import logging
import os
from pathlib import Path
from time import sleep
from typing import Callable, List, Optional, Union

import numpy as np
import tensorflow as tf
from packaging.version import parse
from tensorflow.keras.callbacks import Callback

from huggingface_hub import Repository

from . import IntervalStrategy, PreTrainedTokenizerBase
from .file_utils import get_full_repo_name
from .modelcard import TrainingSummary


logger = logging.getLogger(__name__)


class KerasMetricCallback(Callback):
    """
    Callback to compute metrics at the end of every epoch. Unlike normal Keras metrics, these do not need to be
    compilable by TF. It is particularly useful for common NLP metrics like BLEU and ROUGE that require string
    operations or generation loops that cannot be compiled. Predictions (or generations) will be computed on the
    `eval_dataset` before being passed to the `metric_fn` in `np.ndarray` format. The `metric_fn` should compute
    metrics and return a dict mapping metric names to metric values.

    We provide an example of a suitable metric_fn that computes ROUGE scores for a summarization model below. Note that
    this example skips some post-processing for readability and simplicity, and should probably not be used as-is!

    ```py
    from datasets import load_metric

    rouge_metric = load_metric("rouge")


    def rouge_fn(predictions, labels):
        decoded_predictions = tokenizer.batch_decode(predictions, skip_special_tokens=True)
        decoded_labels = tokenizer.batch_decode(labels, skip_special_tokens=True)
        result = rouge_metric.compute(predictions=decoded_predictions, references=decoded_labels)
        return {key: value.mid.fmeasure * 100 for key, value in result.items()}
    ```

    The above function will return a dict containing values which will be logged like any other Keras metric:

    ```
    {'rouge1': 37.4199, 'rouge2': 13.9768, 'rougeL': 34.361, 'rougeLsum': 35.0781
    ```

    Args:
        metric_fn (`Callable`):
            Metric function provided by the user. It will be called with two arguments - `predictions` and `labels`.
            These contain the model's outputs and matching labels from the dataset. It should return a dict mapping
            metric names to numerical values.
        eval_dataset (`tf.data.Dataset` or `dict` or `tuple` or `np.ndarray` or `tf.Tensor`):
            Validation data to be used to generate predictions for the `metric_fn`.
        metric_fn_kwargs (`dict`, *optional*):
            Additional keyword arguments to be passed to the metric_fn.
        output_cols (`List[str], *optional*):
            A list of columns to be retained from the model output as the predictions. Defaults to all.
        label_cols ('`List[str]`, *optional*'):
            A list of columns to be retained from the input dataset as the labels. Will be autodetected if this is not
            supplied.
        batch_size (`int`, *optional*):
            Batch size. Only used when the data is not a pre-batched `tf.data.Dataset`.
        predict_with_generate: (`bool`, *optional*, defaults to `False`):
            Whether we should use `model.generate()` to get outputs for the model.

    """

    def __init__(
        self,
        metric_fn: Callable,
        eval_dataset: Union[tf.data.Dataset, np.ndarray, tf.Tensor, tuple, dict],
        metric_fn_kwargs: Optional[dict] = None,
        output_cols: Optional[List[str]] = None,
        label_cols: Optional[List[str]] = None,
        batch_size: Optional[int] = None,
        predict_with_generate: Optional[bool] = False,
    ):
        super().__init__()
        self.metric_fn = metric_fn
        self.batch_size = batch_size
        if not isinstance(eval_dataset, tf.data.Dataset):
            if batch_size is None:
                raise ValueError(
                    "When passing data to KerasMetricCallback that is not a pre-batched tf.data.Dataset "
                    "the batch_size argument must be set."
                )
            # Wrap a tf.data.Dataset around it
            eval_dataset = tf.data.Dataset.from_tensor_slices(eval_dataset).batch(batch_size, drop_remainder=False)
        self.eval_dataset = eval_dataset
        self.predict_with_generate = predict_with_generate
        self.output_cols = output_cols
        self.metric_fn_kwargs = metric_fn_kwargs or dict()

        if hasattr(self.model, "encoder") and self.model.encoder.main_input_name != self.model.main_input_name:
            self.main_input_name = self.model.encoder.main_input_name
        else:
            self.main_input_name = self.model.main_input_name

