import os
import sys
from dataclasses import dataclass, field
from typing import Optional

from transformers import HfArgumentParser, TrainingArguments, set_seed
from trl import SFTTrainer
from utils import create_and_prepare_model, create_datasets


# Define and parse arguments.
@dataclass
class ModelArguments:
    """
    Arguments pertaining to which model/config/tokenizer we are going to fine-tune from.
    """

    model_name_or_path: str = field(
        metadata={"help": "Path to pretrained model or model identifier from huggingface.co/models"}
    )
    chat_template_format: Optional[str] = field(
        default="none",
        metadata={
            "help": "chatml|zephyr|none. Pass `none` if the dataset is already formatted with the chat template."
        },
    )
    lora_alpha: Optional[int] = field(default=16)
    lora_dropout: Optional[float] = field(default=0.1)
    lora_r: Optional[int] = field(default=64)
    lora_target_modules: Optional[str] = field(
        default="q_proj,k_proj,v_proj,o_proj,down_proj,up_proj,gate_proj",
        metadata={"help": "comma separated list of target modules to apply LoRA layers to"},
    )
    use_nested_quant: Optional[bool] = field(
        default=False,
        metadata={"help": "Activate nested quantization for 4bit base models"},
    )
    bnb_4bit_compute_dtype: Optional[str] = field(
        default="float16",
        metadata={"help": "Compute dtype for 4bit base models"},
    )
    bnb_4bit_quant_storage_dtype: Optional[str] = field(
        default="uint8",
        metadata={"help": "Quantization storage dtype for 4bit base models"},
    )
    bnb_4bit_quant_type: Optional[str] = field(
        default="nf4",
        metadata={"help": "Quantization type fp4 or nf4"},
    )
    use_flash_attn: Optional[bool] = field(
        default=False,
        metadata={"help": "Enables Flash attention for training."},
    )
    use_peft_lora: Optional[bool] = field(
        default=False,
        metadata={"help": "Enables PEFT LoRA for training."},
    )
    use_8bit_quantization: Optional[bool] = field(
        default=False,
        metadata={"help": "Enables loading model in 8bit."},
    )
    use_4bit_quantization: Optional[bool] = field(
        default=False,
        metadata={"help": "Enables loading model in 4bit."},
    )
    use_reentrant: Optional[bool] = field(
        default=False,
        metadata={"help": "Gradient Checkpointing param. Refer the related docs"},
    )
    use_unsloth: Optional[bool] = field(
        default=False,
        metadata={"help": "Enables UnSloth for training."},
    )


@dataclass
class DataTrainingArguments:
    dataset_name: Optional[str] = field(
        default="timdettmers/openassistant-guanaco",
        metadata={"help": "The preference dataset to use."},
    )
    packing: Optional[bool] = field(
        default=False,
        metadata={"help": "Use packing dataset creating."},
    )
    dataset_text_field: str = field(default="text", metadata={"help": "Dataset field to use as input text."})
    max_seq_length: Optional[int] = field(default=512)
    append_concat_token: Optional[bool] = field(
        default=False,
        metadata={"help": "If True, appends `eos_token_id` at the end of each sample being packed."},
    )
    add_special_tokens: Optional[bool] = field(
        default=False,
        metadata={"help": "If True, tokenizers adds special tokens to each sample being packed."},
    )
    splits: Optional[str] = field(
        default="train,test",
        metadata={"help": "Comma separate list of the splits to use from the dataset."},
    )


def main(model_args, data_args, training_args):
    # Set seed for reproducibility
    set_seed(training_args.seed)

    # model
    model, peft_config, tokenizer = create_and_prepare_model(model_args, data_args, training_args)

    # gradient ckpt
    model.config.use_cache = not training_args.gradient_checkpointing
    training_args.gradient_checkpointing = training_args.gradient_checkpointing and not model_args.use_unsloth
    if training_args.gradient_checkpointing:
        training_args.gradient_checkpointing_kwargs = {"use_reentrant": model_args.use_reentrant}

    # datasets
    train_dataset, eval_dataset = create_datasets(
        tokenizer,
        data_args,
        training_args,
        apply_chat_template=model_args.chat_template_format != "none",
    )

    # trainer
    trainer = SFTTrainer(
        model=model,
        tokenizer=tokenizer,
        args=training_args,
        train_dataset=train_dataset,
        eval_dataset=eval_dataset,
        peft_config=peft_config,
        packing=data_args.packing,
        dataset_kwargs={
            "append_concat_token": data_args.append_concat_token,
            "add_special_tokens": data_args.add_special_tokens,
        },
        dataset_text_field=data_args.dataset_text_field,
        max_seq_length=data_args.max_seq_length,
    )
    trainer.accelerator.print(f"{trainer.model}")
    trainer.model.print_trainable_parameters()

    # train
    checkpoint = None
    if training_args.resume_from_checkpoint is not None:
        checkpoint = training_args.resume_from_checkpoint
    trainer.train(resume_from_checkpoint=checkpoint)

    # saving final model
    if trainer.is_fsdp_enabled:
        trainer.accelerator.state.fsdp_plugin.set_state_dict_type("FULL_STATE_DICT")
    trainer.save_model()


if __name__ == "__main__":
    parser = HfArgumentParser((ModelArguments, DataTrainingArguments, TrainingArguments))
    if len(sys.argv) == 2 and sys.argv[1].endswith(".json"):
        # If we pass only one argument to the script and it's the path to a json file,
        # let's parse it to get our arguments.
        model_args, data_args, training_args = parser.parse_json_file(json_file=os.path.abspath(sys.argv[1]))
    else:
        model_args, data_args, training_args = parser.parse_args_into_dataclasses()
    main(model_args, data_args, training_args)