import torch
from torch import nn
from transformers import PreTrainedModel, AutoModelForCausalLM, AutoTokenizer
from transformers.modeling_outputs import CausalLMOutputWithPast
from torch.nn import CrossEntropyLoss
from typing import Optional
from .configuration_minGRULM import MinGRULMConfig
from minGRU_pytorch.minGRULM import minGRULM

# Wrapper class for device compatibility
class MinGRULMWrapped(nn.Module):
    def __init__(self, min_gru_model):
        super().__init__()
        self.min_gru_model = min_gru_model
        self.device = torch.device("cuda")  # Default device

    def forward(self, *args, **kwargs):
        # Move input tensors to the correct device
        args = [arg.to(self.device) if isinstance(arg, torch.Tensor) else arg for arg in args]
        kwargs = {k: v.to(self.device) if isinstance(v, torch.Tensor) else v for k, v in kwargs.items()}
        return self.min_gru_model(*args, **kwargs)

    def to(self, device):
        # Update device information
        self.device = device
        self.min_gru_model.to(device)
        return self


class MinGRULMPreTrainedModel(PreTrainedModel):
    config_class = MinGRULMConfig
    base_model_prefix = "model"

    def _init_weights(self, module):
        std = 0.02
        if isinstance(module, nn.Linear):
            module.weight.data.normal_(mean=0.0, std=std)
            if module.bias is not None:
                module.bias.data.zero_()
        elif isinstance(module, nn.Embedding):
            module.weight.data.normal_(mean=0.0, std=std)
            if module.padding_idx is not None:
                module.weight.data[module.padding_idx].zero_()


class MinGRULMForCausalLM(MinGRULMPreTrainedModel):
    def __init__(self, config: MinGRULMConfig):
        super().__init__(config)

        # Load model from minGRULM library and wrap it
        raw_min_gru = minGRULM(
            num_tokens=config.vocab_size,
            dim=config.d_model,
            depth=config.n_layer,
            ff_mult=config.ff_mult,
            min_gru_expansion=config.min_gru_expansion,
            enable_conv=config.enable_conv,
        )
        self.model = MinGRULMWrapped(raw_min_gru)

        # Language modeling head
        self.lm_head = nn.Linear(config.d_model, config.vocab_size, bias=False)

        # Initialize weights (if required for missing layers)
        self.initialize_layers()

        self.post_init()

    def get_input_embeddings(self):
        return self.model.min_gru_model.token_emb

    def set_input_embeddings(self, value):
        self.model.min_gru_model.token_emb = value

    def get_output_embeddings(self):
        return self.lm_head

    def prepare_inputs_for_generation(self, input_ids: torch.LongTensor, **kwargs):
        # Ensure that inputs for generation are properly handled
        return {"input_ids": input_ids, "attention_mask": kwargs.get("attention_mask", None)}

    def forward(
        self,
        input_ids: torch.LongTensor,
        labels: Optional[torch.LongTensor] = None,
        return_dict: Optional[bool] = True,
        **kwargs
    ):
        # Forward pass through the wrapped model
        logits = self.model(input_ids)

        loss = None
        if labels is not None:
            shift_logits = logits[..., :-1, :].contiguous()
            shift_labels = labels[..., 1:].contiguous()
            loss_fct = CrossEntropyLoss()
            loss = loss_fct(
                shift_logits.view(-1, self.config.vocab_size),
                shift_labels.view(-1),
            )

        if not return_dict:
            return (loss, logits) if loss is not None else (logits,)

        return CausalLMOutputWithPast(
            loss=loss,
            logits=logits,
        )

    def initialize_layers(self):
        """
        Initialize missing layers in the model, such as custom layers or parts of the minGRULM.
        If layers are already initialized, we can skip them.
        """
        # Example: Initialize layers manually if needed
        for name, module in self.model.min_gru_model.named_children():
            if isinstance(module, nn.Module):
                if 'token_emb' in name:
                    # Token embeddings, if needed, you can initialize with a custom scheme
                    nn.init.xavier_uniform_(module.weight)
                elif isinstance(module, nn.Linear):
                    # Initialize Linear layers if not initialized already
                    if module.weight is not None:
                        nn.init.xavier_uniform_(module.weight)
                    if module.bias is not None:
                        nn.init.zeros_(module.bias)
                # Initialize other layers similarly, depending on the type
                elif isinstance(module, nn.LayerNorm):
                    # Initialize LayerNorm layers
                    nn.init.constant_(module.weight, 1.0)
                    nn.init.constant_(module.bias, 0)