#!/usr/bin/env python
# coding=utf-8
# Copyright 2021 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.
"""
Fine-tuning the library models for translation.
"""
# You can also adapt this script on your own sequence to sequence task. Pointers for this are left as comments.

import logging
import os
import sys
from dataclasses import dataclass, field
from functools import partial
from typing import Optional

import datasets
import numpy as np
import tensorflow as tf
from datasets import load_dataset, load_metric
from tqdm import tqdm

import transformers
from transformers import (
    AutoConfig,
    AutoTokenizer,
    HfArgumentParser,
    M2M100Tokenizer,
    MBart50Tokenizer,
    MBart50TokenizerFast,
    MBartTokenizer,
    MBartTokenizerFast,
    TFAutoModelForSeq2SeqLM,
    TFTrainingArguments,
    create_optimizer,
    set_seed,
)
from transformers.trainer_utils import get_last_checkpoint
from transformers.utils import check_min_version
from transformers.utils.versions import require_version


# region Dependencies and constants
# Will error if the minimal version of Transformers is not installed. Remove at your own risks.
check_min_version("4.19.0.dev0")

require_version("datasets>=1.8.0", "To fix: pip install -r examples/pytorch/summarization/requirements.txt")

logger = logging.getLogger(__name__)
MULTILINGUAL_TOKENIZERS = [MBartTokenizer, MBartTokenizerFast, MBart50Tokenizer, MBart50TokenizerFast, M2M100Tokenizer]
# endregion


# region Arguments
@dataclass
class ModelArguments:
    """
    Arguments pertaining to which model/config/tokenizer we are going to fine-tune from.
    """

    model_name_or_path: str = field(
        metadata={"help": "Path to pretrained model or model identifier from huggingface.co/models"}
    )
    config_name: Optional[str] = field(
        default=None, metadata={"help": "Pretrained config name or path if not the same as model_name"}
    )
    tokenizer_name: Optional[str] = field(
        default=None, metadata={"help": "Pretrained tokenizer name or path if not the same as model_name"}
    )
    cache_dir: Optional[str] = field(
        default=None,
        metadata={"help": "Where to store the pretrained models downloaded from huggingface.co"},
    )
    use_fast_tokenizer: bool = field(
        default=True,
        metadata={"help": "Whether to use one of the fast tokenizer (backed by the tokenizers library) or not."},
    )
    model_revision: str = field(
        default="main",
        metadata={"help": "The specific model version to use (can be a branch name, tag name or commit id)."},
    )
    use_auth_token: bool = field(
        default=False,
        metadata={
            "help": "Will use the token generated when running `transformers-cli login` (necessary to use this script "
            "with private models)."
        },
    )


@dataclass
class DataTrainingArguments:
    """
    Arguments pertaining to what data we are going to input our model for training and eval.
    """

