# Copyright (c) Meta Platforms, Inc. and affiliates.
# All rights reserved.
#
# This source code is licensed under the BSD-style license found in the
# LICENSE file in the root directory of this source tree.


"""
This module implements utility functions for loading and saving
meshes and point clouds as PLY files.
"""
import itertools
import struct
import sys
import warnings
from collections import namedtuple
from dataclasses import asdict, dataclass
from io import BytesIO, TextIOBase
from typing import List, Optional, Tuple

import numpy as np
import torch
from iopath.common.file_io import PathManager
from pytorch3d.io.utils import _check_faces_indices, _make_tensor, _open_file, PathOrStr
from pytorch3d.renderer import TexturesVertex
from pytorch3d.structures import Meshes, Pointclouds

from .pluggable_formats import (
    endswith,
    MeshFormatInterpreter,
    PointcloudFormatInterpreter,
)


_PlyTypeData = namedtuple("_PlyTypeData", "size struct_char np_type")

_PLY_TYPES = {
    "char": _PlyTypeData(1, "b", np.byte),
    "uchar": _PlyTypeData(1, "B", np.ubyte),
    "short": _PlyTypeData(2, "h", np.short),
    "ushort": _PlyTypeData(2, "H", np.ushort),
    "int": _PlyTypeData(4, "i", np.int32),
    "uint": _PlyTypeData(4, "I", np.uint32),
    "float": _PlyTypeData(4, "f", np.float32),
    "double": _PlyTypeData(8, "d", np.float64),
    "int8": _PlyTypeData(1, "b", np.byte),
    "uint8": _PlyTypeData(1, "B", np.ubyte),
    "int16": _PlyTypeData(2, "h", np.short),
    "uint16": _PlyTypeData(2, "H", np.ushort),
    "int32": _PlyTypeData(4, "i", np.int32),
    "uint32": _PlyTypeData(4, "I", np.uint32),
    "float32": _PlyTypeData(4, "f", np.float32),
    "float64": _PlyTypeData(8, "d", np.float64),
}

_Property = namedtuple("_Property", "name data_type list_size_type")


class _PlyElementType:
    """
    Description of an element of a Ply file.
    Members:
        self.properties: (List[_Property]) description of all the properties.
                            Each one contains a name and data type.
        self.count:      (int) number of such elements in the file
        self.name:       (str) name of the element
    """

    def __init__(self, name: str, count: int) -> None:
        self.name = name
        self.count = count
        self.properties: List[_Property] = []

    def add_property(
        self, name: str, data_type: str, list_size_type: Optional[str] = None
    ):
        """Adds a new property.

        Args:
            name:           (str) name of the property.
            data_type:      (str) PLY data type.
            list_size_type: (str) PLY data type of the list size, or None if not
                            a list.
        """
        for property in self.properties:
            if property.name == name:
                msg = "Cannot have two properties called %s in %s."
                raise ValueError(msg % (name, self.name))
        self.properties.append(_Property(name, data_type, list_size_type))

    def is_fixed_size(self) -> bool:
        """Return whether the Element has no list properties

        Returns:
            True if none of the properties are lists.
        """
        for property in self.properties:
            if property.list_size_type is not None:
                return False
        return True

    def is_constant_type_fixed_size(self) -> bool:
        """Return whether the Element has all properties of the same non-list
        type.

        Returns:
            True if none of the properties are lists and all the properties
            share a type.
        """
        if not self.is_fixed_size():
            return False
        first_type = _PLY_TYPES[self.properties[0].data_type]
        for property in self.properties:
            if _PLY_TYPES[property.data_type] != first_type:
                return False
        return True

    def try_constant_list(self) -> bool:
        """Whether the element is just a single list, which might have a
        constant size, and therefore we could try to parse quickly with numpy.

        Returns:
            True if the only property is a list.
        """
        if len(self.properties) != 1:
            return False
        if self.properties[0].list_size_type is None:
            return False
        return True


class _PlyHeader:
    def __init__(self, f) -> None:
        """
        Load a header of a Ply file from a file-like object.
        Members:
            self.elements:   (List[_PlyElementType]) element description
            self.ascii:      (bool) Whether in ascii format
            self.big_endian: (bool) (if not ascii) whether big endian
            self.obj_info:   (List[str]) arbitrary extra data
            self.comments:   (List[str]) comments

        Args:
            f: file-like object.
        """
        if f.readline() not in [b"ply\n", b"ply\r\n", "ply\n"]:
            raise ValueError("Invalid file header.")
        seen_format = False
        self.elements: List[_PlyElementType] = []
        self.comments: List[str] = []
        self.obj_info: List[str] = []
        while True:
            line = f.readline()
            if isinstance(line, bytes):
                line = line.decode("ascii")
            line = line.strip()
            if line == "end_header":
                if not self.elements:
                    raise ValueError("No elements found.")
                if not self.elements[-1].properties:
                    raise ValueError("Found an element with no properties.")
                if not seen_format:
                    raise ValueError("No format line found.")
                break
            if not seen_format:
                if line == "format ascii 1.0":
                    seen_format = True
                    self.ascii = True
                    continue
                if line == "format binary_little_endian 1.0":
                    seen_format = True
                    self.ascii = False
                    self.big_endian = False
                    continue
                if line == "format binary_big_endian 1.0":
                    seen_format = True
                    self.ascii = False
                    self.big_endian = True
                    continue
            if line.startswith("format"):
                raise ValueError("Invalid format line.")
            if line.startswith("comment "):
                self.comments.append(line[8:])
                continue
            if line.startswith("comment") or len(line) == 0:
                continue
            if line.startswith("element"):
                self._parse_element(line)
                continue
            if line.startswith("obj_info "):
                self.obj_info.append(line[9:])
                continue
            if line.startswith("property"):
                self._parse_property(line)
                continue
            raise ValueError("Invalid line: %s." % line)

    def _parse_property(self, line: str):
        """
        Decode a ply file header property line.

