import copy
import math
from functools import lru_cache
from typing import Optional

import einops
import torch
from einops import rearrange
from huggingface_hub import hf_hub_download
from safetensors import safe_open
from torch import nn
from transformers.models.dinov3_vit.configuration_dinov3_vit import DINOv3ViTConfig

from src.model.attention import CrossAttention, PlainAttention, RoPE
from src.model.dino import (
    DINOv3ViTAttention,
    DINOv3ViTDropPath,
    DINOv3ViTEmbeddings,
    DINOv3ViTGatedMLP,
    DINOv3ViTLayer,
    DINOv3ViTLayerScale,
    DINOv3ViTMLP,
    DINOv3ViTRopePositionEmbedding,
)
from src.model.dit import modulate
from src.model.resnet import ResBlock


def create_coordinate(h, w, start=0, end=1, device="cuda:1", dtype=torch.float32):
    # Create a grid of coordinates
    x = torch.linspace(start, end, h, device=device, dtype=dtype)
    y = torch.linspace(start, end, w, device=device, dtype=dtype)
    # Create a 2D map using meshgrid
    xx, yy = torch.meshgrid(x, y, indexing="ij")
    # Stack the x and y coordinates to create the final map
    coord_map = torch.stack([xx, yy], dim=-1)[None, ...]
    coords = rearrange(coord_map, "b h w c -> b (h w) c", h=h, w=w)
    return coords


class TimestepEmbedder(nn.Module):
    def __init__(self, hidden_size: int, frequency_embedding_size: int = 256):
        super().__init__()
        self.mlp = nn.Sequential(
            nn.Linear(frequency_embedding_size, hidden_size),
            nn.SiLU(),
            nn.Linear(hidden_size, hidden_size),
        )
        self.frequency_embedding_size = frequency_embedding_size

    @staticmethod
    def timestep_embedding(t, dim, max_period=10000):
        half = dim // 2
        freqs = torch.exp(
            -math.log(max_period) * torch.arange(start=0, end=half) / half
        ).to(t.device)
        args = t[:, None] * freqs[None]
        embedding = torch.cat([torch.cos(args), torch.sin(args)], dim=-1)
        if dim % 2:
            embedding = torch.cat(
                [embedding, torch.zeros_like(embedding[:, :1])], dim=-1
            )
        return embedding

    def forward(self, t):
        t_freq = self.timestep_embedding(t, self.frequency_embedding_size).to(
            dtype=next(self.parameters()).dtype
        )
        t_emb = self.mlp(t_freq)
        return t_emb


class LabelEmbedder(nn.Module):
    def __init__(self, num_classes, hidden_size, dropout_prob):
        super().__init__()
        use_cfg_embedding = int(dropout_prob > 0)
        self.embedding_table = nn.Embedding(
            num_classes + use_cfg_embedding, hidden_size
        )
        self.num_classes = num_classes
        self.dropout_prob = dropout_prob

    def token_drop(self, labels, force_drop_ids=None):
        if force_drop_ids is None:
            drop_ids = torch.rand(labels.shape[0]) < self.dropout_prob
            drop_ids = drop_ids.cuda()
            drop_ids = drop_ids.to(labels.device)
        else:
            drop_ids = force_drop_ids == 1
        labels = torch.where(drop_ids, self.num_classes, labels)
        return labels

    def forward(self, labels, train, force_drop_ids=None):
        use_dropout = self.dropout_prob > 0
        if (train and use_dropout) or (force_drop_ids is not None):
            labels = self.token_drop(labels, force_drop_ids)
        embeddings = self.embedding_table(labels)
        return embeddings


class DinoEncoderLayer(DINOv3ViTLayer):
    def __init__(self, config: DINOv3ViTConfig):
        super().__init__(config)

        self.norm_cond = nn.LayerNorm(config.hidden_size, eps=config.layer_norm_eps)
        self.cond = DINOv3ViTAttention(config)
        self.layer_scale_cond = DINOv3ViTLayerScale(config)