    source_lang: str = field(default=None, metadata={"help": "Source language id for translation."})
    target_lang: str = field(default=None, metadata={"help": "Target language id for translation."})
    dataset_name: Optional[str] = field(
        default=None, metadata={"help": "The name of the dataset to use (via the datasets library)."}
    )
    dataset_config_name: Optional[str] = field(
        default=None, metadata={"help": "The configuration name of the dataset to use (via the datasets library)."}
    )
    train_file: Optional[str] = field(
        default=None, metadata={"help": "The input training data file (a jsonlines or csv file)."}
    )
    validation_file: Optional[str] = field(
        default=None,
        metadata={
            "help": "An optional input evaluation data file to evaluate the metrics (rouge) on "
            "(a jsonlines or csv file)."
        },
    )
    test_file: Optional[str] = field(
        default=None,
        metadata={
            "help": "An optional input test data file to evaluate the metrics (rouge) on " "(a jsonlines or csv file)."
        },
    )
    overwrite_cache: bool = field(
        default=False, metadata={"help": "Overwrite the cached training and evaluation sets"}
    )
    preprocessing_num_workers: Optional[int] = field(
        default=None,
        metadata={"help": "The number of processes to use for the preprocessing."},
    )
    max_source_length: Optional[int] = field(
        default=1024,
        metadata={
            "help": "The maximum total input sequence length after tokenization. Sequences longer "
            "than this will be truncated, sequences shorter will be padded."
        },
    )
    max_target_length: Optional[int] = field(
        default=128,
        metadata={
            "help": "The maximum total sequence length for target text after tokenization. Sequences longer "
            "than this will be truncated, sequences shorter will be padded."
        },
    )
    val_max_target_length: Optional[int] = field(
        default=None,
        metadata={
            "help": "The maximum total sequence length for validation target text after tokenization. Sequences longer "
            "than this will be truncated, sequences shorter will be padded. Will default to `max_target_length`."
            "This argument is also used to override the ``max_length`` param of ``model.generate``, which is used "
            "during ``evaluate`` and ``predict``."
        },
    )
    pad_to_max_length: bool = field(
        default=False,
        metadata={
            "help": "Whether to pad all samples to model maximum sentence length. "
            "If False, will pad the samples dynamically when batching to the maximum length in the batch. More "
            "efficient on GPU but very bad for TPU."
        },
    )
    max_train_samples: Optional[int] = field(
        default=None,
        metadata={
            "help": "For debugging purposes or quicker training, truncate the number of training examples to this "
            "value if set."
        },
    )
    max_eval_samples: Optional[int] = field(
        default=None,
        metadata={
            "help": "For debugging purposes or quicker training, truncate the number of evaluation examples to this "
            "value if set."
        },
    )
    max_predict_samples: Optional[int] = field(
        default=None,
        metadata={
            "help": "For debugging purposes or quicker training, truncate the number of prediction examples to this "
            "value if set."
        },
    )
    num_beams: Optional[int] = field(
        default=None,
        metadata={
            "help": "Number of beams to use for evaluation. This argument will be passed to ``model.generate``, "
            "which is used during ``evaluate`` and ``predict``."
        },
    )
    ignore_pad_token_for_loss: bool = field(
        default=True,
        metadata={
            "help": "Whether to ignore the tokens corresponding to padded labels in the loss computation or not."
        },
    )
    source_prefix: Optional[str] = field(
        default=None, metadata={"help": "A prefix to add before every source text (useful for T5 models)."}
    )

    def __post_init__(self):
        if self.dataset_name is None and self.train_file is None and self.validation_file is None:
            raise ValueError("Need either a dataset name or a training/validation file.")
        else:
            if self.train_file is not None:
                extension = self.train_file.split(".")[-1]
                assert extension in ["csv", "json"], "`train_file` should be a csv or a json file."
            if self.validation_file is not None:
                extension = self.validation_file.split(".")[-1]
                assert extension in ["csv", "json"], "`validation_file` should be a csv or a json file."
        if self.val_max_target_length is None:
            self.val_max_target_length = self.max_target_length


# endregion

# region Data generator
def sample_generator(dataset, model, tokenizer, shuffle, pad_to_multiple_of=None):
    if shuffle:
        sample_ordering = np.random.permutation(len(dataset))
    else:
        sample_ordering = np.arange(len(dataset))
    for sample_idx in sample_ordering:
        example = dataset[int(sample_idx)]
        # Handle dicts with proper padding and conversion to tensor.
        example = tokenizer.pad(example, return_tensors="np", pad_to_multiple_of=pad_to_multiple_of)
        example = {key: tf.convert_to_tensor(arr, dtype_hint=tf.int32) for key, arr in example.items()}
        if model is not None and hasattr(model, "prepare_decoder_input_ids_from_labels"):
            decoder_input_ids = model.prepare_decoder_input_ids_from_labels(
                labels=tf.expand_dims(example["labels"], 0)
            )
            example["decoder_input_ids"] = tf.squeeze(decoder_input_ids, 0)
        yield example, example["labels"]  # TF needs some kind of labels, even if we don't use them
    return