        Args:
            line: (str) the ply file's line.
        """
        if not self.elements:
            raise ValueError("Encountered property before any element.")
        items = line.split(" ")
        if len(items) not in [3, 5]:
            raise ValueError("Invalid line: %s" % line)
        datatype = items[1]
        name = items[-1]
        if datatype == "list":
            datatype = items[3]
            list_size_type = items[2]
            if list_size_type not in _PLY_TYPES:
                raise ValueError("Invalid datatype: %s" % list_size_type)
        else:
            list_size_type = None
        if datatype not in _PLY_TYPES:
            raise ValueError("Invalid datatype: %s" % datatype)
        self.elements[-1].add_property(name, datatype, list_size_type)

    def _parse_element(self, line: str):
        """
        Decode a ply file header element line.

        Args:
            line: (str) the ply file's line.
        """
        if self.elements and not self.elements[-1].properties:
            raise ValueError("Found an element with no properties.")
        items = line.split(" ")
        if len(items) != 3:
            raise ValueError("Invalid line: %s" % line)
        try:
            count = int(items[2])
        except ValueError:
            msg = "Number of items for %s was not a number."
            raise ValueError(msg % items[1])
        self.elements.append(_PlyElementType(items[1], count))


def _read_ply_fixed_size_element_ascii(f, definition: _PlyElementType):
    """
    Given an element which has no lists and one type, read the
    corresponding data.

    For example

        element vertex 8
        property float x
        property float y
        property float z

    Args:
        f: file-like object being read.
        definition: The element object which describes what we are reading.

    Returns:
        1-element list containing a 2D numpy array corresponding to the data.
        The rows are the different values. There is one column for each property.
    """
    np_type = _PLY_TYPES[definition.properties[0].data_type].np_type
    old_offset = f.tell()
    with warnings.catch_warnings():
        warnings.filterwarnings(
            "ignore", message=".* Empty input file.*", category=UserWarning
        )
        data = np.loadtxt(
            f, dtype=np_type, comments=None, ndmin=2, max_rows=definition.count
        )
    if not len(data):  # np.loadtxt() seeks even on empty data
        f.seek(old_offset)
    if data.shape[1] != len(definition.properties):
        raise ValueError("Inconsistent data for %s." % definition.name)
    if data.shape[0] != definition.count:
        raise ValueError("Not enough data for %s." % definition.name)
    return [data]


def _read_ply_nolist_element_ascii(f, definition: _PlyElementType):
    """
    Given an element which has no lists and multiple types, read the
    corresponding data, by loading all the data as float64 and converting
    the relevant parts later.

    For example, given

        element vertex 8
        property float x
        property float y
        property float z
        property uchar red
        property uchar green
        property uchar blue

    the output will have two arrays, the first containing (x,y,z)
    and the second (red,green,blue).

    Args:
        f: file-like object being read.
        definition: The element object which describes what we are reading.

    Returns:
        List of 2D numpy arrays corresponding to the data.
    """
    old_offset = f.tell()
    with warnings.catch_warnings():
        warnings.filterwarnings(
            "ignore", message=".* Empty input file.*", category=UserWarning
        )
        data = np.loadtxt(
            f, dtype=np.float64, comments=None, ndmin=2, max_rows=definition.count
        )
    if not len(data):  # np.loadtxt() seeks even on empty data
        f.seek(old_offset)
    if data.shape[1] != len(definition.properties):
        raise ValueError("Inconsistent data for %s." % definition.name)
    if data.shape[0] != definition.count:
        raise ValueError("Not enough data for %s." % definition.name)
    pieces = []
    offset = 0
    for dtype, it in itertools.groupby(p.data_type for p in definition.properties):
        count = sum(1 for _ in it)
        end_offset = offset + count
        piece = data[:, offset:end_offset].astype(_PLY_TYPES[dtype].np_type)
        pieces.append(piece)
        offset = end_offset
    return pieces


def _try_read_ply_constant_list_ascii(f, definition: _PlyElementType):
    """
    If definition is an element which is a single list, attempt to read the
    corresponding data assuming every value has the same length.
    If the data is ragged, return None and leave f undisturbed.

    For example, if the element is

        element face 2
        property list uchar int vertex_index

    and the data is

        4 0 1 2 3
        4 7 6 5 4

    then the function will return

        [[0, 1, 2, 3],
         [7, 6, 5, 4]]

    but if the data is

        4 0 1 2 3
        3 6 5 4

    then the function will return None.

    Args:
        f: file-like object being read.
        definition: The element object which describes what we are reading.

    Returns:
        If every element has the same size, 2D numpy array corresponding to the
        data. The rows are the different values. Otherwise None.
    """
    np_type = _PLY_TYPES[definition.properties[0].data_type].np_type
    old_offset = f.tell()
    try:
        with warnings.catch_warnings():
            warnings.filterwarnings(
                "ignore", message=".* Empty input file.*", category=UserWarning
            )
            data = np.loadtxt(
                f, dtype=np_type, comments=None, ndmin=2, max_rows=definition.count
            )
    except ValueError:
        f.seek(old_offset)
        return None
    if not len(data):  # np.loadtxt() seeks even on empty data
        f.seek(old_offset)
    if (data[:, 0] != data.shape[1] - 1).any():
        msg = "A line of %s data did not have the specified length."
        raise ValueError(msg % definition.name)
    if data.shape[0] != definition.count:
        raise ValueError("Not enough data for %s." % definition.name)
    return data[:, 1:]


def _parse_heterogeneous_property_ascii(datum, line_iter, property: _Property):
    """
    Read a general data property from an ascii .ply file.

