from dataclasses import dataclass, fields
from itertools import tee
from typing import Iterable, List, Mapping, Optional, Tuple, Union

import torch
import torch.nn as nn
import torch.nn.functional as F
from mistral_common.protocol.instruct.messages import ImageChunk
from PIL import Image
from transformers import PretrainedConfig
from xformers.ops.fmha import memory_efficient_attention
from xformers.ops.fmha.attn_bias import BlockDiagonalMask

from vllm.attention import AttentionMetadata
from vllm.config import CacheConfig, MultiModalConfig
from vllm.inputs import INPUT_REGISTRY, InputContext, LLMInputs
from vllm.model_executor.layers.layernorm import RMSNorm
from vllm.model_executor.layers.quantization import QuantizationConfig
from vllm.model_executor.layers.sampler import SamplerOutput
from vllm.model_executor.model_loader.weight_utils import default_weight_loader
from vllm.model_executor.models.utils import merge_multimodal_embeddings
from vllm.model_executor.sampling_metadata import SamplingMetadata
from vllm.multimodal import MULTIMODAL_REGISTRY
from vllm.multimodal.base import MultiModalInputs
from vllm.multimodal.utils import cached_get_tokenizer
from vllm.sequence import IntermediateTensors, SequenceData

from .interfaces import SupportsMultiModal
from .utils import init_vllm_registered_model


def get_max_pixtral_image_tokens(ctx: InputContext):
    tokenizer = cached_get_tokenizer(
        ctx.model_config.tokenizer,
        tokenizer_mode=ctx.model_config.tokenizer_mode)
    mm_encoder = tokenizer.instruct.mm_encoder

    max_image_size = mm_encoder.mm_config.max_image_size
    image_patch_size = mm_encoder.mm_config.image_patch_size

    return ((max_image_size // image_patch_size)**2)


def dummy_data_for_pixtral(ctx: InputContext, seq_len: int,
                           mm_counts: Mapping[str, int]):
    tokenizer = cached_get_tokenizer(
        ctx.model_config.tokenizer,
        tokenizer_mode=ctx.model_config.tokenizer_mode)

    mm_encoder = tokenizer.mistral.instruct_tokenizer.mm_encoder
    patch_size = mm_encoder.mm_config.image_patch_size
    image_token_id = mm_encoder.special_ids.img

    mm_config = ctx.model_config.multimodal_config
    num_images = mm_config.limit_per_prompt.get("image", 1)

    # dummy size
    size = 256
    image = Image.new("RGB", (size, size), color=0)

    image_feature_size = (size**2) // (patch_size**2)

    num_image_tokens = image_feature_size * num_images
    seq_data = SequenceData.from_token_counts(
        (image_token_id, num_image_tokens),
        (0, seq_len - num_image_tokens),
    )

    mm_data = {"image": num_images * [image]}
    return seq_data, mm_data


def input_mapper_for_pixtral(ctx: InputContext,
                             data: object) -> MultiModalInputs:
    """Maps the input data to its MultiModalInputs (if any).

    Args:
        ctx: Context of the loaded model.
        data: data potentially containing image/image embeddings to be mapped
            to pixel_values in .forward() for a visual QWenLMHeadModel model.

    Returns:
        MultiModalInputs containing the stacked normalized images tensor or
        image embeddings.
    """
    # Early exit if we have provided an image to a language only Qwen model
    model_config = ctx.model_config
    tokenizer = cached_get_tokenizer(
        model_config.tokenizer, tokenizer_mode=model_config.tokenizer_mode)

    data_list = data if isinstance(data, list) else [data]

    images = []
    for image_data in data_list:
        image = ImageChunk(image=image_data)
        encoding = tokenizer.instruct.mm_encoder(image)
        image = torch.from_numpy(encoding.image).to(device="cuda",
                                                    dtype=torch.float16)
        images.append(image)

    return MultiModalInputs({"images": images})