# endregion


# region Helper functions
def dataset_to_tf(dataset, model, tokenizer, total_batch_size, num_epochs, shuffle):
    if dataset is None:
        return None
    train_generator = partial(sample_generator, dataset, model, tokenizer, shuffle=shuffle)
    train_signature = {
        feature: tf.TensorSpec(shape=(None,), dtype=tf.int32)
        for feature in dataset.features
        if feature != "special_tokens_mask"
    }
    if (
        model is not None
        and "decoder_input_ids" not in train_signature
        and hasattr(model, "prepare_decoder_input_ids_from_labels")
    ):
        train_signature["decoder_input_ids"] = train_signature["labels"]
    # This may need to be changed depending on your particular model or tokenizer!
    padding_values = {
        key: tf.convert_to_tensor(tokenizer.pad_token_id if tokenizer.pad_token_id is not None else 0, dtype=tf.int32)
        for key in train_signature.keys()
    }
    padding_values["labels"] = tf.convert_to_tensor(-100, dtype=tf.int32)
    train_signature["labels"] = train_signature["input_ids"]
    train_signature = (train_signature, train_signature["labels"])
    options = tf.data.Options()
    options.experimental_distribute.auto_shard_policy = tf.data.experimental.AutoShardPolicy.OFF
    tf_dataset = (
        tf.data.Dataset.from_generator(train_generator, output_signature=train_signature)
        .with_options(options)
        .padded_batch(
            batch_size=total_batch_size,
            drop_remainder=True,
            padding_values=(padding_values, np.array(-100, dtype=np.int32)),
        )
        .repeat(int(num_epochs))
    )
    return tf_dataset


# endregion


def main():
    # region Argument parsing
    # See all possible arguments in src/transformers/training_args.py
    # or by passing the --help flag to this script.
    # We now keep distinct sets of args, for a cleaner separation of concerns.

    parser = HfArgumentParser((ModelArguments, DataTrainingArguments, TFTrainingArguments))
    if len(sys.argv) == 2 and sys.argv[1].endswith(".json"):
        # If we pass only one argument to the script and it's the path to a json file,
        # let's parse it to get our arguments.
        model_args, data_args, training_args = parser.parse_json_file(json_file=os.path.abspath(sys.argv[1]))
    else:
        model_args, data_args, training_args = parser.parse_args_into_dataclasses()
    # endregion

    # region Logging
    logging.basicConfig(
        format="%(asctime)s - %(levelname)s - %(name)s - %(message)s",
        datefmt="%m/%d/%Y %H:%M:%S",
        handlers=[logging.StreamHandler(sys.stdout)],
    )
    logger.setLevel(logging.INFO)
    datasets.utils.logging.set_verbosity(logging.INFO)
    transformers.utils.logging.set_verbosity(logging.INFO)

    # Log on each process the small summary:
    logger.info(f"Training/evaluation parameters {training_args}")
    # endregion

    # region Detecting last checkpoint
    last_checkpoint = None
    if os.path.isdir(training_args.output_dir) and training_args.do_train and not training_args.overwrite_output_dir:
        last_checkpoint = get_last_checkpoint(training_args.output_dir)
        if last_checkpoint is None and len(os.listdir(training_args.output_dir)) > 0:
            raise ValueError(
                f"Output directory ({training_args.output_dir}) already exists and is not empty. "
                "Use --overwrite_output_dir to overcome."
            )
        elif last_checkpoint is not None and training_args.resume_from_checkpoint is None:
            logger.info(
                f"Checkpoint detected, resuming training at {last_checkpoint}. To avoid this behavior, change "
                "the `--output_dir` or add `--overwrite_output_dir` to train from scratch."
            )
    # endregion