        nn.init.constant_(self.layer_scale_cond.lambda1, 0)
        self.norm1.requires_grad_(False)
        self.norm2.requires_grad_(False)
        self.attention.requires_grad_(False)
        self.mlp.requires_grad_(False)
        self.layer_scale1.requires_grad_(False)
        self.layer_scale2.requires_grad_(False)

    def forward(
        self,
        hidden_states: torch.Tensor,
        *,
        conditioning_input: Optional[torch.Tensor] = None,
        attention_mask: Optional[torch.Tensor] = None,
        position_embeddings: Optional[tuple[torch.Tensor, torch.Tensor]] = None,
        **kwargs,
    ) -> torch.Tensor:
        assert position_embeddings is not None

        hidden_states = (
            self.drop_path(
                self.layer_scale1(
                    self.attention(
                        self.norm1(hidden_states),
                        attention_mask=attention_mask,
                        position_embeddings=position_embeddings,
                    )
                )
            )
            + hidden_states
        )

        hidden_states = (
            self.drop_path(
                self.layer_scale_cond(
                    self.cond(
                        hidden_states,
                        self.norm_cond(conditioning_input),
                    )
                )
            )
            + hidden_states
        )

        hidden_states = (
            self.drop_path(self.layer_scale2(self.mlp(self.norm2(hidden_states))))
            + hidden_states
        )

        return hidden_states


class DinoDecoderLayer(DINOv3ViTLayer):
    def __init__(self, config: DINOv3ViTConfig, depth: int):
        super().__init__(config)

        hidden_size = config.hidden_size // (4**depth)
        hacky_config = copy.copy(config)
        hacky_config.hidden_size = hidden_size
        hacky_config.intermediate_size = hacky_config.intermediate_size // (3**depth)

        self.norm1 = nn.LayerNorm(hidden_size, eps=config.layer_norm_eps)
        self.attention = PlainAttention(
            hidden_size, config.num_attention_heads // (2**depth)
        )  # head scaling law?
        self.layer_scale1 = DINOv3ViTLayerScale(hacky_config)
        self.drop_path = (
            DINOv3ViTDropPath(hacky_config.drop_path_rate)
            if hacky_config.drop_path_rate > 0.0
            else nn.Identity()
        )

        self.norm2 = nn.LayerNorm(hidden_size, eps=hacky_config.layer_norm_eps)

        if config.use_gated_mlp:
            self.mlp = DINOv3ViTGatedMLP(hacky_config)
        else:
            self.mlp = DINOv3ViTMLP(hacky_config)
        self.layer_scale2 = DINOv3ViTLayerScale(hacky_config)

        # adaln
        self.adaln = nn.Sequential(
            nn.SiLU(),
            nn.Linear(config.hidden_size, 6 * hidden_size, bias=True),
        )

    def forward(
        self,
        hidden_states: torch.Tensor,
        *,
        conditioning_input: Optional[torch.Tensor] = None,
        attention_mask: Optional[torch.Tensor] = None,
        position_embeddings: Optional[tuple[torch.Tensor, torch.Tensor]] = None,
        **kwargs,
    ) -> torch.Tensor:
        conditioning_input = conditioning_input.squeeze(1)  # type: ignore
        shift_msa, scale_msa, gate_msa, shift_mlp, scale_mlp, gate_mlp = self.adaln(
            conditioning_input
        ).chunk(6, dim=-1)

        hidden_states = (
            self.drop_path(
                gate_msa.unsqueeze(1)
                * self.layer_scale1(
                    self.attention(
                        modulate(self.norm1(hidden_states), shift_msa, scale_msa),
                        position_embeddings=position_embeddings,
                    )
                )
            )
            + hidden_states
        )

        hidden_states = (
            self.drop_path(
                gate_mlp.unsqueeze(1)
                * self.layer_scale2(
                    self.mlp(modulate(self.norm2(hidden_states), shift_mlp, scale_mlp))
                )
            )
            + hidden_states
        )

        return hidden_states


class ResidualUpscaler(nn.Module):
    def __init__(
        self, config: DINOv3ViTConfig, depth: list[int], bottleneck_dim: int = 128
    ):  # max depth 2 (2**2 = 16 = patch size)
        super().__init__()

