# Copyright 2024 the Fast authors and The HuggingFace Inc. team. All rights reserved.
#
# 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
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#     http://www.apache.org/licenses/LICENSE-2.0
#
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# distributed under the License is distributed on an "AS IS" BASIS,
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"""PyTorch TextNet model."""

from typing import Any

import torch
import torch.nn as nn
from torch import Tensor

from transformers import PreTrainedModel
from transformers.activations import ACT2CLS
from transformers.modeling_outputs import (
    BackboneOutput,
    BaseModelOutputWithNoAttention,
    BaseModelOutputWithPoolingAndNoAttention,
    ImageClassifierOutputWithNoAttention,
)
from transformers.models.textnet.configuration_textnet import TextNetConfig
from transformers.utils import logging
from transformers.utils.backbone_utils import BackboneMixin

from ...utils import auto_docstring


logger = logging.get_logger(__name__)


class TextNetConvLayer(nn.Module):
    def __init__(self, config: TextNetConfig):
        super().__init__()

        self.kernel_size = config.stem_kernel_size
        self.stride = config.stem_stride
        self.activation_function = config.stem_act_func

        padding = (
            (config.kernel_size[0] // 2, config.kernel_size[1] // 2)
            if isinstance(config.stem_kernel_size, tuple)
            else config.stem_kernel_size // 2
        )

        self.conv = nn.Conv2d(
            config.stem_num_channels,
            config.stem_out_channels,
            kernel_size=config.stem_kernel_size,
            stride=config.stem_stride,
            padding=padding,
            bias=False,
        )
        self.batch_norm = nn.BatchNorm2d(config.stem_out_channels, config.batch_norm_eps)

        self.activation = nn.Identity()
        if self.activation_function is not None:
            self.activation = ACT2CLS[self.activation_function]()

    def forward(self, hidden_states: torch.Tensor) -> torch.Tensor:
        hidden_states = self.conv(hidden_states)
        hidden_states = self.batch_norm(hidden_states)
        return self.activation(hidden_states)


class TextNetRepConvLayer(nn.Module):
    r"""
    This layer supports re-parameterization by combining multiple convolutional branches
    (e.g., main convolution, vertical, horizontal, and identity branches) during training.
    At inference time, these branches can be collapsed into a single convolution for
    efficiency, as per the re-parameterization paradigm.

    The "Rep" in the name stands for "re-parameterization" (introduced by RepVGG).
    """

    def __init__(self, config: TextNetConfig, in_channels: int, out_channels: int, kernel_size: int, stride: int):
        super().__init__()

        self.num_channels = in_channels
        self.out_channels = out_channels
        self.kernel_size = kernel_size
        self.stride = stride

        padding = ((kernel_size[0] - 1) // 2, (kernel_size[1] - 1) // 2)

        self.activation_function = nn.ReLU()

        self.main_conv = nn.Conv2d(
            in_channels=in_channels,
            out_channels=out_channels,
            kernel_size=kernel_size,
            stride=stride,
            padding=padding,
            bias=False,
        )
        self.main_batch_norm = nn.BatchNorm2d(num_features=out_channels, eps=config.batch_norm_eps)

        vertical_padding = ((kernel_size[0] - 1) // 2, 0)
        horizontal_padding = (0, (kernel_size[1] - 1) // 2)

        if kernel_size[1] != 1:
            self.vertical_conv = nn.Conv2d(
                in_channels=in_channels,
                out_channels=out_channels,
                kernel_size=(kernel_size[0], 1),
                stride=stride,
                padding=vertical_padding,
                bias=False,
            )
            self.vertical_batch_norm = nn.BatchNorm2d(num_features=out_channels, eps=config.batch_norm_eps)
        else:
            self.vertical_conv, self.vertical_batch_norm = None, None

        if kernel_size[0] != 1:
            self.horizontal_conv = nn.Conv2d(
                in_channels=in_channels,
                out_channels=out_channels,
                kernel_size=(1, kernel_size[1]),
                stride=stride,
                padding=horizontal_padding,
                bias=False,
            )
            self.horizontal_batch_norm = nn.BatchNorm2d(num_features=out_channels, eps=config.batch_norm_eps)
        else:
            self.horizontal_conv, self.horizontal_batch_norm = None, None

        self.rbr_identity = (
            nn.BatchNorm2d(num_features=in_channels, eps=config.batch_norm_eps)
            if out_channels == in_channels and stride == 1
            else None
        )

    def forward(self, hidden_states: torch.Tensor) -> torch.Tensor:
        main_outputs = self.main_conv(hidden_states)
        main_outputs = self.main_batch_norm(main_outputs)

        # applies a convolution with a vertical kernel
        if self.vertical_conv is not None:
            vertical_outputs = self.vertical_conv(hidden_states)
            vertical_outputs = self.vertical_batch_norm(vertical_outputs)
            main_outputs = main_outputs + vertical_outputs

