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# SPDX-License-Identifier: Apache-2.0
#
# 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
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import shutil
from pathlib import Path

import torch
from transformers import Trainer, TrainerCallback


def safe_save_model_for_hf_trainer(trainer: Trainer, output_dir: str):
    """Collects the state dict and dump to disk."""
    if trainer.deepspeed:
        torch.cuda.synchronize()
        trainer.save_model(output_dir, _internal_call=True)
        return

    state_dict = trainer.model.state_dict()
    if trainer.args.should_save:
        cpu_state_dict = {key: value.cpu() for key, value in state_dict.items()}
        del state_dict
        trainer._save(output_dir, state_dict=cpu_state_dict)  # noqa


class CheckpointFormatCallback(TrainerCallback):
    """This callback format checkpoint to make them standalone. For now, it copies all config
    files to /checkpoint-{step}/experiment_cfg/:
    - conf.yaml
    - initial_actions.npz
    - metadata.json
    """

    def __init__(self, run_name: str, exp_cfg_dir: Path | None = None):
        """
        Args:
            run_name: Name of the experiment run
            exp_cfg_dir: Path to the directory containing all experiment metadata
        """
        self.exp_cfg_dir = exp_cfg_dir

    def on_save(self, args, state, control, **kwargs):
        """Called after the trainer saves a checkpoint."""
        if state.is_world_process_zero:
            checkpoint_dir = Path(args.output_dir) / f"checkpoint-{state.global_step}"

            # Copy experiment config directory if provided
            if self.exp_cfg_dir is not None:
                exp_cfg_dst = checkpoint_dir / self.exp_cfg_dir.name
                if self.exp_cfg_dir.exists():
                    shutil.copytree(self.exp_cfg_dir, exp_cfg_dst, dirs_exist_ok=True)