# coding=utf-8
# Copyright 2022 KAIST 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
#
#     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.
""" PyTorch GLPN model."""


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

import torch
import torch.utils.checkpoint
from torch import nn

from ...activations import ACT2FN
from ...modeling_outputs import BaseModelOutput, DepthEstimatorOutput
from ...modeling_utils import PreTrainedModel
from ...pytorch_utils import find_pruneable_heads_and_indices, prune_linear_layer
from ...utils import (
    add_code_sample_docstrings,
    add_start_docstrings,
    add_start_docstrings_to_model_forward,
    logging,
    replace_return_docstrings,
)
from .configuration_glpn import GLPNConfig


logger = logging.get_logger(__name__)


# General docstring
_CONFIG_FOR_DOC = "GLPNConfig"
_FEAT_EXTRACTOR_FOR_DOC = "GLPNFeatureExtractor"

# Base docstring
_CHECKPOINT_FOR_DOC = "vinvino02/glpn-kitti"
_EXPECTED_OUTPUT_SHAPE = [1, 512, 15, 20]

GLPN_PRETRAINED_MODEL_ARCHIVE_LIST = [
    "vinvino02/glpn-kitti",
    # See all GLPN models at https://huggingface.co/models?filter=glpn
]


# Copied from transformers.models.segformer.modeling_segformer.drop_path
def drop_path(input, drop_prob: float = 0.0, training: bool = False):
    """
    Drop paths (Stochastic Depth) per sample (when applied in main path of residual blocks).

    Comment by Ross Wightman: This is the same as the DropConnect impl I created for EfficientNet, etc networks,
    however, the original name is misleading as 'Drop Connect' is a different form of dropout in a separate paper...
    See discussion: https://github.com/tensorflow/tpu/issues/494#issuecomment-532968956 ... I've opted for changing the
    layer and argument names to 'drop path' rather than mix DropConnect as a layer name and use 'survival rate' as the
    argument.
    """
    if drop_prob == 0.0 or not training:
        return input
    keep_prob = 1 - drop_prob
    shape = (input.shape[0],) + (1,) * (input.ndim - 1)  # work with diff dim tensors, not just 2D ConvNets
    random_tensor = keep_prob + torch.rand(shape, dtype=input.dtype, device=input.device)
    random_tensor.floor_()  # binarize
    output = input.div(keep_prob) * random_tensor
    return output


# Copied from transformers.models.segformer.modeling_segformer.SegformerDropPath
class GLPNDropPath(nn.Module):
    """Drop paths (Stochastic Depth) per sample (when applied in main path of residual blocks)."""

    def __init__(self, drop_prob: Optional[float] = None) -> None:
        super().__init__()
        self.drop_prob = drop_prob

    def forward(self, x: torch.Tensor) -> torch.Tensor:
        return drop_path(x, self.drop_prob, self.training)

    def extra_repr(self) -> str:
        return "p={}".format(self.drop_prob)


# Copied from transformers.models.segformer.modeling_segformer.SegformerOverlapPatchEmbeddings
class GLPNOverlapPatchEmbeddings(nn.Module):
    """Construct the overlapping patch embeddings."""

    def __init__(self, patch_size, stride, num_channels, hidden_size):
        super().__init__()
        self.proj = nn.Conv2d(
            num_channels,
            hidden_size,
            kernel_size=patch_size,
            stride=stride,
            padding=patch_size // 2,
        )

        self.layer_norm = nn.LayerNorm(hidden_size)

    def forward(self, pixel_values):
        embeddings = self.proj(pixel_values)
        _, _, height, width = embeddings.shape
        # (batch_size, num_channels, height, width) -> (batch_size, num_channels, height*width) -> (batch_size, height*width, num_channels)
        # this can be fed to a Transformer layer
        embeddings = embeddings.flatten(2).transpose(1, 2)
        embeddings = self.layer_norm(embeddings)
        return embeddings, height, width


# Copied from transformers.models.segformer.modeling_segformer.SegformerEfficientSelfAttention
class GLPNEfficientSelfAttention(nn.Module):
    """SegFormer's efficient self-attention mechanism. Employs the sequence reduction process introduced in the [PvT
    paper](https://arxiv.org/abs/2102.12122)."""

