import torch
from typing import Optional, Union, Tuple,List

import transformers
from transformers.cache_utils import Cache, DynamicCache
from transformers.processing_utils import Unpack
from transformers.modeling_flash_attention_utils import FlashAttentionKwargs
from transformers.models.llama.modeling_llama import BaseModelOutputWithPast

from torch.nn import CrossEntropyLoss
from transformers.models.qwen2_vl.modeling_qwen2_vl import Qwen2VLCausalLMOutputWithPast

from methods.utils.crops_forward_utils import GetAttentionMaskwithFastVandTextMask

def forward(
        self,
        input_ids: torch.LongTensor = None,
        attention_mask: Optional[torch.Tensor] = None,
        position_ids: Optional[torch.LongTensor] = None,
        past_key_values: Optional[Cache] = None,
        inputs_embeds: Optional[torch.FloatTensor] = None,
        use_cache: Optional[bool] = None,
        output_attentions: Optional[bool] = None,
        output_hidden_states: Optional[bool] = None,
        return_dict: Optional[bool] = None,
        cache_position: Optional[torch.LongTensor] = None,
        ## Additional arguments
        key_position: Optional[dict] = None,
        use_fast_v: Optional[bool] = None,
        aggregate_layer_fast_v: Optional[int] = None,
        minumum_fast_v_tokens: Optional[int] = None,
        use_text_mask: Optional[bool] = None,
        aggregate_layer_text_mask: Optional[int] = None,
        minimum_text_tokens: Optional[int] = None,
        **kwargs
    ) -> Union[Tuple, BaseModelOutputWithPast]:
        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
        )
        use_cache = use_cache if use_cache is not None else self.config.use_cache
        return_dict = return_dict if return_dict is not None else self.config.use_return_dict

        if (input_ids is None) ^ (inputs_embeds is not None):
            raise ValueError("You must specify exactly one of input_ids or inputs_embeds")

        if self.gradient_checkpointing and self.training and use_cache:
            use_cache = False

        if inputs_embeds is None:
            inputs_embeds = self.embed_tokens(input_ids)

        if use_cache and past_key_values is None:
            past_key_values = DynamicCache()

        if cache_position is None:
            past_seen_tokens = past_key_values.get_seq_length() if past_key_values is not None else 0
            cache_position = torch.arange(
                past_seen_tokens, past_seen_tokens + inputs_embeds.shape[1], device=inputs_embeds.device
            )

        # the hard coded `3` is for temporal, height and width.
        if position_ids is None:
            position_ids = cache_position.view(1, 1, -1).expand(3, inputs_embeds.shape[0], -1)
        elif position_ids.dim() == 2:
            position_ids = position_ids[None, ...].expand(3, position_ids.shape[0], -1)

        causal_mask = self._update_causal_mask(
            attention_mask, inputs_embeds, cache_position, past_key_values, output_attentions
        )

        hidden_states = inputs_embeds

        # create position embeddings to be shared across the decoder layers
        position_embeddings = self.rotary_emb(hidden_states, position_ids)

        # decoder layers
        all_hidden_states = () if output_hidden_states else None
        all_self_attns = () if output_attentions else None
        next_decoder_cache = None # check whether this is required or not 

        get_attention_mask_with_fast_v_and_text_mask = GetAttentionMaskwithFastVandTextMask(
            attention_mask=attention_mask,
            key_position=key_position,
            use_fast_v=use_fast_v,
            aggregate_layer_fast_v=aggregate_layer_fast_v,
            minumum_fast_v_tokens=minumum_fast_v_tokens,
            use_text_mask=use_text_mask,
            aggregate_layer_text_mask=aggregate_layer_text_mask,
            minimum_text_tokens=minimum_text_tokens,
            **kwargs
        )

        for decoder_layer in self.layers:
            if output_hidden_states:
                all_hidden_states += (hidden_states,)

            if self.gradient_checkpointing and self.training:
                layer_outputs = self._gradient_checkpointing_func(
                    decoder_layer.__call__,
                    hidden_states,
                    causal_mask,
                    position_ids,
                    past_key_values,
                    output_attentions,
                    use_cache,
                    cache_position,
                    position_embeddings,
                )
            else:
                augmented_attention_mask = get_attention_mask_with_fast_v_and_text_mask(
                    all_self_attns=all_self_attns,
                )   

                causal_mask = self._update_causal_mask(
                    augmented_attention_mask, inputs_embeds, cache_position, past_key_values, output_attentions
                )       

                layer_outputs = decoder_layer(
                    hidden_states,
                    attention_mask=causal_mask,
                    position_ids=position_ids,
                    past_key_value=past_key_values,
                    output_attentions=output_attentions,
                    use_cache=use_cache,
                    cache_position=cache_position,
                    position_embeddings=position_embeddings,
                )

            hidden_states = layer_outputs[0]

            if use_cache:
                next_decoder_cache = layer_outputs[2 if output_attentions else 1]

            if output_attentions:
                all_self_attns += (layer_outputs[1],)

        hidden_states = self.norm(hidden_states)

