# Source code for pymatgen.io.xyz

    # coding: utf-8
    # Copyright (c) Pymatgen Development Team.
    # Distributed under the terms of the MIT License.

    """
    Module implementing an XYZ file object class.
    """

    import re

    from pymatgen.core.structure import Molecule
    from monty.io import zopen
    from io import StringIO
    import pandas as pd

    class XYZ:
        """
        Basic class for importing and exporting Molecules or Structures in XYZ
        format.

        .. note::
            Exporting periodic structures in the XYZ format will lose information
            about the periodicity. Essentially, only cartesian coordinates are
            written in this format and no information is retained about the
            lattice.
        """
        def __init__(self, mol: Molecule, coord_precision: int = 6):
            """
            Args:
                mol: Input molecule or list of molecules
                coord_precision: Precision to be used for coordinates.
            """
            if isinstance(mol, Molecule) or not isinstance(mol, list):
                self._mols = [mol]
            else:
                self._mols = mol
            self.precision = coord_precision

        @property
        def molecule(self) -> Molecule:
            """
            Returns molecule associated with this XYZ. In case multiple frame
            XYZ, returns the last frame.
            """
            return self._mols[-1]

        @property
        def all_molecules(self):
            """
            Returns all the frames of molecule associated with this XYZ.
            """
            return self._mols

        @staticmethod
        def _from_frame_string(contents):
            """
            Convert a single frame XYZ string to a molecule
            """
            lines = contents.split("\n")
            num_sites = int(lines[0])
            coords = []
            sp = []
            coord_patt = re.compile(
                r"(\w+)\s+([0-9\-\+\.*^eEdD]+)\s+([0-9\-\+\.*^eEdD]+)\s+"
                r"([0-9\-\+\.*^eEdD]+)")
            for i in range(2, 2 + num_sites):
                m = coord_patt.search(lines[i])
                if m:
                    sp.append(m.group(1))  # this is 1-indexed
                    # this is 0-indexed
                    # in case of 0.0D+00 or 0.00d+01 old double precision writing
                    # replace d or D by e for ten power exponent,
                    # and some files use *^ convention in place of e
                    xyz = [val.lower().replace("d", "e").replace('*^', 'e') for val
                           in m.groups()[1:4]]
                    coords.append([float(val) for val in xyz])
            return Molecule(sp, coords)

        @staticmethod
        def from_string(contents):
            """
            Creates XYZ object from a string.

            Args:
                contents: String representing an XYZ file.

            Returns:
                XYZ object
            """
            if contents[-1] != "\n":
                contents += "\n"
            white_space = r"[ \t\r\f\v]"
            natoms_line = white_space + r"*\d+" + white_space + r"*\n"
            comment_line = r"[^\n]*\n"
            coord_lines = r"(\s*\w+\s+[0-9\-\+\.*^eEdD]+\s+[0-9\-\+\.*^eEdD]+" \
                          r"\s+[0-9\-\+\.*^eEdD]+.*\n)+"
            frame_pattern_text = natoms_line + comment_line + coord_lines
            pat = re.compile(frame_pattern_text, re.MULTILINE)
            mols = []
            for xyz_match in pat.finditer(contents):
                xyz_text = xyz_match.group(0)
                mols.append(XYZ._from_frame_string(xyz_text))
            return XYZ(mols)

        @staticmethod
        def from_file(filename):
            """
            Creates XYZ object from a file.

            Args:
                filename: XYZ filename

            Returns:
                XYZ object
            """
            with zopen(filename) as f:
                return XYZ.from_string(f.read())

        def as_dataframe(self):
            """
            Generates a coordinates data frame with columns: atom, x, y, and z
            In case of multiple frame XYZ, returns the last frame.

            Returns:
                pandas.DataFrame

            """
            lines = str(self)

            sio = StringIO(lines)
            df = pd.read_csv(sio,
                             header=None,
                             skiprows=[0, 1],
                             comment="#",
                             delim_whitespace=True,
                             names=['atom', 'x', 'y', 'z'])
            df.index += 1
            return df

        def _frame_str(self, frame_mol):
            output = [str(len(frame_mol)), frame_mol.composition.formula]
            fmtstr = "{{}} {{:.{0}f}} {{:.{0}f}} {{:.{0}f}}".format(self.precision)
            for site in frame_mol:
                output.append(fmtstr.format(site.specie, site.x, site.y, site.z))
            return "\n".join(output)

        def __str__(self):
            return "\n".join([self._frame_str(mol) for mol in self._mols])

        def write_file(self, filename):
            """
            Writes XYZ to file.

            Args:
                filename: File name of output file.
            """
            with zopen(filename, "wt") as f:
                f.write(self.__str__())