    def __init__(self, config, hidden_size, num_attention_heads, sequence_reduction_ratio):
        super().__init__()
        self.hidden_size = hidden_size
        self.num_attention_heads = num_attention_heads

        if self.hidden_size % self.num_attention_heads != 0:
            raise ValueError(
                f"The hidden size ({self.hidden_size}) is not a multiple of the number of attention "
                f"heads ({self.num_attention_heads})"
            )

        self.attention_head_size = int(self.hidden_size / self.num_attention_heads)
        self.all_head_size = self.num_attention_heads * self.attention_head_size

        self.query = nn.Linear(self.hidden_size, self.all_head_size)
        self.key = nn.Linear(self.hidden_size, self.all_head_size)
        self.value = nn.Linear(self.hidden_size, self.all_head_size)

        self.dropout = nn.Dropout(config.attention_probs_dropout_prob)

        self.sr_ratio = sequence_reduction_ratio
        if sequence_reduction_ratio > 1:
            self.sr = nn.Conv2d(
                hidden_size, hidden_size, kernel_size=sequence_reduction_ratio, stride=sequence_reduction_ratio
            )
            self.layer_norm = nn.LayerNorm(hidden_size)

    def transpose_for_scores(self, hidden_states):
        new_shape = hidden_states.size()[:-1] + (self.num_attention_heads, self.attention_head_size)
        hidden_states = hidden_states.view(new_shape)
        return hidden_states.permute(0, 2, 1, 3)

    def forward(
        self,
        hidden_states,
        height,
        width,
        output_attentions=False,
    ):
        query_layer = self.transpose_for_scores(self.query(hidden_states))

        if self.sr_ratio > 1:
            batch_size, seq_len, num_channels = hidden_states.shape
            # Reshape to (batch_size, num_channels, height, width)
            hidden_states = hidden_states.permute(0, 2, 1).reshape(batch_size, num_channels, height, width)
            # Apply sequence reduction
            hidden_states = self.sr(hidden_states)
            # Reshape back to (batch_size, seq_len, num_channels)
            hidden_states = hidden_states.reshape(batch_size, num_channels, -1).permute(0, 2, 1)
            hidden_states = self.layer_norm(hidden_states)

        key_layer = self.transpose_for_scores(self.key(hidden_states))
        value_layer = self.transpose_for_scores(self.value(hidden_states))

        # Take the dot product between "query" and "key" to get the raw attention scores.
        attention_scores = torch.matmul(query_layer, key_layer.transpose(-1, -2))

        attention_scores = attention_scores / math.sqrt(self.attention_head_size)

        # Normalize the attention scores to probabilities.
        attention_probs = nn.functional.softmax(attention_scores, dim=-1)

        # This is actually dropping out entire tokens to attend to, which might
        # seem a bit unusual, but is taken from the original Transformer paper.
        attention_probs = self.dropout(attention_probs)

        context_layer = torch.matmul(attention_probs, value_layer)

        context_layer = context_layer.permute(0, 2, 1, 3).contiguous()
        new_context_layer_shape = context_layer.size()[:-2] + (self.all_head_size,)
        context_layer = context_layer.view(new_context_layer_shape)

        outputs = (context_layer, attention_probs) if output_attentions else (context_layer,)

        return outputs


# Copied from transformers.models.segformer.modeling_segformer.SegformerSelfOutput
class GLPNSelfOutput(nn.Module):
    def __init__(self, config, hidden_size):
        super().__init__()
        self.dense = nn.Linear(hidden_size, hidden_size)
        self.dropout = nn.Dropout(config.hidden_dropout_prob)

    def forward(self, hidden_states, input_tensor):
        hidden_states = self.dense(hidden_states)
        hidden_states = self.dropout(hidden_states)
        return hidden_states


