from transformers.trainer import *
from transformers.deepspeed import is_deepspeed_zero3_enabled
from peft import get_peft_model_state_dict

class BiTrainer(Trainer):
    use_lora: bool

    def _save(self, output_dir: Optional[str] = None, state_dict=None):
        if not self.use_lora:
            super()._save(output_dir, state_dict)
            return

        output_dir = output_dir if output_dir is not None else self.args.output_dir
        os.makedirs(output_dir, exist_ok=True)
        logger.info("Saving model checkpoint to %s", output_dir)
        # Save a trained model and configuration using `save_pretrained()`.
        # They can then be reloaded using `from_pretrained()`
        if not hasattr(self.model, 'save'):
            raise NotImplementedError(
                f'MODEL {self.model.__class__.__name__} '
                f'does not support save interface')
        else:
            self.model.save(output_dir)
        # if self.tokenizer is not None and self.is_world_process_zero():
        #     self.tokenizer.save_pretrained(output_dir)

        torch.save(self.args, os.path.join(output_dir, "training_args.bin"))

        if is_deepspeed_zero3_enabled():
            if state_dict is None:
                state_dict = self.model.state_dict()
            prefix = 'model.'
            assert all(k.startswith(prefix) for k in state_dict.keys()), list(state_dict.keys())
            state_dict = {k[len(prefix):]: v for k, v in state_dict.items()}
            lora_state_dict = get_peft_model_state_dict(self.model.model, state_dict)
            if self.args.process_index <= 0:
                torch.save(lora_state_dict, os.path.join(output_dir, "adapter_model.bin"))
                print(f"Save adapter model at {output_dir}")

    def compute_loss(self, model, inputs, return_outputs=False):
        """
        How the loss is computed by Trainer. By default, all models return the loss in the first element.

        Subclass and override for custom behavior.
        """
        outputs = model(**inputs)
        loss = outputs.loss

        return (loss, outputs) if return_outputs else loss