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# Copyright 2025 Baidu Inc and The HuggingFace Inc. team.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.


import torch
import torch.nn.functional as F
from torch import Tensor, nn

from ... import initialization as init
from ...activations import ACT2FN
from ...backbone_utils import BackboneMixin
from ...modeling_outputs import BackboneOutput, BaseModelOutputWithNoAttention, ImageClassifierOutputWithNoAttention
from ...modeling_utils import PreTrainedModel
from ...utils import auto_docstring
from .configuration_hgnet_v2 import HGNetV2Config


# General docstring


@auto_docstring
class HGNetV2PreTrainedModel(PreTrainedModel):
    config: HGNetV2Config
    base_model_prefix = "hgnetv2"
    main_input_name = "pixel_values"
    input_modalities = ("image",)
    _no_split_modules = ["HGNetV2BasicLayer"]

    def _init_weights(self, module):
        super()._init_weights(module)
        # We need to check it like that as d_fine models replace the BatchNorm2d by their own
        if "BatchNorm" in module.__class__.__name__:
            init.ones_(module.weight)
            init.zeros_(module.bias)
            init.zeros_(module.running_mean)
            init.ones_(module.running_var)


class HGNetV2LearnableAffineBlock(nn.Module):
    def __init__(self, scale_value: float = 1.0, bias_value: float = 0.0):
        super().__init__()
        self.scale = nn.Parameter(torch.tensor([scale_value]), requires_grad=True)
        self.bias = nn.Parameter(torch.tensor([bias_value]), requires_grad=True)

    def forward(self, hidden_state: Tensor) -> Tensor:
        hidden_state = self.scale * hidden_state + self.bias
        return hidden_state


class HGNetV2ConvLayer(nn.Module):
    def __init__(
        self,
        in_channels: int,
        out_channels: int,
        kernel_size: int,
        stride: int = 1,
        groups: int = 1,
        activation: str = "relu",
        use_learnable_affine_block: bool = False,
    ):
        super().__init__()
        self.convolution = nn.Conv2d(
            in_channels,
            out_channels,
            kernel_size=kernel_size,
            stride=stride,
            groups=groups,
            padding=(kernel_size - 1) // 2,
            bias=False,
        )
        self.normalization = nn.BatchNorm2d(out_channels)
        self.activation = ACT2FN[activation] if activation is not None else nn.Identity()
        if activation and use_learnable_affine_block:
            self.lab = HGNetV2LearnableAffineBlock()
        else:
            self.lab = nn.Identity()

    def forward(self, input: Tensor) -> Tensor:
        hidden_state = self.convolution(input)
        hidden_state = self.normalization(hidden_state)
        hidden_state = self.activation(hidden_state)
        hidden_state = self.lab(hidden_state)
        return hidden_state


class HGNetV2ConvLayerLight(nn.Module):
    def __init__(
        self, in_channels: int, out_channels: int, kernel_size: int, use_learnable_affine_block: bool = False
    ):
        super().__init__()
        self.conv1 = HGNetV2ConvLayer(
            in_channels,
            out_channels,
            kernel_size=1,
            activation=None,
            use_learnable_affine_block=use_learnable_affine_block,
        )
        self.conv2 = HGNetV2ConvLayer(
            out_channels,
            out_channels,
            kernel_size=kernel_size,
            groups=out_channels,
            use_learnable_affine_block=use_learnable_affine_block,
        )

    def forward(self, hidden_state: Tensor) -> Tensor:
        hidden_state = self.conv1(hidden_state)
        hidden_state = self.conv2(hidden_state)
        return hidden_state


class HGNetV2Embeddings(nn.Module):
    def __init__(self, config: HGNetV2Config):
        super().__init__()