# Copied from transformers.models.segformer.modeling_segformer.SegformerAttention with Segformer->GLPN
class GLPNAttention(nn.Module):
    def __init__(self, config, hidden_size, num_attention_heads, sequence_reduction_ratio):
        super().__init__()
        self.self = GLPNEfficientSelfAttention(
            config=config,
            hidden_size=hidden_size,
            num_attention_heads=num_attention_heads,
            sequence_reduction_ratio=sequence_reduction_ratio,
        )
        self.output = GLPNSelfOutput(config, hidden_size=hidden_size)
        self.pruned_heads = set()

    def prune_heads(self, heads):
        if len(heads) == 0:
            return
        heads, index = find_pruneable_heads_and_indices(
            heads, self.self.num_attention_heads, self.self.attention_head_size, self.pruned_heads
        )

        # Prune linear layers
        self.self.query = prune_linear_layer(self.self.query, index)
        self.self.key = prune_linear_layer(self.self.key, index)
        self.self.value = prune_linear_layer(self.self.value, index)
        self.output.dense = prune_linear_layer(self.output.dense, index, dim=1)

        # Update hyper params and store pruned heads
        self.self.num_attention_heads = self.self.num_attention_heads - len(heads)
        self.self.all_head_size = self.self.attention_head_size * self.self.num_attention_heads
        self.pruned_heads = self.pruned_heads.union(heads)

    def forward(self, hidden_states, height, width, output_attentions=False):
        self_outputs = self.self(hidden_states, height, width, output_attentions)

        attention_output = self.output(self_outputs[0], hidden_states)
        outputs = (attention_output,) + self_outputs[1:]  # add attentions if we output them
        return outputs


# Copied from transformers.models.segformer.modeling_segformer.SegformerDWConv
class GLPNDWConv(nn.Module):
    def __init__(self, dim=768):
        super().__init__()
        self.dwconv = nn.Conv2d(dim, dim, 3, 1, 1, bias=True, groups=dim)

    def forward(self, hidden_states, height, width):
        batch_size, seq_len, num_channels = hidden_states.shape
        hidden_states = hidden_states.transpose(1, 2).view(batch_size, num_channels, height, width)
        hidden_states = self.dwconv(hidden_states)
        hidden_states = hidden_states.flatten(2).transpose(1, 2)

        return hidden_states


# Copied from transformers.models.segformer.modeling_segformer.SegformerMixFFN with Segformer->GLPN
class GLPNMixFFN(nn.Module):
    def __init__(self, config, in_features, hidden_features=None, out_features=None):
        super().__init__()
        out_features = out_features or in_features
        self.dense1 = nn.Linear(in_features, hidden_features)
        self.dwconv = GLPNDWConv(hidden_features)
        if isinstance(config.hidden_act, str):
            self.intermediate_act_fn = ACT2FN[config.hidden_act]
        else:
            self.intermediate_act_fn = config.hidden_act
        self.dense2 = nn.Linear(hidden_features, out_features)
        self.dropout = nn.Dropout(config.hidden_dropout_prob)

    def forward(self, hidden_states, height, width):
        hidden_states = self.dense1(hidden_states)
        hidden_states = self.dwconv(hidden_states, height, width)
        hidden_states = self.intermediate_act_fn(hidden_states)
        hidden_states = self.dropout(hidden_states)
        hidden_states = self.dense2(hidden_states)
        hidden_states = self.dropout(hidden_states)
        return hidden_states


# Copied from transformers.models.segformer.modeling_segformer.SegformerLayer with Segformer->GLPN
class GLPNLayer(nn.Module):
    """This corresponds to the Block class in the original implementation."""

    def __init__(self, config, hidden_size, num_attention_heads, drop_path, sequence_reduction_ratio, mlp_ratio):
        super().__init__()
        self.layer_norm_1 = nn.LayerNorm(hidden_size)
        self.attention = GLPNAttention(
            config,
            hidden_size=hidden_size,
            num_attention_heads=num_attention_heads,
            sequence_reduction_ratio=sequence_reduction_ratio,
        )
        self.drop_path = GLPNDropPath(drop_path) if drop_path > 0.0 else nn.Identity()
        self.layer_norm_2 = nn.LayerNorm(hidden_size)
        mlp_hidden_size = int(hidden_size * mlp_ratio)
        self.mlp = GLPNMixFFN(config, in_features=hidden_size, hidden_features=mlp_hidden_size)

    def forward(self, hidden_states, height, width, output_attentions=False):
        self_attention_outputs = self.attention(
            self.layer_norm_1(hidden_states),  # in GLPN, layernorm is applied before self-attention
            height,
            width,
            output_attentions=output_attentions,
        )

        attention_output = self_attention_outputs[0]
        outputs = self_attention_outputs[1:]  # add self attentions if we output attention weights