        def build_encoder(in_dim, num_layers=2):
            return nn.Sequential(
                nn.Conv2d(
                    in_dim,
                    bottleneck_dim,
                    kernel_size=1,
                    padding=0,
                    padding_mode="reflect",
                    bias=False,
                ),
                *[
                    ResBlock(
                        bottleneck_dim,
                        bottleneck_dim,
                        kernel_size=1,
                        num_groups=8,
                        pad_mode="reflect",
                        norm_fn=nn.GroupNorm,
                        activation_fn=nn.SiLU,
                        use_conv_shortcut=False,
                    )
                    for _ in range(num_layers)
                ],
            )

        self.config = config
        self.depth = depth
        self.global_encode = nn.Linear(
            config.hidden_size * len(depth),
            bottleneck_dim * 2,
        )
        self.local_encode = nn.ModuleList(
            [
                nn.Linear(config.hidden_size, bottleneck_dim * 2)
                if d != 0
                else nn.Identity()
                for d in depth
            ]
        )
        self.q_norm = nn.ModuleList(
            [nn.LayerNorm(bottleneck_dim) if d != 0 else nn.Identity() for d in depth]
        )
        self.k_norm = nn.ModuleList(
            [nn.LayerNorm(bottleneck_dim) if d != 0 else nn.Identity() for d in depth]
        )
        self.v_downsample = nn.ModuleList(
            [
                nn.Linear(config.hidden_size, config.hidden_size // (4**d))
                if d != 0
                else nn.Identity()
                for d in depth
            ]
        )
        self.cross_attn = nn.ModuleList(
            [
                CrossAttention(
                    bottleneck_dim,
                    bottleneck_dim,
                    config.hidden_size // (4**d),
                )
                if d != 0
                else nn.Identity()
                for d in depth
            ]
        )

        self.image_encoder = build_encoder(3)
        self.q_encoder = build_encoder(bottleneck_dim)
        self.k_encoder = build_encoder(bottleneck_dim)

        self.rope = RoPE(bottleneck_dim)

        # ok just shuffle it; no dont
        # self.pixel_shuffle = [nn.PixelShuffle(2), nn.PixelShuffle(4)]

    def forward(self, pixel_values: torch.Tensor, residuals: list[torch.Tensor]):
        # residual[0] => deepest, -1 => shallowest; pixel values (b, 3, h, w) / residuals [(b, 1 + self.config.num_register_tokens + seq, d), (b, 1 + self.config.num_register_tokens + seq, d)]
        # objective: say we have (1024, 1024, 512) residual. we want to make multi head attention query well
        assert self.config.patch_size is not None

        image_h, image_w = pixel_values.shape[-2], pixel_values.shape[-1]

        rest = [
            residual[:, : 1 + self.config.num_register_tokens] for residual in residuals
        ]
        residuals = [
            residual[:, 1 + self.config.num_register_tokens :] for residual in residuals
        ]

        global_shift, global_scale = self.global_encode(
            einops.rearrange(
                torch.stack(residuals, dim=1), "b depth s h -> b s (depth h)"
            )
        ).chunk(2, dim=-1)  # patch-level global btw

        image_residual = self.image_encoder(pixel_values)  # messy; todo: cleanup
        coords = create_coordinate(pixel_values.shape[-2], pixel_values.shape[-1])
        image_residual = rearrange(image_residual, "b c h w -> b (h w) c")
        image_residual = self.rope(image_residual, coords)
        image_residual = rearrange(
            image_residual, "b (h w) c -> b c h w", h=pixel_values.shape[-2]
        )
        q = self.q_encoder(image_residual)
        k = self.k_encoder(image_residual)

        reformed_residual = []
        for i, (depth, residual, rest) in enumerate(zip(self.depth, residuals, rest)):
            if depth == 0:
                reformed_residual.append(torch.cat((rest, residual), dim=1))
                continue

