# SPDX-FileCopyrightText: Copyright (c) 2023 - 2024 NVIDIA CORPORATION & AFFILIATES.
# SPDX-FileCopyrightText: All rights reserved.
# SPDX-License-Identifier: Apache-2.0
#
# 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.

"""
This is the datapipe to read OpenFoam files (vtp/vtu/stl) and save them as point clouds 
in npy format. 

"""

import time, random
from collections import defaultdict
from pathlib import Path
from typing import Any, Iterable, List, Literal, Mapping, Optional, Union, Callable

import numpy as np
import pandas as pd
import pyvista as pv
import vtk
from torch.utils.data import Dataset
import os
from vtk.util import numpy_support


def get_filenames(filepath: str) -> List[str]:
    """Function to get filenames from a directory"""
    if os.path.exists(filepath):
        filenames = []
        for item in os.listdir(filepath):
            filenames.append(item)
        return filenames
    else:
        FileNotFoundError()

def get_node_to_elem(polydata: Any) -> Any:
    """Function to convert node to elem"""
    c2p = vtk.vtkPointDataToCellData()
    c2p.SetInputData(polydata)
    c2p.Update()
    cell_data = c2p.GetOutput()
    return cell_data

def get_fields(data, variables):
    """Function to get fields from VTP/VTU"""
    fields = []
    for array_name in variables:
        try:
            array = data.GetArray(array_name)
        except ValueError:
            raise ValueError(
                f"Failed to get array {array_name} from the unstructured grid."
            )
        array_data = numpy_support.vtk_to_numpy(array).reshape(
            array.GetNumberOfTuples(), array.GetNumberOfComponents()
        )
        fields.append(array_data)
    return fields




class DrivAerAwsPaths:
    @staticmethod
    def _get_index(car_dir: Path) -> str:
        return car_dir.name.removeprefix("run_")

    @staticmethod
    def geometry_path(car_dir: Path) -> Path:
        return car_dir / f"drivaer_{DrivAerAwsPaths._get_index(car_dir)}.stl"

    @staticmethod
    def volume_path(car_dir: Path) -> Path:
        return car_dir / f"volume_{DrivAerAwsPaths._get_index(car_dir)}.vtu"

    @staticmethod
    def surface_path(car_dir: Path) -> Path:
        return car_dir / f"boundary_{DrivAerAwsPaths._get_index(car_dir)}.vtp"


class OpenFoamDataset(Dataset):
    """
    Datapipe for converting openfoam dataset to npy

    """

    def __init__(
        self,
        data_path: Union[str, Path],
        surface_variables: Optional[list] = [
            "pMean",
            "wallShearStress",
        ],
        volume_variables: Optional[list] = ["UMean", "pMean"],
        model_type=None,
    ):
        if isinstance(data_path, str):
            data_path = Path(data_path)
        data_path = data_path.expanduser()

        self.data_path = data_path

        self.path_getter = DrivAerAwsPaths

        assert self.data_path.exists(), f"Path {self.data_path} does not exist"

        assert self.data_path.is_dir(), f"Path {self.data_path} is not a directory"

        self.filenames = get_filenames(self.data_path)
        random.shuffle(self.filenames)
        self.indices = np.array(len(self.filenames))

        self.surface_variables = surface_variables
        self.volume_variables = volume_variables
        self.model_type = model_type

    def __len__(self):
        return len(self.filenames)

    def __getitem__(self, idx):
        cfd_filename = self.filenames[idx]
        car_dir = self.data_path / cfd_filename


        if self.model_type == "surface":
            surface_filepath = self.path_getter.surface_path(car_dir)
            reader = vtk.vtkXMLPolyDataReader()
            reader.SetFileName(surface_filepath)
            reader.Update()
            polydata = reader.GetOutput()

            celldata_all = get_node_to_elem(polydata)
            celldata = celldata_all.GetCellData()
            surface_fields = get_fields(celldata, self.surface_variables)
            surface_fields = np.concatenate(surface_fields, axis=-1)

            mesh = pv.PolyData(polydata)
            surface_coordinates = np.array(mesh.cell_centers().points)


        else:
            surface_fields = None
            surface_coordinates = None

        # Add the parameters to the dictionary
        return {
            "surface_mesh_centers": np.float32(surface_coordinates),
            "surface_fields": np.float32(surface_fields),
        }