    Args:
        datum: list to append the single value to. That value will be a numpy
                array if the property is a list property, otherwise an int or
                float.
        line_iter: iterator to words on the line from which we read.
        property: the property object describing the property we are reading.
    """
    value = next(line_iter, None)
    if value is None:
        raise ValueError("Too little data for an element.")
    if property.list_size_type is None:
        try:
            if property.data_type in ["double", "float"]:
                datum.append(float(value))
            else:
                datum.append(int(value))
        except ValueError:
            raise ValueError("Bad numerical data.")
    else:
        try:
            length = int(value)
        except ValueError:
            raise ValueError("A list length was not a number.")
        list_value = np.zeros(length, dtype=_PLY_TYPES[property.data_type].np_type)
        for i in range(length):
            inner_value = next(line_iter, None)
            if inner_value is None:
                raise ValueError("Too little data for an element.")
            try:
                list_value[i] = float(inner_value)
            except ValueError:
                raise ValueError("Bad numerical data.")
        datum.append(list_value)


def _read_ply_element_ascii(f, definition: _PlyElementType):
    """
    Decode all instances of a single element from an ascii .ply file.

    Args:
        f: file-like object being read.
        definition: The element object which describes what we are reading.

    Returns:
        In simple cases where every element has the same size, 2D numpy array
        corresponding to the data. The rows are the different values.
        Otherwise a list of lists of values, where the outer list is
        each occurrence of the element, and the inner lists have one value per
        property.
    """
    if not definition.count:
        return []
    if definition.is_constant_type_fixed_size():
        return _read_ply_fixed_size_element_ascii(f, definition)
    if definition.is_fixed_size():
        return _read_ply_nolist_element_ascii(f, definition)
    if definition.try_constant_list():
        data = _try_read_ply_constant_list_ascii(f, definition)
        if data is not None:
            return data

    # We failed to read the element as a lump, must process each line manually.
    data = []
    for _i in range(definition.count):
        line_string = f.readline()
        if line_string == "":
            raise ValueError("Not enough data for %s." % definition.name)
        datum = []
        line_iter = iter(line_string.strip().split())
        for property in definition.properties:
            _parse_heterogeneous_property_ascii(datum, line_iter, property)
        data.append(datum)
        if next(line_iter, None) is not None:
            raise ValueError("Too much data for an element.")
    return data


def _read_raw_array(
    f, aim: str, length: int, dtype: type = np.uint8, dtype_size: int = 1
):
    """
    Read [length] elements from a file.

    Args:
        f: file object
        aim: name of target for error message
        length: number of elements
        dtype: numpy type
        dtype_size: number of bytes per element.

    Returns:
        new numpy array
    """

    if isinstance(f, BytesIO):
        # np.fromfile is faster but won't work on a BytesIO
        needed_bytes = length * dtype_size
        bytes_data = bytearray(needed_bytes)
        n_bytes_read = f.readinto(bytes_data)
        if n_bytes_read != needed_bytes:
            raise ValueError("Not enough data for %s." % aim)
        data = np.frombuffer(bytes_data, dtype=dtype)
    else:
        data = np.fromfile(f, dtype=dtype, count=length)
        if data.shape[0] != length:
            raise ValueError("Not enough data for %s." % aim)
    return data


def _read_ply_fixed_size_element_binary(
    f, definition: _PlyElementType, big_endian: bool
):
    """
    Given an element which has no lists and one type, read the
    corresponding data.

    For example

        element vertex 8
        property float x
        property float y
        property float z


    Args:
        f: file-like object being read.
        definition: The element object which describes what we are reading.
        big_endian: (bool) whether the document is encoded as big endian.

    Returns:
        1-element list containing a 2D numpy array corresponding to the data.
        The rows are the different values. There is one column for each property.
    """
    ply_type = _PLY_TYPES[definition.properties[0].data_type]
    np_type = ply_type.np_type
    type_size = ply_type.size
    needed_length = definition.count * len(definition.properties)
    data = _read_raw_array(f, definition.name, needed_length, np_type, type_size)

    if (sys.byteorder == "big") != big_endian:
        data = data.byteswap()
    return [data.reshape(definition.count, len(definition.properties))]


def _read_ply_element_binary_nolists(f, definition: _PlyElementType, big_endian: bool):
    """
    Given an element which has no lists, read the corresponding data as tuple
    of numpy arrays, one for each set of adjacent columns with the same type.

    For example, given

        element vertex 8
        property float x
        property float y
        property float z
        property uchar red
        property uchar green
        property uchar blue

    the output will have two arrays, the first containing (x,y,z)
    and the second (red,green,blue).

    Args:
        f: file-like object being read.
        definition: The element object which describes what we are reading.
        big_endian: (bool) whether the document is encoded as big endian.

    Returns:
        List of 2D numpy arrays corresponding to the data. The rows are the different
        values.
    """
    size = sum(_PLY_TYPES[prop.data_type].size for prop in definition.properties)
    needed_bytes = size * definition.count
    data = _read_raw_array(f, definition.name, needed_bytes).reshape(-1, size)
    offset = 0
    pieces = []
    for dtype, it in itertools.groupby(p.data_type for p in definition.properties):
        count = sum(1 for _ in it)
        bytes_each = count * _PLY_TYPES[dtype].size
        end_offset = offset + bytes_each

        # what we want to do is
        # piece = data[:, offset:end_offset].view(_PLY_TYPES[dtype].np_type)
        # but it fails in the general case
        # because of https://github.com/numpy/numpy/issues/9496.
        piece = np.lib.stride_tricks.as_strided(
            data[:1, offset:end_offset].view(_PLY_TYPES[dtype].np_type),
            shape=(definition.count, count),
            strides=(data.strides[0], _PLY_TYPES[dtype].size),
        )

        if (sys.byteorder == "big") != big_endian:
            piece = piece.byteswap()
        pieces.append(piece)
        offset = end_offset
    return pieces


def _try_read_ply_constant_list_binary(
    f, definition: _PlyElementType, big_endian: bool
):
    """
    If definition is an element which is a single list, attempt to read the
    corresponding data assuming every value has the same length.
    If the data is ragged, return None and leave f undisturbed.