            local_shift, local_scale = self.local_encode[i](residual).chunk(2, dim=-1)
            local_q = self.q_norm[i](
                einops.rearrange(
                    torch.nn.functional.adaptive_avg_pool2d(
                        q,
                        output_size=(
                            image_h // self.config.patch_size * (2**depth),
                            image_w // self.config.patch_size * (2**depth),
                        ),
                    ),
                    "b c h w -> b (h w) c",
                )
            )
            local_k = (1 + local_scale) * (
                (1 + global_scale)
                * self.k_norm[i](
                    einops.rearrange(
                        torch.nn.functional.adaptive_avg_pool2d(
                            k,
                            output_size=(
                                image_h // self.config.patch_size,
                                image_w // self.config.patch_size,
                            ),
                        ),
                        "b c h w -> b (h w) c",
                    )
                )
                + global_shift
            ) + local_shift
            local_v = self.v_downsample[i](residual)

            local_rest = self.v_downsample[i](rest)

            final_residual = torch.concat(
                (local_rest, self.cross_attn[i](local_q, local_k, local_v)), dim=1
            )

            reformed_residual.append(final_residual)

        return reformed_residual


class DinoV3ViTDecoder(nn.Module):
    def __init__(self, config: DINOv3ViTConfig):
        super().__init__()
        self.config = config
        self.num_channels_out = config.num_channels
        self.patch_size = config.patch_size

        self.projection = nn.Linear(
            config.hidden_size // 16, config.num_channels * 16, bias=True
        )
        self.upscale = nn.PixelShuffle(4)

        nn.init.zeros_(self.projection.weight)
        nn.init.zeros_(
            self.projection.bias
        ) if self.projection.bias is not None else None

    def forward(self, x: torch.Tensor, image_size: tuple[int, int]) -> torch.Tensor:
        return self.upscale(
            self.projection(
                einops.rearrange(
                    x,
                    "b (h w) d -> b h w d",
                    h=image_size[0] // 4,
                    w=image_size[1] // 4,
                )
            ).permute(0, 3, 1, 2)
        )


class NerfEmbedder(nn.Module):
    def __init__(self, in_channels, hidden_size_input, max_freqs):
        super().__init__()
        self.max_freqs = max_freqs
        self.hidden_size_input = hidden_size_input
        self.embedder = nn.Sequential(
            nn.Linear(in_channels + max_freqs**2, hidden_size_input, bias=True),
        )

    @lru_cache
    def fetch_pos(self, patch_size, device, dtype):
        pos_x = torch.linspace(0, 1, patch_size, device=device, dtype=dtype)
        pos_y = torch.linspace(0, 1, patch_size, device=device, dtype=dtype)
        pos_y, pos_x = torch.meshgrid(pos_y, pos_x, indexing="ij")
        pos_x = pos_x.reshape(-1, 1, 1)
        pos_y = pos_y.reshape(-1, 1, 1)

        freqs = torch.linspace(
            0, self.max_freqs, self.max_freqs, dtype=dtype, device=device
        )
        freqs_x = freqs[None, :, None]
        freqs_y = freqs[None, None, :]
        coeffs = (1 + freqs_x * freqs_y) ** -1
        dct_x = torch.cos(pos_x * freqs_x * torch.pi)
        dct_y = torch.cos(pos_y * freqs_y * torch.pi)
        dct = (dct_x * dct_y * coeffs).view(1, -1, self.max_freqs**2)
        return dct

    def forward(self, inputs):
        target_dtype = self.embedder[0].weight.dtype
        inputs = inputs.to(dtype=target_dtype)
        B, P2, C = inputs.shape
        patch_size = int(P2**0.5)
        device = inputs.device
        dtype = inputs.dtype
        dct = self.fetch_pos(patch_size, device, dtype)
        dct = dct.repeat(B, 1, 1)
        inputs = torch.cat([inputs, dct], dim=-1)
        inputs = self.embedder(inputs)
        return inputs


class NerfBlock(nn.Module):
    def __init__(self, hidden_size_s: int, hidden_size_x: int, mlp_ratio: int = 4):
        super().__init__()
        self.param_generator1 = nn.Sequential(
            nn.Linear(hidden_size_s, 2 * hidden_size_x**2 * mlp_ratio, bias=True),
        )
        self.norm = nn.RMSNorm(hidden_size_x, eps=1e-6)
        self.mlp_ratio = mlp_ratio

    def forward(self, x, s):
        batch_size, num_x, hidden_size_x = x.shape
        mlp_params1 = self.param_generator1(s)
        fc1_param1, fc2_param1 = mlp_params1.chunk(2, dim=-1)
        fc1_param1 = fc1_param1.view(
            batch_size, hidden_size_x, hidden_size_x * self.mlp_ratio
        )
        fc2_param1 = fc2_param1.view(
            batch_size, hidden_size_x * self.mlp_ratio, hidden_size_x
        )