        self.stem1 = HGNetV2ConvLayer(
            config.stem_channels[0],
            config.stem_channels[1],
            kernel_size=3,
            stride=2,
            activation=config.hidden_act,
            use_learnable_affine_block=config.use_learnable_affine_block,
        )
        self.stem2a = HGNetV2ConvLayer(
            config.stem_channels[1],
            config.stem_channels[1] // 2,
            kernel_size=2,
            stride=1,
            activation=config.hidden_act,
            use_learnable_affine_block=config.use_learnable_affine_block,
        )
        self.stem2b = HGNetV2ConvLayer(
            config.stem_channels[1] // 2,
            config.stem_channels[1],
            kernel_size=2,
            stride=1,
            activation=config.hidden_act,
            use_learnable_affine_block=config.use_learnable_affine_block,
        )
        self.stem3 = HGNetV2ConvLayer(
            config.stem_channels[1] * 2,
            config.stem_channels[1],
            kernel_size=3,
            stride=2,
            activation=config.hidden_act,
            use_learnable_affine_block=config.use_learnable_affine_block,
        )
        self.stem4 = HGNetV2ConvLayer(
            config.stem_channels[1],
            config.stem_channels[2],
            kernel_size=1,
            stride=1,
            activation=config.hidden_act,
            use_learnable_affine_block=config.use_learnable_affine_block,
        )

        self.pool = nn.MaxPool2d(kernel_size=2, stride=1, ceil_mode=True)
        self.num_channels = config.num_channels

    def forward(self, pixel_values: Tensor) -> Tensor:
        num_channels = pixel_values.shape[1]
        if num_channels != self.num_channels:
            raise ValueError(
                "Make sure that the channel dimension of the pixel values match with the one set in the configuration."
            )
        embedding = self.stem1(pixel_values)
        embedding = F.pad(embedding, (0, 1, 0, 1))
        emb_stem_2a = self.stem2a(embedding)
        emb_stem_2a = F.pad(emb_stem_2a, (0, 1, 0, 1))
        emb_stem_2a = self.stem2b(emb_stem_2a)
        pooled_emb = self.pool(embedding)
        embedding = torch.cat([pooled_emb, emb_stem_2a], dim=1)
        embedding = self.stem3(embedding)
        embedding = self.stem4(embedding)
        return embedding


class HGNetV2BasicLayer(nn.Module):
    def __init__(
        self,
        in_channels: int,
        middle_channels: int,
        out_channels: int,
        layer_num: int,
        kernel_size: int = 3,
        residual: bool = False,
        light_block: bool = False,
        drop_path: float = 0.0,
        use_learnable_affine_block: bool = False,
    ):
        super().__init__()
        self.residual = residual

        self.layers = nn.ModuleList()
        for i in range(layer_num):
            temp_in_channels = in_channels if i == 0 else middle_channels
            if light_block:
                block = HGNetV2ConvLayerLight(
                    in_channels=temp_in_channels,
                    out_channels=middle_channels,
                    kernel_size=kernel_size,
                    use_learnable_affine_block=use_learnable_affine_block,
                )
            else:
                block = HGNetV2ConvLayer(
                    in_channels=temp_in_channels,
                    out_channels=middle_channels,
                    kernel_size=kernel_size,
                    use_learnable_affine_block=use_learnable_affine_block,
                    stride=1,
                )
            self.layers.append(block)

        # feature aggregation
        total_channels = in_channels + layer_num * middle_channels
        aggregation_squeeze_conv = HGNetV2ConvLayer(
            total_channels,
            out_channels // 2,
            kernel_size=1,
            stride=1,
            use_learnable_affine_block=use_learnable_affine_block,
        )
        aggregation_excitation_conv = HGNetV2ConvLayer(
            out_channels // 2,
            out_channels,
            kernel_size=1,
            stride=1,
            use_learnable_affine_block=use_learnable_affine_block,
        )
        self.aggregation = nn.Sequential(
            aggregation_squeeze_conv,
            aggregation_excitation_conv,
        )
        self.drop_path = nn.Dropout(drop_path) if drop_path else nn.Identity()

    def forward(self, hidden_state: Tensor) -> Tensor:
        identity = hidden_state
        output = [hidden_state]
        for layer in self.layers:
            hidden_state = layer(hidden_state)
            output.append(hidden_state)
        hidden_state = torch.cat(output, dim=1)
        hidden_state = self.aggregation(hidden_state)
        if self.residual:
            hidden_state = self.drop_path(hidden_state) + identity
        return hidden_state