    For example, if the element is

        element face 2
        property list uchar int vertex_index

    and the data is

        4 0 1 2 3
        4 7 6 5 4

    then the function will return

        [[0, 1, 2, 3],
         [7, 6, 5, 4]]

    but if the data is

        4 0 1 2 3
        3 6 5 4

    then the function will return None.

    Args:
        f: file-like object being read.
        definition: The element object which describes what we are reading.
        big_endian: (bool) whether the document is encoded as big endian.

    Returns:
        If every element has the same size, 2D numpy array corresponding to the
        data. The rows are the different values. Otherwise None.
    """
    property = definition.properties[0]
    endian_str = ">" if big_endian else "<"
    length_format = endian_str + _PLY_TYPES[property.list_size_type].struct_char
    length_struct = struct.Struct(length_format)

    def get_length():
        bytes_data = f.read(length_struct.size)
        if len(bytes_data) != length_struct.size:
            raise ValueError("Not enough data for %s." % definition.name)
        [length] = length_struct.unpack(bytes_data)
        return length

    old_offset = f.tell()

    length = get_length()
    np_type = _PLY_TYPES[definition.properties[0].data_type].np_type
    type_size = _PLY_TYPES[definition.properties[0].data_type].size
    data_size = type_size * length

    output = np.zeros((definition.count, length), dtype=np_type)

    for i in range(definition.count):
        bytes_data = f.read(data_size)
        if len(bytes_data) != data_size:
            raise ValueError("Not enough data for %s" % definition.name)
        output[i] = np.frombuffer(bytes_data, dtype=np_type)
        if i + 1 == definition.count:
            break
        if length != get_length():
            f.seek(old_offset)
            return None
    if (sys.byteorder == "big") != big_endian:
        output = output.byteswap()

    return output


def _read_ply_element_binary(f, definition: _PlyElementType, big_endian: bool) -> list:
    """
    Decode all instances of a single element from a binary .ply file.

    Args:
        f: file-like object being read.
        definition: The element object which describes what we are reading.
        big_endian: (bool) whether the document is encoded as big endian.

    Returns:
        In simple cases where every element has the same size, 2D numpy array
        corresponding to the data. The rows are the different values.
        Otherwise a list of lists/tuples of values, where the outer list is
        each occurrence of the element, and the inner lists have one value per
        property.
    """
    if not definition.count:
        return []

    if definition.is_constant_type_fixed_size():
        return _read_ply_fixed_size_element_binary(f, definition, big_endian)
    if definition.is_fixed_size():
        return _read_ply_element_binary_nolists(f, definition, big_endian)
    if definition.try_constant_list():
        data = _try_read_ply_constant_list_binary(f, definition, big_endian)
        if data is not None:
            return data

    # We failed to read the element as a lump, must process each line manually.
    endian_str = ">" if big_endian else "<"
    property_structs = []
    for property in definition.properties:
        initial_type = property.list_size_type or property.data_type
        property_structs.append(
            struct.Struct(endian_str + _PLY_TYPES[initial_type].struct_char)
        )

    data = []
    for _i in range(definition.count):
        datum = []
        for property, property_struct in zip(definition.properties, property_structs):
            size = property_struct.size
            initial_data = f.read(size)
            if len(initial_data) != size:
                raise ValueError("Not enough data for %s" % definition.name)
            [initial] = property_struct.unpack(initial_data)
            if property.list_size_type is None:
                datum.append(initial)
            else:
                type_size = _PLY_TYPES[property.data_type].size
                needed_bytes = type_size * initial
                list_data = f.read(needed_bytes)
                if len(list_data) != needed_bytes:
                    raise ValueError("Not enough data for %s" % definition.name)
                np_type = _PLY_TYPES[property.data_type].np_type
                list_np = np.frombuffer(list_data, dtype=np_type)
                if (sys.byteorder == "big") != big_endian:
                    list_np = list_np.byteswap()
                datum.append(list_np)
        data.append(datum)
    return data


def _load_ply_raw_stream(f) -> Tuple[_PlyHeader, dict]:
    """
    Implementation for _load_ply_raw which takes a stream.

    Args:
        f:  A binary or text file-like object.

    Returns:
        header: A _PlyHeader object describing the metadata in the ply file.
        elements: A dictionary of element names to values. If an element is regular, in
        the sense of having no lists or being one uniformly-sized list, then the
        value will be a 2D numpy array. If not, it is a list of the relevant
        property values.
    """

    header = _PlyHeader(f)
    elements = {}
    if header.ascii:
        for element in header.elements:
            elements[element.name] = _read_ply_element_ascii(f, element)
    else:
        if isinstance(f, TextIOBase):
            raise ValueError(
                "Cannot safely read a binary ply file using a Text stream."
            )
        big = header.big_endian
        for element in header.elements:
            elements[element.name] = _read_ply_element_binary(f, element, big)
    end = f.read().strip()
    if len(end) != 0:
        raise ValueError("Extra data at end of file: " + str(end[:20]))
    return header, elements


def _load_ply_raw(f, path_manager: PathManager) -> Tuple[_PlyHeader, dict]:
    """
    Load the data from a .ply file.

    Args:
        f:  A binary or text file-like object (with methods read, readline,
            tell and seek), a pathlib path or a string containing a file name.
            If the ply file is binary, a text stream is not supported.
            It is recommended to use a binary stream.
        path_manager: PathManager for loading if f is a str.

