import inspect
import os
import re
from typing import Callable, Dict, List, Optional, Tuple, Union

import datasets
import torch
from packaging import version
from torch import nn
from torch.utils.data.dataset import Dataset

from transformers import PreTrainedModel, Seq2SeqTrainer, Trainer, __version__
from transformers.adapters.composition import AdapterCompositionBlock, Fuse
from transformers.dependency_versions_check import dep_version_check
from transformers.integrations import is_fairscale_available
from transformers.modeling_utils import unwrap_model

from ..configuration_utils import PretrainedConfig
from ..data.data_collator import DataCollator
from ..file_utils import CONFIG_NAME, WEIGHTS_NAME, is_sagemaker_mp_enabled, logger
from ..optimization import Adafactor, AdamW
from ..tokenization_utils_base import PreTrainedTokenizerBase
from ..trainer_callback import TrainerCallback, TrainerControl, TrainerState
from ..trainer_pt_utils import get_parameter_names
from ..trainer_utils import EvalPrediction, ShardedDDPOption
from ..training_args import TrainingArguments


if is_fairscale_available():
    dep_version_check("fairscale")
    from fairscale.optim import OSS

if is_sagemaker_mp_enabled():
    import smdistributed.modelparallel.torch as smp


class AdapterTrainer(Trainer):
    def __init__(
        self,
        model: Union[PreTrainedModel, nn.Module] = None,
        args: TrainingArguments = None,
        data_collator: Optional[DataCollator] = None,
        train_dataset: Optional[Dataset] = None,
        eval_dataset: Optional[Dataset] = None,
        tokenizer: Optional[PreTrainedTokenizerBase] = None,
        model_init: Callable[[], PreTrainedModel] = None,
        compute_metrics: Optional[Callable[[EvalPrediction], Dict]] = None,
        callbacks: Optional[List[TrainerCallback]] = None,
        adapter_names: Optional[List[List[str]]] = None,
        optimizers: Tuple[torch.optim.Optimizer, torch.optim.lr_scheduler.LambdaLR] = (None, None),
    ):
        super().__init__(
            model,
            args,
            data_collator,
            train_dataset,
            eval_dataset,
            tokenizer=tokenizer,
            model_init=model_init,
            compute_metrics=compute_metrics,
            callbacks=[AdapterTrainerCallback(self)] + callbacks if callbacks else [AdapterTrainerCallback(self)],
            optimizers=optimizers,
        )

        if adapter_names is not None:
            self.model.set_active_adapters(adapter_names)
        # Set the defaults for loading/ saving model & adapters
        if isinstance(self.model, PreTrainedModel):
            model_freezed = getattr(self.model.base_model, "model_freezed", False)
        else:
            model_freezed = False
        if model_freezed and self.model.active_adapters:
            # Check if training AdapterFusion
            self.train_adapter_fusion = (
                isinstance(self.model.active_adapters, Fuse)
                or isinstance(self.model.active_adapters, AdapterCompositionBlock)
                and any([isinstance(child, Fuse) for child in self.model.active_adapters.children])
            )
        if model.active_adapters is None:
            raise ValueError(
                "Expected a model with an active adapter setup. "
                "If you want tu fully finetune the model use the Trainer class"
            )

    def create_optimizer(self):
        """
        Setup the optimizer.

        We provide a reasonable default that works well. If you want to use something else, you can pass a tuple in the
        Trainer's init through :obj:`optimizers`, or subclass and override this method in a subclass.
        """
        if self.optimizer is None:
            decay_parameters = get_parameter_names(self.model, [nn.LayerNorm])
            decay_parameters = [name for name in decay_parameters if "bias" not in name]
            if hasattr(self.model, "config") and hasattr(self.model.config, "adapters"):
                match_str = r"adapter_fusion_layer\..*\.value"
                decay_parameters = [name for name in decay_parameters if not re.match(match_str, name)]
            optimizer_grouped_parameters = [
                {
                    "params": [p for n, p in self.model.named_parameters() if n in decay_parameters],
                    "weight_decay": self.args.weight_decay,
                },
                {
                    "params": [p for n, p in self.model.named_parameters() if n not in decay_parameters],
                    "weight_decay": 0.0,
                },
            ]
            if self.args.adafactor:
                optimizer_cls = Adafactor
                optimizer_kwargs = {"scale_parameter": False, "relative_step": False}
            else:
                optimizer_cls = AdamW
                optimizer_kwargs = {
                    "betas": (self.args.adam_beta1, self.args.adam_beta2),
                    "eps": self.args.adam_epsilon,
                }
            optimizer_kwargs["lr"] = self.args.learning_rate
            if self.sharded_ddp == ShardedDDPOption.SIMPLE:
                self.optimizer = OSS(
                    params=optimizer_grouped_parameters,
                    optim=optimizer_cls,
                    **optimizer_kwargs,
                )
            else:
                self.optimizer = optimizer_cls(optimizer_grouped_parameters, **optimizer_kwargs)

