import torch
import torch.nn as nn
from transformers.modeling_bart import BartForConditionalGeneration
from relogic.logickit.dataflow.semtransparse.grammar.keywords import SKETCH_KEYWORDS, KEYWORDS
import logging
import os

logger = logging.getLogger(__name__)
WEIGHTS_NAME = "pytorch_model.bin"

class SQL2TextModel(nn.Module):
  """
  output: tuple: (loss, ) in training
  """
  def __init__(self):
    super().__init__()
    self.bert = BartForConditionalGeneration.from_pretrained("facebook/bart-large")


  def forward(self, *input, **kwargs):
    input_ids = kwargs.pop("input_ids")

    pad_token_id = kwargs.pop("pad_token_id")
    attention_mask = (input_ids != pad_token_id).long()

    if self.training:
      output_ids = kwargs.pop('labels')
      y_ids = output_ids[:, :-1].contiguous()
      lm_labels = output_ids[:, 1:].clone()
      lm_labels[output_ids[:, 1:] == pad_token_id] = -100

      outputs = self.bert(input_ids,
                          attention_mask=attention_mask, decoder_input_ids=y_ids, lm_labels=lm_labels, )
      return (outputs[0],)

    else:
      label_eos_id = kwargs.pop("label_eos_id")
      label_bos_id = kwargs.pop("label_bos_id")
      label_padding_id = kwargs.pop("label_padding_id")
      generated_ids = self.bert.generate(
        input_ids=input_ids,
        attention_mask=attention_mask,
        num_beams=3,
        max_length=60,
        length_penalty=2.0,
        early_stopping=True,
        use_cache=True,
        decoder_start_token_id=label_bos_id,
        eos_token_id=label_eos_id,
        pad_token_id=label_padding_id
      )

      output_ids = kwargs.pop('labels')
      y_ids = output_ids[:, :-1].contiguous()
      lm_labels = output_ids[:, 1:].clone()
      lm_labels[output_ids[:, 1:] == pad_token_id] = -100

      outputs = self.bert(input_ids,
                          attention_mask=attention_mask, decoder_input_ids=y_ids, lm_labels=lm_labels, )
      return (outputs[0].detach(), generated_ids)

  def save_pretrained(self, save_directory):
    """ Save a model and its configuration file to a directory, so that it
        can be re-loaded using the `:func:`~transformers.PreTrainedModel.from_pretrained`` class method.

        Arguments:
            save_directory: directory to which to save.
    """
    assert os.path.isdir(
      save_directory
    ), "Saving path should be a directory where the model and configuration can be saved"

    # Only save the model itself if we are using distributed training
    model_to_save = self.module if hasattr(self, "module") else self

    # Attach architecture to the config
    # model_to_save.config.architectures = [model_to_save.__class__.__name__]

    # If we save using the predefined names, we can load using `from_pretrained`
    output_model_file = os.path.join(save_directory, WEIGHTS_NAME)

    torch.save(model_to_save.state_dict(), output_model_file)

    logger.info("Model weights saved in {}".format(output_model_file))