    Returns:
        header: A _PlyHeader object describing the metadata in the ply file.
        elements: A dictionary of element names to values. If an element is
                  regular, in the sense of having no lists or being one
                  uniformly-sized list, then the value will be a 2D numpy array.
                  If it has no lists but more than one type, it will be a list of arrays.
                  If not, it is a list of the relevant property values.
    """
    with _open_file(f, path_manager, "rb") as f:
        header, elements = _load_ply_raw_stream(f)
    return header, elements


@dataclass(frozen=True)
class _VertsColumnIndices:
    """
    Contains the relevant layout of the verts section of file being read.
    Members
        point_idxs: List[int] of 3 point columns.
        color_idxs: List[int] of 3 color columns if they are present,
                    otherwise None.
        color_scale: value to scale colors by.
        normal_idxs: List[int] of 3 normals columns if they are present,
                    otherwise None.
    """

    point_idxs: List[int]
    color_idxs: Optional[List[int]]
    color_scale: float
    normal_idxs: Optional[List[int]]


def _get_verts_column_indices(
    vertex_head: _PlyElementType,
) -> _VertsColumnIndices:
    """
    Get the columns of verts, verts_colors, and verts_normals in the vertex
    element of a parsed ply file, together with a color scale factor.
    When the colors are in byte format, they are scaled from 0..255 to [0,1].
    Otherwise they are not scaled.

    For example, if the vertex element looks as follows:

        element vertex 892
        property double x
        property double y
        property double z
        property double nx
        property double ny
        property double nz
        property uchar red
        property uchar green
        property uchar blue

    then the return value will be ([0,1,2], [6,7,8], 1.0/255, [3,4,5])

    Args:
        vertex_head: as returned from load_ply_raw.

    Returns:
        _VertsColumnIndices object
    """
    point_idxs: List[Optional[int]] = [None, None, None]
    color_idxs: List[Optional[int]] = [None, None, None]
    normal_idxs: List[Optional[int]] = [None, None, None]
    for i, prop in enumerate(vertex_head.properties):
        if prop.list_size_type is not None:
            raise ValueError("Invalid vertices in file: did not expect list.")
        for j, letter in enumerate(["x", "y", "z"]):
            if prop.name == letter:
                point_idxs[j] = i
        for j, name in enumerate(["red", "green", "blue"]):
            if prop.name == name:
                color_idxs[j] = i
        for j, name in enumerate(["nx", "ny", "nz"]):
            if prop.name == name:
                normal_idxs[j] = i
    if None in point_idxs:
        raise ValueError("Invalid vertices in file.")
    color_scale = 1.0
    if all(
        idx is not None and _PLY_TYPES[vertex_head.properties[idx].data_type].size == 1
        for idx in color_idxs
    ):
        color_scale = 1.0 / 255
    return _VertsColumnIndices(
        point_idxs=point_idxs,
        color_idxs=None if None in color_idxs else color_idxs,
        color_scale=color_scale,
        normal_idxs=None if None in normal_idxs else normal_idxs,
    )


@dataclass(frozen=True)
class _VertsData:
    """
    Contains the data of the verts section of file being read.
    Members:
        verts: FloatTensor of shape (V, 3).
        verts_colors: None or FloatTensor of shape (V, 3).
        verts_normals: None or FloatTensor of shape (V, 3).
    """

    verts: torch.Tensor
    verts_colors: Optional[torch.Tensor] = None
    verts_normals: Optional[torch.Tensor] = None


def _get_verts(header: _PlyHeader, elements: dict) -> _VertsData:
    """
    Get the vertex locations, colors and normals from a parsed ply file.

    Args:
        header, elements: as returned from load_ply_raw.

    Returns:
        _VertsData object
    """

    vertex = elements.get("vertex", None)
    if vertex is None:
        raise ValueError("The ply file has no vertex element.")
    if not isinstance(vertex, list):
        raise ValueError("Invalid vertices in file.")
    vertex_head = next(head for head in header.elements if head.name == "vertex")

    column_idxs = _get_verts_column_indices(vertex_head)

    # Case of no vertices
    if vertex_head.count == 0:
        verts = torch.zeros((0, 3), dtype=torch.float32)
        if column_idxs.color_idxs is None:
            return _VertsData(verts=verts)
        return _VertsData(
            verts=verts, verts_colors=torch.zeros((0, 3), dtype=torch.float32)
        )

    # Simple case where the only data is the vertices themselves
    if (
        len(vertex) == 1
        and isinstance(vertex[0], np.ndarray)
        and vertex[0].ndim == 2
        and vertex[0].shape[1] == 3
    ):
        return _VertsData(verts=_make_tensor(vertex[0], cols=3, dtype=torch.float32))

    vertex_colors = None
    vertex_normals = None

    if len(vertex) == 1:
        # This is the case where the whole vertex element has one type,
        # so it was read as a single array and we can index straight into it.
        verts = torch.tensor(vertex[0][:, column_idxs.point_idxs], dtype=torch.float32)
        if column_idxs.color_idxs is not None:
            vertex_colors = column_idxs.color_scale * torch.tensor(
                vertex[0][:, column_idxs.color_idxs], dtype=torch.float32
            )
        if column_idxs.normal_idxs is not None:
            vertex_normals = torch.tensor(
                vertex[0][:, column_idxs.normal_idxs], dtype=torch.float32
            )
    else:
        # The vertex element is heterogeneous. It was read as several arrays,
        # part by part, where a part is a set of properties with the same type.
        # For each property (=column in the file), we store in
        # prop_to_partnum_col its partnum (i.e. the index of what part it is
        # in) and its column number (its index within its part).
        prop_to_partnum_col = [
            (partnum, col)
            for partnum, array in enumerate(vertex)
            for col in range(array.shape[1])
        ]
        verts = torch.empty(size=(vertex_head.count, 3), dtype=torch.float32)
        for axis in range(3):
            partnum, col = prop_to_partnum_col[column_idxs.point_idxs[axis]]
            verts.numpy()[:, axis] = vertex[partnum][:, col]
            # Note that in the previous line, we made the assignment
            # as numpy arrays by casting verts. If we took the (more
            # obvious) method of converting the right hand side to
            # torch, then we might have an extra data copy because
            # torch wants contiguity. The code would be like:
            #   if not vertex[partnum].flags["C_CONTIGUOUS"]:
            #      vertex[partnum] = np.ascontiguousarray(vertex[partnum])
            #   verts[:, axis] = torch.tensor((vertex[partnum][:, col]))
        if column_idxs.color_idxs is not None:
            vertex_colors = torch.empty(
                size=(vertex_head.count, 3), dtype=torch.float32
            )
            for color in range(3):
                partnum, col = prop_to_partnum_col[column_idxs.color_idxs[color]]
                vertex_colors.numpy()[:, color] = vertex[partnum][:, col]
            vertex_colors *= column_idxs.color_scale
        if column_idxs.normal_idxs is not None:
            vertex_normals = torch.empty(
                size=(vertex_head.count, 3), dtype=torch.float32
            )
            for axis in range(3):
                partnum, col = prop_to_partnum_col[column_idxs.normal_idxs[axis]]
                vertex_normals.numpy()[:, axis] = vertex[partnum][:, col]