        # first residual connection (with stochastic depth)
        attention_output = self.drop_path(attention_output)
        hidden_states = attention_output + hidden_states

        mlp_output = self.mlp(self.layer_norm_2(hidden_states), height, width)

        # second residual connection (with stochastic depth)
        mlp_output = self.drop_path(mlp_output)
        layer_output = mlp_output + hidden_states

        outputs = (layer_output,) + outputs

        return outputs


class GLPNEncoder(nn.Module):
    def __init__(self, config):
        super().__init__()
        self.config = config

        # stochastic depth decay rule
        dpr = [x.item() for x in torch.linspace(0, config.drop_path_rate, sum(config.depths))]

        # patch embeddings
        embeddings = []
        for i in range(config.num_encoder_blocks):
            embeddings.append(
                GLPNOverlapPatchEmbeddings(
                    patch_size=config.patch_sizes[i],
                    stride=config.strides[i],
                    num_channels=config.num_channels if i == 0 else config.hidden_sizes[i - 1],
                    hidden_size=config.hidden_sizes[i],
                )
            )
        self.patch_embeddings = nn.ModuleList(embeddings)

        # Transformer blocks
        blocks = []
        cur = 0
        for i in range(config.num_encoder_blocks):
            # each block consists of layers
            layers = []
            if i != 0:
                cur += config.depths[i - 1]
            for j in range(config.depths[i]):
                layers.append(
                    GLPNLayer(
                        config,
                        hidden_size=config.hidden_sizes[i],
                        num_attention_heads=config.num_attention_heads[i],
                        drop_path=dpr[cur + j],
                        sequence_reduction_ratio=config.sr_ratios[i],
                        mlp_ratio=config.mlp_ratios[i],
                    )
                )
            blocks.append(nn.ModuleList(layers))

        self.block = nn.ModuleList(blocks)

        # Layer norms
        self.layer_norm = nn.ModuleList(
            [nn.LayerNorm(config.hidden_sizes[i]) for i in range(config.num_encoder_blocks)]
        )

    def forward(
        self,
        pixel_values,
        output_attentions=False,
        output_hidden_states=False,
        return_dict=True,
    ):
        all_hidden_states = () if output_hidden_states else None
        all_self_attentions = () if output_attentions else None

        batch_size = pixel_values.shape[0]

        hidden_states = pixel_values
        for idx, x in enumerate(zip(self.patch_embeddings, self.block, self.layer_norm)):
            embedding_layer, block_layer, norm_layer = x
            # first, obtain patch embeddings
            hidden_states, height, width = embedding_layer(hidden_states)
            # second, send embeddings through blocks
            for i, blk in enumerate(block_layer):
                layer_outputs = blk(hidden_states, height, width, output_attentions)
                hidden_states = layer_outputs[0]
                if output_attentions:
                    all_self_attentions = all_self_attentions + (layer_outputs[1],)
            # third, apply layer norm
            hidden_states = norm_layer(hidden_states)
            # fourth, optionally reshape back to (batch_size, num_channels, height, width)
            hidden_states = hidden_states.reshape(batch_size, height, width, -1).permute(0, 3, 1, 2).contiguous()
            if output_hidden_states:
                all_hidden_states = all_hidden_states + (hidden_states,)

        if not return_dict:
            return tuple(v for v in [hidden_states, all_hidden_states, all_self_attentions] if v is not None)
        return BaseModelOutput(
            last_hidden_state=hidden_states,
            hidden_states=all_hidden_states,
            attentions=all_self_attentions,
        )


class GLPNPreTrainedModel(PreTrainedModel):
    """
    An abstract class to handle weights initialization and a simple interface for downloading and loading pretrained
    models.
    """

    config_class = GLPNConfig
    base_model_prefix = "glpn"
    main_input_name = "pixel_values"