class HGNetV2Stage(nn.Module):
    def __init__(self, config: HGNetV2Config, stage_index: int, drop_path: float = 0.0):
        super().__init__()
        in_channels = config.stage_in_channels[stage_index]
        mid_channels = config.stage_mid_channels[stage_index]
        out_channels = config.stage_out_channels[stage_index]
        num_blocks = config.stage_num_blocks[stage_index]
        num_layers = config.stage_numb_of_layers[stage_index]
        downsample = config.stage_downsample[stage_index]
        light_block = config.stage_light_block[stage_index]
        kernel_size = config.stage_kernel_size[stage_index]
        use_learnable_affine_block = config.use_learnable_affine_block

        if downsample:
            self.downsample = HGNetV2ConvLayer(
                in_channels, in_channels, kernel_size=3, stride=2, groups=in_channels, activation=None
            )
        else:
            self.downsample = nn.Identity()

        blocks_list = []
        for i in range(num_blocks):
            blocks_list.append(
                HGNetV2BasicLayer(
                    in_channels if i == 0 else out_channels,
                    mid_channels,
                    out_channels,
                    num_layers,
                    residual=(i != 0),
                    kernel_size=kernel_size,
                    light_block=light_block,
                    drop_path=drop_path,
                    use_learnable_affine_block=use_learnable_affine_block,
                )
            )
        self.blocks = nn.ModuleList(blocks_list)

    def forward(self, hidden_state: Tensor) -> Tensor:
        hidden_state = self.downsample(hidden_state)
        for block in self.blocks:
            hidden_state = block(hidden_state)
        return hidden_state


class HGNetV2Encoder(nn.Module):
    def __init__(self, config: HGNetV2Config):
        super().__init__()
        self.stages = nn.ModuleList([])
        for stage_index in range(len(config.stage_in_channels)):
            resnet_stage = HGNetV2Stage(config, stage_index)
            self.stages.append(resnet_stage)

    def forward(
        self, hidden_state: Tensor, output_hidden_states: bool = False, return_dict: bool = True
    ) -> BaseModelOutputWithNoAttention:
        hidden_states = () if output_hidden_states else None

        for stage in self.stages:
            if output_hidden_states:
                hidden_states = hidden_states + (hidden_state,)

            hidden_state = stage(hidden_state)

        if output_hidden_states:
            hidden_states = hidden_states + (hidden_state,)

        if not return_dict:
            return tuple(v for v in [hidden_state, hidden_states] if v is not None)

        return BaseModelOutputWithNoAttention(
            last_hidden_state=hidden_state,
            hidden_states=hidden_states,
        )


class HGNetV2Backbone(BackboneMixin, HGNetV2PreTrainedModel):
    has_attentions = False

    def __init__(self, config: HGNetV2Config):
        super().__init__(config)
        self.depths = config.depths
        self.num_features = [config.embedding_size] + config.hidden_sizes
        self.embedder = HGNetV2Embeddings(config)
        self.encoder = HGNetV2Encoder(config)

        # initialize weights and apply final processing
        self.post_init()

    @auto_docstring
    def forward(
        self,
        pixel_values: Tensor,
        output_hidden_states: bool | None = None,
        return_dict: bool | None = None,
        **kwargs,
    ) -> BackboneOutput:
        r"""
        Examples:

        ```python
        >>> from transformers import HGNetV2Config, HGNetV2Backbone
        >>> import torch

        >>> config = HGNetV2Config()
        >>> model = HGNetV2Backbone(config)

        >>> pixel_values = torch.randn(1, 3, 224, 224)

        >>> with torch.no_grad():
        ...     outputs = model(pixel_values)