        # applies a convolution with a horizontal kernel
        if self.horizontal_conv is not None:
            horizontal_outputs = self.horizontal_conv(hidden_states)
            horizontal_outputs = self.horizontal_batch_norm(horizontal_outputs)
            main_outputs = main_outputs + horizontal_outputs

        if self.rbr_identity is not None:
            id_out = self.rbr_identity(hidden_states)
            main_outputs = main_outputs + id_out

        return self.activation_function(main_outputs)


class TextNetStage(nn.Module):
    def __init__(self, config: TextNetConfig, depth: int):
        super().__init__()
        kernel_size = config.conv_layer_kernel_sizes[depth]
        stride = config.conv_layer_strides[depth]

        num_layers = len(kernel_size)
        stage_in_channel_size = config.hidden_sizes[depth]
        stage_out_channel_size = config.hidden_sizes[depth + 1]

        in_channels = [stage_in_channel_size] + [stage_out_channel_size] * (num_layers - 1)
        out_channels = [stage_out_channel_size] * num_layers

        stage = []
        for stage_config in zip(in_channels, out_channels, kernel_size, stride):
            stage.append(TextNetRepConvLayer(config, *stage_config))
        self.stage = nn.ModuleList(stage)

    def forward(self, hidden_state):
        for block in self.stage:
            hidden_state = block(hidden_state)
        return hidden_state


class TextNetEncoder(nn.Module):
    def __init__(self, config: TextNetConfig):
        super().__init__()

        stages = []
        num_stages = len(config.conv_layer_kernel_sizes)
        for stage_ix in range(num_stages):
            stages.append(TextNetStage(config, stage_ix))

        self.stages = nn.ModuleList(stages)

    def forward(
        self,
        hidden_state: torch.Tensor,
        output_hidden_states: bool | None = None,
        return_dict: bool | None = None,
    ) -> BaseModelOutputWithNoAttention:
        hidden_states = [hidden_state]
        for stage in self.stages:
            hidden_state = stage(hidden_state)
            hidden_states.append(hidden_state)

        if not return_dict:
            output = (hidden_state,)
            return output + (hidden_states,) if output_hidden_states else output

        return BaseModelOutputWithNoAttention(last_hidden_state=hidden_state, hidden_states=hidden_states)


@auto_docstring
class TextNetPreTrainedModel(PreTrainedModel):
    config: TextNetConfig
    base_model_prefix = "textnet"
    main_input_name = "pixel_values"


@auto_docstring
class TextNetModel(TextNetPreTrainedModel):
    def __init__(self, config):
        super().__init__(config)
        self.stem = TextNetConvLayer(config)
        self.encoder = TextNetEncoder(config)
        self.pooler = nn.AdaptiveAvgPool2d((2, 2))
        self.post_init()

    @auto_docstring
    def forward(
        self,
        pixel_values: Tensor,
        output_hidden_states: bool | None = None,
        return_dict: bool | None = None,
        **kwargs,
    ) -> tuple[Any, list[Any]] | tuple[Any] | BaseModelOutputWithPoolingAndNoAttention:
        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
        )

        hidden_state = self.stem(pixel_values)

        encoder_outputs = self.encoder(
            hidden_state, output_hidden_states=output_hidden_states, return_dict=return_dict
        )

        last_hidden_state = encoder_outputs[0]
        pooled_output = self.pooler(last_hidden_state)

        if not return_dict:
            output = (last_hidden_state, pooled_output)
            return output + (encoder_outputs[1],) if output_hidden_states else output

        return BaseModelOutputWithPoolingAndNoAttention(
            last_hidden_state=last_hidden_state,
            pooler_output=pooled_output,
            hidden_states=encoder_outputs[1] if output_hidden_states else None,
        )


@auto_docstring(
    custom_intro="""
    TextNet Model with an image classification head on top (a linear layer on top of the pooled features), e.g. for
    ImageNet.
    """
)
class TextNetForImageClassification(TextNetPreTrainedModel):
    def __init__(self, config):
        super().__init__(config)
        self.num_labels = config.num_labels
        self.textnet = TextNetModel(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 requests
        >>> from transformers import TextNetForImageClassification, TextNetImageProcessor
        >>> from PIL import Image

        >>> url = "http://images.cocodataset.org/val2017/000000039769.jpg"
        >>> image = Image.open(requests.get(url, stream=True).raw)

        >>> processor = TextNetImageProcessor.from_pretrained("czczup/textnet-base")
        >>> model = TextNetForImageClassification.from_pretrained("czczup/textnet-base")

        >>> 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

        outputs = self.textnet(pixel_values, 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)


@auto_docstring(
    custom_intro="""
    TextNet backbone, to be used with frameworks like DETR and MaskFormer.
    """
)
class TextNetBackbone(TextNetPreTrainedModel, BackboneMixin):
    has_attentions = False

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

        self.textnet = TextNetModel(config)
        self.num_features = config.hidden_sizes

        # 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,
    ) -> tuple[tuple] | BackboneOutput:
        r"""
        Examples:

        ```python
        >>> import torch
        >>> import requests
        >>> from PIL import Image
        >>> from transformers import AutoImageProcessor, AutoBackbone

        >>> url = "http://images.cocodataset.org/val2017/000000039769.jpg"
        >>> image = Image.open(requests.get(url, stream=True).raw)

        >>> processor = AutoImageProcessor.from_pretrained("czczup/textnet-base")
        >>> model = AutoBackbone.from_pretrained("czczup/textnet-base")

        >>> inputs = processor(image, return_tensors="pt")
        >>> with torch.no_grad():
        >>>     outputs = model(**inputs)
        ```"""
        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
        )

        outputs = self.textnet(pixel_values, output_hidden_states=True, return_dict=return_dict)

        hidden_states = outputs.hidden_states if return_dict else outputs[2]

        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:
                hidden_states = outputs.hidden_states if return_dict else outputs[2]
                output += (hidden_states,)
            return output

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


__all__ = ["TextNetBackbone", "TextNetModel", "TextNetPreTrainedModel", "TextNetForImageClassification"]