        if is_sagemaker_mp_enabled():
            self.optimizer = smp.DistributedOptimizer(self.optimizer)

    def _save(self, output_dir: Optional[str] = None, state_dict=None):
        # If we are executing this function, we are the process zero, so we don't check for that.
        output_dir = output_dir if output_dir is not None else self.args.output_dir
        os.makedirs(output_dir, exist_ok=True)
        logger.info(f"Saving model checkpoint to {output_dir}")
        # Save a trained model and configuration using `save_pretrained()`.
        # They can then be reloaded using `from_pretrained()`
        if not isinstance(self.model, PreTrainedModel):
            if isinstance(unwrap_model(self.model), PreTrainedModel):
                if state_dict is None:
                    state_dict = self.model.state_dict()
                unwrap_model(self.model).save_pretrained(output_dir, state_dict=state_dict)
            else:
                logger.info("Trainer.model is not a `PreTrainedModel`, only saving its state dict.")
                if state_dict is None:
                    state_dict = self.model.state_dict()
                torch.save(state_dict, os.path.join(output_dir, WEIGHTS_NAME))
        else:
            self.model.save_all_adapters(output_dir)
            if self.train_adapter_fusion:
                self.model.save_all_adapter_fusions(output_dir)
            if hasattr(self.model, "heads"):
                self.model.save_all_heads(output_dir)
        if self.tokenizer is not None:
            self.tokenizer.save_pretrained(output_dir)

        # Good practice: save your training arguments together with the trained model
        torch.save(self.args, os.path.join(output_dir, "training_args.bin"))

    def _load(self, resume_from_checkpoint):
        args = self.args
        if os.path.isfile(os.path.join(resume_from_checkpoint, WEIGHTS_NAME)):
            logger.info(f"Loading model from {resume_from_checkpoint}).")

        if os.path.isfile(os.path.join(resume_from_checkpoint, CONFIG_NAME)):
            config = PretrainedConfig.from_json_file(os.path.join(resume_from_checkpoint, CONFIG_NAME))
            checkpoint_version = config.transformers_version
            if checkpoint_version is not None and checkpoint_version != __version__:
                logger.warn(
                    f"You are resuming training from a checkpoint trained with {checkpoint_version} of "
                    f"Transformers but your current version is {__version__}. This is not recommended and could "
                    "yield to errors or unwanted behaviors."
                )

        if args.deepspeed:
            # will be resumed in deepspeed_init
            pass
        else:
            if os.path.isdir(resume_from_checkpoint):
                adapter_loaded = self._load_adapters(resume_from_checkpoint)
                self._load_adapter_fusions(resume_from_checkpoint)
                # Save all heads for a model with heads
                if hasattr(self.model, "heads"):
                    self._load_heads(resume_from_checkpoint)

            if not adapter_loaded:
                raise Exception("Can't find a valid checkpoint at {}".format(resume_from_checkpoint))

    def _load_adapters(self, resume_from_checkpoint):
        adapter_loaded = False
        for file_name in os.listdir(resume_from_checkpoint):
            if os.path.isdir(os.path.join(resume_from_checkpoint, file_name)):
                if "," not in file_name and "adapter_config.json" in os.listdir(
                    os.path.join(resume_from_checkpoint, file_name)
                ):
                    self.model.load_adapter(os.path.join(os.path.join(resume_from_checkpoint, file_name)))
                    adapter_loaded = True
        return adapter_loaded

