# coding=utf-8
from dataclasses import dataclass
from typing import List, Optional, Tuple, Union

import torch
import torch.utils.checkpoint
from torch import nn

from transformers import PreTrainedModel
from transformers.modeling_outputs import ModelOutput

from modeling_phi import PhiForCausalLM, InferenceParams
from processing_llava import OpenCLIPImageProcessor
from configuration_llava import LlavaConfig
from open_clip import create_model


@dataclass
class LlavaCausalLMOutputWithPast(ModelOutput):
    loss: Optional[torch.FloatTensor] = None
    logits: torch.FloatTensor = None
    past_key_values: Optional[List[torch.FloatTensor]] = None
    hidden_states: Optional[Tuple[torch.FloatTensor]] = None
    attentions: Optional[Tuple[torch.FloatTensor]] = None
    image_hidden_states: Optional[Tuple[torch.FloatTensor]] = None


class LlavaMultiModalProjector(nn.Module):
    def __init__(self, config: LlavaConfig):
        super().__init__()

        self.linear_1 = nn.Linear(
            config.vision_embed_dim,
            config.text_config.n_embd * config.projector_tokens_num,
            bias=True,
        )
        self.act = nn.GELU()
        self.linear_2 = nn.Linear(
            config.text_config.n_embd * config.projector_tokens_num,
            config.text_config.n_embd * config.projector_tokens_num,
            bias=True,
        )
        self.projector_tokens_num = config.projector_tokens_num

    def forward(self, image_features):
        hidden_states = self.linear_1(image_features)
        hidden_states = self.act(hidden_states)
        hidden_states = self.linear_2(hidden_states)
        hidden_states = hidden_states.reshape(
            hidden_states.shape[0],
            self.projector_tokens_num,
            int(hidden_states.shape[1] / self.projector_tokens_num),
        )
        return hidden_states


class LlavaPreTrainedModel(PreTrainedModel):
    config_class = LlavaConfig
    base_model_prefix = "model"
    supports_gradient_checkpointing = True
    _no_split_modules = ["LlavaVisionAttention"]
    _skip_keys_device_placement = "past_key_values"
    _supports_flash_attn_2 = True

    def __init__(self, config):
        super().__init__(config)

    def _init_weights(self, module):
        return

    @property
    def _supports_sdpa(self):
        """
        Retrieve language_model's attribute to check whether the model supports
        SDPA or not.
        """
        return self.language_model._supports_sdpa


class LlavaForConditionalGeneration(LlavaPreTrainedModel):
    def __init__(self, config: LlavaConfig):
        super().__init__(config)
        clip_model = create_model(config.vision_tower_name)
        self.vision_model = clip_model.visual

        self.multi_modal_projector = LlavaMultiModalProjector(config)
        self.vocab_size = config.vocab_size
        self.language_model = PhiForCausalLM(config.text_config)
        self.pad_token_id = (
            self.config.pad_token_id if self.config.pad_token_id is not None else -1
        )
        self.post_init()

    def get_input_embeddings(self):
        return self.language_model.get_input_embeddings()

    def set_input_embeddings(self, value):
        self.language_model.set_input_embeddings(value)

    def get_output_embeddings(self):
        return self.language_model.get_output_embeddings()

    def set_output_embeddings(self, new_embeddings):
        self.language_model.set_output_embeddings(new_embeddings)

    def set_decoder(self, decoder):
        self.language_model.transformer = decoder

    def get_decoder(self):
        return self.language_model.transformer

    def tie_weights(self):
        return self.language_model.tie_weights()

    def resize_token_embeddings(
        self, new_num_tokens: Optional[int] = None, pad_to_multiple_of=None
    ) -> nn.Embedding:
        model_embeds = self.language_model.resize_token_embeddings(
            new_num_tokens, pad_to_multiple_of
        )
        # update vocab size
        self.config.text_config.vocab_size = model_embeds.num_embeddings
        self.config.vocab_size = model_embeds.num_embeddings
        self.vocab_size = model_embeds.num_embeddings
        return model_embeds

    def _merge_input_ids_with_image_features(
        self, image_features, inputs_embeds, input_ids, attention_mask, position_ids
    ):
        num_images, num_image_patches, embed_dim = image_features.shape
        batch_size, sequence_length = input_ids.shape
        left_padding = not torch.sum(
            input_ids[:, -1] == torch.tensor(self.pad_token_id)
        )
        # 1. Create a mask to know where special image tokens are
        special_image_token_mask = input_ids == self.config.image_token_index
        num_special_image_tokens = torch.sum(special_image_token_mask, dim=-1)
        # Compute the maximum embed dimension
        max_embed_dim = (
            num_special_image_tokens.max() * (num_image_patches - 1)
        ) + sequence_length
        batch_indices, non_image_indices = torch.where(
            input_ids != self.config.image_token_index
        )