    return _VertsData(
        verts=verts,
        verts_colors=vertex_colors,
        verts_normals=vertex_normals,
    )


@dataclass(frozen=True)
class _PlyData:
    """
    Contains the data from a PLY file which has been read.
    Members:
        header: _PlyHeader of file metadata from the header
        verts: FloatTensor of shape (V, 3).
        faces: None or LongTensor of vertex indices, shape (F, 3).
        verts_colors: None or FloatTensor of shape (V, 3).
        verts_normals: None or FloatTensor of shape (V, 3).
    """

    header: _PlyHeader
    verts: torch.Tensor
    faces: Optional[torch.Tensor]
    verts_colors: Optional[torch.Tensor]
    verts_normals: Optional[torch.Tensor]


def _load_ply(f, *, path_manager: PathManager) -> _PlyData:
    """
    Load the data from a .ply file.

    Args:
        f:  A binary or text file-like object (with methods read, readline,
            tell and seek), a pathlib path or a string containing a file name.
            If the ply file is in the binary ply format rather than the text
            ply format, then a text stream is not supported.
            It is easiest to use a binary stream in all cases.
        path_manager: PathManager for loading if f is a str.

    Returns:
        _PlyData object
    """
    header, elements = _load_ply_raw(f, path_manager=path_manager)

    verts_data = _get_verts(header, elements)

    face = elements.get("face", None)
    if face is not None:
        face_head = next(head for head in header.elements if head.name == "face")
        if (
            len(face_head.properties) != 1
            or face_head.properties[0].list_size_type is None
        ):
            raise ValueError("Unexpected form of faces data.")
        # face_head.properties[0].name is usually "vertex_index" or "vertex_indices"
        # but we don't need to enforce this.

    if face is None:
        faces = None
    elif not len(face):
        # pyre is happier when this condition is not joined to the
        # previous one with `or`.
        faces = None
    elif isinstance(face, np.ndarray) and face.ndim == 2:  # Homogeneous elements
        if face.shape[1] < 3:
            raise ValueError("Faces must have at least 3 vertices.")
        face_arrays = [face[:, [0, i + 1, i + 2]] for i in range(face.shape[1] - 2)]
        faces = torch.LongTensor(np.vstack(face_arrays).astype(np.int64))
    else:
        face_list = []
        for (face_item,) in face:
            if face_item.ndim != 1:
                raise ValueError("Bad face data.")
            if face_item.shape[0] < 3:
                raise ValueError("Faces must have at least 3 vertices.")
            for i in range(face_item.shape[0] - 2):
                face_list.append([face_item[0], face_item[i + 1], face_item[i + 2]])
        faces = torch.tensor(face_list, dtype=torch.int64)

    if faces is not None:
        _check_faces_indices(faces, max_index=verts_data.verts.shape[0])

    return _PlyData(**asdict(verts_data), faces=faces, header=header)


def load_ply(
    f, *, path_manager: Optional[PathManager] = None
) -> Tuple[torch.Tensor, torch.Tensor]:
    """
    Load the verts and faces from a .ply file.
    Note that the preferred way to load data from such a file
    is to use the IO.load_mesh and IO.load_pointcloud functions,
    which can read more of the data.

    Example .ply file format:

    ply
    format ascii 1.0           { ascii/binary, format version number }
    comment made by Greg Turk  { comments keyword specified, like all lines }
    comment this file is a cube
    element vertex 8           { define "vertex" element, 8 of them in file }
    property float x           { vertex contains float "x" coordinate }
    property float y           { y coordinate is also a vertex property }
    property float z           { z coordinate, too }
    element face 6             { there are 6 "face" elements in the file }
    property list uchar int vertex_index { "vertex_indices" is a list of ints }
    end_header                 { delimits the end of the header }
    0 0 0                      { start of vertex list }
    0 0 1
    0 1 1
    0 1 0
    1 0 0
    1 0 1
    1 1 1
    1 1 0
    4 0 1 2 3                  { start of face list }
    4 7 6 5 4
    4 0 4 5 1
    4 1 5 6 2
    4 2 6 7 3
    4 3 7 4 0

    Args:
        f:  A binary or text file-like object (with methods read, readline,
            tell and seek), a pathlib path or a string containing a file name.
            If the ply file is in the binary ply format rather than the text
            ply format, then a text stream is not supported.
            It is easiest to use a binary stream in all cases.
        path_manager: PathManager for loading if f is a str.