        >>> feature_maps = outputs.feature_maps
        >>> list(feature_maps[-1].shape)
        [1, 2048, 7, 7]
        ```"""
        return_dict = return_dict if return_dict is not None else self.config.use_return_dict
        output_hidden_states = (
            output_hidden_states if output_hidden_states is not None else self.config.output_hidden_states
        )

        embedding_output = self.embedder(pixel_values)

        outputs = self.encoder(embedding_output, output_hidden_states=True, return_dict=True)

        hidden_states = outputs.hidden_states

        feature_maps = ()
        for idx, stage in enumerate(self.stage_names):
            if stage in self.out_features:
                feature_maps += (hidden_states[idx],)

        if not return_dict:
            output = (feature_maps,)
            if output_hidden_states:
                output += (outputs.hidden_states,)
            return output

        return BackboneOutput(
            feature_maps=feature_maps,
            hidden_states=outputs.hidden_states if output_hidden_states else None,
            attentions=None,
        )


@auto_docstring(
    custom_intro="""
    HGNetV2 Model with an image classification head on top (a linear layer on top of the pooled features), e.g. for
    ImageNet.
    """
)
class HGNetV2ForImageClassification(HGNetV2PreTrainedModel):
    def __init__(self, config: HGNetV2Config):
        super().__init__(config)
        self.num_labels = config.num_labels
        self.embedder = HGNetV2Embeddings(config)
        self.encoder = HGNetV2Encoder(config)
        self.avg_pool = nn.AdaptiveAvgPool2d((1, 1))
        self.flatten = nn.Flatten()
        self.fc = nn.Linear(config.hidden_sizes[-1], config.num_labels) if config.num_labels > 0 else nn.Identity()

        # classification head
        self.classifier = nn.ModuleList([self.avg_pool, self.flatten])

        # initialize weights and apply final processing
        self.post_init()

    @auto_docstring
    def forward(
        self,
        pixel_values: torch.FloatTensor | None = None,
        labels: torch.LongTensor | None = None,
        output_hidden_states: bool | None = None,
        return_dict: bool | None = None,
        **kwargs,
    ) -> ImageClassifierOutputWithNoAttention:
        r"""
        labels (`torch.LongTensor` of shape `(batch_size,)`, *optional*):
            Labels for computing the image classification/regression loss. Indices should be in `[0, ...,
            config.num_labels - 1]`. If `config.num_labels == 1` a regression loss is computed (Mean-Square loss), If
            `config.num_labels > 1` a classification loss is computed (Cross-Entropy).

        Examples:
        ```python
        >>> import torch
        >>> import httpx
        >>> from io import BytesIO
        >>> from transformers import HGNetV2ForImageClassification, AutoImageProcessor
        >>> from PIL import Image

        >>> url = "http://images.cocodataset.org/val2017/000000039769.jpg"
        >>> with httpx.stream("GET", url) as response:
        ...     image = Image.open(BytesIO(response.read()))

        >>> model = HGNetV2ForImageClassification.from_pretrained("ustc-community/hgnet-v2")
        >>> processor = AutoImageProcessor.from_pretrained("ustc-community/hgnet-v2")

        >>> inputs = processor(images=image, return_tensors="pt")
        >>> with torch.no_grad():
        ...     outputs = model(**inputs)
        >>> outputs.logits.shape
        torch.Size([1, 2])
        ```"""
        return_dict = return_dict if return_dict is not None else self.config.use_return_dict
        output_hidden_states = (
            output_hidden_states if output_hidden_states is not None else self.config.output_hidden_states
        )
        embedding_output = self.embedder(pixel_values)
        outputs = self.encoder(embedding_output, output_hidden_states=output_hidden_states, return_dict=return_dict)
        last_hidden_state = outputs[0]
        for layer in self.classifier:
            last_hidden_state = layer(last_hidden_state)
        logits = self.fc(last_hidden_state)
        loss = None

        if labels is not None:
            loss = self.loss_function(labels, logits, self.config)

        if not return_dict:
            output = (logits,) + outputs[2:]
            return (loss,) + output if loss is not None else output

        return ImageClassifierOutputWithNoAttention(loss=loss, logits=logits, hidden_states=outputs.hidden_states)


__all__ = ["HGNetV2Backbone", "HGNetV2PreTrainedModel", "HGNetV2ForImageClassification"]