        # 2. Compute the positions where text should be written
        # Calculate new positions for text tokens in merged image-text sequence.
        # `special_image_token_mask` identifies image tokens. Each image token will be replaced by `nb_text_tokens_per_images - 1` text tokens.
        # `torch.cumsum` computes how each image token shifts subsequent text token positions.
        # - 1 to adjust for zero-based indexing, as `cumsum` inherently increases indices by one.
        new_token_positions = (
            torch.cumsum((special_image_token_mask * (num_image_patches - 1) + 1), -1)
            - 1
        )
        nb_image_pad = max_embed_dim - 1 - new_token_positions[:, -1]
        if left_padding:
            new_token_positions += nb_image_pad[:, None]  # offset for left padding
        text_to_overwrite = new_token_positions[batch_indices, non_image_indices]

        # 3. Create the full embedding, already padded to the maximum position
        final_embedding = torch.zeros(
            batch_size,
            max_embed_dim,
            embed_dim,
            dtype=inputs_embeds.dtype,
            device=inputs_embeds.device,
        )
        final_attention_mask = torch.zeros(
            batch_size,
            max_embed_dim,
            dtype=attention_mask.dtype,
            device=inputs_embeds.device,
        )
        # In case the Vision model or the Language model has been offloaded to CPU, we need to manually
        # set the corresponding tensors into their correct target device.
        target_device = inputs_embeds.device
        batch_indices, non_image_indices, text_to_overwrite = (
            batch_indices.to(target_device),
            non_image_indices.to(target_device),
            text_to_overwrite.to(target_device),
        )
        attention_mask = attention_mask.to(target_device)

        # 4. Fill the embeddings based on the mask. If we have ["hey" "<image>", "how", "are"]
        # we need to index copy on [0, 577, 578, 579] for the text and [1:576] for the image features
        final_embedding[batch_indices, text_to_overwrite] = inputs_embeds[
            batch_indices, non_image_indices
        ]
        final_attention_mask[batch_indices, text_to_overwrite] = attention_mask[
            batch_indices, non_image_indices
        ]

        # 5. Fill the embeddings corresponding to the images. Anything that is still zeros needs filling
        image_to_overwrite = torch.all(final_embedding == 0, dim=-1)
        image_to_overwrite &= image_to_overwrite.cumsum(-1) - 1 >= nb_image_pad[
            :, None
        ].to(target_device)

        if image_to_overwrite.sum() != image_features.shape[:-1].numel():
            raise ValueError(
                f"The input provided to the model are wrong. The number of image tokens is {torch.sum(special_image_token_mask)} while"
                f" the number of image given to the model is {num_images}. This prevents correct indexing and breaks batch generation."
            )

        final_embedding[image_to_overwrite] = (
            image_features.contiguous().reshape(-1, embed_dim).to(target_device)
        )
        final_attention_mask |= image_to_overwrite
        position_ids = (final_attention_mask.cumsum(-1) - 1).masked_fill_(
            (final_attention_mask == 0), 1
        )
        return final_embedding, final_attention_mask, position_ids

    def forward(
        self,
        input_ids: torch.LongTensor = None,
        pixel_values: torch.FloatTensor = None,
        attention_mask: Optional[torch.Tensor] = None,
        position_ids: Optional[torch.LongTensor] = None,
        past_key_values: Optional[List[torch.FloatTensor]] = None,
        inputs_embeds: Optional[torch.FloatTensor] = None,
        vision_feature_layer: Optional[int] = None,
        vision_feature_select_strategy: Optional[str] = None,
        labels: Optional[torch.LongTensor] = None,
        use_cache: Optional[bool] = None,
        output_attentions: Optional[bool] = None,
        output_hidden_states: Optional[bool] = None,
        return_dict: Optional[bool] = None,
    ) -> Union[Tuple, LlavaCausalLMOutputWithPast]:
        output_attentions = (
            output_attentions
            if output_attentions is not None
            else self.config.output_attentions
        )
        output_hidden_states = (
            output_hidden_states
            if output_hidden_states is not None
            else self.config.output_hidden_states
        )
        return_dict = (
            return_dict if return_dict is not None else self.config.use_return_dict
        )

        if inputs_embeds is None:
            # 1. Extra the input embeddings
            inputs_embeds = self.get_input_embeddings()(input_ids)

            # 2. Merge text and images
            if pixel_values is not None and input_ids.shape[1] != 1:
                image_outputs = self.vision_model(pixel_values)

                image_features = self.multi_modal_projector(image_outputs)
                (
                    inputs_embeds,
                    attention_mask,
                    position_ids,
                ) = self._merge_input_ids_with_image_features(
                    image_features,
                    inputs_embeds,
                    input_ids,
                    attention_mask,
                    position_ids,
                )
                # if labels is None:
                #     labels = torch.full_like(
                #         attention_mask, self.config.ignore_index
                #     ).to(torch.long)
            else:
                # In case input_ids.shape[1] == 1 & pixel_values==None & past_key_values != None, we are in the case of
                # generation with cache
                if (
                    past_key_values is not None
                    and pixel_values is not None
                    and input_ids.shape[1] == 1
                ):
                    # Retrieve the first layer to inspect the logits and mask out the hidden states
                    # that are set to 0
                    first_layer_past_key_value = past_key_values[0][0][:, :, :, 0]