    # Copied from transformers.models.segformer.modeling_segformer.SegformerPreTrainedModel._init_weights
    def _init_weights(self, module):
        """Initialize the weights"""
        if isinstance(module, (nn.Linear, nn.Conv2d)):
            # Slightly different from the TF version which uses truncated_normal for initialization
            # cf https://github.com/pytorch/pytorch/pull/5617
            module.weight.data.normal_(mean=0.0, std=self.config.initializer_range)
            if module.bias is not None:
                module.bias.data.zero_()
        elif isinstance(module, nn.Embedding):
            module.weight.data.normal_(mean=0.0, std=self.config.initializer_range)
            if module.padding_idx is not None:
                module.weight.data[module.padding_idx].zero_()
        elif isinstance(module, nn.LayerNorm):
            module.bias.data.zero_()
            module.weight.data.fill_(1.0)


GLPN_START_DOCSTRING = r"""
    This model is a PyTorch [torch.nn.Module](https://pytorch.org/docs/stable/nn.html#torch.nn.Module) sub-class. Use
    it as a regular PyTorch Module and refer to the PyTorch documentation for all matter related to general usage and
    behavior.

    Parameters:
        config ([`GLPNConfig`]): Model configuration class with all the parameters of the model.
            Initializing with a config file does not load the weights associated with the model, only the
            configuration. Check out the [`~PreTrainedModel.from_pretrained`] method to load the model weights.
"""

GLPN_INPUTS_DOCSTRING = r"""

    Args:
        pixel_values (`torch.FloatTensor` of shape `(batch_size, num_channels, height, width)`):
            Pixel values. Padding will be ignored by default should you provide it. Pixel values can be obtained using
            [`GLPNFeatureExtractor`]. See [`GLPNFeatureExtractor.__call__`] for details.

        output_attentions (`bool`, *optional*):
            Whether or not to return the attentions tensors of all attention layers. See `attentions` under returned
            tensors for more detail.
        output_hidden_states (`bool`, *optional*):
            Whether or not to return the hidden states of all layers. See `hidden_states` under returned tensors for
            more detail.
        return_dict (`bool`, *optional*):
            Whether or not to return a [`~utils.ModelOutput`] instead of a plain tuple.
"""


@add_start_docstrings(
    "The bare GLPN encoder (Mix-Transformer) outputting raw hidden-states without any specific head on top.",
    GLPN_START_DOCSTRING,
)
class GLPNModel(GLPNPreTrainedModel):
    # Copied from transformers.models.segformer.modeling_segformer.SegformerModel.__init__ with Segformer->GLPN
    def __init__(self, config):
        super().__init__(config)
        self.config = config

        # hierarchical Transformer encoder
        self.encoder = GLPNEncoder(config)

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

    def _prune_heads(self, heads_to_prune):
        """
        Prunes heads of the model. heads_to_prune: dict of {layer_num: list of heads to prune in this layer} See base
        class PreTrainedModel
        """
        for layer, heads in heads_to_prune.items():
            self.encoder.layer[layer].attention.prune_heads(heads)

    @add_start_docstrings_to_model_forward(GLPN_INPUTS_DOCSTRING.format("(batch_size, sequence_length)"))
    @add_code_sample_docstrings(
        processor_class=_FEAT_EXTRACTOR_FOR_DOC,
        checkpoint=_CHECKPOINT_FOR_DOC,
        output_type=BaseModelOutput,
        config_class=_CONFIG_FOR_DOC,
        modality="vision",
        expected_output=_EXPECTED_OUTPUT_SHAPE,
    )
    # Copied from transformers.models.segformer.modeling_segformer.SegformerModel.forward
    def forward(
        self,
        pixel_values: torch.FloatTensor,
        output_attentions: Optional[bool] = None,
        output_hidden_states: Optional[bool] = None,
        return_dict: Optional[bool] = None,
    ) -> Union[Tuple, BaseModelOutput]:
        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

        encoder_outputs = self.encoder(
            pixel_values,
            output_attentions=output_attentions,
            output_hidden_states=output_hidden_states,
            return_dict=return_dict,
        )
        sequence_output = encoder_outputs[0]

        if not return_dict:
            return (sequence_output,) + encoder_outputs[1:]