    # Set seed before initializing model.
    set_seed(training_args.seed)

    # region Load datasets
    # Get the datasets: you can either provide your own CSV/JSON training and evaluation files (see below)
    # or just provide the name of one of the public datasets available on the hub at https://huggingface.co/datasets/
    # (the dataset will be downloaded automatically from the datasets Hub).
    #
    # For CSV/JSON files this script will use the first column for the full texts and the second column for the
    # summaries (unless you specify column names for this with the `text_column` and `summary_column` arguments).
    #
    # In distributed training, the load_dataset function guarantee that only one local process can concurrently
    # download the dataset.
    if data_args.dataset_name is not None:
        # Downloading and loading a dataset from the hub.
        raw_datasets = load_dataset(
            data_args.dataset_name,
            data_args.dataset_config_name,
            cache_dir=model_args.cache_dir,
            use_auth_token=True if model_args.use_auth_token else None,
        )
    else:
        data_files = {}
        if data_args.train_file is not None:
            data_files["train"] = data_args.train_file
            extension = data_args.train_file.split(".")[-1]
        if data_args.validation_file is not None:
            data_files["validation"] = data_args.validation_file
            extension = data_args.validation_file.split(".")[-1]
        raw_datasets = load_dataset(
            extension,
            data_files=data_files,
            cache_dir=model_args.cache_dir,
            use_auth_token=True if model_args.use_auth_token else None,
        )
    # See more about loading any type of standard or custom dataset (from files, python dict, pandas DataFrame, etc) at
    # https://huggingface.co/docs/datasets/loading_datasets.html.
    # endregion

    # region Load model config and tokenizer
    #
    # Distributed training:
    # The .from_pretrained methods guarantee that only one local process can concurrently
    # download model & vocab.

    config = AutoConfig.from_pretrained(
        model_args.config_name if model_args.config_name else model_args.model_name_or_path,
        cache_dir=model_args.cache_dir,
        revision=model_args.model_revision,
        use_auth_token=True if model_args.use_auth_token else None,
    )
    tokenizer = AutoTokenizer.from_pretrained(
        model_args.tokenizer_name if model_args.tokenizer_name else model_args.model_name_or_path,
        cache_dir=model_args.cache_dir,
        use_fast=model_args.use_fast_tokenizer,
        revision=model_args.model_revision,
        use_auth_token=True if model_args.use_auth_token else None,
    )

    prefix = data_args.source_prefix if data_args.source_prefix is not None else ""
    # endregion

    # region Dataset preprocessing
    # We need to tokenize inputs and targets.
    if training_args.do_train:
        column_names = raw_datasets["train"].column_names
    elif training_args.do_eval:
        column_names = raw_datasets["validation"].column_names
    else:
        logger.info("There is nothing to do. Please pass `do_train`, and/or `do_eval`.")
        return

    column_names = raw_datasets["train"].column_names

    # For translation we set the codes of our source and target languages (only useful for mBART, the others will
    # ignore those attributes).
    if isinstance(tokenizer, tuple(MULTILINGUAL_TOKENIZERS)):
        assert data_args.target_lang is not None and data_args.source_lang is not None, (
            f"{tokenizer.__class__.__name__} is a multilingual tokenizer which requires --source_lang and "
            "--target_lang arguments."
        )
        tokenizer.src_lang = data_args.source_lang
        tokenizer.tgt_lang = data_args.target_lang
        forced_bos_token_id = (
            tokenizer.lang_code_to_id[data_args.forced_bos_token] if data_args.forced_bos_token is not None else None
        )

    # Get the language codes for input/target.
    source_lang = data_args.source_lang.split("_")[0]
    target_lang = data_args.target_lang.split("_")[0]

    padding = "max_length" if data_args.pad_to_max_length else False

    # Temporarily set max_target_length for training.
    max_target_length = data_args.max_target_length
    padding = "max_length" if data_args.pad_to_max_length else False

    def preprocess_function(examples):
        inputs = [ex[source_lang] for ex in examples["translation"]]
        targets = [ex[target_lang] for ex in examples["translation"]]
        inputs = [prefix + inp for inp in inputs]
        model_inputs = tokenizer(inputs, max_length=data_args.max_source_length, padding=padding, truncation=True)

