader(eval_data, sampler=eval_sampler, batch_size=args.eval_batch_size)

    # Prepare optimizer
    param_optimizer = list(model.named_parameters())
    no_decay = ['bias', 'LayerNorm.bias', 'LayerNorm.weight']
    optimizer_grouped_parameters = [
        {'params': [p for n, p in param_optimizer if not any(nd in n for nd in no_decay)], 'weight_decay': 0.01},
        {'params': [p for n, p in param_optimizer if any(nd in n for nd in no_decay)], 'weight_decay': 0.0}
        ]
    num_train_optimization_steps = len(train_data) * args.num_train_epochs // args.train_batch_size
    optimizer = OpenAIAdam(optimizer_grouped_parameters,
                           lr=args.learning_rate,
                           warmup=args.warmup_proportion,
                           max_grad_norm=args.max_grad_norm,
                           weight_decay=args.weight_decay,
                           t_total=num_train_optimization_steps)

    if args.do_train:
        nb_tr_steps, tr_loss, exp_average_loss = 0, 0, None
        model.train()
        for _ in trange(int(args.num_train_epochs), desc="Epoch"):
            tr_loss = 0
            nb_tr_steps = 0
            tqdm_bar = tqdm(train_dataloader, desc="Training")
            for step, batch in enumerate(tqdm_bar):
                batch = tuple(t.to(device) for t in batch)
                input_ids, mc_token_ids, lm_labels, mc_labels = batch
                losses = model(input_ids, mc_token_ids, lm_labels, mc_labels)
                loss = args.lm_coef * losses[0] + losses[1]
                loss.backward()
                optimizer.step()
                tr_loss += loss.item()
                exp_average_loss = loss.item() if exp_average_loss is None else 0.7*exp_average_loss+0.3*loss.item()
                nb_tr_steps += 1
                tqdm_bar.desc = "Training loss: {:.2e} lr: {:.2e}".format(exp_average_loss, optimizer.get_lr()[0])

    # Save a trained model
    if args.do_train:
        model_to_save = model.module if hasattr(model, 'module') else model  # Only save the model it-self
        output_model_file = os.path.join(args.output_dir, "pytorch_model.bin")
        config = model.config
        torch.save(model_to_save.state_dict(), output_model_file)

        # Load a trained model that you have fine-tuned
        model_state_dict = torch.load(output_model_file)
        model = OpenAIGPTDoubleHeadsModel(config)
        model.load_state_dict(model_state_dict)
        model.to(device)

    if args.do_eval:
        model.eval()
        eval_loss, eval_accuracy = 0, 0
        nb_eval_steps, nb_eval_examples = 0, 0
        for batch in tqdm(eval_dataloader, desc="Evaluating"):
            batch = tuple(t.to(device) for t in batch)
            input_ids, mc_token_ids, lm_labels, mc_labels = batch
            with torch.no_grad():
                _, mc_loss = model(input_ids, mc_token_ids, lm_labels, mc_labels)
                _, mc_logits = model(input_ids, mc_token_ids)

            mc_logits = mc_logits.detach().cpu().numpy()
            mc_labels = mc_labels.to('cpu').numpy()
            tmp_eval_accuracy = accuracy(mc_logits, mc_labels)

            eval_loss += mc_loss.mean().item()
            eval_accuracy += tmp_eval_accuracy

            nb_eval_examples += input_ids.size(0)
            nb_eval_steps += 1

        eval_loss = eval_loss / nb_eval_steps
        eval_accuracy = eval_accuracy / nb_eval_examples
        train_loss = tr_loss/nb_tr_steps if args.do_train else None
        result = {'eval_loss': eval_loss,
                  'eval_accuracy': eval_accuracy,
                  'train_loss': train_loss}

        output_eval_file = os.path.join(args.output_dir, "eval_results.txt")
        with open(output_eval_file, "w") as writer:
            logger.info("***** Eval results *****")
            for key in sorted(result.keys()):
                logger.info("  %s = %s", key, str(result[key]))
                writer.write("%s = %s\n" % (key, str(result[key])))

if __name__ == '__main__':
    main()