        # This next block attempts to parse out which elements of the dataset should be appended to the labels list
        # that is passed to the metric_fn
        if isinstance(eval_dataset.element_spec, tuple) and len(eval_dataset.element_spec) == 2:
            input_spec, label_spec = eval_dataset.element_spec
        else:
            input_spec = eval_dataset.element_spec
            label_spec = None
        if label_cols is not None:
            for label in label_cols:
                if label not in input_spec:
                    raise ValueError(f"Label {label} is in label_cols but could not be found in the dataset inputs!")
            self.label_cols = label_cols
            self.use_keras_label = False
        elif label_spec is not None:
            # If the dataset inputs are split into a 2-tuple of inputs and labels,
            # assume the second element is the labels
            self.label_cols = None
            self.use_keras_label = True
        elif "labels" in input_spec:
            self.label_cols = ["labels"]
            self.use_keras_label = False
            logging.warning("No label_cols specified for KerasMetricCallback, assuming you want the 'labels' key.")
        else:
            raise ValueError("Could not autodetect label_cols for KerasMetricCallback, please specify them!")
        if parse(tf.__version__).minor < parse("2.7"):
            logging.warning("TF versions less than 2.7 may encounter issues with KerasMetricCallback!")

    @staticmethod
    def _concatenate_batches(batches):
        # Flattens Numpy array batches into a list of single samples, where each sample is still np.ndarray
        return [sample for batch in batches for sample in batch]

    def _postprocess_predictions_or_labels(self, inputs):
        if isinstance(inputs[0], dict):
            outputs = dict()
            for key in inputs[0].keys():
                outputs[key] = self._concatenate_batches(batch[key] for batch in inputs)
        elif isinstance(inputs[0], list) or isinstance(inputs[0], tuple):
            outputs = []
            for input_list in zip(*inputs):
                outputs.append(self._concatenate_batches(input_list))
        elif isinstance(inputs[0], np.ndarray):
            outputs = self._concatenate_batches(inputs)
        else:
            raise TypeError(f"Couldn't handle batch of type {type(inputs[0])}!")
        return outputs

    def on_epoch_end(self, epoch, logs=None):
        prediction_list = []
        label_list = []

        # The whole predict/generate loop is handled inside this method
        for batch in self.eval_dataset:
            if isinstance(batch, tuple):
                batch, labels = batch
            else:
                labels = None
            if self.predict_with_generate:
                if isinstance(batch, dict):
                    generation_inputs = batch[self.main_input_name]
                    attention_mask = batch.get("attention_mask", None)
                else:
                    generation_inputs = batch
                    attention_mask = None

                predictions = self.model.generate(generation_inputs, attention_mask=attention_mask)
            else:
                predictions = self.model.predict(batch)
            predictions = dict(predictions)
            if self.output_cols is not None:
                predictions = {key: predictions[key] for key in self.output_cols}
            prediction_list.append(predictions)
            if not self.use_keras_label:
                labels = {key: batch[key].numpy() for key in self.label_cols}
            elif isinstance(labels, dict):
                labels = {key: array.numpy() for key, array in labels.items()}
            elif isinstance(labels, list) or isinstance(labels, tuple):
                labels = [array.numpy() for array in labels]
            elif isinstance(labels, tf.Tensor):
                labels = labels.numpy()
            else:
                raise TypeError(f"Confused by labels of type {type(labels)}")
            label_list.append(labels)

        prediction_list = self._postprocess_predictions_or_labels(prediction_list)
        label_list = self._postprocess_predictions_or_labels(label_list)

        metric_output = self.metric_fn(prediction_list, label_list, **self.metric_fn_kwargs)
        if not isinstance(metric_output, dict):
            raise TypeError(
                f"metric_fn should return a dict mapping metric names to values but instead returned {metric_output}"
            )
        # This is the critical bit - Keras passes a dict containing the loss and standard metric values for this epoch
        # in the logs argument. Ordinarily, this is so the callback can read them, but in this case we write a bunch of
        # new keys in there, which will then get read by the History callback and treated like any other metric value.
        # I promise that I have it in writing from Chollet that this is okay.
        logs.update(metric_output)


class PushToHubCallback(Callback):
    def __init__(
        self,
        output_dir: Union[str, Path],
        save_strategy: Union[str, IntervalStrategy] = "epoch",
        save_steps: Optional[int] = None,
        tokenizer: Optional[PreTrainedTokenizerBase] = None,
        hub_model_id: Optional[str] = None,
        hub_token: Optional[str] = None,
        checkpoint: bool = False,
        **model_card_args
    ):
        """
        output_dir (`str`):
            The output directory where the model predictions and checkpoints will be written and synced with the
            repository on the Hub.
        save_strategy (`str` or [`~trainer_utils.IntervalStrategy`], *optional*, defaults to `"epoch"`):
            The checkpoint save strategy to adopt during training. Possible values are:

                - `"no"`: No save is done during training.
                - `"epoch"`: Save is done at the end of each epoch.
                - `"steps"`: Save is done every `save_steps`
        save_steps (`int`, *optional*):
            The number of steps between saves when using the "steps" save_strategy.
        tokenizer (`PreTrainedTokenizerBase`, *optional*):
            The tokenizer used by the model. If supplied, will be uploaded to the repo alongside the weights.
        hub_model_id (`str`, *optional*):
            The name of the repository to keep in sync with the local *output_dir*. It can be a simple model ID in
            which case the model will be pushed in your namespace. Otherwise it should be the whole repository name,
            for instance `"user_name/model"`, which allows you to push to an organization you are a member of with
            `"organization_name/model"`.

