from typing import Optional

import torch.nn as nn
from transformers import LlamaConfig, LlamaModel

from ..base import Critic


class LlamaCritic(Critic):
    """
    Llama Critic model.

    Args:
        pretrained (str): Pretrained model name or path.
        config (LlamaConfig): Model config.
        lora_rank (int): LoRA rank.
        lora_train_bias (str): LoRA bias training mode.
    """

    def __init__(self,
                 pretrained: Optional[str] = None,
                 config: Optional[LlamaConfig] = None,
                 lora_rank: int = 0,
                 lora_train_bias: str = 'none',
                 **kwargs) -> None:

        if pretrained is not None:
            model = LlamaModel.from_pretrained(pretrained)
        elif config is not None:
            model = LlamaModel(config)
        else:
            model = LlamaModel(LlamaConfig())

        value_head = nn.Linear(model.config.hidden_size, 1)
        super().__init__(model, value_head, lora_rank, lora_train_bias, **kwargs)