        # Setup the tokenizer for targets
        with tokenizer.as_target_tokenizer():
            labels = tokenizer(targets, max_length=max_target_length, padding=padding, truncation=True)

        # If we are padding here, replace all tokenizer.pad_token_id in the labels by -100 when we want to ignore
        # padding in the loss.
        if padding == "max_length" and data_args.ignore_pad_token_for_loss:
            labels["input_ids"] = [
                [(l if l != tokenizer.pad_token_id else -100) for l in label] for label in labels["input_ids"]
            ]

        model_inputs["labels"] = labels["input_ids"]
        return model_inputs

    if training_args.do_train:
        if "train" not in raw_datasets:
            raise ValueError("--do_train requires a train dataset")
        train_dataset = raw_datasets["train"]
        if data_args.max_train_samples is not None:
            max_train_samples = min(len(train_dataset), data_args.max_train_samples)
            train_dataset = train_dataset.select(range(max_train_samples))
        with training_args.main_process_first(desc="train dataset map pre-processing"):
            train_dataset = train_dataset.map(
                preprocess_function,
                batched=True,
                num_proc=data_args.preprocessing_num_workers,
                remove_columns=column_names,
                load_from_cache_file=not data_args.overwrite_cache,
                desc="Running tokenizer on train dataset",
            )
    else:
        train_dataset = None

    if training_args.do_eval:
        max_target_length = data_args.val_max_target_length
        if "validation" not in raw_datasets:
            raise ValueError("--do_eval requires a validation dataset")
        eval_dataset = raw_datasets["validation"]
        if data_args.max_eval_samples is not None:
            max_eval_samples = min(len(eval_dataset), data_args.max_eval_samples)
            eval_dataset = eval_dataset.select(range(max_eval_samples))
        with training_args.main_process_first(desc="validation dataset map pre-processing"):
            eval_dataset = eval_dataset.map(
                preprocess_function,
                batched=True,
                num_proc=data_args.preprocessing_num_workers,
                remove_columns=column_names,
                load_from_cache_file=not data_args.overwrite_cache,
                desc="Running tokenizer on validation dataset",
            )
    else:
        eval_dataset = None
    # endregion

    with training_args.strategy.scope():
        # region Prepare model
        model = TFAutoModelForSeq2SeqLM.from_pretrained(
            model_args.model_name_or_path,
            config=config,
            cache_dir=model_args.cache_dir,
            revision=model_args.model_revision,
            use_auth_token=True if model_args.use_auth_token else None,
        )

        model.resize_token_embeddings(len(tokenizer))
        if isinstance(tokenizer, tuple(MULTILINGUAL_TOKENIZERS)):
            model.config.forced_bos_token_id = forced_bos_token_id
        # endregion

        # region Set decoder_start_token_id
        if model.config.decoder_start_token_id is None and isinstance(tokenizer, (MBartTokenizer, MBartTokenizerFast)):
            assert (
                data_args.target_lang is not None and data_args.source_lang is not None
            ), "mBart requires --target_lang and --source_lang"
            if isinstance(tokenizer, MBartTokenizer):
                model.config.decoder_start_token_id = tokenizer.lang_code_to_id[data_args.target_lang]
            else:
                model.config.decoder_start_token_id = tokenizer.convert_tokens_to_ids(data_args.target_lang)

        if model.config.decoder_start_token_id is None:
            raise ValueError("Make sure that `config.decoder_start_token_id` is correctly defined")
        # endregion

        # region Prepare TF Dataset objects
        num_replicas = training_args.strategy.num_replicas_in_sync
        total_train_batch_size = training_args.per_device_train_batch_size * num_replicas
        total_eval_batch_size = training_args.per_device_eval_batch_size * num_replicas
        tf_train_dataset = dataset_to_tf(
            train_dataset,
            model,
            tokenizer,
            total_batch_size=total_train_batch_size,
            num_epochs=training_args.num_train_epochs,
            shuffle=True,
        )
        tf_eval_dataset = dataset_to_tf(
            eval_dataset,
            model,
            tokenizer,
            total_eval_batch_size,
            num_epochs=1,
            shuffle=False,
        )
        # endregion