            Will default to to the name of `output_dir`.
        hub_token (`str`, *optional*):
            The token to use to push the model to the Hub. Will default to the token in the cache folder obtained with
            `huggingface-cli login`.
        checkpoint (`bool`, *optional*, defaults to `False`):
            Whether to save full training checkpoints (including epoch and optimizer state) to allow training to be
            resumed. Only usable when *save_strategy* is *epoch*.
        """
        super().__init__()
        if checkpoint and save_strategy != "epoch":
            raise ValueError("Cannot save checkpoints when save_strategy is not 'epoch'!")
        if isinstance(save_strategy, str):
            save_strategy = IntervalStrategy(save_strategy.lower())
        self.save_strategy = save_strategy
        if self.save_strategy == IntervalStrategy.STEPS and (not isinstance(save_steps, int) or save_steps <= 0):
            raise ValueError("Please supply a positive integer argument for save_steps when save_strategy == 'steps'!")
        self.save_steps = save_steps
        output_dir = Path(output_dir)
        if hub_model_id is None:
            hub_model_id = output_dir.absolute().name
        if "/" not in hub_model_id:
            hub_model_id = get_full_repo_name(hub_model_id, token=hub_token)

        self.output_dir = output_dir
        self.hub_model_id = hub_model_id
        self.repo = Repository(
            str(self.output_dir),
            clone_from=self.hub_model_id,
            use_auth_token=hub_token if hub_token else True,
        )
        self.tokenizer = tokenizer
        self.last_job = None
        self.checkpoint = checkpoint
        self.training_history = None
        self.model_card_args = model_card_args

    def on_train_begin(self, logs=None):
        # Although we can access model.history, we have no guarantees that the History callback will fire before this
        # one, so we keep track of it here too
        self.training_history = []

    def on_train_batch_end(self, batch, logs=None):
        if self.save_strategy == IntervalStrategy.STEPS and batch + 1 % self.save_steps == 0:
            if self.last_job is not None and not self.last_job.is_done:
                return  # The last upload is still running, don't start another
            self.model.save_pretrained(self.output_dir)
            if self.tokenizer is not None:
                self.tokenizer.save_pretrained(self.output_dir)
            _, self.last_job = self.repo.push_to_hub(
                commit_message=f"Training in progress steps {batch}", blocking=False
            )

    def on_epoch_end(self, epoch, logs=None):
        if "epoch" not in logs:
            logs["epoch"] = epoch
        self.training_history.append(logs)
        if self.save_strategy == IntervalStrategy.EPOCH:
            if self.last_job is not None and not self.last_job.is_done:
                return  # The last upload is still running, don't start another
            self.model.save_pretrained(self.output_dir)
            if self.tokenizer is not None:
                self.tokenizer.save_pretrained(self.output_dir)
            if self.checkpoint:
                checkpoint_dir = os.path.join(self.output_dir, "checkpoint")
                self.model._save_checkpoint(checkpoint_dir, epoch)
            train_summary = TrainingSummary.from_keras(
                model=self.model,
                model_name=self.hub_model_id,
                keras_history=self.training_history,
                **self.model_card_args,
            )
            model_card = train_summary.to_model_card()
            with (self.output_dir / "README.md").open("w") as f:
                f.write(model_card)
            _, self.last_job = self.repo.push_to_hub(
                commit_message=f"Training in progress epoch {epoch}", blocking=False
            )

    def on_train_end(self, logs=None):
        if self.last_job is not None and not self.last_job.is_done:
            logger.info("Waiting for existing upload to finish...")
            while not self.last_job.is_done:
                sleep(1)
        self.model.save_pretrained(self.output_dir)
        if self.tokenizer is not None:
            self.tokenizer.save_pretrained(self.output_dir)
        train_summary = TrainingSummary.from_keras(
            model=self.model, model_name=self.hub_model_id, keras_history=self.training_history, **self.model_card_args
        )
        model_card = train_summary.to_model_card()
        with (self.output_dir / "README.md").open("w") as f:
            f.write(model_card)
        self.repo.push_to_hub(commit_message="End of training", blocking=True)