        # normalize fc1
        normalized_fc1_param1 = torch.nn.functional.normalize(fc1_param1, dim=-2)
        # normalize fc2
        normalized_fc2_param1 = torch.nn.functional.normalize(fc2_param1, dim=-2)
        # mlp 1
        res_x = x
        x = self.norm(x)
        x = torch.bmm(x, normalized_fc1_param1)
        x = torch.nn.functional.silu(x)
        x = torch.bmm(x, normalized_fc2_param1)
        x = x + res_x
        return x


class NerfFinalLayer(nn.Module):
    def __init__(self, hidden_size, out_channels):
        super().__init__()
        self.norm = nn.RMSNorm(hidden_size, eps=1e-6)
        self.linear = nn.Linear(hidden_size, out_channels, bias=True)

    def forward(self, x):
        x = self.norm(x)
        x = self.linear(x)
        return x


class UTransformer(nn.Module):
    def __init__(
        self,
        config: DINOv3ViTConfig,
        num_classes: int,
        nerf_patch=16,
        nerf_hidden=64,
        scale_factor: int = 4,
    ):
        super().__init__()
        self.config = config
        self.scale_factor = scale_factor
        self.nerf_patch_size = nerf_patch

        assert config.num_hidden_layers % scale_factor % 3 == 0

        self.embeddings = DINOv3ViTEmbeddings(config)
        self.rope_embeddings = DINOv3ViTRopePositionEmbedding(config)

        def gen_rope(depth: int):
            hidden_size = config.hidden_size // (4**depth)
            hacky_config = copy.copy(config)
            hacky_config.hidden_size = hidden_size
            hacky_config.intermediate_size = hacky_config.intermediate_size // (
                3**depth
            )
            hacky_config.num_attention_heads = hacky_config.num_attention_heads // (
                2**depth
            )
            return DINOv3ViTRopePositionEmbedding(hacky_config)

        self.decode_ropes = nn.ModuleList([gen_rope(i + 1) for i in range(2)])
        self.t_embedder = TimestepEmbedder(config.hidden_size)

        self.encoder_layers = nn.ModuleList(
            [DinoEncoderLayer(config) for _ in range(config.num_hidden_layers)]
        )
        self.encoder_norm = nn.LayerNorm(config.hidden_size, eps=config.layer_norm_eps)

        DEPTH_LAYER = [0, 0, 1, 1, 2, 2]
        self.residual_upscaler = ResidualUpscaler(
            config,
            DEPTH_LAYER,  # hardcoded, sorry
            bottleneck_dim=128,
        )
        self.decoder_layers = nn.ModuleList(
            [
                nn.ModuleList(
                    [
                        DinoDecoderLayer(config, depth)
                        for _ in range(DEPTH_LAYER.count(depth))
                    ]
                )
                for depth in sorted(set(DEPTH_LAYER), key=DEPTH_LAYER.index)
            ]
        )
        self.residual_merger = nn.ModuleList(
            [
                nn.ModuleList(
                    [
                        nn.Sequential(
                            nn.SiLU(),
                            nn.Linear(
                                config.hidden_size // (4**depth),
                                2 * config.hidden_size // (4**depth),
                            ),
                        )
                        for _ in range(DEPTH_LAYER.count(depth))
                    ]
                )
                for depth in sorted(set(DEPTH_LAYER), key=DEPTH_LAYER.index)
            ]
        )
        self.upsample = nn.ModuleList([nn.PixelShuffle(2) for _ in range(2)])
        self.upsample_latent = nn.ModuleList(
            [
                nn.Linear(
                    config.hidden_size // (4**depth),
                    config.hidden_size // (4 ** (depth + 1)),
                )
                for depth in range(2)
            ]
        )
        self.rest_decoder = nn.ModuleList(
            [DinoDecoderLayer(config, 2) for _ in range(4)]
        )
        self.decoder_norm = nn.LayerNorm(
            (config.hidden_size // (4**2)), eps=config.layer_norm_eps
        )