def input_processor_for_pixtral(ctx: InputContext, llm_inputs: LLMInputs):
    multi_modal_data = llm_inputs.get("multi_modal_data")
    if multi_modal_data is not None and "image" in multi_modal_data:
        tokenizer = cached_get_tokenizer(
            ctx.model_config.tokenizer,
            tokenizer_mode=ctx.model_config.tokenizer_mode)

        mm_encoder = tokenizer.mistral.instruct_tokenizer.mm_encoder
        image_token_id = mm_encoder.special_ids.img

        if image_token_id not in llm_inputs['prompt_token_ids']:
            raise ValueError(
                (f"You've passed {llm_inputs=} without {image_token_id=}"
                 " Make sure to process your input via mistral_common's"
                 " tokenizer or pass a chat completion request. For more"
                 " For more info, see: "
                 "https://github.com/vllm-project/vllm/issues/8411."))

    return llm_inputs


@MULTIMODAL_REGISTRY.register_image_input_mapper(input_mapper_for_pixtral)
@MULTIMODAL_REGISTRY.register_max_image_tokens(get_max_pixtral_image_tokens)
@INPUT_REGISTRY.register_dummy_data(dummy_data_for_pixtral)
@INPUT_REGISTRY.register_input_processor(input_processor_for_pixtral)
class PixtralForConditionalGeneration(nn.Module, SupportsMultiModal):

    def __init__(self,
                 config: PretrainedConfig,
                 multimodal_config: MultiModalConfig,
                 cache_config: Optional[CacheConfig] = None,
                 quant_config: Optional[QuantizationConfig] = None) -> None:
        super().__init__()

        self.config = config
        self.multimodal_config = multimodal_config

        dataclass_fields = {field.name for field in fields(VisionEncoderArgs)}
        vision_args = {
            key: value
            for key, value in self.config.vision_config.to_dict().items()
            if key in dataclass_fields
        }

        self.vision_args = VisionEncoderArgs(**vision_args)

        # init MistralForCausalLM
        self.language_model = init_vllm_registered_model(
            config.text_config, cache_config, quant_config)

        self.vision_encoder = VisionTransformer(self.vision_args)
        self.vision_language_adapter = VisionLanguageAdapter(
            self.vision_args, dim=config.text_config.hidden_size)

    def forward(
        self,
        input_ids: torch.Tensor,
        positions: torch.Tensor,
        kv_caches: List[torch.Tensor],
        attn_metadata: AttentionMetadata,
        intermediate_tensors: Optional[IntermediateTensors] = None,
        **kwargs: object,
    ) -> SamplerOutput:
        """Run forward pass for pixtral.

        TODO

        """
        image_input = self._parse_and_validate_image_input(**kwargs)

        if image_input is not None:
            vision_embeddings = self._process_image_input(image_input)
            inputs_embeds = self.language_model.model.get_input_embeddings(
                input_ids)

            inputs_embeds = merge_multimodal_embeddings(
                input_ids, inputs_embeds, vision_embeddings,
                self.vision_args.image_token_id)

            input_ids = None
        else:
            inputs_embeds = None

        hidden_states = self.language_model.model(input_ids,
                                                  positions,
                                                  kv_caches,
                                                  attn_metadata,
                                                  None,
                                                  inputs_embeds=inputs_embeds)

        return hidden_states

    def _parse_and_validate_image_input(
        self,
        images: Optional[Union[List[List[torch.Tensor]], List[torch.Tensor],
                               torch.Tensor]] = None
    ) -> Optional[List[torch.Tensor]]:
        if images is None:
            return None

        if isinstance(images, torch.Tensor):
            # if passed as batch take all images
            N, B, C, W, H = images.shape
            images = images.reshape(N * B, C, W, H)
            images = [images[i] for i in range(images.size(0))]
        elif isinstance(images, list):
            # if passed as list flatten lists of tensors
            flatten_images = []
            for imgs_per_req in images:
                imgs_per_req = [
                    imgs_per_req[i] for i in range(imgs_per_req.size(0))
                ] if isinstance(imgs_per_req, torch.Tensor) else imgs_per_req

                flatten_images.extend(imgs_per_req)