        # add hidden states from the last decoder layer
        if output_hidden_states:
            all_hidden_states += (hidden_states,)

        next_cache = next_decoder_cache if use_cache else None

        if not return_dict:
            return tuple(v for v in [hidden_states, next_cache, all_hidden_states, all_self_attns] if v is not None)
        return BaseModelOutputWithPast(
            last_hidden_state=hidden_states,
            past_key_values=next_cache,
            hidden_states=all_hidden_states,
            attentions=all_self_attns,
        )

def forward_conditional(
        self,
        input_ids: torch.LongTensor = 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,
        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,
        pixel_values: Optional[torch.Tensor] = None,
        pixel_values_videos: Optional[torch.FloatTensor] = None,
        image_grid_thw: Optional[torch.LongTensor] = None,
        video_grid_thw: Optional[torch.LongTensor] = None,
        rope_deltas: Optional[torch.LongTensor] = None,
        cache_position: Optional[torch.LongTensor] = None,
        ## Additional arguments
        key_position: Optional[dict] = None,
        use_fast_v: Optional[bool] = None,
        aggregate_layer_fast_v: Optional[int] = None,
        minumum_fast_v_tokens: Optional[int] = None,
        use_text_mask: Optional[bool] = None,
        aggregate_layer_text_mask: Optional[int] = None,
        minimum_text_tokens: Optional[int] = None,
        **kwargs
    ) -> Union[Tuple, Qwen2VLCausalLMOutputWithPast]:
        r"""
            labels (`torch.LongTensor` of shape `(batch_size, sequence_length)`, *optional*):
                Labels for computing the masked language modeling loss. Indices should either be in `[0, ...,
                config.vocab_size]` or -100 (see `input_ids` docstring). Tokens with indices set to `-100` are ignored
                (masked), the loss is only computed for the tokens with labels in `[0, ..., config.vocab_size]`.

        Returns:

        Example:

        ```python
        >>> from PIL import Image
        >>> import requests
        >>> from transformers import AutoProcessor, Qwen2VLForConditionalGeneration

        >>> model = Qwen2VLForConditionalGeneration.from_pretrained("Qwen/Qwen2-VL-7B-Instruct")
        >>> processor = AutoProcessor.from_pretrained("Qwen/Qwen2-VL-7B-Instruct")

        >>> messages = [
            {
                "role": "user",
                "content": [
                    {"type": "image"},
                    {"type": "text", "text": "What is shown in this image?"},
                ],
            },
        ]
        >>> url = "https://www.ilankelman.org/stopsigns/australia.jpg"
        >>> image = Image.open(requests.get(url, stream=True).raw)

        >>> text = processor.apply_chat_template(messages, tokenize=False, add_generation_prompt=True)
        >>> inputs = processor(text=[text], images=[image], vision_infos=[vision_infos])

        >>> # Generate
        >>> generate_ids = model.generate(inputs.input_ids, max_length=30)
        >>> tokenizer.batch_decode(generate_ids, skip_special_tokens=True, clean_up_tokenization_spaces=False)[0]
        "The image shows a street scene with a red stop sign in the foreground. In the background, there is a large red gate with Chinese characters ..."
        ```"""