        # region Optimizer, loss and LR scheduling
        # Scheduler and math around the number of training steps.
        num_update_steps_per_epoch = len(train_dataset) // training_args.per_device_train_batch_size
        num_train_steps = training_args.num_train_epochs * num_update_steps_per_epoch
        optimizer, lr_schedule = create_optimizer(
            init_lr=training_args.learning_rate,
            num_train_steps=num_train_steps,
            num_warmup_steps=training_args.warmup_steps,
        )

        def masked_sparse_categorical_crossentropy(y_true, y_pred):
            # We clip the negative labels to 0 to avoid NaNs appearing in the output and
            # fouling up everything that comes afterwards. The loss values corresponding to clipped values
            # will be masked later anyway, but even masked NaNs seem to cause overflows for some reason.
            # 1e6 is chosen as a reasonable upper bound for the number of token indices - in the unlikely
            # event that you have more than 1 million tokens in your vocabulary, consider increasing this value.
            # More pragmatically, consider redesigning your tokenizer.
            losses = tf.keras.losses.sparse_categorical_crossentropy(
                tf.clip_by_value(y_true, 0, int(1e6)), y_pred, from_logits=True
            )
            # Compute the per-sample loss only over the unmasked tokens
            losses = tf.ragged.boolean_mask(losses, y_true != -100)
            losses = tf.reduce_mean(losses, axis=-1)
            return losses

        # endregion

        # region Metric and postprocessing
        metric = load_metric("sacrebleu")

        def postprocess_text(preds, labels):
            preds = [pred.strip() for pred in preds]
            labels = [[label.strip()] for label in labels]

            return preds, labels

        # endregion

        # region Training
        model.compile(loss={"logits": masked_sparse_categorical_crossentropy}, optimizer=optimizer)

        if training_args.do_train:
            logger.info("***** Running training *****")
            logger.info(f"  Num examples = {len(train_dataset)}")
            logger.info(f"  Num Epochs = {training_args.num_train_epochs}")
            logger.info(f"  Instantaneous batch size per device = {training_args.per_device_train_batch_size}")
            logger.info(f"  Total train batch size = {total_train_batch_size}")
            logger.info(f"  Total optimization steps = {num_train_steps}")

            model.fit(
                tf_train_dataset,
                epochs=int(training_args.num_train_epochs),
                steps_per_epoch=num_update_steps_per_epoch,
            )
        # endregion

        # region Validation
        if data_args.val_max_target_length is None:
            data_args.val_max_target_length = data_args.max_target_length

        gen_kwargs = {
            "max_length": data_args.val_max_target_length,
            "num_beams": data_args.num_beams,
        }
        if training_args.do_eval:
            logger.info("Evaluation...")
            for batch, labels in tqdm(
                tf_eval_dataset, total=len(eval_dataset) // training_args.per_device_eval_batch_size
            ):
                batch.update(gen_kwargs)
                generated_tokens = model.generate(**batch)
                if isinstance(generated_tokens, tuple):
                    generated_tokens = generated_tokens[0]
                decoded_preds = tokenizer.batch_decode(generated_tokens, skip_special_tokens=True)
                labels = np.where(labels != -100, labels, tokenizer.pad_token_id)
                decoded_labels = tokenizer.batch_decode(labels, skip_special_tokens=True)
                decoded_preds, decoded_labels = postprocess_text(decoded_preds, decoded_labels)

                metric.add_batch(predictions=decoded_preds, references=decoded_labels)
            eval_metric = metric.compute()
            logger.info({"bleu": eval_metric["score"]})
        # endregion

        if training_args.output_dir is not None:
            model.save_pretrained(training_args.output_dir)


if __name__ == "__main__":
    main()