        # nerf!
        self.nerf_encoder = NerfEmbedder(3, nerf_hidden, 8)  # (rgb, hidden, freq)
        self.nerf_decoder = nn.ModuleList(
            [NerfBlock(self.config.hidden_size, nerf_hidden) for _ in range(12)]
        )
        self.final_layer = NerfFinalLayer(nerf_hidden, 3)

        # freeze pretrained
        self.embeddings.requires_grad_(False)
        self.rope_embeddings.requires_grad_(False)
        self.encoder_norm.requires_grad_(False)

    def forward(
        self,
        pixel_values: torch.Tensor,
        time: torch.Tensor,
        # cond: torch.Tensor,
        bool_masked_pos: Optional[torch.Tensor] = None,
        head_mask: Optional[torch.Tensor] = None,
    ):
        if time.dim() == 0:
            time = time.repeat(pixel_values.shape[0])

        # resolution config
        B = pixel_values.shape[0]
        dino_h = pixel_values.shape[-2] // self.config.patch_size
        dino_w = pixel_values.shape[-1] // self.config.patch_size
        nerf_h = pixel_values.shape[-2] // self.nerf_patch_size
        nerf_w = pixel_values.shape[-1] // self.nerf_patch_size

        pixel_values = pixel_values.to(self.embeddings.patch_embeddings.weight.dtype)
        position_embeddings = self.rope_embeddings(pixel_values)

        x = self.embeddings(pixel_values, bool_masked_pos=bool_masked_pos)
        t = self.t_embedder(time).unsqueeze(1)
        # y = self.y_embedder(cond, self.training).unsqueeze(1)
        # conditioning_input = t.to(x.dtype) + y.to(x.dtype)
        conditioning_input = t.to(x.dtype)

        residual = []
        for i, layer_module in enumerate(self.encoder_layers):
            if i % self.scale_factor == 0:
                residual.append(x)
            layer_head_mask = head_mask[i] if head_mask is not None else None
            x = layer_module(
                x,
                conditioning_input=conditioning_input,
                attention_mask=layer_head_mask,
                position_embeddings=position_embeddings,
            )

        x = self.encoder_norm(x)
        reversed_residual = self.residual_upscaler(pixel_values, residual[::-1])

        residual_idx = 0
        for depth, layers in enumerate(self.decoder_layers):
            for i, layer_module in enumerate(layers):  # type: ignore
                x = layer_module(
                    x,
                    conditioning_input=conditioning_input,
                    attention_mask=None,
                    position_embeddings=position_embeddings,
                )
                shift, scale = self.residual_merger[depth][i](  # type: ignore
                    reversed_residual[residual_idx]
                ).chunk(2, dim=-1)
                x = x * (1 + scale) + shift
                residual_idx += 1
            x = torch.cat(
                (
                    rearrange(
                        self.upsample[depth](
                            rearrange(
                                x[:, 1 + self.config.num_register_tokens :],
                                "b (h w) d -> b d h w",
                                h=pixel_values.shape[-2]
                                // (self.config.patch_size)
                                * (2**depth),
                            )
                        ),
                        "b d h w -> b (h w) d",
                    )
                    if depth != 2
                    else x[:, 1 + self.config.num_register_tokens :],
                    self.upsample_latent[depth](
                        x[:, : 1 + self.config.num_register_tokens]
                    )
                    if depth != 2
                    else x[:, : 1 + self.config.num_register_tokens],
                ),
                dim=1,
            )
            position_embeddings = (
                self.decode_ropes[depth](
                    torch.zeros(
                        (
                            1,
                            1,
                            pixel_values.shape[-2] * (2 ** (depth + 1)),
                            pixel_values.shape[-1] * (2 ** (depth + 1)),
                        ),
                        device=x.device,
                    ).to(self.embeddings.patch_embeddings.weight.dtype)
                )
                if depth != 2
                else position_embeddings
            )

