# Copyright 2022 The Plenoptix 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
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"""Fields for nerf-w"""

from typing import Dict, Optional, Tuple

import torch
from torch import nn
from torchtyping import TensorType

from nerfstudio.cameras.rays import RaySamples
from nerfstudio.fields.base import Field
from nerfstudio.fields.modules.embedding import Embedding
from nerfstudio.fields.modules.encoding import Encoding, Identity
from nerfstudio.fields.modules.field_heads import (
    DensityFieldHead,
    FieldHeadNames,
    RGBFieldHead,
    TransientDensityFieldHead,
    TransientRGBFieldHead,
    UncertaintyFieldHead,
)
from nerfstudio.fields.modules.mlp import MLP


class VanillaNerfWField(Field):
    """The NeRF-W field which has appearance and transient conditioning.

    Args:
        num_images: How many images exist in the dataset.
        position_encoding: Position encoder.
        direction_encoding: Direction encoder.
        base_mlp_num_layers: Number of layers for base MLP.
        base_mlp_layer_width: Width of base MLP layers.
        head_mlp_num_layers: Number of layer for ourput head MLP.
        head_mlp_layer_width: Width of output head MLP layers.
        appearance_embedding_dim:: Dimension of appearance embedding.
        transient_embedding_dim:: Dimension of transient embedding.
        skip_connections: Where to add skip connection in base MLP.
    """

    def __init__(
        self,
        num_images: int,
        position_encoding: Encoding = Identity(in_dim=3),
        direction_encoding: Encoding = Identity(in_dim=3),
        base_mlp_num_layers: int = 8,
        base_mlp_layer_width: int = 256,
        head_mlp_num_layers: int = 2,
        head_mlp_layer_width: int = 128,
        appearance_embedding_dim: int = 48,
        transient_embedding_dim: int = 16,
        skip_connections: Tuple[int] = (4,),
    ) -> None:
        super().__init__()
        self.num_images = num_images
        self.position_encoding = position_encoding
        self.direction_encoding = direction_encoding
        self.base_mlp_num_layers = base_mlp_num_layers
        self.base_mlp_layer_width = base_mlp_layer_width
        self.head_mlp_num_layers = head_mlp_num_layers
        self.head_mlp_layer_width = head_mlp_layer_width
        self.appearance_embedding_dim = appearance_embedding_dim
        self.transient_embedding_dim = transient_embedding_dim

        self.embedding_appearance = Embedding(self.num_images, self.appearance_embedding_dim)
        self.embedding_transient = Embedding(self.num_images, self.transient_embedding_dim)

        self.mlp_base = MLP(
            in_dim=self.position_encoding.get_out_dim(),
            num_layers=base_mlp_num_layers,
            layer_width=base_mlp_layer_width,
            skip_connections=skip_connections,
        )
        self.mlp_transient = MLP(
            in_dim=self.mlp_base.get_out_dim() + self.embedding_transient.get_out_dim(),
            out_dim=base_mlp_layer_width // 2,
            num_layers=4,
            layer_width=base_mlp_layer_width,
            activation=nn.ReLU(),
        )
        self.mlp_head = MLP(
            in_dim=self.mlp_base.get_out_dim()
            + self.direction_encoding.get_out_dim()
            + self.embedding_appearance.get_out_dim(),
            num_layers=head_mlp_num_layers,
            layer_width=head_mlp_layer_width,
        )

        self.field_head_density = DensityFieldHead(in_dim=self.mlp_base.get_out_dim())
        self.field_head_rgb = RGBFieldHead(in_dim=self.mlp_head.get_out_dim())

        self.field_head_transient_uncertainty = UncertaintyFieldHead(in_dim=self.mlp_transient.get_out_dim())
        self.field_head_transient_rgb = TransientRGBFieldHead(in_dim=self.mlp_transient.get_out_dim())
        self.field_head_transient_density = TransientDensityFieldHead(in_dim=self.mlp_transient.get_out_dim())

    def get_density(self, ray_samples: RaySamples):
        """Computes and returns the densities."""
        encoded_xyz = self.position_encoding(ray_samples.frustums.get_positions())
        encoded_xyz = self.position_encoding(ray_samples.frustums.get_positions())
        base_mlp_out = self.mlp_base(encoded_xyz)
        density = self.field_head_density(base_mlp_out)
        return density, base_mlp_out

    def get_outputs(
        self, ray_samples: RaySamples, density_embedding: Optional[TensorType[..., "embedding_size"]] = None
    ) -> Dict[FieldHeadNames, TensorType]:
        """Returns the outputs of the NeRF-W field.

        Args:
            ray_samples (RaySamples): Ray samples.
            density_embedding (TensorType[..., "embedding_size"], optional): Density embedding.

        Returns:
            Dict[FieldHeadNames, TensorType]: Outputs of the NeRF-W field.
        """
        outputs = {}
        encoded_dir = self.direction_encoding(ray_samples.frustums.directions)
        if ray_samples.camera_indices is None:
            raise AttributeError("Camera indices are not provided.")
        camera_indices = ray_samples.camera_indices.squeeze().to(ray_samples.frustums.origins.device)
        embedded_appearance = self.embedding_appearance(camera_indices)
        mlp_in = torch.cat([density_embedding, encoded_dir, embedded_appearance], dim=-1)  # type: ignore
        mlp_head_out = self.mlp_head(mlp_in)
        outputs[self.field_head_rgb.field_head_name] = self.field_head_rgb(mlp_head_out)  # static rgb
        embedded_transient = self.embedding_transient(camera_indices)
        transient_mlp_in = torch.cat([density_embedding, embedded_transient], dim=-1)  # type: ignore
        transient_mlp_out = self.mlp_transient(transient_mlp_in)
        outputs[self.field_head_transient_uncertainty.field_head_name] = self.field_head_transient_uncertainty(
            transient_mlp_out
        )  # uncertainty
        outputs[self.field_head_transient_rgb.field_head_name] = self.field_head_transient_rgb(
            transient_mlp_out
        )  # transient rgb
        outputs[self.field_head_transient_density.field_head_name] = self.field_head_transient_density(
            transient_mlp_out
        )  # transient density
        return outputs