    Returns:
        verts: FloatTensor of shape (V, 3).
        faces: LongTensor of vertex indices, shape (F, 3).
    """

    if path_manager is None:
        path_manager = PathManager()
    data = _load_ply(f, path_manager=path_manager)
    faces = data.faces
    if faces is None:
        faces = torch.zeros(0, 3, dtype=torch.int64)

    return data.verts, faces


def _write_ply_header(
    f,
    *,
    verts: torch.Tensor,
    faces: Optional[torch.LongTensor],
    verts_normals: Optional[torch.Tensor],
    verts_colors: Optional[torch.Tensor],
    ascii: bool,
    colors_as_uint8: bool,
) -> None:
    """
    Internal implementation for writing header when saving to a .ply file.

    Args:
        f: File object to which the 3D data should be written.
        verts: FloatTensor of shape (V, 3) giving vertex coordinates.
        faces: LongTensor of shape (F, 3) giving faces.
        verts_normals: FloatTensor of shape (V, 3) giving vertex normals.
        verts_colors: FloatTensor of shape (V, 3) giving vertex colors.
        ascii: (bool) whether to use the ascii ply format.
        colors_as_uint8: Whether to save colors as numbers in the range
                    [0, 255] instead of float32.
    """
    assert not len(verts) or (verts.dim() == 2 and verts.size(1) == 3)
    assert faces is None or not len(faces) or (faces.dim() == 2 and faces.size(1) == 3)
    assert verts_normals is None or (
        verts_normals.dim() == 2 and verts_normals.size(1) == 3
    )
    assert verts_colors is None or (
        verts_colors.dim() == 2 and verts_colors.size(1) == 3
    )

    if ascii:
        f.write(b"ply\nformat ascii 1.0\n")
    elif sys.byteorder == "big":
        f.write(b"ply\nformat binary_big_endian 1.0\n")
    else:
        f.write(b"ply\nformat binary_little_endian 1.0\n")
    f.write(f"element vertex {verts.shape[0]}\n".encode("ascii"))
    f.write(b"property float x\n")
    f.write(b"property float y\n")
    f.write(b"property float z\n")
    if verts_normals is not None:
        f.write(b"property float nx\n")
        f.write(b"property float ny\n")
        f.write(b"property float nz\n")
    if verts_colors is not None:
        color_ply_type = b"uchar" if colors_as_uint8 else b"float"
        for color in (b"red", b"green", b"blue"):
            f.write(b"property " + color_ply_type + b" " + color + b"\n")
    if len(verts) and faces is not None:
        f.write(f"element face {faces.shape[0]}\n".encode("ascii"))
        f.write(b"property list uchar int vertex_index\n")
    f.write(b"end_header\n")


def _save_ply(
    f,
    *,
    verts: torch.Tensor,
    faces: Optional[torch.LongTensor],
    verts_normals: Optional[torch.Tensor],
    verts_colors: Optional[torch.Tensor],
    ascii: bool,
    decimal_places: Optional[int] = None,
    colors_as_uint8: bool,
) -> None:
    """
    Internal implementation for saving 3D data to a .ply file.

    Args:
        f: File object to which the 3D data should be written.
        verts: FloatTensor of shape (V, 3) giving vertex coordinates.
        faces: LongTensor of shape (F, 3) giving faces.
        verts_normals: FloatTensor of shape (V, 3) giving vertex normals.
        verts_colors: FloatTensor of shape (V, 3) giving vertex colors.
        ascii: (bool) whether to use the ascii ply format.
        decimal_places: Number of decimal places for saving if ascii=True.
        colors_as_uint8: Whether to save colors as numbers in the range
                    [0, 255] instead of float32.
    """
    _write_ply_header(
        f,
        verts=verts,
        faces=faces,
        verts_normals=verts_normals,
        verts_colors=verts_colors,
        ascii=ascii,
        colors_as_uint8=colors_as_uint8,
    )

    if not (len(verts)):
        warnings.warn("Empty 'verts' provided")
        return

    color_np_type = np.ubyte if colors_as_uint8 else np.float32
    verts_dtype = [("verts", np.float32, 3)]
    if verts_normals is not None:
        verts_dtype.append(("normals", np.float32, 3))
    if verts_colors is not None:
        verts_dtype.append(("colors", color_np_type, 3))

    vert_data = np.zeros(verts.shape[0], dtype=verts_dtype)
    vert_data["verts"] = verts.detach().cpu().numpy()
    if verts_normals is not None:
        vert_data["normals"] = verts_normals.detach().cpu().numpy()
    if verts_colors is not None:
        color_data = verts_colors.detach().cpu().numpy()
        if colors_as_uint8:
            vert_data["colors"] = np.rint(color_data * 255)
        else:
            vert_data["colors"] = color_data

    if ascii:
        if decimal_places is None:
            float_str = b"%f"
        else:
            float_str = b"%" + b".%df" % decimal_places
        float_group_str = (float_str + b" ") * 3
        formats = [float_group_str]
        if verts_normals is not None:
            formats.append(float_group_str)
        if verts_colors is not None:
            formats.append(b"%d %d %d " if colors_as_uint8 else float_group_str)
        formats[-1] = formats[-1][:-1] + b"\n"
        for line_data in vert_data:
            for data, format in zip(line_data, formats):
                f.write(format % tuple(data))
    else:
        if isinstance(f, BytesIO):
            # tofile only works with real files, but is faster than this.
            f.write(vert_data.tobytes())
        else:
            vert_data.tofile(f)

    if faces is not None:
        faces_array = faces.detach().cpu().numpy()

        _check_faces_indices(faces, max_index=verts.shape[0])

        if len(faces_array):
            if ascii:
                np.savetxt(f, faces_array, "3 %d %d %d")
            else:
                faces_recs = np.zeros(
                    len(faces_array),
                    dtype=[("count", np.uint8), ("vertex_indices", np.uint32, 3)],
                )
                faces_recs["count"] = 3
                faces_recs["vertex_indices"] = faces_array
                faces_uints = faces_recs.view(np.uint8)

                if isinstance(f, BytesIO):
                    f.write(faces_uints.tobytes())
                else:
                    faces_uints.tofile(f)


def save_ply(
    f,
    verts: torch.Tensor,
    faces: Optional[torch.LongTensor] = None,
    verts_normals: Optional[torch.Tensor] = None,
    ascii: bool = False,
    decimal_places: Optional[int] = None,
    path_manager: Optional[PathManager] = None,
) -> None:
    """
    Save a mesh to a .ply file.