        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:
            inputs_embeds = self.model.embed_tokens(input_ids)
            if pixel_values is not None:
                pixel_values = pixel_values.type(self.visual.get_dtype())
                image_embeds = self.visual(pixel_values, grid_thw=image_grid_thw)
                n_image_tokens = (input_ids == self.config.image_token_id).sum().item()
                n_image_features = image_embeds.shape[0]
                if n_image_tokens != n_image_features:
                    raise ValueError(
                        f"Image features and image tokens do not match: tokens: {n_image_tokens}, features {n_image_features}"
                    )
                image_mask = (
                    (input_ids == self.config.image_token_id)
                    .unsqueeze(-1)
                    .expand_as(inputs_embeds)
                    .to(inputs_embeds.device)
                )
                image_embeds = image_embeds.to(inputs_embeds.device, inputs_embeds.dtype)
                inputs_embeds = inputs_embeds.masked_scatter(image_mask, image_embeds)

            if pixel_values_videos is not None:
                pixel_values_videos = pixel_values_videos.type(self.visual.get_dtype())
                video_embeds = self.visual(pixel_values_videos, grid_thw=video_grid_thw)
                n_video_tokens = (input_ids == self.config.video_token_id).sum().item()
                n_video_features = video_embeds.shape[0]
                if n_video_tokens != n_video_features:
                    raise ValueError(
                        f"Video features and video tokens do not match: tokens: {n_video_tokens}, features {n_video_features}"
                    )
                video_mask = (
                    (input_ids == self.config.video_token_id)
                    .unsqueeze(-1)
                    .expand_as(inputs_embeds)
                    .to(inputs_embeds.device)
                )
                video_embeds = video_embeds.to(inputs_embeds.device, inputs_embeds.dtype)
                inputs_embeds = inputs_embeds.masked_scatter(video_mask, video_embeds)

            if attention_mask is not None:
                attention_mask = attention_mask.to(inputs_embeds.device)

        self.rope_deltas = rope_deltas 
        # if we get 4D attention mask we cannot calculate rope deltas anymore. TODO @raushan fixme
        if position_ids is None and (attention_mask is None or attention_mask.ndim == 2):
            # calculate RoPE index once per generation in the pre-fill stage only
            if (
                (cache_position is not None and cache_position[0] == 0)
                or self.rope_deltas is None
                or (past_key_values is None or past_key_values.get_seq_length() == 0)
            ):  
                position_ids, rope_deltas = self.get_rope_index(
                    input_ids, image_grid_thw, video_grid_thw, attention_mask
                )
                self.rope_deltas = rope_deltas
            # then use the prev pre-calculated rope-deltas to get the correct position ids
            else:
                batch_size, seq_length, _ = inputs_embeds.shape
                delta = cache_position[0] + self.rope_deltas if cache_position is not None else 0
                position_ids = torch.arange(seq_length, device=inputs_embeds.device)
                position_ids = position_ids.view(1, -1).expand(batch_size, -1)
                if cache_position is not None:  # otherwise `deltas` is an int `0`
                    delta = delta.repeat_interleave(batch_size // delta.shape[0], dim=0)
                    delta = delta.to(position_ids.device)
                position_ids = position_ids.add(delta)
                position_ids = position_ids.unsqueeze(0).expand(3, -1, -1)

        outputs = self.model(
            input_ids=None,
            position_ids=position_ids,
            attention_mask=attention_mask,
            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,
            cache_position=cache_position,
            key_position=key_position,
            use_fast_v=use_fast_v,
            aggregate_layer_fast_v=aggregate_layer_fast_v,
            minumum_fast_v_tokens=minumum_fast_v_tokens,
            use_text_mask=use_text_mask,
            aggregate_layer_text_mask=aggregate_layer_text_mask,
            minimum_text_tokens=minimum_text_tokens,            
        )

        hidden_states = outputs[0]
        logits = self.lm_head(hidden_states)

        loss = None
        if labels is not None:
            # Upcast to float if we need to compute the loss to avoid potential precision issues
            logits = logits.float()
            # Shift so that tokens < n predict n
            shift_logits = logits[..., :-1, :].contiguous()
            shift_labels = labels[..., 1:].contiguous()
            # Flatten the tokens
            loss_fct = CrossEntropyLoss()
            shift_logits = shift_logits.view(-1, self.config.vocab_size)
            shift_labels = shift_labels.view(-1)
            # Enable model parallelism
            shift_labels = shift_labels.to(shift_logits.device)
            loss = loss_fct(shift_logits, shift_labels)

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

        return Qwen2VLCausalLMOutputWithPast(
            loss=loss,
            logits=logits,
            past_key_values=outputs.past_key_values,
            hidden_states=outputs.hidden_states,
            attentions=outputs.attentions,
            rope_deltas=self.rope_deltas,
        )

def patch_qwen_forward():
    transformers.models.qwen2_vl.modeling_qwen2_vl.Qwen2VLModel.forward = forward
    transformers.models.qwen2_vl.modeling_qwen2_vl.Qwen2VLForConditionalGeneration.forward = forward_conditional
    