            images = flatten_images

        return images

    def _process_image_input(self,
                             image_input: List[torch.Tensor]) -> torch.Tensor:
        return self.vision_language_adapter(self.vision_encoder(image_input))

    def compute_logits(
        self,
        hidden_states: torch.Tensor,
        sampling_metadata: SamplingMetadata,
    ) -> Optional[torch.Tensor]:
        return self.language_model.compute_logits(hidden_states,
                                                  sampling_metadata)

    def sample(
        self,
        logits: torch.Tensor,
        sampling_metadata: SamplingMetadata,
    ) -> Optional[SamplerOutput]:
        return self.language_model.sample(logits, sampling_metadata)

    def load_weights(self, weights: Iterable[Tuple[str, torch.Tensor]]):

        def is_vision_encoder_weights(weight: Tuple[str, torch.Tensor]):
            return weight[0].startswith("vision_encoder")

        def is_vision_lang_adapter_weights(weight: Tuple[str, torch.Tensor]):
            return weight[0].startswith("vision_language_adapter")

        def is_vision_weights(weight: Tuple[str, torch.Tensor]):
            return is_vision_encoder_weights(
                weight) or is_vision_lang_adapter_weights(weight)

        llm_weights, vision_encoder_weights, vision_lang_adapter_weights = tee(
            weights, 3)

        # llm
        llm_weights = filter(lambda x: not is_vision_weights(x), llm_weights)
        self.language_model.load_weights(llm_weights)

        # vision encoder
        vision_encoder_weights = filter(is_vision_encoder_weights,
                                        vision_encoder_weights)
        vision_encoder_dict = dict(self.vision_encoder.named_parameters())
        for name, loaded_weight in vision_encoder_weights:
            # cut 'vision_encoder.'
            name = '.'.join(name.split(".")[1:])
            param = vision_encoder_dict[name]

            default_weight_loader(param, loaded_weight)

        # adapter
        vision_lang_adapter_weights = filter(is_vision_lang_adapter_weights,
                                             vision_lang_adapter_weights)
        vision_lang_adpter_dict = dict(
            self.vision_language_adapter.named_parameters())
        for name, loaded_weight in vision_lang_adapter_weights:
            # cut 'vision_language_adapter.'
            name = '.'.join(name.split(".")[1:])
            param = vision_lang_adpter_dict[name]
            default_weight_loader(param, loaded_weight)


# Vision encoder
@dataclass
class VisionEncoderArgs:
    hidden_size: int
    num_channels: int
    image_size: int
    patch_size: int
    intermediate_size: int
    num_hidden_layers: int
    num_attention_heads: int
    rope_theta: float  # for rope-2D
    image_token_id: int


def _reshape_for_broadcast(freqs_cis: torch.Tensor,
                           x: torch.Tensor) -> torch.Tensor:
    """
    freqs_cis: complex - (seq_len, head_dim / 2)
    x: complex - (bsz, seq_len, head_dim / 2)
    """
    ndim = x.ndim
    assert ndim > 1
    assert freqs_cis.shape == (x.shape[1], x.shape[-1]), (
        freqs_cis.shape,
        (x.shape[1], x.shape[-1]),
    )
    shape = [
        d if i == 1 or i == ndim - 1 else 1 for i, d in enumerate(x.shape)
    ]
    return freqs_cis.view(*shape)


def precompute_freqs_cis_2d(
    dim: int,
    height: int,
    width: int,
    theta: float,
) -> torch.Tensor:
    """
    freqs_cis: 2D complex tensor of shape (height, width, dim // 2)
        to be indexed by (height, width) position tuples
    """
    # (dim / 2) frequency bases
    freqs = 1.0 / (theta**(torch.arange(0, dim, 2).float() / dim))

    h = torch.arange(height, device=freqs.device)
    w = torch.arange(width, device=freqs.device)