    Args:
        f: File (or path) to which the mesh should be written.
        verts: FloatTensor of shape (V, 3) giving vertex coordinates.
        faces: LongTensor of shape (F, 3) giving faces.
        verts_normals: FloatTensor of shape (V, 3) giving vertex normals.
        ascii: (bool) whether to use the ascii ply format.
        decimal_places: Number of decimal places for saving if ascii=True.
        path_manager: PathManager for interpreting f if it is a str.
    """

    if len(verts) and not (verts.dim() == 2 and verts.size(1) == 3):
        message = "Argument 'verts' should either be empty or of shape (num_verts, 3)."
        raise ValueError(message)

    if (
        faces is not None
        and len(faces)
        and not (faces.dim() == 2 and faces.size(1) == 3)
    ):
        message = "Argument 'faces' should either be empty or of shape (num_faces, 3)."
        raise ValueError(message)

    if (
        verts_normals is not None
        and len(verts_normals)
        and not (
            verts_normals.dim() == 2
            and verts_normals.size(1) == 3
            and verts_normals.size(0) == verts.size(0)
        )
    ):
        message = "Argument 'verts_normals' should either be empty or of shape (num_verts, 3)."
        raise ValueError(message)

    if path_manager is None:
        path_manager = PathManager()
    with _open_file(f, path_manager, "wb") as f:
        _save_ply(
            f,
            verts=verts,
            faces=faces,
            verts_normals=verts_normals,
            verts_colors=None,
            ascii=ascii,
            decimal_places=decimal_places,
            colors_as_uint8=False,
        )


class MeshPlyFormat(MeshFormatInterpreter):
    def __init__(self) -> None:
        self.known_suffixes = (".ply",)

    def read(
        self,
        path: PathOrStr,
        include_textures: bool,
        device,
        path_manager: PathManager,
        **kwargs,
    ) -> Optional[Meshes]:
        if not endswith(path, self.known_suffixes):
            return None

        data = _load_ply(f=path, path_manager=path_manager)
        faces = data.faces
        if faces is None:
            faces = torch.zeros(0, 3, dtype=torch.int64)

        texture = None
        if include_textures and data.verts_colors is not None:
            texture = TexturesVertex([data.verts_colors.to(device)])

        verts_normals = None
        if data.verts_normals is not None:
            verts_normals = [data.verts_normals.to(device)]
        mesh = Meshes(
            verts=[data.verts.to(device)],
            faces=[faces.to(device)],
            textures=texture,
            verts_normals=verts_normals,
        )
        return mesh

    def save(
        self,
        data: Meshes,
        path: PathOrStr,
        path_manager: PathManager,
        binary: Optional[bool],
        decimal_places: Optional[int] = None,
        colors_as_uint8: bool = False,
        **kwargs,
    ) -> bool:
        """
        Extra optional args:
            colors_as_uint8: (bool) Whether to save colors as numbers in the
                        range [0, 255] instead of float32.
        """
        if not endswith(path, self.known_suffixes):
            return False

        verts = data.verts_list()[0]
        faces = data.faces_list()[0]

        if data.has_verts_normals():
            verts_normals = data.verts_normals_list()[0]
        else:
            verts_normals = None

        if isinstance(data.textures, TexturesVertex):
            mesh_verts_colors = data.textures.verts_features_list()[0]
            n_colors = mesh_verts_colors.shape[1]
            if n_colors == 3:
                verts_colors = mesh_verts_colors
            else:
                warnings.warn(
                    f"Texture will not be saved as it has {n_colors} colors, not 3."
                )
                verts_colors = None
        else:
            verts_colors = None

        with _open_file(path, path_manager, "wb") as f:
            _save_ply(
                f=f,
                verts=verts,
                faces=faces,
                verts_colors=verts_colors,
                verts_normals=verts_normals,
                ascii=binary is False,
                decimal_places=decimal_places,
                colors_as_uint8=colors_as_uint8,
            )
        return True


class PointcloudPlyFormat(PointcloudFormatInterpreter):
    def __init__(self) -> None:
        self.known_suffixes = (".ply",)

    def read(
        self,
        path: PathOrStr,
        device,
        path_manager: PathManager,
        **kwargs,
    ) -> Optional[Pointclouds]:
        if not endswith(path, self.known_suffixes):
            return None

        data = _load_ply(f=path, path_manager=path_manager)
        features = None
        if data.verts_colors is not None:
            features = [data.verts_colors.to(device)]
        normals = None
        if data.verts_normals is not None:
            normals = [data.verts_normals.to(device)]

        pointcloud = Pointclouds(
            points=[data.verts.to(device)], features=features, normals=normals
        )
        return pointcloud

    def save(
        self,
        data: Pointclouds,
        path: PathOrStr,
        path_manager: PathManager,
        binary: Optional[bool],
        decimal_places: Optional[int] = None,
        colors_as_uint8: bool = False,
        **kwargs,
    ) -> bool:
        """
        Extra optional args:
            colors_as_uint8: (bool) Whether to save colors as numbers in the
                        range [0, 255] instead of float32.
        """
        if not endswith(path, self.known_suffixes):
            return False

        points = data.points_list()[0]
        features = data.features_packed()
        normals = data.normals_packed()

        with _open_file(path, path_manager, "wb") as f:
            _save_ply(
                f=f,
                verts=points,
                verts_colors=features,
                verts_normals=normals,
                faces=None,
                ascii=binary is False,
                decimal_places=decimal_places,
                colors_as_uint8=colors_as_uint8,
            )
        return True