                    # Sum all dimensions of head_dim (-2) to avoid random errors such as: https://github.com/huggingface/transformers/pull/28032#issuecomment-1863691941
                    batch_index, non_attended_tokens = torch.where(
                        first_layer_past_key_value.float().sum(-2) == 0
                    )

                    # Get the target length
                    target_seqlen = first_layer_past_key_value.shape[-1] + 1

                    extended_attention_mask = torch.ones(
                        (
                            attention_mask.shape[0],
                            target_seqlen - attention_mask.shape[1],
                        ),
                        dtype=attention_mask.dtype,
                        device=attention_mask.device,
                    )

                    # Zero-out the places where we don't need to attend
                    extended_attention_mask[batch_index, non_attended_tokens] = 0

                    attention_mask = torch.cat(
                        (attention_mask, extended_attention_mask), dim=1
                    )
                    position_ids = torch.sum(attention_mask, dim=1).unsqueeze(-1) - 1

        outputs = self.language_model(
            input_ids=None,
            attention_mask=attention_mask,
            position_ids=position_ids,
            past_key_values=past_key_values,
            inputs_embeds=inputs_embeds,
            use_cache=use_cache,
            output_attentions=output_attentions,
            output_hidden_states=output_hidden_states,
            return_dict=return_dict,
        )

        logits = outputs[0]

        loss = None
        if labels is not None:
            # Shift so that tokens < n predict n
            if attention_mask is not None:
                shift_attention_mask = attention_mask[..., 1:]
                shift_logits = logits[..., :-1, :][
                    shift_attention_mask.to(logits.device) != 0
                ].contiguous()
                shift_labels = labels[..., 1:][
                    shift_attention_mask.to(labels.device) != 0
                ].contiguous()
            else:
                shift_logits = logits[..., :-1, :].contiguous()
                shift_labels = labels[..., 1:].contiguous()
            # Flatten the tokens
            loss_fct = nn.CrossEntropyLoss()
            loss = loss_fct(
                shift_logits.view(-1, shift_logits.size(-1)),
                shift_labels.view(-1).to(shift_logits.device),
            )

        if not return_dict:
            output = (logits,) + outputs[1:]
            return (loss,) + output if loss is not None else output

        return LlavaCausalLMOutputWithPast(
            loss=loss,
            logits=logits,
            past_key_values=outputs.past_key_values,
            hidden_states=outputs.hidden_states,
            attentions=outputs.attentions,
        )

    def prepare_inputs_for_generation(
        self,
        input_ids,
        past_key_values=None,
        inputs_embeds=None,
        pixel_values=None,
        attention_mask=None,
        **kwargs,
    ):
        if past_key_values is not None:
            if isinstance(past_key_values, InferenceParams):
                cache_length = past_key_values.max_seqlen
                past_length = past_key_values.seqlen_offset
            else:
                cache_length = past_length = past_key_values[0][0].shape[2]

            # Keep only the unprocessed tokens:
            # 1 - If the length of the attention_mask exceeds the length of input_ids, then we are in a setting where
            # some of the inputs are exclusivelly passed as part of the cache (e.g. when passing input_embeds as
            # input)
            if (
                attention_mask is not None
                and attention_mask.shape[1] > input_ids.shape[1]
            ):
                input_ids = input_ids[:, -(attention_mask.shape[1] - past_length) :]
            # 2 - If the past_length is smaller than input_ids', then input_ids holds all input tokens. We can discard
            # input_ids based on the past_length.
            elif past_length < input_ids.shape[1]:
                input_ids = input_ids[:, past_length:]
            # 3 - Otherwise (past_length >= input_ids.shape[1]), let's assume input_ids only has unprocessed tokens.
            elif self.config.image_token_index in input_ids:
                input_ids = input_ids[:, input_ids.shape[1] - 1 :]
            # If the cache has seen more tokens than it can hold, then the cache has a size limit. Let's discard the
            # older attention values, as their corresponding values are not part of the input.
            if cache_length < past_length and attention_mask is not None:
                attention_mask = attention_mask[
                    :, -(cache_length + input_ids.shape[1]) :
                ]

        position_ids = kwargs.get("position_ids", None)
        if attention_mask is not None and position_ids is None:
            # create position_ids on the fly for batch generation
            position_ids = attention_mask.long().cumsum(-1) - 1
            position_ids.masked_fill_(attention_mask == 0, 1)
            if past_key_values:
                position_ids = position_ids[:, -input_ids.shape[1] :]

        # if `inputs_embeds` are passed, we only want to use them in the 1st generation step
        if inputs_embeds is not None and past_key_values is None:
            model_inputs = {"inputs_embeds": inputs_embeds}
        else:
            model_inputs = {"input_ids": input_ids}

        model_inputs.update(
            {
                "position_ids": position_ids,
                "past_key_values": past_key_values,
                "use_cache": kwargs.get("use_cache"),
                "attention_mask": attention_mask,
                "pixel_values": pixel_values,
            }
        )
        return model_inputs

    def _reorder_cache(self, *args, **kwargs):
        return self.language_model._reorder_cache(*args, **kwargs)