        for i, layer_module in enumerate(self.rest_decoder):
            layer_head_mask = head_mask[i] if head_mask is not None else None
            x = layer_module(
                x,
                conditioning_input=conditioning_input,
                attention_mask=layer_head_mask,
                position_embeddings=position_embeddings,
                do_condition=False,
            )  # (batch, image // patch^2, 1024)

        x = x[:, 1 + self.config.num_register_tokens :, :]

        nerf_cond = nn.functional.silu(t + x)  # (batch, image // patch^2, 1024)
        nerf_cond = nerf_cond.reshape(
            B, dino_h, dino_w, self.config.hidden_size
        ).permute(0, 3, 1, 2)  # (batch, 1024, image // patch, image // patch)
        # nerf_cond = nn.functional.interpolate(
        #     nerf_cond, size=(nerf_h, nerf_w), mode="bilinear", align_corners=False
        # )
        nerf_cond = (
            nerf_cond.permute(0, 2, 3, 1)
            .reshape(-1, nerf_h * nerf_w, self.config.hidden_size)
            .view(-1, self.config.hidden_size)
        )

        # nerf
        x_nerf = nn.functional.unfold(
            pixel_values, self.nerf_patch_size, stride=self.nerf_patch_size
        ).transpose(1, 2)
        x_nerf = x_nerf.reshape(
            B * x_nerf.shape[1], -1, self.nerf_patch_size**2
        ).transpose(1, 2)
        x_nerf = self.nerf_encoder(x_nerf)

        for module in self.nerf_decoder:
            x_nerf = module(x_nerf, nerf_cond)

        x_nerf = self.final_layer(x_nerf)

        num_patches = nerf_h * nerf_w
        x_nerf = x_nerf.reshape(
            B * num_patches, -1
        )  # (B*num_patches, 48): flatten pixels+RGB per patch
        x_nerf = (
            x_nerf.view(B, num_patches, -1).transpose(1, 2).contiguous()
        )  # (B, 48, num_patches)

        res = nn.functional.fold(
            x_nerf,
            (pixel_values.shape[-2], pixel_values.shape[-1]),
            kernel_size=self.nerf_patch_size,
            stride=self.nerf_patch_size,
        )
        return res

    def get_residual(
        self,
        pixel_values: torch.Tensor,
        time: Optional[torch.Tensor],
        do_condition: bool,
    ):
        pixel_values = pixel_values.to(self.embeddings.patch_embeddings.weight.dtype)
        position_embeddings = self.rope_embeddings(pixel_values)

        x = self.embeddings(pixel_values, bool_masked_pos=None)

        if do_condition:
            t = self.t_embedder(time).unsqueeze(1)
            # y = self.y_embedder(cond, self.training).unsqueeze(1)
            # conditioning_input = t.to(x.dtype) + y.to(x.dtype)
            conditioning_input = t.to(x.dtype)
        else:
            conditioning_input = None

        residual = []
        for i, layer_module in enumerate(self.encoder_layers):
            if i % self.scale_factor == 0:
                residual.append(x)

            x = layer_module(
                x,
                conditioning_input=conditioning_input,
                attention_mask=None,
                position_embeddings=position_embeddings,
            )
        x = x[:, 1 + self.config.num_register_tokens :]
        x = self.decoder_norm(x)

        return self.decoder(x, image_size=pixel_values.shape[-2:]), residual

    @staticmethod
    def from_pretrained_backbone(name: str):
        config = DINOv3ViTConfig.from_pretrained(name)
        instance = UTransformer(config, 0)

        weight_dict = {}
        with safe_open(
            hf_hub_download(name, "model.safetensors"), framework="pt", device="cuda:1"
        ) as f:
            for key in f.keys():
                new_key = key.replace("layer.", "encoder_layers.").replace(
                    "norm.", "encoder_norm."
                )

                weight_dict[new_key] = f.get_tensor(key)

        instance.load_state_dict(weight_dict, strict=False)

        return instance