        return BaseModelOutput(
            last_hidden_state=sequence_output,
            hidden_states=encoder_outputs.hidden_states,
            attentions=encoder_outputs.attentions,
        )


class GLPNSelectiveFeatureFusion(nn.Module):
    """
    Selective Feature Fusion module, as explained in the [paper](https://arxiv.org/abs/2201.07436) (section 3.4). This
    module adaptively selects and integrates local and global features by attaining an attention map for each feature.
    """

    def __init__(self, in_channel=64):
        super().__init__()

        self.convolutional_layer1 = nn.Sequential(
            nn.Conv2d(in_channels=int(in_channel * 2), out_channels=in_channel, kernel_size=3, stride=1, padding=1),
            nn.BatchNorm2d(in_channel),
            nn.ReLU(),
        )

        self.convolutional_layer2 = nn.Sequential(
            nn.Conv2d(in_channels=in_channel, out_channels=int(in_channel / 2), kernel_size=3, stride=1, padding=1),
            nn.BatchNorm2d(int(in_channel / 2)),
            nn.ReLU(),
        )

        self.convolutional_layer3 = nn.Conv2d(
            in_channels=int(in_channel / 2), out_channels=2, kernel_size=3, stride=1, padding=1
        )

        self.sigmoid = nn.Sigmoid()

    def forward(self, local_features, global_features):
        # concatenate features along the channel dimension
        features = torch.cat((local_features, global_features), dim=1)
        # pass through convolutional layers
        features = self.convolutional_layer1(features)
        features = self.convolutional_layer2(features)
        features = self.convolutional_layer3(features)
        # apply sigmoid to get two-channel attention map
        attn = self.sigmoid(features)
        # construct hybrid features by adding element-wise
        hybrid_features = local_features * attn[:, 0, :, :].unsqueeze(1) + global_features * attn[
            :, 1, :, :
        ].unsqueeze(1)

        return hybrid_features


class GLPNDecoderStage(nn.Module):
    def __init__(self, in_channels, out_channels):
        super().__init__()
        should_skip = in_channels == out_channels
        self.convolution = nn.Conv2d(in_channels, out_channels, kernel_size=1) if not should_skip else nn.Identity()
        self.fusion = GLPNSelectiveFeatureFusion(out_channels)
        self.upsample = nn.Upsample(scale_factor=2, mode="bilinear", align_corners=False)

    def forward(self, hidden_state, residual=None):
        hidden_state = self.convolution(hidden_state)
        if residual is not None:
            hidden_state = self.fusion(hidden_state, residual)
        hidden_state = self.upsample(hidden_state)

        return hidden_state

        hidden_state = self.upsample(hidden_state)
        return hidden_state


class GLPNDecoder(nn.Module):
    def __init__(self, config):
        super().__init__()
        # we use features from end -> start
        reserved_hidden_sizes = config.hidden_sizes[::-1]
        out_channels = config.decoder_hidden_size

        self.stages = nn.ModuleList(
            [GLPNDecoderStage(hidden_size, out_channels) for hidden_size in reserved_hidden_sizes]
        )
        # don't fuse in first stage
        self.stages[0].fusion = None

        self.final_upsample = nn.Upsample(scale_factor=2, mode="bilinear", align_corners=False)

    def forward(self, hidden_states: List[torch.Tensor]) -> List[torch.Tensor]:
        stage_hidden_states = []
        stage_hidden_state = None
        for hidden_state, stage in zip(hidden_states[::-1], self.stages):
            stage_hidden_state = stage(hidden_state, stage_hidden_state)
            stage_hidden_states.append(stage_hidden_state)

        stage_hidden_states[-1] = self.final_upsample(stage_hidden_state)

        return stage_hidden_states


class SiLogLoss(nn.Module):
    """
    Implements the Scale-invariant log scale loss [Eigen et al., 2014](https://arxiv.org/abs/1406.2283).

    $$L=\frac{1}{n} \sum_{i} d_{i}^{2}-\frac{1}{2 n^{2}}\left(\sum_{i} d_{i}^{2}\right)$$ where $d_{i}=\log y_{i}-\log
    y_{i}^{*}$.