    def _load_adapter_fusions(self, resume_from_checkpoint):
        for file_name in os.listdir(resume_from_checkpoint):
            if os.path.isdir(os.path.join(resume_from_checkpoint, file_name)):
                if "," in file_name:
                    self.model.load_adapter_fusion(os.path.join(resume_from_checkpoint, file_name))

    def _load_heads(self, resume_from_checkpoint):
        for file_name in os.listdir(resume_from_checkpoint):
            if os.path.isdir(os.path.join(resume_from_checkpoint, file_name)):
                if "," not in file_name and "head_config.json" in os.listdir(
                    os.path.join(resume_from_checkpoint, file_name)
                ):
                    self.model.load_head(os.path.join(resume_from_checkpoint, file_name))

    def _remove_unused_columns(self, dataset: "datasets.Dataset", description: Optional[str] = None):
        if not self.args.remove_unused_columns:
            return dataset
        if self._signature_columns is None:
            # Inspect model forward signature to keep only the arguments it accepts.
            signature = inspect.signature(self.model.forward)
            self._signature_columns = list(signature.parameters.keys())
            # Labels may be named label or label_ids, the default data collator handles that.
            self._signature_columns += ["label", "label_ids"]
            self._signature_columns += self.label_names
        columns = [k for k in self._signature_columns if k in dataset.column_names]
        ignored_columns = list(set(dataset.column_names) - set(self._signature_columns))
        if len(ignored_columns) > 0:
            dset_description = "" if description is None else f"in the {description} set "
            logger.info(
                f"The following columns {dset_description} don't have a corresponding argument in "
                f"`{self.model.__class__.__name__}.forward` and have been ignored: {', '.join(ignored_columns)}."
            )

        if version.parse(datasets.__version__) < version.parse("1.4.0"):
            dataset.set_format(
                type=dataset.format["type"], columns=columns, format_kwargs=dataset.format["format_kwargs"]
            )
            return dataset
        else:
            return dataset.remove_columns(ignored_columns)


class AdapterTrainerCallback(TrainerCallback):
    def __init__(self, trainer):
        super().__init__()
        self.trainer = trainer

    def on_train_begin(self, args: TrainingArguments, state: TrainerState, control: TrainerControl, **kwargs):
        model = kwargs.pop("model")
        model_freezed = getattr(model.base_model, "model_freezed", False)
        if not model_freezed:
            raise ValueError("The model is not freezed. For training adapters please call the train_adapters() method")

    def on_train_end(self, args: TrainingArguments, state: TrainerState, control: TrainerControl, **kwargs):
        model = kwargs.pop("model")
        if args.load_best_model_at_end and state.best_model_checkpoint is not None:

            logger.info(f"Loading best adapter(s) from {state.best_model_checkpoint} (score: {state.best_metric}).")
            # attempt to re-load all adapters from checkpoint
            for adapter in model.config.adapters.adapters:
                adapter_dir = os.path.join(state.best_model_checkpoint, adapter)
                if os.path.exists(adapter_dir):
                    model.load_adapter(adapter_dir)
            if self.trainer.train_adapter_fusion:
                logger.info(
                    f"Loading best adapter fusion(s) from {state.best_model_checkpoint} (score: {state.best_metric})."
                )
                # attempt to re-load all adapter fusions from checkpoint
                fusion_models = getattr(self.model.config, "adapter_fusion_models", [])
                for fusion in fusion_models:
                    fusion_dir = os.path.join(state.best_model_checkpoint, fusion)
                    if os.path.exists(fusion_dir):
                        self.model.load_adapter_fusion(fusion_dir)

    def on_step_end(self, args: TrainingArguments, state: TrainerState, control: TrainerControl, **kwargs):
        # apply adapter fusion weight regularization on the value matrix
        model = kwargs.pop("model")
        if self.trainer.train_adapter_fusion:
            fusion_reg_loss = model.base_model.get_fusion_regularization_loss()
            fusion_reg_loss.backward()


class Seq2SeqAdapterTrainer(AdapterTrainer, Seq2SeqTrainer):
    pass