    freqs_h = torch.outer(h, freqs[::2]).float()
    freqs_w = torch.outer(w, freqs[1::2]).float()
    freqs_2d = torch.cat(
        [
            freqs_h[:, None, :].repeat(1, width, 1),
            freqs_w[None, :, :].repeat(height, 1, 1),
        ],
        dim=-1,
    )
    return torch.polar(torch.ones_like(freqs_2d), freqs_2d)


def apply_rotary_emb_vit(
    xq: torch.Tensor,
    xk: torch.Tensor,
    freqs_cis: torch.Tensor,
) -> Tuple[torch.Tensor, torch.Tensor]:
    xq_ = torch.view_as_complex(xq.float().reshape(*xq.shape[:-1], -1, 2))
    xk_ = torch.view_as_complex(xk.float().reshape(*xk.shape[:-1], -1, 2))
    assert freqs_cis.dtype == torch.complex64
    freqs_cis = _reshape_for_broadcast(freqs_cis, xq_)
    xq_out = torch.view_as_real(xq_ * freqs_cis).flatten(3)
    xk_out = torch.view_as_real(xk_ * freqs_cis).flatten(3)
    return xq_out.type_as(xq), xk_out.type_as(xk)


class FeedForward(nn.Module):

    def __init__(self, args: VisionEncoderArgs):
        super().__init__()
        assert args.intermediate_size is not None
        self.w1 = nn.Linear(args.hidden_size,
                            args.intermediate_size,
                            bias=False)
        self.w2 = nn.Linear(args.intermediate_size,
                            args.hidden_size,
                            bias=False)
        self.w3 = nn.Linear(args.hidden_size,
                            args.intermediate_size,
                            bias=False)

    def forward(self, x: torch.Tensor) -> torch.Tensor:
        return self.w2(F.silu(self.w1(x)) * self.w3(x))


class Attention(nn.Module):

    def __init__(self, args: VisionEncoderArgs):
        super().__init__()
        self.args = args
        assert not args.hidden_size % args.num_attention_heads
        self.n_heads = args.num_attention_heads
        self.head_dim = args.hidden_size // args.num_attention_heads

        self.wq = nn.Linear(args.hidden_size, args.hidden_size, bias=False)
        self.wk = nn.Linear(args.hidden_size, args.hidden_size, bias=False)
        self.wv = nn.Linear(args.hidden_size, args.hidden_size, bias=False)
        self.wo = nn.Linear(args.hidden_size, args.hidden_size, bias=False)

    def forward(
        self,
        x: torch.Tensor,
        mask: BlockDiagonalMask,
        freqs_cis: torch.Tensor,
    ) -> torch.Tensor:
        batch, patches, _ = x.shape

        q, k, v = self.wq(x), self.wk(x), self.wv(x)
        q = q.reshape(batch, patches, self.n_heads, self.head_dim)
        k = k.reshape(batch, patches, self.n_heads, self.head_dim)
        v = v.reshape(batch, patches, self.n_heads, self.head_dim)

        q, k = apply_rotary_emb_vit(q, k, freqs_cis=freqs_cis)
        out = memory_efficient_attention(q, k, v, attn_bias=mask)
        out = out.reshape(batch, patches, self.n_heads * self.head_dim)
        return self.wo(out)


class TransformerBlock(nn.Module):

    def __init__(self, args: VisionEncoderArgs):
        super().__init__()
        self.attention = Attention(args)
        self.feed_forward = FeedForward(args)
        self.attention_norm = RMSNorm(args.hidden_size, eps=1e-5)
        self.ffn_norm = RMSNorm(args.hidden_size, eps=1e-5)

    def forward(
        self,
        x: torch.Tensor,
        mask: BlockDiagonalMask,
        freqs_cis: torch.Tensor,
    ) -> torch.Tensor:
        r = self.attention.forward(self.attention_norm(x),
                                   mask=mask,
                                   freqs_cis=freqs_cis)
        h = x + r
        r = self.feed_forward.forward(self.ffn_norm(h))
        out = h + r
        return out


class Transformer(nn.Module):

    def __init__(self, args: VisionEncoderArgs):
        super().__init__()
        self.layers = torch.nn.ModuleList()
        for _ in range(args.num_hidden_layers):
            self.layers.append(TransformerBlock(args))