    """

    def __init__(self, lambd=0.5):
        super().__init__()
        self.lambd = lambd

    def forward(self, pred, target):
        valid_mask = (target > 0).detach()
        diff_log = torch.log(target[valid_mask]) - torch.log(pred[valid_mask])
        loss = torch.sqrt(torch.pow(diff_log, 2).mean() - self.lambd * torch.pow(diff_log.mean(), 2))

        return loss


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

        self.config = config

        channels = config.decoder_hidden_size
        self.head = nn.Sequential(
            nn.Conv2d(channels, channels, kernel_size=3, stride=1, padding=1),
            nn.ReLU(inplace=False),
            nn.Conv2d(channels, 1, kernel_size=3, stride=1, padding=1),
        )

    def forward(self, hidden_states: List[torch.Tensor]) -> torch.Tensor:
        # use last features of the decoder
        hidden_states = hidden_states[self.config.head_in_index]

        hidden_states = self.head(hidden_states)

        predicted_depth = torch.sigmoid(hidden_states) * self.config.max_depth
        predicted_depth = predicted_depth.squeeze(dim=1)

        return predicted_depth


@add_start_docstrings(
    """GLPN Model transformer with a lightweight depth estimation head on top e.g. for KITTI, NYUv2.""",
    GLPN_START_DOCSTRING,
)
class GLPNForDepthEstimation(GLPNPreTrainedModel):
    def __init__(self, config):
        super().__init__(config)

        self.glpn = GLPNModel(config)
        self.decoder = GLPNDecoder(config)
        self.head = GLPNDepthEstimationHead(config)

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

    @add_start_docstrings_to_model_forward(GLPN_INPUTS_DOCSTRING.format("batch_size, sequence_length"))
    @replace_return_docstrings(output_type=DepthEstimatorOutput, config_class=_CONFIG_FOR_DOC)
    def forward(
        self,
        pixel_values,
        labels=None,
        output_attentions=None,
        output_hidden_states=None,
        return_dict=None,
    ):
        r"""
        labels (`torch.FloatTensor` of shape `(batch_size, height, width)`, *optional*):
            Ground truth depth estimation maps for computing the loss.

        Returns:

        Examples:

        ```python
        >>> from transformers import GLPNFeatureExtractor, GLPNForDepthEstimation
        >>> import torch
        >>> import numpy as np
        >>> from PIL import Image
        >>> import requests

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

        >>> feature_extractor = GLPNFeatureExtractor.from_pretrained("vinvino02/glpn-kitti")
        >>> model = GLPNForDepthEstimation.from_pretrained("vinvino02/glpn-kitti")

        >>> # prepare image for the model
        >>> inputs = feature_extractor(images=image, return_tensors="pt")

        >>> with torch.no_grad():
        ...     outputs = model(**inputs)
        ...     predicted_depth = outputs.predicted_depth

        >>> # interpolate to original size
        >>> prediction = torch.nn.functional.interpolate(
        ...     predicted_depth.unsqueeze(1),
        ...     size=image.size[::-1],
        ...     mode="bicubic",
        ...     align_corners=False,
        ... )

        >>> # visualize the prediction
        >>> output = prediction.squeeze().cpu().numpy()
        >>> formatted = (output * 255 / np.max(output)).astype("uint8")
        >>> depth = Image.fromarray(formatted)
        ```"""
        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.glpn(
            pixel_values,
            output_attentions=output_attentions,
            output_hidden_states=True,  # we need the intermediate hidden states
            return_dict=return_dict,
        )

        hidden_states = outputs.hidden_states if return_dict else outputs[1]

        out = self.decoder(hidden_states)
        predicted_depth = self.head(out)

        loss = None
        if labels is not None:
            loss_fct = SiLogLoss()
            loss = loss_fct(predicted_depth, labels)

        if not return_dict:
            if output_hidden_states:
                output = (predicted_depth,) + outputs[1:]
            else:
                output = (predicted_depth,) + outputs[2:]
            return ((loss,) + output) if loss is not None else output

        return DepthEstimatorOutput(
            loss=loss,
            predicted_depth=predicted_depth,
            hidden_states=outputs.hidden_states if output_hidden_states else None,
            attentions=outputs.attentions,
        )