    def forward(
        self,
        x: torch.Tensor,
        mask: BlockDiagonalMask,
        freqs_cis: Optional[torch.Tensor],
    ) -> torch.Tensor:
        for layer in self.layers:
            x = layer(x, mask=mask, freqs_cis=freqs_cis)
        return x


def position_meshgrid(patch_embeds_list: List[torch.Tensor], ) -> torch.Tensor:
    positions = torch.cat([
        torch.stack(
            torch.meshgrid(
                torch.arange(p.shape[-2]),
                torch.arange(p.shape[-1]),
                indexing="ij",
            ),
            dim=-1,
        ).reshape(-1, 2) for p in patch_embeds_list
    ])
    return positions


class VisionTransformer(nn.Module):

    def __init__(self, args: VisionEncoderArgs):
        super().__init__()
        self.args = args
        self.patch_conv = nn.Conv2d(
            in_channels=args.num_channels,
            out_channels=args.hidden_size,
            kernel_size=args.patch_size,
            stride=args.patch_size,
            bias=False,
        )
        self.ln_pre = RMSNorm(args.hidden_size, eps=1e-5)
        self.transformer = Transformer(args)

        head_dim = self.args.hidden_size // self.args.num_attention_heads
        assert head_dim % 2 == 0, "ROPE requires even head_dim"
        self._freqs_cis: Optional[torch.Tensor] = None

    @property
    def max_patches_per_side(self) -> int:
        return self.args.image_size // self.args.patch_size

    @property
    def device(self) -> torch.device:
        return next(self.parameters()).device

    @property
    def dtype(self) -> torch.device:
        return next(self.parameters()).dtype

    @property
    def freqs_cis(self) -> torch.Tensor:
        if self._freqs_cis is None:
            self._freqs_cis = precompute_freqs_cis_2d(
                dim=self.args.hidden_size // self.args.num_attention_heads,
                height=self.max_patches_per_side,
                width=self.max_patches_per_side,
                theta=self.args.rope_theta,
            )

        if self._freqs_cis.device != self.device:
            self._freqs_cis = self._freqs_cis.to(device=self.device)

        return self._freqs_cis

    def forward(
        self,
        images: List[torch.Tensor],
    ) -> torch.Tensor:
        """
        Args:
            images: list of N_img images of variable sizes, 
                each of shape (C, H, W)
        Returns:
            image_features: tensor of token features for 
                all tokens of all images of shape (N_toks, D)
        """
        # pass images through initial convolution independently
        patch_embeds_list = [
            self.patch_conv(img.unsqueeze(0).to(self.dtype)) for img in images
        ]

        # flatten to a single sequence
        patch_embeds = torch.cat(
            [p.flatten(2).permute(0, 2, 1) for p in patch_embeds_list], dim=1)
        patch_embeds = self.ln_pre(patch_embeds)

        # positional embeddings
        positions = position_meshgrid(patch_embeds_list).to(self.device)
        freqs_cis = self.freqs_cis[positions[:, 0], positions[:, 1]]

        # pass through Transformer with a block diagonal mask delimiting images
        mask = BlockDiagonalMask.from_seqlens(
            [p.shape[-2] * p.shape[-1] for p in patch_embeds_list], )
        out = self.transformer(patch_embeds, mask=mask, freqs_cis=freqs_cis)

        # remove batch dimension of the single sequence
        return out.squeeze(0)


class VisionLanguageAdapter(nn.Module):

    def __init__(self, args: VisionEncoderArgs, dim: int):
        super().__init__()
        assert isinstance(args, VisionEncoderArgs)
        self.w_in = nn.Linear(
            args.hidden_size,
            dim,
            bias=True,
        )
        self.gelu = nn.GELU()
        self.w_out = nn.Linear(dim, dim, bias=True)

    def forward(self, x: torch.Tensor) -> torch.Tensor:
        return self.w_out(self.gelu(self.w_in(x)))
